Linear Model-Based Predictive Control of the LHC 1.8 K Cryogenic Loop

The LHC accelerator will employ 1800 superconducting magnets (for guidance and focusing of the particle beams) in a pressurized superfluid helium bath at 1.9 K. This temperature is a severely constrained control parameter in order to avoid the transition from the superconducting to the normal state. Cryogenic processes are difficult to regulate due to their highly non-linear physical parameters (heat capacity, thermal conductance, etc.) and undesirable peculiarities like non self-regulating process, inverse response and variable dead time. To reduce the requirements on either temperature sensor or cryogenic system performance, various control strategies have been investigated on a reduced-scale LHC prototype built at CERN (String Test). Model Based Predictive Control (MBPC) is a regulation algorithm based on the explicit use of a process model to forecast the plant output over a certain prediction horizon. This predicted controlled variable is used in an on-line optimization procedure that minimizes an appropriate cost function to determine the manipulated variable. One of the main characteristics of the MBPC is that it can easily incorporate process constraints; therefore the regulation band amplitude can be substantially reduced and optimally placed. An MBPC controller has completed a run where performance and robustness has been compared against a standard PI controller (Proportional and Integral)

Non-Linear Advanced Control of the LHC Inner Triplet Heat Exchanger Test Unit

The future Large Hadron Collider (LHC) at CERN will include eight interaction region final focus magnet systems, the so-called "Inner Triplet", one on each side of the four beam collision points. The Inner Triplets will be cooled in a static bath of pressurized He II nominally at 1.9 K. This temperature is a control parameter and has very severe constraints in order to avoid the transition from the superconducting to normal resistive state. The main difference in these special zones with respect to a regular LHC cell is higher dynamic heat load unevenly distributed which modifies largely the process characteristics and hence the controller performance. Several control strategies have already been tested at CERN in a pilot plant (LHC String Test) which reproduced a LHC half-cell. In order to validate a common control structure along the whole LHC ring, a Nonlinear Model Predictive Control (NMPC) has been developed and implemented in the Inner Triplet Heat Exchanger Unit (IT-HXTU) at CERN. Automation of the Inner Triplet setup and the advanced control techniques deployed based on the Model Based Predictive Control (MBPC) principle are presented

Behavioural features of cerebral visual impairment are common in children with down syndrome

It is widely recognised that children with Down syndrome have a broad range and a high prevalence of visual deficits and it has been suggested that those with Down syndrome are more likely to exhibit visual perception deficits indicative of cerebral visual impairment. This exploratory study aims to determine the prevalence of behavioural features suggestive of cerebral visual impairment (CVI) occurring with Down syndrome and whether the visual problems can be ascribed to optometric factors. A cohort of 226 families of children with Down syndrome (trisomy 21), aged 4–17, were invited to participate in a validated question inventory, to recognise visual perception issues. The clinical records of the participants were then reviewed retrospectively. A five-question screening instrument was used to indicate suspected CVI. The majority of the 81 families who responded to the questionnaire reported some level of visual perceptual difficulty in their child. Among this cohort, the prevalence of suspected CVI as indicated by the screening questionnaire was 38%. Only ametropia was found to have a significant association with suspected CVI, although this increased the correct prediction of suspected CVI outcome by only a small amount. Results suggest that children with Down syndrome are more likely to experience problems consistent with cerebral visual impairment, and that these may originate from a similar brain dysfunction to that which contributes to high levels of ametropia and failure to emmetropise. It is important that behavioural features of CVI are recognised in children with Down syndrome, further investigations initiated and appropriate management applied.V. Vinuela-Navarro and R. England were funded by Action Medical Research for Children GN2338.Peer ReviewedPostprint (author's final draft

Applying Advanced Control Techniques for Temperature Regulation of the LHC Superconducting Magnets

