Mg-Ni-H films as selective coatings: tunable reflectance by layered hydrogenation

Unlike other switchable mirrors, Mg2NiHx films show large changes in reflection that yield very low reflectance (high absorptance) at different hydrogen contents, far before reaching the semiconducting state. The resulting reflectance patterns are of interference origin, due to a self-organized layered hydrogenation mechanism that starts at the substrate interface, and can therefore be tuned by varying the film thickness. This tunability, together with the high absorptance contrast observed between the solar and the thermal energies, strongly suggests the use of these films in smart coatings for solar applications.Comment: Three two-column pages with 3 figures embedded; RevTE

Using graph transformation algorithms to generate natural language equivalents of icons expressing medical concepts

A graphical language addresses the need to communicate medical information in a synthetic way. Medical concepts are expressed by icons conveying fast visual information about patients' current state or about the known effects of drugs. In order to increase the visual language's acceptance and usability, a natural language generation interface is currently developed. In this context, this paper describes the use of an informatics method ---graph transformation--- to prepare data consisting of concepts in an OWL-DL ontology for use in a natural language generation component. The OWL concept may be considered as a star-shaped graph with a central node. The method transforms it into a graph representing the deep semantic structure of a natural language phrase. This work may be of future use in other contexts where ontology concepts have to be mapped to half-formalized natural language expressions.Comment: Presented at the TSD 2014 conference: Text, Speech and Dialogue, 17th international conference. Brno, Czech Republic, September 8-12, 2014. 10 pages, 7 figure

Mg/Ti multilayers: structural, optical and hydrogen absorption properties

Mg-Ti alloys have uncommon optical and hydrogen absorbing properties, originating from a "spinodal-like" microstructure with a small degree of chemical short-range order in the atoms distribution. In the present study we artificially engineer short-range order by depositing Pd-capped Mg/Ti multilayers with different periodicities and characterize them both structurally and optically. Notwithstanding the large lattice parameter mismatch between Mg and Ti, the as-deposited metallic multilayers show good structural coherence. Upon exposure to H2 gas a two-step hydrogenation process occurs, with the Ti layers forming the hydride before Mg. From in-situ measurements of the bilayer thickness L at different hydrogen pressures, we observe large out-of-plane expansions of the Mg and Ti layers upon hydrogenation, indicating strong plastic deformations in the films and a consequent shortening of the coherence length. Upon unloading at room temperature in air, hydrogen atoms remain trapped in the Ti layers due to kinetic constraints. Such loading/unloading sequence can be explained in terms of the different thermodynamic properties of hydrogen in Mg and Ti, as shown by diffusion calculations on a model multilayered systems. Absorption isotherms measured by hydrogenography can be interpreted as a result of the elastic clamping arising from strongly bonded Mg/Pd and broken Mg/Ti interfaces

Vortex pinning by natural defects in thin films of YBa2Cu3O7−δ

Although vortex pinning in laser-ablated YBa2Cu3O7−δ films on (100) SrTiO3 is dominated by threading dislocations, many other natural pinning sites are present. To identify the contribution from twin planes, surface corrugations and point defects, we manipulate the relative densities of all defects by post-annealing films with various as-grown dislocation densities, ndisl. While a universal magnetic field B dependence of the transport current density js(B, T) is observed (independently of ndisl, temperature T and the annealing treatment), the defect structure changes considerably. Correlating the microstructure to js(B, T), it becomes clear that surface roughness, twins and point defects are not important at low magnetic fields compared to linear defect pinning. Transmission electron microscopy indicates that threading dislocations are not part of grain boundaries nor are they related to the twin domain structure. We conclude that js(B, T) is essentially determined by pinning along threading dislocations, naturally induced during the growth process. Even in high magnetic fields, where the vortex density outnumbers ndisl, it appears that linear defects stabilize the vortex lattice by means of the vortex–vortex interaction.

Ferrule-top nanoindenter: An optomechanical fiber sensor for nanoindentation

Ferrule-top probes are self-aligned all-optical devices obtained by fabricating a cantilever on the top of a ferruled optical fiber. This approach has been proven to provide a new platform for the realization of small footprint atomic force microscopes (AFMs) that adapt well to utilization outside specialized laboratories [D. Chavan, Rev. Sci. Instrum. 81, 123702 (2010)10.1063/1.3516044; D. Chavan, Rev. Sci. Instrum. 82, 046107 (2011)10.1063/1.3579496]. In this paper we now show that ferrule-top cantilevers can be also used to develop nanoindenters. Our instrument combines the sensitivity of commercial AFM-based indentation with the ease-of-use of more macroscopic instrumented indenters available today on the market. Furthermore, the all-optical design allows smooth operations also in liquids, where other devices are much more limited and often provide data that are difficult to interpret. This study may pave the way to the implementation of a new generation user-friendly nanoindenters for the measurement of the stiffness of samples in material sciences and medical research. © 2012 American Institute of Physics

The Properties of the Radio-Selected 1Jy Sample of BL Lacertae Objects

We present new optical and near-IR spectroscopy as well as new high dynamic range, arcsecond-resolution VLA radio maps of BL Lacs from the complete radio-selected "1 Jansky" (1Jy) sample (RBLs) for which such data were not previously available. Unlike BL Lacs from the complete X-ray-selected Einstein Medium Sensitivity Survey (EMSS) sample (XBLs), most RBLs possess weak but moderately luminous emission lines. And whereas nearly all XBLs have extended power levels consistent with FR-1s, more than half of the RBLs have extended radio power levels too luminous to be beamed FR-1 radio galaxies. In fact, we find evidence for and examples of three distinct mechanisms for creating the BL Lac phenomenon in the 1Jy sample: beamed FR-1s, beamed FR-2s and possibly a few gravitationally-lensed quasars. The v/v_max determined for the 1Jy sample is 0.614+/-0.047, which is markedly different from the negative evolution seen in the EMSS and other XBL samples. A correlation between logarithmic X-ray to radio flux ratio and v/v_max is observed across the EMSS and 1Jy samples, from negative evolution in the more extreme XBLs to positive evolution in the more extreme RBLs. There is evidence that the selection criteria chosen by Stickel et al. eliminates some BL Lac objects from the 1Jy sample, although how many is unknown. And several objects currently in the sample have exhibited strong emission lines in one or more epochs, suggesting they should be reclassified as FSRQs. However these selection effects cannot account for the observed discrepancy in XBL and RBL properties. From these observational properties we conclude that RBLs and XBLs cannot be related by viewing angle alone, and that RBLs are more closely related to FSRQs.Comment: 29 pages, 47 figures, accepted A

Effectiveness and cost-effectiveness of body psychotherapy in the treatment of negative symptoms of schizophrenia - a multi-centre randomised controlled trial

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