High Linear Velocities Research Articles

Doing more with less: Evaluation of the use of high linear velocities in preparative supercritical fluid chromatography

The evaluation of higher than typical linear velocities is discussed for supercritical fluid chromatographic purifications on the preparative scale. SFC separation efficiency suffers far less at high linear velocities than HPLC by the rapid mass transfer of analytes carried by compressed CO2 through the stationary phase. The technique is discussed using chiral test compounds and columns. In many cases, running at high linear velocities can yield significant time savings and decreased consumption of mobile phase solvent, while also lowering energy consumption. Within the practical limitations of commercial instrumentation, using 20 μm particles can aid in achieving higher linear velocities not attainable with smaller 5 μm particles, particularly when running with high percentages of organic co-solvent. Use of larger particles for the stationary phase also lowers the associated column cost. These benefits can yield an overall purification process that is more productive and environmentally friendly.

Gas content on dual-flow plate in a combined contact device

A study of dual-flow plates with a large free section, which are proposed to be installed in combination with a package of a corrugated nozzle with an oblique corrugation, is carried out. The package of the nozzle is installed above the dual-flow plate as a separator of the gas-liquid layer, thus, the package of the nozzle is the second zone of contact of the phases in the conditions of mass transfer. Such a combined contact device allows high linear gas velocities.It has been established that the hydrodynamic characteristics of the combined contact device are practically independent of the diameter of the column apparatus under load conditions in the liquid phase characteristic of rectification processes

Ultra-High-Throughput Multi-Parametric Imaging Flow Cytometry

I will present a microfluidic imaging flow cytometer incorporating stroboscopic illumination, for blur-free cellular analysis at throughputs exceeding 100,000 cells per second. By combining passive (inertial or viscoelastic) focusing of cells in parallel microchannels with stroboscopic illumination, such chip-based cytometers are able to extract multi-colour fluorescence and bright-field images of single cells moving at high linear velocities. This in turn allows accurate sizing of individual cells, intracellular localization and analysis of heterogeneous cell suspensions. The method is showcased through the rapid enumeration of apoptotic cells, high-throughput discrimination cell cycle phases and localization of p-bodies.

Smartphone-based apparatus for measuring upconversion luminescence lifetimes

Luminescence lifetime detection plays an important role in time-resolved detection and research. However, the traditional instruments always require expensive detectors such as time-correlated single photon counter or streak camera. Herein, a low-cost and miniaturized apparatus for measuring upconversion luminescence lifetimes was developed by using a smartphone equipped with a 980 nm CW laser and a motor. When the motor was driving the sample circling at a high linear velocity, the excited sample would emit a luminescence arc, which could be photographed by the phone camera. The rotating rate could be measured by a tuner APP and then used for transferring arc length to delay times. By analyzing the grayscale distribution of the luminescence arc, the luminescence decay curve was obtained, which was then used for exponential fit and calculating lifetimes. The images captured by different smartphones revealed similar lifetime values, suggesting a wide universality of this method. The whole system was not only remarkably cheaper but also more miniaturized than traditional instruments for measuring luminescence lifetimes, indicating the promising applications in point of care testing for time-resolved luminescence detection for bioanalysis and disease diagnosis.

Evaluation of protein separations based on hydrophobic interaction chromatography using polyethylene terephthalate capillary-channeled polymer (C-CP) fiber phases

Poly(ethylene terephthalate) (polyester, PET) capillary-channeled polymer fibers are used as the stationary phase for the separation of a synthetic protein mixtures composed of cytochrome c, myoglobin, ribonuclease A, lysozyme, α-chymotrypsinogen A, α-chymotrypsin and holo-transferrin. Polyester is a useful phase for HIC, having a mixed alkyl and aromatic backbone to yield mildly hydrophobic properties, an aromatic functionality allowing for π-π interactions, and carboxylate end groups adding hydrophilicity. In addition, the lack of extraneous hydrophobic ligands or charged surface species alleviates secondary interactions between proteins and common support phases. Breakthrough experiments with lysozyme solution were operated at various loading flow rates (0.1–0.5 mL min−1) and protein concentrations (0.025–1.0 mg mL−1). Dynamic binding capacity (DBC) was plotted and results fit to two isotherm models: Langmuir and Freundlich. Column stability and reproducibility were tested via 10 continuous lysozyme load/elution cycles. Organic solvents, acetonitrile and isopropanol, were tested with proportions ranging from 0 to 40% in the elution buffer, aiding protein elution, with the best separation efficiency employing ∼15–20% organic modifier. Resolution was evaluated at solvent pH values between 5 and 7.5, flow rates ranging from 0.2 to 0.6 mL min−18−1) and at gradient slopes between 5 and 16.7% B min−1. Optimum resolution and fast analysis times were achieved employing a steep gradient using high linear velocities. Finally, a comparison of separation efficiency between a commercial HIC phase (TSKgel Phenyl-5 P W) and the PET fiber column is presented for a standard, six protein mixture, using optimal operation conditions for each column type.

