ICR heating in ion separation systems

A systematic procedure for analyzing the physical processes that govern ICR heating in systems for ion separation is developed. The procedure is based on an analytic model of an rf antenna generating rf fields within a plasma column in a magnetic field and includes such issues as the calculation of rf fields, examination of the ICR interaction of ions with these fields, and determination of the distribution function of the ion flow at the exit from the ICR heating system. It is shown that, even in ICR heating systems with easily achievable parameter values, ions with appreciably different masses can be efficiently separated by energy.     

ICR heating of a plasma with a complex ion composition

Two methods for simultaneously heating ions with different masses and, accordingly, with different gyrofrequencies are considered. The first is heating in a steady uniform magnetic field by a nonmonochromatic RF field, and the second is heating in a nonuniform magnetic field by a monochromatic RF field. In the first method, the cyclotron resonance condition is ensured by the finite width of the RF field spectrum, while in the second one, by a drop in the magnetic field along the system. The study is based on the previously developed analytic model of the excitation of RF fields by current-carrying antennas. Nonlinear effects caused by variations in the longitudinal ion velocities during the ICR interaction are taken into account. It is found that ions with atomic masses in the range 85 < A < 150 (fragments of a spent nuclear fuel) can be efficiently heated in systems with moderate parameters.     

Calculation of the ion distribution function over transverse velocities under ICR heating conditions and separation parameters of a collector of heated ions

The ion distribution function over transverse velocities and the ion heating efficiency (which is defined as the fraction η of ions heated above a certain energy W_min) are calculated in the context of a plasma method for isotope separation on the basis of ion cyclotron resonance heating. The ion distribution function over longitudinal velocities is assumed to be linear in the range of low velocities. It is shown that, when the ions are heated to high energies, the averaged ion distribution function over transverse velocities becomes highly nonequilibrium and has two peaks. Results are presented from calculations of the ion heating efficiency η for W_min=40 eV and for different values of the parameter p that characterizes the ratio of the wavelength λ of the antenna electric field to the length L of the heating region. The relative roles of the time-of-flight and the Doppler broadening are analyzed, and the separation parameters of a collector of heated ions are estimated.     

Analysis of the separation of gadolinium isotopes by the ICR method

The problem of separating gadolinium isotopes is discussed. The parameters of isotope separation in a plasma by the ICR method are estimated for a device with given operating parameters. The mean transverse energy 〈E_⊥〉 of the heated ions of the ¹⁵⁷Gd isotope and the heating efficiency η are calculated as functions of the frequency of the RF electric field in the plasma. The dependence of the heating efficiency η on the longitudinal temperature of the plasma flow is investigated. The issue of how the concentration of the target isotope ions at the collector plate depends on the longitudinal coordinate measured from the front edge of the plate is analyzed for different values of the frequency detuning parameter. The extraction coefficient Г for the target isotope is calculated as a function of the distance b between the collector plates for different frequency detunings.     

Theory of the ICR heating of a plasma column: Methodological note

A set of wave equations is derived that describes electromagnetic waves at frequencies on the order of the ion gyrofrequency in a plasma column with an arbitrary electron temperature. This set takes into account, in particular, the resonant interaction of electrons with waves in the transit-time magnetic pumping regime. The effect of the amplification of the electromagnetic fields of current-carrying antennas by the plasma is analyzed. The evolution of the fields with an increase of plasma density from a zero value (vacuum) is considered. The main parameters are determined for minority ion cyclotron resonance heating in the planned EPSILON system.     

