2,508 research outputs found
Contact process on a Voronoi triangulation
We study the continuous absorbing-state phase transition in the contact
process on the Voronoi-Delaunay lattice. The Voronoi construction is a natural
way to introduce quenched coordination disorder in lattice models. We simulate
the disordered system using the quasistationary simulation method and determine
its critical exponents and moment ratios. Our results suggest that the critical
behavior of the disordered system is unchanged with respect to that on a
regular lattice, i.e., that of directed percolation
When Politicians Talk About Politics: Identifying Political Tweets of Brazilian Congressmen
Since June 2013, when Brazil faced the largest and most significant mass
protests in a generation, a political crisis is in course. In midst of this
crisis, Brazilian politicians use social media to communicate with the
electorate in order to retain or to grow their political capital. The problem
is that many controversial topics are in course and deputies may prefer to
avoid such themes in their messages. To characterize this behavior, we propose
a method to accurately identify political and non-political tweets
independently of the deputy who posted it and of the time it was posted.
Moreover, we collected tweets of all congressmen who were active on Twitter and
worked in the Brazilian parliament from October 2013 to October 2017. To
evaluate our method, we used word clouds and a topic model to identify the main
political and non-political latent topics in parliamentarian tweets. Both
results indicate that our proposal is able to accurately distinguish political
from non-political tweets. Moreover, our analyses revealed a striking fact:
more than half of the messages posted by Brazilian deputies are non-political.Comment: 4 pages, 7 figures, 2 table
Relativistic quantum dynamics of scalar bosons under a full vector Coulomb interaction
The relativistic quantum dynamics of scalar bosons in the background of a
full vector coupling (minimal plus nonminimal vector couplings) is explored in
the context of the Duffin-Kemmer-Petiau formalism. The Coulomb phase shift is
determined for a general mixing of couplings and it is shown that the space
component of the nonminimal coupling is a {\it sine qua non} condition for the
exact closed-form scattering amplitude. It follows that the Rutherford cross
section vanishes in the absence of the time component of the minimal coupling.
Bound-state solutions obtained from the poles of the partial scattering
amplitude show that the time component of the minimal coupling plays an
essential role. The bound-state solutions depend on the nonminimal coupling and
the spectrum consists of particles or antiparticles depending on the sign of
the time component of the minimal coupling without chance for pair production
even in the presence of strong couplings. It is also shown that an accidental
degeneracy appears for a particular mixing of couplings.Comment: 8 pages, 1 table. arXiv admin note: text overlap with arXiv:1403.603
A survey of cultural aspects in Human Computer Interaction Research
Considering culture in human computer interaction research is an important issue since culture has a strong impact on many cognitive and affective processes, closed related to the design and evaluation of interactive systems. Also, people with different cultural backgrounds develop alternative interpretations and strategies and do not value their environment in the same way, and this reflects in their interactions and satisfaction with interactive technologies. In this survey we summarize some concepts of the cultural aspects related to human computer interaction research. After we discuss how HCI practices could address these cultural issues. Our intention is to establish background and some basic concepts for helping researchers incorporating cultural issues in their design and evaluation processes
Bis(tetraphenylphosphonium) tris[N-(methylsulfonyl)dithiocarbimato(2−)-κ2 S,S′]stannate(IV)
In the title complex, (C24H20P)2[Sn(C2H3NO2S3)3], the SnIV atom is coordinated by three N-(methylsulfonyl)dithiocarbimate bidentate ligands through the anionic S atoms in a slightly distorted octahedral coordination geometry. There is one half-molecule in the asymmetric unit; the complex is located on a crystallographic twofold rotation axis passing through the cation and bisecting one of the (non-symmetric) ligands, which appears thus disordered over two sites of equal occupancy. In the crystal structure, weak intermolecular C—H⋯O and C—H⋯S interactions contribute to the packing stabilization
Giant Amazonian fish pirarucu (Arapaima gigas): Its viscera as a source of thermostable trypsin
A trypsin was purified from pyloric caeca of pirarucu (Arapaima gigas). the effect of metal ions and protease inhibitors on its activity and its physicochemical and kinetic properties, as well its N-terminal sequence, were determined. A single band (28.0 kDa) was observed by SDS-PAGE. Optimum pH and temperature were 9.0 and 65 degrees C, respectively. the enzyme was stable after incubation for 30 min in a wide pH range (6.0-11.5) and at 55 degrees C. the kinetic parameters K-m, k(cat) and k(cat)/K-m were 0.47 +/- 0.042 mM, 1.33 s(-1) and 2.82 s(-1) mM(-1), respectively, using BApNA as substrate. This activity was shown to be very sensitive to some metal ions, such as Fe2+, Hg2+, Zn2+, Al3+, Pb2+, and was highly inhibited by trypsin inhibitors. the trypsin N-terminal sequence IVGGYECPRNSVPYQ was found. the features of this alkaline peptidase suggest that it may have potential for industrial applications (e.g. food and detergent industries). (C) 2012 Elsevier B.V. All rights reserved.Financiadora de Estudos e Projetos (FINEP/RECAR-CINE)Ministerio da Aquicultura e Pesca (MAP)Empresa brasileira de pesquisa agropecuaria (Embrapa)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundacao de Apoio a Ciencia e Tecnologia do Estado de Pernambuco (FACEPE)Petroleo do Brasil S/A (PETROBRAS)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Univ Fed Pernambuco, Lab Enzimol LABENZ, Dept Bioquim, BR-50670420 Recife, PE, BrazilUniv Fed Pernambuco, LIKA, BR-50670420 Recife, PE, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Biofis, BR-04044020 São Paulo, BrazilUniversidade Federal de São Paulo, Escola Paulista Med, Dept Biofis, BR-04044020 São Paulo, BrazilWeb of Scienc
Bis(tetraphenylphosphonium) bis[N-(phenylsulfonyl)dithiocarbimato-κ2 S,S′]platinate(II) monohydrate
The asymmetric unit of the title compound, (C24H20P)2[Pt(C7H5NO2S3)2]·H2O, consists of two tetraphenylphosphonium cations, two half bis[N-(phenylsulfonyl)dithiocarbimato]platinate(II) dianions and one water molecule. The anions are completed by crystallographic inversion symmetry associated with the central PtII ion. The PtII ion is doubly S,S′-chelated by two symmetry-related phenylsulfonyldithiocarbimate ligands, forming a slightly distorted square-planar configuration. Besides the electrostatic attraction between oppositely charged ions in the crystal packing, intramolecular C—H⋯O and several intermolecular C—H⋯O, C—H⋯N and O—H⋯O hydrogen-bonding interactions between the cations, anions and water molecules are observed
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