Effects of heat-transfer conditions on the performance of a liquid thermal-diffusion column

Theoretical concepts on the parasitic-correction mechanism [1] in thermal diffusion columns have been confirmed by experiment.     

Effects of the concentration-dependent density on liquid separation in a thermal-diffusion column

An analysis is given for the solution to a system of equations describing the separation in a liquid thermal-diffusion column. Similarity numbers are derived for the effects of concentration and thermal expansion on the separation. A method is given for calculating the thermal-diffusion constant that eliminates the effects of concentration on the density.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 12, No. 5, pp. 790–794, May, 1970.     

Transient in a thermodiffusion column with temperature asymmetry

On the basis of an already known physical model, quantitative relations are derived which describe the transient process in thermodiffusion columns with temperature asymmetry.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 21, No. 2, pp. 341–346, August, 1971.     

Transient response of a thermal-diffusion column with buffer vessels at the ends

The transient response in a column with buffer vessels at the ends has been determined for the approximation c(l–c)=a+bc, and this is compared with the asymptotic solution for small times; the range of application of the latter has been determined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 3, pp. 447–452, March, 1976.     

Transport equations for a complex mixture in a thermal-diffusion column

Transport equations are derived for a thermal-diffusion column containing a multicomponent molecular mixture.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 36, No. 4, pp. 668–675, April, 1979.     

Modified frazier-scheme thermal-diffusion columns with column length varied at a constant ratio

The separation theory of the modified Frazier-scheme thermal-diffusion columns with column length varied at a constant ratio has been investigated. The equations for estimating the best ratio of column length and the best column number as well as the maximum degree of separation have been derived. It is found that about 10% of improvement can be achieved by employing the present type of modified Frazier scheme rather than by using the classic Frazier scheme.     

Transient-state soret-coefficient determination for a thermal-diffusion column. IV

Another method is given for approximating a solution previously obtained for small times, and a comparison is made with experiment.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol.31, No.1, pp.66–72, July, 1976.     

Effect of concentration asymmetry on the effectiveness of thermal-diffusion columns

One reason (never hitherto presented) for the development of parasitic convection in thermal-diffusion columns due to concentration asymmetry around their perimeter is set out; a method is also proposed for taking this effect into consideration quantitatively when conducting this process in the liquid phase.     

Determination of the soret coefficient in a thermal-diffusion column operating in the sampling mode

The Soret coefficient for an ethanol-water mixture near the azeotropic point is determined in a continuously operating thermal-diffusion column.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 33, No. 5, pp. 906–911, November, 1977.     

Effect of feedpoint location for a binary mixture on the efficiency of separation in a thermal-diffusion column

We show that there exists an optimal position of the feedpoint of a column at which the separation efficiency is maximum and for which, at the same time, the energy consumption is a minimum.     

Methods of determining the thermal-diffusion constant in liquid mixtures

The article discusses methods for determining Soret coefficients in highly diluted solutions and liquid isotope mixtures.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 38, No. 6, pp. 1066–1076, June, 1980.     

液氦温区国际温标的转换

概括介绍液氦温区国际实用温标的发展情况,系统地给出温标T24,T29,T32,T37,TBS,T48,T55E,TL55,T58,T62,T68,T76以及目前正在采用的T90之间的转换关系,为此编写了计算机程序,可直接用于以上各温标间的数值转换.     

Induced free liquid surface oscillations in a visco-elastic liquid column due to angular temperature fluctuations

The response due to time-fluctuating temperature distribution applied at the free surface of a viscoelastic cylindrical liquid column with no axial dependency has been determined analytically. The amplitude of the radial- and angular velocity as well as the free liquid surface elevation has been presented as a function of the “reduced” forcing frequency of the oscillatory temperature and has numerically been evaluated for an angular temperature field proportional to sin 2φ. It was found, that visco-elasticity as described by the Maxwell model has quite some influence upon the liquid behavior. It shows for larger relaxation times besides the enlarged resonance peak additional peaks below and above resonance. This is particularly evident inside the liquid column, indicating a more pronounced elastic behavior of the liquid.     

