1,179 research outputs found
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Synthesis of iso-C-nucleoside analogues from 1-(methyl 2-O-benzyl-4,6-O- benzylidene-3-deoxy-α-D-altropyranosid-3-yl)but-3-yn-2-ones
1-(Methyl 2-O-benzyl-4,6-O-benzylidene-3-deoxy-α-D-altropyranosid-3- yl)but-3-yn-2-one (3a) reacted with 3-amino-1H-1,2,4-triazole and 5-aminopyrazole-4-carboxylic acid derivatives in the presence of base to furnish the triazolo[1,5-a]pyrimidine (5) and the pyrazolo[1,5-a]pyrimidines (8a-d), respectively. Treatment of 1-(methyl 2-O-benzyl-4,6-O-benzylidene-3-deoxy- α-D-altropyranosid-3-yl)-4-phenyl-but-3-yn-2-one (3b) with cyanacetamide, 2-cyano-N-(4-methoxyphenyl)acetamide und N-aryl-3-oxo-butyramides afforded the substituted nicotinonitriles (11a-d). Furthermore, reaction of 3b with 2-benzimidazolyl-acetonitrile yielded the benz[4,5]imidazo[1,2-a]pyridine-4- carbonitrile (13). Deprotection of 8d in two steps afforded the 2-amino-N-benzyl-5-(methyl 3-deoxy-α-D-altropyranosid-3-yl-methyl) pyrazolo[1,5-a]pyrimidine-3-carboxamide (10). Compounds 5 and 11d were treated with AcOH/H2O to furnish the 5-(methyl 2-O-benzyl-3-deoxy-α-D- altropyranosid-3-yl-methyl)[1,2,4]triazolo[1,5-a]pyrimidine (6) and the 3-acetyl-1,2-dihydro-1-(4-methoxyphenyl)-6-(methyl 2-O-benzyl-3-deoxy-α-D- altropyranosid-3-yl-methyl)-4-phenylpyridin-2-one (12), respectively
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Corrigendum: a new strain collection for improved expression of outer membrane proteins
Autonomous on-board data processing and instrument calibration software for the SO/PHI
The extension of on-board data processing capabilities is an attractive
option to reduce telemetry for scientific instruments on deep space missions.
The challenges that this presents, however, require a comprehensive software
system, which operates on the limited resources a data processing unit in space
allows. We implemented such a system for the Polarimetric and Helioseismic
Imager (PHI) on-board the Solar Orbiter (SO) spacecraft. It ensures autonomous
operation to handle long command-response times, easy changing of the processes
after new lessons have been learned and meticulous book-keeping of all
operations to ensure scientific accuracy. This contribution presents the
requirements and main aspects of the software implementation, followed by an
example of a task implemented in the software frame, and results from running
it on SO/PHI. The presented example shows that the different parts of the
software framework work well together, and that the system processes data as we
expect. The flexibility of the framework makes it possible to use it as a
baseline for future applications with similar needs and limitations as SO/PHI.Comment: Conference: SPIE Astronomical Telescopes + Instrumentatio, Software
and Cyberinfrastructure for Astronomy
The First Dynamical Mass Measurement in the HR 8799 System
HR 8799 hosts four directly imaged giant planets, but none has a mass
measured from first principles. We present the first dynamical mass measurement
in this planetary system, finding that the innermost planet HR~8799~e has a
mass of . This mass results from combining
the well-characterized orbits of all four planets with a new astrometric
acceleration detection (5) from the Gaia EDR3 version of the
Hipparcos-Gaia Catalog of Accelerations. We find with 95\% confidence that
HR~8799~e is below , the deuterium-fusing mass limit. We
derive a hot-start cooling age of \,Myr for HR~8799~e that
agrees well with its hypothesized membership in the Columba association but is
also consistent with an alternative suggested membership in the
~Pictoris moving group. We exclude the presence of any additional
5- planets interior to HR~8799~e with semi-major axes
between 3-16\,au. We provide proper motion anomalies and a matrix
equation to solve for the mass of any of the planets of HR~8799 using only mass
ratios between the planets.Comment: Accepted to ApJ Letter
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