Linearized force constants method for lattice dynamics in mixed semiconductors

A simple and accurate method of calculating phonon spectra in mixed semiconductors alloys, on the basis of preliminarily (from first principles) relaxed atomic structure, is proposed and tested for (Zn,Be)Se and (Ga,In)As solid solutions. The method uses an observation that the interatomic force constants, calculated ab initio for a number of microscopic configurations in the systems cited, show a clear linear variation of the main (diagonal) values of the interatomic force constants with the corresponding bond length. We formulate simple rules about how to recover the individual 3x3 subblocks of the force constants matrix in their local (bonds-related) coordinate systems and how to transform them into a global (crystal cell-related) coordinate system. Test calculations done for 64-atom supercells representing different concentrations of (Zn,Be)Se and (Ga,In)As show that the phonon frequencies and compositions of eigenvectors are faithfully reproduced in a linearized force constants calculation, as compared to true ab initio calculations.Comment: to appear in the proceedings of the Phonons2007 conference (Paris, July 2007

Lattice dynamics of mixed semiconductors (Be,Zn)Se from first-principles calculations

Vibration properties of Zn(1-x)Be(x)Se, a mixed II-VI semiconductor haracterized by a high contrast in elastic properties of its pure constituents, ZnSe and BeSe, are simulated by first-principles calculations of electronic structure, lattice relaxation and frozen phonons. The calculations within the local density approximation has been done with the Siesta method, using norm-conserving pseudopotentials and localized basis functions; the benchmark calculations for pure endsystems were moreover done also by all-electron WIEN2k code. An immediate motivation for the study was to analyze, at the microscopic level, the appearance of anomalous phonon modes early detected in Raman spectra in the intermediate region (20 to 80%) of ZnBe concentration. This was early discussed on the basis of a percolation phenomenon, i.e., the result of the formation of wall-to-wall --Be--Se-- chains throughout the crystal. The presence of such chains was explicitly allowed in our simulation and indeed brought about a softening and splitting off of particular modes, in accordance with experimental observation, due to a relative elongation of Be--Se bonds along the chain as compared to those involving isolated Be atoms. The variation of force constants with interatomic distances shows common trends in relative independence on the short-range order.Comment: 11 pages, 10 figures, to be published in Phys. Rev.

Aportación al conocimiento de las tricolomatáceas de Cataluña

Sobre la base de 555 recolecciones procedentes de 190 localidades de Catalufia, se da cuenta de 88 especies de Tricolomataceas (excluyendo Melanoleuca y Mycena) reconocidas. De ellas, las 11 siguientes constituyen nueva cita para la flora catalana: Armillariella cepestipes Vel., Armillariella obscura (Secr.) Romagn., Calocybe ionides (Bull, ex Fr.) Donk., Laccaria montana Sing., Lyophyllum fumatofoetens (Secr.) Schff., Marasmius tremulae Vel., Oudemansiella badia (Quél.) Moser, Resupinatus unguicularis (Fr.) Sing., Strobilurus stephanocystis (Hora) Sing., Strobilurus tenacellus (Pers. ex Fr.) Sing., Tricholoma flavobrunneum (Fr. ex Fr.) Kummer.Contribution to the study of the Tricholomataceae of Catalonia. Based on 555 collections from 190 localities of Catalonia (NE Spain), a list is given of 88 species of Tricholomataceae (excuding Melanoleuca and Mycena) collected, with first hand chorological and ecological data. Some of them (11) are new records for Catalonia: Armillariella cepestipes Vel., Armillariella obscura (Secr.) Romagn., Calocybe ionides (Bull, ex Fr.) Donk., Laccaria montana Sing., Lyophyllum fumatofoetens (Secr.) Schff., Marasmius tremulae Vel., Oudemansiella badia (Quél.) Moser, Resupinatus unguicularis (Fr.) Sing., Strobilurus stephanocystis (Hora) Sing., Strobilurus tenacellus (Pers. ex Fr.) Sing., Tricholoma flavobrunneum (Fr. ex Fr.) Kummer

