Artifact removal in magnetoencephalogram background activity with independent component analysis

The aim of this study was to assess whether independent component analysis (ICA) could be valuable to remove power line noise, cardiac, and ocular artifacts from magnetoencephalogram (MEG) background activity. The MEGs were recorded from 11 subjects with a 148-channel whole-head magnetometer. We used a statistical criterion to estimate the number of independent components. Then, a robust ICA algorithm decomposed the MEG epochs and several methods were applied to detect those artifacts. The whole process had been previously tested on synthetic data. We found that the line noise components could be easily detected by their frequency spectrum. In addition, the ocular artifacts could be identified by their frequency characteristics and scalp topography. Moreover, the cardiac artifact was better recognized by its skewness value than by its kurtosis one. Finally, the MEG signals were compared before and after artifact rejection to evaluate our method.     

Analysis of network function sharing in Content Delivery Network-as-a-service slicing scenarios

Video content consumption is currently dominating the mix of traffic observed in Internet service provider (ISP) networks. The distribution of that content is usually performed by means of content delivery network (CDN) caches storing and delivering multimedia. The advent of virtualization is calling attention to the CDN providers as a use case for virtualizing the cache function. In parallel, there is a trend for sharing network infrastructures as a way of reducing deployment costs by ISPs. Then, an interesting scenario emerges when considering the possibility of sharing virtualized cache functions among ISPs which are sharing a common physical infrastructure, mostly considering that those ISPs offer similar video content catalogs to end users. Furthermore, when deciding to share the caches among ISPs, it is interesting to understand the impacts due to limiting the storage capacity at the edge sites. This paper investigates through simulations the potential efficiencies that can be achieved when sharing a virtual cache function if compared with the classical approach of independent virtual caches operated per ISP, as well as the implications of limiting the storage capacity of the caches at the edge.     

Recent Advances in Calcium-Based Anticancer Nanomaterials Exploiting Calcium Overload to Trigger Cell Apoptosis

Calcium ion is vital for the regulation of many cellular functions and serves as a second messenger in the signal transduction pathways. Once the intracellular Ca²⁺ level exceeds the tolerance of cells (called Ca²⁺ overload), oxidative stress, mitochondrial damage, and cell/mitochondria apoptosis happen. Therefore, Ca²⁺ overload has started to be deeply exploited as a new strategy for cancer therapy due to its high efficiency and satisfactory safety. This review aims to highlight the recent development of Ca²⁺-based nanomaterials (such as Ca₃(PO₄)₂, CaCO₃, CaO₂, CaH₂, CaS, and others) able to trigger intracellular Ca²⁺ overload and apoptosis in cancer therapy. The intracellular mechanisms of varied Ca²⁺-based nanomaterials and the different types of strategies to enhance Ca²⁺ overload are discussed in detail. Moreover, the design of more efficient Ca²⁺ overload-mediated cancer therapies is prospected mainly based on 1) the enhanced cellular uptake by surface modification and morphology optimization of nanomaterials, 2) the accelerated Ca²⁺ release from nanomaterials by increasing the intracellular H⁺ level and by photothermal effect, and 3) the overload maintenance by Ca²⁺ efflux inhibition, Ca²⁺ influx promotion, or promoting Ca²⁺ release from the endoplasmic reticulum.     

The chemical and structural origin of efficient p-type doping in P3HT

We investigate the chemical and structural properties of solution-processed thin films of P3HT blended with p-type dopant F4TCNQ. The maximum in-plane electrical conductivity of doped films is observed at a molar doping fraction of 0.17, in agreement with the binding mechanism of F4TCNQ:P3HT complexes. Through the use of X-ray diffraction, a previously unreported crystalline phase is observed for P3HT films doped above a critical threshold concentration. This crystalline phase involves the incorporation of F4TCNQ molecules into ordered polymer regions and ultimately improves charge dissociation, leading to higher carrier density in thin film. Finally, optical absorption and X-ray diffraction reveal that the chemical state of P3HT in solution has a dramatic impact on the electrical and structural properties of the blended films.     

