Strontium doping in mullite-type bismuth aluminate: A vacancy investigation using neutrons, photons and electrons

We report on strontium doped dibismuth-nonaoxoaluminate(III) produced at 1023 K. Partial substitution of bismuth by strontium in the structure yields oxygen vacancies for charge balance. Introducing oxygen vacancies rearranged the associated Al2O7 double-tetrahedra forming “Al3O10” tri-clusters which were identified by multi-quantum 27Al MAS NMR. Both STEM-EDX and XPS showed homogeneous distribution of strontium in the bulk and on the surface, respectively. Moreover, XPS confirms the valence state of bismuth after doping. The orientations of bismuth 6s2 lone electron pairs were calculated using DFT methods. The amount of strontium in the crystal structure was further confirmed from the decomposition product SrAl12O19 formed during the temperature-dependent X-ray powder diffraction. The structural proof was carried out by refining the structure of (Bi0.94Sr0.06)2Al4O8.94 from powder neutron and X-ray diffraction data. Rietveld refinements clearly showed the under occupation of one oxygen site and the shift of two aluminum atoms from the double-tetrahedra to two tri-cluster sites

Consequences of converting graded to action potentials upon neural information coding and energy efficiency

Information is encoded in neural circuits using both graded and action potentials, converting between them within single neurons and successive processing layers. This conversion is accompanied by information loss and a drop in energy efficiency. We investigate the biophysical causes of this loss of information and efficiency by comparing spiking neuron models, containing stochastic voltage-gated Na+ and K+ channels, with generator potential and graded potential models lacking voltage-gated Na+ channels. We identify three causes of information loss in the generator potential that are the by-product of action potential generation: (1) the voltage-gated Na+ channels necessary for action potential generation increase intrinsic noise and (2) introduce non-linearities, and (3) the finite duration of the action potential creates a ‘footprint’ in the generator potential that obscures incoming signals. These three processes reduce information rates by ~50% in generator potentials, to ~3 times that of spike trains. Both generator potentials and graded potentials consume almost an order of magnitude less energy per second than spike trains. Because of the lower information rates of generator potentials they are substantially less energy efficient than graded potentials. However, both are an order of magnitude more efficient than spike trains due to the higher energy costs and low information content of spikes, emphasizing that there is a two-fold cost of converting analogue to digital; information loss and cost inflation

A Taxonomy of Causality-Based Biological Properties

We formally characterize a set of causality-based properties of metabolic networks. This set of properties aims at making precise several notions on the production of metabolites, which are familiar in the biologists' terminology. From a theoretical point of view, biochemical reactions are abstractly represented as causal implications and the produced metabolites as causal consequences of the implication representing the corresponding reaction. The fact that a reactant is produced is represented by means of the chain of reactions that have made it exist. Such representation abstracts away from quantities, stoichiometric and thermodynamic parameters and constitutes the basis for the characterization of our properties. Moreover, we propose an effective method for verifying our properties based on an abstract model of system dynamics. This consists of a new abstract semantics for the system seen as a concurrent network and expressed using the Chemical Ground Form calculus. We illustrate an application of this framework to a portion of a real metabolic pathway

World Press Photo 2012: the discursive construction of the Arab Spring

O presente artigo pretende analisar a forma como o fenómeno da Primavera Árabe foi retratado nas fotografias vencedoras do concurso World Press Photo em 2012. As fotografias jornalísticas, embora se apresentem como índices do real, condicionam frequentemente a percepção dos indivíduos e influenciam as suas práticas sociais. Também as fotografias vencedoras do World Press Photo, um dos concursos mais prestigiados de fotojornalismo, em 2012 não fogem ao construtivismo discursivo que molda a representação e a percepção dos acontecimentos. A partir da análise crítica do discurso, nomeadamente dos instrumentos teóricos da semiótica barthesiana e da semiótica social de Gunther Kress e Theo van Leeuwen, procurámos interpretar as 38 fotografias vencedoras do World Press Photo 2012, a fim de reflectirmos sobre o modo como contribuíram para a compreensão da Revolta Árabe e como despertaram o nosso interesse e a nossa imaginação para o desenrolar do conflito.ABSTRACT:This article aims to analyze how the Arab Spring phenomenon was represented in the award-winning photographs of the World Press Photo contest in 2012. Although news photographs are usually seen as indexes of the real, they often limit the perception of individuals and influence their social practices. Also the winning photographs in 2012 of the World Press Photo, one of the most prestigious photojournalism contests, do not escape the discursive constructivism that shapes the representation and perception of events. Drawing from critical discourse analysis, namely from the theoretical tools of barthesian semiotics and Gunther Kress’s and Theo van Leeuwen’s social semiotics, we sought to interpret the 38 award-winning photographs of the World Press Photo contest in 2012, in order to reflect on the way they have contributed to our understanding of the Arab Revolt and aroused our interest and imagination to the unfolding of the conflict.info:eu-repo/semantics/publishedVersio

Tumour-derived PGD2 and NKp30-B7H6 engagement drives an immunosuppressive ILC2-MDSC axis.

