Diamond-Like Carbon: A Surface for Extreme, High-Wear Environments.

In this study, we present an in-depth characterization of a diamond-like carbon (DLC) film, using a range of techniques to understand the structure and chemistry of the film both in the interior and particularly at the DLC/air surface and DLC/liquid interface. The DLC film is found to be a combination of sp2 and sp3 carbon, with significant oxygen present at the surface. The oxygen seems to be present as OH groups, making the DLC somewhat hydrophilic. Quartz-Crystal Microbalance (QCM) isotherms and complementary neutron reflectivity data indicate significant adsorption of a model additive, bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT) surfactant, onto the DLC from water solutions and indicate the adsorbed film is a bilayer. This initial study of the structure and composition of a model surfactant is intended to give a clearer insight into how DLC and additives function as antiwear systems.

Ultra-low oxygen, liquid sample cell for in situ synchrotron-based small-wide angle scattering (SAXS-WAXS).

Here, we report the design and successful implementation of an ultra-low oxygen sample cell for use on the SAXS-WAXS (small-wide angle x-ray scattering) beamline I22 at DIAMOND. The rigorous exclusion of oxygen is found to require double jacketing with purge gas throughout the entire system, pipework, pumps, and the sample cell itself. This particularly includes a "double-window" arrangement at the sample location to accommodate the very tight geometrical restrictions of the sample position. The in situ cell design also requires the additional complexity of heating the sample/solution and real-time electrochemical measurements. We demonstrate the successful implementation of this arrangement with real-time in situ characterization of an iron foil corrosion evolving under the "sweet-scale environment," very anoxic conditions common, in particular, commercial situations. The formation of iron carbonate, siderite, rather than iron oxide, indicates that our system is oxygen free down very low levels (<35 ppb at 80 °C).

Universal DNA methylation age across mammalian tissues.

Aging, often considered a result of random cellular damage, can be accurately estimated using DNA methylation profiles, the foundation of pan-tissue epigenetic clocks. Here, we demonstrate the development of universal pan-mammalian clocks, using 11,754 methylation arrays from our Mammalian Methylation Consortium, which encompass 59 tissue types across 185 mammalian species. These predictive models estimate mammalian tissue age with high accuracy (r > 0.96). Age deviations correlate with human mortality risk, mouse somatotropic axis mutations and caloric restriction. We identified specific cytosines with methylation levels that change with age across numerous species. These sites, highly enriched in polycomb repressive complex 2-binding locations, are near genes implicated in mammalian development, cancer, obesity and longevity. Our findings offer new evidence suggesting that aging is evolutionarily conserved and intertwined with developmental processes across all mammals.

A Novel Study on the Role of Pressure on Surface Adsorption from Solutions.

In this work, we present experimental data on the behavior of model additives adsorbed at the solid/liquid interface as a function of pressure. We report that some additives adsorbed from non-aqueous solvents exhibit rather little variation with pressure, while others exhibit more significant changes. We also display the important pressure dependence of added water. This pressure dependence is relevant, indeed central to many commercially important situations where the adsorption of molecular species to the solid/liquid interface under high pressure is key, such as wind turbines, and this work should help in understanding how protective, anti-wear, or friction-reducing agents can persist (or not) under these extreme conditions. With a very significant gap in the fundamental understanding of the role of pressure on adsorption from solution phases, this important fundamental study provides a methodology to investigate the pressure dependence of these academically and commercially important systems. In the best case, one may even be able to predict which additives will lead to more adsorption under pressure and avoid those that may desorb.

Potential of in-plant intramuscular fat predictions to enable sheep breeders to incorporate consumer preferences in breeding programmes.

The inclusion of eating quality traits in sheep genetic improvement programmes is desirable. Intramuscular fat (IMF) plays a key role in ensuring consumer satisfaction when eating lamb, but genetic progress for IMF is constrained by a lack of routine data collection. This study investigated the potential for IMF predictor traits to substitute for measured IMF in genetic improvement programmes. Carcass and predicted IMF (near-infrared estimated IMF and marbling score) data were available on 10,113 New Zealand lambs, 1678 of which also had measured chemical IMF on a slice of M. longissimus lumborum on which the predictions of IMF had been made. Genetic antagonisms were observed between carcass lean traits and IMF. The genetic correlation between the predictors and measured IMF approached one, indicating that predictors of IMF can be used in genetic improvement programmes. Through using selection indexes, simultaneous increases in IMF and the existing terminal selection index are possible, provided all traits are measured. This study highlights the importance and potential of predicted IMF to achieve genetic improvement in traits of importance to consumers.

