Range Of Linear Velocities Research Articles

Characterization of a macroporous epoxy-polymer based resin for the ion-exchange chromatography of therapeutic proteins

This study investigated the adsorption capacity and mass transfer properties of a novel macroporous epoxy-polymer-based anion-exchanger, MPR Q, for the efficient separation of therapeutic proteins. MPR Q resin was prepared by phase separation based on spinodal decomposition followed by dextran grafting and ligand conjugation. Under static conditions, MPR Q exhibited a binding capacity of 49.8 mg-IgG/cm3-resin at pH 10, whereas the fastest adsorption was observed among the anion-exchanger resins tested. Inverse size-exclusion chromatography (iSEC) experiments revealed that the apparent pore diameter of MPR Q was approximately 90 nm, which was sufficiently large for the penetration of human IgG and bovine IgM. Moreover, the reduced height equivalent to a theoretical plate, h, of human IgG, determined using the linear gradient elution method was 65.8 and was not significantly changed in the range of linear velocities from 20.37 to 50.93 cm/min. The dynamic binding capacity at 10% breakthrough of MPR Q, determined by frontal analysis, exhibited a capacity of 43.8 mg/cm3 at 5.09 cm/min and 58% of DBC10% was maintained even though the linear velocity was increased to 50.93 cm/min. Furthermore, a resolution for separation of IgG and BSA by MPR Q was 1.06 at 5.09 cm/min, while it was higher than that for the conventional resin at all linear velocities from 5.09 cm/min to 50.93 cm/min. Thus, it was suggested that the MPR Q developed in this study is a promising resin that can efficiently separate large biomacromolecules such as human IgG at higher velocities.

Study of the dynamics of the coefficient of external friction of seeds crops with shell

The article is devoted to the study of the coefficients of external friction of grain agricultural products-friction in static and dynamic modes, as the most important physical and mechanical characteristics of bulk materials. The description of carousel laboratory unit, program, methodology and results of studies on the practical determination of the coefficients of external friction for typical agricultural grain products according to the materials typical of the working bodies of the production machines. As a result of the research, it was found that in the range of linear velocities from 0 to 1.75 m/s, there is a change in the friction coefficients, which has a nonlinear character.

Performance of small-domain monolithic silica columns in nano-liquid chromatography and comparison with commercial packed bed columns with 2 µm particles

We report on a direct comparison of the separation performance in capillary nano-LC between commercial packed bed columns and the small-domain silica monoliths in applications. Octadecylsilylated monolithic silica capillary columns with a 50 and 100 µm inner diameter (i.d.) were prepared with a procedure providing domain sizes in the sub-2 µm range. The fabricated monolith columns could provide plate heights (H) of 4.0‒4.2 µm for hexylbenzene (retention factor (k) = 3.6) at an optimal linear velocity range under an isocratic condition, while showing a column permeability (Kv0 = 1.6‒1.8 × 10−14 m2) comparable to that of a column packed with 3‒3.5 µm particles. When the peak capacity (np) for a cytochrome C digest was compared for variable gradient times (tG = 15, 30, 60, and 120 min) and constant gradient steepness (b’), the present monolith columns could show a 30‒40% higher np-value than the packed capillary column with 2 µm particles (e.g. np = 180 versus np = 259 at tG = 30 min). The produced monolith columns showed a high chromatographic repeatability for both isocratic and gradient elution (e.g. relative standard deviation (n = 3, RSD (%)) = 0.5% for H, 2,6% for k, and 5.6% for Kv0 in the isocratic mode using the 100 µm i.d.-columns). The present results show that the domain sizes which can now be achieved for capillary silica monoliths are sufficiently small to result in separation efficiencies that can successfully compete with the commercial packed bed columns available for use in nano-LC applications.

Method for controlling the formation parameters of an elastohydrodynamic layer in rolling bearings

A study was made of the load properties, namely, the control of the formation parameters of an elastohydrodynamic layer in rolling bearings, a range of linear velocities at which an elastohydrodynamic layer of lubricant is formed taking into account axial and radial loads, properties, purpose of the lubricant and design features of a rolling bearing. The method for controlling the parameters of formation of an elastohydrodynamic layer in rolling bearings allows one to determine the parameters of rolling friction at which an elastohydrodynamic layer is formed on the surfaces of rolling bodies, at which the bearing life is maximum.

