3,966 research outputs found
Mathematical properties of formulations of the gas transmission problem
The paper presents the mathematical properties of several formulations for the gas transmission problem that account for the nonlinear flow pressure relations. The form of the nonlinear flow pressure relations is such that the model is in general nonconvex. However, we show here that under a restrictive condition (gas inlet or gas pressure fixed at every entry/outgoing node) the problem becomes convex. This result is obtained by use of the variational inequality theory. We also give a computational method to find a feasible solution to the problem and give a physical interpretation to this feasible solution
How do Multi-National Corporations CEOs perceive and communicate about Social Responsibility?
This paper aims to investigate Multi-National Corporations (MNC) Chief Executives Officers (CEO) perception of Corporate Social Responsibility (CSR) and their communication about it. As the key decision makers, CEOs have nowadays, a central role to play in implementing CSR. Thus, such investigation could be very useful for a better understanding of MNCs CSR approaches. A lexical analysis of one hundred and five executives letters from Sustainability and CSR reports revealed that CEOs evoke different CSR areas. As a matter of fact, they often focus on specific areas generally linked to their firm activity, particularly those which caused or may cause pressure from specific stakeholders. Besides, based on the investigation of linguistic features of the executives discourse, five categories of CEO discourses were identified. Nevertheless, the authors recognized that even such investigation could not give us a clear idea about the CEOs perception of CSR, because CEOs discourse is not spontaneous; it is rather stake-driven. Keywords: Corporate social responsibility, CEO, Discourse analysis, CSR communication, Lexical analysis
Utilisation des techniques de la recherche opérationnelle pour la sélection de portefeuille dans l'industrie pétrolière
Two important characteristics of petroleum exploration and production
investment are the high nancial amounts and uncertainties. For these rea-
sons, the risk analysis should be implemented in the projects evaluation and
the selection process. Depending on their available resources, petroleum
companies choose a number of projects on the basis of some criteria: the
net present value, internal rate of return, pro tability index However, these
criteria appear to be insu cient if we consider, on the one hand, the ab-
sence of risk idea which is an essential element of the petroleum industry,
on the other hand the omission of the correlations and interactions between
di erent projects. In this paper, in order to make up for the lacks of the
traditional approach, we apply a variant of Markowitzs method to deter-
mine the e cient portfolio exploration and production projects that insure
the best compromise minimum risk-maximum return under the di erent
constraints faced by the company. A practical application of this method
about selection of petroleum exploration projects in the North Sea is pre-
sented. This practical case illustrates the in
uence of the crude price in the
choice of the portfolio
Concentration of symmetric eigenfunctions
In this article we examine the concentration and oscillation effects
developed by high-frequency eigenfunctions of the Laplace operator in a compact
Riemannian manifold. More precisely, we are interested in the structure of the
possible invariant semiclassical measures obtained as limits of Wigner measures
corresponding to eigenfunctions. These measures describe simultaneously the
concentration and oscillation effects developed by a sequence of
eigenfunctions. We present some results showing how to obtain invariant
semiclassical measures from eigenfunctions with prescribed symmetries. As an
application of these results, we give a simple proof of the fact that in a
manifold of constant positive sectional curvature, every measure which is
invariant by the geodesic flow is an invariant semiclassical measure.Comment: 8 page
Exploring the Mutational Landscape of Isolated Congenital Heart Defects: An Exome Sequencing Study Using Cardiac DNA
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253059.pdf (Publisher’s version ) (Open Access
Myocardial disease and ventricular arrhythmia in Marfan syndrome : a prospective study
Background Aortic root dilatation and-dissection and mitral valve prolapse are established cardiovascular manifestations in Marfan syndrome (MFS). Heart failure and arrhythmic sudden cardiac death have emerged as additional causes of morbidity and mortality. Methods To characterize myocardial dysfunction and arrhythmia in MFS we conducted a prospective longitudinal case-control study including 86 patients with MFS (55.8% women, mean age 36.3 yr-range 13-70 yr-) and 40 age-and sex-matched healthy controls. Cardiac ultrasound, resting and ambulatory ECG (AECG) and NT-proBNP measurements were performed in all subjects at baseline. Additionally, patients with MFS underwent 2 extra evaluations during 30 +/- 7 months follow-up. To study primary versus secondary myocardial involvement, patients with MFS were divided in 2 groups: without previous surgery and normal/mild valvular function (MFS-1; N = 55) and with previous surgery or valvular dysfunction (MFS-2; N = 31). Results Compared to controls, patients in MFS-1 showed mild myocardial disease reflected in a larger left ventricular end-diastolic diameter (LVEDD), lower TAPSE and higher amount of (supra) ventricular extrasystoles [(S)VES]. Patients in MFS-2 were more severely affected. Seven patients (five in MFS-2) presented decreased LV ejection fraction. Twenty patients (twelve in MFS-2) had non-sustained ventricular tachycardia (NSVT) in at least one AECG. Larger LVEDD and higher amount of VES were independently associated with NSVT. Conclusion Our study shows mild but significant myocardial involvement in patients with MFS. Patients with previous surgery or valvular dysfunction are more severely affected. Evaluation of myocardial function with echocardiography and AECG should be considered in all patients with MFS, especially in those with valvular disease and a history of cardiac surgery