Corrosion inhibitor distribution on abrasive-blasted steels.

HYPOTHESIS: Abrasive-blasted steel surfaces exhibit a complex, multi-substrate environment. Adsorption to contaminant substrates can reduce the amount of available corrosion inhibitor and decrease its efficiency. Knowledge of where inhibitors preferentially adsorb is required. EXPERIMENTS: The quantitative extent and strength of adsorption of the representative corrosion inhibitor benzotriazole (BTAH) from toluene to particular substrates is given, including corrections for solution self-association, and complemented by X-ray photoelectron spectroscopy (XPS), sum-frequency generation spectroscopy (SFG), and quartz crystal microbalance (QCM) measurements. FINDINGS: All substrates show adsorbed BTAH layers. Based on the adsorption strength, preferential adsorption is found to be in the order steel > iron oxide > calcium carbonate and garnet > silica - this is relevant when there is limited BTAH. However, with ample BTAH, the amounts adsorbed in the plateau regions of the isotherm are more relevant and the order is calcium carbonate and silica > iron oxide > garnet > steel. Although the contaminant substrates deplete the BTAH concentration, the steel should still have a complete monolayer of BTAH inhibitor. This work is part of a larger initiative developing novel methods of corrosion inhibitor delivery via the blasting process, to prevent corrosion between blasting and repainting.

SNP discovery and population structure analysis in Lassi and Marecha camel breeds using a genotyping by sequencing method.

Pakistani camels have been classified socio-geographically into 20 breeds, but they have not yet been subjected to substantial selective pressures and the genetic basis for these breeds is not understood. However, it should be possible to distinguish them by use of molecular data. This study investigated the genetic diversity and population structure within and between two major Pakistani camel breeds, Marecha and Lassi. As no SNP array is currently available, we first identified 63 619 SNPs using a genotyping by sequencing approach. After quality control, a panel of 36 926 SNPs was used in the analysis. Population structure was investigated with a principal coordinate analysis as well as a cluster analysis using NetView, and multilocus heterozygosity analysis to explore between- and within-breed genetic variation. In addition, between-breed variation was explored using the fixation index, FST . We also compared relationship matrices computed using the VanRaden SNP-based method and a method developed specifically for genotyping by sequencing data. Among the two camel breeds, Lassi showed a lower level of genetic diversity whereas Marecha showed a higher level. As a genotyping platform has not yet been developed for the camel, the SNPs discovered in this study will be useful in future genetic studies in camels.

Using genotyping-by-sequencing to predict gender in animals.

Gender assignment errors are common in some animal species and lead to inaccuracies in downstream analyses. Procedures for detecting gender misassignment are available for array-based SNP data but are still being developed for genotyping-by-sequencing (GBS) data. In this study, we describe a method for using GBS data to predict gender using X and Y chromosomal SNPs. From a set of 1286 X chromosomal and 23 Y chromosomal deer (Cervus sp.) SNPs discovered from GBS sequence reads, a prediction model was built using a training dataset of 422 Red deer and validated using a test dataset of 868 Red deer and Wapiti deer. Prediction was based on the proportion of heterozygous genotypes on the X chromosome and the proportion of non-missing genotypes on the Y chromosome observed in each individual. The concordance between recorded gender and predicted gender was 98.6% in the training dataset and 99.3% in the test dataset. The model identified five individuals across both datasets with incorrect recorded gender and was unable to predict gender for another five individuals. Overall, our method predicted gender with a high degree of accuracy and could be used for quality control in gender assignment datasets or for assigning gender when unrecorded, provided a suitable reference genome is available.

Heritability of ram mating success in multi-sire breeding situations.

