Apparent digestibility in meat-type guinea pigs as determined by total collection or by internal marker

Six adult male meat-type guinea pigs were subjected to three subsequent digestibility trials with 100% alfalfa, 50% alfalfa and 50% sugar cane and 50% alfalfa and 50% concentrate. For each animal in each period, feed intakes were recorded and all faeces were collected and stored at -20 degrees C until analysis. Feeds and faeces were analysed for dry matter, crude ash, crude protein, ether-extract, crude fibre and acid-insoluble ash. Coefficients of apparent digestibility were calculated according to both the total collection method and the marker method with acid-insoluble ash as internal marker. The present study suggests that acid-insoluble ash is not valid as an internal marker when looking at differences between individuals, but might be useful to demonstrate differences between diets, albeit with lack of accuracy for estimating the absolute digestibility coefficients obtained through the total collection method. Sugar cane was slightly less digestible than alfalfa in meat-type guinea-pigs

Bifurcation analysis of a normal form for excitable media: Are stable dynamical alternans on a ring possible?

We present a bifurcation analysis of a normal form for travelling waves in one-dimensional excitable media. The normal form which has been recently proposed on phenomenological grounds is given in form of a differential delay equation. The normal form exhibits a symmetry preserving Hopf bifurcation which may coalesce with a saddle-node in a Bogdanov-Takens point, and a symmetry breaking spatially inhomogeneous pitchfork bifurcation. We study here the Hopf bifurcation for the propagation of a single pulse in a ring by means of a center manifold reduction, and for a wave train by means of a multiscale analysis leading to a real Ginzburg-Landau equation as the corresponding amplitude equation. Both, the center manifold reduction and the multiscale analysis show that the Hopf bifurcation is always subcritical independent of the parameters. This may have links to cardiac alternans which have so far been believed to be stable oscillations emanating from a supercritical bifurcation. We discuss the implications for cardiac alternans and revisit the instability in some excitable media where the oscillations had been believed to be stable. In particular, we show that our condition for the onset of the Hopf bifurcation coincides with the well known restitution condition for cardiac alternans.Comment: to be published in Chao

Sufficient Conditions for Fast Switching Synchronization in Time Varying Network Topologies

In previous work, empirical evidence indicated that a time-varying network could propagate sufficient information to allow synchronization of the sometimes coupled oscillators, despite an instantaneously disconnected topology. We prove here that if the network of oscillators synchronizes for the static time-average of the topology, then the network will synchronize with the time-varying topology if the time-average is achieved sufficiently fast. Fast switching, fast on the time-scale of the coupled oscillators, overcomes the descychnronizing decoherence suggested by disconnected instantaneous networks. This result agrees in spirit with that of where empirical evidence suggested that a moving averaged graph Laplacian could be used in the master-stability function analysis. A new fast switching stability criterion here-in gives sufficiency of a fast-switching network leading to synchronization. Although this sufficient condition appears to be very conservative, it provides new insights about the requirements for synchronization when the network topology is time-varying. In particular, it can be shown that networks of oscillators can synchronize even if at every point in time the frozen-time network topology is insufficiently connected to achieve synchronization.Comment: Submitted to SIAD

Unifying theory of quantum state estimation using past and future information

Quantum state estimation for continuously monitored dynamical systems involves assigning a quantum state to an individual system at some time, conditioned on the results of continuous observations. The quality of the estimation depends on how much observed information is used and on how optimality is defined for the estimate. In this work, we consider problems of quantum state estimation where some of the measurement records are not available, but where the available records come from both before (past) and after (future) the estimation time, enabling better estimates than is possible using the past information alone. Past-future information for quantum systems has been used in various ways in the literature, in particular, the quantum state smoothing, the most-likely path, and the two-state vector and related formalisms. To unify these seemingly unrelated approaches, we propose a framework for partially-observed quantum system with continuous monitoring, wherein the first two existing formalisms can be accommodated, with some generalization. The unifying framework is based on state estimation with expected cost minimization, where the cost can be defined either in the space of the unknown record or in the space of the unknown true state. Moreover, we connect all three existing approaches conceptually by defining five new cost functions, and thus new types of estimators, which bridge the gaps between them. We illustrate the applicability of our method by calculating all seven estimators we consider for the example of a driven two-level system dissipatively coupled to bosonic baths. Our theory also allows connections to classical state estimation, which create further conceptual links between our quantum state estimators.Comment: 48 pages, 9 figure