3D magnetic induction maps of nanoscale materials revealed by electron holographic tomography
This is an open access article published under a Creative Commons Attribution (CC-BY) License.-- et al.The investigation of three-dimensional (3D) ferromagnetic nanoscale materials constitutes one of the key research areas of the current magnetism roadmap and carries great potential to impact areas such as data storage, sensing, and biomagnetism. The properties of such nanostructures are closely connected with their 3D magnetic nanostructure, making their determination highly valuable. Up to now, quantitative 3D maps providing both the internal magnetic and electric configuration of the same specimen with high spatial resolution are missing. Here, we demonstrate the quantitative 3D reconstruction of the dominant axial component of the magnetic induction and electrostatic potential within a cobalt nanowire (NW) of 100 nm in diameter with spatial resolution below 10 nm by applying electron holographic tomography. The tomogram was obtained using a dedicated TEM sample holder for acquisition, in combination with advanced alignment and tomographic reconstruction routines. The powerful approach presented here is widely applicable to a broad range of 3D magnetic nanostructures and may trigger the progress of novel spintronic nonplanar nanodevices.This work was supported by the European Union under the Seventh Framework Program under a contract for an Integrated Infrastructure Initiative Reference 312483-ESTEEM2. S.B. and A.B. gratefully acknowledge funding by ERC Starting grants
number 335078 COLOURATOMS and number 278510 VORTEX. A.F.-P. acknowledges an EPSRC Early Career fellowship and support from the Winton Foundation. E.S.,
C.G., and L.A.R. acknowledge the French ANR program for support though the project EMMA. J.M.D.T. and C. M. acknowledge the Spanish MINECO projects MAT2014-51982-
C2-1-R and MAT2014-51982-C2-2-R, respectively.Peer Reviewe
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Recommended Thermal Rate Coefficients for the C + H3+ Reaction and Some Astrochemical Implications
We incorporate our experimentally derived thermal rate coefficients for C + forming CH+ and CH2 + into a commonly used astrochemical model. We find that the Arrhenius–Kooij equation typically used in chemical models does not accurately fit our data and instead we use a more versatile fitting formula. At a temperature of 10 K and a density of 104 cm−3, we find no significant differences in the predicted chemical abundances, but at higher temperatures of 50, 100, and 300 K we find up to factor of 2 changes. In addition, we find that the relatively small error on our thermal rate coefficients, ~15%, significantly reduces the uncertainties on the predicted abundances compared to those obtained using the currently implemented Langevin rate coefficient with its estimated factor of 2 uncertainty
Electron spin evolution induced by interaction with nuclei in a quantum dot
We study the decoherence of a single electron spin in an isolated quantum dot
induced by hyperfine interaction with nuclei for times smaller than the nuclear
spin relaxation time. The decay is caused by the spatial variation of the
electron envelope wave function within the dot, leading to a non-uniform
hyperfine coupling . We show that the usual treatment of the problem based
on the Markovian approximation is impossible because the correlation time for
the nuclear magnetic field seen by the electron spin is itself determined by
the flip-flop processes.
The decay of the electron spin correlation function is not exponential but
rather power (inverse logarithm) law-like. For polarized nuclei we find an
exact solution and show that the precession amplitude and the decay behavior
can be tuned by the magnetic field. The decay time is given by ,
where is the number of nuclei inside the dot. The amplitude of precession,
reached as a result of the decay, is finite. We show that there is a striking
difference between the decoherence time for a single dot and the dephasing time
for an ensemble of dots.Comment: Revtex, 11 pages, 5 figure
Recommended from our members
Recommended Thermal Rate Coefficients for the C + H3+ Reaction and Some Astrochemical Implications
We incorporate our experimentally derived thermal rate coefficients for C + forming CH+ and CH2 + into a commonly used astrochemical model. We find that the Arrhenius–Kooij equation typically used in chemical models does not accurately fit our data and instead we use a more versatile fitting formula. At a temperature of 10 K and a density of 104 cm−3, we find no significant differences in the predicted chemical abundances, but at higher temperatures of 50, 100, and 300 K we find up to factor of 2 changes. In addition, we find that the relatively small error on our thermal rate coefficients, ~15%, significantly reduces the uncertainties on the predicted abundances compared to those obtained using the currently implemented Langevin rate coefficient with its estimated factor of 2 uncertainty
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