998 resultados para Controlled vocabulary


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An architecture to simultaneously affect both amplitude and phase control from a reflectarray element using an impedance transformation unit is demonstrated. It is shown that a wide range of control is possible from a single element, removing the conventional necessity for variable sized elements across an array in order to form a desired reflectarray far-field pattern. Parallel plate waveguide measurements for a 2.2 GHz prototype element validate the phase and amplitude variation available from the element. It is demonstrated that there is sufficient control of the element's reflection response to allow Dolph-Tschebyscheff weighting coefficients for major-lobe to side-lobe ratios of up to 36 dB to be implemented.

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OBJECTIVE: This study was undertaken to compare preprandial and postprandial capillary glucose monitoring in pregnant women with type 1 diabetes.

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The enhanced optical properties of metal films periodically perforated with an array of sub-wavelength size holes have recently been widely studied in the field of surface plasmon optics. The ability to design the optical transmission of such nanostructures, which act as plasmonic crystals, by varying their geometrical parameters gives them great flexibility for numerous applications in photonics, opto-electronics, and sensing. Transforming these passive optical elements into devices that may be actively controlled has presented a new challenge. Here, we report on the realization of an electrically controlled nanostructured optical system based on the unique properties of surface plasmon polaritonic crystals in contact with a liquid crystal (LC) layer. We discuss the effect of LC layer modulation on the surface plasmon dispersion, the related optical transmission and the underlying mechanism. The reported effect may be used to achieve active spectral tuneability and switching in a wide range of applications.

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This paper describes a randomised controlled trial (RCT) investigation of the added value of systemic family therapy (SFT) over individually focused cognitive behavioural therapy (CBT) for families in which one or more members has suffered trauma and been referred to a community-based psychotherapy centre. The results illustrate how an apparently robust design can be confounded by high attrition rates, low average number of therapeutic sessions and poor protocol adherence. The paper highlights a number of general and specific lessons regarding the resources and processes involved that can act as a model for those planning to undertake studies of this type and scope. A key message is that the challenges of conducting RCTs in ‘real world’ settings should not be underestimated. The wider implications in relation to the place of RCTs within the creation of the evidence base for complex psycho-social interventions is discussed and the current movement towards a phased mixed-methods approach, including the appropriate use of RCTs, which some might argue is a return to the original vision of evidence-based practice (EBP), is affirmed.

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Guided transport of a relativistic electron beam in solid is achieved experimentally by exploiting the strong magnetic fields created at the interface of two metals of different electrical resistivities. This is of substantial relevance to the Fast Ignitor approach to fusion energy production [M. Tabak et al., Phys. Plasmas 12, 057305 (2005)], since it allows the electron deposition to be spatially tailored-thus adding substantial design flexibility and preventing inefficiencies due to electron beam spreading. In the experiment, optical transition radiation and thermal emission from the target rear surface provide a clear signature of the electron confinement within a high resistivity tin layer sandwiched transversely between two low resistivity aluminum slabs. The experimental data are found to agree well with numerical simulations.