452 research outputs found
Évolution de la qualité de vie après un traumatisme crânien par accident de la route : un suivi à cinq ans de la cohorte ESPARR
Continua com: Info Ajuntament+Sostenible : notícies de l'Ajuntament+sostenibl
Ultrafast excited state dynamics of silver ion-mediated cytosine–cytosine base pairs in metallo-DNA
The following article appeared in The Journal of Chemical Physics 153.10 (2020): 105104 and may be found at ttps://doi.org/10.1063/5.0020463To better understand the nexus between structure and photophysics in metallo-DNA assemblies, the parallel-stranded duplex formed by the
all-cytosine oligonucleotide, dC20, and silver nitrate was studied by circular dichroism (CD), femtosecond transient absorption spectroscopy,
and time-dependent-density functional theory calculations. Silver(I) ions mediate Cytosine–Cytosine (CC) base pairs by coordinating to the
N3 atoms of two cytosines. Although these silver(I) mediated CC base pairs resemble the proton-mediated CC base pairs found in i-motif
DNA at first glance, a comparison of experimental and calculated CD spectra reveals that silver ion-mediated i-motif structures do not form.
Instead, the parallel-stranded duplex formed between dC20 and silver ions is proposed to contain consecutive silver-mediated base pairs
with high propeller twist-like ones seen in a recent crystal structure of an emissive, DNA-templated silver cluster. Femtosecond transient
absorption measurements with broadband probing from the near UV to the near IR reveal an unusually long-lived (>10 ns) excited state in
the dC20 silver ion complex that is not seen in dC20 in single-stranded or i-motif forms. This state is also absent in a concentrated solution of
cytosine–silver ion complexes that are thought to assemble into planar ribbons or sheets that lack stacked silver(I) mediated CC base pairs.
The large propeller twist angle present in metal-mediated base pairs may promote the formation of long-lived charged separated or triplet
states in this metallo-DNAThe work at The Ohio State University was supported by a
grant from the U.S. National Science Foundation (Grant No. CHE1800471). L.M.-F. thanks the MINECO project (No. CTQ2016-
76061-P) for financial support and the Centro de Computación
Científica, CCC-UAM, for generous allocation of computational
time. The authors declare no competing financial interes
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Comparative global energy budgets for the climates of terrestrial and gas giant planets
The weather and climate on Earth are generally determined by the amount and distribution of incoming solar radiation. This must be balanced in equilibrium by the emission of thermal radiation from the surface and atmosphere, but the precise routes by which incoming energy is transferred from the surface and within the atmosphere and back out to space are important features that characterize the current climate. This has been analysed in the past by several groups over the years, based on combinations of numerical model simulations and direct observations of the Earth’s climate system. The results are often presented in schematic form[1] to show the main routes for the transfer of energy into, out of and within the climate system. Although relatively simple in concept, such diagrams convey a great deal of information about the climate system in a compact form, and are especially valuable pedagogically at school and undergraduate level.
Such an approach has not so far been adopted in any systematic way for other planets of the Solar System, let alone beyond, although quite detailed climate models of several planets are now available, constrained by many new observations and measurements. Here we analyse the global transfers of energy within the climate systems of a range of terrestrial planets within the Solar System, including Mars, Titan and Venus, as simulated by relatively comprehensive numerical circulation models of such planets. These results will then be presented in schematic form for comparison with the ‘classical’ global energy budget analysis of Trenberth et al.[1] for the Earth, highlighting the important similarities and differences. We also consider how to extend this approach towards other Solar System and extra-solar planets, including Jupiter, Saturn and hot Jupiter exoplanets.
[1] Trenberth, K. E., Fasullo, J. T. and Kiehl, J.: Earth’s global energy budget, BAMS, Vol. 90, 311-323, 2009
Order parameter configurations in the Lifshitz-type incommensurate ferroelectric thin films
The Dzialoshinskii model of periodic and helicoidal structures has been
analyzed without neglecting of the amplitude function oscillations. The
amplitude function oscillations are shown to be important for understanding of
the nature of the phase function. Analytic consideration is carried out in the
limit of small anisotropy (neglecting the cosine term in the Hamiltonian).