Multi-sire mating of a mob of ewes is commonly used in commercial sheep production systems. However, ram mating success (defined as the number of lambs sired by an individual) can vary between rams in the mating group. If this trait was repeatable and heritable, selection of rams capable of siring larger numbers of lambs could reduce the number of rams required for mating and ultimately lead to increased genetic gain. However, genetic correlations with other productive traits, such as growth and female fertility, could influence the potential for ram mating success to be used as a selection trait. In order to investigate this trait, parentage records (including accuracy of sire assignment) from 15 commercial ram breeding flocks of various breeds were utilised to examine the repeatability and heritability of ram mating success in multi-sire mating groups. In addition, genetic and phenotypic correlations with growth and female fertility traits were estimated using ASReml. The final model used for the ram mating success traits included age of the ram and mating group as fixed effects. Older rams (3+years old) had 15% to 20% greater mating success than younger rams (1 or 2 years of age). Increasing the stringency of the criteria for inclusion of both an individual lamb, based on accuracy of sire assignment, or a whole mating group, based on how many lambs had an assigned sire, increased repeatability and heritability estimates of the ram mating success traits examined. With the most stringent criteria employed, where assignment of sire accuracy was >0.95 and the total number of lambs in the progeny group that failed to have a sire assigned was<0.05, repeatability and heritability for loge(number of lambs) was 0.40±0.09 and 0.26±0.12, respectively. For proportion of lambs sired, repeatability and heritability were both 0.30±0.09. The two ram mating traits (loge(nlamb) and proportion) were highly correlated, both phenotypically and genetically (0.88±0.01 and 0.94±0.06, respectively). Both phenotypic and genetic correlations between ram mating success and growth and other female fertility traits were low and non-significant. In conclusion, there is scope to select rams capable of producing high numbers of progeny and thus increase selection pressure on rams to increase genetic gain.

High-pressure discovery of ß-NiBi.

Herein, we present the discovery of a new high-pressure phase in the Ni-Bi system, ß-NiBi, which crystallizes in the TlI structure type. The powerful technique of in situ high-pressure and high-temperature powder X-ray diffraction enabled observation of the formation of ß-NiBi and its reversible reconversion to the ambient pressure phase, α-NiBi.

Multilayering of Calcium Aerosol-OT at the Mica/Water Interface Studied with Neutron Reflection: Formation of a Condensed Lamellar Phase at the CMC.

Using specular neutron reflection, the adsorption of sodium and calcium salts of the surfactant bis(2-ethylhexyl) sulfosuccinate (Aerosol-OT or AOT) has been studied at the mica/water interface at concentrations between 0.1 and 2 CMC. The pH dependence of the adsorption was also probed. No evidence of the adsorption of Na(AOT) was found even at the critical micelle concentration (CMC) while the calcium salt was found to adsorb significantly at concentrations of 0.5 CMC and above. This interesting and somewhat unexpected finding demonstrates that counterion identity may be used to tune the adsorption of anionic surfactants on anionic surfaces. At the CMC, three condensed bilayers of Ca(AOT)2 were adsorbed at pH 7 and 9 and four bilayers adsorbed at pH 4. Multilayering at the CMC of Ca(AOT)2 on the mica surface is an unusual feature of this surfactant/surface combination. Only single bilayer adsorption has been observed at other surfaces at the CMC. We suggest this arises from the high charge density of mica which must provide an excellent template for the surfactant.

Complete bilayer adsorption of C16TAB on the surface of mica using neutron reflection.

We present neutron reflection data from an alkylammonium surfactant (C16TAB) at the mica/water interface. The system is studied in situ in a noninvasive manner and indicates the formation of a complete adsorbed bilayer with little evidence of defects. A detailed analysis suggests that the data are not consistent with some other previously reported adsorbed structures, such as micelles or cylinders.

Soft-sphere soft glasses.

Molecular dynamics simulations have been used to compute physical properties of model fluids in which the particles interacted via the soft-sphere pair potential (SSP) phi(r)=epsilon(sigma/r)(n), where epsilon and sigma are the characteristic energy and distance, respectively. The emphasis is on small values of n, tending to the lower theromodynamically allowed bound of 3+. An accurate equation of state for the SSP fluid is obtained, consisting of two terms, and as n-->3+, the compressibility factor, Z tends to Z=B(2)zeta(n/3) for zeta>0, where B(2) is the second virial coefficient, and zeta=piNsigma(3)/6V is a nominal packing fraction for N particles in volume V. A simple formula for the position of the first peak in the radial distribution function in the soft particle limit is proposed and shown to agree with the simulation data. The fluid phase velocity autocorrelation function at fluid-solid coexistence becomes more oscillatory as n decreases. Values for the self-diffusion coefficient D and shear viscosity eta were calculated as a function of n and density, and these were used to estimate the n-dependence of an ideal glass transition. The glass transition shifts relatively further into the solid part of the phase diagram as softness ( approximately 1/n) increases. D decreases by ca. 75% and eta increases by about a factor of 3 along the fluid-solid coexistence line from n=infinity to 3.25. Non-Gaussian behavior was calculated from the particle displacements as a function of particle softness. A screened soft-sphere potential, SSSP, was introduced to explore the effects for small n of the long range part of the potential in relation to the scale of the local structure. The SSSP with suitable analytic form and parameters can give statistically indistinguishable results from the full SSP for the static properties, D and eta.

