69 research outputs found
A chemical model for the atmosphere of hot Jupiters
Our purpose is to release a chemical network, and the associated rate
coefficients, developed for the temperature and pressure range relevant to hot
Jupiters atmospheres. Using this network, we study the vertical atmospheric
composition of the two hot Jupiters (HD209458b, HD189733b) with a model that
includes photolyses and vertical mixing and we produce synthetic spectra. The
chemical scheme is derived from applied combustion models that have been
methodically validated over a range of temperatures and pressures typical of
the atmospheric layers influencing the observations of hot Jupiters. We compare
the predictions obtained from this scheme with equilibrium calculations, with
different schemes available in the literature that contain N-bearing species
and with previously published photochemical models. Compared to other chemical
schemes that were not subjected to the same systematic validation, we find
significant differences whenever non-equilibrium processes take place. The
deviations from the equilibrium, and thus the sensitivity to the network, are
more important for HD189733b, as we assume a cooler atmosphere than for
HD209458b. We found that the abundances of NH3 and HCN can vary by two orders
of magnitude depending on the network, demonstrating the importance of
comprehensive experimental validation. A spectral feature of NH3 at 10.5m
is sensitive to these abundance variations and thus to the chemical scheme. Due
to the influence of the kinetics, we recommend the use of a validated scheme to
model the chemistry of exoplanet atmospheres. Our network is robust for
temperatures within 300-2500K and pressures from 10mbar up to a few hundreds of
bars, for species made of C,H,O,N. It is validated for species up to 2 carbon
atoms and for the main nitrogen species.Comment: 20 pages, 10 figures. Accepted for publication in Astronomy &
Astrophysic
The Headgroup (A)Symmetry Strongly Determines the Aggregation Behavior of Single-Chain Phenylene-Modified Bolalipids and Their Miscibility with Classical Phospholipids
Photodissociation and photoionisation of atoms and molecules of astrophysical interest
Effects of PEGylation on the physicochemical properties and in vivo distribution of organic nanotubes
Wuxiao Ding, Hiroyuki Minamikawa, Naohiro Kameta, Toshimi Shimizu, Mitsutoshi Masuda Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Ibaraki, Japan Abstract: Application of organic nanotubes (ONTs) into drug nanocarriers ultimately requires validation in live animals. For improving the dispersibility in biological media and in vivo distribution, the outer surface of an ONT was functionalized with polyethylene glycol (PEG) via the coassembly of an ONT-forming lipid with 5–20 mol% of a PEG-tethered lipid analogue (PEG-lipid). Firstly, the effect of PEGylation on the psysicochemical properties of ONTs, such as morphology and dispersibility, was investigated. PEGylation of ONTs slightly reduced the average length and effectively prevented the aggregation in phosphate-buffered saline (PBS). The PEGylated ONTs even showed high thermal stability in aqueous dispersion at least up to 95°C. Secondly, differential scanning calorimetry and powder X-ray diffraction indicated that ~10 mol% of PEG-lipid was completely incorporated into the ONTs, while 20 mol% of PEG-lipid encountered a partial phase separation during coassembly. In the heating differential scanning calorimetry runs, the resultant PEGylated ONTs with 5 mol% PEG-lipid showed no sign of phase separation up to 180°C under lyophilized condition, while those with 10 mol% and 20 mol% PEG-lipid showed some phase separation of the PEG-lipid above 120°C. Finally, PEGylation significantly affected the tissue distribution and prolonged the persistence time in the blood in mice. Non-PEGylated ONTs was quickly cleared from the circulation after intravenous infusion and preferentially accumulated in the lung, while PEGylated ONTs was mainly trapped in the liver and could circulate in the blood up to 24 hours. This study provided valuable information of physicochemical properties and the in vivo distribution behavior of PEGylated ONTs for their potential application into drug nanocarriers. Keywords: nanostructure, dispersibility, distributio
Control of Self-assembled Morphology and Molecular Packing of Asymmetric Glycolipids by Association/Dissociation with Poly(thiopheneboronic acid)
Synthesis of (S)-BINOL-Terminated Poly(ethylene glycol) Polyrotaxane Including α-Cyclodextrin
Measuring the Length Distribution of Self-Assembled Lipid Nanotubes by Orientation Control with a High-Frequency Alternating Current Electric Field in Aqueous Solutions
A case of neonatal lupus erythematosus in a very low-birth-weight infant that suffered intraventricular hemorrhage at birth
Supramolecular Self-Assembly into Biofunctional Soft Nanotubes: From Bilayers to Monolayers
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