A study of the age, growth, sexual maturity, and spawning of the anchoveta, Cetengraulis mysticetus, in the Gulf of Panama

ENGLISH: Crew members of tuna clippers and Commission personnel are collecting specimens of anchovetas (Cetengraulis mysticetus) for studies of the biology of this important tuna-bait species. More than 27,000 fish from 231 collections captured in the Gulf of Panama between June 1951 and January 1956 are the basis of this study of the age, growth, sexual maturity, and spawning season of this species in that area. Estimates of age and rate of growth were made by studying the temporal progression of modal size groups from monthly length frequency distributions. Sexual development and time of spawning were determined from gross examination of ovaries and measurements of ovarian eggs. SPANISH: Con el fin de estudiar la biología de la anchoveta (Cetengraulis mysticetus) los tripulantes de los barcos atuneros y el personal de la Comisión están recolectando especimenes de esta importante especie de carnada para capturar el atún. Mas de 27,000 ejemplares de las 231 colecciones hechas en el Golfo de Panamá entre junio de 1951 y enero de 1956, sirven de material al presente estudio sobre la edad, el crecimiento, la madurez sexual y las épocas de desove de esta especie en el área indicada. Las estimaciones de la edad y de la proporción del crecimiento fueron hechas a base del estudio de la progresión temporal de los grupos modales de tamaño en las distribuciones mensuales de frecuencias de longitud. El desarrollo sexual y el periodo de desove fueron determinados mediante el examen microscópico de los ovarios y las mediciones de los huevos ováricos. (PDF contains 79 pages.

Changes in the dynamical behavior of nonlinear systems induced by noise.

Weak noise acting upon a nonlinear dynamical system can have far-reaching consequences. The fundamental underlying problem - that of large deviations of a nonlinear system away from a stable or metastable state, sometimes resulting in a transition to a new stationary state, in response to weak additive or multiplicative noise - has long attracted the attention of physicists. This is partly because of its wide applicability, and partly because it bears on the origins of temporal irreversibility in physical processes. During the last few years it has become apparent that, in a system far from thermal equilibrium, even small noise can also result in qualitative change in the system's properties, e.g., the transformation of an unstable equilibrium state into a stable one, and vice versa, the occurrence of multistability and multimodality, the appearance of a mean field, the excitation of noise-induced oscillations, and noise-induced transport (stochastic ratchets). A representative selection of such phenomena is discussed and analyzed, and recent progress made towards their understanding is reviewed

A new species of <i>Parthenope</i> Weber (Crustacea: Brachyura: Parthenopidae) from the Pacifc coast of Mexico

A new species of Parthenopidae from the East Pacific belonging to the genus Parthenope Weber is described and illustrated. Parthenope johngarthi n. sp. was collected along the west coast of Mexico, off the coast of Jalisco and Colima. Parthenope johngarthi is readily distinguished from species of other genera of Parthenopidae from the East Pacific by the shape of the tuberculate carapace, the relative lenght and shape of the chelipeds, and the shape and relative size of segments of walking legs. It is closely related to P. exilipes (Rathbun, 1893) but differs from the latter by its slender and almost smooth walking legs, its slender and less densely tuberculate chelipeds, and by its almost straight, narrower rostrum. Comparison of male first gonopods from both species also indicates differences that are considered of specific value

Development of turbulence in submerged jets as a noise-induced transition

Experiments show that the amplitude of turbulent pulsation in submerged jets rises with increasing distance from the nozzle, at first slowly and then, after a certain distance, rapidly. This dependence on distance from the nozzle closely resembles the dependence of an order parameter on temperature in the case of a second-order phase transition. Following an idea introduced by Landa and Zaikin in 1996, it is suggested that the onset of turbulence is a noise-induced phase transition similar to that in a pendulum with a randomly vibrated suspension axis. The Krylov-Bogolyubov asymptotic method is used to provide an approximate description of the transition. Results obtained in this way are shown to coincide closely with experimental data. Such an approach is appropriate because the convective character of the instability means that turbulence in nonclosed flows cannot be a self-oscillatory process, as is often assumed. Rather, it must originate in the external random disturbances that are always present in real flows

