Effects of gamma-Ray radiation on magnetic properties of NdFeB and SmCo permanent magnets for space applications

Several samples of NdFeB and SmCo permanent magnets have been irradiated with gamma rays up to different total irradiation doses until 1Mrad(Si). Magnetic properties of the samples have been measured at different temperatures before and after irradiation. The modifications of the magnetic parameters are presented. From these results it is highlighted which permanent magnets show more resistance to radiation and are more suitable to be included in devices for space applications or high radiation environments.

Crack mechanical failure in lithium niobate crystal under ion irradiation; novel simulation by extended finite elements

Swift heavy ion irradiation (ions with mass heavier than 15 and energy exceeding MeV/amu) transfer their energy mainly to the electronic system with small momentum transfer per collision. Therefore, they produce linear regions (columnar nano-tracks) around the straight ion trajectory, with marked modifications with respect to the virgin material, e.g., phase transition, amorphization, compaction, changes in physical or chemical properties. In the case of crystalline materials the most distinctive feature of swift heavy ion irradiation is the production of amorphous tracks embedded in the crystal. Lithium niobate is a relevant optical material that presents birefringence due to its anysotropic trigonal structure. The amorphous phase is certainly isotropic. In addition, its refractive index exhibits high contrast with those of the crystalline phase. This allows one to fabricate waveguides by swift ion irradiation with important technological relevance. From the mechanical point of view, the inclusion of an amorphous nano-track (with a density 15% lower than that of the crystal) leads to the generation of important stress/strain fields around the track. Eventually these fields are the origin of crack formation with fatal consequences for the integrity of the samples and the viability of the method for nano-track formation. For certain crystal cuts (X and Y), these fields are clearly anisotropic due to the crystal anisotropy. We have used finite element methods to calculate the stress/strain fields that appear around the ion-generated amorphous nano-tracks for a variety of ion energies and doses. A very remarkable feature for X cut-samples is that the maximum shear stress appears on preferential planes that form +/-45º with respect to the crystallographic planes. This leads to the generation of oriented surface cracks when the dose increases. The growth of the cracks along the anisotropic crystal has been studied by means of novel extended finite element methods, which include cracks as discontinuities. In this way we can study how the length and depth of a crack evolves as function of the ion dose. In this work we will show how the simulations compare with experiments and their application in materials modification by ion irradiation.

A molecular dynamics study of swift heavy ion irradiation of amorphous silica: the role of thermal effects

Irradiation with swift heavy ions (SHI), roughly defined as those having atomic masses larger than 15 and energies exceeding 1 MeV/amu, may lead to significant modification of the irradiated material in a nanometric region around the (straight) ion trajectory (latent tracks). In the case of amorphous silica, SHI irradiation originates nano-tracks of higher density than the virgin material (densification). As a result, the refractive index is increased with respect to that of the surroundings. Moreover, track overlapping leads to continuous amorphous layers that present a significant contrast with respect to the pristine substrate. We have recently demonstrated that SHI irradiation produces a large number of point defects, easily detectable by a number of experimental techniques (work presented in the parallel conference ICDIM). The mechanisms of energy transfer from SHI to the target material have their origin in the high electronic excitation induced in the solid. A number of phenomenological approaches have been employed to describe these mechanisms: coulomb explosion, thermal spike, non-radiative exciton decay, bond weakening. However, a detailed microscopic description is missing due to the difficulty of modeling the time evolution of the electronic excitation. In this work we have employed molecular dynamics (MD) calculations to determine whether the irradiation effects are related to the thermal phenomena described by MD (in the ps domain) or to electronic phenomena (sub-ps domain), e.g., exciton localization. We have carried out simulations of up to 100 ps with large boxes (30x30x8 nm3) using a home-modified version of MDCASK that allows us to define a central hot cylinder (ion track) from which heat flows to the surrounding cold bath (unirradiated sample). We observed that once the cylinder has cooled down, the Si and O coordination numbers are 4 and 2, respectively, as in virgin silica. On the other hand, the density of the (cold) cylinder increases with respect to that of silica and, furthermore, the silica network ring size decreases. Both effects are in agreement with the observed densification. In conclusion, purely thermal effects do not explain the generation of point defects upon irradiation, but they do account for the silica densification.