Reputation based selfishness prevention techniques for mobile ad-hoc networks

Mobile ad-hoc networks require nodes to cooperate in the relaying of data from source to destination. However, due to their limited resources, selfish nodes may be unwilling to forward packets, which can deteriorate the multi-hop connectivity. Different reputation-based protocols have been proposed to cope with selfishness in mobile ad-hoc networks. These protocols utilize the watchdog detection mechanism to observe the correct relaying of packets, and to compile information about potential selfish nodes. This information is used to prevent the participation of selfish nodes in the establishment of multi-hop routes. Despite its wide use, watchdog tends to overestimate the selfish behavior of nodes due to the effects of radio transmission errors or packet collisions that can be mistaken for intentional packet drops. As a result, the availability of valid multi-hop routes is reduced, and the overall performance deteriorates. This paper proposes and evaluates three detection techniques that improve the ability of selfishness prevention protocols to detect selfish nodes and to increase the number of valid routes.     

Design and realization of transparent solar modules based on luminescent solar concentrators integrating nanostructured photonic crystals

Herein, we present a prototype of a photovoltaic module that combines a luminescent solar concentrator integrating one‐dimensional photonic crystals and in‐plane CuInGaSe₂ (CIGS) solar cells. Highly uniform and wide‐area nanostructured multilayers with photonic crystal properties were deposited by a cost‐efficient and scalable liquid processing amenable to large‐scale fabrication. Their role is to both maximize light absorption in the targeted spectral range, determined by the fluorophore employed, and minimize losses caused by emission at angles within the escape cone of the planar concentrator. From a structural perspective, the porous nature of the layers facilitates the integration with the thermoplastic polymers typically used to encapsulate and seal these modules. Judicious design of the module geometry, as well as of the optical properties of the dielectric mirrors employed, allows optimizing light guiding and hence photovoltaic performance while preserving a great deal of transparency. Optimized in‐plane designs like the one herein proposed are of relevance for building integrated photovoltaics, as ease of fabrication, long‐term stability and improved performance are simultaneously achieved. © 2015 The Authors. Progress in Photovoltaics: Research and Applications published by John Wiley & Sons Ltd.     

Properties and Printability of Inkjet and Screen-Printed Silver Patterns for RFID Antennas

We report the modeling, and geometrical and electrical characterization, of inkjet and screen-printed patterns on different polymeric substrates for use as antennas in radio-frequency identification (RFID) applications. We compared the physical and electrical characteristics of two silver nanoparticle-based commercial inkjet-printable inks and one screen-printable silver paste, when deposited on polyimide (PI), polyethylene terephthalate (PET), and polyetherimide (PEI) substrates. First, the thickness of the inkjet-printed patterns was predicted by use of an analytical model based on printing conditions and ink composition. The predicted thickness was confirmed experimentally, and geometrical characterization of the lines was completed by measuring the root-mean-square roughness of the patterns. Second, direct-current electrical characterization was performed to identify the printing conditions yielding the lowest resistivity and sheet resistance. The minimum resistivity for the inkjet-printing method was 8.6 ± 0.8 μΩ cm, obtained by printing four stacked layers of one of the commercial inks on PEI, whereas minimum resistivity of 44 ± 7 μΩ cm and 39 ± 4 μΩ cm were obtained for a single layer of screen-printed ink on polyimide (PI) with 140 threads/cm mesh and 90 threads/cm mesh, respectively. In every case, these minimum values of resistivity were obtained for the largest tested thickness. Coplanar waveguide transmission lines were then designed and characterized to analyze the radio-frequency (RF) performance of the printed patterns; minimum transmission losses of 0.0022 ± 0.0012 dB/mm and 0.0016 ± 0.0012 dB/mm measured at 13.56 MHz, in the high-frequency (HF) band, were achieved by inkjet printing on PEI and screen printing on PI, respectively. At 868 MHz, in the ultra-high-frequency band, the minimum values of transmission loss were 0.0130 ± 0.0014 dB/mm for inkjet printing on PEI and 0.0100 ± 0.0014 dB/mm for screen printing on PI. Although the resistivity achieved is lower for inkjet printing than for screen printing, RF losses for inkjetted patterns were larger than for screen-printed patterns, because thicker layers were obtained by screen printing. Finally, several coil inductors for the HF band were also fabricated by use of both printing techniques, and were used as antennas for semi-passive smart RFID tags on plastic foil capable of measuring temperature and humidity.     

