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Unidad externa para una estación terrena del experimento CODE

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Instantaneous model of a MESFET for use in linear and nonlinear circuit simulations

A formal approach for nonlinear modeling of FETs is presented. The intrinsic transistor is described by current and charge generators, that are instantaneously dependent on the two internal voltages. The extrinsic parasitic elements are also included. This instantaneous model is obtained from the small signal equivalent circuit computed at a number of bias points, by integration of the bias dependent elements. A program for using this model in nonlinear circuit analysis has been developed. The process has been carried out for two transistors, one being of low noise, and the other a power MESFET. Good agreement has been observed when comparing the nonlinear analysis with measured data. A solid-state power amplifier at 28 GHz has been designed using the power transistor, delivering 21 dBm at 1 dB compression point.Peer ReviewedPostprint (published version

Caracterización funcional del mucus epidérmico en peces de interés productivo: Metodología no invasiva de identificación de moléculas biomarcadoras y relación con el estado fisiológico.

[spa] La acuicultura se ha convertido en una alternativa real y rentable a la pesca extractiva para proporcionar un alimento de un elevado valor nutritivo. Entre las especies de mayor relevancia en la producción acuícola marina del área Mediterránea, se encuentran la dorada (Sparus aurata), la lubina (Dicentrarchus labrax) y más recientemente la corvina (Argyrosomus regius). Si bien se han conseguido grandes adelantos en la mejora de la alimentación y el crecimiento, las metodologías más utilizadas de análisis para determinar su estado fisiológico son de carácter invasivo, ya sea por análisis sobre tejidos (lo que provoca la muerte del animal) o hematológicos (pueden provocar patologías adyacentes). Las superficies mucosas (en piel, branquias e intestino) de los peces teleósteos constituyen la primera línea de defensa contra la infección patógena además de participar en un amplio espectro de otros procesos fisiológicos muy importantes como la absorción de nutrientes, la osmoregulación, la respiración, la locomoción o la excreción de residuos. En la última década, el mucus epidérmico llegado a cautivar a muchos investigadores por su gran variedad de respuestas frente a diferentes condiciones y además, por tener un potencial muy importante para ser un método no invasivo de estudio del estado global del animal. Este trabajo se ha centrado en la característica no invasiva y potencial del mucus epidérmico. Por otro lado, tiene como objetivo principal obtener un conjunto completo de marcadores biológicos o biomarcadores (definidos en este trabajo como biomarcadores asociados al mucus de la piel o SMABs, por sus siglas en inglés “Skin Mucus Associated Biomarkers” del estado fisiológico en el mucus para poder establecer su relación con la respuesta a los cambios ambientales y nutricionales. Para ello, se propuso: caracterizar los componentes proteicos del mucus en dorada, estudiar la respuesta mediante diferentes agentes estresores, ya sean agudos o crónicos y caracterizar y comparar algunas de las propiedades defensivas del mucus entre las tres especies. Como resultado de todos estos objetivos, se han identificado una serie de posibles SMABs ordenados de la siguiente manera: 1) características físico-químicas, dónde se propone el estudio reológico del mucus como un posible informador de un estrés agudo; 2) metabolitos y hormonas, estudiando sus cambios en el mucus, sus niveles de exudación puede informar sobre respuestas agudas, como por ejemplo en los metabolitos como la glucosa, el lactato, la proteína o en la hormona cortisol; 3) enzimas con función defensiva no-específica, tanto proteasas como esterasas tienen un papel muy importante en el mucus, por ello se estudió el zimograma de la actividad proteasa y la familia de las carboxilesterasas, como posibles marcadores biológicos frente a un estrés crónico; y 4) otras moléculas principalmente de estrés crónico, como: la actina y sobretodo sus isoformas, importantes informadoras sobre la secreción del mucus; diferentes fragmentos de queratina, propuestos como péptidos antimicrobianos; moléculas relacionadas con el metabolismo de la glucosa, que pueden informar sobre el estado metabólico interno de los animales; moléculas relacionadas con el metabolismo proteico, importantes para determinar la estructura del mucus o activadoras de varios componentes; y finalmente moléculas con un carácter protector como las transferrinas o diferentes chaperonas. Con todo ello, finalmente se determinó también la actividad bactericida del mucus epidérmico como indicativo del potencial real defensivo contra posibles infecciones. En las conclusiones del trabajo se explican los beneficios de estudiar las propiedades y componentes del mucus de la piel como indicativos del estado del animal y de manera no invasiva, indicando qué componentes pueden ser más interesantes de analizar de manera rápida y qué componentes responden a desafíos agudos o crónicos.[eng] Aquaculture has become a real and profitable alternative to extractive fishing, providing food with high nutritional value. In this work, we select three marine species with a great interest in Mediterranean aquaculture: gilthead sea bream (Sparus aurata), sea bass (Dicentrarchus labrax) and meagre (Argyrosomus regius), with the purpose to evaluate the health and welfare status of the animals through non-invasive methods, selecting putative biomarkers. Our aim was to use skin mucus as it plays an important role in innate defense, but also in other physiological processes such as osmoregulation, respiration, locomotion or waste excretion. For that, fish were subjected to different stress factors (acute and chronic), and different techniques were used to reveal a wide range of biomarkers, also described in the present study as Skin Mucus Associated Biomarkers, SMABs. As result, we propose the following biological markers: 1) related to rheology, mucus viscosity was selected as acute stress indicator; 2) related to metabolism response, metabolites such as glucose, lactate or protein, together with exuded cortisol, its mucus levels could report on acute responses like hypoxia or netting, and chronic stressors like fasting periods in sea bream; 3) related to enzymatic activities, several protease types could be good biomarkers of fish defense status or mucus removal, mainly the metalloprotease activity detected at chronic low temperatures, or esterases subfamily of carboxylesterase, within which we detected at least three different activities in fish mucus, all of them related to detoxifying capacity to different toxics; 4) related to different soluble mucus proteins by proteasome studies, like some structural β-actin or keratin isoforms (KDAMPs), some metabolic proteins related to glucose and protein metabolism, or protective proteins with different functions like transferrin or Heat Shock Proteins (HSPs). Finally, we also determined the bactericidal activity of the epidermal mucus as an indication of the real defensive potential against possible infections. In the conclusions section, we explain the benefits of studying the properties and components of the skin mucus as indicative of the animal state non-invasively, indicating which components can be more interesting to analyze quickly and which components would better respond to acute challenges or chronic conditions

