Extreme event quantification in dynamical systems with random components

A central problem in uncertainty quantification is how to characterize the impact that our incomplete knowledge about models has on the predictions we make from them. This question naturally lends itself to a probabilistic formulation, by making the unknown model parameters random with given statistics. Here this approach is used in concert with tools from large deviation theory (LDT) and optimal control to estimate the probability that some observables in a dynamical system go above a large threshold after some time, given the prior statistical information about the system's parameters and/or its initial conditions. Specifically, it is established under which conditions such extreme events occur in a predictable way, as the minimizer of the LDT action functional. It is also shown how this minimization can be numerically performed in an efficient way using tools from optimal control. These findings are illustrated on the examples of a rod with random elasticity pulled by a time-dependent force, and the nonlinear Schr\"odinger equation (NLSE) with random initial conditions

Wave-Turbulence Theory of four-wave nonlinear interactions

The Sagdeev-Zaslavski (SZ) equation for wave turbulence is analytically derived, both in terms of generating function and of multi-point pdf, for weakly interacting waves with initial random phases. When also initial amplitudes are random, the one-point pdf equation is derived. Such analytical calculations remarkably agree with results obtained in totally different fashions. Numerical investigations of the two-dimensional nonlinear Schroedinger equation (NLSE) and of a vibrating plate prove that: (i) generic Hamiltonian 4-wave systems rapidly attain a random distribution of phases independently of the slower dynamics of the amplitudes, vindicating the hypothesis of initially random phases; (ii) relaxation of the Fourier amplitudes to the predicted stationary distribution (exponential) happens on a faster timescale than relaxation of the spectrum (Rayleigh-Jeans distribution); (iii) the pdf equation correctly describes dynamics under different forcings: the NLSE has an exponential pdf corresponding to a quasi-gaussian solution, like the vibrating plates, that also show some intermittency at very strong forcings

Vinicia tomentosa, new genus and species of Lychnophorinae (Vernonieae, Asteraceae) from Minas Gerais, Brazil

Se describe e ilustra un nuevo género y especie de la tribu Vernonieae (Asteraceae) de los cerrados y campos rupestres de Minas Gerais (Brasil). El nuevo taxon, Vinicia tomentosa Dematt., está estrechamente relacionado a Chronopappus DC. y Lychnophora Mart., pero difiere por presentar glomérulos pedunculados y el involucro estrechamente cilíndrico. Los dos géneros anteriores siempre tienen glomérulos sésiles y el involucro es turbinado o cilíndrico en Lychnophora y ovoideo en ChronopappusA new genus and species of the tribe Vernonieae (Asteraceae) from the cerrado and campo rupestre vegetation of Minas Gerais (Brazil) is described and illustrated. The new taxon, Vinicia tomentosa Dematt. is closely related to Chronopappus DC. and Lychnophora Mart., but differs in having pedunculate glomerules and the narrowly cylindrical involucre. The other two genera always have sessile glomerules and the involucre is turbinate to cylindrical in Lychnophora and ovoid in ChronopappusFil: Dematteis, Massimiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentin

A revision of the South American genus Chrysolaena (Vernonieae, Asteraceae)

El género Chrysolaena H. Rob. (Vernonieae, Asteraceae) se diferencia de los restantes miembros sudamericanos de la tribu por la presencia de indumento seríceo o velutino, anteras con apéndice apical glanduloso, estilo sin nódulo basal y cipselas glandulares. También se puede separar de otros grupos americanos por la morfología de los granos de polen y el número de cromosomas. Esta última es una de las diferencias más importantes, dado que Chrysolaena es el único miembro americano de la tribu con número básico x=10, un guarismo presente principalmente en las Vernonieae del Viejo Mundo. Hasta la actualidad, este género comprende 12 especies distribuidas principalmente en el sur de Brasil, Paraguay y nordeste de Argentina. En el presente trabajo se describen e ilustran todas las especies reconocidas hasta ahora y se incorporan otras seis entidades, dos de las cuales son nuevas para la ciencia. También se discuten las posibles relaciones filogenéticas del género y se amplía la distribución geográfica de la mayoría de las especiesA revision of the South American genus Chrysolaena (Vernonieae, Asteraceae.The genus Chrysolaena H. Rob. (Vernonieae, Asteraceae) can be distinguished from the remaining South American members of the tribe by its sericeous to velvety indumentum, anthers with glandular apical appendages, styles lacking a basal nodule and glandular cypselas. It can also be separated from other American genera of the tribe by the pollen morphology and the chromosome number. The last constitutes one of the most important features, because Chrysolaena is the single American member of the tribe with basic number x=10, a number widespread in Old World Vernonieae. At the present, this genus comprises 12 species mainly distributed in southern Brazil, Paraguay and northeastern Argentina. In this paper, all the species recognized until now are described and illustrated and six entities are added to the group, two of which are new taxa. The possible phylogenetic relationships of the genus are also discussed and the geographic distribution of most species is revised to include a larger areaFil: Dematteis, Massimiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; Argentin

Remote Neuropsychological Assessment: Does Mode of Administration Matter?

Neuropsychology relies heavily on standardization of administration to increase the validity, reliability, sensitivity, and specificity of an assessment instrument. The COVID-19 pandemic has rapidly increased the need to be able to provide neuropsychological assessments remotely. Teleneuropsychology can be conducted through various avenues, including telephone, computerized, and televideo modalities. Given neuropsychology\u27s reliance on standardization for proper use of normative data that accompanies individual assessments, the question arises how mode of administration impacts the validity, reliability, sensitivity, and specificity of an assessment instrument. The literature review summarizes the research conducted regarding the validity, reliability, sensitivity, and specificity of telephone neuropsychological assessments, computerized neuropsychological assessments, and televideo neuropsychological assessments. Additionally, the literature review aims to provide guidelines for best practice for each mode of administration for practicing neuropsychologists