SPH simulations of turbulence in fixed and rotating boxes in two dimensions with no-slip boundaries

In this paper we study decaying turbulence in fixed and rotating boxes in two dimen- sions using the particle method SPH. The boundaries are specified by boundary force particles, and the turbulence is initiated by a set of gaussian vortices. In the case of fixed boxes we recover the results of Clercx and his colleagues obtained using both a high accuracy spectral method and experiments. Our results for fixed boxes are also in close agreement with those of Monaghan1 and Robinson and Monaghan2 obtained using SPH. A feature of decaying turbulence in no-slip, square, fixed boundaries is that the angular momentum of the fluid varies with time because of the reaction on the fluid of the viscous stresses on the boundary. We find that when the box is allowed to rotate freely, so that the total angular momentum of box and fluid is constant, the change in the angular momentum of the fluid is a factor ~ 500 smaller than is the case for the fixed box, and the final vorticity distribution is different. We also simulate the behaviour of the turbulence when the box is forced to rotate with small and large Rossby number, and the turbulence is initiated by gaussian vortices as before. If the rotation of the box is maintained after the turbulence is initiated we find that in the rotating frame the decay of kinetic energy, enstrophy and the vortex structure is insensitive to the angular velocity of the box. On the other hand, If the box is allowed to rotate freely after the turbulence is initiated, the evolved vortex structure is completely different

Development of efficient micropropagation protocol for Withania coagulans (Stocks) Dunal

The present study describes the development of efficient micropropagation protocol for a commercially important medicinal plant Withania coagulans. Nodal segments were immersed in various concentrations of cefotaxime, viz 100, 250, 500 and 750 mgl-1 for 5 min and implanted on Murashige and Skoog medium (MS) medium fortified with 6-benzyladenine (BA) (2 to 4 mgl-1) or indolebutyric acid (IBA) (0.25 to 0.5 mgl-1) either alone or in combination with different concentrations. Of the four concentrations of cefotaxime tested, the 250 mgL-1 showed nonphytotoxic effect on cultures and completely eliminated bacterial infection. Direct multiple shoots differentiation occurred in cultured explants without intervening callus phase and the maximum number of shoots (7.2 ± 1.0 per explant) and elongation (7 ± 1.4 cm) were achieved on MS media containing 2 mgl-1 BA + 0.5 mgl-1 IBA. For induction of stout root system, the shoot buds were cultured on ½MS medium fortified with different concentrations of IBA (1 to 4 mgl-1), indole-3-acetic acid (IAA) (0.25 to 1.0 mgl-1) and kinetin (Kin) (1 to 2 mgl-1). MS medium with 2 mgl-1 IBA was found most effective for the induction of stout root system. Well-rooted plantlets were transferred to outside pots containing sterile soil, and sand mixture (2:1) showed 75% survival.Key words: In vitro, medicinal plant, propagation, Withania coagulans

Parametrised polyconvex hyperelasticity with physics-augmented neural networks

In the present work, neural networks are applied to formulate parametrised hyperelastic constitutive models. The models fulfill all common mechanical conditions of hyperelasticity by construction. In particular, partially input-convex neural network (pICNN) architectures are applied based on feed-forward neural networks. Receiving two different sets of input arguments, pICNNs are convex in one of them, while for the other, they represent arbitrary relationships which are not necessarily convex. In this way, the model can fulfill convexity conditions stemming from mechanical considerations without being too restrictive on the functional relationship in additional parameters, which may not necessarily be convex. Two different models are introduced, where one can represent arbitrary functional relationships in the additional parameters, while the other is monotonic in the additional parameters. As a first proof of concept, the model is calibrated to data generated with two differently parametrised analytical potentials, whereby three different pICNN architectures are investigated. In all cases, the proposed model shows excellent performance

Essential oil constituents and biological activities of leaf extracts of semenovia suffruticosa from Iran

Semenovia suffruticosa (Freyn et Bornm.) Manden. is one of the species of genus Semenovia (Apiaceae family). The essential oil of S. suffruticosa was obtained by hydrodistillation and analysed by gas chromatography coupled to mass spectrometry (GC/MS). The main components were cis-\uce\ub2-ocimene (12.9%), linalool (9.5%), \uce\ub3-terpinene (9.0%) and \uce\ub1-terpinolene (7.4%), representing the 38.8% of the oil. Antibacterial activity of S. suffruticosa ethanol, chloroform, ethyl acetate and aqueous leaf extracts was evaluated for the first time. The various extracts were tested by the disc-diffusion assay for antimicrobial activity against common animal and human infectious bacteria. Pseudomonas aeruginosa exhibited the highest sensitivity against the extracts, with a 13-15 mm zone of inhibition. Antiradical activity of S. suffruticosa ethanol, chloroform, ethyl acetate and aqueous leaf extracts was determined by DPPH (2,2-diphenyl-1-picrylhydrazyl) radical, FRAP (ferric reducing antioxidant power) and \uce\ub2-carotene/linoleic acid assays. Ethanol extract was the most powerful free radical scavenger in all these methods. These results, though preliminary, suggest that leaf extracts of S. suffruticosa exert promising antioxidant and antibacterial activities

