211 research outputs found
Ligand Effects on the Rate and Mechanism of Solvent Exchange at Rhodium(III) and Iridium(III)
The rate constants and activation parameters for solvent exchange for a series of RhIII and IrIII complexes of the form [M(H2O)6]3+ (M = Rh or Ir) and [Cp*M(S)3]2+ (M = Rh or Ir, and S = H2O, MeCN, or Me2SO) have been determined by NMR spectroscopy as a function of free-solvent concentration, temperature, and pressure, and the mechanisms for the respective exchange processes have been inferred
The importance of episodic accretion for low-mass star formation
A star acquires much of its mass by accreting material from a disc. Accretion
is probably not continuous but episodic. We have developed a method to include
the effects of episodic accretion in simulations of star formation. Episodic
accretion results in bursts of radiative feedback, during which a protostar is
very luminous, and its surrounding disc is heated and stabilised. These bursts
typically last only a few hundred years. In contrast, the lulls between bursts
may last a few thousand years; during these lulls the luminosity of the
protostar is very low, and its disc cools and fragments. Thus, episodic
accretion enables the formation of low-mass stars, brown dwarfs and
planetary-mass objects by disc fragmentation. If episodic accretion is a common
phenomenon among young protostars, then the frequency and duration of accretion
bursts may be critical in determining the low-mass end of the stellar initial
mass function.Comment: To appear in the Astrophysical Journal. Press release available at:
http://www.astro.cf.ac.uk/pub/Dimitrios.Stamatellos/News/News.html Full
resolution paper available at http://stacks.iop.org/0004-637X/730/3
Campaña de comunicación integral “APAVIT, viaja tranquilo”
El presente trabajo desarrolla una campaña de comunicación integral después de la pandemia COVID-19 del año 2020 para APAVIT. El cliente es una organización sin fines de lucro que representa al canal de distribución en el sector turismo en Perú. Las herramientas de comunicación utilizadas se basan principalmente en estrategias de marketing digital como el uso plataformas de redes sociales y páginas web
Lipid-conjugated fluorescent pH sensors for monitoring pH changes in reconstituted membrane systems
Construction and characterization of a bovine BAC library with four genome-equivalent coverage
A bovine artificial chromosome (BAC) library of 105 984 clones has been constructed in the vector pBeloBAC11 and organized in 3-dimension pools and high density membranes for screening by PCR and hybridization. The average insert size, determined after analysis of 388 clones, was estimated at 120 kb corresponding to a four genome coverage. Given the fact that a male was used to construct the library, the probability of finding any given autosomal and X or Y locus is respectively 0.98 and 0.86. The library was screened for 164 microsatellite markers and an average of 3.9 superpools was positive for each PCR system. None of the 50 or so BAC clones analysed by FISH was chimeric. This BAC library increases the international genome coverage for cattle to around 28 genome equivalents and extends the coverage of the ruminant genomes available at the Inra resource center to 15 genome equivalents
Accuracy of core mass estimates in simulated observations of dust emission
We study the reliability of mass estimates obtained for molecular cloud cores
using sub-millimetre and infrared dust emission. We use magnetohydrodynamic
simulations and radiative transfer to produce synthetic observations with
spatial resolution and noise levels typical of Herschel surveys. We estimate
dust colour temperatures using different pairs of intensities, calculate column
densities and compare the estimated masses with the true values. We compare
these results to the case when all five Herschel wavelengths are available. We
investigate the effects of spatial variations of dust properties and the
influence of embedded heating sources. Wrong assumptions of dust opacity and
its spectral index beta can cause significant systematic errors in mass
estimates. These are mainly multiplicative and leave the slope of the mass
spectrum intact, unless cores with very high optical depth are included.
Temperature variations bias colour temperature estimates and, in quiescent
cores with optical depths higher than for normal stable cores, masses can be
underestimated by up to one order of magnitude. When heated by internal
radiation sources the observations recover the true mass spectra. The shape,
although not the position, of the mass spectrum is reliable against
observational errors and biases introduced in the analysis. This changes only
if the cores have optical depths much higher than expected for basic
hydrostatic equilibrium conditions. Observations underestimate the value of
beta whenever there are temperature variations along the line of sight. A bias
can also be observed when the true beta varies with wavelength. Internal
heating sources produce an inverse correlation between colour temperature and
beta that may be difficult to separate from any intrinsic beta(T) relation of
the dust grains. This suggests caution when interpreting the observed mass
spectra and the spectral indices.Comment: Revised version, 17 pages, 17 figures, submitted to A&
Impact of a long-lived anticyclonic mesoscale eddy on seawater anomalies in the northeastern tropical Pacific Ocean: a composite analysis from hydrographic measurements, sea level altimetry data, and reanalysis model products
Using observational data, satellite altimeters, and reanalysis model products, we have investigated eddy-induced seawater anomalies and heat and salt transport in the northeastern tropical Pacific Ocean. An eddy detection algorithm (EDA) was used to identify eddy formation at the Mexican Tehuantepec Gulf (TT) in July 2018 during an unusually strong summer wind event. The eddy separated from the coast with a mean translation velocity of 11 cm s−1 and a mean radius of 115 km and traveled 2050–2400 km westwards off the Central American coast, where it was followed at approx 114∘ W and 11∘ N for oceanographic observation between April and May 2019. The in situ observations show that the major eddy impacts are restricted to the upper 300 m of the water column and are traceable down to 1500 m water depth. In the eddy core at 92 m water depth an extreme positive temperature anomaly of 8.2 ∘C, a negative salinity anomaly of −0.78 psu, a positive fluorescence anomaly of +0.8 mg m−3, and a positive dissolved oxygen concentration anomaly of 137 µmol kg−1 are observed. Compared with annual climatological averages in 2018, the water trapped within the eddy is estimated to transport an average positive westward zonal heat anomaly of 85×1012 W and an average westward negative salt anomaly of kg s−1. The heat transport is the equivalent of 1 % of the total annual zonal eddy-induced heat transport at this latitude in the Pacific Ocean. Understanding the dynamics of long-lived mesoscale eddies that may reach the seafloor in this region of the Pacific Ocean is especially important in light of potential deep-sea mining activities that are being targeted on this area
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