Surprisingly, the phase jumps survive even in the limit of the vanishing
anisotropy
Building solids inside nano-space: from confined amorphous through confined solvate to confined ‘metastable’ polymorph
The nanocrystallisation of complex molecules inside mesoporous hosts and control over the resulting structure is a significant challenge. To date the largest organic molecule crystallised inside the nano-pores is a known pharmaceutical intermediate – ROY (259.3 g mol1). In this work we demonstrate smart manipulation of the phase of a larger confined pharmaceutical – indomethacin (IMC, 357.8 g mol1), a substance with known conformational flexibility and complex polymorphic behaviour. We show the detailed structural analysis and the control of solid state transformations of encapsulated molecules inside the pores of mesoscopic cellular foam (MCF, pore size ca. 29 nm) and controlled pore glass (CPG, pore size ca. 55 nm). Starting from confined amorphous IMC we drive crystallisation into a confined methanol solvate, which upon vacuum drying leads to the stabilised rare form V of IMC inside the MCF host. In contrast to the pure form, encapsulated form V does not transform into a more stable polymorph upon heating. The size of the constraining pores and the drug concentration within the pores determine whether the amorphous state of the drug is stabilised or it recrystallises into confined nanocrystals. The work presents, in a critical manner, an application of complementary techniques (DSC, PXRD, solid-state NMR, N2 adsorption) to confirm unambiguously the phase transitions under confinement and offers a comprehensive strategy towards the formation and control of nano-crystalline encapsulated organic solids
First direct detection of an exoplanet by optical interferometry; Astrometry and K-band spectroscopy of HR8799 e
To date, infrared interferometry at best achieved contrast ratios of a few
times on bright targets. GRAVITY, with its dual-field mode, is now
capable of high contrast observations, enabling the direct observation of
exoplanets. We demonstrate the technique on HR8799, a young planetary system
composed of four known giant exoplanets. We used the GRAVITY fringe tracker to
lock the fringes on the central star, and integrated off-axis on the HR8799e
planet situated at 390 mas from the star. Data reduction included
post-processing to remove the flux leaking from the central star and to extract
the coherent flux of the planet. The inferred K band spectrum of the planet has
a spectral resolution of 500. We also derive the astrometric position of the
planet relative to the star with a precision on the order of 100as. The
GRAVITY astrometric measurement disfavors perfectly coplanar stable orbital
solutions. A small adjustment of a few degrees to the orbital inclination of HR
8799 e can resolve the tension, implying that the orbits are close to, but not
strictly coplanar. The spectrum, with a signal-to-noise ratio of
per spectral channel, is compatible with a late-type L brown dwarf. Using
Exo-REM synthetic spectra, we derive a temperature of \,K and a
surface gravity of cm/s. This corresponds to a radius
of and a mass of , which is an independent confirmation of mass estimates from evolutionary
models. Our results demonstrate the power of interferometry for the direct
detection and spectroscopic study of exoplanets at close angular separations
from their stars.Comment: published in A&
A survey of exoplanet phase curves with Ariel
The ESA-Ariel mission will include a tier dedicated to exoplanet phase curves corresponding to ∼ 10 % of the science time. We present here the current observing strategy for studying exoplanet phase curves with Ariel. We define science questions, requirements and a list of potential targets. We also estimate the precision of phase curve reconstruction and atmospheric retrieval using simulated phase curves. Based on this work, we found that full-orbit phase variations for 35-40 exoplanets could be observed during the 3.5-yr mission. This statistical sample would provide key constraints on atmospheric dynamics, composition, thermal structure and clouds of warm exoplanets, complementary to the scientific yield from spectroscopic transits/eclipses measurements
Peering into the Young Planetary System AB Pic. Atmosphere, Orbit, Obliquity & Second Planetary Candidate
We aim to revisit the system AB Pic which has a known companion at the
exoplanet/ brown-dwarf boundary. We based this study on a rich set of
observations to investigate the companion's orbit and atmosphere. We composed a
spectrum of AB Pic b merging archival VLT/SINFONI K-band data, with published
spectra at J and H-band (SINFONI) and Lp-band (Magellan-AO), and photometric
measurements (HST and Spitzer). We modeled the spectrum with ForMoSA, based on
two atmospheric models: ExoREM and BT-SETTL13. We determined the orbital
properties of b fitting the astrometric measurements from NaCo (2003 and 2004)
and SPHERE (2015). The orbital solutions favor a semi-major axis of 190au
viewed edge-on. With Exo-REM, we derive a T of 170050K and surface
gravity of 4.50.3dex, consistent with previous works, and we report for
the first time a C/O ratio of 0.580.08 (solar). The posteriors are
sensitive to the wavelength interval and the family of models used. Given the
2.1hr rotation period and our vsin(i) of 73km/s, we estimate for the
first time the true obliquity to be 45 or 135deg, indicating a
significant misalignment between the planet's spin and orbit orientations.
Finally, the existence of a proper motion anomaly between the Hipparcos and
Gaia eDR3 compared to our SPHERE detection limits and adapted radial velocity
limits indicate the existence of a 6M inner planet orbiting from
2 to 10au (40-200mas). The possible existence of an inner companion, together
with the likely miss-alignment of the spin axis orientation, strongly favor a
formation path by gravitational instability or core accretion within a disk
closer inside followed by dynamical interactions. Confirmation and
characterization of planet c and access to a broader wavelength coverage for
planet b will be essential to probe the uncertainties associated with the
parameters.Comment: 17 pages, 13 Figures, 6 Tables. Accepted for publication in A&A (31
of October
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