Geometric matrix midranges

We define geometric matrix midranges for positive definite Hermitian matrices and study the midrange problem from a number of perspectives. Special attention is given to the midrange of two positive definite matrices before considering the extension of the problem to $N > 2$ matrices. We compare matrix midrange statistics with the scalar and vector midrange problem and note the special significance of the matrix problem from a computational standpoint. We also study various aspects of geometric matrix midrange statistics from the viewpoint of linear algebra, differential geometry and convex optimization.ECH2020 EUROPEAN RESEARCH COUNCIL (ERC) (670645

Drugs - a study in post-primary schools situated outside Dublin 1981.

The article reports on a survey of a random sample of pupils attending post-primary schools outside Dublin city and county. The survey of 5,408 students from 16 schools was conducted between September and December 1981. Information on the availability, use and knowledge of illicit drugs was gathered by means of self administered questionnaires. Some of the survey results were compared with those from a study of Irish rural post-primary school-children dating from 1970/71, and another carried out among Dublin post-primary school-children in 1981. A three- to eight-fold increase in the numbers of respondents who said they had taken a drug was found when the results were compared to the 1970/71 survey, and these students occurred with one-third to one-half the frequency to the Dublin 1980/81 survey. The authors suggested that their findings exposed the need to improve the drugs education available in schools

Near-field and confocal scanning spectroscopy/microscopy of porphyrin wheels

Contains fulltext : 10204.pdf (publisher's version ) (Open Access

Averaging Symmetric Positive-Definite Matrices

Symmetric positive definite (SPD) matrices have become fundamental computational objects in many areas, such as medical imaging, radar signal processing, and mechanics. For the purpose of denoising, resampling, clustering or classifying data, it is often of interest to average a collection of symmetric positive definite matrices. This paper reviews and proposes different averaging techniques for symmetric positive definite matrices that are based on Riemannian optimization concepts

Semi-metallic polymers

Polymers are lightweight, flexible, solution-processable materials that are promising for low-cost printed electronics as well as for mass-produced and large-area applications. Previous studies demonstrated that they can possess insulating, semiconducting or metallic properties; here we report that polymers can also be semi-metallic. Semi-metals, exemplified by bismuth, graphite and telluride alloys, have no energy bandgap and a very low density of states at the Fermi level. Furthermore, they typically have a higher Seebeck coefficient and lower thermal conductivities compared with metals, thus being suitable for thermoelectric applications. We measure the thermoelectric properties of various poly(3,4-ethylenedioxythiophene) samples, and observe a marked increase in the Seebeck coefficient when the electrical conductivity is enhanced through molecular organization. This initiates the transition from a Fermi glass to a semi-metal. The high Seebeck value, the metallic conductivity at room temperature and the absence of unpaired electron spins makes polymer semi-metals attractive for thermoelectrics and spintronics. © 2014 Macmillan Publishers Limited. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe