Dynamics of colloid silver nanoparticles in an evaporating water drop

The method of photon correlation spectroscopy is used to investigate the distribution of the diffusion coefficient of silver nanoparticles in an evaporating water drop given that the drop base area remains unchanged (the pinning condition). It is established that the capillary flow dominates over the diffusion nanoparticle motion in redistribution of concentration of the dissolved nanoparticles.     

An improved broadband decoupling sequence for liquid crystals and solids

Recently we developed an efficient broadband decoupling sequence called SPARC-16 for liquid crystals ?J. Magn. Reson. 130, 317 (1998). The sequence is based upon a 16-step phase cycling of the 2-step TPPM decoupling method for solids ?J. Chem. Phys. 103, 6951 (1995). Since then, we have found that a stepwise variation of the phase angle in the TPPM sequence offers even better results. The application of this new method to a liquid crystalline compound, 4-n-pentyl-4'-cyanobiphenyl, and a solid, L-tyrosine hydrochloride, is reported. The reason for the improvement is explained by an analysis of the problem in the rotating frame.     

Nuclear magnetic resonance study of self-diffusion in liquid crystals

A simple and accurate pulsed-gradient nuclear magnetic resonance technique for measuring coefficients of self-diffusion in liquid crystals is described. It is based on exciting sharp response signals with long weak pulses. The method uses an extremely weak radio-frequency field, which eliminates the problem of radio-frequency heating of the sample. The temperature dependencies of coefficients of self-diffusion for two liquid crystals, 5CB (4-pentyl-4(')-cyanobiphenyl) and EBBA (N-(4-ethoxybenzylidene)-4-butylaniline), are presented.     

Cloused cycle of production of ulltrafine polytetrafluoroethylene and new areas of use of fluoropolymer manufacture waste

The features of processes of ultrafine polytetrafluoroethylene manufacture of waste technological polytetrafluoroethylene by hydrothermal method and thermal degradation with an exhaustive fluorination in the presence of cobalt trifluoride were studied. Compositions and properties of gaseous and solid products of pyrolysis and recycling in ultrafine polytetrafluoroethylene manufacture were determined. Methods of use of ultrafine polytetrafluoroethylene, gaseous products, and spent catalyst were developed. On the basis of the experiments a closed scheme of producing ultrafine polytetrafluoroethylene was proposed in view of its application with recycling of accompanying gas fraction, and separating manufacture waste with recycling of cobalt trifluoride catalyst and using the resulting cobalt difluoride for producing composite coatings and lubricants.     

Development of the method for determination of the content of softwood component in lignins

Methods for the quantitative treatment of IR Fourier spectra for the determination of relative contents of pine and birch lignin in wood were studied.     

Fast protonic conductivity in crystalline benzenehexasulfonic acid hydrates

We report on the crystal structures of two hydrates of benzenehexasulfonic acid, its water sorption isotherm, temperature- and humidity-dependent conductivity, along with ¹H NMR studies. At comparable humidities and temperatures, this crystalline material shows conductivity similar to Nafion, which conducts protons via liquid water channels. We believe that the presented discovery of fast protonic conductivity in benzenehexasulfonic acid at low humidities is encouraging for further efforts in developing highly sulfonated polymers as membranes for fuel cells.     

Depolymerization of polytetrafluoroethylene in the presence of water vapor or fluorine-transfer agent

Relationships of depolymerization of polytetrafl uoroethylene wastes in the presence of water vapor or a fl uorine-transfer agent were studied. The possible fields of application of the products formed (preparation of composite coatings, lubricants, modifying additives to polymeric materials) were outlined.     

Projection of a quantum state on eigenstates of average Hamiltonian

A scheme for projecting an arbitrary quantum state on eigenstates of average Hamiltonian is described. As an experimental example, projection on entangled Bell states, which are eigenstates of specially constructed average Hamiltonian, is demonstrated for a system of two dipolar-coupled nuclear spins. The results of a direct and time-reversed evolution are added to average out the coherences between different eigenstates and accomplish the projection.     

High-resolution NMR imaging of objects with dipolar-broadened spectra

It is shown that, in some substances with dipolar-broadened conventional NMR spectra, it is possible to use long-lived coherent response signals, excited by long and weak radiofrequency pulses, for producing NMR images with high spatial resolution. Compared to other techniques, the method does not require high field gradients or strong radiofrequency fields, and therefore, can be applied to large objects.     

Adiabatic cross-polarization via intermediate dipolar-ordered state

It is experimentally demonstrated that an adiabatic demagnetization-remagnetization in the laboratory frame, where the Zeeman order of abundant nuclei is first adiabatically converted into the dipolar order, and then, into the Zeeman order of rare nuclei, can significantly increase polarization of rare nuclei compared to the conventional cross-polarization technique.