Free expansion of impenetrable bosons on one-dimensional optical lattices

We review recent exact results for the free expansion of impenetrable bosons on one-dimensional lattices, after switching off a confining potential. When the system is initially in a superfluid state, far from the regime in which the Mott-insulator appears in the middle of the trap, the momentum distribution of the expanding bosons rapidly approaches the momentum distribution of noninteracting fermions. Remarkably, no loss in coherence is observed in the system as reflected by a large occupation of the lowest eigenstate of the one-particle density matrix. In the opposite limit, when the initial system is a pure Mott insulator with one particle per lattice site, the expansion leads to the emergence of quasicondensates at finite momentum. In this case, one-particle correlations like the ones shown to be universal in the equilibrium case develop in the system. We show that the out-of-equilibrium behavior of the Shannon information entropy in momentum space, and its contrast with the one of noninteracting fermions, allows to differentiate the two different regimes of interest. It also helps in understanding the crossover between them.Comment: 21 pages, 14 figures, invited brief revie

Transformation elastodynamics and active exterior acoustic cloaking

This chapter consists of three parts. In the first part we recall the elastodynamic equations under coordinate transformations. The idea is to use coordinate transformations to manipulate waves propagating in an elastic material. Then we study the effect of transformations on a mass-spring network model. The transformed networks can be realized with "torque springs", which are introduced here and are springs with a force proportional to the displacement in a direction other than the direction of the spring terminals. Possible homogenizations of the transformed networks are presented, with potential applications to cloaking. In the second and third parts we present cloaking methods that are based on cancelling an incident field using active devices which are exterior to the cloaked region and that do not generate significant fields far away from the devices. In the second part, the exterior cloaking problem for the Laplace equation is reformulated as the problem of polynomial approximation of analytic functions. An explicit solution is given that allows to cloak larger objects at a fixed distance from the cloaking device, compared to previous explicit solutions. In the third part we consider the active exterior cloaking problem for the Helmholtz equation in 3D. Our method uses the Green's formula and an addition theorem for spherical outgoing waves to design devices that mimic the effect of the single and double layer potentials in Green's formula.Comment: Submitted as a chapter for the volume "Acoustic metamaterials: Negative refraction, imaging, lensing and cloaking", Craster and Guenneau ed., Springe

Properties of recent IBAD-MOCVD Coated Conductors relevant to their high field, low temperature magnet use

BaZrO3 (BZO) nanorods are now incorporated into production IBAD-MOCVD coated conductors. Here we compare several examples of both BZO-free and BZO-containing coated conductors using critical current (Ic) characterizations at 4.2 K over their full angular range up to fields of 31 T. We find that BZO nanorods do not produce any c-axis distortion of the critical current density Jc(theta) curve at 4.2 K at any field, but also that pinning is nevertheless strongly enhanced compared to the non-BZO conductors. We also find that the tendency of the ab-plane Jc(theta) peak to become cusp-like is moderated by BZO and we define a new figure of merit that may be helpful for magnet design - the OADI (Off-Axis Double Ic), which clearly shows that BZO broadens the ab-plane peak and thus raises Jc 5-30{\deg} away from the tape plane, where the most critical approach to Ic occurs in many coil designs. We describe some experimental procedures that may make critical current Ic tests of these very high current tapes more tractable at 4.2 K, where Ic exceeds 1000 A even for 4 mm wide tape with only 1 micron thickness of superconductor. A positive conclusion is that BZO is very beneficial for the Jc characteristics at 4.2 K, just as it is at higher temperatures, where the correlated c-axis pinning effects of the nanorods are much more obvious

Supermassive black holes in the EAGLE Universe. Revealing the observables of their growth

We investigate the evolution of supermassive black holes in the ‘Evolution and Assembly of GaLaxies and their Environments’ (EAGLE) cosmological hydrodynamic simulations. The largest of the EAGLE volumes covers a (100 cMpc)3 and includes state-of-the-art physical models for star formation and black hole growth that depend only on local gas properties. We focus on the black hole mass function, Eddington ratio distribution and the implied duty cycle of nuclear activity. The simulation is broadly consistent with observational constraints on these quantities. In order to make a more direct comparison with observational data, we calculate the soft and hard X-ray luminosity functions of the active galactic nuclei (AGN). Between redshifts 0 and 1, the simulation is in agreement with data. At higher redshifts, the simulation tends to underpredict the luminosities of the brightest observed AGN. This may be due to the limited volume of the simulation, or a fundamental deficiency of the underlying model. It seems unlikely that additional unresolved variability can account for this difference. The simulation shows a similar ‘downsizing’ of the AGN population as seen in observational surveys