Thermal characterisation of power devices during transient operation

An experimental infrared method for the thermal characterisation of semiconductor devices during fast transient operation, in the range from a few microseconds and up to some milliseconds, is presented. The features which make it suitable and convenient, particularly for use with power electronics applications are pointed out; its time and space resolution are illustrated by means of properly chosen examples. The considered solution qualifies as a very versatile and powerful tool in many diverse lines of investigation.     

An On-Chip Spectrum Analyzer for Analog Built-In Testing

This paper presents an analog built-in testing (BIT) architecture and its implementation. It enables the frequency response and harmonic distortion characterizations of an integrated device-under-test (DUT) through a digital off-chip interface. External analog instrumentation is avoided, reducing test time and cost. The proposed on-chip testing scheme uses a digital frequency synthesizer and a simple signal generator synchronized with a switched capacitor bandpass filter. A general methodology for the use of this structure in the functional verification of a DUT is also provided. The circuit-level design and experimental results of an integrated prototype in standard CMOS 0.5 m technology are presented to demonstrate the feasibility of the proposed BIT technique.Marcia G. Mendez-Rivera was born in Irapuato, Mexico in 1972. She received the Communications and Electronics Engineering Degree from the Universidad de Guanajuato, Guanajuato, Mexico. in 1996, the M.Sc. degree from the Instituto Nacional de Astrofisica, Optica y Electronica (INAOE), Puebla, Mexico in 1998 and the M.Sc. from Texas A&M University, College Station in 2002. Her research interest is in the design and fabrication of analog and mixed-signal circuits.Alberto Valdes-Garcia born in 1978, grew up in San Mateo Atenco, Mexico. He received the B.S. in Electronic Systems Engineering degree from the Monterrey Institute of Technology (ITESM), Campus Toluca, Mexico in 1999 (with honors as the best score from all majors). Since the fall of 2000 he has been working towards the Ph.D. degree at Analog and Mixed-Signal Center (AMSC), Texas A&M University. During the spring and summer of 2000 he was a Design Engineer with Motorola Broadband Communications Sector. In the summer of 2002 he was with the Read Channel Design Group at Agere Systems where he investigated wide tuning range GHz LC VCOs for mass storage applications. During the summer of 2004 he was with the Mixed-Signal Communications IC Design Group at the IBM T. J. Watson Research Center, where worked on design and analysis of SiGe power amplifiers for millimeter wave radios. Since the fall of 2001 he has been a Semiconductor Research Corporation (SRC) research assistant at the AMSC working on the development of analog built-in testing techniques. Since the fall of 2000, Alberto has been the recipient of a scholarship from the Mexican National Council for Science and Technology (CONACYT). He represented Mexico in the 1994 Odyssey of the Mind World Creativity Contest and in the 1997 International Exposition for Young Scientists. His present research interests include built-in testing implementations for analog and RF circuits, system level design for wireless receivers and RF circuit design for UltraWideBand (UWB) communications.Jose Silva-Martinez was born in Tecamachalco, Puebla, México. He received the B.S. degree in electronics from the Universidad Autónoma de Puebla, México, in 1979, the M.Sc. degree from the Instituto Nacional de Astrofísica Optica y Electrónica (INAOE), Puebla, México, in 1981, and the Ph.D. degree from the Katholieke Univesiteit Leuven, Leuven Belgium in 1992. From 1981 to 1983, he was with the Electrical Engineering Department, INAOE, where he was involved with switched-capacitor circuit design. In 1983, he joined the Department of Electrical Engineering, Universidad Autonoma de Puebla, where he remained until 1993; He was a co-founder of the graduate program on Opto-Electronics in 1992. From 1985 to 1986, he was a Visiting Scholar in the Electrical Engineering Department, Texas A&M University. In 1993, he re-joined the Electronics Department, INAOE, and from May 1995 to December 1998, was the Head of the Electronics Department; He was a co-founder of the Ph.D. program on Electronics in 1993. He is currently with the Department of Electrical Engineering (Analog and Mixed Signal Center) Texas A&M University, at College Station, where He holds the position of Associate Professor. His current field of research is in the design and fabrication of integrated circuits for communication and biomedical application. Dr. Silva-Martinez has served as IEEE CASS Vice President Region-9 (1997–1998), and as Associate Editor for IEEE Transactions on Circuits and Systems part-II from 1997–1998 and May 2002–December 2003. Since January 2004 is serving as Associate Editor of IEEE TCAS Part-I. He was the main organizer of the 1998 and 1999 International IEEE-CAS Tour in region 9, and Chairman of the International Workshop on Mixed-Mode IC Design and Applications (1997–1999). He is the inaugural holder of the TI Professorship-I in Analog Engineering, Texas A&M University. He was a co-recipient of the 1990 European Solid-State Circuits Conference Best Paper Award.Edgar Sánchez-Sinencio was born in Mexico City, Mexico. He received the degree in communications and electronic engineering (Professional degree) from the National Polytechnic Institute of Mexico, Mexico City, the M.S.E.E. degree from Stanford University, CA, and the Ph.D. degree from the University of Illinois at Urbana-Champaign, in 1966, 1970, and 1973, respectively. In 1974 he held an industrial Post-Doctoral position with the Central Research Laboratories, Nippon Electric Company, Ltd., Kawasaki, Japan. From 1976 to 1983 he was the Head of the Department of Electronics at the Instituto Nacional de Astrofísica, Optica y Electrónica (INAOE), Puebla, Mexico. He was a Visiting Professor in the Department of Electrical Engineering at Texas A&M University, College Station, during the academic years of 1979–1980 and 1983-1984. He is currently the TI J Kilby Chair Professor and Director of the Analog and Mixed-Signal Center at Texas A&M University. He was the General Chairman of the 1983 26th Midwest Symposium on Circuits and Systems. He was an Associate Editor for IEEE Trans. on Circuits and Systems, (1985–1987), and an Associate Editor for the IEEE Trans. on Neural Networks. He is the former Editor-in-Chief of the Transactions on Circuits and Systems II. He is co-author of the book Switched Capacitor Circuits (Van Nostrand-Reinhold 1984), and co-editor of the book Low Voltage/Low-Power Integrated Circuits and Systems (IEEE Press 1999). In November 1995 he was awarded an Honoris Causa Doctorate by the National Institute for Astrophysics, Optics and Electronics, Mexico. The first honorary degree awarded for Microelectronic Circuit Design contributions. He is co-recipient of the 1995 Guillemin-Cauer for his work on Cellular Networks. He is a former IEEE CAS Vice President-Publications. He was also the co-recipient of the 1997 Darlington Award for his work on high-frequency filters He received the Circuits and Systems Society Golden Jubilee Medal in 1999. He was the IEEE Circuits and Systems Society, Representative to the Solid-State Circuits Society (2000–2002). He is presently a member of the IEEE Solid-State Circuits Fellow Award Committee. His present interests are in the area of RF-Communication circuits and analog and mixed-mode circuit design. He is an IEEE Fellow Member since 1992.     

