Dielectric response and intraband plasmon dispersion in stage-1 FeCl3 intercalated graphite

A theory of the frequency and wavevector dependent longitudinal dielectric response functions in stage-1 FeCl₃-intercalated-graphite is developed from a two-band model for the graphite π electrons. The theory predicts the observed wavevector dependence of the energy and intensity of the intraband plasmon induced by intercalation, and comparison with experiment provides a measurement of the degree of charge transfer in C_6.6FeCl₃.     

Electronic states near the band gap for the GaAs(110) surface

The recent theoretical controversy regarding empty surface states at the GaAs cleavage plane is examined by the exact solution of several tight binding models applied to a semi-infinite crystal. We correlate the existence of an empty surface gap state with the anion p/cation p character of this state. This work isolates the specific properties of a Hamiltonian for GaAs which yield band gap states on a relaxed surface and clarifies the essential differences among current theoretical treatments.     

Electric polarization of heteropolar nanotubes as a geometric phase

The threefold symmetry of planar boron nitride (BN), the III-V analog to graphene, prohibits an electric polarization in its ground state, but this symmetry is broken when the sheet is wrapped to form a BN nanotube. We show that this leads to an electric polarization along the nanotube axis which is controlled by the quantum mechanical boundary conditions on its electronic states around the tube circumference. Thus the macroscopic dipole moment has an intrinsically nonlocal quantum mechanical origin from the wrapped dimension. We formulate this novel phenomenon using the Berry's phase approach and discuss its experimental consequences.     

Sneutrino–Higgs mixing in WW and ZZ production in supersymmetry with R-parity violation

We consider new s-channel scalar exchanges in e⁺e⁻→ZZ, W⁺W⁻ in supersymmetry with a small lepton number violation. We show that a small bilinear R-parity violating term which leads to sneutrino–Higgs mixing can give rise to a significant scalar resonance enhancement in e⁺e⁻→ZZ, W⁺W⁻. We use the LEP2 measurements of the WW and ZZ cross-sections to place useful constraints on this scenario. We also find, under conservative assumptions on the relevant parameter space involved, that such an exchange of the sneutrino-like admixture in e⁺e⁻→ZZ, W⁺W⁻ may be accessible to a 500 GeV e⁺e⁻ collider.     

Methylprednisolone release from agar-Carbomer-based hydrogel: a promising tool for local drug delivery

A number of studies and works in drug delivery literature are focused on the understanding and modelling of transport phenomena, the pivotal point of a good scaffold design for tissue engineering. Accurate knowledge of the diffusion coefficient of an active drug plays a key role in the analysis, prediction of their kinetics and formulation of efficient drug delivery systems. In this work, the kinetics of the release of methylprednisolone from agar-Carbomer hydrogel were studied taking into consideration the different drug concentrations and clearances typically achieved in in vitro or in vivo tests. Starting from the experiments it is possible to model the transport phenomenon and to calculate the diffusion coefficient through the hydrogel matrix.     

Influence of the processing solvent on the photoactive layer nanomorphology of P3HT/PC60BM solar cells

In this article, it is demonstrated that doctor blading of thin poly‐3‐hexylthiophene/phenyl‐C₆₁‐butyric acid methyl ester (1/1) bulk‐hetero junction films from toluene leads to an improved nanocrystallinity, when compared with their unannealed chlorobenzene processed counterparts. This difference in morphology was demonstrated by solid‐state NMR and Rapid Heating Cooling Calorimetry (RHC), being useful complementary techniques to investigate the active layer morphology of photovoltaic devices. An increased PC₆₀BM nanocrystallinity is indicated by several NMR relaxation decay times (T_1C, T_1H, and T_1ρH) and confirmed by an increase of the melting enthalpy in RHC experiments. An improved solar cell performance further strengthens this conclusion. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Regiospecific naphthyl nitration of 5,10,15,20‐tetranaphthylporphyrin

The nitration reaction of 5,10,15,20‐tetranaphthylporphyrin (TNP) was investigated in detail and the mono‐, di‐, and tri‐nitro‐TNPs were synthesized in high yield using 65% HNO₃. The ¹H‐NMR study shows that the preferred site of nitration of the naphthyl substituted porphyrin is the carbon atom of the meso‐substituents para to its bond to the porphyrin ring. The reaction leads to exquisite regioselectivity in favor of the mono, di, and tri‐nitro‐TNP. Quantum‐chemical ab initio calculations at different levels of theory were performed in order to explain the experimentally observed reactivity. Copyright © 2010 John Wiley & Sons, Ltd.