Histological Assessment of Sexual Maturity of the Flemish Cap Cod (Division 3M) in 1995

6 páginas, 5 tablas, 2 fisguras.-- Scientific Council Meetin

Sexual Maturity of Cod (Gadus morhua) in Flemish Cap (Div. 3M)

6 páginas, 3 tablas, 2 figuras.-- Scientific Council Meetin

Spanish Pelagic Redfish (Sebastes mentella) Fishery in the NAFO Regulatory Area (Division 1F) in 2000

In early October 2000 an exploratory fishing for oceanic redfish have been conducted by one Spanish pelagic trawler in the NAFO Regulatory Area of Div. 1F. One scientific observer was on board this vessel during the whole fishing period. The seasonal and geographic distribution pattern of the fishing effort in the Spanish oceanic redfish fishery is presented. A shift in the fleet activity towards the south and west is observed between the second and third quarter, approaching the vicinity of the NAFO Convention area. In the fourth quarter no fishing activity occurred in the Irminger Sea, and the fleet activity concentrated in NAFO Div. 1F. The length distribution in NAFO Div. 1F is similar to the one recorded in the NEAFC oceanic redfish fishery by the Spanish and German fleets in the upper 500 m layer. Only 11 % of the females and 5 % of the redfish males caught in NAFO 1F were immature (juveniles). The majority of the adult females were sexually inactive, while 49 % of the adult males were at the fully ripe stage, so it could be a mating concentration

Spawning biomass variation in Atlantic Cod (Gadus morhua) in Flemish Cap in Relation to Changes in Growth and Maturation

Drastic changes in both age- and length-at-maturity of cod (Gadus morhua) on Flemish Cap have been observed during this decade. In the present paper, growth by cohort in this period was analyzed and compared with the observed trend in maturation. Different cohorts displayed different growth rates, the strongest 1990 year-class showing fastest growth. The compensatory response to lower population density alone did not explain the decline in both age- and size-at-maturity. Strong changes in fishing pressure during the period could have provoked a size-selectivity for early maturity, i.e. genetic selection. An estimate of the spawning biomass, accounting for the corresponding size-at-age distributions, on a cohort basis is given. The influence of changes in spawning biomass and spawning stock biomass age structure on the probability of future stock rebuilding is also discussed. It is shown a low spawning biomass composed of young and recruited females will hardly rebuild the stock to historical levels

Histological Assessment of Sexual Maturity of the Flemish Cap Cod in 1995

In this paper the proportion of females with postovulatory follicles in their ovaries in July 1995 is used to determine the length- and age-at-maturity of cod (Gadus morhua) in the year 1995. The proportion of females in the cortical alveoli stage is then used to estimate the same parameters for 1996. This histological method allows to accurately detect the proportion of both adult and primiparous females in the population at the very beginning of the gonad development, as it happens in the summer, and few months after spawning, when it is very difficult to make a visual diagnosis of the sexual maturity stage. Length and age at 50% maturity obtained from the curves plotting the proportion of cortical alveoli were 39.07 cm and 3.1 years, respectively. The same parameters obtained from postovulatory follicle frequencies were 42.65 cm and 3.9 years, respectively. During the period from 1990 to 1995, a decrease in both length- and age-at-maturity was observed for cod on Flemish Cap. It seems likely that in those recent years the age-at-maturity of female cod was fixed around age 3. The possibility that these features could be a density-dependent response is discussed

Histological Assessment of Sexual Maturity in Greenland Halibut in Div. 3LM

11 páginas, 6 tablas, 1 figura.-- Scientific Council Meetin

Band alignment at metal/ferroelectric interfaces: insights and artifacts from first principles

Based on recent advances in first-principles theory, we develop a general model of the band offset at metal/ferroelectric interfaces. We show that, depending on the polarization of the film, a pathological regime might occur where the metallic carriers populate the energy bands of the insulator, making it metallic. As the most common approximations of density functional theory are affected by a systematic underestimation of the fundamental band gap of insulators, this scenario is likely to be an artifact of the simulation. We provide a number of rigorous criteria, together with extensive practical examples, to systematically identify this problematic situation in the calculated electronic and structural properties of ferroelectric systems. We discuss our findings in the context of earlier literature studies, where the issues described in this work have often been overlooked. We also discuss formal analogies to the physics of polarity compensation at LaAlO3/SrTiO3 interfaces, and suggest promising avenues for future research.Comment: 29 pages, 23 figure

Neutron Irradiation Tests of Calibrated Cryogenic Sensors at Low Temperatures

This paper presents the advancement of a program being carried out in view of selecting the cryogenic temperature sensors to be used in the LHC accelerator. About 10,000 sensors will be installed around the 26.6 km LHC ring, and most of them will be exposed to high radiation doses during the accelerator lifetime. The following thermometric sensors : carbon resistors, thin films, and platinum resistors, have been exposed to high neutron fluences (>10$^15$ n/cm$^2$) at the ISN (Grenoble, France) Cryogenic Irradiation Test Facility. A cryostat is placed in a shielded irradiation vault where a 20 MeV deuteron beam hits a Be target, resulting in a well collimated and intense neutron beam. The cryostat, the on-line acquisition system, the temperature references and the main characteristics of the irradiation facility are described. The main interest of this set-up is its ability to monitor online the evolution of the sensors by comparing its readout with temperature references that are in principle insensitive to the neutron radiation (i.e. Argon gas bulbs when working at about 84 K, and below 4.5 K, either helium gas bulbs or the saturation pressure of the superfluid helium bath). The resistance shifts of the different sensors at liquid helium temperatures are presented