Can hydrodynamic contact line paradox be solved by evaporation--condensation?

We investigate a possibility to regularize the hydrodynamic contact line singularity in the configuration of partial wetting (liquid wedge on a solid substrate) via evaporation-condensation, when an inert gas is present in the atmosphere above the liquid. The no-slip condition is imposed at the solid-liquid interface and the system is assumed to be isothermal. The mass exchange dynamics is controlled by vapor diffusion in the inert gas and interfacial kinetic resistance. The coupling between the liquid meniscus curvature and mass exchange is provided by the Kelvin effect. The atmosphere is saturated and the substrate moves at a steady velocity with respect to the liquid wedge. A multi-scale analysis is performed. The liquid dynamics description in the phase-change-controlled microregion and visco-capillary intermediate region is based on the lubrication equations. The vapor diffusion is considered in the gas phase. It is shown that from the mathematical point of view, the phase exchange relieves the contact line singularity. The liquid mass is conserved: evaporation existing on a part of the meniscus and condensation occurring over another part compensate exactly each other. However, numerical estimations carried out for three common fluids (ethanol, water and glycerol) at the ambient conditions show that the characteristic length scales are tiny

Allosteric modulation of AURKA kinase activity by a small-molecule inhibitor of its protein-protein interaction with TPX2.

The essential mitotic kinase Aurora A (AURKA) is controlled during cell cycle progression via two distinct mechanisms. Following activation loop autophosphorylation early in mitosis when it localizes to centrosomes, AURKA is allosterically activated on the mitotic spindle via binding to the microtubule-associated protein, TPX2. Here, we report the discovery of AurkinA, a novel chemical inhibitor of the AURKA-TPX2 interaction, which acts via an unexpected structural mechanism to inhibit AURKA activity and mitotic localization. In crystal structures, AurkinA binds to a hydrophobic pocket (the 'Y pocket') that normally accommodates a conserved Tyr-Ser-Tyr motif from TPX2, blocking the AURKA-TPX2 interaction. AurkinA binding to the Y- pocket induces structural changes in AURKA that inhibit catalytic activity in vitro and in cells, without affecting ATP binding to the active site, defining a novel mechanism of allosteric inhibition. Consistent with this mechanism, cells exposed to AurkinA mislocalise AURKA from mitotic spindle microtubules. Thus, our findings provide fresh insight into the catalytic mechanism of AURKA, and identify a key structural feature as the target for a new class of dual-mode AURKA inhibitors, with implications for the chemical biology and selective therapeutic targeting of structurally related kinases.We are grateful for the access and support at beamlines i02, i03 and i04-1 at Diamond Light Source at Harwell, UK (proposal MX9007 and MX9537) and at beamline Proxima1 at the SOLEIL Synchrotron, Gif-sur-Yvette, France. We are grateful for access and support from the X-ray and biophysics facilities (Dept. of Biochemistry) and the screening/imaging facility (MRC Cancer Unit). M.J. was supported by a Cancer Research UK studentship held in the labs of DS and ARV, PS and MR by a Wellcome Trust Strategic Award to ARV and MH, and DJH, BH, AJN and GM by grants from the UK Medical Research Council to ARV.This is the final version of the article. It first appeared from Nature Publishing Group via http://dx.doi.org/10.1038/srep2852

Expression of alternansucrase in potato plants

Alternan, which consists of alternating α-(1→3)/α-(1→6)-linked glucosyl residues, was produced in potato tubers by expressing a mature alternansucrase (Asr) gene from Leuconostoc mesenteroides NRRL B-1355 in potato. Detection of alternan was performed by enzyme-linked immunosorbent assay in tuber juices, revealing a concentration between 0.3 and 1.2 mg g-1 fresh wt. The Asr transcript levels correlated well with alternan accumulation in tuber juices. It appeared that the expression of sucrose-regulated starch-synthesizing genes (ADP-glucose pyrophosphorylase subunit S and granule-bound starch synthase I) was down-regulated. Despite this, the physico-chemical properties of the transgenic starches were unaltered. These results are compared to those obtained with other transgenic potato plants producing mutan [α-(1→3)-linked glucosyl residues] and dextran [α-(1→6)-linked glucosyl residues]

Fatigue life of machined components

A correlation between machining process and fatigue strength of machined components clearly exists. However, a complete picture of the knowledge on this is not readily available for practical applications. This study addresses this issue by investigating the effects of machining methods on fatigue life of commonly used materials, such as titanium alloys, steel, aluminium alloys and nickel alloys from previous literature. Effects of turning, milling, grinding and different non-conventional machining processes on fatigue strength of above-mentioned materials have been investigated in detail with correlated information. It is found that the effect of materials is not significant except steel in which phase change causes volume expansion, resulting in compressive/tensile residual stresses based on the amounts of white layers. It is very complex to identify the influence of surface roughness on the fatigue strength of machined components in the presence of residual stresses. The polishing process improves the surface roughness, but removes the surface layers that contain compressive residual stresses to decrease the fatigue strength of polished specimens. The compressive and tensile residual stresses improve and reduce fatigue strength, respectively. Grinding process induces tensile residual stresses on the machined surfaces due to high temperature generation. On the other hand, milling and turning processes induce compressive residual stresses. High temperature non-conventional machining generates a network of micro-cracks on the surfaces in addition to tensile residual stresses to subsequently reduce fatigue strength of machined components. Embedded grits of abrasive water jet machining degrade the fatigue performance of components machined by this method

