Reflexiones sobre la enseñanza de la física universitaria

In spite of the scientific and technological development and a worldwide increment in the number of university students, it is evident a decrease in the number of students of physics in this level. This work brings out some features of the university education, particularly the teaching of the firsts courses. At the same time it is stated that a poor didactic knowledge, a rutinary teaching, that is not participative from the part of the teachers can be linked to a growing loss of interest from the part of the students. Finally the authors give some trends to make a deep study of this problem

The Global Struggle Over AI Surveillance: Emerging Trends and Democratic Responses

From cameras that identify the faces of passersby to algorithms that keep tabs on public sentiment online, artificial intelligence (AI)-powered tools are opening new frontiers in state surveillance around the world. Law enforcement, national security, criminal justice, and border management organizations in every region are relying on these technologies—which use statistical pattern recognition, machine learning, and big data analytics—to monitor citizens.What are the governance implications of these enhanced surveillance capabilities?This report explores the challenge of safeguarding democratic principles and processes as AI technologies enable governments to collect, process, and integrate unprecedented quantities of data about the online and offline activities of individual citizens. Three complementary essays examine the spread of AI surveillance systems, their impact, and the transnational struggle to erect guardrails that uphold democratic values.In the lead essay, Steven Feldstein, a senior fellow at the Carnegie Endowment for International Peace, assesses the global spread of AI surveillance tools and ongoing efforts at the local, national, and multilateral levels to set rules for their design, deployment, and use. It gives particular attention to the dynamics in young or fragile democracies and hybrid regimes, where checks on surveillance powers may be weakened but civil society still has space to investigate and challenge surveillance deployments.Two case studies provide more granular depictions of how civil society can influence this norm-shaping process: In the first, Eduardo Ferreyra of Argentina's Asociación por los Derechos Civiles discusses strategies for overcoming common obstacles to research and debate on surveillance systems. In the second, Danilo Krivokapic of Serbia's SHARE Foundation describes how his organization drew national and global attention to the deployment of Huawei smart cameras in Belgrade

Revisiting the core EP inverse and its extension to rectangular matrices

[EN] In this paper, we revise the core EP inverse of a square matrix introduced by Prasad and Mohana in [12], Core EP inverse, Linear and Multilinear Algebra62(3) (2014), 792-802. Firstly, we give a new representation and a new characterization of the core EP inverse. Then, we study some properties of the core EP inverse by using a representation by block matrices. Secondly, we extend the notion of core EP inverse to rectangular matrices by means of a weighted core EP decomposition. Finally, we study some properties of weighted core EP inverses.Partially supported by a CONICET's Postdoctoral Research Fellowship, Universidad Nacional de Ro Cuarto (grant PPI 18/C472) and CONICET (grant PIP 112-201501-00433CO). Partially supported by Ministerio de Economia y Competitividad of Spain (grants DGI MTM2013-43678-P and Red de Excelencia MTM2015-68805-REDT).Ferreyra, DE.; Levis, F.; Thome, N. (2018). Revisiting the core EP inverse and its extension to rectangular matrices. Quaestiones Mathematicae. 41(2):265-281. https://doi.org/10.2989/16073606.2017.1377779S26528141

Maximal classes of matrices determining generalized inverses

[EN] This paper derives some further results on recent generalized inverses studied in the literature, namely core EP, DMP, and CMP inverses. Our main aim is to develop maximal classes of matrices for which their representations remain valid. (C) 2018 Elsevier Inc. All rights reserved.Partially supported by a CONICET's Posdoctoral Research Fellowship, UNRC (grant PPI 18/C472) and CONICET (grant PIP 112-201501-00433CO). Partially supported by Ministerio de Economia y Competitividad of Spain (Grants DGI MTM2013-43678-P and Red de Excelencia MTM2017-90682-REDT).Ferreyra, DE.; Levis, F.; Thome, N. (2018). Maximal classes of matrices determining generalized inverses. Applied Mathematics and Computation. 333:42-52. https://doi.org/10.1016/j.amc.2018.03.102S425233

Left and right generalized Drazin invertible operators on Banach spaces and applications

[EN] In this paper, left and right generalized Drazin invertible operators on Banach spaces are defined and characterized by means of the generalized Kato decomposition. Then, new binary relations associated with these operators are presented and studied. In addition, a new characterization of the generalized Drazin pre-order and a sufficient condition for that to be a partial order are given by using a matrix operator technique.This paper was partially supported by Universidad Nacional de La Pampa, Facultad de Ingenieria (grant Resol. No 155/14), Universidad Nacional de Rio Cuarto (grant PPI 18/C472) and CONICET (grant PIP 112-201501-00433CO). Fourth author was partially supported by Ministerio de Economia y Competitividad of Spain (grant Red de Excelencia MTM2017-90682-REDT).Ferreyra, DE.; Latanzi, M.; Levis, F.; Thome, N. (2019). Left and right generalized Drazin invertible operators on Banach spaces and applications. Operators and Matrices. 13(3):569-583. https://doi.org/10.7153/oam-2019-13-43S56958313

Representations of the weighted WG inverse and a rank equation's solution

In this paper, we present several representations of the W-weighted WG inverse. These representations are expressed in terms of matrix powers as well as in terms of matrix products involving only the Moore–Penrose inverse. In addition, a new characterization of the W-weighted WG inverse is presented by using a rank equation.Fil: Ferreyra, David Eduardo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Físico-Químicas y Naturales. Departamento de Matemática; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Orquera, Valentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas, Físico-Químicas y Naturales. Departamento de Matemática; ArgentinaFil: Thome Coppo, Néstor Javier. Universidad Politécnica de Valencia; Españ