Calcium ion cyclotron resonance (ICR) transfers information to living systems: effects on human epithelial cell differentiation

The specific aim of the present work concerns the effectiveness of low-frequency electromagnetic fields treatment to modify biochemical properties of human keratinocytes (HaCaT). Cells exposed to a 7 Hz electromagnetic field, tuned to calcium ion cyclotron resonance (ICR), showed modifications in the cytoskeleton. These modifications were related to different actin distributions as revealed by phalloidin fluorescence analysis. Indirect immunofluorescence with fluorescent antibodies against involucrin and beta catenin, both differentiation and adhesion markers, revealed an increase in involucrin and beta-catenin expression, indicating that exposure to electromagnetic field carries keratinocytes to an upper differentiation level. This study confirms our previous observation and supports the hypothesis that a 7 Hz calcium ICR electromagnetic field may modify cell biochemistry and interfere in the differentiation and cellular adhesion of normal keratinocytes, suggesting the possibility to use ICR electromagnetic therapy for the treatment of undifferentiated diseases.     

Statistical thermodynamics of phase separation and ion partitioning in aqueous two-phase systems.

A general model for the phase behavior of polymer-polymer aqueous two-phase systems containing small amounts of added inorganic salts has been developed from statistical thermodynamics. The model is based on the solution theory of Hill and new electrolyte solution model based on Fluctuation Solution Theory. It includes the effect of polymer molecular weight with scaling expressions from the Renormalization Group theory of polymer solutions. The model has been used to calculate the phase diagram and the partitioning of salt for an aqueous two-phase system containing polyethylene glycol (MW = 8000) and dextran (MW = 28,700) with 0.1 mole/kg of added Na2SO4. The calculations have been compared to experimental results with good agreement.     

Measurements of the load resistance of a poloidal antenna and the phase velocity of fast magnetosonic waves during ICR plasma heating in the L-2M stellarator

The propagation and damping of waves excited by a poloidal antenna in a hydrogen plasma at the ion cyclotron resonance (ICR) frequency were investigated. The longitudinal wavenumber and damping length of waves excited in the ohmically heated plasma of the L-2M stellarator, the dependence of the damping length of fast magnetosonic waves on the magnetic field strength, and the dependence of the antenna load resistance on the plasma density were measured. It is the first time that such complex measurements were performed in experiments on ICR heating of a hydrogen plasma at the fundamental harmonic of the ion gyrofrequency in toroidal magnetic confinement systems.     

Changes in antenna of photosystem II induced by short-term heating

Changes in antenna of photosystem II, induced by short-term heating, were studied using characteristics of a short-wavelength band in low-temperature fluorescence spectra (77 K) of pea chloroplasts. Heating for 5 min was carried out at 25 and 45°C in the darkness or in the presence of white light with intensity of 260 or 1,400 μmol/m²s. Most modes of thermal treating induced a decrease in integral intensity of the band and an increase of its half-width. The changes were more prominent at high-temperature heating. The second derivative of the contour of a short-wavelength band showed its three components around 680, 685, and 693 nm, the first of which belongs to emission of the outer antenna of Photosystem II, and the other two to its inner antenna. As the fourth derivative shows, high-temperature heating in the presence of light evokes an appearance of some additional components in a short-wavelength region (654, 658, 661, 666, 672, and 675 nm) as well as of two additional components, 682 and 689 nm, in the region of 685-nm peak. Two subcomponents, 692 and 694 nm, can be detected in the 693-nm component. The results are discussed on the basis of the data concerning energy levels and pathways of energy transfer in pigment–protein complexes of the outer and the inner antennas of photosystem II. It is assumed that a protective role of low light relates to inducing of an essential disarrangement in the outer and the inner antennas and of a subsequent decrease in energy funneling to reaction centers, which, in turn, lowers the extent of photoinhibition.     

Kinetics of ion exchange process for separation of glutamic acid

Kinetics of the separation of L-glutamic acid (GLU) by ion exchange has been studied with strongly acidic H⁺-type cation exchange resin Amberlite IR-122. Since glutamic acid is a trivalent ampholyte and dissociates according to three equilibrium reactions, separation of G⁺ ions by a cation exchange process is accompanied by the dominant reversible reaction, i.e. G⁺+H⁺ ? G⁰. Accompanying reversible reaction has an effect on the ion exchange rate, and decreases the performance of the process comparing with the ideal case that the exchanging ions retain their identity. The analysis was performed first with the ion exchange column, DIC (L/D=0.52); and then with the ion exchange column, IC (L/D=10.9). The data were collected with model glutamic acid solutions for both DIC and IC columns/reactors. IC experimental results were then compared with that of DIC and the effect of scale up on ion exchange process was investigated. The experimental results have provided an adequate basis for the design calculations, and the design parameters were determined. Rate coefficients for the liquid phase mass transfer controlled cation exchange process were calculated and interrelated with a plot of j _Mfactor versus Reynolds number.     

