T-fold sequential-validation technique for out-of-distribution generalization with financial time series data

The temporal structure in financial time series (FTS) data demands non-trivial considerations in the use of cross-validation (CV). Such frequently used technique is based on statistical learning theory, which is founded on the assumption that training samples are i.i.d. Although there is progress in studying fundamental phenomenons in certain learning methods such as feature selection imbalance during the learning stage, it is currently widely accepted that there will be no reason to expect good out of sample results from a learning process without such strong assumption. In FTS, there are conditions under which sub-sampling data leads to overshadow the effect of non-deterministic relationships between features and the target variable among different samples. Such effect remains unnoticed given the use of the additivity property in the decomposition of objective functions for the Learning Process. Moreover, it reduces to a particular operation the relationship among samples without information attribution. We present a technique that controls information leakage and decomposes the global probability distribution into local probability distributions, providing identification of each sample contribution to the learning process, maintaining information sparsity, therefore, relaxing the effects of the i.i.d. assumption. Parametric stability, as a result, is presented for exchange rate prediction using different predictive models.ITESO, A.C

High-Order SUSY-QM, the Quantum XP Model and zeroes of the Riemann Zeta function

Making use of the first- and second-order algorithms of supersymmetric quantum mechanics (SUSY-QM), we construct quantum mechanical Hamiltonians whose spectra are related to the zeroes of the Riemann Zeta function $\zeta(s)$. Inspired by the model of Das and Kalauni (DK), which corresponds to this function in the strip $0<Re[s]<1$, and taking the factorization energy equal to zero, we use the wave function $|x|^{-S}$, $S\in\mathbb{C}$, as a seed solution for our algorithms, obtaining XP-like operators. Thus, we construct SUSY-QM partner Hamiltonians whose zero energy mode locates exactly the nontrivial zeroes of $\zeta(s)$ along the critical line $Re[s]=1/2$ in the complex plane. We further find that unlike the DK case, where the SUSY-QM partner potentials correspond to free particles, our partner potentials belong to the family of inverse squared distance potentials with complex couplings

Under Reporting of Dementia Deaths on Death Certificates: A Systematic Review of Population-based Cohort Studies

The purpose of this review is to assess the extent to which dementia is omitted as a cause of death from the death certificates of patients with dementia. A systematic literature search was performed to identify population-based cohort studies in which all participants were examined or screened for symptoms of dementia with a validated instrument followed by confirmation of any suspected cases with a clinical examination (two-phase investigation). Data were extracted in a standardized manner and assessed through the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) initiative. Seven studies met the selection criteria. These were from the Americas (5 articles: 2 from Canada, 2 from the US, and 1 from Brazil) and Europe (2 articles: 1 from the UK and 1 from Spain). Each met at least 83% of the STROBE criteria. The reporting of dementia on death certificates was poor in these 7 studies, ranging from 7.2%-41.8%. Respiratory or circulatory-related problems were the most frequently reported causes of death among people who were demented but who were not reported as demented on death certificates. The use of death certificates for studying dementia grossly underestimates the occurrence of dementia in the population. The poor reporting of dementia on these certificates suggests a lack of awareness of the importance of dementia as a cause of death among medical personnel. There is an urgent need to provide better education on the importance of codification of dementia on death certificates in order to minimize errors in epidemiological studies on dementia.pre-print475 K

Dirac materials in parallel non-uniform electromagnetic fields generated by SUSY: A new class of chiral Planar Hall Effect?

Within a Supersymmetric Quantum Mechanics (SUSY-QM) framework, the (3+1) Dirac equation describing a Dirac material in the presence of external parallel electric and magnetic fields is solved. Considering static but non-uniform electric and magnetic profiles with translational symmetry along the y-direction, the Dirac equation is transformed into two decoupled pairs of Schr\"odinger equations, one for each chirality of the fermion fields. Taking trigonometric and hyperbolic profiles for the vector and scalar potentials, respectively, we arrive at SUSY partner P\"oschl-Teller-like quantum potentials. Restricting to the conditions of the potentials that support an analytic zero-mode solution, we obtain a nontrivial current density in the same plane where the electric and magnetic fields lie, but perpendicular to both of them, indicating the possibility of realizing the Planar Hall Effect. Furthermore, this non-vanishing current density is the sum of current densities for the left- and right-chiralities, suggesting that the net current is a consequence of chiral symmetry.Comment: 10 pages, 6 figure

Tissue distribution of mercury and its relationship with selenium in atlantic bluefin tuna (Thunnus thynnus l.)