Wireless communication enhancement methods for mobile robots in radiation environments

En entornos hostiles tales como aquellas instalaciones científicas donde la radiación ionizante es el principal peligro, el hecho de reducir las intervenciones humanas mediante el incremento de las operaciones robotizadas está siendo cada vez más de especial interés. CERN, la Organización Europea para la Investigación Nuclear, tiene alrededor de unos 50 km de superficie subterránea donde robots móviles controlador de forma remota podrían ayudar en su funcionamiento, por ejemplo, a la hora de llevar a cabo inspecciones remotas sobre radiación en los diferentes áreas destinados al efecto. No solo es preciso considerar que los robots deben ser capaces de recorrer largas distancias y operar durante largos periodos de tiempo, sino que deben saber desenvolverse en los correspondientes túneles subterráneos, tener en cuenta la presencia de campos electromagnéticos, radiación ionizante, etc. y finalmente, el hecho de que los robots no deben interrumpir el funcionamiento de los aceleradores. El hecho de disponer de un sistema de comunicaciones inalámbrico fiable y robusto es esencial para la correcta ejecución de las misiones que los robots deben afrontar y por supuesto, para evitar tales situaciones en las que es necesario la recuperación manual de los robots al agotarse su energía o al perder el enlace de comunicaciones. El objetivo de esta Tesis es proveer de las directrices y los medios necesarios para reducir el riesgo de fallo en la misión y maximizar las capacidades de los robots móviles inalámbricos los cuales disponen de almacenamiento finito de energía al trabajar en entornos peligrosos donde no se dispone de línea de vista directa. Para ello se proponen y muestran diferentes estrategias y métodos de comunicación inalámbrica. Teniendo esto en cuenta, se presentan a continuación los objetivos de investigación a seguir a lo largo de la Tesis: predecir la cobertura de comunicaciones antes y durante las misiones robotizadas; optimizar la capacidad de red inalámbrica de los robots móviles con respecto a su posición; y mejorar el rango operacional de esta clase de robots. Por su parte, las contribuciones a la Tesis se citan más abajo. El primer conjunto de contribuciones son métodos novedosos para predecir el consumo de energía y la autonomía en la comunicación antes y después de disponer de los robots en el entorno seleccionado. Esto es importante para proporcionar conciencia de la situación del robot y evitar fallos en la misión. El consumo de energía se predice usando una estrategia propuesta la cual usa modelos de consumo provenientes de diferentes componentes en un robot. La predicción para la cobertura de comunicaciones se desarrolla usando un nuevo filtro de RSS (Radio Signal Strength) y técnicas de estimación con la ayuda de Filtros de Kalman. El segundo conjunto de contribuciones son métodos para optimizar el rango de comunicaciones usando novedosas técnicas basadas en muestreo espacial que son robustas frente a ruidos de campos de detección y radio y que proporcionan redundancia. Se emplean métodos de diferencia central finitos para determinar los gradientes 2D RSS y se usa la movilidad del robot para optimizar el rango de comunicaciones y la capacidad de red. Este método también se valida con un caso de estudio centrado en la teleoperación háptica de robots móviles inalámbricos. La tercera contribución es un algoritmo robusto y estocástico descentralizado para la optimización de la posición al considerar múltiples robots autónomos usados principalmente para extender el rango de comunicaciones desde la estación de control al robot que está desarrollando la tarea. Todos los métodos y algoritmos propuestos se verifican y validan usando simulaciones y experimentos de campo con variedad de robots móviles disponibles en CERN. En resumen, esta Tesis ofrece métodos novedosos y demuestra su uso para: predecir RSS; optimizar la posición del robot; extender el rango de las comunicaciones inalámbricas; y mejorar las capacidades de red de los robots móviles inalámbricos para su uso en aplicaciones dentro de entornos peligrosos, que como ya se mencionó anteriormente, se destacan las instalaciones científicas con emisión de radiación ionizante. En otros términos, se ha desarrollado un conjunto de herramientas para mejorar, facilitar y hacer más seguras las misiones de los robots en entornos hostiles. Esta Tesis demuestra tanto en teoría como en práctica que los robots móviles pueden mejorar la calidad de las comunicaciones inalámbricas mediante la profundización en el estudio de su movilidad para optimizar dinámicamente sus posiciones y mantener conectividad incluso cuando no existe línea de vista. Los métodos desarrollados en la Tesis son especialmente adecuados para su fácil integración en robots móviles y pueden ser aplicados directamente en la capa de aplicación de la red inalámbrica. ABSTRACT In hostile environments such as in scientific facilities where ionising radiation is a dominant hazard, reducing human interventions by increasing robotic operations are desirable. CERN, the European Organization for Nuclear Research, has around 50 km of underground scientific facilities, where wireless mobile robots could help in the operation of the accelerator complex, e.g. in