Changes of the antenna of photosystem I induced by short-term heating

Changes in low-temperature fluorescence spectra of pea chloroplasts induced by the short-term heating were studied. Excitation spectra of the long-wavelength fluorescence were studied as well. Heating was carried out at 45°C for 5 min in the darkness or in the presence of white light sourced with intensities of 260 or 1400 μmol/m² s. All variants of heating decreased the intensity of the long-wavelength fluorescence band. The integral of the excitation spectrum decreased after the exposure to heating in the darkness and increased after the exposure to heating in the presence of light. The observed changes in most intensive components — 726, 729 and 731 nm — of the long-wavelength fluorescence band, induced by various modes of heating, were similar. The changes in the fourth intensive component at 735 nm were different. Twenty-five components were found in the fine structure of the excitation spectrum of the long-wavelength fluorescence. Positions of most of peaks corresponded to the absorption peaks of Lhca proteins. Heat-induced changes in the excitation spectrum in the regions corresponding to the absorption of chl b and short-wavelength forms of chl a have been shown to correlate with changes in the intensities of the 726-, 729-, and 731-nm components of the long-wavelength fluorescence. This allows one to assign them to the emission of the outer antenna of Photosystem I. Changes in the intensity of the component at 735 nm correlated only with changes in excitation spectrum in the long-wavelength region that corresponded to the absorption of the long-wave-length forms of chlorophyll a. Therefore, the 735-nm component could be assigned to the emission of the Photosystem I inner antenna. Analysis of the changes induced by heating in the emission and excitation spectra of fluorescence revealed changes in the energy transfer in the outer and the inner antennas of Photosystem I. Heating in the darkness lowered the energy transfer in the outer and in the inner antennas. Both modes of heating in the presence of light increased the energy transfer in the outer antenna. For the inner antenna, presence of the light promotes an efficient of energy transfer at the levels close to the control one. It is proposed that illumination during heating exposure causes a specific state of the antenna complex in Photosystem I that provides an increase in funneling of the energy toward the reaction centers.     

Chelator,metal ion and buffer studies for protein C separation

Protein C (PC) is the pivotal anticoagulant and antithrombotic in the human coagulation cascade. PC deficiency can result in major medical problems such as deep vein thrombosis (DVT), leading to tissue oxygen deprivation. PC treatment has no bleeding or skin necrosis problems because it circulates in the blood as a zymogen and is only activated when and where it is needed. One source of PC is transgenic animal milk. The major components in the milk, such as alpha-casein, beta-casein, kappa-casein, alpha-lactalbumin and beta-lactoglobulin, are proteins that must be separated from PC. Immobilized metal affinity chromatography (IMAC) is an inexpensive separation technology with relatively high specificity, and it has great potential for difficult protein separations. After systematic studies of different chelator, metal ion and buffers, the combination of iminodiacetic acid (IDA) and Fe was found to be effective to separate PC from major milk components. alpha-Lactalbumin and beta-lactoglobulin fell through the column in the starting buffer. PC was eluted. alpha-Casein, beta-casein, kappa-casein remained bound in the column after PC elution. This technology might be applied for PC separation from transgenic animal milk. It is very important for PC production in large quantities and at low cost to treat PC-deficient patients.     

