Massive Dirac fermions and spin physics in an ultrathin film of topological insulator

We study transport and optical properties of the surface states which lie in the bulk energy gap of a thin-film topological insulator. When the film thickness is comparable with the surface state decay length into the bulk, the tunneling between the top and bottom surfaces opens an energy gap and form two degenerate massive Dirac hyperbolas. Spin dependent physics emerges in the surface bands which are vastly different from the bulk behavior. These include the surface spin Hall effects, spin dependent orbital magnetic moment, and spin dependent optical transition selection rule which allows optical spin injection. We show a topological quantum phase transition where the Chern number of the surface bands changes when varying the thickness of the thin film.Comment: 7 pages, 5 figure

Bis[N′-(3-cyano­benzyl­idene)isonicotino­hydrazide-κN]silver(I) trifluoro­methane­sulfonate

In the title compound, [Ag(C14H10N4O)2]CF3SO3, two N atoms from two independent pyridyl rings of two N′-3-cyano­benzyl­ideneisonicotinohydrazide ligands coordinate to the unique AgI ion, forming a nearly linear coordination geometry. Adjacent silver complexes are primarily linked together by Ag⋯N inter­actions, with Ag⋯N separations of 2.877 (2) and 3.314 (2) Å. On the other hand, one CF3SO3 − anion inter­acts with hydrazone groups of two neighbouring ligands via N—H⋯O hydrogen bonds. These weak inter­molecular inter­actions contribute to the formation of supra­molecular chains. In addition, there are Ag⋯O inter­actions [2.787 (2) Å] between Ag and O atoms from adjacent chains

Doubly charmed baryon decays Ξcc++→Ξc(′)+π+\Xi_{cc}^{++}\to\Xi_c^{(\prime)+}\pi^+ in the quark model

In this work we study the doubly charmed baryon decays $\Xi_{cc}^{++}\to\Xi_c^{(\prime)+}\pi^+$ within the framework of the non-relativistic quark model (NRQM). Factorizable amplitudes are expressed in terms of transition form factors, while nonfactorizable amplitudes arising form the inner $W$-emission are evaluated using current algebra and the pole model and expressed in terms of baryonic matrix elements and axial-vector form factors. Nonperturbative parameters are then calculated using the NRQM. They can be expressed in terms of the momentum integrals of baryon wave functions, which are in turn expressed in terms of the harmonic oscillator parameters $\alpha_\rho$ and $\alpha_\lambda$ for $\rho$- and $\lambda$-mode excitation. The measured ratio $R$ of the branching fraction of $\Xi_{cc}^{++}\to \Xi^{\prime +}_c\pi^+$ relative to $\Xi_{cc}^{++}\to \Xi_c^+\pi^+$ can be accommodated in the NRQM with $\alpha_{\rho 1}$ and $\alpha_{\rho_2}$ being in the vicinity of 0.51 and 0.19, respectively, where $\alpha_{\rho 1}$ is the $\alpha_\rho$ parameter for $\Xi_{cc}^{++}$ and $\alpha_{\rho 2}$ for $\Xi_{c}^{(\prime)+}$. Decay asymmetries are predicted to be $-0.78$ and $-0.89$ for $\Xi_c^+\pi^+$ and $\Xi_c^{\prime +}\pi^+$ modes, respectively, which can be tested in the near future. We compare our results with other works and point out that although some other models can accommodate the ratio $R$, they tend to lead to a branching fraction of $\Xi_{cc}^{++}\to \Xi_c^+\pi^+$ too large compared to that inferred from the LHCb measurement of its rate relative to $\Xi_{cc}^{++}\to\Lambda_c^+ K^- \pi^+\pi^+$.Comment: 17 pages, 2 figure