Criterios y métodos de reducción del ruido de fase en osciladores de microondas con MESFET

This paper gives several building criteria for the design of microwave oscillators with MESFET (MESFET-MWO) in order to achieve low phase noise. From device low frequency noise model and identification of phase noise mechanisms generation and sources in MESFET-MWO, a novel expression of 1Hz single side noise power ro carrier power relation or ~(t) function is obtained. A low cost X band oscillator with high efficiency and medium power is built to prove the methods of phase noise reduction derived of that expression. The phase noise measured of the built oscillator allows us to doubt of the device noise model used.Peer ReviewedPostprint (published version

The correlation of visibility noise and its impact on the radiometric resolution of an aperture synthesis radiometer

The correlation between the visibility samples' noise of an aperture synthesis radiometer are required for the computation of the recovered temperature noise of a given pixel and of the improvement introduced by baseline redundance. A general expression for this correlation and noise examples for a linear array are presented.Peer ReviewedPostprint (published version

Ocean salinity observations with SMOS mission

The purpose of this paper is to present the capabilities of SMOS (Soil Moisture and Ocean Salinity mission) for the global mapping of ocean salinity from space. SMOS has been selected by the European Space Agency as the second Earth Explorer Opportunity with a launch date in June 2005. The sensor embarked on SMOS is MIRAS, a Microwave Imaging Radiometer with Aperture Synthesis. MIRAS works at L-band, in the two-polarisations, and has full polarimetric capability. The measurement of sea surface salinity (SSS) is one of the challenges of SMOS. This paper presents first the scientific requirements for a number of oceanographic applications. The scientific requirements are then translated into instrument accuracy, sensitivity, stability and spatial resolution. Major sources of error in the retrieval of ocean salinity will be addressed through an experimental campaign which is described.Peer ReviewedPostprint (published version

