Universidad Técnica Federico Santa María

In the low voltage converter range, 3-phase 3-level VSC topologies are not wide spread in industry because of the increased part count and higher costs, although they are more efficient for higher switching frequencies. In this paper an alternative 3-level topology referred to as T-type is presented, which is very high efficient for medium switching frequencies (4-20 kHz). Additionally, it is shown that the total silicon chip area of a 3-level topology can be lower than in a 2-level topology since the losses are distributed over more components leading to only a small increase in the junction temperature. This allows for the design of a chip area and cost optimized 3-level bridge leg module for the mass market.

Sterile neutrinos with masses in the range of 1--100 GeV have been searched for in a variety of experiments. Here, we discuss the prospects of searching for sterile neutrinos at the LHC using displaced vertices. Two different cases are discussed: (i) the standard model extended with sterile neutrinos, and (ii) right-handed neutrinos in a left-right symmetric extension of the standard model. A dedicated displaced vertex search will allow us to probe parts of the parameter space not accessible to other searches, but both cases will require a large luminosity.

Avocado (Persea americana Mill) is a native American fruit. Its industrial processing generates a large number of wastes (leaves, peels, and seeds). These wastes are a source of bioactive compounds which have been attributed biological activities. We aim to compile scientific research on bioactive compounds of avocado pulp and wastes and their potential biological properties. Main bioactive compounds identified in pulp and wastes are polyphenols, carotenoids, tocopherols, and phytosterols. Thus, wastes extracts have reported numerous biological activities, e.g., antimicrobial, anti–inflammatory, anticancer, antidiabetic, antihypertensive. Therefore, potential applications in food and pharmaceutical industries can be issued.

In this paper, model-predictive control is used as a framework for implementing a quasi-time-optimal speed controller for a permanent-magnet synchronous motor. The scheme consists of an inner predictive torque control, which makes use of the full actuation range provided by a two-level voltage source inverter, although with the use of pulsewidth modulation. An outer speed controller, based on classical results for the time-optimal control of the double integrator, constitutes a good example application of the proposed torque controller. The overall scheme achieves both fast transient dynamics (as fast as the physics of the system and the control constraints allow) and acceptable steady-state performance.

Leptoquark-Higgs interactions induce mixing between leptoquark (LQ) states with different chiralities once the electroweak symmetry is broken. In such LQ models Majorana neutrino masses are generated at 1-loop order. Here we calculate the neutrino mass matrix and explore the constraints on the parameter space enforced by the assumption that LQ-loops explain current neutrino oscillation data. LQs will be produced at the CERN LHC, if their masses are at or below the TeV scale. Since the fermionic decays of LQs are governed by the same Yukawa couplings, which are responsible for the nontrivial neutrino mass matrix, several decay branching ratios of LQ states can be predicted from measured neutrino data. Especially interesting is that large lepton flavor violating rates in muon and tau final states are expected. In addition, the model predicts that, if kinematically possible, heavier LQs decay into lighter ones plus either a standard model Higgs boson or a ${Z}^{0}/{W}^{\ifmmode\pm\else\textpm\fi{}}$ gauge boson. Thus, experiments at the LHC might be able to exclude the LQ mechanism as an explanation of neutrino data.

Let K(Q be the set of univalent functions in the unit disk D which are convex in the direction eip . We determine the set of analytic functions g in D which preserve K(9) under the Hadamard product, i.e., g * f e K(p) whenever f e X(d. This result contains as a special case the proof of a conjecture of Goodman and Saff about l((rp) and solves partially a multiplier problem concerning convex univalent harmonic functions in D, posed by Clunie and Sheil-Small.

We analyze the branching ratios of $B\ensuremath{\rightarrow}{D}^{(*)}{D}_{s0}^{*}({D}_{s1})$ decays using the factorization hypothesis. The $B\ensuremath{\rightarrow}{D}^{(*)}$ transition form factors are taken from a model-independent analysis done by Caprini, Lellouch, and Neubert based on heavy quark spin symmetry and dispersive constraints, including short-distance and power corrections. The leptonic decay constants ${f}_{{D}_{s0}^{*}}$ and ${f}_{{D}_{s1}}$ are calculated assuming a molecular structure for the ${D}_{s0}^{*}$ and ${D}_{s1}$ mesons. The calculated branching ratios of $B$-meson two-body decays are compared with experimental data and other theoretical results.

The experimental implementation and performance analysis of control techniques applied to an indirect matrix converter are presented here, to improve the input current behaviour under resonances and harmonics distortions. The control strategies are based on model predictive control, which uses the commutation state of the converter in the subsequent sampling time, according to an optimisation algorithm given by a simple cost function and the discrete system model. Experimental results with a laboratory prototype are provided in order to validate the different control schemes, and the effects of a distorted source voltage and filter resonance are analysed.

Recently, carbon allotropes were shown to play a key role in energy harvesting and as hydrophobic coatings on metal alloys. We have designed octylamine-functionalized graphene oxide materials for energy harvesting and as an anti-corrosion coating for metal alloy protection in a 3.5% NaCl medium. The material has been characterized by different techniques to confirm the structure and composition of the modified graphene oxide sheet: FTIR spectroscopy, XRD, Raman spectroscopy, FESEM and TEM. The electrochemical stability and corrosion inhibition efficiency were studied by electrochemical methods. The electrochemical stability increased with an increase in the applied voltage up to 500 mV, and the corrosion inhibition efficiency was shown to be 73%. The coating stability studies showed a long stability time in the corrosion medium.

