In silico study of reaction mechanisms and design principles for water oxidation catalysts

Throughout the last decades the water oxidation process has been extensively investigated. However, open questions remain on the reaction mechanism and the possible intermediates in the catalytic cycle. Indeed, different catalysts can function through different reaction routes. Some of them work in a proton-coupled electron transfer (PCET) pathway, while other catalysts have a non-PCET behaviour. Some of these problems lie in the very short lifetime of intermediates, which makes it difficult to characterize them experimentally. Within this context, DFT calculations represent a very useful tool. In fact quantum-mechanical computational tools allow exploring and analyzing the possible intermediates and study and compare different reaction pathways in order to find the energetically most likely one. In the same way the thermodynamics of the catalytic cycle and the kinetics of the reaction coordinates can be analyzed. The specific aim of this thesis is the study of different catalysts and reaction pathways to find clues about the mechanism of the reaction and develop guiding principles for the design of efficient water oxidation complexesUBL - phd migration 201

Tailor-Made Tissue Phantoms Based on Acetonitrile Solutions for Microwave Applications up to 18 GHz

(c) 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.Tissue-equivalent phantoms play a key role in the development of new wireless communication devices that are tested on such phantoms prior to their commercialization. However, existing phantoms cover a small number of tissues and do not reproduce them accurately within wide frequency bands. This paper aims at enlarging the number of mimicked tissues as well as their working frequency band. Thus, a variety of potential compounds are scanned according to their relative permittivity from 0.5 to 18 GHz. Next, a combination of these compounds is characterized so the relation between their dielectric properties and composition is provided. Finally, taking advantage of the previous analysis, tailor-made phantoms are developed for different human tissues up to 18 GHz and particularized for the main current body area network (BAN) operating bands. The tailor-made phantoms presented here exhibit such a high accuracy as would allow researchers and manufacturers to test microwave devices at high frequencies for large bandwidths as well as the use of heterogeneous phantoms in the near future. The key to these phantoms lies in the incorporation of acetonitrile to aqueous solutions. Such compounds have a suitable behavior to achieve the relative permittivity values of body tissues within the studied frequency band.This work was supported by the Ministerio de Economia y Competitividad, Spain (TEC2014-60258-C2-1-R) and by the European FEDER Funds.Castelló-Palacios, S.; García Pardo, C.; Fornés Leal, A.; Cardona Marcet, N.; Vallés Lluch, A. (2016). Tailor-Made Tissue Phantoms Based on Acetonitrile Solutions for Microwave Applications up to 18 GHz. IEEE Transactions on Microwave Theory and Techniques. 64(11):3987-3994. https://doi.org/10.1109/TMTT.2016.2608890S39873994641

Formulas for easy-to-prepare tailored phantoms at 2.4 GHz ISM band

[EN] Emerging integration of communication networks into wearable or implantable body devices involves a challenge due to the transmitting medium, the body itself. This medium is heterogeneous and lossier than air, so devices that are supposed to work on it should be tested in tissue-equivalent materials. A number of materials with the electromagnetic response of body tissues have been proposed. Most of them are sucrose aqueous solutions that are supposed to simulate human's muscle tissue mainly within medical frequency bands. However, these recipes are restricted to a single tissue and it is difficult to adapt them to fit the permittivity values of different body tissues. The significance of this study lies in the development of a mathematical relationship that models the dielectric properties of an aqueous solution according to the concentration of sugar and salt at 2.4 GHz, the frequency around which an Industrial, Scientific and Medical (ISM) band is placed. Thus, it becomes possible to create custom-made phantoms with simple and accessible ingredients that are easy to prepare in any laboratory.This work was supported by the Ministerio de Economia y Competitividad, Spain (TEC2014-60258-C2-1-R) and by the European FEDER Funds.Castelló-Palacios, S.; Garcia-Pardo, C.; Fornés Leal, A.; Cardona Marcet, N.; Vallés Lluch, A. (2017). Formulas for easy-to-prepare tailored phantoms at 2.4 GHz ISM band. IEEE. 27-31. https://doi.org/10.1109/ISMICT.2017.7891760S273

Accurate broadband measurement of electromagnetic tissue phantoms using open-ended coaxial systems

[EN] New technologies and devices for wireless communication networks are continually developed. In order to assess their performance, they have to be tested in realistic environments taking into account the influence of the body in wireless communications. Thus, the development of phantoms, which are synthetic materials that can emulate accurately the electromagnetic behaviour of different tissues, is mandatory. An accurate dielectric measurement of these phantoms requires using a measurement method with a low uncertainty. The open-ended coaxial technique is the most spread technique but its accuracy is strongly conditioned by the calibration procedure. A typical calibration is performed using an open circuit, a short circuit and water. However, this basic calibration is not the most accurate approach for measuring all kinds of materials. In this paper, an uncertainty analysis of the calibration process of open-ended coaxial characterization systems when a polar liquid is added to the typical calibration is provided. Measurements are performed on electromagnetically well-known liquids in the 0.5 - 8.5 GHz band. Results show that adding methanol improves the accuracy in the whole solution domain of the system, mainly when measuring phantoms that mimic high water content tissues, whereas ethanol is more suitable for measuring low water content tissue phantoms.This work was supported by the Ministerio de Educacion y Ciencia, Spain (ref. TEC2014-60258-C2-1-R, TEC2014-56469-REDT), by the European FEDER funds.Fornés Leal, A.; Garcia-Pardo, C.; Castelló-Palacios, S.; Vallés Lluch, A.; Cardona Marcet, N. (2007). Accurate broadband measurement of electromagnetic tissue phantoms using open-ended coaxial systems. IEEE. 32-36. https://doi.org/10.1109/ISMICT.2017.7891761S323

