Crystal structure and proton conductivity of BaSn0.6Sc0.4O3-delta: insights from neutron powder diffraction and solid-state NMR spectroscopy

The solid-state synthesis and structural characterisation of perovskite BaSn(1–x)Sc(x)O(3–δ) (x = 0.0, 0.1, 0.2, 0.3, 0.4) and its corresponding hydrated ceramics are reported. Powder and neutron X-ray diffractions reveal the presence of cubic perovskites (space group Pm3m) with an increasing cell parameter as a function of scandium concentration along with some indication of phase segregation. (119)Sn and (45)Sc solid-state NMR spectroscopy data highlight the existence of oxygen vacancies in the dry materials, and their filling upon hydrothermal treatment with D(2)O. It also indicates that the Sn(4+) and Sc(3+) local distribution at the B-site of the perovskite is inhomogeneous and suggests that the oxygen vacancies are located in the scandium dopant coordination shell at low concentrations (x ≤ 0.2) and in the tin coordination shell at high concentrations (x ≥ 0.3). (17)O NMR spectra on (17)O enriched BaSn(1–x)Sc(x)O(3–δ) materials show the existence of Sn–O–Sn, Sn–O–Sc and Sc–O–Sc bridging oxygen environments. A further room temperature neutron powder diffraction study on deuterated BaSn(0.6)Sc(0.4)O(3–δ) refines the deuteron position at the 24k crystallographic site (x, y, 0) with x = 0.579(3) and y = 0.217(3) which leads to an O–D bond distance of 0.96(1) Å and suggests tilting of the proton towards the next nearest oxygen. Proton conduction was found to dominate in wet argon below 700 °C with total conductivity values in the range 1.8 × 10(–4) to 1.1 × 10(–3) S cm(–1) between 300 and 600 °C. Electron holes govern the conduction process in dry oxidizing conditions, whilst in wet oxygen they compete with protonic defects leading to a wide mixed conduction region in the 200 to 600 °C temperature region, and a suppression of the conductivity at higher temperature

Functional Memory B Cells and Long-Lived Plasma Cells Are Generated after a Single Plasmodium chabaudi Infection in Mice

Antibodies have long been shown to play a critical role in naturally acquired immunity to malaria, but it has been suggested that Plasmodium-specific antibodies in humans may not be long lived. The cellular mechanisms underlying B cell and antibody responses are difficult to study in human infections; therefore, we have investigated the kinetics, duration and characteristics of the Plasmodium-specific memory B cell response in an infection of P. chabaudi in mice. Memory B cells and plasma cells specific for the C-terminal region of Merozoite Surface Protein 1 were detectable for more than eight months following primary infection. Furthermore, a classical memory response comprised predominantly of the T-cell dependent isotypes IgG2c, IgG2b and IgG1 was elicited upon rechallenge with the homologous parasite, confirming the generation of functional memory B cells. Using cyclophosphamide treatment to discriminate between long-lived and short-lived plasma cells, we demonstrated long-lived cells secreting Plasmodium-specific IgG in both bone marrow and in spleens of infected mice. The presence of these long-lived cells was independent of the presence of chronic infection, as removal of parasites with anti-malarial drugs had no impact on their numbers. Thus, in this model of malaria, both functional Plasmodium-specific memory B cells and long-lived plasma cells can be generated, suggesting that defects in generating these cell populations may not be the reason for generating short-lived antibody responses

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Proton conduction in oxygen deficient Ba3In1.4Y0.3M0.3ZrO8 (M = Ga3+ or Gd3+) perovskites

B-site disordered, oxygen deficient Ba3In1.4Y0.3M0.3ZrO8 (M = Gd3+ or Ga3+) perovskites of space group Pm (3) over barm, were prepared by a solid-state reactive sintering method. Thermogravimetric analysis of the as-prepared samples revealed 79.3% and 55.5% protonation of the available oxygen vacancies by OH groups in the Gd-3: and Ga-3: containing samples, respectively. Conductivity was found to be in the range of 0.3-1.1 x 10 (3) S cm (1) (M = Gd3+) and 1.1-4.6 x 10 (4) S cm (1) (M = Ga3+) for the temperature interval 300-600 degrees C in wet Argon. Ba3In1.4Y0.3Ga0.3ZrO8 shows an approximate one order of magnitude increase in conductivity at T > 600 degrees C under dry oxygen indicating a significant p-type contribution whereas Ba3In1.4Y0.3Gd0.3ZrO8 reveals a smaller enhancement. Ba3In1.4Y0.3Ga0.3ZrO8 displays considerable mixed proton-electronic conduction in the interval 400-800 degrees C under wet oxidising conditions suggesting possibility of Ga-containing compositions as a cathode materials in a proton conducting fuel cell

Proton Conductivity in Mixed B-Site Doped Perovskite Oxide BaZr[sub 0.5]In[sub 0.25]Yb[sub 0.25]O[sub 3 - delta]

