Behavioral responses of humpback whales (Megaptera novaeangliae) to full-scale ATOC signals

Loud (195 dB re 1 microPa at 1 m) 75-Hz signals were broadcast with an ATOC projector to measure ocean temperature. Respiratory and movement behaviors of humpback whales off North Kauai, Hawaii, were examined for potential changes in response to these transmissions and to vessels. Few vessel effects were observed, but there were fewer vessels operating during this study than in previous years. No overt responses to ATOC were observed for received levels of 98-109 dB re 1 microPa. An analysis of covariance, using the no-sound behavioral rate as a covariate to control for interpod variation, found that the distance and time between successive surfacings of humpbacks increased slightly with an increase in estimated received ATOC sound level. These responses are very similar to those observed in response to scaled-amplitude playbacks of ATOC signals [Frankel and Clark, Can. J. Zool. 76, 521-535 (1998)]. These similar results were obtained with different sound projectors, in different years and locations, and at different ranges creating a different sound field. The repeatability of the findings for these two different studies indicates that these effects, while small, are robust. This suggests that at least for the ATOC signal, the received sound level is a good predictor of response.     

A free boundary problem modeling thermal instabilities: Stability and bifurcation

In this paper, we analyze a simple free boundary model associated with solid combustion and some phase transition processes. There is strong evidence that this one-phase model captures all major features of dynamical behavior of more realistic (and complicated) combustion and phase transition models. The principal results concern the dynamical behavior of the model as a bifurcation parameter (which is related to the activation energy in the case of combustion) varies. We prove that the basic uniform front propagation is asymptotically stable against perturbations for the bifurcation parameter above the instability threshold and that a Hopf bifurcation takes place at the threshold value. Results of numerical simulations are presented which confirm that both supercritical and subcritical Hofp bifurcation may occur for physically reasonable nonlinear kinetic functions.     

The effect of residual stresses on hardness measurements

The RockwellC hardness,RC, was measured as a function of position on steel rings with different residual-stress profiles through the thickness. An experimental correlation between residual stress andRC was obtained. A relationship between the average pressurep of a spherical indenter, the yield strengthS _y and the residual stress of the material was conceived and used in fitting the experimental data. In order to model the effects of residual stresses on the measured hardness, the von Mises-Hencky (power) yield criterion was utilized, together with an adaptation for residual stresses of the expression for the stress state under a spherical indenter, given in Shaw, Hoshi and Henry. A parameter α was introduced in our calculations to account for the effect of the nonperpendicularity of the residual stresses to the pressurep of the spherical indenter. The proposed model in large measure fits experimental hardness versus residual stress data, and results are consistent with different samples. This model can be used as a basis for the measurement of residual stresses in steel or other materials.     

Asymptotics for some semilinear hyperbolic equations with non-autonomous damping

Let V and H be Hilbert spaces such that $V?H?V^{\prime }$ with dense and continuous injections. Consider a linear continuous operator $A:V\to V^{\prime }$ which is assumed to be symmetric, monotone and semi-coercive. Given a function $f:V\to H$ and a map $\gamma \in W_{\mathit{loc}}^{1,1}({\mathbb{R}}_{+},{\mathbb{R}}_{+})$ such that ${\lim }_{t\to +\infty }\gamma (t)=0$, our purpose is to study the asymptotic behavior of the following semilinear hyperbolic equation$\frac{d^{2}u}{d{t}^2}(t)+\gamma (t)\frac{du}{dt}(t)+Au(t)+f(u(t))=0,t?0.$ The nonlinearity f is assumed to be monotone and conservative. Condition ${\int }_0^{+\infty }\gamma (t)dt=+\infty$ guarantees that some suitable energy function tends toward its minimum. The main contribution of this paper is to provide a general result of convergence for the trajectories of (E): if the quantity $\gamma (t)$ behaves as $k/t^{\alpha }$, for some $\alpha \in ]0,1[$, $k>0$ and t large enough, then $u(t)$ weakly converges in V toward an equilibrium as $t\to +\infty$. Strong convergence in V holds true under compactness or symmetry conditions. We also give estimates for the speed of convergence of the energy under some ellipticity-like conditions. The abstract results are applied to particular semilinear evolution problems at the end of the paper.     

Auxiliary functions of the PsbO, PsbP and PsbQ proteins of higher plant Photosystem II: a critical analysis

Numerous studies over the last 25 years have established that the extrinsic PsbO, PsbP and PsbQ proteins of Photosystem II play critically important roles in maintaining optimal manganese, calcium and chloride concentrations at the active site of Photosystem II. Chemical or genetic removal of these components induces multiple and profound defects in Photosystem II function and oxygen-evolving complex stability. Recently, a number of studies have indicated possible additional roles for these proteins within the photosystem. These include putative enzymatic activities, regulation of reaction center protein turnover, modulation of thylakoid membrane architecture, the mediation of PS II assembly/stability, and effects on the reducing side of the photosystem. In this review we will critically examine the findings which support these auxiliary functions and suggest additional lines of investigations which could clarify the nature of the functional interactions of these proteins with the photosystem.     

Painlevé Transcendent Evaluations of Finite System Density Matrices for 1d Impenetrable Bosons

 The recent experimental realisation of a one-dimensional Bose gas of ultra cold alkali atoms has renewed attention on the theoretical properties of the impenetrable Bose gas. Of primary concern is the ground state occupation of effective single particle states in the finite system, and thus the tendency for Bose-Einstein condensation. This requires the computation of the density matrix. For the impenetrable Bose gas on a circle we evaluate the density matrix in terms of a particular Painlevé VI transcendent in Σ-form, and furthermore show that the density matrix satisfies a recurrence relation in the number of particles. For the impenetrable Bose gas in a harmonic trap, and with Dirichlet or Neumann boundary conditions, we give a determinant form for the density matrix, a form as an average over the eigenvalues of an ensemble of random matrices, and in special cases an evaluation in terms of a transcendent related to Painlevé V and VI. We discuss how our results can be used to compute the ground state occupations. Received: 24 July 2002 / Accepted: 26 January 2003 Published online: 13 May 2003 Communicated by L. Takhtajan     

An information theoretic approach to system differentiation on the basis of statistical dependencies between subsystems

We develop an analysis of complex systems in terms of statistical correlations between the dynamics of its subsystems as a formal framework within which to understand processes of system differentiation.     

Finite Dimensional Attractor for a One-Phase Stefan Problem with Kinetics

For a one-phase free-boundary problem with kinetics, which is known to generate a rich dynamics, we study evolution of the infinitesimal volume along the trajectories in the attractor. We demonstrate that for sufficiently large m that is defined solely by the properties of the kinetics function the m-dimensional volume decays exponentially. This property combined with the uniform differentiability of the semigroup leads to the conclusion that the Hausdorff dimension of the attractor is finite.