Modelling the structure of Zr-rich Pb(Zr1-xTix)O-3, x=0.4 by a multiphase approach

Solid solution perovskite Pb(Zr1−xTix)O3 (PZT) is an industrially important material. Despite the long history of experimental and theoretical studies, the structure of this material is still under intensive discussion. In this work, we have applied structure searching coupled with density functional theory methods to provide a multiphase description of this material at x = 0.4. We demonstrate that the permutational freedom of B-site cations leads to the stabilisation of a variety of local phases reflecting a relatively flat energy landscape of PZT. Using a set of predicted local phases we reproduce the experimental pair distribution function (PDF) profile with high accuracy. We introduce a complex multiphase picture of the structure of PZT and show that additional monoclinic and rhombohedral phases account for a better description of the experimental PDF profile. We propose that such a multiphase picture reflects the entropy reached in the sample during the preparation process

Long-term (trophic) purinergic signalling: purinoceptors control cell proliferation, differentiation and death

The purinergic signalling system, which uses purines and pyrimidines as chemical transmitters, and purinoceptors as effectors, is deeply rooted in evolution and development and is a pivotal factor in cell communication. The ATP and its derivatives function as a 'danger signal' in the most primitive forms of life. Purinoceptors are extraordinarily widely distributed in all cell types and tissues and they are involved in the regulation of an even more extraordinary number of biological processes. In addition to fast purinergic signalling in neurotransmission, neuromodulation and secretion, there is long-term (trophic) purinergic signalling involving cell proliferation, differentiation, motility and death in the development and regeneration of most systems of the body. In this article, we focus on the latter in the immune/defence system, in stratified epithelia in visceral organs and skin, embryological development, bone formation and resorption, as well as in cancer. Cell Death and Disease (2010) 1, e9; doi:10.1038/cddis.2009.11; published online 14 January 201

Emergent Phenomena Induced by Spin-Orbit Coupling at Surfaces and Interfaces

Spin-orbit coupling (SOC) describes the relativistic interaction between the spin and momentum degrees of freedom of electrons, and is central to the rich phenomena observed in condensed matter systems. In recent years, new phases of matter have emerged from the interplay between SOC and low dimensionality, such as chiral spin textures and spin-polarized surface and interface states. These low-dimensional SOC-based realizations are typically robust and can be exploited at room temperature. Here we discuss SOC as a means of producing such fundamentally new physical phenomena in thin films and heterostructures. We put into context the technological promise of these material classes for developing spin-based device applications at room temperature

The apicomplexan plastid and its evolution

Protistan species belonging to the phylum Apicomplexa have a non-photosynthetic secondary plastid—the apicoplast. Although its tiny genome and even the entire nuclear genome has been sequenced for several organisms bearing the organelle, the reason for its existence remains largely obscure. Some of the functions of the apicoplast, including housekeeping ones, are significantly different from those of other plastids, possibly due to the organelle’s unique symbiotic origin

The role of VHE muons in an explanation of unusual events observed in cosmic rays

Unusual events observed in cosmic-ray experiments that cannot be explained in the context of modern theories and models are considered. The peculiarities of VHE (>= 100 TeV) muon interactions and their possible contribution to the production of various unusual events in cosmic rays are analyzed. Some preliminary results obtained in relation to unusual events detected in the Tien Shan calorimeter and in the Pamir experiment are discussed

Novel gene HCS1 is specifically expressed in the giant interneurones of the terrestrial snail

THE terrestrial snail Helix lucorum is a promising model for molecular neurobiology since its central nervous system (CNS) is simple and contains many morphologically and functionally identified large neurones. Among these, the giant interneurones located in pleural and parietal ganglia are especially interesting because they trigger the withdrawal behaviour of the snail and participate in aversive conditioning. Here we describe the identification and characterization of a gene named HCS1 which is preferentially expressed in these interneurones. It encodes a putative protein 100 amino acids long containing an N-terminal hydrophobic leader peptide. No sequences with significant homology to HCS1 were found in the protein (Swiss-Prot) and nucleotide (EMBLbank) data libraries. We suppose that the product of this gene is a secreted protein, presumably a neuropeptide or a growth factor

Identification of two novel genes specifically expressed in the D-group neurons of the terrestrial snail CNS

A search for genes specifically expressed in the giant interneurons of parietal ganglia of the snail Helix lucorum yielded, among others, two genes named HDS1 and HDS2. According to data obtained by Northern hybridization and whole-mount in situ hybridization, both genes are neurospecific and expressed almost exclusively in the peptidergic D-group neurons (Sakharov, 1974) located in the right parietal ganglion. In situ hybridization of the HDS1 and HDS2 probes with CNS of several related species of the Helicoidea superfamily identified in all cases similarly located homologous groups of neurons. Sequencing of the near full-length cDNA copies of the HDS1 and HDS2 genes revealed open reading frames 107 and 102 amino acids long for HDS1 and HDS2, respectively. Both putative proteins contain a hydrophobic leader peptide and putative recognition sites for furin-like and PC-like endopeptidases. Predicted amino acid sequences of the HDS1 and HDS2 proteins were found to be moderately homologous to each other, as well as to the LYCP preprohormone expressed by the light yellow cells of the freshwater snail Lymnaea stagnalis. These results confirm an earlier hypothesis that the D-group of the Helix family and the light yellow cells of Lymnaea stagnalis represent homologous neuronal groups. Our data suggest that the HDS1 and HDS2 genes encode precursors of secreted molecules, most likely neuropeptides or neurohormones