Impact of signal quantization on the performance of RFI mitigation algorithms

Radio Frequency Interference (RFI) is currently a major problem in Communications and Earth Observation, but it is even more dramatic in Microwave Radiometry because of the low power levels of the received signals. Its impact has been attested in several Earth Observation missions. On-board mitigation systems are becoming a requirement to detect and remove affected measurements, increasing thus radiometric accuracy and spatial coverage. However, RFI mitigation methods have not been tested yet in the context of some particular radiometer topologies, which rely on the use of coarsely quantized streams of data. In this study, the impact of quantization and sampling in the performance of several known RFI mitigation algorithms is studied under different conditions. It will be demonstrated that in the presence of clipping, quantization changes fundamentally the time-frequency properties of the contaminated signal, strongly impairing the performance of most mitigation methods. Important design considerations are derived from this analysis that must be taken into account when defining the architecture of future instruments. In particular, the use of Automatic Gain Control (AGC) systems is proposed, and its limitations are discussedPeer ReviewedPostprint (published version

On the detection of RFI through the correlation anomaly at different time lags

Microwave radiometers can be considerably affected by Radio Frequency Interference (RFI). These man-made interference conceal the underlying natural signal, preventing the retrieval of geophysical variables. Adopting on-board detection and mitigation techniques is a requirement to reduce the impact of RFI. Several families of RFI detection algorithms have been developed over the last years (e.g. [1]–[4]). In this work, a new detection technique is proposed and its performance analyzed. It is based in the distortion of the shape of the cross-correlation function at lags different from zero under the presence of RFI. Its performance is compared to other common RFI mitigation algorithms. Proposed methods' performance is found to surpass other common algorithms such as signal Kurtosis, while presenting some convenient properties for its practical application in correlation and synthetic aperture radiometers.Peer ReviewedPostprint (author's final draft

On the potential of empirical mode decomposition for RFI mitigation in microwave radiometry

Radio-frequency interference (RFI) is an increasing problem particularly for Earth observation using microwave radiometry. RFI has been observed, for example, at L-band by the European Space Agency’s (ESA’s) soil moisture and ocean salinity (SMOS) Earth Explorer and by National Aeronautics and Space Administration’s (NASA’s) soil moisture active passive (SMAP) and Aquarius missions, as well as at C-band by Advanced Microwave Scanning Radiometer (AMSR)-E and AMSR-2, and at 10.7 and 18.7 GHz by AMSR-E, AMSR-2, WindSat, and GPM Microwave Imager (GMI). Therefore, systems dedicated to interference detection and removal of contaminated measurements are nowadays a must in order to improve radiometric accuracy and reduce the loss of spatial coverage caused by interference. In this work, the feasibility of using the empirical mode decomposition (EMD) technique for RFI mitigation is explored. The EMD, also known as Hilbert–Huang transform (HHT), is an algorithm that decomposes the signal into intrinsic mode functions (IMFs). The achieved performance is analyzed, and the opportunities and caveats that this type of methods present are described. EMD is found to be a practical RFI mitigation method, albeit presenting some limitations and considerable complexity. Nevertheless, in some conditions, EMD exhibits a better performance than other commonly used methods (such as frequency binning). In particular, it has been found that EMD performs well for RFI affecting the <25% lower part of the intermediate frequency (IF) bandwidth.This work was supported in part by the Sensing With Pioneering Opportunistic Techniques (SPOT) under Grant RTI2018-099008-B-C21/ AEI/10.13039/501100011033, in part by the RYC-2016-20918 under Grant MCIN/AEI/10.13039/501100011033, and in part by the European Social Fund (ESF), Investing in your future.Peer ReviewedPostprint (author's final draft

Funciones físicas no-clonables para ciberseguridad

En este trabajo se implementa una función física no-clonable (PUF) basada en osciladores de anillo. En primer lugar, se investigan diferentes métodos para obtener información sobre la frecuencia de los osciladores. A continuación, se examina la dependencia de la frecuencia de los osciladores con su posición en una FPGA. Se proponen cinco estrategias diferentes de selección de un pequeño conjunto de ubicaciones a partir de un gran conjunto de ubicaciones y se estudia la PUF construida en términos de unicidad, reproducibilidad e identificabilidad. Este análisis demuestra que la calidad de la PUF es altamente dependiente de la posición donde se implementan los osciladores. Finalmente, se analiza la modificación de los resultados en respuesta a cambios en el entorno de operación tales como variaciones de temperatura o del voltaje de alimentación de la placa.<br /