Microwave studies of the fractional Josephson effect in HgTe-based Josephson junctions

The rise of topological phases of matter is strongly connected to their potential to host Majorana bound states, a powerful ingredient in the search for a robust, topologically protected, quantum information processing. In order to produce such states, a method of choice is to induce superconductivity in topological insulators. The engineering of the interplay between superconductivity and the electronic properties of a topological insulator is a challenging task and it is consequently very important to understand the physics of simple superconducting devices such as Josephson junctions, in which new topological properties are expected to emerge. In this article, we review recent experiments investigating topological superconductivity in topological insulators, using microwave excitation and detection techniques. More precisely, we have fabricated and studied topological Josephson junctions made of HgTe weak links in contact with two Al or Nb contacts. In such devices, we have observed two signatures of the fractional Josephson effect, which is expected to emerge from topologically-protected gapless Andreev bound states. We first recall the theoretical background on topological Josephson junctions, then move to the experimental observations. Then, we assess the topological origin of the observed features and conclude with an outlook towards more advanced microwave spectroscopy experiments, currently under development.Comment: Lectures given at the San Sebastian Topological Matter School 2017, published in "Topological Matter. Springer Series in Solid-State Sciences, vol 190. Springer

RF characterisation of new coatings for future circular collider beam screens

For the future high energy colliders being under the design at this moment, the choice of a low surface impedance beam screen coating material has become of fundamental importance to ensure sufficiently low beam impedance and consequently guaranteed stable operation at high currents. We have studied the use of high-temperature superconducting coated conductors as possible coating materials for the beam screen of the FCC-hh. In addition, amorphous carbon coating and laser-based surface treatment techniques are effective surface treatments to lower the secondary electron yield and minimise the electron cloud build-up. We have developed and adapted different experimental setups based on resonating structures at frequencies below 10 GHz to study the response of these coatings and their modified surfaces under the influence of RF fields and DC magnetic fields up to 9¿T. Taking the FCC-hh as a reference, we will show that the surface resistance for REBCO-CCs is much lower than that of Cu. Further we show that the additional surface modifications can be optimised to minimise their impact on the surface impedance. Results from selected coatings will be presented.Work supported by CERN under Grants FCC-GOV-CC-0210 (KE4945/ATS), FCC-GOV-CC-0209 (KE4946/ATS) and FCC-GOV-CC0208 (KE4947/ATS). ICMAB funding through RTI2018-095853-B-C21 SuMaTe from MICINN and co-financing by the European Regional Development Fund, 2017-SGR 1519 from Generalitat de Catalunya, and COST Action NANOCO-HYBRI (CA16218) from EU, the Center of Excellence award Severo Ochoa CEX2019-000917-S. UPC funding through the Unit of Excellence Maria de Maetzu MDM2016-0600. N. Tagdulang and A. Romanov acknowledge MSCA-COFUND-2016-754397 for the PhD grant.Peer ReviewedPostprint (published version

Development and optimisation of spironolactone nanoparticles for enhanced dissolution rates and stability

Stable solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) formulations to enhance the dissolution rates of poorly soluble drug spironolactone (SP) were being developed. Probe ultra-sonication method was used to prepare SLNs and NLCs. All NLCs contained stearic acid (solid lipid carrier) and oleic acid (liquid lipid content), whereas, SLNs were prepared and optimised by using the solid lipid only. The particles were characterised in terms of particle size analysis, thermal behaviour, morphology, stability and in vitro release. The zeta sizer data revealed that the increase in the concentration of oleic acid in the formulations reduced the mean particle size and the zeta potential. The increase in concentration of oleic acid from 0 to 30% (w/w) resulted in a higher entrapment efficiency. All nanoparticles were almost spherically shaped with an average particle size of about ∼170 nm. The DSC traces revealed that the presence of oleic acid in the NLC formulations resulted in a shift in the melting endotherms to a higher temperature. This could be attributed to a good long-term stability of the nanoparticles. The stability results showed that the particle size remained smaller in NLC compared to that of SLN formulations after 6 months at various temperatures. The dissolution study showed about a 5.1- to 7.2-fold increase in the release of the drug in 2 h compared to the raw drug. Comparing all nanoparticle formulations indicated that the NLC composition with a ratio of 70:30 (solid:liquid lipid) is the most suitable formulation with desired drug dissolution rates, entrapment efficiency and physical stability