Modern Physics Letters B

Thioglycolic acid capped cadmium selenide (CdSe) and CdSe@ZnO core–shell quantum dots have been synthesized in aqueous phase. The sample was characterized by UV-vis spectrophotometer, TEM and Z-scan technique. The nonlinear optical parameters viz. nonlinear absorption coefficient $(\beta )$, nonlinear refractive index $(n_2)$ and third-order nonlinear susceptibilities $({\chi }^3)$ of quantum dots have been estimated using second harmonic of Nd:YAG laser. The study predicts that CdSe@ZnO quantum dots exhibits strong nonlinearity as compared to core CdSe quantum dots. The nonlinearity in quantum dots is attributed to the presence of resonant excitation and free optical processes. The presence of RSA in these nanoparticles makes them a potential material for the development of optical limiter.

In this study, Heusler alloy ${\mathrm{\text{Ni}}}_{50}{\mathrm{\text{Mn}}}_{37}{\mathrm{\text{Sb}}}_{13}$ has been prepared by solid state hybrid microwave heating within 40 min. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) analyses reveal that the obtained samples are of single phase cubic structure and homogeneous. Temperature-dependence of electrical resistivity and magnetization measurements confirm the austenite to martensitic transition of the first-order nature with the absence of the exchange bias (EB), which is verified by the magnetic hysteresis loops. Compared with the samples prepared by conventional arc-melting method, the sample synthesized by fast microwave heating has lower martensitic transition temperature, smooth magnetization change in the martensitic region and disappeared EB, implying strongly suppressed antiferromagnetic (AFM) interaction. These results suggest that tuning the microstructure via different synthesis method can influence significantly the martensitic transition and magnetic interactions in the Ni–Mn–Sb system.

Interconnections between networks make the traffic condition in interconnected networks more complicated than that in an isolated network. They make the load and capacity of nodes mismatch and restrict the traffic performance accordingly. To improve the performance, in this paper, we propose a hybrid routing strategy, which distinguishes the traffic within each individual network and the traffic across multiple networks and uses different routing rules for these two types of traffic. Simulation results show that this routing strategy can achieve better traffic performance than traditional strategies when networks are coupled by a small number of interconnected links, which is the case in most of real-world interconnected networks. Therefore, the proposed hybrid routing strategy can find applications in the planning and optimization of practical interconnected networks.

Impurities free ferromagnetic ${\mathrm{\text{Fe}}}_3{\mathrm{\text{O}}}_4$ was prepared via sol–gel auto-combustion method and then gold was doped with various concentrations 1, 3 and 5 wt.% using conventional deposition–precipitation method. All samples of ${\mathrm{\text{Fe}}}_3{\mathrm{\text{O}}}_4$ with/without Au doping were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The room temperature magnetic hysteresis loops of all the samples were measured using a physical property measuring system (PPMS), and the results showed a ferromagnetic behavior at room temperature. The results obtained confirmed the fabrication of magnetite–gold composite nanoparticles. The results showed that the resistance and the magnetic behavior of the samples decrease sharply with the increase of Au concentration indicating semiconducting behavior. The saturation magnetization $(M_s)$ of the bare ${\mathrm{\text{Fe}}}_3{\mathrm{\text{O}}}_4$ sample (94.72 emu/g) is much higher than that (66.78 emu/g) of the 5 wt.% Au-doped ${\mathrm{\text{Fe}}}_3{\mathrm{\text{O}}}_4$ sample.

In this paper, the silicon clathrate ${\mathrm{\text{Ba}}}_8{\mathrm{\text{Si}}}_{46}$ was successfully synthesized using low-cost antioxidative azide $\mathrm{\text{Ba}}{({\mathrm{\text{N}}}_3)}_2$ and Si as precursors by means of high pressure and high temperature (HPHT). The clathrate phase was one-step synthesized by high pressure chemical method within a short time. The reaction temperature and pressure were optimized to achieve good-quality crystalline products with a composition of ${\mathrm{\text{Ba}}}_{7.7}{\mathrm{\text{Si}}}_{46}$ and its transition temperature $(T_c)$ is about 8.3 K. The new preparation route presented in this paper provides an alternative to the multistep HPHT synthesis applied so far. One-step synthesis of type-I silicon clathrate ${\mathrm{\text{Ba}}}_8{\mathrm{\text{Si}}}_{46}$ by high pressure chemical method can shorten the synthesis period of time greatly.

In complex network analysis, the local community detection problem is getting more and more attention. Because of the difficulty to get complete information of the network, such as the World Wide Web, the local community detection has been proposed by researcher. That is, we can detect a community from a certain source vertex with limited knowledge of an entire graph. The previous methods of local community detection now are more or less inadequate in some places. In this paper, we have proposed a new local modularity metric $G$ and based on it, a two-phase algorithm is proposed. The method we have taken is a greedy addition algorithm which means adding vertices into the community until $G$ does not increase. Compared with the previous methods, when our method is calculating the modularity metric, the range of vertices what we considered may affect the quality of the community detection wider. The results of experiments show that whether in computer-generated random graph or in the real networks, our method can effectively solve the problem of the local community detection.

In this paper, long wavelength superluminal and subluminal properties of pulse propagation in a defect slab medium doped with four-level GaAs/AlGaAs multiple quantum wells (MQWs) with 15 periods of 17.5 nm GaAs wells and 15 nm ${\mathrm{\text{Al}}}_{0.3}{\mathrm{\text{Ga}}}_{0.7}\mathrm{\text{As}}$ barriers is theoretically discussed. It is shown that exciton spin relaxation (ESR) between excitonic states in MQWs can be used for controlling the superluminal and subluminal light transmissions and reflections at different wavelengths. We also show that reflection and transmission coefficients depend on the thickness of the slab for the resonance and nonresonance conditions. Moreover, we found that the ESR for nonresonance condition lead to superluminal light transmission and subluminal light reflection.

We quantify the prior information to infer the optimal characteristics for a constrained thermodynamic process of maximum work extraction for a pair of non-identical finite systems. The total entropy of the whole system remains conserved. The ignorance is assumed about the final temperatures of the finite systems and then a prior distribution is assigned to the unknown temperatures. We derive the estimates of efficiency for this reversible model of heat engine with incomplete information. The estimates show good agreement with efficiency at optimal work for arbitrary sizes of systems, however the estimates become exact when one of the reservoir becomes very large in comparison to the other.

A novel surface plasmon polaritons (SPPs) refractive index sensor based on a single defect nanocavity coupled with a metal–insulator–metal (MIM) waveguide is proposed and numerically simulated by using the finite difference time domain (FDTD) method with perfectly matched layer absorbing boundary condition. It is found that the defect structure can realize two Fano resonances and these two Fano resonances originate from two different mechanisms. The results demonstrate the liner correlation between the resonance wavelengths of the device and the refractive index of the material under sensing. Through the optimization of structural parameters, we achieve a theoretical value of the refractive index sensitivity as high as 1800.4 nmRIU${}^{-1}$. It could be utilized to develop ultra-compact nanodevice for high-resolution biological sensing.

In this paper, we alternatively study the evolution of squeezed vacuum state (SVS) in lossy channel by virtue of the phase space method. By using the formula of Wigner function (WF) in coherent representation and $P$ representation of quantum density operator, the WF formula in lossy channel is derived. After obtaining the analytical expressions of the WFs of the lossy SVS and the squeezed thermal state (STS), we further prove the fact that the lossy SVS is equivalent to a kind of STS. Our result is useful in dealing with the light field transmission problems in the presence of losses.