Contribution to conducted EMI reduction in multiconverter topology

This paper contributes to the conducted EMI reduction generated by switched power converters operating in multiconverter arrangement. The EMI reduction is achieved by means of the combination of two techniques: interleaving and switching frequency modulation. The effectiveness of such methods in terms of EMI reduction is experimentally validated in a four channel parallel buck converter. The technique that provides the best attenuation results is identified. Finally, special attention has been paid to possible undesired side-effects produced by these techniques. For this reason the converter efficiency and output voltage ripple are evaluated.Peer ReviewedPreprin

A new switching frequency modulation scheme for EMI reduction in multiconverter topology

This paper presents a modulation scheme in order to reduce conducted Electromagnetic Interference (EMI) generated by modular power converters with parallel topology. The proposed scheme is based on a combination of interleaving and Switching Frequency Modulation (SFM) techniques. The objective of this modulation scheme is to cancel certain harmonics of EMI and to reduce the amplitude of the remaining harmonics. The proposed scheme has been implemented in a field programmable gate array and a four channel parallel buck converter has been used in order to verify it. A significant EMI reduction has been obtained in comparison to use the interleaving and Switching Frequency Modulation separately.Peer ReviewedPostprint (published version

Bioelectrochemical enhancement of methane production from exhausted vine shoot fermentation broth by integration of MEC with anaerobic digestion

[ES] A microbial electrolysis cell integrated in an anaerobic digestion system (MEC-AD) is an efficient configuration to produce methane from an exhausted vine shoot fermentation broth (EVS). The cell worked in a single-chamber two-electrode configuration at an applied potential of 1 V with a feeding ratio of 30/70 (30% EVS to 70% synthetic medium). In addition, an identical cell operated in an open circuit was used as a control reactor. Experimental results showed similar behavior in terms of carbon removal (70–76%), while the specific averaged methane production from cycle 7 was more stable and higher in the connected cell (MECAD) compared with the unpolarized one (OCAD) accounting for 403.7 ± 33.6 L CH4·kg VS−1 and 121.3 ± 49.7 L CH4·kg VS−1, respectively. In addition, electrochemical impedance spectroscopy revealed that the electrical capacitance of the bioanode in MECAD was twice the capacitance shown by OCAD. The bacterial community in both cells was similar but a clear adaptation of Methanosarcina Archaea was exhibited in MECAD, which could explain the increased yields in CH4 production. In summary, the results reported here confirm the advantages of integrating MEC-AD for the treatment of real organic liquid waste instead of traditional AD treatment.SIPublicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCL

Aspectos de la calidad e-learning: referencia a la Universidad de La Rioja

En esta comunicación presentamos la experiencia de la impartición de asignaturas integramente en red. Estudiamos cuál es el nuevo rol del docente, al ser uno de los aspectos nucleares sobre los que gira este tipo de enseñanza. El docente pasa a ser un facilitador y ayudante del estudiante en su proceso de aprendizaje, para ello debe crear un ambiente cómodo, tener claros los objetivos y conocer las nuevas tecnologías. Aportamos también ciertos datos específicos de la Universidad de La Rioja en relación a las dos licenciaturas que se imparten en ella. A continuación, analizamos aquellos aspectos relevantes a considerar para evaluar si se ofrece calidad en la formación a través de la red. En este sentido pueden utilizarse modelos parciales y modelos globales, estos últimos aplicables a toda la universidad.In this paper, we present an experience with subjects taught entirely on the Internet. We study the new role of teachers, as this is one of the core aspects of this kind of teaching efforts. Teachers have become facilitators and assistants of students in their learning process, and to this aim, they must create a comfortable atmosphere, have clear objectives and be familiar with the new technologies. We also provide some specific data of the University of La Rioja concerning its two degrees taught on the Internet. Then, we analyze the relevant aspects to consider when assessing the quality of education on the Internet. In this sense, two kinds of models can be used: partial models and models applicable to the whole University (global models)

