A superionic state in nano-porous double-layer capacitors: insights from Monte Carlo simulations

Recently observed anomalous properties of ionic-liquid-based nanoporous supercapacitors [C. Largot et al., J. Am. Chem. Soc., 2008, 130, 2730-2731] have attracted much attention. Here we present Monte Carlo simulations of a model ionic liquid in slit-like metallic nanopores. We show that exponential screening of the electrostatic interactions of ions inside a pore, as well as the image-charge attraction of ions to the pore surface, lead to the 'anomalous' increase of the capacitance with decreasing the pore width. The simulation results are in good agreement with the experimental data. The capacitance as a function of voltage is almost constant for low voltages and vanishes above a certain threshold voltage. For very narrow pores, these two regions are separated by a peak. With increase of the pore size the peak turns into a bump and disappears for wide pores. This effect, related to a specific character of the voltage-induced filling of nanopores with counterions at high densities, is yet to be verified experimentally.     

Electrowetting with electrolytes

A theory of electrowetting is developed for systems containing an interface between two immiscible electrolytic solutions. Laws for the dependence of contact angle on electrode potential are presented. Ionic impermeability of the liquid-liquid interface and nonlinear double-layer responses rationalize observed phenomena such as contact-angle saturation and droplet contraction or detachment. The theoretical results can be applied to design new, precisely controllable microfluidic devices.     

Direct one-index transformations in multiconfiguration response calculations

The evaluation of gradient vectors of a general operator with one-index, double-one-index, or higher-order one-index transformed integrals is a key operation in multiconfiguration response theory calculations. We describe an integral-driven direct algorithm that carries out this operation efficiently without pretransforming the integrals. The use of this algorithm leads to a considerable reduction in disk space and timing. © 1994 by John Wiley & Sons, Inc.     

Statistical mechanics of columnar DNA assemblies

Many physical systems can be mapped onto solved or solvable models of magnetism. In this work, we have mapped the statistical mechanics of columnar phases of ideally helical rigid DNA --subject to the earlier found unusual, frustrated pair potential (A.A. Kornyshev, S. Leikin, J. Chem. Phys. 107, 3656 (1997))-- onto an exotic, unknown variant of the XY model on a fixed or restructurable lattice. Here, the role of the spin is played by the azimuthal orientation of the molecules. We have solved this model using a Hartree-Fock approximation, ground-state calculations, and finite-temperature Monte Carlo simulations. We have found peculiar spin order transitions, which may also be accompanied by positional restructuring, from hexagonal to rhombohedric lattices. Some of these have been experimentally observed in dense columnar aggregates. Note that DNA columnar phases are of great interest in biophysical research, not only because they are a useful in vitro tool for the study of DNA condensation, but also since these structures have been detected in living matter. Within the approximations made, our study provides insight into the statistical mechanics of these systems.     

Design,synthesis of novel quinazolin-4-one derivatives and biological evaluation against human MCF-7 breast cancer cell line

A new series of 6,8-dibromo-2-(4-chlorophenyl)quinazolin-4(3H)-one derivatives VI–XIII were synthesized. Their chemical structures were confirmed by spectral and elemental analysis. The cytotoxic effect of the newly synthesized compounds was tested in vitro against human breast cancer cell line (MCF-7). Most of the tested compounds have shown promising cytotoxic activity. Compounds X and XIIIb exerted a powerful cytotoxic effect against MCF-7 with a very low IC50 (0.0015 and 0.0047 µmol/ml), while compounds VI, VII, VIII, XIIb, XI, XIIIc and IX exerted a moderate cytotoxic effect (IC50 0.01523, 0.0213, 0.031, 0.0478, 0.049, 0.068 and 0.079 µmol/ml respectively), compared to doxorubicin (0.0025 µmol/ml). Exploring their apoptotic effect; interestingly,all compounds activated apoptotic cascade in MCF-7. Compounds VI, XIIIb, XIIb, XI, XIIa, VII, V and VIII showed potent effect even much more than doxorubicin by 12.87–5.91 folds, while compounds XIIIc, IX, XIIIa, XIIc and X showed moderate increase in CASP3 activity by 4.96–3.22 folds relative to untreated cells more or less similar to doxorubicin (5.57 folds).     

Ultra-low-frequency dust-electromagnetic modes in self-gravitating magnetized dusty plasmas

Obliquely propagating altra-low-frequency dust-electromagnetic waves in a self-gravitating, warm, magnetized, two fluid dusty plasma system have been investigated. Two special cases, namely, dust-Alfvén mode propagating parallel to the external magnetic field and dustmagnetosonic mode propagating perpendicular to the external magnetic field have also been considered. It has been shown that effects of self-gravitational field, dust fluid temperature, and obliqueness significantly modify the dispersion properties of these ultra-low-frequency dust-electromagnetic modes. It is also found that in parallel propagating dust-Alfvén mode these effects play no role, but in obliquely propagating dust-Alfvén mode or perpendicular propagating dust-magnetosonic mode the effect of self-gravitational field plays destabilizing role whereas the effect of dust/ion fluid temperature plays stabilizing role.     

Reflection of light by metal nanoparticles at electrodes

We present model calculations for the reflection spectrum of an ordered two dimensional array of metallic nanoparticles located near an electrochemical interface. We consider three cases, nanoparticles at: (i) a metal electrode, (ii) a transparent semiconductor electrode, and (iii) an electrified liquid/liquid interface. In the case of a metal electrode, the presence of nanoparticles introduces dips in reflection, whose position and depth are affected by the distance and size of the nanoparticles. For both a transparent semiconductor electrode and a liquid/liquid interface, the presence of nanoparticles enhances reflectivity. The spectra are sensitive to the particle spacing and size. The response from all three systems exhibits a strong dependence on the polarisation of light. The dependence on the angle of incidence reveals shallow dips typical of surface plasmon resonance spectra. These findings suggest diagnostic tools for the detection and characterisation of nanoparticle monolayers on functionalised electrodes, and enable electrovariable optical devices based on the controlled assembly of nanoparticles at interfaces.     

On the physical nature of mesophases of guanosine gels

The unusual columnar aqueous mesophases of self-assembled guanosine stacks, such as 2'-deoxyguanosine 5'-monophosphate and 2'-deoxyguanosine 3'-monophosphate, are analyzed in terms of a general theory of azimuthal correlations between the charged helices. This theory considers forces, specific to the helical structure of each macromolecule, which depend on the azimuthal orientations of the molecules about their long axes. More specifically, in determining the magnitudes and decay lengths of these helix specific forces we utilize the Kornyshev-Leikin theory of electrostatic interaction between helical macromolecules and quantitatively fit experimental data. Together with explaining a number of the observed features of these mesophases, several new effects are predicted. Possible limitations and developments of our theoretical model are discussed, as well as new experiments to test the implications of the theory.