Magnetic quasicrystals: What can we expect to see in their neutron diffraction data?

The theory of magnetic symmetry in quasicrystals is used to characterize the nature of magnetic peaks, expected in elastic neutron diffraction experiments. It is established that there is no symmetry-based argument which forbids the existence of quasiperiodic long-range magnetic order. Suggestions are offered as to where one should look for the simplest kinds of antiferromagnetic quasicrystals.Comment: 4 pages. Submitted to Materials Science and Engineering

(Re)construccion de una identidad negra en Venezuela

Depuis quelques années, on peut observer au Venezuela un renouveau des pratiques culturelles liées à l’identité noire. Ce processus a été complexe et s’inscrit dans l’affirmation d’une nouvelle société civile indépendante du système des parties et des structures traditionnelles de pouvoir. Les organisations noires ont investi de nombreux domaines de la vie sociale : défense de l’environnement, économie, santé, éducation, culture. La mise en évidence de la relation entre lutte ethnico-culturelle et revendication sociale a été au cœur de son action. Des exemples choisis dans des communautés rurales et urbaines illustreront cette nouvelle réalité.Desde hace unis años se puede observar una nueva affirmación de la cultura y de la identidad afro-venezolana se trata del resultado de un proceso complejo. Su característica más revelante fue su emergencia dentro de la “nueva sociedad civil” distanciada de los partidos politicos y de los poderes tradicionales. El movimiento negro venezuelano se ha impuestio como interlocutor en varios campos de la vida pùblica defensa del medio : ambiente, economia, salud, educación, cultura. Frecuentemente su acción se ha caracterizado por la voluntad de ligar lo étnico y lo social como se podrá demostrar con ejemplos escogidos en varias comunidades urbanas y rurales

Justin DANIEL (dir.), Les îles caraïbes modèles politiques et stratégies de développement

Cet ouvrage est né d’une collaboration entre chercheurs de la Caraïbe, d’Europe et des Etats-Unis ayant 1’ambition avouée de diffuser largement des travaux souvent épars sur une région rarement considérée dans sa globalité. Les contributions présentées dessinent la Caraïbe insulaire dans la diversitéde ses statuts politiques (Etats dépendants et territoires liés à une métropole), de ses régimes politiques (démocraties consolidées ou en voie de consolidation) et de ses cultures (sociétés anglo..

Justin DANIEL (dir.), Les îles caraïbes modèles politiques et stratégies de développement

Cet ouvrage est né d’une collaboration entre chercheurs de la Caraïbe, d’Europe et des Etats-Unis ayant 1’ambition avouée de diffuser largement des travaux souvent épars sur une région rarement considérée dans sa globalité. Les contributions présentées dessinent la Caraïbe insulaire dans la diversitéde ses statuts politiques (Etats dépendants et territoires liés à une métropole), de ses régimes politiques (démocraties consolidées ou en voie de consolidation) et de ses cultures (sociétés anglo..

The nature of the silicaphilic fluorescence of PDMPO

PDMPO (2-(4-pyridyl)-5-((4-(2-dimethylaminoethylaminocarbamoyl)methoxy)phenyl)oxazole), has unique silica specific fluorescence and is used in biology to understand biosilicification. This ‘silicaphilic’ fluorescence is not well understood nor is the response to local environmental variables like solvent and pH. We investigated PDMPO in a range of environments: using UV-vis and fluorescence spectroscopy supported by computational data, (SPARC, molecular dynamics simulations, density functional theory calculations), dynamic light scattering and zeta potential measurements to understand the PDMPO–silica interaction. From absorption data, PDMPO exhibited a pKa of 4.20 for PDMPOH22+ to PDMPOH+ . Fluorescence emission measurements revealed large shifts in excited state pKa* values with different behaviour when bound to silica (pKa* of 10.4). PDMPO bound to silica particles is located in the Stern layer with the dye exhibiting pH dependent depolarising motion. In aqueous solution, PDMPO showed strong chromaticity with correlation between the maximum emission wavelength for PDMPOH+* and dielectric constant (4.8–80). Additional chromatic effects were attributed to changes in solvent accessible surface area. Chromatic effects were also observed for silica bound dye which allow its use as a direct probe of bulk pH over a range far in excess of what is possible for the dye alone (3–5.2). The unique combination of chromaticity and excited state dynamics allows PDMPO to monitor pH from 3 to 13 while also reporting on surface environment opening a new frontier in the quantitative understanding of (bio)silicification

The checkpoint Saccharomyces cerevisiae Rad9 protein contains a tandem tudor domain that recognizes DNA.