Nonlinear dynamics of coupled transverse-rotational waves in granular chains

The nonlinear dynamics of coupled waves in one-dimensional granular chains with and without a substrate is theoretically studied accounting for quadratic nonlinearity. The multiple time scale method is used to derive the nonlinear dispersion relations for infinite granular chains and to obtain the wave solutions for semiinfinite systems. It is shown that the sum-frequency and difference-frequency components of the coupled transverse-rotational waves are generated due to their nonlinear interactions with the longitudinal wave. Nonlinear resonances are not present in the chain with no substrate where these frequency components have low amplitudes and exhibit beating oscillations. In the chain positioned on a substrate two types of nonlinear resonances are predicted. At resonance, the fundamental frequency wave amplitudes decrease and the generated frequency component amplitudes increase along the chain, accompanied by the oscillations due to the wave numbers asynchronism. The results confirm the possibility of a highly efficient energy transfer between the waves of different frequencies, which could find applications in the design of acoustic devices for energy transfer and energy rectification

Model of the evolution of acoustic emission as the randomization of transient processes in coupled nonlinear oscillators

The behavior of a crack as a resonator radiating acoustic emission (AE) pulses at instants of sudden growth is investigated theoretically and experimentally. This resonance behavior of a growing crack is determined to a large extent by surface waves propagating along its edges. The crack can therefore be regarded as an acoustic resonator excited at the instant of growth of its tip. Transformations in the form of high-frequency harmonic and combination-frequency subharmonic generation are observed in the spectra of the AE signals. The final stage in the evolution of AE is characterized by the transition to a wideband noise spectrum. These facts lead to the hypothesis that bifurcations analogous to those encountered in the onset of dynamic chaos take place in the AE process. This hypothesis forms the basis of a mathematical model of the AE process as a system of coupled nonlinear oscillators, each corresponding to an individual crack. The initial displacement in one of the interacting cracks is adopted as the bifurcation parameter. Spectra calculated by computer simulation exhibit qualitative agreement with the evolution of the spectra obtained in the processing of data from physical experiments

Symmetry broken motion of a periodically driven Brownian particle: nonadiabatic regime

We report a theoretical study of an overdamped Brownian particle dynamics in the presence of both a spatially modulated one-dimensional periodic potential and a periodic alternating force (AF). As the periodic potential has a low symmetry (a ratchet potential) the Brownian particle displays a broken symmetry motion with a nonzero time average velocity. By making use of the Green function method and a mapping to the theory of Brillouin bands the probability distribution of the particle coordinate is derived and the nonlinear dependence of the macroscopic velocity on the frequency and the amplitude of AF is found. In particular, our theory allows to go beyond the adiabatic limit and to explain the peculiar reversal of the velocity sign found previously in the numerical analysis.Comment: 4 pages, 2 figure

Modes of Oscillation in Radiofrequency Paul Traps

We examine the time-dependent dynamics of ion crystals in radiofrequency traps. The problem of stable trapping of general three-dimensional crystals is considered and the validity of the pseudopotential approximation is discussed. We derive analytically the micromotion amplitude of the ions, rigorously proving well-known experimental observations. We use a method of infinite determinants to find the modes which diagonalize the linearized time-dependent dynamical problem. This allows obtaining explicitly the ('Floquet-Lyapunov') transformation to coordinates of decoupled linear oscillators. We demonstrate the utility of the method by analyzing the modes of a small `peculiar' crystal in a linear Paul trap. The calculations can be readily generalized to multispecies ion crystals in general multipole traps, and time-dependent quantum wavefunctions of ion oscillations in such traps can be obtained.Comment: 24 pages, 3 figures, v2 adds citations and small correction