PVT-Robust CMOS Programmable Chaotic Oscillator: Synchronization of Two 7-Scroll Attractors

Designing chaotic oscillators using complementary metal-oxide-semiconductor (CMOS) integrated circuit technology for generating multi-scroll attractors has been a challenge. That way, we introduce a current-mode piecewise-linear (PWL) function based on CMOS cells that allow programmable generation of 2–7-scroll chaotic attractors. The mathematical model of the chaotic oscillator designed herein has four coefficients and a PWL function, which can be varied to provide a high value of the maximum Lyapunov exponent. The coefficients are implemented electronically by designing operational transconductance amplifiers that allow programmability of their transconductances. Design simulations of the chaotic oscillator are provided for the 0.35μ m CMOS technology. Post-layout and process–voltage–temperature (PVT) variation simulations demonstrate robustness of the multi-scroll chaotic attractors. Finally, we highlight the synchronization of two seven-scroll attractors in a master–slave topology by generalized Hamiltonian forms and observer approach. Simulation results show that the synchronized CMOS chaotic oscillators are robust to PVT variations and are suitable for chaotic secure communication applications.Universidad Autónoma de Tlaxcala CACyPI-UATx-2017Program to Strengthen Quality in Educational Institutions C/PFCE-2016-29MSU0013Y-07-23National Council for Science and Technology 237991 22284

Pathological element-based active device models and their application to symbolic analysis

This paper proposes new pathological element-based active device models which can be used in analysis tasks of linear(ized) analog circuits. Nullators and norators along with the voltage mirror-current mirror (VM-CM) pair (collectively known as pathological elements) are used to model the behavior of active devices in voltage-, current-, and mixed-mode, also considering parasitic elements. Since analog circuits are transformed to nullor-based equivalent circuits or VM-CM pairs or as a combination of both, standard nodal analysis can be used to formulate the admittance matrix. We present a formulation method in order to build the nodal admittance (NA) matrix of nullor-equivalent circuits, where the order of the matrix is given by the number of nodes minus the number of nullors. Since pathological elements are used to model the behavior of active devices, we introduce a more efficient formulation method in order to compute small-signal characteristics of pathological element-based equivalent circuits, where the order of the NA matrix is given by the number of nodes minus the number of pathological elements. Examples are discussed in order to illustrate the potential of the proposed pathological element-based active device models and the new formulation method in performing symbolic analysis of analog circuits. The improved formulation method is compared with traditional formulation methods, showing that the NA matrix is more compact and the generation of nonzero coefficients is reduced. As a consequence, the proposed formulation method is the most efficient one reported so far, since the CPU time and memory consumption is reduced when recursive determinant-expansion techniques are used to solve the NA matrix.Promep-Mexico UATLX-PTC-088Junta de Andalucía TIC-2532Ministerio de Educación y Ciencia TEC2007-67247, TEC2010-14825UC-MEXUS-CONACyT CN-09-31

Electrochemical and photo-electrochemical processes of Methylene blue oxidation by Ti/TiO2 electrodes modified with Fe-allophane

Indexación: Scopus.This work reports the degradation of methylene blue (MB) on Ti/TiO2 and Ti/TiO2/Fe-allophane electrodes in a pH 3 using 0.1 M Na2SO4 as support electrolyte. SEM micrographs show a homogeneous distribution of TiO2 over the whole electrode surface forming nanotubes and nanopores. Fe-allophane modified electrode shows the formation of large-grains agglomerate on the electrode surface due to allophane, which provides a greater surface area to the electrode due to meso and micropore structures. Preliminary cyclic voltammetry show that Ti/TiO2 has the typical voltammetric response due to Ti(III)/Ti(IV) pair. Diffusional problems were observed through of the film when the electrode is modified with Fe-allophane modifying the quasi-reversible process Ti(III)/Ti(IV). Different kind of methodologies in the degradation process were used: Electrochemistry (EC), Photochemistry (PC), Photoelectrochemistry (PEC) and Adsorption (Ads). These methods were developing to discard any reaction or interaction that is not of interest. On Ti/TiO2 with PC and Ads methodologies was not observed any activity to MB degradation showing that is not photosensitive and that the interaction between this and surface electrode is low. But with EC and PEC degradation to 55% is reached after 3 hours of electrolysis. With Ti/TiO2-Fe-allophane electrodes are observed a higher activity for all methodologies. The PC and Ads methods show that the MB degradation reaches to ∼20 % of the initial concentration. As mentioned above, the PC and Ads processes no show degradation on Ti/TiO2, therefore the degradation it only due to the adsorption of MB in/on allophane coat behaving as concentrator matrix. A lower improvement is observed with EC process when is incorporated Ti/TiO2-Fe-allophane is due to the barrier of the electrode surface by oxidation products. With PEC is reached the higher degradation value of ∼88 %, showing an improvement of the degradation with the presence of Fe-allophane. The results indicate that the main role of Fe-allophane on the electrode is similar to a concentrator matrix.http://ref.scielo.org/shz7t

