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Texture-engineered ceramics enable access to a vast array of novel texture-property relations leading to property values ranging between those of single crystals and isotropic bulk ceramics. Recently developed templated grain growth and magnetic alignment texturing methods yield high quality crystallographic texture, and thus significant advances in achievable texture-engineered properties in magnetic, piezoelectric, electronic, optical, thermoelectric, and structural ceramics. In this paper, we outline the fundamental basis for these texture-engineered properties and review recent contributions to the field of texture-engineered ceramics with an update on the properties of textured lead-free and lead-based piezoelectrics. We propose that further property improvements can be realized through development of processes that improve crystallographic alignment of the grain structure, create biaxial texture, and explore a wider array of crystallographic orientations. There is a critical need to model the physics of texture-engineered ceramics, and more comprehensively characterize texture, thus enabling testing of texture orientation-property relations and materials performance. We believe that in situ measurements of texture evolution can lead to a more fundamental and comprehensive understanding of the mechanisms of texture development.
In most developed countries, children in lone parent families face a high risk of poverty. A partial solution commonly sought in English-speaking nations is to increase the amounts of private child maintenance paid by the other parent. However, where lone parent families are in receipt of social assistance benefits, some countries hold back a portion of the child maintenance to reduce public expenditures. This partial ‘pass-through’ treats child maintenance as a substitute for cash benefits which conceivably neutralises its poverty reduction potential. Such neutralising effects are not well understood and can be obscured further when more subtle interactions between child maintenance systems and social security systems operate. This research makes a unique contribution to knowledge by exposing the hidden interaction effects operating in similar child maintenance systems across four countries: the United Kingdom, United States (Wisconsin), Australia and New Zealand. We found that when child maintenance is counted as income in calculating benefit entitlements, it can reduce the value of cash benefits. Using model lone parent families with ten different employment and income scenarios, we show how the poverty reduction potential of child maintenance is affected by whether it is treated as a substitute for, or a complement to, cash benefits.
We obtained near–infrared spectra of a sample of very low mass objects as a function of age in order to investigate the temperature and surface gravity sensitivity of several features in the J– and K–bands.
We present an analysis of low-resolution infrared spectra for 25 brown dwarf candidates in the NGC 1333 molecular cloud. Candidates were chosen on the basis of their association with the high column density cloud core, and near-infrared fluxes and colors. We compare the depths of water vapor absorption bands in our candidate objects with a grid of dwarf, subgiant, and giant standards to determine spectral types which are independent of reddening. These data are used to derive effective temperatures and bolometric luminosities which, when combined with theoretical tracks and isochrones for pre-main sequence objects, enable us to estimate masses and ages. Depending on the models considered, a total of 9 to 20 brown dwarfs are identified with a median of age of <1 Myr.
We quantify the scientific potential for exoplanet imaging with the mid-infrared E-ELT Imager and Spectrograph (METIS) foreseen as one of the instruments of the European Extremely Large Telescope (E-ELT). We focus on two main science cases: (1) the direct detection of known gas giant planets found by radial velocity (RV) searches; and (2) the direct detection of small (1–4 R⊕) planets around the nearest stars. Under the assumptions made in our modelling, in particular on the achievable inner working angle and sensitivity, our analyses reveal that within a reasonable amount of observing time METIS is able to image >20 already known, RV-detected planets in at least one filter. Many more suitable planets with dynamically determined masses are expected to be found in the coming years with the continuation of RV-surveys and the results from the GAIA astrometry mission. In addition, by extrapolating the statistics for close-in planets found by Kepler, we expect METIS might detect ≈10 small planets with equilibrium temperatures between 200 and 500 K around the nearest stars. This means that (1) METIS will help constrain atmospheric models for gas giant planets by determining for a sizable sample their luminosity, temperature and orbital inclination; and (2) METIS might be the first instrument to image a nearby (super-) Earth-sized planet with an equilibrium temperature near that expected to enable liquid water on a planet surface.
Guidelines for treating various conditions can be helpful in setting practice standards, but the presence of several sets of guidelines from different countries, experts, and settings, written at different times, can also create confusion. Here we provide a “guideline of guidelines” for the treatment of schizophrenia, or “meta-guidelines,” which not only reconcile the various existing standards but also update them to include the use of several newer agents, most of which were marketed following the publication of existing standards.
