Two techniques for digital filter design

Digital controllers, one using a special-purpose computer and the other using a combination of digital and analog techniques, are designed around /1/ computers that simulate the transfer function and interface with the system, and /2/ analog and digital circuits, converters, amplifiers, constant multipliers, and delay lines that form a digital filter

A swollen phase observed between the liquid-crystalline phase and the interdigitated phase induced by pressure and/or adding ethanol in DPPC aqueous solution

A swollen phase, in which the mean repeat distance of lipid bilayers is larger than the other phases, is found between the liquid-crystalline phase and the interdigitated gel phase in DPPC aqueous solution. Temperature, pressure and ethanol concentration dependences of the structure were investigated by small-angle neutron scattering, and a bending rigidity of lipid bilayers was by neutron spin echo. The nature of the swollen phase is similar to the anomalous swelling reported previously. However, the temperature dependence of the mean repeat distance and the bending rigidity of lipid bilayers are different. This phase could be a precursor to the interdigitated gel phase induced by pressure and/or adding ethanol.Comment: 7 pages, 6 figure

Modeling Cluster Production at the AGS

Deuteron coalescence, during relativistic nucleus-nucleus collisions, is carried out in a model incorporating a minimal quantal treatment of the formation of the cluster from its individual nucleons by evaluating the overlap of intial cascading nucleon wave packets with the final deuteron wave function. In one approach the nucleon and deuteron center of mass wave packet sizes are estimated dynamically for each coalescing pair using its past light-cone history in the underlying cascade, a procedure which yields a parameter free determination of the cluster yield. A modified version employing a global estimate of the deuteron formation probability, is identical to a general implementation of the Wigner function formalism but can differ from the most frequent realisation of the latter. Comparison is made both with the extensive existing E802 data for Si+Au at 14.6 GeV/c and with the Wigner formalism. A globally consistent picture of the Si+Au measurements is achieved. In light of the deuteron's evident fragility, information obtained from this analysis may be useful in establishing freeze-out volumes and help in heralding the presence of high-density phenomena in a baryon-rich environment.Comment: 31 pages REVTeX, 19 figures (4 oversized included as JPEG). For full postscript figures (LARGE): contact [email protected]

Coarse-Graining and Self-Dissimilarity of Complex Networks

Can complex engineered and biological networks be coarse-grained into smaller and more understandable versions in which each node represents an entire pattern in the original network? To address this, we define coarse-graining units (CGU) as connectivity patterns which can serve as the nodes of a coarse-grained network, and present algorithms to detect them. We use this approach to systematically reverse-engineer electronic circuits, forming understandable high-level maps from incomprehensible transistor wiring: first, a coarse-grained version in which each node is a gate made of several transistors is established. Then, the coarse-grained network is itself coarse-grained, resulting in a high-level blueprint in which each node is a circuit-module made of multiple gates. We apply our approach also to a mammalian protein-signaling network, to find a simplified coarse-grained network with three main signaling channels that correspond to cross-interacting MAP-kinase cascades. We find that both biological and electronic networks are 'self-dissimilar', with different network motifs found at each level. The present approach can be used to simplify a wide variety of directed and nondirected, natural and designed networks.Comment: 11 pages, 11 figure

A theorem on the absence of phase transitions in one-dimensional growth models with onsite periodic potentials

We rigorously prove that a wide class of one-dimensional growth models with onsite periodic potential, such as the discrete sine-Gordon model, have no phase transition at any temperature $T>0$. The proof relies on the spectral analysis of the transfer operator associated to the models. We show that this operator is Hilbert-Schmidt and that its maximum eigenvalue is an analytic function of temperature.Comment: 6 pages, no figures, submitted to J Phys A: Math Ge

Elastic energy of polyhedral bilayer vesicles

In recent experiments [M. Dubois, B. Dem\'e, T. Gulik-Krzywicki, J.-C. Dedieu, C. Vautrin, S. D\'esert, E. Perez, and T. Zemb, Nature (London) Vol. 411, 672 (2001)] the spontaneous formation of hollow bilayer vesicles with polyhedral symmetry has been observed. On the basis of the experimental phenomenology it was suggested [M. Dubois, V. Lizunov, A. Meister, T. Gulik-Krzywicki, J. M. Verbavatz, E. Perez, J. Zimmerberg, and T. Zemb, Proc. Natl. Acad. Sci. U.S.A. Vol. 101, 15082 (2004)] that the mechanism for the formation of bilayer polyhedra is minimization of elastic bending energy. Motivated by these experiments, we study the elastic bending energy of polyhedral bilayer vesicles. In agreement with experiments, and provided that excess amphiphiles exhibiting spontaneous curvature are present in sufficient quantity, we find that polyhedral bilayer vesicles can indeed be energetically favorable compared to spherical bilayer vesicles. Consistent with experimental observations we also find that the bending energy associated with the vertices of bilayer polyhedra can be locally reduced through the formation of pores. However, the stabilization of polyhedral bilayer vesicles over spherical bilayer vesicles relies crucially on molecular segregation of excess amphiphiles along the ridges rather than the vertices of bilayer polyhedra. Furthermore, our analysis implies that, contrary to what has been suggested on the basis of experiments, the icosahedron does not minimize elastic bending energy among arbitrary polyhedral shapes and sizes. Instead, we find that, for large polyhedron sizes, the snub dodecahedron and the snub cube both have lower total bending energies than the icosahedron

Continuous melting of compact polymers

The competition between chain entropy and bending rigidity in compact polymers can be addressed within a lattice model introduced by P.J. Flory in 1956. It exhibits a transition between an entropy dominated disordered phase and an energetically favored crystalline phase. The nature of this order-disorder transition has been debated ever since the introduction of the model. Here we present exact results for the Flory model in two dimensions relevant for polymers on surfaces, such as DNA adsorbed on a lipid bilayer. We predict a continuous melting transition, and compute exact values of critical exponents at the transition point.Comment: 5 pages, 1 figur

Author Correction: LKB1 loss links serine metabolism to DNA methylation and tumorigenesis

Erratum for: LKB1 loss links serine metabolism to DNA methylation and tumorigenesis. [Nature. 2016