Energy balance of mussels Mytilus galloprovincialis: the effect of length and age

Clearance and ingestion rates, absorption efficiencies and respiration rates were measured in mussels Mytilus galloprovincialis Lmk of different lengths (53 to 89 mm) and age (10 to 24 mo) from cultivation rafts in the Ría de Arosa (Galicia, Spain). The experiments were carried out either in the laboratory, using monoalgal food (Isochrysis galbana) with an organic content of 91%, or under natural conditions of food availability in cultivation rafts with seston, the organic content of which ranged from 33 to 69%. Food concentrations ranged from 0.57 to 1.00 mg l-1 of total particulate matter (TPM), a load which is below the threshold for the production of pseudofaeces in Mytilus. These experiments proved that the ingestion rate (IR = mg TPM h-1) of food increases with the size of the mussel (measured as g of soft-tissue dry weight [DW]) according to the power equation IR = 12.661DW0.619, this model accounting for over 90% of the variance of the IR. Behavioural patterns that tended to maintain constant IR regardless of the density of the food were observed. Absorption efficiency (AE) is positively related to the organic content (OC) of the food according to the following hyperbolic equation: AE = 1.015 - 0.163(1/OC) (r = 0.940). AE is independent of mussel size for most of the size range used in this study, but there is a critical length around 85 mm, above which there is a noticeable decrease of AE. Metabolic expenditure, measured in terms of oxygen consumption standarized per unit of dry weight of flesh, tends to increase with the age of the mussel. The results obtained led to the conclusion that physiological traits such as the regulation of ingestion or differences in AE between groups do not explain the differences in growth between mussels of the same age. These differences must therefore be due to the limited food and space available as a result of the large numbers of mussels on the cultivation rafts and the agglomeration of mussels on the cultivation ropes.Versión de editor

Why are the Trial-By-Trial, Strength-Based Criterion Shifts Hard to Observe? Is the Difficulty in the Mental Process Itself or in the Typical Cued-Criterion Method?

In the cued-criterion recognition paradigm (Stretch & Wixted, 1998a), trial-by-trial memory-strength based criterion shifts have been an elusive phenomenon. Often the criterion shifts fail to occur. We suggest that the frequent failure in making criterion shifts in the literature is due to participants’ failure to understand the rationale of the task as typically presented in an abstract format. In this study, participants studied words once or thrice and were asked at test to either classify the probes into “new”, “seen once”, or “seen 3 times” categories by pressing the corresponding keys, or to make an Old/New binary decision followed by an item presentation-frequency judgment, a confidence, or a memory-quality judgment. No memory-strength cues were provided and only one set of new items served as distractors for strong and weak targets. Robust trial-by-trial criterion shift was observed. We concluded that no cues distinguishing between strong and weak probes are necessary for obtaining this type of criterion shift when the tasks are designed to make good pragmatic sense for the participants. The reason why this type of criterion shifts is typically hard to obtain in the cued-criterion paradigm is not that the process itself is difficult, but that the cued-criterion method is hard to understand to the participants

Electromagnetic pumps for liquid metals

This thesis is the result of a literary research on the subject of electromagnetic pumps for liquid metals. The research was conducted at the U. S. Naval Postgraduate School to educate the authors in the field of electromagnetic pumps and to fulfill requirements for a Master of Science Degree in Electrical Engineering. This thesis which is a synopsis of information obtained from various technical publications is designed to give the reader information on the theory and design of electromagnetic pumps in general. Included are: (l) Description of operation of all types of conduction and induction pumps (2) The development of the DC conduction pump from the equivalent circuit. (3)Dcvelopnent of electrical efficiency (4) Analysis of armature reaction. (5) A comprehensive bibliography. The important results of work performed in the laboratory by various individuals has been included.http://www.archive.org/details/electromagneticp00gutiLieutenant, Junior Grade, Chilean NavyLieutenant, United States NavyApproved for public release; distribution is unlimited

Rare Events and Scale--Invariant Dynamics of Perturbations in Delayed Dynamical Systems

