706 research outputs found
Further improvements in the sea urchin embryo cryopreservation protocol (Paracentrotus lividus)
Post-print2,06
Development of Detailed Chemistry Models for Boundary Layer Catalytic Recombination
During the (re-)entry phase of a space vehicle, the gas flow in the shock layer can be in a
state of strong thermal non-equilibrium. Under these circumstances, the population of the
internal energy levels of the atoms and molecules of the gas deviates from the Boltzmann
distribution. A substantial increase of the heat flux transferred from the gas
to the vehicle is possible, as the thermal protection system of the vehicle acts as a
catalyzer. The objective of the paper is to show how thermal non-equilibrium and
catalysis can jointly influence wall heat flux predictions. In order to study thermal
non-equilibrium effects a coarse-grained State-to-State model for nitrogen is used coupled
with a phenomenological model for catalysis. From the numerical simulations performed,
an important effect on the heat flux has been observed due to the interaction of catalysis
and thermal non-equilibrium at the wall
Comparative cryopreservation study of trochophore larvae from two species of bivalves: Pacific oyster (Crassostrea gigas) and Blue mussel (Mytilus galloprovincialis)
Oysters and mussels are among the most farmed species in aquaculture industry around the world. The aim of this study was to test the toxicity of cryoprotective agents to trochophore larvae from two different species of bivalves and develop an improved cryopreservation protocol to ensure greater efficiency in the development of cryopreserved trochophores (14 h old oyster larvae and 20 h old mussel larvae) to normal D-larvae for future developments of hatchery spat production. The cryopreservation protocol producing the best results for oyster trochophores (60.0 ± 6.7% normal D-larvae) was obtained by holding at 0 °C for 5 min then cooling at 1 °C min(-1) to -10 °C and holding for 5 min before cooling at 0.5 °C to -35 °C, holding 5 min and then plunging into liquid nitrogen (LN), using 10% ethylene glycol. For mussel experiments, no significant differences were found when cooling at 0.5 °C min(-1) or at 1 °C min(-1) for CPA combinations with 10% ethylene glycol and at 0.5 °C min(-1). Using these combinations, around half of trochophores were able to develop to normal D-larvae post-thawing (48.9 ± 7.6% normal D-larvae).Post-print
Conductive nitrides: growth principles, optical and electronic properties, and their perspectives in photonics and plasmonics
The nitrides of most of the group IVb-Vb-VIb transition metals (TiN, ZrN, HfN, VN, NbN, TaN, MoN, WN) constitute the unique category of conductive ceramics. Having substantial electronic conductivity, exceptionally high melting points and covering a wide range of work function values, they were considered for a variety of electronic applications, which include diffusion barriers in metallizations of integrated circuits, Ohmic contacts on compound semiconductors, and thin film resistors, since early eighties. Among them, TiN and ZrN are recently emerging as significant candidates for plasmonic applications. So the possible plasmonic activity of the rest of transition metal nitrides (TMN) emerges as an important open question. In this work, we exhaustively review the experimental and computational (mostly ab initio) works in the literature dealing with the optical properties and electronic structure of TMN spanning over three decades of time and employing all the available growth techniques. We critically evaluate the optical properties of all TMN and we model their predicted plasmonic response. Hence, we provide a solid understanding of the intrinsic (e.g. the valence electron configuration of the constituent metal) and extrinsic (e.g. point defects and microstructure) factors that dictate the plasmonic performance. Based on the reported optical spectra, we evaluate the quality factors for surface plasmon polariton and localized surface plasmon for various TMN and critically compare them to each other. We demonstrate that, indeed TiN and ZrN along with HfN are the most well-performing plasmonic materials in the visible range, while VN and NbN may be viable alternatives for plasmonic devices in the blue, violet and near UV ranges, albeit in expense of increased electronic loss. Furthermore, we consider the alloyed ternary TMN and by critical evaluation and comparison of the reported experimental and computational works, we identify the emerging optimal tunable plasmonic conductors among the immense number of alloying combinations