Mercury (Hg) is an important heavy metal to consider in marine predators, while selenium (Se) has a natural antagonistic effect on this metal in fish. The Atlantic bluefin tuna (ABFT, Thunnus thynnus) is a pelagic top-level predator of the trophic web and their Hg muscular content is an object of concern in food safety. Nevertheless, little is known about levels of this metal in remaining tissues, which may be important as by-product source, and its relationship with Se. Thus, concentration of both elements in liver, kidney, brain, gill and bone, in addition to muscle, of ABFT were determined. The kidney was the tissue with the highest concentration of Hg (Total-Hg, THg) and Se, and the Se/THg concentration ratio was similar in all tissues, except bone and muscle. The Selenium Health Benefit Value (HBVSe ) was positive in each specimen and tissue, indicating that the Se plays an important role against Hg not only in the muscle. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Preprin

A Second Order Sliding Mode Controller with Predefined-Time Convergence

This paper presents the basis to design a well-suited control law which guarantees predefined-time convergence for a class of second-order systems. In contrast to the case of finite-time and fixed-time controllers, a predefined-time controller allows to set the bound of the convergence time, explicitly during the control design. Furthermore, in the case of no disturbance, the least upper bound of the convergence time can be predefined directly from the control definition. A Lyapunov-like characterization for predefined-time stability is performed. Numerical results are discussed to show the reliability of the proposed method.Consejo Nacional de Ciencia y Tecnologí

Optimización del Tratamiento Térmico de Productos Tubulares de Acero

[Optimization of Heat Treatment of Steel Tubular Products] El problema a abordar es el de la optimización del tratamiento térmico de productos tubulares de acero, presente en la empresa siderúrgica Tenaris. Más específicamente, se estudia el problema de dar un tratamiento adecuado a cargas retenidas en el horno de revenido. En este caso, el tratamiento térmico se compone de un primer calentamiento de los tubos a temperaturas cercanas a los 900°C, en el que se austeniza el material, seguido por un enfriamiento rápido en el que el material se transforma en martensita. Esta etapa constituye el templado del acero. Para lograr las propiedades metalúrgicas finales especificadas para el producto se realiza un segundo calentamiento a temperaturas entre 500 y 700°C, que se denomina revenido. Para simplificar el análisis, en este trabajo se considera una única propiedad metalúrgica, la dureza, que para el producto que se analiza debe estar en el rango de 270-300 Hv

Supersymmetric Quantum Mechanics, multiphoton algebras and coherent states

The multiphoton algebras for one-dimensional Hamiltonians with infinite discrete spectrum, and for their associated kth-order SUSY partners are studied. In both cases, such an algebra is generated by the multiphoton annihilation and creation operators, as well as by Hamiltonians which are functions of an appropriate number operator. The algebras obtained turn out to be polynomial deformations of the corresponding single-photon algebra previously studied. The Barut-Girardello coherent states, which are eigenstates of the annihilation operator, are obtained and their uncertainty relations are explored by means of the associated quadratures.Comment: Last version of the paper, 6 figure

Master in Water Engineering a “semi-attendance” University-specific degree with international participation

The Water Engineering Master Course is a university-specific degree at the University of Seville which nowadays can be coursed in two different modalities: “on line” and “semi-attendance”. Its first edition took place at 2000 and since then, the average of graduated students has been of 40 students per course. The semi-attendance mode offers the possibility of being followed in an on-line way from November to June. A Moodle platform provides all the documentation that is required to attend every module, at the end of each one some online questionnaires are also uploaded in order to evaluate the students. Only one of the 10 mandatory modules which make up the course have to be attended in a classroom mode. It takes place during 15 days in July and allows the students to come into contact with the lecturers, professionals of the sector and their own mates as well. During this period both, teachers and students, are lodged in the same residence and all of them have the chance of interchanging experiences in a full teaching-learning process, solving doubts and improving their skills thanks to specific courses, specially designed in function of the lack of knowledge which has been detected during de previous modules, o even, the suggestions received directly from students. Most of the students come from Hispanic countries and in less amount from African and European countries. Actually every July about 80 students and teachers from 25 different countries around the world, meet in Seville to attend this Master. The classes are given in Spanish with translator support if it’s necessary. Different environments, problematic and conditioning factors are studied and a large kind of solutions in water cycle are designed during these days. The requirements to elaborate the final master project are mainly that this one can be used to resolve a real local problem in the student’s origin place and moreover the student can obtain better marks if he/she finds financing to carry it out. In the last 8 years a useful module named “Tools for design” has been included in the program of the Master in order to enable the student in IT, specifically spreadsheets, cad, software for budgeting and measurement, topography and decision support systems. Students who graduate are able to evaluate the most proper technology from a social, technic and economic point of view, as well as, select the most efficient alternatives in order to achieve a sustainable development

A Note on Predefined-Time Stability

This note presents a new characterization for predefined-time-stable systems based on Lyapunov stability. In contrast to the previous results in predefined-time stability, the proposed characterization allows the construction of predefined-time stabilizing controllers with polynomial terms instead of exponential ones, removing the exponential nature hypothesis of predefined-time-stable systems. Moreover, the existing Lyapunov characterization of predefined-time stability is shown to be a consequence of the new theorem presented in this paper. Finally, the proposed approach is used for the construction of robust predefined-time stabilizing controllers for first-order systems. A simulation example shows the feasibility of the proposed methods.Consejo Nacional de Ciencia y Tecnologí