166,828 research outputs found
Measurements of soft QCD and double parton scattering at LHCb
Soft QCD and double parton scattering are of great interest in high energy
physics. They are both actively studied at the LHCb experiment. The measurement
of the central exclusive production of and mesons in
collisions at is presented. The result shows
good agreement with the theoretical predictions. The measurement of the
pair production cross-section in collisions at is reported. The differential cross-sections as functions of
various kinematic variables are compared to the theoretical predictions, and
show significant evidence of double parton scattering contribution.Comment: 6 pages, 7 figures, Proceedings of the Fifth Annual Conference on
Large Hadron Collider Physics, Shanghai Jiao Tong University, Shanghai,
China, May 15-20, 201
2D-Delocalized vs Confined Diradicals
Resumen de la comunicación oral seleccionadaDiradicals are beautiful chemical objects where the more basic and intricate aspects of the chemical bonding are revealed.1 Not this being important enough, nowadays, diradical-based substrates are becoming very appealing for new organic electronic applications. We focus here in conjugated organic diradicals formed by competition between non-aromatic quinoidal structures and their canonical aromatic forms. How this quinoidal(closed-shell)-vs-aromatic(open-shell) energetic balance producing the diradical is affected by several situations has been our objective in the last few years.2 Now, we focusses on how the properties of diradicals are influenced when several diradical canonical forms are available in such a way that create a 2D (i.e., bidimensional) electron delocalization surface in which the diradical substructures are in cross-conjugation mode producing the curious effect of diradical confinement.3
Herein, the diradical molecular properties of compound 1 in Figure 1 will be discussed in connection with 2D delocalization, cross-conjugation and surface confinement.
1. Rajca, A., Chem. Rev., 1994, 94, 871; Abe, M., Chem. Rev. 2013, 113, 7011.
2. Zeng, Z.; X. Shi, L.; Chi, C.; Casado, J.; Wu, J. Chem. Soc. Rev. 2015, 44, 6578.
3. Yuan, D.; Huang, D.; Medina Rivero, S.; Carreras, A.; Zhang, C.; Zou, Y.; Jiao, X.;
McNeill, C.R.; Zhu, X.; Di, C.; Zhu, D.; Casanova, D.; Casado, J. CHEM, 2019, accepted.Universidad de Málaga. Campus de Excelencia Internacional AndalucÃa Tech
The fox Operon from Rhodobacter Strain SW2 Promotes Phototrophic Fe(II) Oxidation in Rhodobacter capsulatus SB1003
Anoxygenic photosynthesis based on Fe(II) is thought to be one of the most ancient forms of metabolism and is hypothesized to represent a transition step in the evolution of oxygenic photosynthesis. However, little is known about the molecular basis of this process because, until recently (Y. Jiao and D. K. Newman, J. Bacteriol. 189:1765-1773, 2007), most phototrophic Fe(II)-oxidizing bacteria have been genetically intractable. In this study, we circumvented this problem by taking a heterologous-complementation approach to identify a three-gene operon (the foxEYZ operon) from Rhodobacter sp. strain SW2 that confers enhanced light-dependent Fe(II) oxidation activity when expressed in its genetically tractable relative Rhodobacter capsulatus SB1003. The first gene in this operon, foxE, encodes a c-type cytochrome with no significant similarity to other known proteins. Expression of foxE alone confers significant light-dependent Fe(II) oxidation activity on SB1003, but maximal activity is achieved when foxE is expressed with the two downstream genes foxY and foxZ. In SW2, the foxE and foxY genes are cotranscribed in the presence of Fe(II) and/or hydrogen, with foxZ being transcribed only in the presence of Fe(II). Sequence analysis predicts that foxY encodes a protein containing the redox cofactor pyrroloquinoline quinone and that foxZ encodes a protein with a transport function. Future biochemical studies will permit the localization and function of the Fox proteins in SW2 to be determined
Neutrinoless double-beta decay matrix elements in large shell-model spaces with the generator-coordinate method
We use the generator-coordinate method with realistic shell-model
interactions to closely approximate full shell-model calculations of the matrix
elements for the neutrinoless double-beta decay of Ca, Ge, and
Se. We work in one major shell for the first isotope, in the
space for the second and third, and finally in two major
shells for all three. Our coordinates include not only the usual axial
