On the uniqueness of the non-minimal matter coupling in massive gravity and bigravity

In de Rham-Gabadadze-Tolley (dRGT) massive gravity and bigravity, a non-minimal matter coupling involving both metrics generically re-introduces the Boulware--Deser (BD) ghost. A non-minimal matter coupling via a simple, yet specific composite metric has been proposed, which eliminates the BD ghost below the strong coupling scale. Working explicitly in the metric formulation and for arbitrary spacetime dimensions, we show that this composite metric is the unique consistent non-minimal matter coupling below the strong coupling scale, which emerges out of two diagnostics, namely, absence of Ostrogradski ghosts in the decoupling limit and absence of the BD ghost from matter quantum loop corrections.Comment: v2: references added, matches accepted version in Physics Letters B v1: 6 pages, two-colum

Salt Secretion Is Essential for Xero-Halophyte \u3cem\u3eReaumuria soongorica\u3c/em\u3e Responding to Osmotic Stress

Reaumuria soongorica, a xero-halophyte semi-shrub belonging to Tamaricaceae with excellent adaptability to adverse arid and salinity environments of northwest China, serves important ecological roles in the improvement of saline-alkali soil and dune stabilisation, and also is an attractive fodder shrub in desert steppe (Ma et al. 2011). Previous studies demonstrated that secreting salt via salt glands is an important strategy for R. soongorica adapting to high salinity environments (Zhou et al. 2012). However, very little is known about the role of salt secretion in the plant’s responses to drought. Therefore, in the present work, R. soongorica seedlings were subjected to osmotic stress in the presence or absence of additional NaCl to determine the potential relationship between salt secretion and drought tolerance of R. soongorica seedlings

Corrosion protection of carbon steel by an epoxy resin containing organically modified clay

This study focusses on the use of montmorillonite clay (MMT) treated with an organic compound (aminotrimethylphosphonic acid (ATMP)) and dispersed in an epoxy resin to improve corrosion protection of carbon steel. X-ray diffraction was performed to verify that the individual silicate layers were separated and dispersed in the epoxy resin. Corrosion resistance of the coated steel was evaluated by electrochemical impedance spectroscopy (EIS) and local electrochemical impedance spectroscopy (LEIS). Three systems were tested: the epoxy clear-coat, the epoxy resin containing 2 wt.% clay and the epoxy resin containing 2 wt.% clay modified byATMP (ATMP-modified clay). From conventional EIS, it was shown that the incorporation of clay or ATMP-modified clay in the epoxy matrix significantly improved the barrier properties of the coating. The corrosion resistance of the carbon steel coated by the epoxy resin containing ATMP-modified clay was higher than that obtained for the system containing non-treated clay. Local electrochemical measurements performed on scratched samples revealed the inhibitive role of ATMP at the carbon steel/coating interface

Do Deep Learning Methods Really Perform Better in Molecular Conformation Generation?

Molecular conformation generation (MCG) is a fundamental and important problem in drug discovery. Many traditional methods have been developed to solve the MCG problem, such as systematic searching, model-building, random searching, distance geometry, molecular dynamics, Monte Carlo methods, etc. However, they have some limitations depending on the molecular structures. Recently, there are plenty of deep learning based MCG methods, which claim they largely outperform the traditional methods. However, to our surprise, we design a simple and cheap algorithm (parameter-free) based on the traditional methods and find it is comparable to or even outperforms deep learning based MCG methods in the widely used GEOM-QM9 and GEOM-Drugs benchmarks. In particular, our design algorithm is simply the clustering of the RDKIT-generated conformations. We hope our findings can help the community to revise the deep learning methods for MCG. The code of the proposed algorithm could be found at https://gist.github.com/ZhouGengmo/5b565f51adafcd911c0bc115b2ef027c

Tetrakis[μ-3-(3-hy­droxy­phen­yl)propenoato]bis­{aqua­(2,2′-bipyridine)­[3-(3-hy­droxy­phen­yl)propenoato]neodymium(III)} 2,2′-bipyridine disolvate dihydrate

The dinuclear title compound, [Nd2(C9H7O3)6(C10H8N2)2]·2C10H8N2·2H2O, was synthesized under hydro­thermal conditions. The centrosymmetric complex consists of two nine-coordinated Nd3+ cations, six 3-hy­droxy­cinnamate anions and two chelating 2,2′-bipyridine mol­ecules. The coordination geometry around the cations can be best described as distorted tricapped trigonal-prismatic. The carboxyl­ate groups show different coordination and bridging modes. Two of them chelate to one Nd3+ cation, two bridge the two cations in a bis-monodentate fashion, and two chelate to one and bridge monodentately to the symmetry-related Nd3+ cation. The dinuclear mol­ecule is surrounded by two 2,2′-bipyridine solvent and two water mol­ecules. Extensive O—H⋯O and O—H⋯N hydrogen-bonding inter­actions between the components lead to the formation of a three-dimensional network

Efficient non-collinear antiferromagnetic state switching induced by orbital Hall effect in chromium

Recently orbital Hall current has attracted attention as an alternative method to switch the magnetization of ferromagnets. Here we present our findings on electrical switching of antiferromagnetic state in Mn3Sn/Cr, where despite the much smaller spin Hall angle of Cr, the switching current density is comparable to heavy metal based heterostructures. On the other hand, the inverse process, i.e., spin-to-charge conversion in Cr-based heterostructures is much less efficient than the Pt-based equivalents, as manifested in the almost one order of magnitude smaller terahertz emission intensity and spin current induced magnetoresistance in Cr-based structures. These results in combination with the slow decay of terahertz emission against Cr thickness (diffusion length of ~11 nm) suggest that the observed magnetic switching can be attributed to orbital current generation in Cr, followed by efficient conversion to spin current. Our work demonstrates the potential of light metals like Cr as an efficient orbital/spin current source for antiferromagnetic spintronics.Comment: 19 pages, 4 figure