Structural, dielectric, and conduction behaviour of A-site deficient SrxNa1−2xNbO3 ceramics

The crystallographic and electrical properties of A-site deficient SrxNa1−2xNbO3 (x = 0.00, 0.05, 0.10, 0.15, 0.20, and 0.25) perovskites have been studied by X-ray diffraction, scanning electron microscopy, dielectric spectroscopy, impedance spectroscopy and polarisation against electric field loops. Despite complexities in the microstructural evolution due to the formation of a NaNb3O8 liquid phase, the crystallographic and dielectric properties show much clearer trends. The introduction of A-site vacancies shows an almost linear expansion of the pseudo-cubic unit cell volume of ∼0.05 Å3 per at%, stabilising the ferroelectric P21ma Q-phase. Compositions x > 0.10 show increasingly relaxor-like behaviour in the dielectric properties and impedance spectroscopy shows increasing conductivity and tan δ values associated with predominantly electronic conduction from x = 0.05 to 0.25. Measurements in N2 at 600 °C show progressively n-type behaviour with increasing levels of A-site vacancies due to the increased tendency to lose under-bonded O2− ions and therefore partially reduce some Nb5+ to Nb4+ ions. Although it is not possible to fully establish the electrical properties of our undoped NaNbO3 ceramics, we propose they contain mixed ionic–electronic behaviour with the clear presence of a weak n-type dependent grain boundary contribution to the total conductivity

Alternative explanation for the relaxor ferroelectric behavior in FeTiNbO6 rutile ceramics: The influence of electrode contacts

The radio-frequency permittivity-temperature profiles of acceptor-donor codoped TiO2-based rutiles commonly produce higher than expected values (>103 at 300 K) often with conflicting interpretations. A combination of dielectric spectroscopy (DS) and impedance spectroscopy (IS) with different electrode materials is used to reinvestigate the electrical properties of Fe3+-Nb5+-doped rutile in the form of FeTiNbO6 ceramics that show permittivity-temperature characteristics that are consistent with relaxor ferroelectrics (RFE). IS results reveal semiconducting grains with an activation energy of ∼0.16eV, and relative permittivity of similar magnitude and temperature dependence to undoped TiO2(<250). Reducing the work function of the electrode material by replacing Au with InGa has a dramatic effect on the IS and DS data. We propose the apparent RFE behavior observed by DS and previously attributed to the formation of nanoclustering of the cations is an extrinsic effect primarily associated with the development of Schottky barriers between the semiconducting ceramics and Au contacts

The Self Model and the Conception of Biological Identity in Immunology

The self/non-self model, first proposed by F.M. Burnet, has dominated immunology for sixty years now. According to this model, any foreign element will trigger an immune reaction in an organism, whereas endogenous elements will not, in normal circumstances, induce an immune reaction. In this paper we show that the self/non-self model is no longer an appropriate explanation of experimental data in immunology, and that this inadequacy may be rooted in an excessively strong metaphysical conception of biological identity. We suggest that another hypothesis, one based on the notion of continuity, gives a better account of immune phenomena. Finally, we underscore the mapping between this metaphysical deflation from self to continuity in immunology and the philosophical debate between substantialism and empiricism about identity

Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt(s)=1.96 TeV using Lepton + Jets Events with Lifetime b-tagging

We present a measurement of the top quark pair ($t\bar{t}$) production cross section ($\sigma_{t\bar{t}}$) in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV using 230 pb$^{-1}$ of data collected by the D0 experiment at the Fermilab Tevatron Collider. We select events with one charged lepton (electron or muon), missing transverse energy, and jets in the final state. We employ lifetime-based b-jet identification techniques to further enhance the $t\bar{t}$ purity of the selected sample. For a top quark mass of 175 GeV, we measure $\sigma_{t\bar{t}}=8.6^{+1.6}_{-1.5}(stat.+syst.)\pm 0.6(lumi.)$ pb, in agreement with the standard model expectation.Comment: 7 pages, 2 figures, 3 tables Submitted to Phys.Rev.Let

Pasteurella multocida infections: Report of 34 cases and review of the literature