Kinetics of phase separation for polyethylene glycol-phosphate two-phase systems

Phase separation times for polyethylene glycol (PEG)-4000-phosphate aqueous two-phase systems were studied, for small scale (5-g) and large scale (1300-g) systems, as a -function of the stability ratio. Profiles of dispersion height for both large and small scale systems were represented as a fraction of the initial height and were found to be independent of the geometrical dimensions of the separator. Furthermore, by plotting time as a fraction of the initial height the total time of separation can be calculated for a given height of system at a particular stability ratio. This generalization is important for the design of large scale aqueous two-phase separators. Phase separation times were also found to be dependent on which of the phases is continuous. A characteristic change in phase separation time was also observed at the phase inversion point (i.e., where the dispersed phase changes to a continuous phase and vice versa) and this point tends toward higher volume ratios as the tie-line length (TLL) is increased. Furthermore, the phase inversion point at each TLL corresponds to a fixed phosphate concentration. (c) 1995 John Wiley & Sons, Inc.     

New reactive extraction systems for separation of bio-succinic acid

Biotechnologically produced succinic acid has the potential to displace maleic acid and its uses and to become an important feedstock for the chemical industry. In addition to optimized production strains and fermentation processes, an efficient separation of succinic acid from the aqueous fermentation broth is indispensable to compete with the current petrochemical production processes. In this context, high molecular weight amines are known to be effective extractants for organic acids. For this reason, as a first step of isolation and purification, the reactive extraction of succinic acid was studied by mixing aqueous succinic acid solutions with 448 different amine–solvent mixtures as extraction agents (mixer-settler studies). The extraction agents consist either of one amine and one solvent (208 reactive extraction systems) or two amines and two solvents (240 reactive extraction systems). Maximum extraction yields of succinic acid from an aqueous solution with 423 mM succinic acid at pH 2.0 were obtained with more than 95% yield with trihexylamine solved in 1-octanol or with dihexylamine and diisooctylamine solved in 1-octanol and 1-hexanol. Applying these optimized reactive extraction systems with Escherichia coli fermentation broth resulted in extraction yields of 78–85% due to the increased ionic strength of the fermentation supernatant and the co-extraction of other organic acids (e.g., lactic acid and acetic acid), which represent typical fermentation byproducts.     

A linear framework for time-scale separation in nonlinear biochemical systems

Cellular physiology is implemented by formidably complex biochemical systems with highly nonlinear dynamics, presenting a challenge for both experiment and theory. Time-scale separation has been one of the few theoretical methods for distilling general principles from such complexity. It has provided essential insights in areas such as enzyme kinetics, allosteric enzymes, G-protein coupled receptors, ion channels, gene regulation and post-translational modification. In each case, internal molecular complexity has been eliminated, leading to rational algebraic expressions among the remaining components. This has yielded familiar formulas such as those of Michaelis-Menten in enzyme kinetics, Monod-Wyman-Changeux in allostery and Ackers-Johnson-Shea in gene regulation. Here we show that these calculations are all instances of a single graph-theoretic framework. Despite the biochemical nonlinearity to which it is applied, this framework is entirely linear, yet requires no approximation. We show that elimination of internal complexity is feasible when the relevant graph is strongly connected. The framework provides a new methodology with the potential to subdue combinatorial explosion at the molecular level.     

Microbial diversity in biofilms from corroding heating systems

Culture-independent investigations of the bacterial diversity and activity in district heating systems with and without corrosion did not make it possible to relate one group of microorganisms with the observed corrosion. Fluorescence in situ hybridization by oligonucleotide probes revealed the dominance of beta-proteobacteria, sulphate reducing prokaryotes and alpha-proteobacteria. Analysis of a clone library from one Danish heating (DH) system showed that the most sequences formed two clusters within the alpha-proteobacteria affiliated to the families Rhizobiaceae and Acetobacteraceae and two clusters within the beta-proteobacteria belonging to the family Comamonadaceae. Functional groups were determined by microautoradiography showing aerobic and anaerobic bacteria (sulphate reducing and methanogenic bacteria). The corrosion study showed that pitting corrosion rates were five to ten times higher than the general corrosion rates, suggesting the presence of biocorrosion. The results indicate that several bacterial groups could be involved in corrosion of DH system piping including sulphate reducing prokaryotes, Acidovorax (within the beta-proteobacteria), methanogenic bacteria and others.