2,306 research outputs found
Observations of Sy2 galaxy NGC 3281 by XMM-Newton and INTEGRAL satellites
We present here the results of our analysis of X-ray properties of Seyfert 2
galaxy NGC 3281, based on the observational data obtained by XMM-Newton and
INTEGRAL within the energy ranges 0.2-12 keV and 20-150 keV, respectively. The
XMM-Newton spectrum of this object is presented for the first time. We show
that fitting the X-ray spectrum of this galaxy with models based on the
reflection from the disc with infinite column density yields non-physical
results. More appropriate fit takes into account both transmitted and reflected
emission, passed through a gas-dusty torus-like structure. Keeping this in
mind, to model the inhomogeneous clumpy torus, we used the MYTorus model.
Hence, we propose that the torus of NGC 3281 is not continuous structure, but
it consists of separate clouds, which is in a good agreement with the results
of near-IR observations. Using this assumption, we found that the torus
inclination angle and the hydrogen column density are 66.98^{+2.63}_{-1.34}
degrees and 2.08^{+0.35}_{-0.18}x10^{24} cm^{-2}, respectively. Also, the
emission of the hot diffuse gas with temperature ~590 eV and warm absorption
were detected.Comment: 8 pages, 5 figures, 2 tables, accepted for publication in Advances in
Astronomy and Space Physic
Hexakis(dimethylformamide)bis(hexaphenylcyclohexasiloxanehexaolato)hexacopper(II) Dimethylformamide Solvate
The sandwich-like title complex, hexakis(dimethylformamide)-1O,2O,3O,4O,5O,6O-bis[2,4,6,8,10,12-hexaphenylsiloxane-2,4,6,8,10,12-hexaolato(6-)-1:22O1,2:32O2,3:42O3,- 4:52O4,5:62O5,1:62O6]hexacopper(II) tetrakis(dimethylformamide) solvate, [Cu6(C3H7NO)6{(C6H5)6O12Si6}2].4C3H7NO, is comprised of two regular crown-shaped macrocyclic hexadentate organosiloxanolate ligands chelating a flat Cu6 hexagon, as in the ethanol-solvated analogue investigated previously. The title complex has a more distorted shape than the trigonal ethanol-solvated analogue, being slightly side-oblated, but still contains a large empty inner channel accessible by small molecules (the diameter of the free cross-section being about 2.5 Å). Each CuII ion has square-pyramidal coordination with four basal siloxanolate O atoms and an apical dimethylformamide (DMFA) molecule (coordinated through its carbonyl group). The average bond lengths are: Cu-O(Si) 1.964 (11) Å and Cu-O(DMFA) 2.215 (10) Å. The structure contains four additional DMFA molecules per complex unit, linked by weak C-HO hydrogen bonds. Unexpectedly, the C=O bond length is longer [1.248 (10) and 1.255 (9) Å] in the uncoordinated DMFA molecules than in the coordinated [1.214-1.227 (7) Å]
On the classification of conditionally integrable evolution systems in (1+1) dimensions
We generalize earlier results of Fokas and Liu and find all locally analytic
(1+1)-dimensional evolution equations of order that admit an -shock type
solution with .
To this end we develop a refinement of the technique from our earlier work
(A. Sergyeyev, J. Phys. A: Math. Gen, 35 (2002), 7653--7660), where we
completely characterized all (1+1)-dimensional evolution systems
\bi{u}_t=\bi{F}(x,t,\bi{u},\p\bi{u}/\p x,...,\p^n\bi{u}/\p x^n) that are
conditionally invariant under a given generalized (Lie--B\"acklund) vector
field \bi{Q}(x,t,\bi{u},\p\bi{u}/\p x,...,\p^k\bi{u}/\p x^k)\p/\p\bi{u} under
the assumption that the system of ODEs \bi{Q}=0 is totally nondegenerate.
Every such conditionally invariant evolution system admits a reduction to a
system of ODEs in , thus being a nonlinear counterpart to quasi-exactly
solvable models in quantum mechanics.
Keywords: Exact solutions, nonlinear evolution equations, conditional
integrability, generalized symmetries, reduction, generalized conditional
symmetries
MSC 2000: 35A30, 35G25, 81U15, 35N10, 37K35, 58J70, 58J72, 34A34Comment: 8 pages, LaTeX 2e, now uses hyperre
On separable Schr\"odinger equations
We classify (1+3)-dimensional Schr\"odinger equations for a particle
interacting with the electromagnetic field that are solvable by the method of
separation of variables. As a result, we get eleven classes of the
electromagnetic vector potentials of the electromagnetic field , providing separability of the
corresponding Schr\"odinger equations. It is established, in particular, that
the necessary condition for the Schr\"odinger equation to be separable is that
the magnetic field must be independent of the spatial variables. Next, we prove
that any Schr\"odinger equation admitting variable separation into second-order
ordinary differential equations can be reduced to one of the eleven separable
Schr\"odinger equations mentioned above and carry out variable separation in
the latter. Furthermore, we apply the results obtained for separating variables
in the Hamilton-Jacobi equation.Comment: 30 pages, LaTe
Real or not? Identifying untrustworthy news websites using third-party partnerships
Untrustworthy content such as fake news and clickbait have become a pervasive problem on the Internet, causing significant socio-political problems around the world. Identifying untrustworthy content is a crucial step in countering them. The current best-practices for identification involve content analysis and arduous fact-checking of the content. To complement content analysis, we propose examining websites? third-parties to identify their trustworthiness. Websites utilize third-parties, also known as their digital supply chains, to create and present content and help the website function. Third-parties are an important indication of a website?s business model. Similar websites exhibit similarities in the third-parties they use. Using this perspective, we use machine learning and heuristic methods to discern similarities and dissimilarities in third-party usage, which we use to predict trustworthiness of websites. We demonstrate the effectiveness and robustness of our approach in predicting trustworthiness of websites from a database of News, Fake News, and Clickbait websites. Our approach can be easily and cost-effectively implemented to reinforce current identification methods
Formation of singularities on the surface of a liquid metal in a strong electric field
The nonlinear dynamics of the free surface of an ideal conducting liquid in a
strong external electric field is studied. It is establish that the equations
of motion for such a liquid can be solved in the approximation in which the
surface deviates from a plane by small angles. This makes it possible to show
that on an initially smooth surface for almost any initial conditions points
with an infinite curvature corresponding to branch points of the root type can
form in a finite time.Comment: 14 page
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