Aportación al conocimiento de las tricolomatáceas de Cataluña

Contribution to the study of the Tricholomataceae of Catalonia. Based on 555 collections from 190 localities of Catalonia (NE Spain), a list is given of 88 species of Tricholomataceae (excuding Melanoleuca and Mycena) collected, with first hand chorological and ecological data. Some of them (11) are new records for Catalonia: Armillariella cepestipes Vel., Armillariella obscura (Secr.) Romagn., Calocybe ionides (Bull, ex Fr.) Donk., Laccaria montana Sing., Lyophyllum fumatofoetens (Secr.) Schff., Marasmius tremulae Vel., Oudemansiella badia (Quél.) Moser, Resupinatus unguicularis (Fr.) Sing., Strobilurus stephanocystis (Hora) Sing., Strobilurus tenacellus (Pers. ex Fr.) Sing., Tricholoma flavobrunneum (Fr. ex Fr.) Kummer.Sobre la base de 555 recolecciones procedentes de 190 localidades de Catalufia, se da cuenta de 88 especies de Tricolomataceas (excluyendo Melanoleuca y Mycena) reconocidas. De ellas, las 11 siguientes constituyen nueva cita para la flora catalana: Armillariella cepestipes Vel., Armillariella obscura (Secr.) Romagn., Calocybe ionides (Bull, ex Fr.) Donk., Laccaria montana Sing., Lyophyllum fumatofoetens (Secr.) Schff., Marasmius tremulae Vel., Oudemansiella badia (Quél.) Moser, Resupinatus unguicularis (Fr.) Sing., Strobilurus stephanocystis (Hora) Sing., Strobilurus tenacellus (Pers. ex Fr.) Sing., Tricholoma flavobrunneum (Fr. ex Fr.) Kummer

Raman spectroscopy, a non-destructive solution to the study of glass and its alteration

This paper presents the potential of Raman spectroscopy, a non-destructive technique which can be applied in-situ, for the analyses of glass and their alteration. Recent analytical developments are summarised for different glass composition and practical examples are given. The paper describes how to extract compositional information from the glass, first based on the spectra profile to distinguish rapidly alkali silicate from alkaline-earth alkali silicate and lead alkali silicate glass, then using the spectral decomposition and correlations to extract quantitative data. For alkali silicate glasses, that are most prone to alteration, the spectral characteristics are described to interpret the alteration process (selective leaching or dissolution of the glass) from the Raman spectra of the altered glass. These developments have greatly widened the potential of the technique and supplement well its ability to measure the thickness of the altered layer and identify the crystalline deposits

Noves dades sobre els gasteromicets de Catalunya

Revisió del material de gasteromicets contingut a l'h erbari dels autors, que compren especialment les recol·leccions procedents del projecte "Bi odiversitat Micológica de Catalunya" (1994-2005). Una part important del material procedeix de comunitats mediterr ánies arbustives, especialment d'estepars (Cistion). D'un total de 47 espec ies identificades, al costat de táxons abundants i de descornposici ó lenta, de gran persistencia i abundancia, com Astraeus hygro111etricus, Bovista aestivalis, Calvatia excipuliformis, Scleroderma po /yrhizum, etc., hi ha diverses espec ies poc citades a Catalunya: Battarrea steve nii, Bovista ochrotricha, Disciseda bovista, Gastrop ila fragilis, Geastrum campestre, G. quadrifidum, Gyrophragmium dunalii, Hydnangium carneum, Hystera ngium c/athroides var. cistophilum, Lycoperdon ericaeum i Setchelliogaster tenuipes.The Gasteromycctcs preserved in the author' s herbarium, which is especially rich in collection s made during the "Biodiversitat Micol ógica de Catalunya" proje ct (1994-2005), are revised. An import ant part of the material comes from the study of Mediterranean bush comrnunities, especially rockro se bushes (Cistion). The total number of species identified is 47, and includ e, along with taxa of high presence and slow breakdown rate, such as Astraeus hygrometricus, Bovista aestivalis, Calvatia excipu/iformis, Scleroderma polyrhizum, etc., a numb er of taxa rarely quoted in the area or others which are chorologically relevant, such as Battarrea stevenii, Bovista ochrotricha, Disciseda bovista, Gastrop i/a fragilis, Geastrum campestre, G. quadrifidum , Gyrophragmium dunalii, Hydnangium carneum, Hystera ngium clathroides var. cistophilum, Lycoperdon ericaeum and Setchelliogaster tenuipes