Determination of the reflectivity of liquid semiconductors over a wide temperature range

A new method for the determination of the reflectivity of liquid semiconductors in the temperature range from the melting point to the boiling point is presented in the paper, The method is based on the pulsed laser irradiation of the semiconductor surface. the time-resolved reflectivity (TRR) measurement technique, and the numerical simulation of the process using a nonequilibrium thermal model, Matching the experimental and computed values of the maximum reflectivity of the cw probe laser and the surface melt duration in the dependence on energy density of the laser pulse and a least-squares-based fitting procedure lead to the determination of the reflectivity of the liquid at the wavelength of the primary laser beam, The method is illustrated by experimental data on XeCl (308-nm) and ArF (193-nm) excimer laser irradiation of Si(100 ), giving the results B,=0.67±0.01-(8±I) x10^–5 (T-1687) at 308 nm and R,= 0.755 ±0.010 - (7 ± I ) x 10^–5( T-1687) at 193 rim, where R, is the reflectivity of the liquid and T is temperature in K,Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Liquid surface oscillations in a viscous liquid column induced by temperature fluctuations

It was found that timewise fluctuating temperature gradients induce, due to the variation of the surface tension, oscillations of the free surface of a liquid column, which may in or close to resonance lead to large amplitudes, able to disingtegrate the liquid system. An analytical solution leading to the magnification functions and their phases is presented for an arbitrary angular temperature field.     

Modeling retention and selectivity as a function of pH and column temperature in liquid chromatography

In reversed-phase liquid chromatography (RPLC), the retention of weak acids and bases is a sigmoidal function of the mobile-phase pH. Therefore, pH is a key chromatographic variable to optimize retention and selectivity. Furthermore, at an eluent pH close to the pKa of the solute, the dependence of ionization of the buffer and solute on temperature can be used to improve chromatographic separations involving ionizable solutes by an adequate handling of column temperature. In this paper, we derive a general equation for the prediction of the retentive behavior of ionizable compounds upon simultaneous changes in mobile-phase pH and column temperature. Four experiments, two limiting pH values and two temperatures, provide the input data that allow predictions in the whole range of these two variables, based on the thermodynamic fundamentals of the involved equilibria. Also, the study demonstrates the significant role that the choice of the buffer compound would have on selectivity factors in RPLC at temperatures higher than 25 degrees C.     

Parameters of a countercurrent thermal-diffusion apparatus with flow closure and sampling

Formulas have been derived for the optimum apparatus parameters.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 2, pp. 280–284, August, 1987.     

Combination of column temperature gradient and mobile phase flow gradient in microcolumn and capillary column high-performance liquid chromatography

The combination of several gradient modes (solvent, temperature, and flow programming) is rarely used in HPLC analysis. In this work, the separations obtained utilizing simultaneous flow and temperature gradient in capillary column and microcolumn HPLC were compared with the separations performed under isocratic, isothermal, and isorheic (constant flow) conditions. When the mobile phase flow rate and the column temperature were changed simultaneously during the separation run, the analysis time was shortened up to 50%, while the separation efficiency was preserved. The separations obtained with combined temperature and flow gradients show high reproducibility (relative standard deviation <2.0%), comparable to the reproducibility normally seen with a mobile phase gradient. For capillary HPLC, simultaneous temperature and flow programming is the method of choice because of the great technical difficulties involved in performing solvent gradient elution.     

Automation of nanoscale microcapillary liquid chromatography-tandem mass spectrometry with a vented column

To fully automate the sample introduction step for nanoscale microcapillary liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses, 75 microm i.d. x 14 cm capillary columns were interfaced with a commercial autosampler instrument using a novel procedure which allowed dilute peptide samples to be transferred from the AS loop injector to the nanoscale column at flow rates up to 5 microL min(-1). On-column enrichment and desalting was demonstrated for large sample volumes (>40 microL) by constructing a vent 2 cm after the entrance to the packed bed of 5-microm ODS-AQ modified silica. Salts and nonretained solutes were removed via the vent, which allowed for column washing independent of the continuation of the bed into the electrospray source. Separations of test peptide mixtures demonstrated 50-nL elution peak volumes with low- to subfemtomole detection levels. In addition, a highly complex peptide mixture (outer membrane preparation from Psuedemonas aeruginosa) was efficiently separated with more than 100 proteins identified from a single reversed-phase LC-MS/MS analysis. Finally, the vented column (V-column) was utilized for on-line separations in a multidimensional chromatography/tandem MS experiment where large numbers of strong cation exchange chromatography fractions from a trypsinized yeast lysate were desalted, concentrated, and analyzed in a completely automated fashion. The procedures for constructing and using a V-column require minimal changes in current methods and equipment for nano-LC-MS analyses using columns of 100-microm diameter and smaller.     

Nonlinear vibration control of a tall structure with tuned liquid column damper

The nonlinear vibration model of a structure with the tuned liquid column damper (TLCD) is established. TLCD is a successful structure control device. The damping of TLCD is amplitude-dependent and consequently nonlinear. Due to its complexity, the effective linear model is considered for investigating structure characteristics in almost all literatures. Moreover, the structure is usually modeled as a single degree of freedom model. However, the analytical solution for this nonlinear system is derived here. Further, it is found that the optimum design of TLCD for the suppression of vibration depends greatly on the structure parameters.