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We theoretically investigate multifrequency cloak based on multishell by using transformation medium. As for each shell, we use the Maxwell–Garnett theory and the spectral representation theory to design the permittivity profile for the transverse magnetic wave. The plasma frequencies of the metals used in the inner (B) and outer (C) shells must satisfy ω1<ωpC<ω2<ωpB. In such case, incident electromagnetic wave of lower frequency ω1 will be distorted only by the outer shell C without entering the inner shell B to achieve invisibility. However, at the higher operating frequency ω2, the outer shell C is transparent by choosing the materials appropriately, and the incident electromagnetic wave will be distorted only by the inner shell B to achieve invisibility. So, the multishell cloak can work simultaneously on two different optical frequencies. Furthermore, we use the anisotropic differential effective dipole theory to evaluate the efficiency of the cylindrical cloak. [ABSTRACT FROM AUTHOR]

We apply a Langevin model to investigate the nonlinear ac responses of electro-magnetorheological (ERMR) fluids under the application of two crossed dc magnetic (z axis) and electric (x axis) fields and a probing ac sinusoidal magnetic field. We focus on the influence of the magnetic fields which can yield nonlinear behaviors inside the system due to the particles with a permanent magnetic dipole moment. Based on a perturbation approach, we extract the harmonics of the magnetic field and orientational magnetization analytically. To this end, we find that the harmonics are sensitive to the degree of anisotropy of the structure as well as the field frequency. Thus, it is possible to real-time-monitor the structure transformation of ERMR fluids by detecting the nonlinear ac responses. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A theoretical study of the dielectrophoretic (DEP) spectrum of a pair of touching colloidal particles or biological cells in a host fluid under the application of a nonuniform alternating current (ac) electric field is presented. The main objective of this work is to investigate the correlation effects due to the presence of mutual polarization on the DEP spectrum. In particular, we employ the multiple image method to account for the effect of multiple images, and obtain an analytic expression for the DEP force. It is found that, at low frequencies, the DEP force can be enhanced (reduced) significantly for the longitudinal (transverse) field case due to the presence of multiple images. The numerical results can be well understood in the spectral representation theory. To first order in the dipole interaction, our results reduce to the established formula derived by an alternative method. Our approach demonstrates the importance of the correlation effects in ac electrokinetic phenomena of colloidal suspensions. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have fabricated a class of colloidal electrorheological (ER) fluids, in which suspended TiO2 particles were synthesized by a sol-gel method and modified by 1,4-butyrolactone molecules with a permanent molecular dipole moment of 4.524 D. Compared with pure TiO2 ER fluids, the quasi-static yield stress of the polar- molecules-modified ER fluid is enhanced as high as 48.1 kPa when subjected to an external electric field of 5 kV/mm. Also, it possesses other attractive characters such as low current density (<14 µA/cm2) and low sedimentation. Based on a Green's function method, we present a first-principles approach to investigate colloidal electrostatic interactions. Excellent agreement between experiment and theory has been shown for the enhancement ratio of quasi-static yield stress, which quantitatively reveals that enough polar molecules oriented within the field-directed gap between the colloidal particles can unexpectedly enhance the interactions, thus yielding the unusual enhancement. This shows a promising and flexible direction for achieving more highly active ER materials. [ABSTRACT FROM AUTHOR]

The key to realizing fault‐tolerant quantum computation for singlet‐triplet (ST) qubits in semiconductor double quantum dot (DQD) is to operate both the single‐ and two‐qubit gates with high fidelity. The feasible way includes operating the qubit near the transverse sweet spot (TSS) to reduce the leading order of the noise, as well as adopting the proper pulse sequences which are immune to noise. The single‐qubit gates can be achieved by introducing an AC drive on the detuning near the TSS. The large dipole moment of the DQDs at the TSS has enabled strong coupling between the qubits and the cavity resonator, which leads to two‐qubit entangling gates. When operating in the proper region and applying modest pulse sequences, both single‐ and two‐qubit gates have fidelity higher than 99%. The results in this paper suggest that taking advantage of the appropriate pulse sequences near the TSS can be effective to obtain high‐fidelity ST qubits. [ABSTRACT FROM AUTHOR]