A wet chemical route was used to prepare the oxygen deficient codoped perovskite oxide BaZr0.5In0.25Yb0.25O3−. Analysis of X-ray powder diffraction data showed that the sample belongs to the cubic crystal system with space group Pmm. Dynamic thermogravimetric (TG) analysis confirmed complete filling of oxygen vacancies (V) by protonic defects (OH) during the hydration process. The proton conductivity was investigated by impedance spectroscopy. The bulk and total conductivities of prehydrated BaZr0.5In0.25Yb0.25O3− were found to be 8.5×10−4 and 2.2×10−5 S cm−1, respectively, at 300°C. The total conductivity in the codoped perovskite oxide was higher compared to that of the respective single doped perovskite oxides with the same doping level. The bulk and grain-boundary mobility and diffusion coefficients of protons were calculated at 200°C using impedance and TG data to obtain the conductivity and proton concentration, respectively. The high bulk diffusivity (2.3×10−7 cm2 s−1) was obtained which indicates that the protons are more free to move in the heavily doped matrix compared to the lightly doped systems where trapping of protons occurs

Pyrochlore to Fluorite Transition: The Y₂(Ti_1–<i>x</i>Zr_<i>x</i>)₂O₇ (0.0 ≤ <i>x</i> ≤ 1.0) System

The structural properties of the system Y₂(Ti_1–<i>x</i>Zr_<i>x</i>)₂O₇ have been investigated using the neutron powder diffraction technique, including a detailed analysis of the “total scattering” using reverse Monte Carlo modeling to probe the short-range ion–ion correlations over sample range 0.0 ≤ <i>x</i> ≤ 1.0. The average crystal structure shows a continuous transformation from the long-range ordered pyrochlore structure (<i>Fd</i>3̅<i>m</i>, <i>a</i> = 10.0967(1) Å, <i>Z</i> = 8, for <i>x</i> = 0.00, Y₂Ti₂O₇) to a disordered fluorite structure (<i>Fm</i>3̅<i>m</i>, <i>a</i> = 5.2042(1) Å, <i>Z</i> = 1, for <i>x</i> = 1.00, Zr₂Y₂O₇) in agreement with previous reports. However, on increasing <i>x</i> the disordering of both the cation and the anion sublattices occurs in stages, with the Zr⁴⁺ initially only substituting onto the Ti⁴⁺ site and adopting a cubic, rather than octahedral, local anion environment. At concentrations in excess of <i>x</i> ≈ 0.4 there is a gradual disordering of the Y³⁺, Ti⁴⁺, and Zr⁴⁺ species over all the cation sites, coupled with a redistribution of the O^2– which initially only involves those anions on the O1 sites. The relationship between the composition dependences of the structure properties and the ionic conductivity is discussed

Pyrochlore to Fluorite Transition: The Y₂(Ti_1–<i>x</i>Zr_<i>x</i>)₂O₇ (0.0 ≤ <i>x</i> ≤ 1.0) System

The structural properties of the system Y₂(Ti_1–<i>x</i>Zr_<i>x</i>)₂O₇ have been investigated using the neutron powder diffraction technique, including a detailed analysis of the “total scattering” using reverse Monte Carlo modeling to probe the short-range ion–ion correlations over sample range 0.0 ≤ <i>x</i> ≤ 1.0. The average crystal structure shows a continuous transformation from the long-range ordered pyrochlore structure (<i>Fd</i>3̅<i>m</i>, <i>a</i> = 10.0967(1) Å, <i>Z</i> = 8, for <i>x</i> = 0.00, Y₂Ti₂O₇) to a disordered fluorite structure (<i>Fm</i>3̅<i>m</i>, <i>a</i> = 5.2042(1) Å, <i>Z</i> = 1, for <i>x</i> = 1.00, Zr₂Y₂O₇) in agreement with previous reports. However, on increasing <i>x</i> the disordering of both the cation and the anion sublattices occurs in stages, with the Zr⁴⁺ initially only substituting onto the Ti⁴⁺ site and adopting a cubic, rather than octahedral, local anion environment. At concentrations in excess of <i>x</i> ≈ 0.4 there is a gradual disordering of the Y³⁺, Ti⁴⁺, and Zr⁴⁺ species over all the cation sites, coupled with a redistribution of the O^2– which initially only involves those anions on the O1 sites. The relationship between the composition dependences of the structure properties and the ionic conductivity is discussed

Kilifi Health and Demographic Surveillance Data (Abridged Version) 2000 - 2019

The Kilifi Health and Demographic Surveillance System (KHDSS), located on the Indian Ocean coast of Kenya, was established in 2000 as a record of births, pregnancies, migration events, deaths and causes of deaths and is maintained by 4-monthly household visits. The study area was selected to capture the majority of patients admitted to Kilifi District Hospital, now Kilifi County Hospital. The KHDSS has 284,000 residents and covers 891 km2 and the hospital admits 4,400 paediatric patients and 3,400 adult patients per year. At the hospital, morbidity events are linked in real time by a computer search of the KHDSS population register. Linked surveillance was extended to KHDSS vaccine clinics in 2008. KHDSS data have been used to define the incidence of hospital presentation with childhood infectious diseases (e.g. rotavirus diarrhoea, pneumococcal disease), to test the association between genetic risk factors (e.g. thalassaemia and sickle cell disease) and infectious diseases, to define the community prevalence of chronic diseases (e.g. epilepsy), to evaluate access to health care and to calculate the operational effectiveness of major public health interventions (e.g. conjugate Haemophilus influenzae type b vaccine). Rapport with residents is maintained through an active programme of community engagement. A system of collaborative engagement exists for sharing data on survival, morbidity, socio-economic status and vaccine coverage.</p