The temperature of the superconducting magnets for the future LHC accelerator is a control parameter with strict operating constraints imposed by (a) the maximum temperature at which the magnets can o perate, (b) the cooling capacity of the cryogenic system, (c) the variability of applied heat loads and (d) the accuracy of the instrumentation. A temperature regulation with narrow control band can i n principle be achieved by implementing a Model Predictive Control (MPC)-type controller. For this purpose, and for investigating the behaviour of the cooling system, a simulation program has been dev eloped. A prototype MPC controller has been installed and completed its first run

Utilidad de la reconstrucción tridimensional con tomografía computarizada en Traumatología y Ortopedia

La reconstrucción tridimensional es una nuev a técnica diagnóstica introducida en cirugía ortopédica y traumatología. Está indicada en algunas fracturas de acetábulo, columna y pelvis porque facilita una visión desde diferente s ángulos y en determinadas lesiones congénitas donde es imprescindible una correcta evaluación preoperatoria. Presentamo s dos paciente s con fracturas acetabulares, otro con lesión me - tastásica en columna lumbar y otro con hipoplasia del arco neural de cuarta vértebra lumbar. La reconstrucción tridimensional fue útil para el definitivo diagnóstico en los cuatro pacientes.Three dimensional images is a new technique introduced in orthopaedic surgery and traumatology. It's indicated for some fractures of the acetabulum, spine or pelvic girdle becaus e supply a vision from differents angles and in determinated congenital damage s who is indispensable an accurate evaluation before the surgery. We presented two patients with acetabular fractures, other with a metastasi c tumour in lumbar spine and anothe r with a hipoplasti c neural arch in a lumbar vertebra. The thre e dimensional reconstruction was useful for the definitive diagnostic in the four patients

The action of obestatin in skeletal muscle repair: stem cell expansion, muscle growth, and microenvironment remodeling

The development of therapeutic strategies for skeletal muscle diseases, such as physical injuries and myopathies, depends on the knowledge of regulatory signals that control the myogenic process. The obestatin/GPR39 system operates as an autocrine signal in the regulation of skeletal myogenesis. Using a mouse model of skeletal muscle regeneration after injury and several cellular strategies, we explored the potential use of obestatin as a therapeutic agent for the treatment of trauma-induced muscle injuries. Our results evidenced that the overexpression of the preproghrelin, and thus obestatin, and GPR39 in skeletal muscle increased regeneration after muscle injury. More importantly, the intramuscular injection of obestatin significantly enhanced muscle regeneration by simulating satellite stem cell expansion as well as myofiber hypertrophy through a kinase hierarchy. Added to the myogenic action, the obestatin administration resulted in an increased expression of VEGF/VEGFR2 and the consequent microvascularization, with no effect on collagen deposition in skeletal muscle. Furthermore, the potential inhibition of myostatin during obestatin treatment might contribute to its myogenic action improving muscle growth and regeneration. Taken together, our data demonstrate successful improvement of muscle regeneration, indicating obestatin is a potential therapeutic agent for skeletal muscle injury and would benefit other myopathies related to muscle regeneration

Apostillas al «Teatro completo» de Quevedo

This article provides a series of details proposing explanations for different passages of Quevedo’s theater, completing the editors’ annotation of Francisco de Quevedo’s Teatro completo, Ignacio Arellano and Celsa Carmen García Valdés, Madrid, Cátedra, 2011.Este artículo aporta una serie de apostillas y precisiones proponiendo explicaciones para distintos pasajes del teatro de Quevedo, completando la anotación de los editores del Teatro completo de Francisco de Quevedo, Ignacio Arellano y Celsa Carmen García Valdés, Madrid, Cátedra, 2011

Avian predators as a biological control system of common vole (Microtus arvalis) populations in NW Spain: experimental set-up and preliminary results

Jareño, D., Paz, A., Arroyo, L., Viñuela, J., Arroyo, B.E., Mougeot, F., Luque-Larena, J.J., Fargallo, J.A