Pasteurella multocida, a small gram-negative coccobacillus, is part of the normal oral flora of many animals, including the cat and dog. P. multocida is a major pathogen in wound infections due to animal bites and can cause cellutitis, abscess, osteomyelitis, septic arthritis, or a variety of other infectious syndromes (Table 1). Over the years, P. multocida has been the subject of a number of short general reviews (74, 80, 91, 96, 158). More recently, reviews have focused on selected aspects of P. multocida infection including meningitis (44), empyema (112), spontaneous bacterial peritonitis (160), bone and joint infections (56), and septicemia (111). A large series of cases with a comprehensive review, however, has not been published. We therefore report here 34 cases from the Massachusetts General Hospital and review the English literature

Structural and dielectric properties of CaSnO3-doped Sr2.1Na0.8Nb5O15 ceramics

The crystallographic, microstructural, and dielectric properties of Sr2.1Na0.8-xCaxNb5-xSnxO15 (x = 0.00, 0.01, 0.05, 0.10) polycrystalline ceramics have been studied by X-ray diffraction, scanning electron microscopy, dielectric spectroscopy (DS) and impedance spectroscopy (IS). For x = 0.00, 0.05, and 0.10, samples are single phase with P4bm symmetry at room temperature with x = 0.01 showing a small quantity of secondary phase(s). All compositions show typical ceramic microstructures and d50 grain sizes ranging from 5.1 to 26.6 μm. DS shows a clear trend in the high temperature ferroelectric-paraelectric transition with the Curie temperature, T0, decreasing from ∼ 160 to ∼ 110 °C, and an additional relaxation at approximately 120 °C with increasing CaSnO3. IS reveals all samples have a homogeneous electrical microstructure with predominantly electronic conduction. The activation energy of conduction calculated from Arrhenius plots of the conductivity increases with CaSnO3 content from 1.27 to 1.38 eV likely due to the expansion of the band gap

Size Doesn't Matter: Towards a More Inclusive Philosophy of Biology

notes: As the primary author, O’Malley drafted the paper, and gathered and analysed data (scientific papers and talks). Conceptual analysis was conducted by both authors.publication-status: Publishedtypes: ArticlePhilosophers of biology, along with everyone else, generally perceive life to fall into two broad categories, the microbes and macrobes, and then pay most of their attention to the latter. ‘Macrobe’ is the word we propose for larger life forms, and we use it as part of an argument for microbial equality. We suggest that taking more notice of microbes – the dominant life form on the planet, both now and throughout evolutionary history – will transform some of the philosophy of biology’s standard ideas on ontology, evolution, taxonomy and biodiversity. We set out a number of recent developments in microbiology – including biofilm formation, chemotaxis, quorum sensing and gene transfer – that highlight microbial capacities for cooperation and communication and break down conventional thinking that microbes are solely or primarily single-celled organisms. These insights also bring new perspectives to the levels of selection debate, as well as to discussions of the evolution and nature of multicellularity, and to neo-Darwinian understandings of evolutionary mechanisms. We show how these revisions lead to further complications for microbial classification and the philosophies of systematics and biodiversity. Incorporating microbial insights into the philosophy of biology will challenge many of its assumptions, but also give greater scope and depth to its investigations

Update on biomarkers in neuromyelitis optica

Neuromyelitis optica (NMO) (and NMO spectrum disorder) is an autoimmune inflammatory disease of the CNS primarily affecting spinal cord and optic nerves. Reliable and sensitive biomarkers for onset, relapse, and progression in NMO are urgently needed because of the heterogeneous clinical presentation, severity of neurologic disability following relapses, and variability of therapeutic response. Detecting aquaporin-4 (AQP4) antibodies (AQP4-IgG or NMO-IgG) in serum supports the diagnosis of seropositive NMO. However, whether AQP4-IgG levels correlate with disease activity, severity, response to therapy, or long-term outcomes is unclear. Moreover, biomarkers for patients with seronegative NMO have yet to be defined and validated. Collaborative international studies hold great promise for establishing and validating biomarkers that are useful in therapeutic trials and clinical management. In this review, we discuss known and potential biomarkers for NMO

ASASSN-15lu is a Type Ia Supernova

We report spectroscopic classification of ASASSN-15lu (ATel #7698) in SDSS J132112.88+401556.7 (z=0.035037, via NED) through inspection of an optical spectrum (range 370-680 nm, resolution 0.8 nm), obtained with the 2.3-m Bok telescope (+ Boller & Chivens spectrograph) at Kitt Peak on 2015 June 24.2 UT