Nanomaterials by severe plastic deformation: review of historical developments and recent advances

International audienceSevere plastic deformation (SPD) is effective in producing bulk ultrafine-grained and nanostructured materials with large densities of lattice defects. This field, also known as NanoSPD, experienced a significant progress within the past two decades. Beside classic SPD methods such as high-pressure torsion, equal-channel angular pressing, accumulative roll-bonding, twist extrusion, and multi-directional forging, various continuous techniques were introduced to produce upscaled samples. Moreover, numerous alloys, glasses, semiconductors, ceramics, polymers, and their composites were processed. The SPD methods were used to synthesize new materials or to stabilize metastable phases with advanced mechanical and functional properties. High strength combined with high ductility, low/room-temperature superplasticity, creep resistance, hydrogen storage, photocatalytic hydrogen production, photocatalytic CO2 conversion, superconductivity, thermoelectric performance, radiation resistance, corrosion resistance, and biocompatibility are some highlighted properties of SPD-processed materials. This article reviews recent advances in the NanoSPD field and provides a brief history regarding its progress from the ancient times to modernity

Nuclear localisation of Aurora-A: its regulation and significance for Aurora-A functions in cancer.

The Aurora-A kinase regulates cell division, by controlling centrosome biology and spindle assembly. Cancer cells often display elevated levels of the kinase, due to amplification of the gene locus, increased transcription or post-translational modifications. Several inhibitors of Aurora-A activity have been developed as anti-cancer agents and are under evaluation in clinical trials. Although the well-known mitotic roles of Aurora-A point at chromosomal instability, a hallmark of cancer, as a major link between Aurora-A overexpression and disease, recent evidence highlights the existence of non-mitotic functions of potential relevance. Here we focus on a nuclear-localised fraction of Aurora-A with oncogenic roles. Interestingly, this pool would identify not only non-mitotic, but also kinase-independent functions of the kinase. We review existing data in the literature and databases, examining potential links between Aurora-A stabilisation and localisation, and discuss them in the perspective of a more effective targeting of Aurora-A in cancer therapy

Contact line singularity at partial wetting during evaporation driven by substrate heating

We present a theoretical investigation of the evaporation of a liquid on a solid substrate into the atmosphere of its pure vapor. The evaporation is provoked by the overheating of the substrate above the saturation temperature. At partial wetting, the liquid forms a wedge ending at the triple liquid-vapor-solid contact line (CL). The wedge region is extremely important in all evaporation geometries (bubble, drop, meniscus in a capillary) for two reasons. First, in this region a significant part of the evaporative heat flux is spent to compensate the latent heat. Second, a strong meniscus curvature that occurs in this region leads to the apparent contact angle larger than its actual microscopic value. We show that unlike the conventional diffusive evaporation models, the evaporation rate at the CL is bounded and is defined by the CL velocity. In particular the evaporation rate vanishes at the CL when it is immobile. This means that the slip length is not essential for the contact line singularity relaxation. The pressure boundary conditions at the CL are also derived. An analytic expression for the apparent contact angle (valid in the asymptotic limit of vanishing overheating) is derived. It is compared to numerical results

Drivers of functional and taxonomical diversity within fragmented grasslands

Seminatural grasslands are biodiversity hotspots in the increasingly fragmented Central European landscape. In consequence vegetation scientists and conservationists are looking for factors maintaining such diversity under the threat of land-use changes. In our study, we surveyed around 1200 grassland patches within a  region of 400 km2 in the Železné hory Mts. (Czech Republic). According to field measures and remote sensing information these patches varied in terms of productivity, wetness, disturbance, size and connectivity and different historical trajectories. We evaluated the effects of these factors on both taxonomical and functional biodiversity, and community functional properties. As expected, taxonomic diversity was positively correlated with grassland area and connectivity and was also higher on traditionally managed meadows. This effect of management is nevertheless meadow type specific and is much more pronounced on wet compare to dry meadows. Functional diversity, such as taxonomical, is positively affected by meadow size, but on the contrary, is higher on dry meadows. Mown meadows host less clonal, smaller, earlier flowering species with lighter seeds, however there are considerable differences among habitat types. In addition, the decrease in meadow size has more negative effect on species richness in unmanaged meadows in contrast to managed ones. This indicates the high importance of traditional management for maintaining species diversity of smaller grassland patches which often represent important landscape elements maintaining connectivity but are mostly omitted in conservation planning