Influence of Linear Flow Velocity of Uncracked Ammonia (NH3) Gas on Formation of Higher Nitrides, 𝛅-MoN and 𝛆-Fe2N, under Concentrated Solar Irradiation in the SF40 Solar Furnace at PSA

Nitriding experiments for powder specimens of Mo and Fe were carried out using a solar furnace SF40 at PSA (Plataforma Solar de Almeria) in Tabernas (Spain) in uncracked ammonia NH3 gas (NH3 gas with suppressed extent of dissociation by flowing) aiming at determining the range of linear velocity v of NH3 gas flow to yield higher nitride phases, δ-MoN for Mo and e-Fe2N for Fe. Standard solar exposure duration at a specified reaction temperature T was set to be 60 min over range of v between 1.14 mm·s-1 and 11.4 mm·s-1. By X-ray diffraction (XRD) analysis, presence of δ-MoN was detected besides γ-Mo2N and metallic Mo for Mo powder specimen heated to 900 oC in NH3 gas flow at v = 1.14 mm·s-1 but XRD peaks identifiable as δ-MoN became indiscernible when v was increased to 11.4 mm·s-1. On the other hand, for Fe powder specimen exposed to NH3 gas flow at v = 1.14 mm·s-1 at T = 500 oC, remnant metallic α-Fe was detectable by XRD at the down-stream side of the specimen holder but no metallic α-Fe was detected at the up-stream side of the specimen holder suggesting that chemical activity a(N) of N atom in uncracked NH3 gas tended to decrease along the NH3 gas flow path on going from the up-stream side to the down-stream side.

Study of the nature of the dynamic coefficient of internal friction of grainmaterials

The article highlights the issues related to the study of physical and mechanical characteristics of bulk materials, namely internal friction coefficients in static and dynamic modes. An innovative device of the carousel type for determining the frictional characteristics of bulk materials is described, which allows to implement the tasks of practical determination of dynamic coefficients of internal friction. Presented the program, methodology and results of research on the practical study of the internal friction coefficient of typical bulk products of agricultural production in the range of linear velocities of displacement of layers from 0 to 2.79 m/s, the reliability of which is not lower than 0.878.

One pot synthesis of carboxyl functionalized-polyhedral oligomeric siloxane based monolith via photoinitiated thiol-methacrylate polymerization for nano-hydrophilic interaction chromatography

A hybrid monolith exhibiting almost retention independent separation performance in hydrophilic interaction chromatography (HILIC) was obtained by one-pot photoinitiated thiol-methacrylate polymerization. Polyhedral oligomeric silsesquioxane containing methacrylate units (POSS-MA) was used as the main monomer and crosslinking agent, together with a hydrophilic ligand with two carboxyl groups, mercaptosuccinic acid (MSA) as the thiol agent and chromatographic ligand. The isocratic separation of nucleosides, nucleotides and organic acids on MSA attached-poly(POSS-MA) monolith was investigated in HILIC mode. The van-Deemter plots for obtained for nucleosides, nucleotides and benzoic acids clearly showed that there were two regions in each graph with two different slopes in the studied range of linear flow rate (i.e. 0.2–4.3mm/s). The slope of plate height-linear velocity curve was so small in the low linear velocity region between 0.2–2.1mm/s while the slope in high linear velocity region between 2.1–4.3mm/s was so higher with respect to the first region. The van-Deemter plots sketched for all analyte grous used in HILIC mode obeyed this tendency Almost “retention independent plate height behavior” was demonstrated in HILIC, using nucleotides, nucleotides or benzoic acids as the analytes in the linear velocity range of 0.2–2.1mm/s. This behavior was explained by the porous structure of the synthesized monolith facilitating the convective transport of analytes. The variation of plate height was not retention-independent within high linear velocity range (>3.2mm/s) when nucleosides were separated in HILIC mode.

