Hafnium silicate: a new microwave dielectric ceramic with low thermal expansivity.

A HfSiO4 ceramic was prepared by a conventional solid state synthesis method by sintering at 1600 °C. The morphology of the sintered surface was characterized using scanning electron microscopy and atomic force microscopy and the average surface roughness was about 118 nm. The sintered HfSiO4 ceramic has εr = 7.0, Qu × f = 25 000 and τf = -44 ppm °C(-1) at 10 GHz. It exhibits promising thermal properties such as a low linear thermal expansivity (CTE) of -1.8 ppm °C(-1) (dilatometer) in the temperature range of 30-800 °C and a room temperature thermal conductivity of 11 W m(-1) K(-1).

Poly(vinylidene fluoride)-La(0.5)Sr(0.5)CoO(3-δ) composites: the influence of LSCO particle size on the structure and dielectric properties.

Dielectric composites composed of poly(vinylidene fluoride) (PVDF) and La0.5Sr0.5CoO3-δ (LSCO) with high permittivity, low loss and high breakdown strength have been developed. The effects of particle size of LSCO (fine (∼250 nm) and coarse (∼3 µm)) on the phase crystallization of PVDF and dielectric properties of polymer-LSCO composites are studied. The inclusion of fine LSCO into PVDF readily favours the formation of polar crystals (ß and γ-phases), which makes the composite suitable for both electromechanical and high charge storage embedded capacitor applications. Moreover, the addition of fine LSCO particles also increases the overall crystallization rate as well as the melting point of PVDF. The composite containing fine LSCO particles gave a percolation threshold at about 25 volume percentage, while that with coarse particles did not show any percolation even at very high volume percentage. As a result of fine LSCO particle loading, the composite exhibited a relative permittivity (εr) of ∼600, a conductivity of 2.7 × 10(-7) S cm(-1), a dielectric loss (tan δ) of 0.7 at 1 kHz and a breakdown voltage of 100 V even at 20 volume percentage of a filler, demonstrating promising applications in the embedded capacitors.

Neurocognitive disorder detection based on feature vectors extracted from VBM analysis of structural MRI.

Dementia is a growing concern due to the aging process of the western societies. Non-invasive detection is therefore a high priority research endeavor. In this paper we report results of classification systems applied to the feature vectors obtained by a feature extraction method computed on structural magnetic resonance imaging (sMRI) volumes for the detection of two neurological disorders with cognitive impairment: myotonic dystrophy of type 1 (MD1) and Alzheimer disease (AD). The feature extraction process is based on the voxel clusters detected by voxel-based morphometry (VBM) analysis of sMRI upon a set of patient and control subjects. This feature extraction process is specific for each kind of disease and is grounded on the findings obtained by medical experts. The 10-fold cross-validation results of several statistical and neural network based classification algorithms trained and tested on these features show high specificity and moderate sensitivity of the classifiers, suggesting that the approach is better suited for rejecting than for detecting early stages of the diseases.

Functional ceramic materials database: an online resource for materials research.

We present work on the creation of a ceramic materials database which contains data gleaned from literature data sets as well as new data obtained from combinatorial experiments on the London University Search Instrument. At the time of this writing, the database contains data related to two main groups of materials, mainly in the perovskite family. Permittivity measurements of electroceramic materials are the first area of interest, while ion diffusion measurements of oxygen ion conductors are the second. The nature of the database design does not restrict the type of measurements which can be stored; as the available data increase, the database may become a generic, publicly available ceramic materials resource.

Highly tunable photonic crystal filter for the terahertz range.

By use of an incipient ferroelectric, SrTiO3, as a defect material inserted into a periodic structure of alternating layers of quartz and high-permittivity ceramic, thermal tuning of a single defect mode over the entire lowest forbidden band was obtained. The tunability of this compact structure reached 60%.