Group 2 innate lymphoid cells (ILC2s) are involved in human diseases, such as allergy, atopic dermatitis and nasal polyposis, but their function in human cancer remains unclear. Here we show that, in acute promyelocytic leukaemia (APL), ILC2s are increased and hyper-activated through the interaction of CRTH2 and NKp30 with elevated tumour-derived PGD2 and B7H6, respectively. ILC2s, in turn, activate monocytic myeloid-derived suppressor cells (M-MDSCs) via IL-13 secretion. Upon treating APL with all-trans retinoic acid and achieving complete remission, the levels of PGD2, NKp30, ILC2s, IL-13 and M-MDSCs are restored. Similarly, disruption of this tumour immunosuppressive axis by specifically blocking PGD2, IL-13 and NKp30 partially restores ILC2 and M-MDSC levels and results in increased survival. Thus, using APL as a model, we uncover a tolerogenic pathway that may represent a relevant immunosuppressive, therapeutic targetable, mechanism operating in various human tumour types, as supported by our observations in prostate cancer.Group 2 innate lymphoid cells (ILC2s) modulate inflammatory and allergic responses, but their function in cancer immunity is still unclear. Here the authors show that, in acute promyelocytic leukaemia, tumour-activated ILC2s secrete IL-13 to induce myeloid-derived suppressor cells and support tumour growth

Removal of Misincorporated Ribonucleotides from Prokaryotic Genomes: An Unexpected Role for Nucleotide Excision Repair

Stringent steric exclusion mechanisms limit the misincorporation of ribonucleotides by high-fidelity DNA polymerases into genomic DNA. In contrast, low-fidelity Escherichia coli DNA polymerase V (pol V) has relatively poor sugar discrimination and frequently misincorporates ribonucleotides. Substitution of a steric gate tyrosine residue with alanine (umuC_Y11A) reduces sugar selectivity further and allows pol V to readily misincorporate ribonucleotides as easily as deoxynucleotides, whilst leaving its poor base-substitution fidelity essentially unchanged. However, the mutability of cells expressing the steric gate pol V mutant is very low due to efficient repair mechanisms that are triggered by the misincorporated rNMPs. Comparison of the mutation frequency between strains expressing wild-type and mutant pol V therefore allows us to identify pathways specifically directed at ribonucleotide excision repair (RER). We previously demonstrated that rNMPs incorporated by umuC_Y11A are efficiently removed from DNA in a repair pathway initiated by RNase HII. Using the same approach, we show here that mismatch repair and base excision repair play minimal back-up roles in RER in vivo. In contrast, in the absence of functional RNase HII, umuC_Y11A-dependent mutagenesis increases significantly in ΔuvrA, uvrB5 and ΔuvrC strains, suggesting that rNMPs misincorporated into DNA are actively repaired by nucleotide excision repair (NER) in vivo. Participation of NER in RER was confirmed by reconstituting ribonucleotide-dependent NER in vitro. We show that UvrABC nuclease-catalyzed incisions are readily made on DNA templates containing one, two, or five rNMPs and that the reactions are stimulated by the presence of mispaired bases. Similar to NER of DNA lesions, excision of rNMPs proceeds through dual incisions made at the 8th phosphodiester bond 5′ and 4th-5th phosphodiester bonds 3′ of the ribonucleotide. Ribonucleotides misinserted into DNA can therefore be added to the broad list of helix-distorting modifications that are substrates for NER

Non-hematopoietic cells contribute to protective tolerance to Aspergillus fumigatus via a TRIF pathway converging on IDO

Innate responses combine with adaptive immunity to generate the most effective form of anti-Aspergillus immune resistance. Whereas the pivotal role of dendritic cells in determining the balance between immunopathology and protective immunity to the fungus is well established, we determined that epithelial cells (ECs) also contributes to this balance. Mechanistically, EC-mediated protection occurred through a Toll-like receptor 3/Toll/IL-1 receptor domain-containing adaptor-inducing interferon (TLR3/TRIF)-dependent pathway converging on indoleamine 2,3-dioxygenase (IDO) via non-canonical nuclear factor-?B activation. Consistent with the high susceptibility of TRIF-deficient mice to pulmonary aspergillosis, bone marrow chimeric mice with TRIF unresponsive ECs exhibited higher fungal burdens and inflammatory pathology than control mice, underexpressed the IDO-dependent T helper 1/regulatory T cell (Th1/Treg) pathway and overexpressed the Th17 pathway with massive neutrophilic inflammation in the lungs. Further studies with interferon (IFN)-?, IDO or IL-17R unresponsive cells confirmed the dependency of immune tolerance to the fungus on the IFN-?/IDO/Treg pathway and of immune resistance on the MyD88 pathway controlling the fungal growth. Thus, distinct immune pathways contribute to resistance and tolerance to the fungus, to which the hematopoietic/non-hematopoietic compartments contribute through distinct, yet complementary, roles.We thank Cristina Massi Benedetti for digital art and editing. This work was supported by the Specific Targeted Research Project 'Sybaris' (LSHE-CT-2006), contract number 037899 (FP7) and by the Italian Projects PRIN 2007KLCKP8_004 (to LR) and 2007XYB9T9_001 (to SB). CC and AC were financially supported by fellowships from Fundacao para a Ciencia e Tecnologia, Portugal (contracts SFRH/BD/65962/2009 and SFRH/BPD/46292/2008, respectively)