Mixing in adsorbed monolayers: perfluorinated alkanes.

The mixing behavior of binary combinations of perfluoroalkanes in the bulk and in solid monolayers adsorbed at the graphite/liquid interface, determined by calorimetry and powder diffraction, is reported. The perfluoroalkanes are found to generally have a smaller excess enthalpy of mixing on the surface than in the bulk, and their relative size ratio is a good parameter to predict the mixing behavior. The excess enthalpy of mixing for perfluoroalkanes is found to be significantly smaller than that of the closely related hydrocarbons. The preferential adsorption of longer homologues over shorter ones is observed. Interestingly, the extent of preferential adsorption with relative size ratio is very similar to that of the hydrocarbons. These results can be understood in terms of the increased compressibility and lower polarizability of the perfluoroalkanes compared to hydrocarbons.

Filtration of deformable emulsion droplets.

Oil-in-water (o/w) emulsions of different droplet size were filtered on membranes of various pore sizes to investigate the growth and behaviour of o/w filter cakes. The cake desorptivity S and the filter membrane resistance R were measured at various filtration pressures P. The variation of S with P shows that filter cake oil droplets of radius a are effectively rigid for P << gamma/a and fully deformable for P >> gamma/a, where gamma is the oil-water interfacial tension. For the largest P, when S became P-independent, the filter cake remained water-permeable as expected from theory.

The crystalline structures of carboxylic acid monolayers adsorbed on graphite.

X-ray and neutron diffraction have been used to investigate the formation of solid crystalline monolayers of all of the linear carboxylic acids from C(6) to C(14) at submonolayer coverage and from C(8) to C(14) at multilayer coverages, and to characterize their structures. X-rays and neutrons highlight different aspects of the monolayer structures, and their combination is therefore important in structural determination. For all of the acids with an odd number of carbon atoms, the unit cell is rectangular of plane group pgg containing four molecules. The members of the homologous series with an even number of carbon atoms have an oblique unit cell with two molecules per unit cell and plane group p2. This odd-even variation in crystal structure provides an explanation for the odd-even variation observed in monolayer melting points and mixing behavior. In all cases, the molecules are arranged in strongly hydrogen-bonded dimers with their extended axes parallel to the surface and the plane of the carbon skeleton essentially parallel to the graphite surface. The monolayer crystal structures have unit cell dimensions similar to certain close-packed planes of the bulk crystals, but the molecular arrangements are different. There is a 1-3% compression on increasing the coverage over a monolayer.

Liquid crystalline elastomers: dynamics and relaxation of microstructure.

The equilibrium mechanical response of nematic elastomers can be soft or hard depending on the relation between the imposed strains and the nematic director, in particular, if the local nematic director is able to respond by rotating. The dynamical response proves to be equally unusual. We examine the linear dynamic mechanical response of monodomain nematic elastomers under shear and the aspects of time-temperature superposition of the dynamical data across phase-transition regions. In the low-frequency region of the master curves, one finds a dramatic reduction of rubber plateau modulus and the rise in internal dissipation: in the shear geometries compatible with dynamic soft elasticity. Power-law variation of the storage modulus with frequency G' proportional, variant omega(a) agrees very well with the results of static stress relaxation, where each relaxation curve obeys the analogous power law G' proportional, variant t(-a) in the corresponding region of long times and temperatures.

NMR study of n-dodecane adsorbed on graphite.

In this brief contribution we demonstrate that 1H and 2H NMR spectroscopy can be an effective method of investigating adsorption from liquids at the solid-liquid interface. The method is illustrated here with the adsorption of a simple alkane adsorbed on graphite, in particular the system n-dodecane and graphite at coverages of 1 and 5 monolayers. Static single-pulse proton nuclear magnetic resonance and static quadrupolar echo deuterium nuclear magnetic resonance spectra were recorded for both coverages. The experimental NMR results presented here show features clearly consistent with earlier calorimetric and neutron scattering work and demonstrate the formation of solid adsorbed layers that coexist with the bulk adsorbate with both isotopes. This ability to probe both deuterated and protonated materials simultaneously illustrates that this experimental approach can be readily extended to investigate the adsorption behaviour of multicomponent mixtures.