164 research outputs found
Light Scattering from Nonequilibrium Concentration Fluctuations in a Polymer solution
We have performed light-scattering measurements in dilute and semidilute
polymer solutions of polystyrene in toluene when subjected to stationary
temperature gradients. Five solutions with concentrations below and one
solution with a concentration above the overlap concentration were
investigated. The experiments confirm the presence of long-range nonequilibrium
concentration fluctuations which are proportional to , where
is the applied temperature gradient and is the wave number of
the fluctuations. In addition, we demonstrate that the strength of the
nonequilibrium concentration fluctuations, observed in the dilute and
semidilute solution regime, agrees with theoretical values calculated from
fluctuating hydrodynamics. Further theoretical and experimental work will be
needed to understand nonequilibrium fluctuations in polymer solutions at higher
concentrations.Comment: revtex, 16 pages, 7 figures. J. Chem. Phys., to appea
Dynamics of fluctuations in a fluid below the onset of Rayleigh-B\'enard convection
We present experimental data and their theoretical interpretation for the
decay rates of temperature fluctuations in a thin layer of a fluid heated from
below and confined between parallel horizontal plates. The measurements were
made with the mean temperature of the layer corresponding to the critical
isochore of sulfur hexafluoride above but near the critical point where
fluctuations are exceptionally strong. They cover a wide range of temperature
gradients below the onset of Rayleigh-B\'enard convection, and span wave
numbers on both sides of the critical value for this onset. The decay rates
were determined from experimental shadowgraph images of the fluctuations at
several camera exposure times. We present a theoretical expression for an
exposure-time-dependent structure factor which is needed for the data analysis.
As the onset of convection is approached, the data reveal the critical
slowing-down associated with the bifurcation. Theoretical predictions for the
decay rates as a function of the wave number and temperature gradient are
presented and compared with the experimental data. Quantitative agreement is
obtained if allowance is made for some uncertainty in the small spacing between
the plates, and when an empirical estimate is employed for the influence of
symmetric deviations from the Oberbeck-Boussinesq approximation which are to be
expected in a fluid with its density at the mean temperature located on the
critical isochore.Comment: 13 pages, 10 figures, 52 reference
Sampling protocol for skeletal structures of North Atlantic albacore tuna (Thunnus alalunga) and ageing interpretation
This paper presents a standardized protocol for sampling skeletal hard parts (dorsal fin ray
and otoliths), preparation and age interpretation of albacore first dorsal fin ray. Ageing of
albacore is focused in interpretation and reading of annual temporal marks (translucent bands)
in first ray of dorsal fin. Preparation of fin ray sections (spines) is presented in detail using two
different methods. The spines are usually cut individually using a low speed cutter. Depending
of the size of spines, a new procedure has been developed for small spines based on encasing
spines in a matrix of plastic resin allowing multiple spines cutting. Interpretation of growth
marks on spine sections is explained and examples are presented for a range of size of albacore
aged using this method.Ce document présente un protocole standardisé pour l’échantillonnage des pièces dures du
squelette (rayon de la nageoire dorsale et otolithes), la préparation et l’interprétation de l’âge
du rayon du premier rayon de la nageoire dorsale du germon. La détermination de l’âge du
germon se centre sur l’interprétation et la lecture des marques temporelles annuelles (bandes
translucides) du premier rayon de la nageoire dorsale. La préparation des sections du rayon de
la nageoire (épines) est présentée en détail à l’aide de deux méthodes différentes. Les épines
sont généralement sectionnées individuellement en utilisant un couteau basse vitesse. Selon la
taille des épines, une nouvelle procédure a été élaborée pour les petites épines, consistant Ã
enfermer les épines dans une matrice en résine plastique qui permet le découpage de plusieurs
épines. L’interprétation des marques de croissance sur les sections des épines est expliquée et
des exemples sont donnés pour une gamme de tailles de germon dont l’âge a été déterminé Ã
l’aide de cette méthode.En este documento se presenta un protocolo estandarizado para el muestreo de partes duras
del esqueleto (otolitos y rayo de la aleta dorsal) y para la preparación e interpretación de la
edad del primer rayo de la aleta dorsal del atún blanco. La determinación de la edad del atún
blanco se centra en la interpretación y lectura de las marcas temporales anuales (bandas
traslucidas) en el primer rayo de la aleta dorsal. Se presenta en detalle la preparación de las
secciones del rayo de la aleta (espinas) utilizando dos métodos diferentes. Las espinas suelen
cortarse generalmente de forma individual utilizando un cortador de baja velocidad.
Dependiendo del tamaño de las espinas, se ha desarrollado un nuevo procedimiento para las
espinas pequeñas, que consiste en introducir las espinas en una matriz de resina plástica que
permite cortar espinas múltiples. Se explica la interpretación de las marcas de crecimiento en
las secciones de espinas y se presentan ejemplos para una gama de tallas de atún blanco cuya
edad se determinó utilizando este método
Impact of thermodiffusion on the initial vertical distribution of species in hydrocarbon reservoirs
Application of age-length-keys to estimate catch-at-age for the North Atlantic albacore (Thunnus alalunga) stock
This document presents the results of applying two different methods to estimate catch-at-age
for North Atlantic albacore (Thunnus alalunga). The Spanish albacore surface fishery size
frequency data from 2003 to 2005 have been analyzed by means of MULTIFAN and age-lengthkeys
(ALKs) have been derived from readings of sections obtained from sampled dorsal spiny
rays of catch landed.Ce document présente les résultats de l’application de deux méthodes différentes visant Ã
estimer la prise par âge pour le germon de l’Atlantique Nord (Thunnus alalunga). Les données
de fréquences de tailles de la pêcherie de surface espagnole ciblant le germon de 2003 à 2005
ont été analysées à l’aide de MULTIFAN et des clefs âge-taille ont été calculées (ALKs)
d’après la lecture des sections obtenues des rayons épineux de la dorsale échantillonnées de la
prise débarquée.Este documento presenta los resultados de aplicar dos métodos distintos para estimar la
captura por edad del atún blanco del Atlántico norte. La distribución por talla de las capturas
comerciales de las flotas españolas de superficie fue analizada con MULTIFAN. Las claves
talla edad fueron obtenidas por medio de la lectura de secciones de radios espinosos
muestreados a partir de las capturas comerciales
- …