conducting remote inspections and radiation surveys in different areas. The main challenges to be considered here are not only that the robots should be able to go over long distances and operate for relatively long periods, but also the underground tunnel environment, the possible presence of electromagnetic fields, radiation effects, and the fact that the robots shall in no way interrupt the operation of the accelerators. Having a reliable and robust wireless communication system is essential for successful execution of such robotic missions and to avoid situations of manual recovery of the robots in the event that the robot runs out of energy or when the robot loses its communication link. The goal of this thesis is to provide means to reduce risk of mission failure and maximise mission capabilities of wireless mobile robots with finite energy storage capacity working in a radiation environment with non-line-of-sight (NLOS) communications by employing enhanced wireless communication methods. Towards this goal, the following research objectives are addressed in this thesis: predict the communication range before and during robotic missions; optimise and enhance wireless communication qualities of mobile robots by using robot mobility and employing multi-robot network. This thesis provides introductory information on the infrastructures where mobile robots will need to operate, the tasks to be carried out by mobile robots and the problems encountered in these environments. The reporting of research work carried out to improve wireless communication comprises an introduction to the relevant radio signal propagation theory and technology followed by explanation of the research in the following stages: An analysis of the wireless communication requirements for mobile robot for different tasks in a selection of CERN facilities; predictions of energy and communication autonomies (in terms of distance and time) to reduce risk of energy and communication related failures during missions; autonomous navigation of a mobile robot to find zone(s) of maximum radio signal strength to improve communication coverage area; and autonomous navigation of one or more mobile robots acting as mobile wireless relay (repeater) points in order to provide a tethered wireless connection to a teleoperated mobile robot carrying out inspection or radiation monitoring activities in a challenging radio environment. The specific contributions of this thesis are outlined below. The first sets of contributions are novel methods for predicting the energy autonomy and communication range(s) before and after deployment of the mobile robots in the intended environments. This is important in order to provide situational awareness and avoid mission failures. The energy consumption is predicted by using power consumption models of different components in a mobile robot. This energy prediction model will pave the way for choosing energy-efficient wireless communication strategies. The communication range prediction is performed using radio signal propagation models and applies radio signal strength (RSS) filtering and estimation techniques with the help of Kalman filters and Gaussian process models. The second set of contributions are methods to optimise the wireless communication qualities by using novel spatial sampling based techniques that are robust to sensing and radio field noises and provide redundancy features. Central finite difference (CFD) methods are employed to determine the 2-D RSS gradients and use robot mobility to optimise the communication quality and the network throughput. This method is also validated with a case study application involving superior haptic teleoperation of wireless mobile robots where an operator from a remote location can smoothly navigate a mobile robot in an environment with low-wireless signals. The third contribution is a robust stochastic position optimisation algorithm for multiple autonomous relay robots which are used for wireless tethering of radio signals and thereby to enhance the wireless communication qualities. All the proposed methods and algorithms are verified and validated using simulations and field experiments with a variety of mobile robots available at CERN. In summary, this thesis offers novel methods and demonstrates their use to predict energy autonomy and wireless communication range, optimise robots position to improve communication quality and enhance communication range and wireless network qualities of mobile robots for use in applications in hostile environmental characteristics such as scientific facilities emitting ionising radiations. In simpler terms, a set of tools are developed in this thesis for improving, easing and making safer robotic missions in hostile environments. This thesis validates both in theory and experiments that mobile robots can improve wireless communication quality by exploiting robots mobility to dynamically optimise their positions and maintain connectivity even when the (radio signal) environment possess non-line-of-sight characteristics. The methods developed in this thesis are well-suited for easier integration in mobile robots and can be applied directly at the application layer of the wireless network. The results of the proposed methods have outperformed other comparable state-of-the-art methods.