Evaluating the repetitive mucus extraction effects on mucus biomarkers, mucous cells, and the skin-barrier status in a marine fish model

Among all the mucosal barriers, the skin and its surrounding mucus are possibly the main defensive tool against changes in the environment that can be harmful for fish. Due to the extraction of this mucus being less invasive, the study of its production and functions has attracted great interest in recent years. However, there are still many gaps concerning the sampling process as well as the possible alterations in skin integrity and mucus composition. In the current study, the effects of skin mucus extraction were determined by comparing the effects of a single extraction (single extraction group, SEG) with those of three successive extractions separated by 3 days (repetitive extractions group, REG). Intact skin histology without mucus extraction (ØEG) and both plasma and skin mucus biomarkers and antibacterial capacities were also assessed. Regarding the skin histology and skin barrier properties, both the SEG and REG did not show differences in the intact skin. Interestingly, repetitive mucus extractions seemed to activate skin mucus turnover, significantly increasing the number of small-sized mucous cells (cell area< 100 µm2) and reducing the number of large-sized mucous cells (cell area > 150 µm2). Repetitive extractions significantly decreased the amounts of soluble protein and increased cortisol secretion. These metabolites remained unaltered in the plasma, indicating different responses in the plasma and mucus. Despite changes in the mucus biomarkers, antibacterial capacity against pathogenic bacteria (Pseudomonas anguilliseptica and Vibrio anguillarum) was maintained in both the plasma and mucus irrespective of the number of mucus extractions. Overall, the mucus sampling protocol had little effect on skin integrity and mucus antibacterial properties, only modifying the amounts of soluble protein exuded and stimulating mucous cell replacement. This protocol is a feasible and minimally invasive way of studying and monitoring fish health and welfare and can be used as an alternative or a complement to plasma analysis. This methodology can be transferred to farm culture conditions and be very useful for studying threatened species in order to preserve fish welfare

Exact representation of antenna system diversity performance from input parameter description

A simplc formulation Io compute thc envelope correlation of an antenna divemiry system is dcrired. 11 is shown how to compute the envelope correlation hom the S-parameter descnplian of the antenna system. This approach has the advantage that i t does not require the computation nor the measurement of the radiation panem of the antenna system. It also offers the advantage of providing a clca understanding ofthe effects ofmutual coupling and input match on the diversity performance of the antcnnii system

Processing and initial comparison of PSR data from CAMEX-3 to SSM/I and TMI data

A multiband Polarimetric Scanning Radiometer (PSR) was integrated on a NASA DC-8 aircraft and flown from August through September of 1998 during the third Convection and Moisture Experiment (CAMEX-3). The PSR is a new conically-scanning imaging radiometer with channels at 10.7, 18.7, 21.5, 37.0 and 89.0 GHz, including both vertical and horizontal polarizations at each of these frequencies. These channels correspond to several key sensing bands of the DMSP (Defense Meteorological Satellite Program) SSM/I (Special Sensor Microwave Imager) and the NASA TRMM (Tropical Rainfall Measuring Mission) TMI (TRMM Microwave Imager). The PSR was developed by Georgia Institute of Technology and the NOAA Environmental Technology Laboratory and is the first airborne imaging radiometer to provide a research quality dataset of high spatial resolution multiband polarimetric microwave imagery within and around a hurricane. The authors describe the processing and calibration of the PSR CAMEX-3 dataset. They also provide a qualitative analysis and comparison of the PSR imagery to the SSM/I and TMI with specific regard to the spatial structure of a hurricane eyewall and surrounding rainbands.Peer ReviewedPostprint (published version