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141.
Elvira Barbera Carmela Currò Giovanna Valenti 《Mathematical Methods in the Applied Sciences》2010,33(12):1504-1515
A hyperbolic predator–prey model is proposed within the context of extended thermodynamics. The nature of the steady state solutions for the uniform and non‐uniform perturbations are analyzed. The existence of smooth traveling wave‐like solutions, related to the invasion of the predator population into a prey‐only state is discussed. Validation of the model in point is also accomplished by searching for numerical solutions of the system, which also points out limit cycles in the populations. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
142.
Chiara Lavarello Sebastiano Barco Martina Bartolucci Isabella Panfoli Emanuele Magi Gino Tripodi Andrea Petretto Giuliana Cangemi 《Molecules (Basel, Switzerland)》2021,26(14)
Liquid-chromatography coupled to high resolution mass spectrometry (LC-HRMS) is currently the method of choice for untargeted metabolomic analysis. The availability of established protocols to achieve a high confidence identification of metabolites is crucial. The aim of this work is to describe the workflow that we have applied to build an Accurate Mass Retention Time (AMRT) database using a commercial metabolite library of standards. LC-HRMS analysis was carried out using a Vanquish Horizon UHPLC system coupled to a Q-Exactive Plus Hybrid Quadrupole-Orbitrap Mass Spectrometer (Thermo Fisher Scientific, Milan, Italy). The fragmentation spectra, obtained with 12 collision energies, were acquired for each metabolite, in both polarities, through flow injection analysis. Several chromatographic conditions were tested to obtain a protocol that yielded stable retention times. The adopted chromatographic protocol included a gradient separation using a reversed phase (Waters Acquity BEH C18) and a HILIC (Waters Acquity BEH Amide) column. An AMRT database of 518 compounds was obtained and tested on real plasma and urine samples analyzed in data-dependent acquisition mode. Our AMRT library allowed a level 1 identification, according to the Metabolomics Standards Initiative, of 132 and 124 metabolites in human pediatric plasma and urine samples, respectively. This library represents a starting point for future metabolomic studies in pediatric settings. 相似文献
143.
144.
We present an extension of the mosaic method aimed at capturing many-dimensional modal logics. As a proof-of-concept, we define the method for logics arising from the combination of linear tense operators with an “orthogonal” S5-like modality. We show that the existence of a model for a given set of formulas is equivalent to the existence of a suitable set of partial models, called mosaics, and apply the technique not only in obtaining a proof of decidability and a proof of completeness for the corresponding Hilbert-style axiomatization, but also in the development of a mosaic-based tableau system. We further consider extensions for dealing with the case when interactions between the two dimensions exist, thus covering a wide class of bundled Ockhamist branching-time logics, and present for them some partial results, such as a non-analytic version of the tableau system. 相似文献
145.
Bernard Dacorogna Paolo Marcellini Emanuele Paolini 《NoDEA : Nonlinear Differential Equations and Applications》2013,20(2):345-359
The two well problem consists in finding maps u which satisfy some boundary conditions and whose gradient Du assumes values in the two wells ${\mathbb{S}_{A}, \mathbb{S}_{B}}$ . Here ${\mathbb{S}_{A}}$ (similarly ${\mathbb{S}_{B}}$ ) is the well generated by a 2 × 2 matrix A, i.e., ${\mathbb{S}_{A}}$ is the set of matrices of the form RA, where R is a rotation. We study specifically the case when at least one of the two matrices A, B is singular and we characterize piecewise affine maps u satisfying almost everywhere the differential inclusion ${Du(x) \in \mathbb{S}_{A} \cup \mathbb{S}_{B}}$ . In particular we describe the lamination and angle properties, which turn out to be different from those of the nonsingular case described in detail in [15]. We also show that the two well problem can be solved in some cases involving singular matrices, in strict contrast to the nonsingular (and not orthogonal) case. 相似文献
146.