deformation parameter , but also the triaxiality angle and
neutron-proton pairing amplitudes. In the smaller model spaces our matrix
elements agree well with those of full shell-model diagonalization, suggesting
that our Hamiltonian-based GCM captures most of the important valence-space
correlations. In two major shells, where exact diagonalization is not currently
possible, our matrix elements are only slightly different from those in a
single shell.Comment: 8 pages, 7 figure
Two-phase flow dynamics in the gas diffusion layer of proton exchange membrane fuel cells: Volume of fluid modeling and comparison with experiment
This paper proposes a three-dimensional (3D) volume of fluid (VOF) study to investigate two-phase flow in the gas diffusion layer (GDL) of proton exchange membrane (PEM) fuel cells and liquid water distribution. A stochastic model was adopted to reconstruct the 3D microstructures of Toray carbon papers and incorporate the experimentally-determined varying porosity. The VOF predictions were compared with the water profiles obtained by the X-ray tomographic microscopy (XTM) and the Leverett correlation. It was found local water profiles are similar in the sample’s sub-regions under the pressure difference p = 1000 Pa between the two GDL surfaces, but may vary significantly under p = 6000 Pa. The water-air interfaces inside the GDL structure were presented to show water distribution and breakthrough
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Investigating the in-/through-plane effective diffusivities of dry and partially-saturated gas diffusion layers
In this study, the effective oxygen diffusivity in the dry or partially-saturated gas diffusion layer (GDL) is numerically investigated by an oxygen diffusion model in GDLs reconstructed by a stochastic method. The predicted effective diffusivity in dry GDLs is compared with various diffusivity models from literatures. Reasonable agreements with other models were obtained. The effect of the PTFE loading in the dry Toray carbon paper is also investigated and compared with recent experimental data. It is found that the effective diffusivity becomes lower under higher PTFE loading due to the decreased pore volume, as expected. The relative effective oxygen diffusivity in partially-saturated GDLs is calculated using the two-phase volume of fluid (VOF) model and an oxygen diffusion model. The effects of different local water profiles and porosity distribution on the effective oxygen diffusivity in both the through-plane (TP) and in-plane (IP) directions are investigated and compared with a lattice Boltzmann model and experimental data. The present results are in good agreement with other studies. It is found that local water profile has significant impacts on the effective diffusivity in partially-saturated GDLs and the diffusivity in the TP direction is more sensitive to the water distribution than the IP direction
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Transit in the land of plenty : a case for linking land use patterns and public transit service planning
This professional report examines academic literature on needs-gaps analyses in transit planning and proposes that this methodology ignores the basic premise of transit planning which is to serve a region and respond to land uses. The report proposes identifying land use patterns in Dallas County, TX for improved transit service. The research incorporates land use into needs-gaps analyses to test the relevancy of this proposal.Community and Regional Plannin
The Green-function transform and wave propagation
Fourier methods well known in signal processing are applied to
three-dimensional wave propagation problems. The Fourier transform of the Green
function, when written explicitly in terms of a real-valued spatial frequency,
consists of homogeneous and inhomogeneous components. Both parts are necessary
to result in a pure out-going wave that satisfies causality. The homogeneous
component consists only of propagating waves, but the inhomogeneous component
contains both evanescent and propagating terms. Thus we make a distinction
between inhomogenous waves and evanescent waves. The evanescent component is
completely contained in the region of the inhomogeneous component outside the
k-space sphere. Further, propagating waves in the Weyl expansion contain both
homogeneous and inhomogeneous components. The connection between the Whittaker
and Weyl expansions is discussed. A list of relevant spherically symmetric
Fourier transforms is given
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