Hierarchical structure of SERS substrates possessing the silver ring morphology

1. Download : Download high-res image (366KB)
2. Download : Download full-size image

     

Chemical Mechanism for Fluorapatite Dissolution in Acids

Abstract

New chemical mechanism for acidic dissolution of fluorapatite is discussed.     

Chemical aspects of the radiation stability of macrocyclic extractants designed for 90Sr separation

1. Download : Download high-res image (100KB)
2. Download : Download full-size image

     

Quantum corrections to ϕ 4 model solutions and applications to Heisenberg chain dynamics

The Heisenberg spin chain is considered in ? ⁴ model approximation. Quantum corrections to classical solutions of the one-dimensional ? ⁴ model within the correspondent physics are evaluated with account of rest d-1 dimensions of a d-dimensional theory. A quantization of the model is considered in terms of spacetime functional integral. The generalized zeta-function formalism is used to renormalize and evaluate the functional integral and quantum corrections to energy in a quasiclassical approximation. The results are applied to appropriate conditions of the spin chain model and its dynamics, for which elementary solutions, energy and the quantum corrections are calculated.     

First measurements of 238Pu and 238Pu/137Cs activity ratio in Montenegro soil

Plutonium-238 (²³⁸Pu) activity concentrations in soil samples from Montenegro (six samples from three localities) have been measured for the first time. The ²³⁸Pu/¹³⁷Cs activity ratio was determined on the basis of alpha and gamma-spectrometric measurements, and found to be with an average of 0.0006 and standard deviation of 0.0003. By using the activity ratios determined in the present study, ²³⁸Pu activity concentrations were estimated for three localities in the central: one in the northern, and two in the eastern part of Montenegro.     

Sequential-dissociation kinetics of non-covalent complexes of DNA with multiple proteins in separation-based approach: General theory and its application

Binding of multiple proteins to DNA is crucial in many regulatory cellular processes. The kinetics of assembly and disassembly of DNA–multiple protein complexes is very difficult to study in detail due to the lack of suitable experimental approaches. A separation-based approach has been recently proposed to resolve disassembly kinetics of such complexes. While conceptually simple, the separation-based approach generates experimental data with very complex patterns. The analysis of these patterns is a challenging problem on its own. Here we report on a mathematical approach that can extract a solution for the experimental data obtained in separation-based analysis of sequential dissociation of a DNA complex with multiple proteins. This case describes the dissociation of proteins one-by-one from the complex. Generally speaking, a mathematical solution of such problems requires calculations of multiple integrals. Our approach reduces this procedure to taking double integrals and constructing their superposition. We tested this approach with the experimental data obtained for three-step sequential dissociation of complexes of DNA with two protein copies.     

EPR Study of Ligand Effects in Spin Triads of Bis(o-Semiquinonato)Copper(II) Complexes

We report the X-band (9 GHz) electron paramagnetic resonance (EPR) study of series of bis(o-semiquinonato)copper(II) complexes with different ligands. It was found previously, that exchange interactions in spin triads of these compounds are very sensitive to the structure of the ligand coordinated to the central copper(II) ion. Ligand moderates the copper–radical and radical–radical exchange interactions and strongly changes the magnetic properties of the compound. Depending on a ligand, ferromagnetic or antiferromagnetic character of exchange dominates in the system. The EPR study of these complexes allowed us to obtain information on zero-field splitting parameters and their distributions in the studied compounds. The EPR results compliment previously obtained spectroscopic data on these compounds and suggest the pronounced plasticity of the clusters manifested in the broad distributions of their rhombicity parameters.     

Quantum carpets woven by cold atoms in a laser field

Propagation of wave packets of cold two-level atoms in a standing-wave laser field can be interpreted in the dressed-state basis as motion in two optical potentials. The three distinct regimes of the wavepacket motion are specified by the ratio of the squared atom–laser detuning to the normalized Doppler shift. We calculate the momentum and position probability densities, which form patterns with minima and maxima of probability both in the momentum and the position spaces known as quantum carpets. At small and large detunings, the atomic motion is substantially adiabatic, and the quantum carpets have a simple form. At intermediate detunings, the wave packet moves nonadiabatically, splitting at each node of the standing wave, which causes a proliferation or branching of atomic trajectories with a single atom. Nonadiabatic transitions produce beautiful quantum carpets with a rich structure.