Nonlinear optical and structural properties of M@C N endohedrals (M = Li,Ca and Sc,N = 60 and 70)

We have investigated the static (ω = 0) and frequency-dependent nonlinear optical (NLO) properties of the M@C _N endohedrals (M = Li, Ca, Sc, N = 60 and 70) using the SSH (Su–Schrieffer–Heeger) approximation and sum-over-state (SOS) approach. Also, we study the effects of displacement and alkali, alkaline earth and lanthanide metal atoms and type of cage on the hyperpolarisabilities of the M@C _N endohedrals. The hyperpolarisability magnitudes and spectra are in agreement with experiment and the work of others using the SSH approximation. Our results indicate that the cage-type effect on the NLO spectra of M@C _N endohedrals is dramatic. Also, atom type has little effect on the highest peak value. These relationships between the atom and cage type and hyperpolarisability values may be beneficial to experimentalists when designing new NLO materials with large NLO responses.     

Improved photonic crystal directional coupler with short length

We investigate a photonic crystal (PC) waveguide coupler which is formed by two closely spaced linear waveguides in a two-dimensional triangular lattice of air holes. Our study shows that shifting one row of the air holes between the waveguides affects the dispersion curves of the guided modes and if the triangular lattice of air holes between the waveguides is replaced by a rectangular lattice, this modification results in an ultra-short coupling structure with coupling length less than 3a, where a is the lattice constant. Also, we investigate the effect of changing the radii of air holes that are adjacent to or between the waveguides on the coupling length and show that increasing the radius of air holes between the waveguides decreases the coupling length. We analyze the output spectrum of an ultra-short channel drop filter designed based on this structure.     

Heavy Charged Gauge Bosons with General CP Violating Couplings

Heavy gauge bosons such as W＇ are expected to exist in many extensions of the Standard Model. In this paper, the most general Lagrangian for the interaction of W＇ with top and bottom quarks is considered. This Lagrangian consists of V- A and V ＋ A structure with in general complex couplings. Such interactions produce an Electric Dipole Moment （EDM） for the top quark at one loop level. We predict the allowed ranges for the mass and couplings of W＇ by using the upper limit on the top quark EDM.     

On the performance of density functional schemes for computing the static dipole polarizability of 4d transition-metal monohalides

This article presents the static dipole polarizabilities of 4d transition-metal monohalides in the framework of density functional theory. The behavior of a large number of density functionals, including various types of the local spin density approximation (LSDA), the generalized gradient approximation (GGA), meta GGA (MGGA), hybrid GGA (HGGA), and hybrid meta GGA (HMGGA), has been assessed in polarizability calculations. The highly accurate CCSD(T) methodology is used to benchmark a variety of functionals. Our results indicate that there is a large variation in performance of the various functionals of each type in the calculation of the dipole polarizability. It turned out that, in the LSDA class, SVWN5 gives better results than SVWN3 for the reference values. Of the GGA methods, BP86 and BPW91 give the best results for our data set, followed by G96LYP. The TPSS functional is the best method of the MGGA class, followed by the VSXC and BB95 functionals. Moreover, the B98 and mPW1PW91 functionals are the best methods of the HGGA lineage, predicting the most accurate static dipole polarizabilities. Finally, TPSS1KCIS and PBE1KCIS are the best methods of the HMGGA functionals for that purpose. In general, it was found that the HGGA and HMGGA functionals provide the best performance.     

Enhancing optomechanical force sensing via precooling and quantum noise cancellation

We theoretically investigate optomechanical force sensing via precooling and quantum noise cancellation in two coupled cavity optomechanical systems.We show that force sensing based on the reduction of noise can be used to dramatically enhance the force sensing and that the precooling process can eifectively improve the quantum noise cancellation.Specifically,we examine the effect of optomechanical cooling and noise reduction on the spectral density of the noise of the force measurement;these processes can significantly enhance the performance of optomechanical force sensing,and setting up the system in the resolved sideband regime can lead to an optimization of the cooling processes in a hybrid system.Such a scheme serves as a promising platform for quantum back-action-evading measurements of the motion and a framework for an optomechanical force sensor.     

Measuring the radon concentration and investigating the mechanism of decline prior an earthquake (Jooshan, SE of Iran)

Batch equilibrium studies were conducted at 20 ± 0.5 °C with indigenously synthesized spherical resorcinol–formaldehyde resin beads, using radioanalytical technique, to determine their capacity for sorption of cesium ions from alkaline medium. Equilibrium isotherm studies were carried out, by varying the initial concentrations of cesium from 0.1 to 50 mM. The liquid-to-solid phase ratio of ~100 ml:1 g was maintained for all the sorption experiments. The equilibrium data were fitted to Langmuir and Freundlich isotherm models. It was observed that Freundlich isotherm explains sorption process nicely. The effect of resin size on percentage cesium ion uptake was also investigated, and 20–40 mesh size was found to be the optimum particle size. The cesium sorption capacity of the beads was determined to be ~238 mg/g. The kinetics of the sorption was studied at different initial cesium ion concentrations, and the kinetics data were fitted into various kinetics models. The kinetics of the cesium ion sorption was found to be pseudo second-order. The mechanistic steps involved were found to be complex, consisting of both film diffusion and intraparticle diffusion with film diffusion as the rate limiting step.     

Preparation and characterization of gamma irradiated ZnO/PANI hybrid films

Journal of Radioanalytical and Nuclear Chemistry - In this study, Zinc Oxide/Polyaniline (ZnO/PANI) hybrid was successfully synthesized using the combination of in-situ chemical oxidative...     

One-pot synthesis of new hydantoin (thiohydantoin) derivatives and evaluation of their antibacterial and antioxidant activities

One-pot four-component reactions of phenacyl bromides, parabanic or thioparabanic acids, thiophenols, and triphenylphosphine in the presence of triethylamine afforded new derivatives of hydantoin or thiohydantoin in good to high yields (65%-90%). Their antibacterial activities were evaluated against two Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). Among the synthesized compounds, the obtained products from 2-hydroxythiophenol exhibited higher antibacterial activity than those obtained from 2-aminothiophenol. Compound 9l including N,N′^′-diphenyl thiohydantoin moiety showed the highest antibacterial activity (26.0 ± 01.4) against B subtilis, in comparison with other synthesized samples. The antioxidant activities of the synthesized hydantoins and thiohydantoins were investigated by DPPH radical-scavenging based on Blois method. The results showed that all the compounds have high DPPH inhibition potency (77.4%-83.9%) that it could be due to existence of heteroatoms with lone pair electrons and exchangeable protons on their NH₂ and OH groups.     

Copper chromite decorated on nitrogen-doped graphene aerogel as an efficient catalyst for thermal decomposition of ammonium perchlorate particles

Journal of Thermal Analysis and Calorimetry - The present study reports numerical simulations of water-based Al2O3 nanofluid flowing in a 2D channel with a heated wall-mounted obstacle. The...