Graphene and liquid crystal mediated interactions

ABSTRACT

The two-dimensional graphene-honeycomb structure can interact with the liquid crystal’s (LC) benzene rings through π–π electron stacking. This LC–graphene interaction gives rise to a number of interesting physical and optical phenomena in the LC. In this paper, we present a combination of a review and original research of the exploration of novel themes of LC ordering at the nanoscale graphene surface and its macroscopic effects on the LC’s nematic and smectic phases. We show that monolayer graphene films impose planar alignment on the LC, creating pseudo-nematic domains (PNDs) at the surface of graphene. In a graphene-nematic suspension, these PNDs enhance the orientational order parameter, exhibiting a giant enhancement in the dielectric anisotropy of the LC. These anisotropic domains interact with the external electric field, resulting in a non-zero dielectric anisotropy in the isotropic phase as well. We also show that graphene flakes in an LC reduce the free ion concentration in the nematic media by an ion-trapping process. The reduction of mobile ions in the LC is found to have subsequent impacts on the LC’s rotational viscosity, allowing the nematic director to respond quicker on switching the electric field on and off. In a ferroelectric LC (smectic-C* phase), suspended graphene flakes enhance the spontaneous polarisation by improving the tilted smectic-C* ordering resulting from the π–π electron stacking. This effect accelerates the ferroelectric-switching phenomenon. Graphene can possess strain chirality due to a soft shear mode. This surface chirality of graphene can be transmitted into LC molecules exhibiting two types of chiral signatures in the LCs: an electroclinic effect (a polar tilt of the LC director perpendicular to, and linear in, an applied electric field) in the smectic-A phase, and a macroscopic helical twist of the LC director in the nematic phase. Finally, we show that a graphene-based LC cell can be fabricated without using any aligning layers and ITO electrodes. Graphene itself can be used as the electrodes as well as the aligning layers, obtaining an electro-optic effect of the LC inside the cell.     

Proper orthogonal decomposition of the dynamics in bolted joints

Joints play an important role in the dissipation of vibration energy in built-up structures. The highly nonlinear nature of joints with micro-slip is the main hurdle in developing a reduced-order model which can simulate the dynamic behaviour of a joint for a wide range of excitation conditions and geometries. In this paper, the proper orthogonal decomposition is applied to joint dynamics in an attempt to arrive at a generic reduced-order model without a compromise on the physics of the system. Only the linear part of the system of equations is reduced. The nonlinear part is determined in the full space and then reduced before the numerical integration phase. The major reduction in computational time is achieved by the increase in the size of the stable time step and the reduced number of coordinates in the integration phase. The reduced-order model, which is derived for an isolated and harmonically excited joint, is successfully applied to separate joints with different geometries and excitation conditions, e.g. harmonic and impulsive. The model is also capable of simulating the dynamics of structures with joints. The results of the reduced-order model show good agreement with a full model both in terms of the state of the system and its hysteretic behaviour.     

Isospin mixing in 12C

We observe a yield to the 1⁺T = 1 level in ¹²C at 15.11 MeV in the isospin forbidden ¹²C(d, d') and ¹⁰B(α, d) reactions at about 1 % of the yield to the 1⁺T = 0 level at 12.71 MeV. Observed yields to the T = 12⁺ level at 16.11 MeV in both reactions at about half the yield to the 15.11 MeV level preclude attributing this observed isospin violation entirely to final state mixing. From the ratios of the spectroscopic factors for the 12.71 and 15.11 MeV levels in ¹²C and the ground state of ¹²B from the ¹³C(d, t) and ¹³C(d, ³He) reactions, we find a charge dependent matrix element between the 1⁺ states in ¹²C of 179 ± 75 keV.     

Experimental results on J/ψ production by π±, K±, p and p incident on hydrogen at 39.5 GeV/c

J/ψ production at 40 GeV/c by π^±, K^±, p and $\text{p}$ incident on hydrogen has been studied and results compared with those obtained on tungsten in the same experiment. On hydrogen, J/ψ cross-section ratios relative to π^? have been measured to be (for $\text{x}{}_{\mathrm{<mtext>F</mtext>}}\text{> 0) σ(π}{}^{\mathrm{?}}\text{) : σ(π}{}^{\mathrm{+}}\text{) : σ(}\text{p}\text{) : σ(}\text{p}\text{) = 1 : (0.78 ± 0.09) : (0.83 ± 0.35) : (0.07 ± 0.04)}$. The suppression of the proton induced cross sections shows the importance of calence quark-antiquark fusiin J/ψ production at this energy (i.e. M_J²/_ψ/s=0.13).     

Preparation of functionalized tertiary thiols and nitrosothiols

The development and preparation of five series of tertiary thiols and nitrosothiols as nitric oxide releasing molecules functionalized with acid, alcohol, or amine groups for future conjugation are reported.     

Compression studies on a monolayer of polymer stabilized latices at the air/2 molar sodium chloride solution interface

Summary The two dimensional compression technique ofDoroszkowski et al. has been used to study the steric repulsion force for a monolayer of poly(vinyl pyrrolidone) stabilized polystyrene latex particles spread at the Air/2M sodium chloride solution interface. Repulsion forces were first detected at a particle separation of 150 nm with a dramatic increase in repulsion at about 15 nm.

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Zusammenfassung Die sterische Abstoßung zwischen Polystyrol-Latexteilchen in einer Monoschicht wurde nach der Methode vonDoroszkowski et al. gemessen. Die Latexteilchen waren mit Polyvinylpyrrolidon stabilisiert und an der Grenzfläche einer 2M Natriumchloridlösung zur Luft gespreitet. Die Abstoßungskräfte machten sich bei einer Annäherung der Teilchen auf 150 nm zum 1. Mal bemerkbar. Sie stiegen drastisch an bei etwa 15 nm.

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With 4 figures and 1 table