Integrated Power Supply for MEMS Sensor

The recent expansion of wireless sensor networks and the rapid development of low-power consumption devices and MEMS devices have been driving research on harvester converting ambient energy into electricity to replace batteries that require costly maintenance. Harvesting energy from ambient environment vibration becomes an ideal power supply mode. The power supply module can be integrated with the MEMS sensor. There are many ways to convert ambient energy into electrical energy, such as photocells, thermocouples, vibration, and wind and so on. Among these energy-converting ways, the ambient vibration energy harvesting is more attractive because the vibration is everywhere in our daily environment. Based on the analysis of the basic theory of the electret electrostatic harvester, the basic equations and equivalent analysis model of electret electrostatic harvester are established. The experimental tests for the output performance of electret electrostatic harvester are completed. For the electret material, the material itself can also provide a constant voltage to avoid the use of additional power, which provides an effective way for electrostatic harvesting. Therefore, the electret electrostatic harvesting structure is a kind of ideal energy harvesting method using ambient vibration and can be easily integrated with the MEMS system

Protective effect of Acorus tatarinowii extract against alzheimer in 3xTg-AD mice

Purpose: To investigate the protective effect of Acorus tatarinowii extract (ATE) against Alzheimer's disease in 3xTg-AD mice. Method: The cognitive function of 3xTg-AD mice was assessed using Morris water maze test. The levels of the amyloid beta deposits and NeuN in the hippocampus were evaluated by immunohistochemical assay while brain neurotrophic derived factor (BDNF) and tyrosine kinase B (TrkB) expressions were determined by western blot analysis. Results: ATE treatment significantly ameliorated learning and memory deficits in AD mice, as shown by increased time spent in the target zone during probe tests. The escape latency in animals treated with 600 mg/kg ATE (24.8 ± 1.3 s) was significantly increased relative to ontreated 3xTg-AD mice (8.5 ± 1.0 s, p < 0.01). In addition, ATE significantly decreased Aβ deposits, increased NeuN-positive cells, and upregulated the expression of BDNF (1.9 ± 0.4, p < 0.05) and TrkB (1.9 ± 0.2, p < 0.05) in 3xTg AD mice. Conclusion: These results suggest that ATE treatment may be a useful strategy for managing memory impairment induced by several neurodegenerative diseases

Bis[N′-(3-cyano­benzyl­idene)isonicotino­hydrazide]silver(I) trifluoro­acetate

In the title compound, [Ag(C14H10N4O)2]CF3CO2, the AgI ion is coordinated by two N atoms of the pyridine rings of two N′-(3-cyano­benzyl­idene)isonicotinohydrazide ligands in a nearly linear geometry. In the crystal structure, a combination of close contacts formed via Ag⋯N inter­actions [Ag⋯N = 3.098 (2) and 3.261 (2) Å] from symmetry-related mol­ecules and inter­molecular N—H⋯O hydrogen bonds between CF3CO2 − anions and the hydrazone groups of two ligands give rise to chains. Furthermore, there are Ag⋯O inter­actions with a separation of 2.765 (2) Å between chains. The F atoms of the CF3CO2 − anion are disordered over two sites with refined occupancies of 0.593 (5) and 0.407 (5)

RNAi technology extends its reach: Engineering plant resistance against harmful eukaryotes

RNA interference (RNAi) is a homology-dependent gene silencing technology that is initiated by double stranded RNA (dsRNA). It has emerged as a genetic tool for engineering plants resistance against prokaryotic pathogens such as virus and bacteria. Recent studies broaden the role of RNAi, and many successful examples have described the application of RNAi for engineering plant resistance against a range of eukaryotic organisms. Expression of dsRNA directed against suitable eukaryotic pathogens target genes in transgenic plants has been shown to give protection against harmful eukaryotic species, including nematodes, herbivorous insects, parasitic weeds and fungi. This review addresses the progress of RNAi-based transgenic plant resistance against these four class eukaryotic pests, as well as future challenges and prospects.Key words: dsRNA, RNAi, crop resistance, biotechnology, nematode, insect, parasitic weed, fungus