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Adult schistosomes live in the blood vessels and cannot easily be sampled from humans, so archived miracidia larvae hatched from eggs expelled in feces or urine are commonly used for population genetic studies. Large collections of archived miracidia on FTA cards are now available through the Schistosomiasis Collection at the Natural History Museum (SCAN). Here we describe protocols for whole genome amplification of Schistosoma mansoni and Schistosome haematobium miracidia from these cards, as well as real time PCR quantification of amplified schistosome DNA. We used microgram quantities of DNA obtained for exome capture and sequencing of single miracidia, generating dense polymorphism data across the exome. These methods will facilitate the transition from population genetics, using limited numbers of markers to population genomics using genome-wide marker information, maximising the value of collections such as SCAN.
When a rigid body collides with a liquid surface with sufficient velocity, it creates a splash curtain above the surface and entrains air behind the sphere, creating a cavity below the surface. While cavity dynamics has been studied for over a century, this work focuses on the water entry characteristics of deformable elastomeric spheres, which has not been studied. Upon free surface impact, an elastomeric sphere deforms significantly, giving rise to large-scale material oscillations within the sphere resulting in unique nested cavities. We study these phenomena experimentally with high-speed imaging and image processing techniques. The water entry behaviour of deformable spheres differs from rigid spheres because of the pronounced deformation caused at impact as well as the subsequent material vibration. Our results show that this deformation and vibration can be predicted from material properties and impact conditions. Additionally, by accounting for the sphere deformation in an effective diameter term, we recover previously reported characteristics for time to cavity pinch off and hydrodynamic force coefficients for rigid spheres. Our results also show that velocity change over the first oscillation period scales with the dimensionless ratio of material shear modulus to impact hydrodynamic pressure. Therefore, we are able to describe the water entry characteristics of deformable spheres in terms of material properties and impact conditions.
14C dates of relict tufa deposits at Gordale indicated a Subboreal age when the carbonate age was corrected with empirical bedrock dilution factors ‘q’ of 0.79 or 0.85. Estimates of ‘apparent age,’ based on extrapolated δ13C values were about twice those obtained with q, and the 1σ error was large. The δ13C values of tufa samples were not correlated with carbonate age and were close to −10. Application of q values in this district requires caution as they appear to be site-specific. We recommend that wherever possible, levels of 13C and 14C are measured in the associated tufa-depositing water, and an empirical dilution factor employed.
Radiocarbon (14C) produced by cosmogenic processes in the atmosphere reacts rapidly with atomic oxygen to form 14CO. The primary sink for this species is oxidation by the OH radical, the single most important oxidation mechanism for pollutants in the atmosphere. Hence, knowledge of the spatial and temporal distribution of 14CO allows important inferences to be made about atmospheric transport processes and the distribution of OH. Because the chemical lifetime of 14CO against OH attack is relatively short, 1–3 months, its distribution in the atmosphere should show modulations due to changes in 14C production caused by variations in the solar cycle. In this work we present a simple methodology to provide a time series of global 14C production to help interpret time series of atmospheric 14CO measurements covering the whole of solar cycle 23. We use data from neutron monitors, a readily available proxy for global 14C production, and show that an existing 6-year time series of 14CO data from Baring Head, New Zealand, tracks changes in global 14C production at the onset of solar cycle 23.
Elevated levels of interleukin-6 (IL-6) have been associated with the development of common mental disorders, such as depression, but its role in symptom resolution is unclear.
We examined the association between IL-6 and symptom resolution in a non-clinical sample of participants with psychological distress.
Relative to high IL-6 levels, low levels at baseline were associated with symptom resolution at follow-up [age- and sex-adjusted risk ratio (RR) = 1.15, 95% confidence interval (CI) 1.06–1.25]. Further adjustment for covariates had little effect on the association. Symptomatic participants with repeated low IL-6 were more likely to be symptom-free at follow-up compared with those with repeated high IL-6 (RR = 1.21, 95% CI 1.03–1.41). Among the symptomatic participants with elevated IL-6 at baseline, IL-6 decreased along with symptom resolution.
IL-6 is potentially related to the mechanisms underlying recovery from symptoms of mental ill health. Further studies are needed to examine these mechanisms and to confirm the findings in relation to clinical depression.
Holographic polymer dispersed liquid crystal (H-PDLC) films with partially fluorinated matrices were investigated. Electro-optical and morphological studies revealed that fluorinated composites were substantially different from non-fluorinated analogues. The addition of a fluorinated monofunctional acrylate monomer to a pentaacrylate-derived polymer matrix resulted in improved diffraction efficiency. These findings suggest that the partial fluorination of the host polymer decreases the compatibility between the matrix and liquid crystal phase. Morphological differences between fluorinated films and non-fluorinated control specimens were verified using low-voltage, high-resolution scanning electron microscopy (LVHRSEM).