A tool for the automatic analysis of single events effects on electronic circuits

Nowadays integrated circuit reliability is challenged by both variability and working conditions. Environmental radiation has become a major issue when ensuring the circuit correct behavior. The required radiation and later analysis performed to the circuit boards is both fund and time expensive. The lack of tools which support pre-manufacturing radiation hardness analysis hinders circuit designers tasks. This paper describes an extensively customizable simulation tool for the characterization of radiation effects on electronic systems. The proposed tool can produce an in depth analysis of a complete circuit in almost any kind of radiation environment in affordable computation times.

Self-reference Scrubber for TMR Systems Based on Xilinx Virtex FPGAs

SRAM-based FPGAs are sensitive to radiation effects. Soft errors can appear and accumulate, potentially defeating mitigation strategies deployed at the Application Layer. Therefore, Configuration Memory scrubbing is required to improve radiation tolerance of such FPGAs in space applications. Virtex FPGAs allow runtime scrubbing by means of dynamic partial reconfiguration. Even with scrubbing, intra-FPGA TMR systems are subjected to common-mode errors affecting more than one design domain. This is solved in inter-FPGA TMR systems at the expense of a higher cost, power and mass. In this context, a self-reference scrubber for device-level TMR system based on Xilinx Virtex FPGAs is presented. This scrubber allows for a fast SEU/MBU detection and correction by peer frame comparison without needing to access a golden configuration memory

MMonCa: A flexible and powerful new Kinetic Monte Carlo simulator

Kinetic Monte Carlo (KMC) is a widely used technique to simulate the evolution of radiation damage inside solids. Despite de fact that this technique was developed several decades ago, there is not an established and easy to access simulating tool for researchers interested in this field, unlike in the case of molecular dynamics or density functional theory calculations. In fact, scientists must develop their own tools or use unmaintained ones in order to perform these types of simulations. To fulfil this need, we have developed MMonCa, the Modular Monte Carlo simulator. MMonCa has been developed using professional C++ programming techniques and has been built on top of an interpreted language to allow having a powerful yet flexible, robust but customizable and easy to access modern simulator. Both non lattice and Lattice KMC modules have been developed. We will present in this conference, for the first time, the MMonCa simulator. Along with other (more detailed) contributions in this meeting, the versatility of MMonCa to study a number of problems in different materials (particularly, Fe and W) subject to a wide range of conditions will be shown. Regarding KMC simulations, we have studied neutron-generated cascade evolution in Fe (as a model material). Starting with a Frenkel pair distribution we have followed the defect evolution up to 450 K. Comparison with previous simulations and experiments shows excellent agreement. Furthermore, we have studied a more complex system (He-irradiated W:C) using a previous parametrization [1]. He-irradiation at 4 K followed by isochronal annealing steps up to 500 K has been simulated with MMonCa. The He energy was 400 eV or 3 keV. In the first case, no damage is associated to the He implantation, whereas in the second one, a significant Frenkel pair concentration (evolving into complex clusters) is associated to the He ions. We have been able to explain He desorption both in the absence and in the presence of Frenkel pairs and we have also applied MMonCa to high He doses and fluxes at elevated temperatures. He migration and trapping dominate the kinetics of He desorption. These processes will be discussed and compared to experimental results. [1] C.S. Becquart et al. J. Nucl. Mater. 403 (2010) 75

Effect of ion flux on helium retention in helium-irradiated tungsten

Helium retention in irradiated tungsten leads to swelling, pore formation, sample exfoliation and embrittlement with deleterious consequences in many applications. In particular, the use of tungsten in future nuclear fusion plants is proposed due to its good refractory properties. However, serious concerns about tungsten survivability stems from the fact that it must withstand severe irradiation conditions. In magnetic fusion as well as in inertial fusion (particularly with direct drive targets), tungsten components will be exposed to low and high energy ion (helium) irradiation, respectively. A common feature is that the most detrimental situations will take place in pulsed mode, i.e., high flux irradiation. There is increasing evidence on a correlation between a high helium flux and an enhancement of detrimental effects on tungsten. Nevertheless, the nature of these effects is not well understood due to the subtleties imposed by the exact temperature profile evolution, ion energy, pulse duration, existence of impurities and simultaneous irradiation with other species. Physically based Kinetic Monte Carlo is the technique of choice to simulate the evolution of radiation-induced damage inside solids in large temporal and space scales. We have used the recently developed code MMonCa (Modular Monte Carlo simulator), presented in this conference for the first time, to study He retention (and in general defect evolution) in tungsten samples irradiated with high intensity helium pulses. The code simulates the interactions among a large variety of defects and impurities (He and C) during the irradiation stage and the subsequent annealing steps. In addition, it allows us to vary the sample temperature to follow the severe thermo-mechanical effects of the pulses. In this work we will describe the helium kinetics for different irradiation conditions. A competition is established between fast helium cluster migration and trapping at large defects, being the temperature a determinant factor. In fact, high temperatures (induced by the pulses) are responsible for large vacancy cluster formation and subsequent additional trapping with respect to low flux irradiation.

