Umklapp scattering at reconstructed quantum Hall edges

We study the low-lying excitations of a quantum Hall sample that has undergone edge reconstruction such that there exist three branches of chiral edge excitations. Among the interaction processes that involve electrons close to the three Fermi points is a new type of Umklapp-scattering process which has not been discussed before. Using bosonization and a refermionization technique, we obtain exact results for electronic correlation functions and discuss the effect Umklapp scattering has on the Luttinger-liquid properties of quantum Hall edges.     

边临界图的新下界

图$G$ 为简单的第二类连通图, 且对$G$ 的任意边$e$,有$\chi^{\prime}(G-e)<\chi^{\prime}(G)$, 则称 $G$是临界的.该文给出了阶为$n$ 边数为$m$的$\Delta$ -临界图的新下界, 即$m\geq(3\Delta+6)n/10$, 这里$1\leq\Delta\leq18$     

Spin dependent electronic transport properties of zigzag black phosphorene nanojunctions induced by H,Li, O,Co asymmetric edge saturations

Two-dimensional (2D) material of few-layer black phosphorus (BP) has recently attracted extensive interest owing to its tunable band gap and high carrier mobility. We investigate the electronic transport properties of zigzag black phosphorene nanoribbons (ZBPNRs) with asymmetric H, Li, O and Co edge saturations by employing the density functional theory in combination with the non-equilibrium Green's function. The computational results forecast that different types of saturated atoms at both edge of ribbons mainly contribute to the electronic transport properties of molecular junctions. The metal edge saturation of Co atom is used to the one edge of ZBPNR which can induce an identical electronic transport property. Interestingly, the negative differential resistance (NDR) phenomena can be observed in our proposed ZBPNR junctions with an analysis of internal physical mechanism. Our theoretical results could support the possibility of potential applications to design 2D electronic devices based on the material of BP in future.     

Magnetic and electronic properties of zigzag BN nanoribbons with nonmetallic atom terminations: A first-principles study

The boron nitride (BN) nanosheet is an isostructural analog of graphene and can be viewed as the structure that C atoms in graphene are replaced with alternating B and N. The easily modulated band-gap of BN nanosheet by simply passivating its edge(s) makes it is promising for many potential applications in nanodevices and nanoelectronics. We further systematically theoretically study the magnetic and electronic properties of passivated-ZBNNR by nonmetallic atom(s), here. According to our calculations, all considered structures show magnetic feature, and the ZBNNRs can be metal or half-metal or semiconductor depending on the termination details. The great application-potential of the passivated-ZBNNRs is further confirmed based on our results.     

Photodynamic Effect of Riboflavin on Chitosan Coatings and the Application in Pork Preservation

Riboflavin (RF) was considered to be possessed of photoactivity to generate reactive oxygen species (ROS) under ultraviolet (UV) light, which is thought to be a favorable antibacterial candidate. Herein, RF was incorporated into chitosan (CS) coatings and treated under UV with different exposure times (2, 4, and 6 h) to improve the physicochemical and antibacterial properties. The results showed that the light transmittance and antibacterial performance of chitosan coatings gradually increased with the extension of the UV irradiation time. The antibacterial ability of chitosan coatings correlated with the generation of ROS: ∙OH and H₂O₂, which achieved 1549.08 and 95.48 μg/g, respectively, after 6 h irradiation. Furthermore, the chitosan coatings with UV irradiation also reduced the pH value, total volatile basic nitrogen (TVB-N), ΔE, and total viable counts (TVC) and improved sensory attributes of pork. In conclusion, the UV irradiated chitosan coatings could be used as an environmentally friendly antimicrobial packaging material to effectively delay the spoilage of pork, maintain its sensory quality and prolong its shelf life.     

An efficient task allocation framework for scheduled data in edge based Internet of Things using hybrid optimization algorithm approach

Allocation of tasks in IoT is an integral and critical approach to finding a perfect match between scheduled tasks of a particular application and Edge-based processing devices for instant response and efficient utilization of resources to make them renewable. We need a protocol to help optimize the problem of allocating processing devices to the tasks, as task allocation is considered an NP-hard problem to prevent problems with energy consumption and response time problems. For this, a hybrid bio-inspired Swarm-based approach will improve the solution to optimize the matching of a task to a particular device. This paper proposed a Meta-heuristic algorithm to optimize Energy and Time-delay for allocating tasks to the edge-based Processing device in IoT. The proposed algorithm called the Hybrid Artificial Bee Colony whales Optimization algorithm (HAWO) is formulated by integrating Artificial Bee Colony with the Whales Optimization algorithm to overcome the search process of an Artificial Bee Colony, which converges too soon due to the local search of Employee Bee phase and Onlooker Bee phase causing the problem of looping. From the simulation results conducted in Matlab, it is observed that the integrated HAWO method shows promising results in terms of Energy and Time Delay when compared with Artificial Bee Colony and Whales Optimization algorithms separately. Also, proposed method when compared with the benchmark work shows significant improvements of 50%, 25% and 60% in terms of Energy, Time Delay and Best cost, respectively.     

A Crowning Achievement: The First Solution-Phase Synthesis of Circumcoronenes

Circumcoronene is a highly symmetric polybenzenoid hydrocarbon that has fascinated organic chemists and materials scientists for decades. However, until recently, it had only been studied theoretically, because its synthesis in solution remained challenging. In a recent report, Wu and co-workers described the first successful solution-phase synthesis and isolation of crystalline circumcoronene derivatives, validating the long-predicted Clar structure. Their synthetic approach enables preparation of new polycyclic benzenoid hydrocarbons with multiple K-regions, which are difficult to obtain, and expands our understanding of the chemistry of these systems.     

Circumcoronenes

Circumcoronene, a hexagonal graphene fragment with six zigzag edges, has been the focus of theoretical studies for many years, but its synthesis in solution has remained a challenge. In this study, we present a facile method for synthesizing three derivatives of circumcoronene using Brønsted/Lewis acid-mediated cyclization of vinyl ether or alkyne. Their structures were confirmed through X-ray crystallographic analysis. Bond length analysis, NMR measurement, and theoretical calculations showed that circumcoronene mostly follows Clar's bonding model and exhibits dominant local aromaticity. Its absorption and emission spectra are similar to those of the smaller hexagonal coronene due to its six-fold symmetry.