Vitrification and dehydration for the preservation of gametes

Of the 36 species of felines in the world, all except the domestic cat are listed as endangered or threatened. To preserve the genetic diversity of felines and other species, genome resource banks have been established. Due to limited availability of germ cells for research, studies must use models to optimize the techniques before they are applied to endangered species. In this study, preservation of oocytes and spermatozoa was examined using the bovine as a model for felines. In the first series of experiments, bovine and feline oocytes were dehydrated, vitrified, warmed and cultured to assess their ability to undergo embryonic development using a choline-based medium (CJ2) for vitrification and warming solutions preparation as well as the standard sodium based media. In the second series of experiments, feline spermatozoa were dehydrated using air- and freeze-drying as alternative methods to standard cryopreservation. Assessment was done by examining embryonic development after intracytoplasmic sperm injection (ICSI) and DNA integrity of the dehydrated spermatozoa using the comet assay. In the second series of experiments, bovine and feline oocytes behaved osmotically in response to increasingly concentrated solutions. However, vitrified-warmed bovine oocytes had significantly higher cleavage and blastocyst rates compared with their feline counterparts and development using CJ2 medium was similar to the standard media used for cattle but was detrimental to feline oocytes. In the third experiment, cleavage and blastocyst development of feline oocytes injected with cat spermatozoa preserved using air- and freeze-drying was observed. Also, exposure to the dehydration solution and vitrification did not induce DNA damage but the process of freeze-drying did have significantly higher levels compared with controls. Air-dried sperm did not decondense. In conclusion, the use of bovine oocytes as a model for feline oocytes was successful. Both bovine and feline oocytes responded similarly to dehydration and vitrification, except when processed using CJ2 medium. Furthermore, feline spermatozoa can be preserved using dehydration as demonstrated by their ability to produce blastocysts. This study has encouraging results for germ cell preservation. However, the efficiency of these procedures must be improved before they can be used as alternative methods of preservation in endangered species

Modeling Nutrient and Plankton Processes in the California Coastal Transition Zone: 3. Lagrangian Drifters

Two types of numerical Lagrangian drifter experiments were conducted, using a set of increasingly complex and sophisticated models, to investigate the processes associated with the plankton distributions in the California coastal transition zone (CTZ). The first experiment used a one-dimensional (1-D; vertical) time-dependent physical-bio-optical model, which contained a nine-component food web. Vertical velocities, along the track of simulated Lagrangian drifters, derived from a three-dimensional (3-D), primitive equation circulation model developed to simulate the flow observed within the CTZ; were used to parameterize the upwelling and downwelling processes. The second experiment used 880 simulated Lagrangian drifters from a 3-D primitive equation circulation model which was coupled to the same food web and bio-optical model used in the first experiment. Parameterization of the biological processes in both experiments were based upon data obtained during the CTZ field experiments. Comparison of simulations with data provided insight into the role of the biological and physical processes in determining the development of the subsurface chlorophyll maximum and other related features. In both studies, the vertical velocities experienced by a simulated Lagrangian drifter as it was advected offshore while entrained within a filament played a major role in determining the depth to which the euphotic zone and the chlorophyll maximum developed. Also, as the drifters moved offshore, the food web changed from a coastal, neritic food web to an offshore, oligotrophic food web due to the decrease in nutrient availability. The temporal development of the food web constituents following the simulated drifters was dependent upon the environment to which the drifter was exposed. For example, the amount of time upwelled or downwelled and the initial location in the CTZ region greatly affected the development of the food web

Modeling Nutrient and Plankton Processes in the California Coastal Transition Zone: 1. A Time- and Depth-Dependent Model

A time- and depth-dependent, physical-bio-optical model was developed for the California coastal transition zone (CTZ) with the overall objective of understanding and quantifying the processes that contribute to the vertical and temporal development of nutrient and plankton distributions in the CTZ. The model food web components included silicate, nitrate, ammonium, two phytoplankton size fractions, copepods, doliolids, euphausiids, and a detritus pool. The wavelength-dependent subsurface irradiance field was attenuated by sea water and phytoplankton pigments. The one-dimensional (1-D) model adequately simulated the development and maintenance of a subsurface chlorophyll maximum in different regions within the CTZ. An analysis of the individual terms in the model governing equations revealed that phytoplankton in situ growth was primarily responsible for the creation and maintenance of the subsurface chlorophyll maximum at both coastal and oceanic regions in the CTZ. The depth to which the maximum in situ growth occurred was controlled by the combined effect of light and nutrient limitation. Also, the simulated bio-optical fields demonstrated the effect of nonlinear couplings between food web components and the subsurface irradiance field on vertical biological distributions. In particular, the epsilon-folding scale of the subsurface photosynthetically available radiation (PAR) was influenced by the level of zooplankton grazing