Electrodynamic tether at Jupiter 2. Tour missions after capture

Three separate scenarios of an electrodynamic tether mission at Jupiter following capture of a spacecraft (SC) into an equatorial, highly elliptical orbit around the planet, with perijove at about 1.5 times the Jovian radius, are discussed. Repeated application of Lorentz drag on the spinning tether, at the perijove vicinity, can progressively lower the apojove. One mission involves the tethered-SC rapidly and frequently visiting Galilean moons; elliptical orbits with apojove down at the Ganymede, Europa, and Io orbits are in 2:5, 4:9, and 1:2 resonances with the respective moons. About 20 slow flybys of Io would take place before the accumulated radiation dose exceeds 3 Mrad (Si) at 10 mm Al shield thickness, with a total duration of 5 months after capture (4 months for lowering the apojove to Io and one month for the flybys). The respective number of flybys for Ganymede would be 10 with a total duration of about 9 months. An alternative mission would have the SC acquire a low circular orbit around Jupiter, below the radiation belts, and manoeuvre to get an optimal altitude, with no major radiation effects, in less than 5 months after capture. In a third mission, repeated thrusting at the apojove vicinity, once down at the Io torus, would raise the perijove itself to the torus to acquire a low circular orbit around Io in about 4 months, for a total of 8 months after capture; this corresponds, however, to over 100 apojove passes with an accumulated dose, of about 8.5 Mrad (Si), that poses a critical issue.

Design techniques for xilinx virtex FPGA configuration memory scrubbers

SRAM-based FPGAs are in-field reconfigurable an unlimited number of times. This characteristic, together with their high performance and high logic density, proves to be very convenient for a number of ground and space level applications. One drawback of this technology is that it is susceptible to ionizing radiation, and this sensitivity increases with technology scaling. This is a first order concern for applications in harsh radiation environments, and starts to be a concern for high reliability ground applications. Several techniques exist for coping with radiation effects at user application. In order to be effective they need to be complemented with configuration memory scrubbing, which allows error mitigation and prevents failures due to error accumulation. Depending on the radiation environment and on the system dependability requirements, the configuration scrubber design can become more or less complex. This paper classifies and presents current and novel design methodologies and architectures for SRAM-based FPGAs, and in particular for Xilinx Virtex-4QV/5QV, configuration memory scrubbers.

Frequency-dependent opacity calculations for radiation transport simulations

We will present recent developments in the calculation of opacity tables suitable for including in the radiation hydrodynamic code ARWEN [1] to study processes like ICF or X-ray secondary sources. For these calculations we use the code BiG BART in LTE conditions, with self-consistent data generated with the Flexible Atomic Code (FAC) [2]. Non-LTE effects are approximately taken into account by means of the improved RADIOM model [3], which makes use of existing LTE data tables.

Effects of dietary restriction combined with different exercise programs or physical activity recommendations on blood lipids in overweight adults

Background and aim: Many exercise studies, although generally showing the beneficial effects of supervised aerobic, resistance or combined exercise on blood lipids, have sometimes reached equivocal conclusions. The aim of this study is to evaluate the impact of different programs that combined exercise and dietary restriction on blood lipids versus a clinical practice intervention for weight loss, in overweight adults. Methods: For this study 66 subjects participated in a supervised 22 weeks training program, composed of three sessions per week and they were randomized in three groups: strength training (S; n = 19), endurance training (E; n = 25), a combination of E and S (SE; n = 22). Eighteen subjects served as physical activity group (PA) that followed a clinical intervention consisted of physical activity recommendations. All groups followed the same dietary treatment, and blood samples were obtained for lipids measurements, at the beginning and end of the study. Results: Lipid profile improved in all groups. No significant differences for baseline and post-training values were observed between groups. In general, SE and PA decreased low-density lipoprotein cholesterol (LDL-C) values (p menor que 0.01). S decreased triglyceride levels (p menor que 0.01) and E, SE, and PA decreased total cholesterol levels (p menor que 0.05, p menor que 0.01 and p menor que 0.01, respectively). Conclusions: These results suggest that an intervention program of supervised exercise combined with diet restriction did not achieved further improvements in blood lipid profile than diet restriction and physical activity recommendations, in overweight adults. (Clinical Trials gov number: NCT01116856).

Running away from side effects: physical exercise as a complementary intervention for breast cancer patients

The number of breast cancer survivors increases every year, thanks to the development of new treatments and screening techniques. However, patients present with numerous side effects that may affect their quality of life. Exercise has been demostrated to reduce some of these side effects, but in spite of this, few breast cancer patientes know and follow the exercise recommendations needed to remain healthy. In this review, we describe the differente breast cancer treatments and the related side effects and implications of exercise in relation to these. We propose that exercise could be and integrative complementary intervention to improve physiological, physical and psychological factors that affect survival and quality of life of these patients. For that reason, the main objective of this review is to provide a general overview of exercise benefits in breast cancer patients and recommendations of how to design exercise interventions in patients with different side effects.