Enseñanza de la Topología y Geometría en los niveles elementales

Tanto las nociones topológicas como las geométricas son un componente particularmente esencial en el desarrollo de la conciencia de los niños. Muchos autores están de acuerdo en la importancia de este conocimiento, pero están en disputa sobre cómo debe estructurarse. Estamos dividiendo el trabajo en dos partes: en la primera tratamos el contenido y ofrecemos un esquema de aprendizaje; En el segundo, ofrecemos orientación didáctica

Cutaneous lesions associated to multiple endocrine neoplasia syndrome type 1

Original article[Abstract] Background  Multiple endocrine neoplasia type 1 (MEN1) is a genetic disease that predisposes to endocrine tumour development. Some cutaneous lesions (angiofibromas, collagenomas, melanosis guttaca, lipomas, melanomas, ‘cafe au lait macules’) have been associated to this syndrome. We compare the prevalence of cutaneous lesion in affected patients with their non‐carrier relatives. Patients and method  We studied 9 patients with MEN1 and 20 non‐carrier, first‐degree relatives. Genetic screening was realized in all of them. Patients were examined by dermatologist, and biopsy was performed when necessary. Results  Patients with MEN1 presented hyperparathyroidism (100%), neuroendocrine tumours of pancreas (66%) and pituitary adenomas (44%); their relatives were free of endocrine features of MEN1. The studied cutaneous lesions were more prevalent in affected patients than in non‐carriers (55.5% vs. 25%; P = 0.029). Odds ratio of developing cutaneous lesions in MEN1 patients was 6.6 (95% confidence interval, 1.09–40.43). The frequency of angiofibromas was lower (22.2%) than the reported in other studies (43–88%), and we did not find any collagenoma. Conclusions  MEN1 is associated to some cutaneous lesions and could be useful for detecting MEN1 carriers in an affected family. Cutaneous lesions should be assessed in MEN1 patients.Instituto de Salud Carlos III; FIS PI051024Xunta de Galicia; PGIDT05PXIC91605P

Estudio de métodos de selección de conceptos

Ponencia presentada en el XI Congreso Internacional de Ingeniería de Proyectos celebrado en Lugo en el año 2007Best product concept selection is of prime importance to direct the marketing launching process. This selection is one of the most difficult and critical decisions for the designer, and an inappropriate concept selection can rarely be compensated on a later stage of the process, increasing the cost of redesign at the same time. Nowadays, there are several concept selection and evaluation methods that allow to reduce the failure risk. The objective of this communication is to carry an analysis of those different methods to evaluate and select concepts, with the aim of reinforcing the methodology developed by the authors on 2006.La elección del mejor concepto de producto es vital para encaminar el proceso de lanzamiento del mismo al mercado. Dicha elección es una de las cuestiones más críticas y difíciles que tiene que tomar el diseñador. Una elección inadecuada de concepto raramente puede ser compensada en posteriores fases del proceso incrementando a su vez el coste de rediseño. En la actualidad existen diferentes métodos de selección y evaluación de concepto que permiten reducir el riesgo de fracaso del proceso. El objetivo de esta comunicación es realizar un estudio de los diferentes métodos que existen en la actualidad para la evaluar y seleccionar conceptos de producto, con el fin de reforzar el método desarrollado por los autores en el año 2006

Screen-printed electrode-based electrochemical detector coupled with in-situ ionic-liquid-assisted dispersive liquid–liquid microextraction for determination of 2,4,6-trinitrotoluene

A novel method is reported, whereby screen-printed electrodes (SPELs) are combined with dispersive liquid–liquid microextraction. In-situ ionic liquid (IL) formation was used as an extractant phase in the microextraction technique and proved to be a simple, fast and inexpensive analytical method. This approach uses miniaturized systems both in sample preparation and in the detection stage, helping to develop environmentally friendly analytical methods and portable devices to enable rapid and onsite measurement. The microextraction method is based on a simple metathesis reaction, in which a water-immiscible IL (1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, [Hmim][NTf2]) is formed from a water-miscible IL (1-hexyl-3-methylimidazolium chloride, [Hmim][Cl]) and an ion-exchange reagent (lithium bis[(trifluoromethyl)sulfonyl]imide, LiNTf2) in sample solutions. The explosive 2,4,6-trinitrotoluene (TNT) was used as a model analyte to develop the method. The electrochemical behavior of TNT in [Hmim][NTf2] has been studied in SPELs. The extraction method was first optimized by use of a two-step multivariate optimization strategy, using Plackett–Burman and central composite designs. The method was then evaluated under optimum conditions and a good level of linearity was obtained, with a correlation coefficient of 0.9990. Limits of detection and quantification were 7 μg L−1 and 9 μg L−1, respectively. The repeatability of the proposed method was evaluated at two different spiking levels (20 and 50 μg L−1), and coefficients of variation of 7 % and 5 % (n = 5) were obtained. Tap water and industrial wastewater were selected as real-world water samples to assess the applicability of the method.The authors would like to thank the Spanish Ministry of Science and Innovation (project n. CTQ2011-23968), Generalitat Valenciana (Spain) (projects n. ACOMP/2013/072 and PROMETEO/2012/038) and Universidad de Alicante (Spain) (project n. GRE12-45) for the financial support. E.F. also thanks Generalitat Valenciana for her fellowship