Evolution of the decay mechanisms in central collisions of XeXe + SnSn from E/AE/A = 8 to 29 MeVMeV

Collisions of Xe+Sn at beam energies of $E/A$ = 8 to 29 $MeV$ and leading to fusion-like heavy residues are studied using the $4\pi$ INDRA multidetector. The fusion cross section was measured and shows a maximum at $E/A$ = 18-20 $MeV$. A decomposition into four exit-channels consisting of the number of heavy fragments produced in central collisions has been made. Their relative yields are measured as a function of the incident beam energy. The energy spectra of light charged particles (LCP) in coincidence with the fragments of each exit-channel have been analyzed. They reveal that a composite system is formed, it is highly excited and first decays by emitting light particles and then may breakup into 2- or many- fragments or survives as an evaporative residue. A quantitative estimation of this primary emission is given and compared to the secondary decay of the fragments. These analyses indicate that most of the evaporative LCP precede not only fission but also breakup into several fragments.Comment: Invited Talk given at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS

Modeling Nutrient and Plankton Processes in the California Coastal Transition Zone: 2. A Three-Dimensional Physical-Bio-Optical Model

A three-dimensional (3-D) primitive equation model, developed to simulate the circulation features (filaments) observed in the California coastal transition zone (CTZ), was coupled to a nine-component food web model and a bio-optical model. The simulated flow fields from a 3-D primitive equation model are used to advect the constituents of the food web model, which include silicate, nitrate, ammonium, two phytoplankton size fractions, copepods, doliolids, euphausiids, and a detritus pool. The bio-optical model simulates the wavelength-dependent attenuation of the subsurface irradiance field. The overall objective of this modeling study was to understand and quantify the processes that contribute to the spatial and temporal development of nutrient and plankton distributions in the CTZ. The resulting simulated 3-D nutrient, plankton and submarine light fields agree well with those observed within the CTZ. Specifically, high nutrient and plankton biomass occur onshore and within the core of the simulated filament. Variations in the depth of the 1% light level, which result from the simulated plankton distributions, shallows to less than 30 m in regions of high phytoplankton biomass, and deepens to greater than 75 m in regions of low phytoplankton biomass. The onshore and offshore surface carbon flux patterns are similar in shape due to the meander-like flow patterns of the filament; however, the net across-shore area-integrated carbon flux is predominantly offshore. The total 20-day integrated carbon transport for the model domain varies with distance from shore and is highest (35 × 109 g C) in the region where the filament circulation pattern develops into an anticyclonic and cyclonic pair of eddies. The annual integrated carbon transport by filaments along the California coast is estimated to be 1.89 × 1012 g C

Au-delà de ‘tisser le lien social au quotidien’, la construction du métier de Médiateur Social

Prefácio a “Le Tour d’Europe des médiateurs sociaux: de la valorisation de l’expérience et la formation à la reconnaissance et la professionnalisation”Médiation, ensuite. Comme vision sociale, d’abord. Celle d’une société patchwork à l’image de la tunique d’ArleKin, dont les coutures se tissent grâce à ces “espaces-tiers” de médiation: espaces où la prise de parole (la sienne) et l’écoute de l’autre (l’opposant, l’étranger, le représentant de l’institution), peuvent co-exister sans risque parce que protégés. Vision “d’une communauté paradoxale (…) en train de surgir, faite d’étrangers qui s’acceptent dans la mesure où ils se reconnaissent étrangers eux-mêmes” (Kristeva, 2007, p. 290).Référence: 539947-LLP-1-2013-1-FR- GRUNDTVIG-GMP - www.arlekin-eu.f

Le Tour d’Europe des médiateurs sociaux: de la valorisation de l’expérience et la formation à la reconnaissance et la professionnalisation

Inclusion, d’abord. Si ce n’est le mot lui-même, le projet est “au fond” de tous les témoignages qui se lisent dans cet E-book. Nous laissons le lecteur le découvrir par lui-même. C’est ce qui, fondamentalement donne sens aux activités des médiateurs. Contre une société qui exclue, discrimine, construit des murs et des frontières, calcule au “moins-disant” l’accueil des demandeurs d’asile, rejette les individus vers leur communauté d’appartenance et les y enferme au lieu de leur permettre d’y trouver les ressources pour s’ouvrir à l’altérité et leur société d’accueil – la médiation est là pour retisser les liens, donner accès aux droits, permettre le long apprentissage d’institutions qui existent pour les protéger, développer leur confiance en eux-mêmes, s’ouvrir à sa propre richesse pour s’ouvrir à celle de l’autre et résoudre les multiples conflits de la vie quotidienne.Référence: 539947-LLP-1-2013-1-FR- GRUNDTVIG-GMP - www.arlekin-eu.f