Parametrized solutions X of the system AXA = AEA and A^k EAX = XAEA^k for a matrix A having index k

[EN] Let A and E be n x n given complex matrices. This paper provides a necessary and sufficient condition for the solvability to the matrix equation system given by AXA = AEA and A(k) EAX = XAEA(k) , for k being the index of A. In addition, its general solution is derived in terms of a G-Drazin inverse of A. As consequences, new representations are obtained for the set of all G-Drazin inverses; some interesting applications are also derived to show the importance of the obtained formulas.Partially supported by Universidad Nacional de Rio Cuarto (grant PPI 18/C472) and CONICET (grant PIP 112-201501-00433CO). Partially supported by Universidad Nacional de La Pampa, Facultad de Ingenieria (grant Resol. Nro. 155/14). Partially supported by Ministerio de Economia, Industria y Competitividad of Spain (grant Red de Excelencia MTM2017-90682-REDT) and by Universidad Nacional del Sur of Argentina (grant 24/L108).Ferreyra, DE.; Latanzi, M.; Levis, F.; Thome, N. (2019). Parametrized solutions X of the system AXA = AEA and A^k EAX = XAEA^k for a matrix A having index k. The Electronic Journal of Linear Algebra. 35:503-510. https://doi.org/10.13001/1081-3810.4051S5035103

Acceso a la información : hacia la democratización de la administración pública

The work is structured in three sections. In the first one, the intention is to\ndelineate the concept of the right of access to public information and the complexities\nderived from it following what was resolved and legislated in different systems. In the\nsecond one, the Argentinean normative structure and its deficits are analyzed. In the\nthird section and based on the initial reflections, final considerations and suggestions\nare developed.Fil: Ferreyra, Leandro Eduardo. Universidad de Buenos Aires. Facultad de Derecho; ArgentinaEl trabajo se encuentra estructurado en tres partes. En la primera se intenta\ndelimitar un concepto de derecho de acceso a la información pública y de las complejidades\nderivadas del mismo de acuerdo a lo resuelto y normado en diversos sistemas.\nEn la segunda, se analiza el régimen argentino y sus déficits. En la tercera, se esbozan\nconsideraciones y propuestas en base a lo expuesto anteriormente

IMPACTO DEL DESEQUILIBRIO DE CLASES EN EL ENTRENAMIENTO DE REDES NEURONALES CONVOLUCIONALES EN PROBLEMAS MULTI-CLASE (IMPACT OF CLASS IMBALANCE IN THE TRAINING OF CONVOLUTIONAL NEURAL NETWORKS FOR MULTI-CLASS PROBLEMS)

El problema del desequilibrio de clases en el aprendizaje automático, se presenta cuando el conjunto de entrenamiento subyacente está compuesto por un número desigual de muestras para cada clase, lo que ocasiona que datos de algunas clases dominen claramente. Aparentemente, la mayoría de los modelos clasificadores aprenden a clasificar dichos conjuntos de datos; sin embargo, presentan un rendimiento de generalización deficiente debido a un fuerte sesgo hacia las clases mayoritarias. En este artículo, se presenta un estudio sistemático dirigido a comprender como afecta el problema del desequilibrio de clases al rendimiento de una red neuronal convolucional entrenada para una tarea de clasificación de imágenes, y se presenta una metodología para corregir el sobreentrenamiento e incrementar la generalización de la red.The class imbalance problem in machine learning occurs when the underlying training set is composed of unequal number of samples for each class, which causes data from some classes to clearly dominate. Apparently, most classifiers learn to classify such datasets, however, they show poor generalization performance due to a strong bias towards the majority classes. This article presents a systematic study aimed at understanding how the class imbalance problem affects the performance of a convolutional neural network which has been trained for an image classification task. Also, we present a methodology to correct the overtraining and increase the generalization performance of the network

Identification of a Bifunctional Maize C- and O-Glucosyltransferase

Flavonoids accumulate in plant vacuoles usually as O-glycosylated derivatives, but several species can also synthesize flavonoid C-glycosides. Recently, we demonstrated that a flavanone 2-hydroxylase (ZmF2H1, CYP93G5) converts flavanones to the corresponding 2-hydroxy derivatives, which are expected to serve as substrates for C-glycosylation. Here, we isolated a cDNA encoding a UDP-dependent glycosyltransferase (UGT708A6), and its activity was characterized by in vitro and in vivo bioconversion assays. In vitro assays using 2-hydroxyflavanones as substrates and in vivo activity assays in yeast co-expressing ZmF2H1 and UGT708A6 show the formation of the flavones C-glycosides. UGT708A6 can also O-glycosylate flavanones in bioconversion assays in Escherichia coli as well as by in vitro assays with the purified recombinant protein. Thus, UGT708A6 is a bifunctional glycosyltransferase that can produce both C- and O-glycosidated flavonoids, a property not previously described for any other glycosyltransferase.Fil: Falcone Ferreyra, María Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Centro de Estudios Fotosintéticos y Bioquímicos (i); ArgentinaFil: Rodriguez, Eduardo Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Casas, María Isabel. The Ohio State University. Plant Biotechnology Center. Department Plant Cell Molecular Biology; Estados UnidosFil: Labadie, Guillermo Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Química Rosario; ArgentinaFil: Grotewold, Erich. The Ohio State University. Plant Biotechnology Center; Estados UnidosFil: Casati, Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Centro de Estudios Fotosintéticos y Bioquímicos (i); Argentin