Mitochondrial and ribosomal biogenesis are new hallmarks of stemness, oncometabolism and biomass accumulation in cancer : mito-stemness and ribo-stemness features

Using proteomics analysis, we previously compared MCF7 breast cancer cells grown as 3D tumor spheres, with the same cell line grown as monolayers. Our results indicated that during 3D anchorage‐independent growth, the cellular machinery associated with i) mitochondrial biogenesis and ii) ribosomal biogenesis, were both significantly increased. Here, for simplicity, we refer to these two new oncogenic hallmarks as “mito‐stemness” and “ribo‐stemness” features. We have now applied this same type of strategy to begin to understand how fibroblasts and MCF7 breast cancer cells change their molecular phenotype, when they are co‐cultured together. We have previously shown that MCF7‐fibroblast co‐cultures are a valuable model of resistance to apoptosis induced by hormonal therapies, such as Tamoxifen and Fulvestrant. Here, we directly show that these mixed co‐cultures demonstrate the induction of mito‐stemness and ribo‐stemness features, likely reflecting a mechanism for cancer cells to increase their capacity for accumulating biomass. In accordance with the onset of a stem‐like phenotype, KRT19 (keratin 19) was induced by ~6‐fold during co‐culture. KRT19 is a well‐established epithelial CSC marker that is used clinically to identify metastatic breast cancer cells in sentinel lymph node biopsies. The potential molecular therapeutic targets that we identified by label‐free proteomics of MCF7‐fibroblast co‐cultures were then independently validated using a bioinformatics approach. More specifically, we employed publically‐available transcriptional profiling data derived from primary tumor samples from breast cancer patients, which were previously subjected to laser‐capture micro‐dissection, to physically separate breast cancer cells from adjacent tumor stroma. This allowed us to directly validate that the proteins up‐regulated in this co‐culture model were also transcriptionally elevated in patient‐derived breast cancer cells in vivo. This powerful approach for target identification and translational validation, including the use of patient outcome data, can now be applied to other tumor types as well, to validate new therapeutic targets that are more clinically relevant, for patient benefit. Moreover, we discuss the therapeutic implications of these findings for new drug development, drug repurposing and Tamoxifen‐resistance, to effectively target mito‐stemness and ribo‐stemness features in breast cancer patients. We also discuss the broad implications of this “organelle biogenesis” approach to cancer therapy

Mitochondrial fission as a driver of stemness in tumor cells : mDIVI1 inhibits mitochondrial function, cell migration and cancer stem cell (CSC) signalling

Mitochondria are dynamic organelles frequently undergoing fission and fusion events to maintain their integrity, bioenergetics and spatial distribution, which is fundamental to the processes of cell survival. Disruption in mitochondrial dynamics plays a role in cancer. Therefore, proteins involved in regulating mitochondrial dynamics are potential targets for treatment. mDIVI1 is an inhibitor of the mitochondrial fission protein DRP1, which induces i) mitochondrial oxidative stress and ii) effectively reduces mitochondrial metabolism. We show here that mDIVI1 is able to inhibit 3D tumorsphere forming capacity, cell migration and stemness-related signalling in breast cancer cells, indicating that mDIVI1 can potentially be used for the therapeutic elimination of cancer stem cells (CSCs)