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A versatile molecule is described that performs as a nondestructible read-out optical-storage molecular memory. This molecular memory is composed of two distinct molecules that are chemically bonded to each other to form a single molecule with unique properties. One component is a photochromic fulgimide, and the other is a strongly fluorescing oxazine dye. This composite molecule was specifically designed and synthesized to display, under specific conditions, both the photochromic functions of the first component and the fluorescence properties of the dye. To store information, the polar, closed form of the photochromic component is illuminated with 530-nm light, which converts it to the open, nonpolar form. The information is accessed by excitation at the 650-nm band of the oxazine dye component, causing the dye to fluoresce. However, the dye emits intense fluorescence under a nonpolar environment, which is attained only when the fulgimide component is in its open, nonpolar structure. The ultrafast kinetics, spectroscopy, and mechanism of the photoreaction of this molecule and its photoinduced intermediates have been measured, and fluorescence quantum yields and cross sections were determined.

A molecular dynamics simulation study was performed to investigate the influence of molecular weight (MW) on the conformation dynamics of oil contaminants onto Al 2 O 3 surface in aqueous solution. In the present work, two kinds of adsorption contents were used for each kind of oil contaminants. The simulation results reveal the apparent effect of MW on the dynamics of oil contaminants. Ignoring different adsorption contents, oil contaminants undergo similar microscopic conformational change processes. Meanwhile, some new features are exhibited, owing to the effect of different MWs and oil adsorption contents. At low adsorption content, the oil contaminants with high-MW finally form a contact angle with the hydration substrate surface, while those with low-MW are thoroughly detached. As for oil contaminants at high adsorption content, most of them could not be thoroughly detached from Al 2 O 3 surface. Further, steered molecular dynamics (SMD) simulations were carried out to investigate the microscopic detachment of residual oil contaminants under the action of external force. Finally, the effect of temperature on the conformational change of oil contaminants was studied from molecular scale and it was found that the increase of temperature could effectively promote the detachment of oil contaminants, despite of the influence of MW. All findings in the present study are believed to be helpful for the understanding of the removal mechanism of oil contaminants on solid surface. [ABSTRACT FROM AUTHOR]

Abstract: Three-dimensional molecular dynamics simulations of AFM-based nanometric cutting monocrystalline copper with pin tool radius of 0.713nm are performed to investigate the effect of uncut chip thicknesses (0.1805nm, 0.361nm, 0.5415nm, 0.722nm, 0.9025nm, 1.0875nm, and 1.268nm) on the depth of subsurface deformed layers. The EAM potential and Morse potential are utilized respectively to compute the interactions between workpiece atoms, the interactions between workpiece atoms and tool atoms. The single-atom potential energy variations of the workpiece atoms within the subsurface regions during the cutting process are obtained and analyzed through a deformation criterion to determine the deformation behaviors of subsurface atoms. The simulation results reveal that the depth of subsurface deformed layers is affected by the AFM pin tool''s rake angle. At each uncut chip thickness, the AFM pin tool presents different negative rake angles, consequently different degrees of deformation in the subsurface take place. [Copyright &y& Elsevier]

Abstract: A three-dimensional molecular dynamics (MD) model is utilized to investigate the effect of tool geometry on the deformation process of the workpiece and the nature of deformation process at the atomic-scale. Results show that different states exist between the atomic force microscope (AFM) pin tool and the workpiece surface, i.e. the non-wear state, the ploughing state, the state in which ploughing is dominant and the state in which cutting plays a key role. A relationship between the deformation process of the workpiece and the potential energy variation is presented. The potential energy variation of atoms in different deformed regions in the workpiece such as plastically deformed region, elastically deformed region and the mixed deformation region is different. The features of variations of potential energy are discussed. [Copyright &y& Elsevier]