Influence of the interfacing with an electrically inhomogeneous bottom electrode on the ferroelectric properties of epitaxial PbTiO3

The influence of an electrically inhomogeneous epitaxial bottom layer on the ferroelectric and electrical properties has been explored in epitaxial PbTiO3 (PTO)/La0.7Sr0.3MnO3 (LSMO) submicron structures using atomic force microscopy. The submicron LSMO-dot structures underneath the ferroelectric PTO film allow exploring gradual changes in material properties. The LSMO interfacial layer influences significantly both electrical and ferroelectric properties of the upper PTO layer. The obtained results show that the as-grown polarization state of an epitaxial ferroelectric layer is strongly influenced by the properties of the layer on top of which it is deposited. (C) 2013 AIP Publishing LLC.

Evaluation of the diagnostic potential of a novel field immunomagnetic separation-immunochromatographic lateral flow assay to detect Mycobacterium bovis cells in European badger (Meles meles) faeces

The European badger (Meles meles) is a natural reservoir for Mycobacterium bovis, the causative agent of Bovine Tuberculosis, and has consequently been implicated in transmission of the disease to cattle. This study describes application of a novel M. bovis-specific immunochromatographic (lateral flow) assay in combination with immunomagnetic separation (IMS-LFD), to test badger faeces samples. In total, 441 faeces samples from badgers of unknown disease status collected from latrines at 110 badger setts throughout Northern Ireland (NI) and 100 faeces samples from badgers of known infection status from Great Britain (GB) were tested. Faeces (approx. 1g) was homogenised in 9 ml phosphate buffered saline, filtered (70 µm), and then 6-8 ml subjected to the IMS-LFD test. Residual clarified faecal homogenates were subjected to automated IMS followed by MGIT™ liquid culture (AIMS-MGIT™ culture) and qPCR (AIMS-qPCR). Evidence for the presence of M. bovis was obtained for 78 (18%), 61 (14%) and 140 (32%) of 441 NI badger faeces samples, and 10 (10%), 41 (41%) and 56 (56%) of 100 GB badger faeces samples, by IMS-LFD, AIMS-MGIT culture and AIMS-qPCR tests, respectively. The IMS-LFD test was less sensitive than AIMS-qPCR for detection of M. bovis and was, therefore, detecting badgers shedding high numbers of M. bovis in their faeces only. However, these ‘super shedders’ may be primarily responsible for the spread of Bovine Tuberculosis so are, therefore, an important target. This non-invasive test could form the basis of a field surveillance tool to indicate infected badger groups which are actively spreading M. bovis.

A LEED STRUCTURAL STUDY OF THE CO INDUCED RECONSTRUCTION OF PD(110) - EVIDENCE FOR A MISSING ROW STRUCTURE

Molecularly adsorbed CO on Pd{110} has been shown (R. Raval et al., Chem. Phys. Lett. 167 (1990) 391, ref. [1]) to induce a substantial reconstruction of the surface in the coverage range 0.3 <theta less-than-or-equal-to 0.75. Throughout this coverage range, the adsorbate-covered reconstructed surface exhibits a (4 x 2) LEED pattern. However, the exact nature of the reconstruction remains uncertain. We have conducted a LEED I(E) "fingerprinting" analysis of the CO/Pd{110}-(4 x 2) structure in order to establish the type of reconstruction induced in the metal surface. This study shows that the LEED I(E) profiles of the integral order and appropriate half-order beams of the CO/Pd{110}-(4 x 2) pattern closely resemble the I(E) profiles theoretically calculated for a Pd{110}-(1 x 2) missing-row structure. Additionally, there is a strong resemblance to the experimental LEED I(E) profiles for the Cs/Pd{110}-(1 x 2) structure which has also been shown to exhibit the missing-row structure. On the basis of this evidence we conclude that the CO/Pd{110}-(4 x 2) LEED pattern arises from a missing-row reconstruction of the Pd{110} surface which gives rise to a strong underlying (1 x 2) pattern plus a poorly ordered CO overlayer which produces weak, diffuse fourth-order spots in the LEED pattern.

Electrooxidation of the iodides [C(4)mim]I, LiI, NaI, KI, RbI, and CsI in the room temperature ionic liquid [C(4)mim][NTf2]

The electrochemical oxidation of 1-butyl-3-methylimidazolium iodide, [C(4)mim]I, has been investigated by cyclic voltammetry at a platinum microelectrode at varying concentrations in the RTIL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C(4)mim][NTf2]. Two oxidation peaks were observed. The first peak is assigned to the oxidation of iodide to triiodide, in an overall two-electron process: 3I(-)- 2e(-) -> I-3(-). At higher potentials, the electrogenerated triiodide oxidizes to iodine, in an overall one-electron process: I-3(-) - e(-) -> 3/2I(2). An average diffusion coefficient, D, for I- of 1.55 x 10(-11) m(2) s(-1) was obtained. A digital simulation program was used to simulate the voltammetric response, and kinetic parameters were successfully extracted. The parameters deduced from the simulation include D for I-, I-3(-), and I-2 and K-eq,K-2, the equilibrium constant for the reaction of iodide and iodine to form triiodide. Values for these parameters are of the same order as those previously published for the oxidation of Br- in the same RTIL [Allen et al. J. Electroanal. Chem. 2005, 575, 311]. Next, the cyclic voltammetry of five different inorganic iodide salts was studied by dissolving small amounts of the solid in [C(4)mim][NTf2]. Similar oxidation peaks were observed, revealing diffusion coefficients of ca. 0.55, 1.14, 1.23, 1.44, and 1.33 x 10(-11) m(2) s(-1) and solubilities of 714, 246, 54, 83, and 36 mM for LiI, NaI, KI, RbI, and CsI, respectively. The slightly smaller diffusion coefficients for the XI salts (compared to [C(4)mim]I) may indicate that I- is ion-paired with Li+, Na+, K+, Rb+, and Cs+ in the RTIL medium.