International audienceDNA damage checkpoints are signal transduction pathways that are activated after genotoxic insults to protect genomic integrity. At the site of DNA damage, 'mediator' proteins are in charge of recruiting 'signal transducers' to molecules 'sensing' the damage. Budding yeast Rad9, fission yeast Crb2 and metazoan 53BP1 are presented as mediators involved in the activation of checkpoint kinases. Here we show that, despite low sequence conservation, Rad9 exhibits a tandem tudor domain structurally close to those found in human/mouse 53BP1 and fission yeast Crb2. Moreover, this region is important for the resistance of Saccharomyces cerevisiae to different genotoxic stresses. It does not mediate direct binding to a histone H3 peptide dimethylated on K79, nor to a histone H4 peptide dimethylated on lysine 20, as was demonstrated for 53BP1. However, the tandem tudor region of Rad9 directly interacts with single-stranded DNA and double-stranded DNAs of various lengths and sequences through a positively charged region absent from 53BP1 and Crb2 but present in several yeast Rad9 homologs. Our results argue that the tandem tudor domains of Rad9, Crb2 and 53BP1 mediate chromatin binding next to double-strand breaks. However, their modes of chromatin recognition are different, suggesting that the corresponding interactions are differently regulated

A rapid and robust diagnostic for liver fibrosis using a multichannel polymer sensor array

Liver disease is the fifth most common cause of premature death in the Western world, with the irreversible damage caused by fibrosis, and ultimately cirrhosis, a primary driver of mortality. Early detection of fibrosis would facilitate treatment of the underlying liver disease to limit progression. Unfortunately, most cases of liver disease are diagnosed late, with current strategies reliant on invasive biopsy or fragile lab-based antibody technologies. A robust, fully synthetic fluorescent-polymer sensor array is reported, which, rapidly (in 45 minutes), detects liver fibrosis from low-volume serum samples with clinically relevant specificity and accuracy, using an easily read- able diagnostic output. The simplicity, rapidity, and robustness of this method make it a promising platform for point-of-care diagnostics for detecting and monitoring liver disease

The rotation-coupled sliding of EcoRV

It has been proposed that certain type II restriction enzymes (REs), such as EcoRV, track the helical pitch of DNA as they diffuse along DNA, a so-called rotation-coupled sliding. As of yet, there is no direct experimental observation of this phenomenon, but mounting indirect evidence gained from single-molecule imaging of RE–DNA complexes support the hypothesis. We address this issue by conjugating fluorescent labels of varying size (organic dyes, proteins and quantum dots) to EcoRV, and by fusing it to the engineered Rop protein scRM6. Single-molecule imaging of these modified EcoRVs sliding along DNA provides us with their linear diffusion constant (D1), revealing a significant size dependency. To account for the dependence of D1 on the size of the EcoRV label, we have developed four theoretical models describing different types of motion along DNA and find that our experimental results are best described by rotation-coupled sliding of the protein. The similarity of EcoRV to other type II REs and DNA binding proteins suggests that this type of motion could be widely preserved in other biological contexts

A Miocene tectonic inversion in the Ionian Sea (Central Mediterranean): evidence from multi-channel seismic data

It is widely accepted that the Central and Eastern Mediterranean are remnants of the Neo-Tethys. However, the orientation and timing of spreading of this domain remain controversial. Here, we present time migrated and pre-stack depth migrated NW-SE oriented Archimede (1997) lines together with the PrisMed01 (1993) profile to constrain the evolution of the Ionian basin. Our interpretation allows us to identify a large-scale set of SW-NE striking reverse faults beneath the Ionian Abyssal Plain. These primarily NW vergent faults are characterized by a spacing comprised between 10 to 20 km and a dip ranging from 60 to 65{degree sign}. Following very recent paleogeographic reconstructions, we propose that the set of N{degree sign}55 features initially formed as normal faults during the NW-SE trending seafloor spreading of the Ionian basin after its late Triassic-early Jurassic rifting. Based on geometric comparisons with the intraplate deformation observed beneath the Central Indian Ocean, we show that the inherited oceanic normal faults were reactivated under compression as reverse faults. Well-developed Tortonian syntectonic basins developed NW of the major faults and the base of the Messinian evaporites (Mobile Unit) is slightly folded by the activity of the faults. We show that 3-4 km of total shortening occurs over a 80 km wide area beneath the Ionian Abyssal Plain, resulting in a bulk shortening of 3.5-5 %. We propose a link between the Tortonian-early Messinian inversion of the fault pattern and a plate tectonic reorganization prior to the main phase of back-arc opening of the Tyrrhenian domain