Rayleigh wave propagation in centrosymmetric materials with micro-stiffness, flexoelectric and micro-inertia effects.

A theoretical investigation of Rayleigh waves propagation in polarized media has been carried out using a reformulated flexoelectric theory for isotropic dielectrics with micro-inertia effect. Within this non-classical theory, the internal energy density is the functional of the strain tensor, dilatation gradient, deviatoric part of stretch gradient and rotation gradient tensors, polarization vector, and polarization gradient. The obtained system of governing equations additionally contains three material length-scale parameters to account the micro-stiffness effect, one material constant to capture the micro-inertia effect, two flexoelectric constants to describe the flexoelectric effect and three length scale parameters related to the polarization gradient. To solve the coupled governing equations, the method of Lamé-type potentials for mechanical displacement and electric polarization vectors is used. The influences of various factors such as micro-stiffness, flexoelectricity, electric quadrupoles and micro-inertia effects on the phase velocity of the Rayleigh waves in a homogeneous isotropic half-space are studied. It is found that above effects become significant with the increase of the wavenumber. This study can be important for the investigation of high frequency surface acoustic waves in dielectric materials.

In silico analysis of interaction pattern switching in ligandreceptor binding in Golgi α-mannosidase II induced by the protonated states of inhibitors.

Golgi α-mannosidase II (GM) is a pharmaceutical target for the design of inhibitors with anticancer activity. The known potent GM inhibitors undergo complex interactions with Zn2+ ions and the active-site amino acids, many of which contain ionisable functional groups. Herein, the physical insight into the ligandreceptor interactions has been provided based on energy decomposition techniques: SAPT (symmetry adapted perturbation theory) and FMO-PIEDA (fragment molecular orbital-pair interaction energy decomposition analysis) for a large GM active-site cluster. Protonation-dependent molecular recognition in Golgi α-mannosidase was demonstrated for five inhibitors, mannose, and its transition state. Zn2+ ion and Asp472 induce the key interactions with the deprotonated inhibitors (bearing an amino group in the neutral state), followed by Asp92 and Asp341. This interaction pattern is consistent for all the studied inhibitors and is similar to the interaction pattern of the enzyme native substrate - mannose. The interactions with Zn2+ ion become repulsive for the protonated states of the inhibitors (bearing an amino group with +1 charge) and the mannosyl transition state. The importance of Asp92 and Asp204 considerably increases, while the interactions with Asp472 and Asp341 are slightly modified. The interaction pattern for the protonated ligands seems to have an oxocarbenium transition state-like character, rather than a Michaelis complex of GM. The electrostatic interactions with amino acids coordinating zinc ion are of key importance for both the neutral and protonated states of the inhibitors. The ligand's diol group has a dual role as an electron donor, coordinating zinc ion, and as an electron acceptor, interacting with Asp92 and Asp472 via strong hydrogen bonds. This interaction pattern is an essential structural feature of the potent GM inhibitors, which is consistent with the experimental findings. Based on the calculations, either the protonated or deprotonated state of the ligand may be the active form of the GM inhibitor, exhibiting different interacting patterns.

Regional long-term co-operation in the field of nuclear and radiation emergency preparedness.

Emergency preparedness is generally covered by methodical and coordinative activities of the International Atomic Energy Agency (IAEA) in Member States of the IAEA and by the European Commission (EC) in EU Member and EU Accession Countries. However, the regional harmonisation of emergency arrangements is an important trend of emergency preparedness. The present paper gives a couple of illustrative examples for a regional co-operation in the field of emergency preparedness in Central Europe and an overview on international exercises in this region. The penultimate section contains an outlook on future activities regarding regional co-operation in Central Europe. The following topics have been suggested inter alia: the harmonisation of intervention criteria and countermeasures, co-ordination in the field of information of the public, comprehensive bi lateral and multilateral exercises, exchange of experts between the national nuclear emergency centres and inter-comparison calculations of the computer codes.