Modelling exchange bias in core/shell nanoparticles

We present an atomistic model of a single nanoparticle with core/shell structure that takes into account its lattice strucutre and spherical geometry, and in which the values of microscopic parameters such as anisotropy and exchange constants can be tuned in the core, shell and interfacial regions. By means of Monte Carlo simulations of the hysteresis loops based on this model, we have determined the range of microscopic parameters for which loop shifts after field cooling can be observed. The study of the magnetic order of the interfacial spins for different particles sizes and values of the interfacial exchange coupling have allowed us to correlate the appearance of loop asymmetries and vertical displacements to the existence of a fraction of uncompensated spins at the shell interface that remain pinned during field cycling, offering new insight on the microscopic origin of the experimental phenomenology.Comment: 7 pages, 3 figures. Contribution presented at HMM 2007 held at Napoli 4-6 June 2007. To be published in J. Phys. Condens. Matte

Grenadiers in the Spanish Fishery of Greenland Halibut, NAFO Divisions 3LM and 3N, 1991-1993

In the Spanish Greenland halibut fishery, grenadier are an important component in the by-catch. Their catch, catch-rate and size distribution were analyzed during the period 1991 to 1993.The importance of these species in relation to the targetted species increased in the period studied and the proportion between the two in by-catch was approximately 50%. Yields were greater during the first half year period, and increased with depth. Sizes of roundnoes were smaller to the south (3N) whereas roughead sizes were larger in this same division

S wave velocity structure below central Mexico using high-resolution surface wave tomography

Shear wave velocity of the crust below central Mexico is estimated using surface wave dispersion measurements from regional earthquakes recorded on a dense, 500 km long linear seismic network. Vertical components of regional records from 90 well-located earthquakes were used to compute Rayleigh-wave group-velocity dispersion curves. A tomographic inversion, with high resolution in a zone close to the array, obtained for periods between 5 and 50 s reveals significant differences relative to a reference model, especially at larger periods (>30 s). A 2-D S wave velocity model is obtained from the inversion of local dispersion curves that were reconstructed from the tomographic solutions. The results show large differences, especially in the lower crust, among back-arc, volcanic arc, and fore-arc regions; they also show a well-resolved low-velocity zone just below the active part of the Trans Mexican Volcanic Belt (TMVB) suggesting the presence of a mantle wedge. Low densities in the back arc, inferred from the low shear wave velocities, can provide isostatic support for the TMVB

Distribution of American Plaice (Hippoglossoides platesssoides) on the Grand Bank (NAFO Divisions 3NO), 1995-2004

The changes appreciated in the distribution of American plaice (Hippoglossoides platessoides) by depth on the Grand Bank (NAFO Divisions 3NO) in the period 2001-04 did not show a clear relationship with the increase of estimated biomass. Significant differences in the distribution depth range between sizes and sexes were observed. The females were distributed until deeper than the males. The small individuals (<20 cm) also appeared in the deepest strata. Inter-annual changes were appreciated in the period 2001-04 with an accused decrease in the distribution depth range in the 2004. The population was concentrated at shallower depth in spite of the increment of the abundance and biomass in the last year

Occurrence of American plaice (Hippoglossoides platessoides) at Non-habitual Depths in the Northwest Atlantic, 1990–93

In 1992 and 1993 American plaice (Hippoglossoides platessoides) was detected in the catches of the Spanish fleet at depths greater than those habitual to the species (>800 m). The maximum depth was registered in Div. 3L at more than 1 400 m. The maximum yields of this species at depths over 800 m were observed in Div. 3N. The presence of American plaice at great depths was mainly detected in the first half of the year, and most predominantly at the end of winter and beginning of spring. No clear relationship between the length distribution and the depths reached were observed

Towards segmentation and spatial alignment of the human embryonic brain using deep learning for atlas-based registration

We propose an unsupervised deep learning method for atlas based registration to achieve segmentation and spatial alignment of the embryonic brain in a single framework. Our approach consists of two sequential networks with a specifically designed loss function to address the challenges in 3D first trimester ultrasound. The first part learns the affine transformation and the second part learns the voxelwise nonrigid deformation between the target image and the atlas. We trained this network end-to-end and validated it against a ground truth on synthetic datasets designed to resemble the challenges present in 3D first trimester ultrasound. The method was tested on a dataset of human embryonic ultrasound volumes acquired at 9 weeks gestational age, which showed alignment of the brain in some cases and gave insight in open challenges for the proposed method. We conclude that our method is a promising approach towards fully automated spatial alignment and segmentation of embryonic brains in 3D ultrasound

An attempt to determine variability of RNA/DNA ratios during Dicentrarchus labrax larval development