Laser transmission welding of Acrylonitrile-Butadiene-Styrene (ABS) using a tailored high power diode-laser optical fiber coupled system

Laser transmission welding (LTW) of polymers is a direct bonding technique which is already used in different industrial applications sectors such as automobile, microfluidic, electronic and biomedicine. This technique offers several advantages over conventional methods, especially when a local deposition of energy and minimum thermal distortions are required. In LTW one of the polymeric materials needs to be transparent to the laser wavelength and the second part needs to be designed to be absorbed in IR spectrum. This report presents a study of laser weldability of ABS (acrylonitrile/butadiene/styrene) filled with two different concentrations of carbon nanotubes (0.01% and 0.05% CNTs). These additives are used as infrared absorbing components in the laser welding process, affecting the thermal and optical properties of the material and, hence, the final quality of the weld seam. A tailored laser system has been designed to obtain high quality weld seams with widths between 0.4 and 1.0mm. It consists of two diode laser bars (50W per bar) coupled into an optical fiber using a non-imaging solution: equalization of the beam quality factor (M2 ) in the slow and fast axes by a pair of micro step-mirrors. The beam quality factor has been analyzed at different laser powers with the aim to guarantee a coupling efficiency to the multimode optical fiber. The power scaling is carried out by means of multiplexing polarization technique. The analysis of energy balance and beam quality is performed in two linked steps: first by means ray tracing simulations (ZEMAX® ) and second, by validation. Quality of the weld seams is analyzed in terms of the process parameters (welding speed, laser power and clamping pressure) by visual and optical microscope inspections. The optimum laser power range for three different welding speeds is determinate meanwhile the clamping pressure is held constant. Additionally, the corresponding mechanical shear tests were carried out to analyze the mechanical properties of the weld seams. This work provides a detailed study concerning the effect of the material microstructure and laser beam quality on the final weld formation and surface integrity

Optical constants of evaporation-deposited silicon monoxide films in the 7.1-800 eV photon energy range

8 págs.; 11 figs.The transmittance of silicon monoxide films prepared by thermal evaporation was measured from 7.1 to 800 eV and used to determine the optical constants of the material. SiO films deposited onto C-coated microgrids in ultrahigh vacuum conditions were measured in situ from 7.1 to 23.1 eV. Grid-supported SiO films deposited in high vacuum conditions were characterized ex situ from 28.5 to 800 eV. At each photon energy, transmittance, and thickness data were used to calculate the extinction coefficient k. The obtained k values combined with data from the literature, and with interpolations and extrapolations in the rest of the electromagnetic spectrum provided a complete set of k values that was used in a Kramers-Kronig analysis to obtain the real part of the index of refraction, n. Two different sum-rule tests were performed that indicated good consistency of the data. © 2009 American Institute of Physics.This work was supported by the National Programme for Space Research, Subdirección General de Proyectos de Investigación, Ministerio de Ciencia y Tecnología, Project Nos. ESP2002-01391 and ESP2005-02650. This work was also performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Berkeley National Laboratory under Contract No. DE-AC03-76F00098 and by the University of California Lawrence Livermore National Laboratory under Contract No. DE-AC52- 07NA27344. M.F.-P. is thankful to Consejo Superior de Investigaciones Científicas Spain for funding under the Programa I3P Contract No. I3P-BPD2004, partially supported by the European Social Fund. M.V.-D. acknowledges financial support from a FPI Contract No. BES-2006-14047 fellowship.Peer Reviewe

The Structural Architecture of an Infectious Mammalian Prion Using Electron Cryomicroscopy

The structure of the infectious prion protein (PrPSc), which is responsible for Creutzfeldt-Jakob disease in humans and bovine spongiform encephalopathy, has escaped all attempts at elucidation due to its insolubility and propensity to aggregate. PrPSc replicates by converting the non-infectious, cellular prion protein (PrPC) into the misfolded, infectious conformer through an unknown mechanism. PrPSc and its N-terminally truncated variant, PrP 27-30, aggregate into amorphous aggregates, 2D crystals, and amyloid fibrils. The structure of these infectious conformers is essential to understanding prion replication and the development of structure-based therapeutic interventions. Here we used the repetitive organization inherent to GPI-anchorless PrP 27-30 amyloid fibrils to analyze their structure via electron cryomicroscopy. Fourier-transform analyses of averaged fibril segments indicate a repeating unit of 19.1 Å. 3D reconstructions of these fibrils revealed two distinct protofilaments, and, together with a molecular volume of 18,990 Å3, predicted the height of each PrP 27-30 molecule as ~17.7 Å. Together, the data indicate a four-rung β-solenoid structure as a key feature for the architecture of infectious mammalian prions. Furthermore, they allow to formulate a molecular mechanism for the replication of prions. Knowledge of the prion structure will provide important insights into the self-propagation mechanisms of protein misfolding