Synthesis,size-dependent optoelectronic and charge transport properties of thieno(bis)imide end-substituted molecular semiconductors

The synthesis of two new thieno(bis)imide (TBI, N) end functionalized oligothiophene semiconductors is reported. In particular, trimer (NT3N) and pentamer (NT5N) have been synthesized and characterized. Two different synthetic approaches for their preparation were tested and compared namely conventional Stille cross coupling and direct arylation reaction via C–H activation. Theoretical calculations, optical and electrochemical characterization allowed us to assess the role of the π-conjugation extent, i.e., of the oligomer size on the optoelectronic properties of these materials. In both TBI ended compounds, due to the strong localization of the LUMO orbital on the TBI unit, the LUMO energy is almost insensitive to the oligomer size, this being crucial for the fine-tailoring of the energy and the distribution of the frontier orbitals. Surprisingly, despite its short size and contrarily to comparable TBI-free analogues, NT3N shows electron charge transport with mobility up to μ_N = 10⁻⁴ cm² V⁻¹ s⁻¹, while increasing the oligomer size to NT5N promotes ambipolar behavior and electroluminescence properties with mobility up to μ_N = 0.14 cm² V⁻¹ s⁻¹ and to μ_P = 10⁻⁵ cm² V⁻¹ s⁻¹.