Search

An active system of temperature regulation and temperature gradient in a sample on the example NMR sensor is described in this work. By supporting the given average temperature, the system of temperature-stabilization allows one to set and supervise the size and direction of the temperature gradient along a sample. The temperature of a sample is maintained with on accuracy of about ±0.1°C in a temperature interval of -150 to +200°C with a longitudinal temperature gradient no more than ±0.2°C. The value of the temperature gradient is established in the range of 0° to 10°C/cm in both directions.

Experimental data on the self-diffusion of the molecules of n-(p-ethoxybenzilidene)-p'-n-butylaniline (EBBA) isotropic nematic in the bulk and porous media are reported. It is disclosed that, as the temperature decreases, the temperature dependence of the ratio of the self-diffusion coefficient of EBBA in a porous medium Deff to that of EBBA in the bulk Ds is transformed from the Deff/Ds = const regime to the Deff/DS =f(T) mode at 361 and 355 K for porous media with pore diameters 40 and 400 Å, respectively. It was also found that in the bulk EBBA, temperature dependence of the self-diffusion coefficient near the temperature of isotropicnematic transition deviates from the Arrhenius pattern and diffusion decay becomes nonexponential. These facts are related to the presence of nematically ordered cybotactic groups in the EBBA isotropic phase and to their effect on the mean self-diffusion coefficient of EBBA molecules at temperatures much higher than that of isotropic-nematic transition. It is noted that the presence of cybotaclic groups affects diffusion in the porous medium much more strongly than that in the bulk EBBA. © 2000 MAIK "Nauka/Interperiodica".

An active system of temperature regulation and temperature gradient in a sample on the example NMR sensor is described in this work. By supporting the given average temperature, the system of temperature-stabilization allows one to set and supervise the size and direction of the temperature gradient along a sample. The temperature of a sample is maintained with on accuracy of about ±0.1°C in a temperature interval of-150 to +200°C with a longitudinal temperature gradient no more than ±0.2°C. The value of the temperature gradient is established in the range of 0° to 10°C/cm in both directions. © 1998 MAHK Hayka/Interperiodica Publishing.

Experimental data on the self-diffusion of the molecules of n-(p-ethoxybenzilidene)-p'-n-butylaniline (EBBA) isotropic nematic in the bulk and porous media are reported. It is disclosed that, as the temperature decreases, the temperature dependence of the ratio of the self-diffusion coefficient of EBBA in a porous medium Deff to that of EBBA in the bulk Ds is transformed from the Deff/Ds = const regime to the Deff/DS =f(T) mode at 361 and 355 K for porous media with pore diameters 40 and 400 Å, respectively. It was also found that in the bulk EBBA, temperature dependence of the self-diffusion coefficient near the temperature of isotropicnematic transition deviates from the Arrhenius pattern and diffusion decay becomes nonexponential. These facts are related to the presence of nematically ordered cybotactic groups in the EBBA isotropic phase and to their effect on the mean self-diffusion coefficient of EBBA molecules at temperatures much higher than that of isotropic-nematic transition. It is noted that the presence of cybotaclic groups affects diffusion in the porous medium much more strongly than that in the bulk EBBA. © 2000 MAIK "Nauka/Interperiodica".

An active system of temperature regulation and temperature gradient in a sample on the example NMR sensor is described in this work. By supporting the given average temperature, the system of temperature-stabilization allows one to set and supervise the size and direction of the temperature gradient along a sample. The temperature of a sample is maintained with on accuracy of about ±0.1°C in a temperature interval of -150 to +200°C with a longitudinal temperature gradient no more than ±0.2°C. The value of the temperature gradient is established in the range of 0° to 10°C/cm in both directions.

An active system of temperature regulation and temperature gradient in a sample on the example NMR sensor is described in this work. By supporting the given average temperature, the system of temperature-stabilization allows one to set and supervise the size and direction of the temperature gradient along a sample. The temperature of a sample is maintained with on accuracy of about ±0.1°C in a temperature interval of-150 to +200°C with a longitudinal temperature gradient no more than ±0.2°C. The value of the temperature gradient is established in the range of 0° to 10°C/cm in both directions. © 1998 MAHK Hayka/Interperiodica Publishing.