In recent years, a considerable amount of research has been dedicated to synthesizing highly ordered nanostructured materials. One way to achieve this is through templated polymerizations. A novel route to fabricating such materials is through the use of lyotropic liquid crystals (LLCs) that possess highly ordered nanostructures. However, LLC phases lack the necessary physical robustness. So, templating LLC phase morphology onto other materials such as organic polymers would give a nanostructure retained as part of a robust polymeric matrix. This study focuses on the photopolymerization behavior and structure retention of hydroxyethyl acrylate (HEA) / dodecyltrimethyl ammonium bromide (DTAB) / water system in a select LC phase. The results suggest that the polymerization behavior is heavily dependent on the type of LLC structure. Specifically, lamellar aggregates polymerize faster than either cubic or isotropic morphologies due to diffusional limitations on the growing polymer chain. Monomer segregation also plays a role in determining the polymerization rates. Results also indicate that the original LLC order of these systems is largely retained upon photopolymerization although some LLC phases do change upon cure. This order would be useful in applications such as ultrafiltration membranes, separation media, and drug delivery systems.
The oxygen vacancy in silicon dioxide is currently believed to explain one of the most important defects observed in this material, the E1 ' center. To get a better understanding of the oxygen vacancy, we have investigated the equilibrium geometric structures, total energies, and charge densities of several charge states of the defect in alpha cristobalite. We also present some preliminary results for alpha quartz.
A tight-binding theory is used to study vibrational excitations of the π-bonded chain model of the Si(111)2×l surface. Some aspects of the surface phonon spectrum are discussed. We study the charge fluctuations driven by the vibrational excitations and the surface conductivity associated with the phonons. We find that a longitudinal optical phonon on the surface chains dominates the surface conductivity.
Material growth is an inherently non-equilibrium process. However, thermodynamic considerations often provide important insight into material growth, the structure of grown materials, and process control parameters. In essence, thermodynamic considerations are important when activated processes are either slow or fast on the time scale of the growth. Activated kinetic processes are important when their time scale is the same as that of growth. Realistic ab-initio calculations of material structure and dynamics can provide a microscopic understanding of both thermodynamics and the kinetics of material growth. The primary focus of this article is a recently proposed defect-assisted multiple-regrowth stabilization of cubic phases. in this theory the incorporation of vacancies at the growth face changes the relative binding energy of cubic versus hexagonal phases so that diamond and cubic boron nitride can nucleate and grow. This theory predicts that diamond nucleation and growth is enhanced under electron rich or positive ion conditions. Experimental results on growth of both diamond and cubic boron nitride that motivate and support theoretical predictions are described. Cubic boron-nitride grows under off-stoichiometric conditions. The nucleation rate of diamond is increased by many orders of magnitude when a flux of electrons impinges upon the surface. Raman line broadening and ESR measurements indicate the presence of significant concentrations of point defects. Predictions and experimental evidence for both n and p type doping will be discussed. Ab-initio calculations of key kinetic processes and thermodynamic quantities for diamond and boron nitride growth are described.
We report parameter-free self-consistent calculations of structural properties for the oxygen vacancy in silicon-dioxide using new oxygen pseudopotentials and quantum molecular dynamics simulations. Results challenge the accepted identification of the oxygen vacancy with the paramagnetic E1′ center. Bonding of the adjacent silicon atoms occurs sufficiently strongly for all charge states to inhibit the asymmetric distortion which would be required for correspondence with the E1′ center.
As part of an ongoing investigation to characterize the properties and structure of zinc halide-tellurium oxide glasses, we report preliminary measurements of the optical properties of several Nd- and Er-doped tellurites. Measurements include florescence lifetimes and estimates of the theoretical radiative lifetimes (as obtained by traditional Judd-Ofelt analysis of optical absorption spectra) as well as phonon sideband studies sensitive to vibrational characteristics near the rare earth ion. The response of these optical features to the substitution of alternative halides is examined.
The crystallography and electronic properties of the Ln2-xSr1+xMn2O7 manganese oxides adopting the n = 2 Ruddlesden-Popper (RP) structure are discussed, focusing on the structural phase diagrams and electronic properties in the vicinity of the Mn +3.5 oxidation state and in particular the ease of synthesis of single phases of these materials.
Molten salts have traditionally been used as recrystallizing solvents for the crystal growth of mixed metal oxides. In recent years, many examples of the direct preparation of mixed metal oxides from molten salt solutions have been reported. We have been exploring the use of chloride melts as a reaction media to prepare complex early transition metal oxides. Specific examples of new synthetic routes to interesting titanates and niobates will be presented. In one case, we have prepared a series of layered niobate perovskite solid acids from molten salts at temperatures well below those traditionally used in solid state syntheses. In the second case, we have discovered a new synthetic route to a poorly characterized reduced calcium titanate that is otherwise very difficult to make. The synthesis and characterization of these two classes of compounds will be described.