The massive star population of the Virgo Cluster galaxy NGC 4535
We analyzed the massive star population of the Virgo Cluster galaxy NGC 4535
using archival Hubble Space Telescope Wide Field Planetary Camera 2 images in
filters F555W and F814W, equivalent to Johnson V and Kron-Cousins I. We
performed high precision point spread function fitting photometry of 24353
sources including 3762 candidate blue supergiants, 841 candidate yellow
supergiants and 370 candidate red supergiants. We estimated the ratio of blue
to red supergiants as a decreasing function of galactocentric radius. Using
Modules for Experiments in Stellar Astrophysics isochrones at solar
metallicity, we defined the luminosity function and estimated the star
formation history of the galaxy over the last 60 Myrs. We conducted a
variability search in the V and I filters using three variability indexes: the
median absolute deviation, the interquartile range and the inverse von-Neumann
ratio. This analysis yielded 120 new variable candidates with absolute
magnitudes ranging from M = 4 to 11 mag. We used the MESA
evolutionary tracks at solar metallicity, to classify the variables based on
their absolute magnitude and their position on the color-magnitude diagram.
Among the new candidate variable sources are eight candidate variable red
supergiants, three candidate variable yellow supergiants and one candidate
luminous blue variable, which we suggest for follow-up observations.Comment: Accepted by A&A, 7 pages, 7 Tables, 53 figure
NELIOTA: The wide-field, high-cadence lunar monitoring system at the prime focus of the Kryoneri telescope
We present the technical specifications and first results of the ESA-funded,
lunar monitoring project "NELIOTA" (NEO Lunar Impacts and Optical TrAnsients)
at the National Observatory of Athens, which aims to determine the
size-frequency distribution of small Near-Earth Objects (NEOs) via detection of
impact flashes on the surface of the Moon. For the purposes of this project a
twin camera instrument was specially designed and installed at the 1.2 m
Kryoneri telescope utilizing the fast-frame capabilities of scientific
Complementary Metal-Oxide Semiconductor detectors (sCMOS). The system provides
a wide field-of-view (17.0' 14.4') and simultaneous observations in
two photometric bands (R and I), reaching limiting magnitudes of 18.7 mag in 10
sec in both bands at a 2.5 signal-to-noise level. This makes it a unique
instrument that can be used for the detection of NEO impacts on the Moon, as
well as for any astronomy projects that demand high-cadence multicolor
observations. The wide field-of-view ensures that a large portion of the Moon
is observed, while the simultaneous, high-cadence, monitoring in two
photometric bands makes possible, for the first time, the determination of the
temperatures of the impacts on the Moon's surface and the validation of the
impact flashes from a single site. Considering the varying background level on
the Moon's surface we demonstrate that the NELIOTA system can detect NEO impact
flashes at a 2.5 signal-to-noise level of ~12.4 mag in the I-band and R-band
for observations made at low lunar phases ~0.1. We report 31 NEO impact flashes
detected during the first year of the NELIOTA campaign. The faintest flash was
at 11.24 mag in the R-band (about two magnitudes fainter than ever observed
before) at lunar phase 0.32. Our observations suggest a detection rate of events .Comment: Accepted for publication in A&
Catálogo oficial de la Exposición Nacional de Bellas Artes de 1936
Forma part del projecte: Biblioteca Digital d'Història de l'Art Hispà nic (UAB)Localització de l'original: Biblioteca del Museu Nacional d'Art de CatalunyaCatà leg de l'exposició nacional de belles arts que va tenir lloc l'any 1936 a Madrid. Conté fotografies d'algunes de les obres exposades.Catálogo de la exposición nacional de bellas artes que tuvo lugar en 1936 en Madrid. Contiene fotografÃas de algunas de las obras expuestas.Catalog of the national fine arts exhibition that took place in 1936 in Madrid. It contains photographs of some of the exhibited works
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