289 research outputs found
A Frame Work for the Error Analysis of Discontinuous Finite Element Methods for Elliptic Optimal Control Problems and Applications to IP methods
In this article, an abstract framework for the error analysis of
discontinuous Galerkin methods for control constrained optimal control problems
is developed. The analysis establishes the best approximation result from a
priori analysis point of view and delivers reliable and efficient a posteriori
error estimators. The results are applicable to a variety of problems just
under the minimal regularity possessed by the well-posed ness of the problem.
Subsequently, applications of interior penalty methods for a boundary
control problem as well as a distributed control problem governed by the
biharmonic equation subject to simply supported boundary conditions are
discussed through the abstract analysis. Numerical experiments illustrate the
theoretical findings. Finally, we also discuss the variational discontinuous
discretization method (without discretizing the control) and its corresponding
error estimates.Comment: 23 pages, 5 figures, 1 tabl
3-(2-Amino-1-methyl-4-oxo-4,5-dihydro-1H-imidazol-5-yl)-3-hydroxy-1-phenylindolin-2-one ethanol solvate
In the title compound, C18H16N4O3·C2H5OH, molecules are linked into chains by a series of intermolecular N—H⋯O, N—H⋯N and O—H⋯O hydrogen bonds which stabilize the crystal structure. The indole and creatinine units make a dihedral angle of 56.45 (4)°. The title compound has two chiral centres. The crystal structure indicates the compound is racemic (RR and SS)
3-(2-Amino-1-methyl-4-oxo-4,5-dihydro-1H-imidazol-5-yl)-5-fluoro-3-hydroxy-1-methylindolin-2-one methanol hemisolvate
In the title compound, C13H13FN4O3·0.5CH3OH, molecules are packed in the crystal structure by a series of O—H⋯N, N—H⋯O, N—H⋯F and O—H⋯O intermolecular hydrogen bonds. The indole and creatinine units make a dihedral angle of 60.80 (4)°
Near-Infrared Spectroscopy of Carbon-Enhanced Metal-Poor Stars. I. A SOAR/OSIRIS Pilot Study
We report on an abundance analysis for a pilot study of seven Carbon-Enhanced
Metal-Poor (CEMP) stars, based on medium-resolution optical and near-infrared
spectroscopy. The optical spectra are used to estimate [Fe/H], [C/Fe], [N/Fe],
and [Ba/Fe] for our program stars. The near-infrared spectra, obtained during a
limited early science run with the new SOAR 4.1m telescope and the Ohio State
Infrared Imager and Spectrograph (OSIRIS), are used to obtain estimates of
[O/Fe] and 12C/13C. The chemical abundances of CEMP stars are of importance for
understanding the origin of CNO in the early Galaxy, as well as for placing
constraints on the operation of the astrophysical s-process in very
low-metallicity Asymptotic Giant Branch (AGB) stars.
This pilot study includes a few stars with previously measured [Fe/H],
[C/Fe], [N/Fe],[O/Fe], 12C/13C, and [Ba/Fe], based on high-resolution optical
spectra obtained with large-aperture telescopes. Our analysis demonstrates that
we are able to achieve reasonably accurate determinations of these quantities
for CEMP stars from moderate-resolution optical and near-infrared spectra. This
opens the pathway for the study of significantly larger samples of CEMP stars
in the near future. Furthermore, the ability to measure [Ba/Fe] for (at least
the cooler) CEMP stars should enable one to separate stars that are likely to
be associated with s-process enhancements (the CEMP-s stars) from those that do
not exhibit neutron-capture enhancements (the CEMP-no stars).Comment: 27 pages, including 5 tables, 6 figures, accepted for publication in
The Astronomical Journa
(Z)-Methyl 4-({3-[(2,5-dioxoimidazolidin-4-ylidene)methyl]-1H-indol-1-yl}methyl)benzoate
In the title compound, C21H17N3O4, pairs of molecules form a planar[maximum deviation 0.0566 (9) Å] centrosymmetric imidazole dimer via two N—H⋯O hydrogen bonds. These dimeric units are linked by further N—H⋯O hydrogen bonds between the ester carbonyl group and the imidazolidine ring, formiing chains parallel to the c-axis direction. In addition, there are π–π stacking interactions between the planar imidazole pairs, with an interplanar spacing of 3.301 (2) Å. There is a double bond with Z geometry connecting the imidazolidine and indole units
Synthesis and In Vitro Screening of Novel Heterocyclic Compounds as Potential Breast Cancer Agents
Decoding the compositions of four bright -process-enhanced stars
There has been a concerted effort in recent years to identify the
astrophysical sites of the -process that can operate early in the Galaxy.
The discovery of many -process-enhanced (RPE) stars (especially by the
-process Alliance collaboration) has significantly accelerated this effort.
However, only limited data exist on the detailed elemental abundances covering
the primary neutron-capture peaks. Subtle differences in the structure of the
-process pattern, such as the relative abundances of elements in the third
peak, in particular, are expected to constrain the -process sites further.
Here, we present a detailed elemental-abundance analysis of four bright RPE
stars selected from the HESP-GOMPA survey. Observations were carried out with
the 10-m class telescope Gran Telescopio Canarias (GTC), Spain. The high
spectral signal-to-noise ratios obtained allow us to derive abundances for 20
neutron-capture elements, including the third -process peak element osmium
(Os). We detect thorium (Th) in two stars, which we use to estimate their ages.
We discuss the metallicity evolution of Mg, Sr, Ba, Eu, Os, and Th in -II
and -I stars, based on a compilation of RPE stars from the literature. The
strontium (Sr) abundance trend with respect to europium (Eu) suggests the need
for an additional production site for Sr (similar to several earlier studies);
this requirement could be milder for yttrium (Y) and zirconium (Zr). We also
show that there could be some time delay between -II and -I star
formation, based on the Mg/Th abundance ratios.Comment: 33 pages, 22 figures, Accepted for publication in MNRA
(E,E)-1-Methyl-2,6-distyrylpyridinium iodide
In the title compound, C22H20N+·I−, the dihedral angles between the central pyridine ring and two outer benzene rings are 15.30 (10) and 11.82 (11)°. There are intermolecular π–π stacking interactions between the nearest phenyl ring over an inversion-related pyridyl ring, the shortest centroid–centroid distance being 3.672 (3) Å. The crystal structure of the compound indicates the 2,6-distyryl substituents have an E configuration
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