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  • 1
    Publication Date: 2018-03-06
    Description: Hemi-implicative semilattices (lattices), originally defined under the name of weak implicative semilattices (lattices), were introduced by the second author of the present article. A hemi-implicative semilattice is an algebra $(H,{\wedge},{\rightarrow},1)$ of type $(2,2,0)$ such that $(H,{\wedge})$ is a meet semilattice, $1$ is the greatest element with respect to the order, $a{\rightarrow} a = 1$ for every $a\in H$ and for every $a$, $b$, $c\in H$, if $a\leq b{\rightarrow} c$ then $a{\wedge} b \leq c$. A bounded hemi-implicative semilattice is an algebra $(H,{\wedge},{\rightarrow},0,1)$ of type $(2,2,0,0)$ such that $(H,{\wedge},{\rightarrow},1)$ is a hemi-implicative semilattice and $0$ is the first element with respect to the order. A hemi-implicative lattice is an algebra $(H,{\wedge},\vee,{\rightarrow},0,1)$ of type $(2,2,2,0,0)$ such that $(H,{\wedge},\vee,0,1)$ is a bounded distributive lattice and the reduct algebra $(H,{\wedge},{\rightarrow},1)$ is a hemi-implicative semilattice. In this article, we introduce an equivalence for the categories of bounded hemi-implicative semilattices and hemi-implicative lattices, respectively, which is motivated by an old construction due J. Kalman that relates bounded distributive lattices and Kleene algebras.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
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  • 2
    Publication Date: 2013-11-14
    Description: We present a new approach in astrodynamics and celestial mechanics fields, called hybrid perturbation theory. A hybrid perturbation theory combines an integrating technique, general perturbation theory or special perturbation theory or semianalytical method, with a forecasting technique, statistical time series model or computational intelligence method. This combination permits an increase in the accuracy of the integrating technique, through the modeling of higher-order terms and other external forces not considered in the integrating technique. In this paper, neural networks have been used as time series forecasters in order to help two economic general perturbation theories describe the motion of an orbiter only perturbed by the Earth’s oblateness.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 3
    Publication Date: 2015-03-28
    Description: In this article, we introduce and study a family of compatible functions in Hilbert algebras which in the case of Heyting algebras agree with the frontal operators given by Esakia (2006, J. Appl. Non-Class. Log ., 16, 349–366). Moreover, we give a representation theory, based on previous works by Cabrer, Celani and Montangie, for Hilbert algebras with a frontal operator and for Hilbert algebras with some particular frontal operators.
    Print ISSN: 1367-0751
    Electronic ISSN: 1368-9894
    Topics: Mathematics
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  • 4
    Publication Date: 2014-07-07
    Description: A scalable second-order analytical orbit propagator programme based on modern and classical perturbation methods is being developed. As a first step in the validation and verification of part of our orbit propagator programme, we only consider the perturbation produced by zonal harmonic coefficients in the Earth’s gravity potential, so that it is possible to analyze the behaviour of the mathematical expressions involved in Delaunay normalization and the Krylov-Bogoliubov-Mitropolsky method in depth and determine their limits.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 5
    Publication Date: 2015-03-03
    Description: Deprit’s method has been revisited in order to take advantage of certain arbitrariness arising when the inverse of the Lie operator is applied to obtain the generating function of the Lie transform. This arbitrariness is intrinsic to all perturbation techniques and can be used to demonstrate the equivalence among different perturbation methods, to remove terms from the generating function of the Lie transform, or to eliminate several angles simultaneously in the case of having a degenerate Hamiltonian.
    Print ISSN: 1024-123X
    Electronic ISSN: 1563-5147
    Topics: Mathematics , Technology
    Published by Hindawi
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  • 6
    Publication Date: 2015-05-03
    Description: Genome packing in adenovirus has long evaded precise description, since the viral dsDNA molecule condensed by proteins (core) lacks icosahedral order characteristic of the virus protein coating (capsid). We show that useful insights regarding the organization of the core can be inferred from the analysis of spatial distributions of the DNA and condensing protein units (adenosomes). These were obtained from the inspection of cryo-electron tomography reconstructions of individual human adenovirus particles. Our analysis shows that the core lacks symmetry and strict order, yet the adenosome distribution is not entirely random. The features of the distribution can be explained by modeling the condensing proteins and the part of the genome in each adenosome as very soft spheres, interacting repulsively with each other and with the capsid, producing a minimum outward pressure of ~0.06 atm. Although the condensing proteins are connected by DNA in disrupted virion cores, in our models a backbone of DNA linking the adenosomes is not required to explain the experimental results in the confined state. In conclusion, the interior of an adenovirus infectious particle is a strongly confined and dense phase of soft particles (adenosomes) without a strictly defined DNA backbone.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 7
    Publication Date: 2019-07-11
    Description: SUMMARY In addition to enabling the physical processes of volcanic systems to be better understood, seismology has been also used to infer the complexity of magma pathways and plumbing systems in steep-sided andesitic and stratovolcanoes. However, in these volcanic environments, the application of seismic location methods is particularly challenging and systematic comparisons of common methods are lacking. Furthermore, little is known about the characteristic seismicity and deep structure of Lascar volcano, one of the most historically active volcanoes in northern Chile known to produce VEI-4 eruptions. To better understand the inner processes and deep structure of Lascar, the local broad-band seismic monitoring network was densified during a temporal installation in 2014–2015. Herein, we focus on the local seismicity during the 2014–2015 unrest episode, during which we recorded numerous seismic events mainly classified as long-period (LP) type, but also denote volcano-tectonic (VT) activity. Specifically, a long-lasting phase of LP activity is observed over a period of ∼14 months that starts in tandem with a pulse of VT activity. The LP rate and amplitude are modulated over time; they are lower in the initial phase, rise during the intermediate period from October 2014 to July 2015, and finally slowly decay while approaching the eruption time. The location of LPs is challenging due to the typical lack of clear seismic onsets. We thus encompass this problem by comparing a broad range of different standard and novel location techniques to map the source region of LPs by fitting the amplitude decay, polarization patterns, coherence of characteristic functions and cross-correlation differential times. As a result, we principally constrain LP locations within the first 5 km depth below the summit extending downward along a narrow, conduit-like path. We identify different regions of complexity: VTs dominate at depth, both VTs and LPs cluster in an intermediate depth region (down to 1.5 km), suggesting a change in the plumbing system geometry, and LPs dominate the shallowest region. Based on these results, we infer the presence of a subvertical conduit extending down to a depth of ∼5 km, and a region of path divergence, possibly accommodating a magma plumbing system, at a depth of ∼3 km beneath the volcano summit. Identifying the locations of complexities in the magma pathways at Lascar may help identify future unrest. The results are compared with independent observations, demonstrating the strength of the location method used herein that will be tested at volcanoes elsewhere.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
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