Gremlin activates the smad pathway linked to epithelial mesenchymal transdifferentiation in cultured tubular epithelial cells

Gremlin is a developmental gene upregulated in human chronic kidney disease and in renal cells in response to transforming growth factor-(TGF-β). Epithelial mesenchymal transition (EMT) is one process involved in renal fibrosis. In tubular epithelial cells we have recently described that Gremlin induces EMT and acts as a downstream TGF-β mediator. Our aim was to investigate whether Gremlin participates in EMT by the regulation of the Smad pathway. Stimulation of human tubular epithelial cells (HK2) with Gremlin caused an early activation of the Smad signaling pathway (Smad 2/3 phosphorylation, nuclear translocation, and Smad-dependent gene transcription). The blockade of TGF-β, by a neutralizing antibody against active TGF-β, did not modify Gremlin-induced early Smad activation.These data showthatGremlin directly, by a TGF-β independent process, activates the Smad pathway. In tubular epithelial cells long-term incubation with Gremlin increased TGF-β production and caused a sustained Smad activation and a phenotype conversion into myofibroblasts-like cells. Smad 7 overexpression, which blocks Smad 2/3 activation, diminished EMT changes observed in Gremlin-transfected tubuloepithelial cells. TGF-β neutralization also diminished Gremlininduced EMT changes. In conclusion, we propose that Gremlin could participate in renal fibrosis by inducing EMT in tubular epithelial cells through activation of Smad pathway and induction of TGF-βThis work was supported by grants from the Instituto de Salud Carlos III (PI11/01854 and REDINREN ISCIIIRETIC RD12/0021/0002 and 0001), Sociedad Española de Nefrología, PCI Iberoamerica (A/9571/07), CYTED IBERERC, FONDECYT Chile 1080083 and 1120480, Comunidad de Madrid (Fibroteam S2010/BMD-2321, S2010/BMD- 2378), Programa Intensificación Actividad Investigadora (ISCIII/Agencia Laín Entralgo/CM) to A.O. Fundación para el fomento en Asturias de la investigaciónn cientíica aplicada y la tecnología (FICYT)

Effect of hemodialysis session on acute changes in inflammatory and cardiovascular risk biomarkers

Background: Inflammation is associated with enhanced cardiovascular risk profile and increased cardiovascular mortality in end-stage kidney disease patients undergoing hemodialysis. Mechanisms of activated acute phase reaction in patients on chronic hemodialysis remain to be identified. As successful treatment of the inflammatory condition in these patients may improve long-term survival, we studied potential changes in different inflammatory biomarkers of cardiovascular risk in end-stage kidney disease patients after a mid-week hemodialysis session. Methods: Inflammatory biomarkers of cardiovascular risk (cystatin-C, homocysteine, C-reactive protein, procalcitonin, pentraxin-3, serum amyloid-A) and atherogenic plasma lipoproteins (Lipoprotein(a), cholesterol low and high density lipoproteins) were studied in 21 end-stage kidney disease patients previously and after a mid-week hemodialysis session. Results: We found a significant reduction in serum levels of low molecular weight molecules: cystatin-C (5.56 to 1.85 mg/L, 66.73%, p < 0.001), homocysteine (22.85 to 13.25 µmol/L, 42.01%, p < 0.001) and procalcitonin (0.788 to 0.457 ng/mL, 42.01%, p < 0.001). Large molecules as C-reactive protein (9.70 to 9.90 mg/L, 2.06%, p = 0.022) and pentraxin-3 (1.67 to 4.28 ng/mL, 156%, p < 0.001) increased, but serum amyloid-A decreased (15.90 to 12.70 mg/L, 20.13%, p < 0.05). There was no change in Lipoprotein (a) levels. Conclusion: Pentraxin-3 was a more specific inflammatory vascular marker than C-reactive protein, and the best inflammatory marker associated with hemodialysis. Homocysteine, procalcitonin and the other small proteins could be released and removed during hemodialysis session. Further studies are needed to understand the behavior and significance of these markers after successive hemodialysis