Short-term effects of four tillage practices on soil physical properties, soil water potential, and maize yield

The area cultivated using conservation tillage has recently increased in central Spain. However, soil compaction and water retention with conservation tillage still remains a genuine concern for landowners in this region be- cause of its potential effect on the crop growth and yield. The aim of this research is to determine the short- term influences of four tillage treatments on soil physical properties. In the experiment, bulk density, cone index, soil water potential, soil temperature and maize (Zea mays L.) productivity have been measured. A field experiment was established in spring of 2013 on a loamy soil. The experiment compared four tillage methods (zero tillage, ZT; reservoir tillage, RT; minimum tillage, MT; and conventional tillage, CT). Soil bulk density and soil cone index were measured during maize growing season and at harvesting time. Furthermore, the soil water potential was monitored by using a wireless sensors network with sensors at 20 and 40 cm depths. Also, soil temperatures were registered at depths of 5 and 12 cm. Results indicated that there were significant differ- ences between soil bulk density and cone index of ZT method and those of RT, MT, and CT, during the growing season; although, this difference was not significant at the time of harvesting in some soil layers. Overall, in most soil layers, tillage practice affected bulk density and cone index in the order: ZT N RT N MT N CT. Regardless oftheentireobservationperiod,results exhibited that soils under ZT and RT treatments usually resulted in higher water potential and lower soil temperature than the other two treatments at both soil depths. In addition, clear differences in maize grain yield were observed between ZT and CT treatments, with a grain yield (up to 15.4%) increase with the CT treatment. On the other hand, no significant differences among (RT, MT, and CT) on maizeyieldwerefound.Inconclusion,the impact of soil compaction increase and soil temperature decrease,pro- duced by ZT treatment is a potential reason for maize yield reduction in this tillage method. We found that RT could be certainly a viable option for farmers incentral Spain,particularly when switching to conservation tillage from conventional tillage. This technique showed a moderate and positive effect on soil physical properties and increased maize yields compared to ZT and MT, and provides an opportunity to stabilize maize yields compared to CT.

Integration of physical, chemical and biological tactics against insect pests and virus diseases in horticultural crops