Investigation on the quality of bio-oil produced through fast pyrolysis of biomass-polymer waste mixture

A high-impact poly-styrene (HIPS) was mixed with dried and ground coconut shell (CS) at equal weight percentage. Fast pyrolysis was carried out on the mixture in a fixed bed reactor over a temperature range of 573 K to 1073 K, and a nitrogen (N2) linear velocity range of 7.8x10-5 m/s to 6.7x10-2 m/s to produce bio-oil. Heat transfer and fluid dynamics of the pyrolysis process inside the reactor was visualised by using Computational Fluid Dynamics (CFD). The CFD modelling was validated by experimental results and they both indicated that at temperature of 923 K and N2 linear velocity of 7.8x10-5 m/s, the maximum bio-oil yield of 52.02 wt% is achieved.

The Effect of High Strain Rate on Properties and Microstructure of the Fully Austenitic High Mn Steel

In the paper, results of impact bending tests of a high-manganese steel of X30MnAlSi26-4-3 grade are presented. The tests were carried out using a flywheel machine, suitable for dynamic tensile tests and impact bending tests in the range of linear velocity of the forcing element from 5 ÷ 40 m/s. The obtained test results were compared with the results of impact resistance of the studied steel determined using Charpy machine. Structural investigations were carried out using light microscope and scanning transmission electron microscopy. Creating a mechanical twins at different strain rates was analyzed. The surfaces of fractures formed in the break point during bending tests were analyzed, and they indicate a presence of mixed transcrystalline fractures with a predominance of plastic fractures. Substructure studies revealed the presence of mechanical twinning induced in a high strain rate for the X30MnAlSi26-4-3 steel.

Alkaline cation-exchange chromatography for the reduction of aggregate and a mis-formed disulfide variant in a bispecific antibody purification process.

During the purification development of a bispecific antibody, cation-exchange chromatography was screened for its ability to separate a prominently expressed (>12%) mis-formed disulfide bond variant, termed MAb-diabody, and aggregate from the product of interest. The influence of pH, product load (g of product per liter of resin) and linear velocity on the separations were evaluated for the strong cation-exchange resins SP Sepharose HP and POROS(®) HS50. Cation-exchange chromatography is commonly operated distant to the isoelectric point of a molecule, generally leading to acidic conditions for antibody purification. However, the results herein demonstrated improved removal of MAb-diabody with increasing pH, resulting in reduction of MAb-diabody content greater than 12-fold when operating near the alkaline pI of the product. This approach was successful over a range of linear velocities and g/L of resin loading. Aggregate removal was less affected by pH and was effectively reduced from 10.9% to less than 3% for each condition. Furthermore, this method was successfully scaled to a 60 cm diameter column using SP Sepharose HP resin.

Dynamic evaluation of polypropylene capillary‐channeled fibers as a stationary phase in high‐performance liquid chromatography

Polypropylene (PP) capillary-channeled polymer (C-CP) fiber stationary phases are investigated for applications in HPLC. Specifically, the roles that fiber size and shape, linear velocity, interstitial fraction, and column inner diameter play in separation efficiency were evaluated using a uracil and butylparaben mixture eluted under isocratic conditions. Four fiber types, having nominal diameters ranging from 30 to 65 μm, were used in 250 mm × 2.1 mm columns. Optimum flow characteristics, as judged by plate height and resolution, were observed for 40 μm diameter PP C-CP fibers packed at an interstitial fraction of ~0.63, over a broad range of linear velocities (~2 to 37 mm/s). The influence of column inner diameter was studied on 1.5, 2.1, and 4.6 mm columns packed at the optimal interstitial fraction. The best performing column in terms of plate height and resolution was the 2.1 mm inner diameter. C-CP columns were also evaluated for the separation of a protein mixture composed of ribonuclease A, cytochrome c, and transferrin. Results obtained with the biomacromolecules mixture validate the optimal structural and operative conditions determined with the small solutes, laying the groundwork towards biomacromolecule applications, focusing more on the chemical aspects of separations.