RNA and DNA content of seabass (Dicentrarchus labra.x) larvae were determined from day 10 to day 60 after hatching in an aquaculture facility. Our results show a two-phase modulation of the RNA/DNA ratio throughout seabass larvae development. From day 10 after hatching there is an increase in the RNA/DNA ratio reaching maximal values at day 30 of age. Then, the RNA/DNA ratio decreased reaching minimal values at day 60 after hatching. These results are consistent with a high rate of protein synthesis during the first 30 days of seabass development compared with the rest of the developmental period studied. The results are compared with that of otolith growth carried out for the same species larvaeAPROXIMACIÓ A LA DETERMINACIÓ DE LA VARIABILITAT DE LA RELACIÓ DNA/RNA DURANT EL DESENVOLUPAMENT LARVAL DEL LLOBARRO Dicentrarchus labrax. S'ha determinat el contingut de DNA (àcid desoxiribonucleic) i de RNA (àcid ribonucleic) en larves de llobarro (Dicentrarchus labrax) d'edats compreses entre 10 i 60 dies de vida, procedents d'una planta de cultiu. Els resultats obtinguts mostren dues fases diferenciades de desenvolupament d'aquestes larves, basades en la relaci6 RNA/DNA avaluada. S'observa un augment de la proporci6 de RNNDNA des del dia 10 fins el dia 30 de vida, per a decréixer a continuació, trobant els valors mínims en les larves de 60 dies de vidaPublicado

The masses of hot subdwarfs

Masses are a fundamental parameter, but they are not well known for most hot subdwarfs. In general, the mass of a hot subdwarf is derived with asteroseismology or dynamical methods, for which it is often difficult to obtain the necessary data from observations. We intend to find an approach to deriving the masses of hot subdwarfs from observational data in the literature. We presented full evolutionary calculations for hot subdwarfs in a wide mass range (0.33 $M_\odot$ to 1.4 $M_\odot$) for a Population I metallicity of $Z$=0.02, and obtained a relation between $M_{\rm p}$ and $\log (\frac{T_{\rm eff}^4}{g})$, where $M_{\rm p}$, $T_{\rm eff}$, and $g$ are the most probable mass, effective temperature, and gravity. This relation is used to study the masses of some observed hot subdwarfs. We proposed a method of determining the masses of hot subdwarfs. Using this method, we studied the masses of hot subdwarfs from the ESO supernova Ia progenitor survey and Hamburg quasar survey. The study shows that most of subdwarf B stars have masses between 0.42 and 0.54 $M_\odot$, whilst most sdO stars are in the range 0.40 $\sim$ 0.55 $M_\odot$. Comparing our study to the theoretical mass distributions of Han et al. (2003), we found that sdO stars with mass less than $\sim$ 0.5 $M_\odot$ may evolve from sdB stars, whilst most high-mass($>$ 0.5 $M_\odot$) sdO stars result from mergers directly.Comment: 5 pages, 6 figures, accepted for publication in A&A Letter

Condition and Feeding of Greenland Halibut (Reinhardtius hippoglossoides) in the North Atlantic with Emphasis on the Flemish Cap

The Relative Condition Factor of Greenland halibut (Reinhardtius hippoglossoides) was analysed for seasonal, annual and geographical variability. Sampling covered commercial fishing and scientific surveys in three areas of the North Atlantic (NAFO Divisions 3M and 3LNO, and ICES Division IIb), comprising a total of 64 984 individuals from 1992 to 2003. Several data sets were established in order to carry out the comparisons: individuals as a whole; by sex - females and males separately; and by areas - each area independently. Condition showed significant differences with regard to the area, season, size range and sex, but it was not always significant among interactions of these factors. Individuals from the Northeast Atlantic had better condition, while those in the Northwest Atlantic suffered a notable fall in condition throughout the studied period, mainly in Flemish Cap. Condition was lightly superior in females, regarding size. A clear increment in the feeding intensity appeared when the condition diminished. When the total weight is used to calculate the condition, more remarkable differences could be expected because this index is sensitive to the gonad weight; in this respect, adult females showed more marked differences. Moreover, the complex maturity schedule and variable maturity at size would contribute to find misleading differences. Feeding habits of Greenland halibut were studied in the same areas based on a sample of 19 001 fish. Feeding intensity was the higher on the Flemish Cap, where the main preys were Pandalus borealis, Sebastes spp. and Serrivomer beani. P. borealis predation increased in the late 1990s. Diet was piscivorous in Div. 3LNO and Div. IIb as well, mainly based on Mallotus villosus and Micromesistius poutassou, respectively. Cannibalism and offal consumption was remarkable in Svalbard (ICES Div. IIb). Fish predation increased when predator size increased. Molluscs took an important place in the diet of intermediate sizes in Div. 3LNO and IIb. Similar diet pattern for both sexes was observed