Two new isostructural coordination compounds of cobalt(II) and zinc(II) involving 1,10-phenanthroline and 2,5-pyridine dicarboxylate, viz., [Co(2,5-PDC)(phen)2]·9H2O (1) and [Zn(2,5-PDC)(phen)2]·9H2O (2) (in which, PDC = pyridine dicarboxylate, phen = 1,10-phenanthroline) have been synthesized and characterised using FT-IR, electronic spectroscopy, thermal analysis, elemental analysis and single crystal X-ray diffraction techniques. Crystal structure analysis reveals that the neighboring monomeric units of 1 and 2 are self-assembled via π-stacking, C–H⋯π and C–H⋯O interactions. Fascinating and unusual discrete (H2O)21 clusters in 2 stabilize the network architecture. The self-assembled enclathration of water clusters in the hexameric supramolecular host cavity of 1 provides additional reinforcement to the crystal structure. The strength of the biologically relevant cooperative π-stacking interactions for 1 and 2 has been investigated using DFT calculations and analyzed using an NCI plot index. Remarkably, the (π–π)1 binding modes in the ternary π-stacked assemblies are energetically more significant than the (π–π)2 mode due to the contribution of the two symmetrically related C–H⋯O interactions. The large and almost identical dipole moments of the compounds nullify the influence of the metal centers on the strength of the cooperative π-stacked assemblies, and this corroborates the strong binding energies. The compounds significantly induce concentration dependent cell cytotoxicity and apoptosis in DL cancer cells with negligible cytotoxicity in normal cells. The molecular docking study and pharmacophore features establish the structure activity relationship (SAR) of the compounds. [ABSTRACT FROM AUTHOR]

We report video microscopy measurements and computer simulations of quasi-two-dimensional configurations of micron sized colloids in 1 MHz ac electric fields between coplanar thin film electrodes. Interactions of induced dipoles (IDs) with each other and inhomogeneous electric fields (IFs) as a function of concentration and field amplitude produced microstructures including confined hard disk fluids, oriented dipolar chains, and oriented hexagonal close packed crystals. Equilibrium measurements and analyses of single colloids within electric fields were used to directly measure ID-IF interactions in the absence of many body effects. Measurements of concentrated systems were characterized in terms of density profiles across the electrode gap and angular pair distribution functions. In concentrated measurements, an inverse Monte Carlo analysis was used to extract the ID-ID interaction. A single adjustable parameter consistently modified the ID-IF potential and the ID-ID potential to account for weakening of ID as the result of the local particle concentration and configuration. [ABSTRACT FROM AUTHOR]

Electric force is the most popular technique for bioparticle transportation and manipulation in microfluidic systems. In this paper, the iterative dipole moment (IDM) method was used to calculate the dielectrophoretic (DEP) forces of particle-particle interactions in a two-dimensional DC electric field, and the Lagrangian method was used to solve the transportation of particles. It was found that the DEP properties and whether the connection line between initial positions of particles perpendicular or parallel to the electric field greatly affect the chain patterns. In addition, the dependence of the DEP particle interaction upon the particle diameters, initial particle positions, and the DEP properties have been studied in detail. The conclusions are advantageous in elelctrokinetic microfluidic systems where it may be desirable to control, manipulate, and assemble bioparticles. [ABSTRACT FROM AUTHOR]

The properties of 4-(benzyloxy)benzaldehyde (BBA), as a pharmaceutically important compound, have been investigated through the density functional theory (DFT) calculations. The properties of original crystalline and optimised gaseous structures have been evaluated to recognise the crystalline effects. In addition to the structural properties, nuclear magnetic resonance (NMR) properties have also been evaluated for both investigated systems to better detect the effects in atomic levels. The results indicated that the structural shape of BBA is significantly changed in the optimised gaseous system, showing significant crystalline effects on the geometrical positions. Moreover, the magnitudes for energies and dipole moments indicate notable effects on the electronic properties. The evaluated NMR properties also show that the atoms of aromatic systems detect significant changes more than the atoms of aliphatic systems in the investigated BBA. And finally, the oxygen bridge atom plays a dominant role in combining two benzene rings of BBA. [ABSTRACT FROM AUTHOR]