Half-precessional dynamics of monsoon rainfall near the East African Equator

External climate forcings-such as long-term changes in solar insolation-generate different climate responses in tropical and high latitude regions(1). Documenting the spatial and temporal variability of past climates is therefore critical for understanding how such forcings are translated into regional climate variability. In contrast to the data-richmiddle and high latitudes, high-quality climate-proxy records from equatorial regions are relatively few(2-4), especially from regions experiencing the bimodal seasonal rainfall distribution associated with twice-annual passage of the Intertropical Convergence Zone. Here we present a continuous and well-resolved climate-proxy record of hydrological variability during the past 25,000 years from equatorial East Africa. Our results, based on complementary evidence from seismic-reflection stratigraphy and organic biomarker molecules in the sediment record of Lake Challa near Mount Kilimanjaro, reveal that monsoon rainfall in this region varied at half-precessional (similar to 11,500-year) intervals in phase with orbitally controlled insolation forcing. The southeasterly and northeasterly monsoons that advect moisture from the western Indian Ocean were strengthened in alternation when the inter-hemispheric insolation gradient was at a maximum; dry conditions prevailed when neither monsoon was intensified and modest local March or September insolation weakened the rain season that followed. On sub-millennial timescales, the temporal pattern of hydrological change on the East African Equator bears clear high-northern-latitude signatures, but on the orbital timescale it mainly responded to low-latitude insolation forcing. Predominance of low-latitude climate processes in this monsoon region can be attributed to the low-latitude position of its continental regions of surface air flow convergence, and its relative isolation from the Atlantic Ocean, where prominent meridional overturning circulation more tightly couples low-latitude climate regimes to high-latitude boundary conditions.

Towards groundwater security in coastal East Africa: initiating a regional research network and integrated hydrogeologic, climatic & socio-economic observatories in coastal aquifers of the Comoros Islands, Kenya and Tanzania

African coastal regions are expected to experience the highest rates of population growth in coming decades. Fresh groundwater resources in the coastal zone of East Africa (EA) are highly vulnerable to seawater intrusion. Increasing water demand is leading to unsustainable and ill-planned well drilling and abstraction. Wells supplying domestic, industrial and agricultural needs are or have become, in many areas, too saline for use. Climate change, including weather changes and sea level rise, is expected to exacerbate this problem. The multiplicity of physical, demographic and socio-economic driving factors makes this a very challenging issue for management. At present the state and probable evolution of coastal aquifers in EA are not well documented. The UPGro project 'Towards groundwater security in coastal East Africa' brings together teams from Kenya, Tanzania, Comoros Islands and Europe to address this knowledge gap. An integrative multidisciplinary approach, combining the expertise of hydrogeologists, hydrologists and social scientists, is investigating selected sites along the coastal zone in each country. Hydrogeologic observatories have been established in different geologic and climatic settings representative of the coastal EA region, where focussed research will identify the current status of groundwater and identify future threats based on projected demographic and climate change scenarios. Researchers are also engaging with end users as well as local community and stakeholder groups in each area in order to understanding the issues most affecting the communities and searching sustainable strategies for addressing these.

The large- and small-scale Ca IIK structure of the Milky Way from observations of Galactic and Magellanic sightlines

Aims. The large and small-scale (pc) structure of the Galactic interstellar medium can be investigated by utilising spectra of early-type stellar probes of known distances in the same region of the sky. This paper determines the variation in line strength of Ca ii at 3933.661 Å as a function of probe separation for a large sample of stars, including a number of sightlines in the Magellanic Clouds. 

Methods. FLAMES-GIRAFFE data taken with the Very Large Telescope towards early-type stars in 3 Galactic and 4 Magellanic open clusters in Ca ii are used to obtain the velocity, equivalent width, column density, and line width of interstellar Galactic calcium for a total of 657 stars, of which 443 are Magellanic Cloud sightlines. In each cluster there are between 43 and 111 stars observed. Additionally, FEROS and UVES Ca ii K and Na i D spectra of 21 Galactic and 154 Magellanic early-type stars are presented and combined with data from the literature to study the calcium column density - parallax relationship. 

Results. For the four Magellanic clusters studied with FLAMES, the strength of the Galactic interstellar Ca ii K equivalent width on transverse scales from ∼0.05-9 pc is found to vary by factors of ∼1.8-3.0, corresponding to column density variations of ∼0.3-0.5 dex in the optically-thin approximation. Using FLAMES, FEROS, and UVES archive spectra, the minimum and maximum reduced equivalent widths for Milky Way gas are found to lie in the range ∼35-125 mÅ and ∼30-160 mÅ for Ca ii K and Na i D, respectively. The range is consistent with a previously published simple model of the interstellar medium consisting of spherical cloudlets of filling factor ∼0.3, although other geometries are not ruled out. Finally, the derived functional form for parallax (π) and Ca ii column density (N_CaII) is found to be π(mas) = 1 / (2.39 × 10^-13 × N_CaII (cm^-2) + 0.11). Our derived parallax is ∼25 per cent lower than predicted by Megier et al. (2009, A&A, 507, 833) at a distance of ∼100 pc and ∼15 percent lower at a distance of ∼200 pc, reflecting inhomogeneity in the Ca ii distribution in the different sightlines studied.