33 research outputs found
On the effective shear speed in 2D phononic crystals
The quasistatic limit of the antiplane shear-wave speed ('effective speed')
in 2D periodic lattices is studied. Two new closed-form estimates of
are derived by employing two different analytical approaches. The first
proceeds from a standard background of the plane wave expansion (PWE). The
second is a new approach, which resides in -space and centers on
the monodromy matrix (MM) introduced in the 2D case as the multiplicative
integral, taken in one coordinate, of a matrix with components being the
operators with respect to the other coordinate. On the numerical side, an
efficient PWE-based scheme for computing is proposed and implemented. The
analytical and numerical findings are applied to several examples of 2D square
lattices with two and three high-contrast components, for which the new PWE and
MM estimates are compared with the numerical data and with some known
approximations. It is demonstrated that the PWE estimate is most efficient in
the case of densely packed stiff inclusions, especially when they form a
symmetric lattice, while in general it is the MM estimate that provides the
best overall fitting accuracy.Comment: 13 pages, 9 figure
A review of elliptical and disc galaxy structure, and modern scaling laws
A century ago, in 1911 and 1913, Plummer and then Reynolds introduced their
models to describe the radial distribution of stars in `nebulae'. This article
reviews the progress since then, providing both an historical perspective and a
contemporary review of the stellar structure of bulges, discs and elliptical
galaxies. The quantification of galaxy nuclei, such as central mass deficits
and excess nuclear light, plus the structure of dark matter halos and cD galaxy
envelopes, are discussed. Issues pertaining to spiral galaxies including dust,
bulge-to-disc ratios, bulgeless galaxies, bars and the identification of
pseudobulges are also reviewed. An array of modern scaling relations involving
sizes, luminosities, surface brightnesses and stellar concentrations are
presented, many of which are shown to be curved. These 'redshift zero'
relations not only quantify the behavior and nature of galaxies in the Universe
today, but are the modern benchmark for evolutionary studies of galaxies,
whether based on observations, N-body-simulations or semi-analytical modelling.
For example, it is shown that some of the recently discovered compact
elliptical galaxies at 1.5 < z < 2.5 may be the bulges of modern disc galaxies.Comment: Condensed version (due to Contract) of an invited review article to
appear in "Planets, Stars and Stellar
Systems"(www.springer.com/astronomy/book/978-90-481-8818-5). 500+ references
incl. many somewhat forgotten, pioneer papers. Original submission to
Springer: 07-June-201
Molecular classification of selective oestrogen receptor modulators on the basis of gene expression profiles of breast cancer cells expressing oestrogen receptor α
The purpose of this study was to classify selective oestrogen receptor modulators based on gene expression profiles produced in breast cancer cells expressing either wtERα or mutant351ERα. In total, 54 microarray experiments were carried out by using a commercially available Atlas cDNA Expression Arrays (Clontech), containing 588 cancer-related genes. Nine sets of data were generated for each cell line following 24âh of treatment: expression data were obtained for cells treated with vehicle EtOH (Control); with 10â9 or 10â8âM oestradiol; with 10â6âM 4-hydroxytamoxifen; with 10â6âM raloxifene; with 10â6âM idoxifene, with 10â6âM EM 652, with 10â6âM GW 7604; with 5Ă10â5âM resveratrol and with 10â6âM ICI 182,780. We developed a new algorithm âExpression Signaturesâ to classify compounds on the basis of differential gene expression profiles. We created dendrograms for each cell line, in which branches represent relationships between compounds. Additionally, clustering analysis was performed using different subsets of genes to assess the robustness of the analysis. In general, only small differences between gene expression profiles treated with compounds were observed with correlation coefficients ranged from 0.83 to 0.98. This observation may be explained by the use of the same cell context for treatments with compounds that essentially belong to the same class of drugs with oestrogen receptors related mechanisms. The most surprising observation was that ICI 182,780 clustered together with oestrodiol and raloxifene for cells expressing wtERα and clustered together with EM 652 for cells expressing mutant351ERα. These data provide a rationale for a more precise and elaborate study in which custom made oligonucleotide arrays can be used with comprehensive sets of genes known to have consensus and putative oestrogen response elements in their promoter regions