Wideband phantoms of different body tissues for heterogeneous models in body area networks

[EN] One of the key issues about wireless technologies is their interaction with the human body. The so-called internet of things will comprise many devices that will transmit either around or through the human body. These devices must be tested either in their working medium, when possible, or in the most realistic one. For this purpose, tissue-like phantoms are the best alternative to carry out realistic analyses of the performance of body area networks. In addition, they are the conventional way to certify the compliance of commercial standards by these devices. However, the number of phantoms that work in large bandwidths is limited in literature. This work aims at presenting chemical solutions that will be useful to prepare a variety of wideband tissue phantoms. Besides, the colon was mimicked in two ways, the healthy tissue and the malignant one, taking into account studies that relate changes on the relative permittivity with cancer. They were designed on the basis of acetonitrile in aqueous solutions as described in a previous work. Thus, many scenarios could be developed such as multilayers which imitate parts of the heterogeneous body.Research supported by the Programa de Ayudas de Investigación y Desarrollo (PAID-01-16) from Universitat Politècnica de València, by the Ministerio de Economía y Competitividad, Spain (TEC2014-60258-C2-1- R) and by the European FEDER Funds.Castelló-Palacios, S.; Garcia-Pardo, C.; Fornés Leal, A.; Cardona Marcet, N.; Vallés Lluch, A. (2018). Wideband phantoms of different body tissues for heterogeneous models in body area networks. IEEE. 3032-3035. https://doi.org/10.1109/EMBC.2017.8037496S3032303

Frequency Dependence of UWB In-Body Radio Channel Characteristics

(c) 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.[EN] In this letter, a research of ultra-wideband in-body channel by using a high accurate phantom is performed in order to evaluate the impact of frequency dependence of human tissues on the channel characteristics. Hence, a phantom-based measurement campaign from 3.1 to 5.1 GHz has been conducted. From postprocessing data, the path loss is assessed considering subbands of 500 MHz as well as the entire frequency range under test. In addition, the correlation in transmission is computed and discussed.This work was supported in part by the Ministerio de Economia y Competitividad, Spain, under Grant TEC2014-60258-C2-1-R, and in part by the European FEDER funds. (Corresponding author: Carlos Andreu.)Andreu-Estellés, C.; Garcia-Pardo, C.; Castelló-Palacios, S.; Vallés Lluch, A.; Cardona Marcet, N. (2018). Frequency Dependence of UWB In-Body Radio Channel Characteristics. IEEE Microwave and Wireless Components Letters. 28(4):359-361. https://doi.org/10.1109/LMWC.2018.2808427S35936128

Gel Phantoms for Body Microwave Propagation in the (2 to 26.5) GHz Frequency Band

[EN] Tissue phantoms are widely used for assessing the interaction between the electromagnetic waves and the human body. These are especially key in body area networks, where the body itself acts as the propagation medium since transmission is highly influenced by its diverse dielectric properties. Gels are suitable materials because of their high water content, which is required to mimic the dielectric properties of most tissues. In this paper, PHEA gels are suggested for achieving those properties due to their synthetic nature, which gives them the possibility to be swollen reversibly in more types of mixtures, in addition to water. These gels can be tailored to control the amount of liquid they embed so that they can imitate different body tissues in a wide bandwidth (2¿26.5 GHz), which includes most of the current mobile communication and medical bands. This versatility offers the chance to create heterogeneous models of particular regions of the body, and thus improve the test realism. In addition, they own better mechanical and stability properties than the widely used agar or gelatin.This work was supported in part by the Universitat Politecnica de Valencia-Institut d'Investigacio Sanitaria La Fe (UPV-IIS La Fe) Program [Early Stage Colon Tumour Diagnosis by Electromagnetic Reflection (STuDER), 2016 and Electromagnetic Probe for Early Tumour Detection (EMOTE), 2017], in part by the Universitat Politecnica de Valencia through the Programa de Ayudas de Investigacion y Desarrollo under Grant PAID-01-16, and in part by the European Union's H2020: MSCA: ITN Program for the "mmWave Communications in the Built Environments - WaveComBE" Project under Grant 766231.Castelló-Palacios, S.; Garcia-Pardo, C.; Alloza-Pascual, M.; Fornés Leal, A.; Cardona Marcet, N.; Vallés Lluch, A. (2019). Gel Phantoms for Body Microwave Propagation in the (2 to 26.5) GHz Frequency Band. IEEE Transactions on Antennas and Propagation. 67(10):6564-6573. https://doi.org/10.1109/TAP.2019.2920293S65646573671

Spatial In-Body Channel Characterization Using an Accurate UWB Phantom

"(c) 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works."Ultra-wideband (UWB) systems have emerged as a possible solution for future wireless in-body communications. However, in-body channel characterization is complex. Animal experimentation is usually restricted. Furthermore, software simulations can be expensive and imply a high computational cost. Synthetic chemical solutions, known as phantoms, can be used to solve this issue. However, achieving a reliable UWB phantom can be challenging since UWB systems use a large bandwidth and the relative permittivity of human tissues are frequency dependent. In this paper, a measurement campaign within 3.1-8.5 GHz using a new UWB phantom is performed. Currently, this phantom achieves the best known approximation to the permittivity of human muscle in the whole UWB band. Measurements were performed in different spatial positions, in order to also investigate the diversity of the in-body channel in the spatial domain. Two experimental in-body to in-body (IB2IB) and in-body to on-body (IB2OB) scenarios are considered. From the measurements, new path loss models are obtained. Besides, the correlation in transmission and reception is computed for both scenarios. Our results show a highly uncorrelated channel in transmission for the IB2IB scenario at all locations. Nevertheless, for the IB2OB scenario, the correlation varies depending on the position of the receiver and transmitter.This work was supported by the Ministerio de Economia y Competitividad, Spain, under Grant TEC2014-60258-C2-1-R and Grant TEC2014-56469-REDT and by the European FEDER Funds.Andreu Estellés, C.; Castelló Palacios, S.; García Pardo, C.; Fornés Leal, A.; Vallés Lluch, A.; Cardona Marcet, N. (2016). Spatial In-Body Channel Characterization Using an Accurate UWB Phantom. IEEE Transactions on Microwave Theory and Techniques. 64(11):3995-4002. doi:10.1109/TMTT.2016.2609409S39954002641

Experimental Path Loss Models for In-Body Communications Within 2.36-2.5 GHz

"(c) 2015 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works."Biomedical implantable sensors transmitting a variety of physiological signals have been proven very useful in the management of chronic diseases. Currently, the vast majority of these in-body wireless sensors communicate in frequencies below 1 GHz. Although the radio propagation losses through biological tissues may be lower in such frequencies, e.g., the medical implant communication services band of 402 to 405 MHz, the maximal channel bandwidths allowed therein constrain the implantable devices to low data rate transmissions. Novel and more sophisticated wireless in-body sensors and actuators may require higher data rate communication interfaces. Therefore, the radio spectrum above 1 GHz for the use of wearable medical sensing applications should be considered for in-body applications too. Wider channel bandwidths and smaller antenna sizes may be obtained in frequency bands above 1 GHz at the expense of larger propagation losses. Therefore, in this paper, we present a phantom-based radio propagation study for the frequency bands of 2360 to 2400 MHz, which has been set aside for wearable body area network nodes, and the industrial, scientific, medical band of 2400 to 2483.5 MHz. Three different channel scenarios were considered for the propagation measurements: in-body to in-body, in-body to on-body, and in-body to off-body.We provide for the first time path loss formulas for all these cases.Chavez-Santiago, R.; García Pardo, C.; Fornés Leal, A.; Vallés Lluch, A.; Vermeeren, G.; Joseph, W.; Balasingham, I.... (2015). Experimental Path Loss Models for In-Body Communications Within 2.36-2.5 GHz. IEEE Journal of Biomedical and Health Informatics. 19(3):930-937. doi:10.1109/JBHI.2015.2418757S93093719

Ultrawideband Technology for Medical In-Body Sensor Networks: An Overview of the Human Body as a Propagation Medium, Phantoms, and Approaches for Propagation Analysis

[EN] An in-body sensor network is that in which at least one of the sensors is located inside the human body. Such wireless in-body sensors are used mainly in medical applications, collecting and monitoring important parameters for health and disease treatment. IEEE Standard 802.15.6-2012 for wireless body area networks (WBANs) considers in-body communications in the Medical Implant Communications Service (MICS) band. Nevertheless, high-data-rate communications are not feasible at the MICS band because of its narrow occupied bandwidth. In this framework, ultrawideband (UWB) systems have emerged as a potential solution for in-body highdata-rate communications because of their miniaturization capabilities and low power consumption.This work was supported by the Programa de Ayudas de Investigación y Desarrollo (PAID-01-16) at the Universitat Politècnica de València, Spain; by the Ministerio de Economía y Competitividad, Spain (TEC2014-60258-C2-1-R); and by the European FEDER funds. It was also funded by the European Union’s H2020:MSCA:ITN program for the Wireless In-Body Environ-ment Communication–WiBEC project under grant 675353.Garcia-Pardo, C.; Andreu-Estellés, C.; Fornés Leal, A.; Castelló-Palacios, S.; Pérez-Simbor, S.; Barbi, M.; Vallés Lluch, A.... (2018). Ultrawideband Technology for Medical In-Body Sensor Networks: An Overview of the Human Body as a Propagation Medium, Phantoms, and Approaches for Propagation Analysis. IEEE Antennas and Propagation Magazine. 60(3):19-33. https://doi.org/10.1109/MAP.2018.2818458S193360