Actualmente, la gestión de sistemas de Manejo Integrado de Plagas (MIP) en cultivos hortícolas tiene por objetivo priorizar los métodos de control no químicos en detrimento del consumo de plaguicidas, según recoge la directiva europea 2009/128/CE ‘Uso Sostenible de Plaguicidas’ (OJEC, 2009). El uso de agentes de biocontrol como alternativa a la aplicación de insecticidas es un elemento clave de los sistemas MIP por sus innegables ventajas ambientales que se utiliza ampliamente en nuestro país (Jacas y Urbaneja, 2008). En la región de Almería, donde se concentra el 65% de cultivo en invernadero de nuestro país (47.367 ha), MIP es la principal estrategia en pimiento (MAGRAMA, 2014), y comienza a serlo en otros cultivos como tomate o pepino. El cultivo de pepino, con 8.902 ha (MAGRAMA, 2013), tiene un protocolo semejante al pimiento (Robledo et al., 2009), donde la única especie de pulgón importante es Aphis gossypii Glover. Sin embargo, pese al continuo incremento de la superficie de cultivo agrícola bajo sistemas MIP, los daños originados por virosis siguen siendo notables. Algunos de los insectos presentes en los cultivos de hortícolas son importantes vectores de virus, como los pulgones, las moscas blancas o los trips, cuyo control resulta problemático debido a su elevada capacidad para transmitir virus vegetales incluso a una baja densidad de plaga (Holt et al., 2008; Jacas y Urbaneja, 2008). Las relaciones que se establecen entre los distintos agentes de un ecosistema son complejas y muy específicas. Se ha comprobado que, pese a que los enemigos naturales reducen de manera beneficiosa los niveles de plaga, su incorporación en los sistemas planta-insecto-virus puede desencadenar complicadas interacciones con efectos no deseables (Dicke y van Loon, 2000; Jeger et al., 2011). Así, los agentes de biocontrol también pueden inducir a que los insectos vectores modifiquen su comportamiento como respuesta al ataque y, con ello, el grado de dispersión y los patrones de distribución de las virosis que transmiten (Bailey et al., 1995; Weber et al., 1996; Hodge y Powell, 2008a; Hodge et al., 2011). Además, en ocasiones el control biológico por sí solo no es suficiente para controlar determinadas plagas (Medina et al., 2008). Entre los métodos que se pueden aplicar bajo sistemas MIP están las barreras físicas que limitan la entrada de plagas al interior de los invernaderos o interfieren con su movimiento, como pueden ser las mallas anti-insecto (Álvarez et al., 2014), las mallas fotoselectivas (Raviv y Antignus, 2004; Weintraub y Berlinger, 2004; Díaz y Fereres, 2007) y las mallas impregnadas en insecticida (Licciardi et al., 2008; Martin et al., 2014). Las mallas fotoselectivas reducen o bloquean casi por completo la transmisión de radiación UV, lo que interfiere con la visión de los insectos y dificulta o impide la localización del cultivo y su establecimiento en el mismo (Raviv y Antignus, 2004; Weintraub, 2009). Se ha comprobado cómo su uso puede controlar los pulgones y las virosis en cultivo de lechuga (Díaz et al., 2006; Legarrea et al., 2012a), así como la mosca blanca, los trips y los ácaros, y los virus que estos transmiten en otros cultivos (Costa y Robb, 1999; Antignus et al., 2001; Kumar y Poehling, 2006; Doukas y Payne, 2007a; Legarrea et al., 2010). Sin embargo, no se conoce perfectamente el modo de acción de estas barreras, puesto que existe un efecto directo sobre la plaga y otro indirecto mediado por la planta, cuya fisiología cambia al desarrollarse en ambientes con falta de radiación UV, y que podría afectar al ciclo biológico de los insectos fitófagos (Vänninen et al., 2010; Johansen et al., 2011). Del mismo modo, es necesario estudiar la compatibilidad de esta estrategia con los enemigos naturales de las plagas. Hasta la fecha, los estudios han evidenciado que los agentes de biocontrol pueden realizar su actividad bajo ambientes pobres en radiación UV (Chyzik et al., 2003; Chiel et al., 2006; Doukas y Payne, 2007b; Legarrea et al., 2012c). Otro método basado en barreras físicas son las mallas impregnadas con insecticidas, que se han usado tradicionalmente en la prevención de enfermedades humanas transmitidas por mosquitos (Martin et al., 2006). Su aplicación se ha ensayado en agricultura en ciertos cultivos al aire libre (Martin et al., 2010; Díaz et al., 2004), pero su utilidad en cultivos protegidos para prevenir la entrada de insectos vectores en invernadero todavía no ha sido investigada. Los aditivos se incorporan al tejido durante el proceso de extrusión de la fibra y se liberan lentamente actuando por contacto en el momento en que el insecto aterriza sobre la malla, con lo cual el riesgo medioambiental y para la salud humana es muy limitado. Los plaguicidas que se emplean habitualmente suelen ser piretroides (deltametrina o bifentrín), aunque también se ha ensayado dicofol (Martin et al., 2010) y alfa-cipermetrina (Martin et al., 2014). Un factor que resulta de vital importancia en este tipo de mallas es el tamaño del poro para facilitar una buena ventilación del cultivo, al tiempo que se evita la entrada de insectos de pequeño tamaño como las moscas blancas (Bethke y Paine, 1991; Muñoz et al., 1999). Asimismo, se plantea la necesidad de estudiar la compatibilidad de estas mallas con los enemigos naturales. Es por ello que en esta Tesis Doctoral se plantea la necesidad de evaluar nuevas mallas impregnadas que impidan el paso de insectos de pequeño tamaño al interior de los invernaderos, pero que a su vez mantengan un buen intercambio y circulación de aire a través del poro de la malla. Así, en la presente Tesis Doctoral, se han planteado los siguientes objetivos generales a desarrollar: 1. Estudiar el impacto de la presencia de parasitoides sobre el grado de dispersión y los patrones de distribución de pulgones y las virosis que éstos transmiten. 