Spectroscopic Fourier self-deconvolution analysis was used to investigate β-sheet features in the secondary structure of hemoglobin under mobile phone microwaves at 900 MHz. To this end, four samples of hemoglobin in bidistilled water, sucrose, trehalose, and sodium chloride aqueous solutions were exposed for up to 4 hr to 900 MHz microwaves at an average H-field intensity of 42 mA/m. Quantitative spectral analyses highlighted significant increases in β-sheet contents in the Amide I region of hemoglobin samples in bidistilled water solution, but no appreciable change was observed in hemoglobin samples in sucrose, trehalose, and sodium chloride solutions. These results led us to conclude that mobile phone microwaves can denaturate hemoglobin in bidistilled water solution whereas sucrose, trehalose, and sodium chloride solutions produce a protective effect against microwaves, preserving the protein from unfolding. 相似文献
147.
Emanuele Berti 《Brazilian Journal of Physics》2013,43(5-6):341-350
Astrophysical tests of general relativity belong to two categories: 1) “internal”, i.e. consistency tests within the theory (for example, tests that astrophysical black holes are indeed described by the Kerr solution and its perturbations), or 2) “external”, i.e. tests of the many proposed extensions of the theory. I review some ways in which astrophysical black holes can be used as natural laboratories for both “internal” and “external” tests of general relativity. The examples provided here (ringdown tests of the black hole “no-hair” theorem, bosonic superradiant instabilities in rotating black holes and gravitational-wave tests of massive scalar-tensor theories) are shamelessly biased towards recent research by myself and my collaborators. Hopefully this colloquial introduction aimed mainly at astrophysicists will convince skeptics (if there are any) that space-based detectors will be crucial to study fundamental physics through gravitational-wave observations. 相似文献
148.
Alessio Emanuele Biondo Alessandro Pluchino Andrea Rapisarda 《Journal of statistical physics》2013,151(3-4):607-622
In this paper we focus on the beneficial role of random strategies in social sciences by means of simple mathematical and computational models. We briefly review recent results obtained by two of us in previous contributions for the case of the Peter principle and the efficiency of a Parliament. Then, we develop a new application of random strategies to the case of financial trading and discuss in detail our findings about forecasts of markets dynamics. 相似文献
149.
Simulation models support managers in the solution of complex problems. International agencies recommend uncertainty and global sensitivity methods as best practice in the audit, validation and application of scientific codes. However, numerical complexity, especially in the presence of a high number of factors, induces analysts to employ less informative but numerically cheaper methods. This work introduces a design for estimating global sensitivity indices from given data (including simulation input–output data), at the minimum computational cost. We address the problem starting with a statistic based on the L1-norm. A formal definition of the estimators is provided and corresponding consistency theorems are proved. The determination of confidence intervals through a bias-reducing bootstrap estimator is investigated. The strategy is applied in the identification of the key drivers of uncertainty for the complex computer code developed at the National Aeronautics and Space Administration (NASA) assessing the risk of lunar space missions. We also introduce a symmetry result that enables the estimation of global sensitivity measures to datasets produced outside a conventional input–output functional framework. 相似文献
150.
C. Corianò A.E. Faraggi M. Guzzi 《The European Physical Journal C - Particles and Fields》2008,53(3):421-428
The standard model indicates the realization of grand unified structures in nature, and it can only be viewed as an effective
theory below a higher energy cutoff. While the renormalizable standard model forbids proton decay mediating operators due
to accidental global symmetries, many extensions of the standard model introduce such dimension 4, 5 and 6 operators. Furthermore,
quantum gravity effects are expected to induce proton instability, indicating that the higher energy cutoff scale must be
above 1016 GeV. Quasi-realistic heterotic string models provide the arena to explore how perturbative quantum gravity affects the particle
physics phenomenology. An appealing explanation for the proton longevity is provided by the existence of an Abelian gauge
symmetry that suppresses the proton decay mediating operators. Additionally, such a low scale U(1) symmetry should feature
the following: it should allow for the suppression of the left-handed neutrino masses by a seesaw mechanism; allow for fermion
Yukawa couplings to the electroweak Higgs doublets; be anomaly free; and finally be family universal. These requirements render
the existence of such U(1) symmetries in quasi-realistic heterotic string models highly non-trivial. We demonstrate the existence
of a U(1) symmetry that satisfies all of the above requirements in a class of left–right symmetric heterotic string models
in the free fermionic formulation. The existence of the extra in the energy range accessible to future experiments is motivated by the requirement of adequate suppression of proton decay
mediation. We further show that, while the extra U(1) forbids dimension 4 baryon number violating operators, it allows dimension
4 lepton number violating operators and R-parity violation. 相似文献