On-Shell Gauge Invariant Three-Point Amplitudes

Assuming locality, Lorentz invariance and parity conservation we obtain a set of differential equations governing the 3-point interactions of massless bosons, which in turn determines the polynomial ring of these amplitudes. We derive all possible 3-point interactions for tensor fields with polarisations that have total symmetry and mixed symmetry under permutations of Lorentz indices. Constraints on the existence of gauge-invariant cubic vertices for totally symmetric fields are obtained in general spacetime dimensions and are compared with existing results obtained in the covariant and light-cone approaches. Expressing our results in spinor helicity formalism we reproduce the perhaps mysterious mismatch between the covariant approach and the light cone approach in 4 dimensions. Our analysis also shows that there exists a mismatch, in the 3-point gauge invariant amplitudes corresponding to cubic self-interactions, between a scalar field $\phi$ and an antisymmetric rank-2 tensor field $A_{\mu\nu}$. Despite the well-known fact that in 4 dimensions rank-2 anti-symmetric fields are dual to scalar fields in free theories, such duality does not extend to interacting theories.Comment: significantly revised, final version published in JHE

Supercapacitor Performance of Nickel-Cobalt Sulfide Nanotubes Decorated Using Ni Co-Layered Double Hydroxide Nanosheets Grown in Situ on Ni Foam

In this study, to fabricate a non-binder electrode, we grew nickel-cobalt sulfide (NCS) nanotubes (NTs) on a Ni foam substrate using a hydrothermal method through a two-step approach, namely in situ growth and an anion-exchange reaction. This was followed by the electrodeposition of double-layered nickel-cobalt hydroxide (NCOH) over a nanotube-coated substrate to fabricate NCOH core-shell nanotubes. The final product is called NCS@NCOH herein. Structural and morphological analyses of the synthesized electrode materials were conducted via SEM and XRD. Different electrodeposition times were selected, including 10, 20, 40, and 80 s. The results indicate that the NCSNTs electrodeposited with NCOH nanosheets for 40 s have the highest specific capacitance (SC), cycling stability (2105 Fg-1 at a current density of 2 Ag-1), and capacitance retention (65.1% after 3,000 cycles), in comparison with those electrodeposited for 10, 20, and 80 s. Furthermore, for practical applications, a device with negative and positive electrodes made of active carbon and NCS@NCOH was fabricated, achieving a high-energy density of 23.73 Whkg-1 at a power density of 400 Wkg-1

Carbon nanotube@manganese oxide nanosheet core-shell structure encapsulated within reduced graphene oxide film for flexible all-solid-state asymmetric supercapacitors

To achieve flexible energy storage devices with high performance, a new class of flexible electrodes with exquisite architectures that provide well-defined pathways for efficient ionic and electronic transport is highly needed. A flexible 3D electrode is fabricated based on assembling 1D carbon nanotube@manganese oxide (MnO2) nanosheet core-shell structures (CM) with 2D reduced graphene oxide (rGO) nanosheets. MnO2 nanosheets are grafted vertically along the carbon nanotube backbone through a secondary (seeded) growth. Flexible hybrid films (GCM) composed of CM and rGO are prepared by vacuum filtration of the mixed dispersions of both components assisted by electrostatic interactions. By adopting this ternary hybrid architecture, the GCM electrode exhibits exceptional charge storage capability in 1 M Na2SO4 aqueous electrolyte with high specific capacitance (298 F g−1 at 0.5 A g−1), good rate capability, and high cycling stability (90.3% retention over 5000 cycles). A highly flexible all-solid-state asymmetrical supercapacitor is assembled with GCM as the positive electrode and holey graphene film spaced with carbon sphere (H-GCS) as the negative electrode. GCM//H-GCS asymmetric supercapacitor delivers a maximum energy density of 24.6 Wh kg−1 and a power density of 9005.3 W kg−1 with excellent cycle life of 75.9% retention after 10 000 cycles

Epidemiology and management of epilepsy in Hong Kong: an overview

AbstractOver half of the estimated 50 million people with epilepsy live in Asia, but there has been limited information on the epidemiology, aetiology and management of epilepsy from this region. In this article, we summarise some of the main problems faced by patients and the current treatment options available in an urban area of China