We study the dynamics of perturbations in time delayed dynamical systems. Using a suitable space-time coordinate transformation, we find that the time evolution of the linearized perturbations (Lyapunov vector) can be mapped to the linear Zhang surface growth model [Y.-C. Zhang, J. Phys. France {\bf 51}, 2129 (1990)], which is known to describe surface roughening driven by power-law distributed noise. As a consequence, Lyapunov vector dynamics is dominated by rare random events that lead to non-Gaussian fluctuations and multiscaling properties.Comment: Final version to appear in Phys. Rev. Lett., 4 pages, 3 eps fig

Spectral behavior of contractive noise

We study the behavior of the spectra corresponding to quantum systems subjected to a contractive noise, i.e. the environment reduces the accessible phase space of the system, but the total probability is conserved. We find that the number of long lived resonances grows as a power law in $\hbar$ but surprisingly there is no relationship between the exponent of this power law and the fractal dimension of the corresponding classical attractor. This is in disagreement with the predictions of the fractal Weyl law which has been established for open systems where the probability is lost under the effect of a projective noise.Comment: 5 pages, 8 figure

Positive and negative streamers in ambient air: modeling evolution and velocities

We simulate short positive and negative streamers in air at standard temperature and pressure. They evolve in homogeneous electric fields or emerge from needle electrodes with voltages of 10 to 20 kV. The streamer velocity at given streamer length depends only weakly on the initial ionization seed, except in the case of negative streamers in homogeneous fields. We characterize the streamers by length, head radius, head charge and field enhancement. We show that the velocity of positive streamers is mainly determined by their radius and in quantitative agreement with recent experimental results both for radius and velocity. The velocity of negative streamers is dominated by electron drift in the enhanced field; in the low local fields of the present simulations, it is little influenced by photo-ionization. Though negative streamer fronts always move at least with the electron drift velocity in the local field, this drift motion broadens the streamer head, decreases the field enhancement and ultimately leads to slower propagation or even extinction of the negative streamer.Comment: 18 pages, 10 figure

Virtual photons in imaginary time: Computing exact Casimir forces via standard numerical-electromagnetism techniques

We describe a numerical method to compute Casimir forces in arbitrary geometries, for arbitrary dielectric and metallic materials, with arbitrary accuracy (given sufficient computational resources). Our approach, based on well-established integration of the mean stress tensor evaluated via the fluctuation-dissipation theorem, is designed to directly exploit fast methods developed for classical computational electromagnetism, since it only involves repeated evaluation of the Green's function for imaginary frequencies (equivalently, real frequencies in imaginary time). We develop the approach by systematically examining various formulations of Casimir forces from the previous decades and evaluating them according to their suitability for numerical computation. We illustrate our approach with a simple finite-difference frequency-domain implementation, test it for known geometries such as a cylinder and a plate, and apply it to new geometries. In particular, we show that a piston-like geometry of two squares sliding between metal walls, in both two and three dimensions with both perfect and realistic metallic materials, exhibits a surprising non-monotonic ``lateral'' force from the walls.Comment: Published in Physical Review A, vol. 76, page 032106 (2007

Non-minimally coupled scalar fields and isolated horizons

The isolated horizon framework is extended to include non-minimally coupled scalar fields. As expected from the analysis based on Killing horizons, entropy is no longer given just by (a quarter of) the horizon area but also depends on the scalar field. In a subsequent paper these results will serve as a point of departure for a statistical mechanical derivation of entropy using quantum geometry.Comment: 14 pages, 1 figure, revtex4. References and minor clarifications adde

Hall noise and transverse freezing in driven vortex lattices

We study driven vortices lattices in superconducting thin films. Above the critical force $F_c$ we find two dynamical phase transitions at $F_p$ and $F_t$, which could be observed in simultaneous noise measurements of the longitudinal and the Hall voltage. At $F_p$ there is a transition from plastic flow to smectic flow where the voltage noise is isotropic (Hall noise = longitudinal noise) and there is a peak in the differential resistance. At $F_t$ there is a sharp transition to a frozen transverse solid where the Hall noise falls down abruptly and vortex motion is localized in the transverse direction.Comment: 4 pages, 3 figure