More than 50% of the global population already lives in urban settlements and urban areas are projected to absorb almost all the global population growth to 2050, amounting to some additional three billion people. Over the next decades the increase in rural population in many developing countries will be overshadowed by population flows to cities. Rural populations globally are expected to peak at a level of 3.5 billion people by around 2020 and decline thereafter, albeit with heterogeneous regional trends. This adds urgency in addressing rural energy access, but our common future will be predominantly urban. Most of urban growth will continue to occur in small-to medium-sized urban centers. Growth in these smaller cities poses serious policy challenges, especially in the developing world. In small cities, data and information to guide policy are largely absent, local resources to tackle development challenges are limited, and governance and institutional capacities are weak, requiring serious efforts in capacity building, novel applications of remote sensing, information, and decision support techniques, and new institutional partnerships. While ‘megacities’ with more than 10 million inhabitants have distinctive challenges, their contribution to global urban growth will remain comparatively small.
Energy-wise, the world is already predominantly urban. This assessment estimates that between 60–80% of final energy use globally is urban, with a central estimate of 75%. Applying national energy (or GHG inventory) reporting formats to the urban scale and to urban administrative boundaries is often referred to as a ‘production’ accounting approach and underlies the above GEA estimate.
Natural and synthetic hydroxyapatite (HA) scaffolds for potential
load-bearing bone implants were fabricated by two methods. The natural
scaffolds were formed by heating bovine cancellous bone at 1325°C, which
removed the organic and sintered the HA. The synthetic scaffolds were
prepared by freeze-casting HA powders, using different solid loadings (20–35
vol.%) and cooling rates (1–10°C/min). Both types of scaffolds were
infiltrated with polymethylmethacrylate (PMMA). The porosity, pore size, and
compressive mechanical properties of the natural and synthetic scaffolds
were investigated and compared to that of natural cortical and cancellous
bone. Prior to infiltration, the sintered cancellous scaffolds exhibited
pore sizes of 100 – 300 μm, a strength of 0.4 – 9.7 MPa, and a Young’s
modulus of 0.1 – 1.2 GPa. The freeze-casted scaffolds had pore sizes of 10 –
50 μm, strengths of 0.7 – 95.1 MPa, and Young’s moduli of 0.1 –19.2 GPa.
When infiltrated with PMMA, the cancellous bone- PMMA composite showed a
strength of 55 MPa and a Young’s modulus of 4.5 GPa. Preliminary data for
the synthetic HA-PMMA composite showed a strength of 42 MPa and a modulus of
The behaviour of 300 keV Ba ions implanted at room temperature with doses between 1015 and 1017 cm−2 in Mg single crystal and foils was investigated. The results show that the Ba ions do not occupy substitutions sites in Mg, either after the implantation or the annealing treatments. However, pronounced migration of Ba to the surface is observed above 380 °C. The remaining fraction overlaps with the aa-implanted distribution and forms small precipitates. This behaviour is not correlated with the recovery of the Mg lattice which is already complete at about 250 °C. The surface segregation of Ba delays the evaporation of Mg to temperatures near the melting point.
In this study, the causes of biaxial and hydrostatic stress components in epitaxially grown thin GaN films on sapphire are analyzed. It is observed that growth by Molecular Beam Epitaxy (MBE) and by Metal Organic Chemical Vapor Deposition (MOCVD) are governed by very similar physical principles. Differences in the absolute stress values are mainly due to the difference in growth temperature. It is argued that in the case of MOCVD growth the onset of plasticity for higher growth temperatures is responsible for a larger stress relaxation in the buffer layer. It is further found that either process can result in highly off-stoichiometric GaN layers, as manifested by the large variations in the a and c lattice parameters caused by intrinsic point defects.
We report on results of low-temperature photoluminescence measurements performed on GaN films, grown by molecular beam epitaxy (MBE) on sapphire substrates. The GaN films are either Mg doped (p-type) or consist of a Mg-doped layer on top of a Si doped GaN layer (n-type). In the p-doped samples, the sharpness of the donor-acceptor-pair transition is striking, three phonon replicas are clearly resolved. A transition band occurs around 3.4 eV, which becomes dominant for samples with an np-layer structure. The position and the composition of the near band edge transitions are influenced by the growth of the buffer layers. Depending on the growth conditions a transition at 3.51 eV can be observed.