Steam as a carrier gas in capillary chromatography

The use of water as a carrier gas in capillary gas chromatography has been considered. Steam and helium have been compared as a mobile phase for separation of alkanes (using the example of chromatograms of diesel fuel) and polyaromatic compounds (SE-30 and HP-5 capillary columns). Steam has been shown to have an advantage. The peak resolution values calculated for the pair of C18/iso-C20 compounds are 4.4 for steam and 3.9 for helium. The Van Deemter relations have been measured and it has been shown that a significantly lower viscosity of steam compared to helium allows for analysis of substances in a wide range of linear velocities with good selectivity. Steam has been shown to hold promise for chromatographic determination of hydrocarbons.

Water vapor as a carrier gas in capillary gas chromatography

The use of water vapor as carrier gas in capillary chromatography is analyzed. Under equivalent conditions, a comparison of water vapor and helium as a mobile phase was performed during the separation of diesel fuel components. The advantage of water vapor was demonstrated. The resolutions of peaks were calculated for a pair of substances, C18-iso and C20 (4.4 for water vapor and 3.9 for helium). The Van Deemter dependences were measured, and it was demonstrated that the substantially lower viscosity of the water vapor compared to helium makes it possible to perform the separation of substances in a broader range of linear velocities, comparable to hydrogen used as mobile phase. The prospects for using water vapor was demonstrated in chromatographic analysis of hydrocarbons.

The dynamics of the vestibulo-ocular reflex after peripheral vestibular damage. I. Frequency-dependent asymmetry.

Accurate performance by the vestibulo-ocular reflex (VOR) is necessary to stabilize visual fixation during head movements. VOR performance is severely affected by peripheral vestibular damage; after one horizontal semicircular canal is plugged, the horizontal VOR is asymmetric and its amplitude is reduced. The VOR recovers partially. We investigated the limits of recovery by measuring the VOR's response to ipsilesional and contralesional rotation after unilateral peripheral damage in cats. We found that the VOR's response to rotation at high frequencies remained asymmetric after recovery was complete. When the stimulus was a pulse of head velocity comprising a dynamic overshoot followed by a plateau, gain was partially restored and symmetry completely restored within 30 days after the plug, but only for the plateau response. The overshoot in eye velocity remained asymmetric. The asymmetry was independent of stimulus velocity throughout the known linear velocity range of primary vestibular afferents. Sinusoidal rotation at 0.05-8 Hz revealed that, within this range, the persistent asymmetry was significant only at frequencies above 2 Hz. Asymmetry was independent of the peak head acceleration over the range of 50-500 degrees/s2. When both horizontal canals were plugged, a small residual VOR was observed, suggesting residual signal transduction by plugged semicircular canals. However, transduction by plugged canals could not explain the enhancement of the VOR gain, at high frequencies, for rotation away from the plugged side compared with rotation toward the plug. Also, the high-frequency asymmetry was present after recovery from a unilateral labyrinthectomy. These results suggest that high-frequency asymmetry after unilateral damage is not due to residual function in the plugged canal. The findings are discussed in the context of a bilateral model of the VOR that includes central filtering.

Improved High-Density Phase-Change Recording

By using a simple write strategy we have found that a wide range of linear velocities can be covered for direct overwrite in high-density phase-change recording. This is especially advantageous for data recording where the application of constant angular velocity facilitates fast seek and short random-access times. In the case of repeated overwriting, material flow will limit the number of cycles, particularly if a fixed pseudo-random data pattern is used. We studied how a random bit shift can reduce this problem and found that a relatively large shift of up to 100 bytes was required. Using these techniques in an optimized disc structure we achieved more than 100,000 overwrite cycles on a 2.6 Gbyte 12 cm phase-change disc.