2. Conocer el efecto directo de ambientes pobres en radiación UV sobre el comportamiento de vuelo de plagas clave de hortícolas y sus enemigos naturales. 3. Evaluar el efecto directo de la radiación UV-A sobre el crecimiento poblacional de pulgones y mosca blanca, y sobre la fisiología de sus plantas hospederas, así como el efecto indirecto de la radiación UV-A en ambas plagas mediado por el crecimiento de dichas planta hospederas. 4. Caracterización de diversas mallas impregnadas en deltametrina y bifentrín con diferentes propiedades y selección de las óptimas para el control de pulgones, mosca blanca y sus virosis asociadas en condiciones de campo. Estudio de su compatibilidad con parasitoides. ABSTRACT Insect vectors of plant viruses are the main agents causing major economic losses in vegetable crops grown under protected environments. This Thesis focuses on the implementation of new alternatives to chemical control of insect vectors under Integrated Pest Management programs. In Spain, biological control is the main pest control strategy used in a large part of greenhouses where horticultural crops are grown. The first study aimed to increase our knowledge on how the presence of natural enemies such as Aphidius colemani Viereck may alter the dispersal of the aphid vector Aphis gossypii Glover (Chapter 4). In addition, it was investigated if the presence of this parasitoid affected the spread of aphid-transmitted viruses Cucumber mosaic virus (CMV, Cucumovirus) and Cucurbit aphid-borne yellows virus (CABYV, Polerovirus) infecting cucumber (Cucumis sativus L). SADIE methodology was used to study the distribution patterns of both the virus and its vector, and their degree of association. Results suggested that parasitoids promoted aphid dispersal in the short term, which enhanced CMV spread, though consequences of parasitism suggested potential benefits for disease control in the long term. Furthermore, A. colemani significantly limited the spread and incidence of the persistent virus CABYV in the long term. The flight activity of pests Myzus persicae (Sulzer), Bemisia tabaci (Gennadius) and Tuta absoluta (Meyrick), and natural enemies A. colemani and Sphaerophoria rueppellii (Weidemann) under UV-deficient environments was studied under field conditions (Chapter 5). One-chamber tunnels were covered with cladding materials with different UV transmittance properties. Inside each tunnel, insects were released from tubes placed in a platform suspended from the ceiling. Specific targets were located at different distances from the platform. The ability of aphids and whiteflies to reach their targets was diminished under UV-absorbing barriers, suggesting a reduction of vector activity under this type of nets. Fewer aphids reached distant traps under UV-absorbing nets, and significantly more aphids could fly to the end of the tunnels covered with non-UV blocking materials. Unlike aphids, differences in B. tabaci captures were mainly found in the closest targets. The oviposition of lepidopteran T. absoluta was also negatively affected by a UV-absorbing cover. The photoselective barriers were compatible with parasitism and oviposition of biocontrol agents. Apart from the direct response of insects to UV radiation, plant-mediated effects influencing insect performance were investigated (Chapter 6). The impact of UV-A radiation on the performance of aphid M. persicae and whitefly B. tabaci, and growth and leaf physiology of host plants pepper and eggplant was studied under glasshouse conditions. Plants were grown inside cages covered by transparent and UV-A-opaque plastic films. Plant growth and insect fitness were monitored. Leaves were harvested for chemical analysis. Pepper plants responded directly to UV-A by producing shorter stems whilst UV-A did not affect the leaf area of either species. UV-A-treated peppers had higher content of secondary metabolites, soluble carbohydrates, free amino acids and proteins. Such changes in tissue chemistry indirectly promoted aphid performance. For eggplants, chlorophyll and carotenoid levels decreased with supplemental UVA but phenolics were not affected. Exposure to supplemental UV-A had a detrimental effect on whitefly development, fecundity and fertility presumably not mediated by plant cues, as compounds implied in pest nutrition were unaltered. Lastly, the efficacy of a wide range of Long Lasting Insecticide Treated Nets (LLITNs) was studied under laboratory and field conditions. This strategy aimed to prevent aphids and whiteflies to enter the greenhouse by determining the optimum mesh size (Chapter 7). This new approach is based on slow release deltamethrin- and bifenthrin-treated nets with large hole sizes that allow improved ventilation of greenhouses. All LLITNs produced high mortality of M. persicae and A. gossypii although their efficacy decreased over time with sun exposure. It was necessary a net with hole size of 0.29 mm2 to exclude B. tabaci under laboratory conditions. The feasibility of two selected nets was studied in the field under a high insect infestation pressure in the presence of CMV- and CABYV-infected cucumber plants. Besides, the compatibility of parasitoid A. colemani with bifenthrin-treated nets was studied in parallel field experiments. Both nets effectively blocked the invasion of aphids and reduced the incidence of both viruses, however they failed to exclude whiteflies. We found that our LLITNs were compatible with parasitoid A. colemani. As shown, the role of natural enemies has to be taken into account regarding the dispersal of insect vectors and subsequent spread of plant viruses. The additional benefits of novel physicochemical barriers, such as photoselective and insecticide-impregnated nets, need to be considered in Integrated Pest Management programs of vegetable crops grown under protected environments.