Colorectal cancer (CRC) was the second-ranked worldwide type of cancer during 2020 due to the crude mortality rate of 12.0 per 100000 inhabitants. It can be prevented if glandular tissue (adenomatous polyps) is detected early. Colonoscopy has been strongly recommended as a screening test for both early cancer and adenomatous polyps. However, it has some limitations that include the high polyp miss rate for smaller (< 10 mm) or flat polyps, which are easily missed during visual inspection. Due to the rapid advancement of technology, artificial intelligence (AI) has been a thriving area in different fields, including medicine. Particularly, in gastroenterology AI software has been included in computer-aided systems for diagnosis and to improve the assertiveness of automatic polyp detection and its classification as a preventive method for CRC. This article provides an overview of recent research focusing on AI tools and their applications in the early detection of CRC and adenomatous polyps, as well as an insightful analysis of the main advantages and misconceptions in the field.

Substantial advances in our knowledge of the fauna of the Caribbean area

We present electronic structure calculations of twisted double bilayer graphene (TDBG): a tetralayer graphene structure composed of two AB-stacked graphene bilayers with a relative rotation angle between them. Using first-principles calculations, we find that TDBG is semiconducting with a band gap that depends on the twist angle, that can be tuned by an external electric field. The gap is consistent with TDBG symmetry and its magnitude is related to surface effects, driving electron transfer from outer to inner layers. The surface effect competes with an energy upshift of localized states at inner layers, giving rise to the peculiar angle dependence of the band gap, which reduces at low angles. For these low twist angles, the TDBG develops flat bands, in which electrons in the inner layers are localized at the AA regions, as in twisted bilayer graphene.

Currently, the use of information and communication technologies (ICT) in education does not conclusively demonstrate significant effects on learning. However, not all ICT usage models are designed to affect student outcomes. Therefore, to accurately study the impact of ICT, the concept of an educational programme supported by ICT must first be defined. The authors propose the ICT for Education (ICT4E) programme, an evidence-based framework to determine a model’s ability to produce improvements before having to evaluate its results. The framework has four components: implementation, intervention, transference and total cost. Based on an explicit definition of the outcomes pursued by a given programme, this framework supports the design of its activities to promote sustainable changes in pedagogical practices in schools and calculate the programme’s total cost. The authors illustrate this with a programme implemented in six countries. In Chile, the ICT4E programme forms part of the policy for educational technology, evaluating the effectiveness and scalability of such initiatives.

We have recently reported that mouse embryonic stem cells (mESCs) are deficient in expressing type I interferons (IFNs) in response to viral infection and synthetic viral RNA analogs (Wang, R., Wang, J., Paul, A. M., Acharya, D., Bai, F., Huang, F., and Guo, Y. L. (2013) J. Biol. Chem. 288, 15926-15936). Here, we report that mESCs are able to respond to type I IFNs, express IFN-stimulated genes, and mediate the antiviral effect of type I IFNs against La Crosse virus and chikungunya virus. The major signaling components in the IFN pathway are expressed in mESCs. Therefore, the basic molecular mechanisms that mediate the effects of type I IFNs are functional in mESCs; however, these mechanisms may not yet be fully developed as mESCs express lower levels of IFN-stimulated genes and display weaker antiviral activity in response to type I IFNs when compared with fibroblasts. Further analysis demonstrated that type I IFNs do not affect the stem cell state of mESCs. We conclude that mESCs are deficient in type I IFN expression, but they can respond to and mediate the cellular effects of type I IFNs. These findings represent unique and uncharacterized properties of mESCs and are important for understanding innate immunity development and ESC physiology.

Two control strategies that allow the control of source and load currents for direct matrix converters are presented in this study. Both methods use the switching state of the converter in the subsequent sampling time, based on an optimisation algorithm given by a simple cost function and the discrete system model. The control goals include regulation of load currents according to an arbitrary reference and good tracking of the source currents to their references. In the first method, the input current reference is given as a function of the instantaneous active power. In the second case, the source current reference is given as a function of the output current reference and system parameters. Experimental results with an experimental prototype support the theoretical approach.

The aim of this study is to determine the factors that affect working capital management in Latin American companies. Using an unbalanced panel data analysis for companies quoted in five Latin American capital markets it is shown that companies in Argentina, Brazil, Chile and Mexico are holding cash excesses, which could destroy firm value. Results show that the industry cash conversion cycle, the company market power, its future sales and country risk have an influence on the way Latin American companies manage their working capital with significant differences among countries in the region.

Abstract The ATLAS experiment has developed extensive software and distributed computing systems for Run 3 of the LHC. These systems are described in detail, including software infrastructure and workflows, distributed data and workload management, database infrastructure, and validation. The use of these systems to prepare the data for physics analysis and assess its quality are described, along with the software tools used for data analysis itself. An outlook for the development of these projects towards Run 4 is also provided.

Correction for 'A comparative study of Ir(iii) complexes with pyrazino[2,3-f][1,10]phenanthroline and pyrazino[2,3-f][4,7]phenanthroline ligands in light-emitting electrochemical cells (LECs)' by Iván González et al., Dalton Trans., 2015, 44, 14771-14781.

Pyrazolo[3,4-<italic>b</italic>]pyridines derivatives have been synthesized <italic>via</italic> one-pot condensation of 3-methyl-1-phenyl-1<italic>H</italic>-pyrazolo-5-amine (<bold>1</bold>), paraformaldehyde (<bold>2</bold>) and β-diketones (<bold>3</bold>) under microwave irradiation in aqueous media catalyzed by InCl₃.

The objective of this review paper is to summarize the main properties of the spatial ARMA models and describe some of the well-known methods used in image filtering based on estimation of spatial autoregressive models. A new proposal based on robust RA estimation is also presented. Previous studies have shown that under additive outliers the RA estimator is resistant to a small percentage of contamination and behaves better than the LS, M, and GM estimators. A discussion about how well these models fit to a digital image is presented. Some applications using real images are presented to illustrate how an image is filtered in practice.