Extension of Linear-Velocity Margin in Phase-Change Optical Recording with Variable-Pulse Compensation

Using a variable-pulse compensation method, it was demonstrated that a phase-change optical disk consisting of a stoichiometric Ge2Sb2Te5 active layer and a fixed rapid cooling multilayer structure, which was designed for use at high linear velocity of over 5 m/s, exhibited a satisfactory read/write performance for a wide range of linear velocity, 1.4 m/s–10 m/s. The variable-pulse compensation method includes a variable-pulse division strategy in accordance with the linear velocity in pulse-width modulation recording. For recording an amorphous mark which is nT length (n: integer, T: the length of one clock cycle), the pulse duration of each divided writing pulse in the nT period was reduced and laser power was optimized at lower linear velocity to suppress the undesirable heat accumulation in the laser-irradiated area that leads to shrinking the amorphous mark. This assures exact control of molten area formation and its cooling process to obtain clear edges of amorphous marks, and overcomes the recrystallization around the mark in overwriting that is predominant in the low-linear-velocity regime.

Ion Exchange of Phenylalanine in Fluidized/Expanded Beds

Experimental and theoretical studies were carried out to investigate the performance of a batch, fluidized/expanded ion-exchange system. Exchange of phenylalanine on cation exchange resin was studied in the linear velocity range 5.5-39.8 cm/min. The breakthrough curves were obtained at various design and operating conditions with changes of column size, distributor, bed type, bed height, flow rate, and number of stages. The breakthrough data were analyzed by two theoretical models. A CSTR-type model which we called a lumped model fitted the data well when bed aspect ratio (bed height/bed diameter) was less than 1.5 and column diameter was less than 4 cm. We considered the fluidized bed as a bed that can be well simulated by the lumped model (uniform mixing), and the expanded bed as a bed where the lumped model fails because of reduced backmixing. Another model, which is adapted from a packed bed model (VERSE) with axial dispersion, film diffusion, and intraparticle diffusion, fitted the data for both fluidized beds and expanded beds successfully. Experimental and theoretical results showed the bed type changed from a fluidized bed to an expanded bed as the bed aspect ratio increases. The breakthrough curves for the expanded bed and a packed bed were almost identical except at very short times. When sieve plates were used as liquid distributors, the plate with more holes of a smaller size was most efficient. Mass transfer at different flow rates and the effects of bed type and multiple stages are discussed

Three-dimensional analysis of overwritable phase-change optical disks

Three-dimensional computer calculations which analyze time-transient behavior of heat conduction and phase-change kinetics in an InSbTe overwritable disk were made. To improve the calculation accuracy, thermal conductivities of thin-film materials and critical cooling rate for crystallizing the recording film were estimated. For realization of high-performance overwrite, it was found that the cooling conditions of writing and erasing processes should be controlled to match the critical cooling rate in a given linear velocity range. This could be achieved by optimal design of the disk structure.

Ge–Te–Sb Based Overwritable Phase Change Optical Disk

An overwritable recording medium conformed to the ISO format (CCS) has been developed on the basis of the phase change type recording material using the Ge–Te–Sb ternary alloy. This material achieved the bit error rate (BER) of less than 10-5 and phase margin of more than 40 nsec, which are sufficient for practical use as a digital data recording medium. The overwriting tests made clear the relationship between the digital and analog recording characteristics: erase ratio of more than 25 dB is required to realize the desired BER and the phase margin. Overwritability is achieved over the wide range of linear velocity from 1.4 m/s to 22.0 m/s by selecting appropriate composition areas of the ternary alloy. The crystallization and amorphization mechanisms are discussed in detail which have great effects both on the favorable alloy composition area according to the linear velocity and on the optimum bias power for digital data recording.

Stationäre phasen mit SiN bindung für die flügkeitschromatographie

 SiN bonded stationary phases for liquid chromatography The preparation of SiN bonded stationary phases for high-pressure liquid chromatography on the surface of silica with a specific surface area of 370 m 2/ g is described. The organic part of the stationary phase has a monomeric structure. In order to “modify” the selectivity to a required value, one or more functional groups, such as −COOH, −SO 3H, −NH 2, −CN or −NO 2, are introduced into the aliphatic chain. The spatial requirement of the organic “bristles” varies between 55 and 400 Å 2. Peak broadening, capacity ratios and mass transfer terms were determined in the linear velocity range 0.5–10 cm/sec with n-heptane, methanol and water as eluents. The change in the relative retention as a function of the eluent and of the functional groups is discussed.