Clinical features and early detection of sport-related concussion.

AimAthletes who suffer sport‐related concussions but continue playing have a high probability of experiencing more severe symptoms with any subsequent concussion. This study used data from the authors’ clinical department to retrospectively investigate the clinical characteristics of sport‐related concussion and factors associated with delays in examinations.MethodsThe study included 38 patients with sport‐related concussions who were treated at the authors’ hospital. The sports during which the injuries occurred, occasions of injury, factors affecting the time from injury until examination at hospital, and prognoses were evaluated retrospectively.ResultsSport‐related concussions most frequently occurred in rugby and judo, where tackling, throwing, and other types of physical contact can result in impacts to the head region at high angular or linear velocity with acceleration. Some subjects showed consciousness disturbance and/or clear subjective symptoms immediately after the injury and were therefore examined at the hospital rapidly. However, other subjects who suffered amnesia or less obvious symptoms continued to play after the injury and had delayed examinations. In addition, there was a tendency for examinations to be delayed when an on‐site physician was present.ConclusionsIn contact sports where injury‐resulting events occur, such as impacts to the head at high angular or linear velocity with acceleration, athletes should be immediately withdrawn from play and evaluated for concussion, even if there are no obvious head injuries or symptoms. The immediate ascertainment of symptoms after physical contact would improve the rapid detection of sport‐related concussion.

The specific features of high-velocity magnetic fluid sealing complexes

The factors, which are insignificant at small velocities, become rather considerable with increasing the shaft surfacevelocity as far as the magnetic fluid sealing complex (MFSC) is concerned They impact both on the pressure drop restrained by the sealer and on MFS operational resource. The mutual influence of magnetic and centrifugal forces in the gap of the high-speedmagnetic fluid sealing complex is analyzed. A method for reducing the effect of centrifugal forces on the performance of a complex by placing magnetic flux concentrators on a rotating shaft with the use of multi-physical modeling is studied. It is shown that thelocation of the magnetic flux concentrators on the shaft results in the decrease in the magnetic field drop under the last outer tooth by 10%. It is also shown that the location of magnetic flux concentrators on the shaft reduces the value of the vortex velocity in theend part of the sealer, the directions of the vortex and the magnetic induction vector are opposite each other. The obtained results allowed to expand the field of application of magneto-liquid hermetic complexes at high linear velocities in the gap and were used inthe development of the design of the sealing gas-blowing complex, working on coke oven gas.

Overload Effects in Reversed Phase Protein Separations using Capillary-Channeled Polymer Fiber Columns.

In preparative chromatography, overloading effects are a fact of life. However, peak distortion is problematic in analytical scale chromatography, especially in the case of bio-macromolecule separations. Capillary-channeled polymer fibers have been employed for fast protein separations in reversed phase, ion exchange, and hydrophobic interaction liquid chromatography. Although the primary advantage of the phase is operation at high linear velocities (~100 mm s-1 ) without van Deemter C-term limitations, the limited specific surface area (<5 m2 g-1 ) suggests that a thorough understanding of overloading effects is needed. We evaluate important factors (injected mass and volume) affecting overload in terms of peak height, width and shape (asymmetry). Overload conditions readily apparent as the peak shape changes from a Gaussian distribution to a left-triangle with slight tailing; more-or-less classical overload behavior. Three methods were used to compute column efficiency in terms of plate counts (N), including the area height, half-height, and the Dorsey-Foley approaches. The half-height method is best-suited for describing column overload, accounting for peak distortion and achieving high levels of consistency. The limiting plate count (N0 ) and the column sample loading capacity (ω0.5 ) were key metrics to characterize overall column performance. Peak capacity (P) was used to assess gradient elution separation performance. Increased flow rates and column length result in enhanced loading capacity. pH mismatch between the sample matrix and the mobile phase, a common cause of protein overload with other phases, was not responsible for distorted peak shapes unless the solvent pH is close to the pI of protein samples.

Attitude determination sensor for low Earth orbit satellite based on Lorentz force

Spacecraft attitude determination is a crucial task in attitude control subsystems. It provides the necessary feedback to close the control loop. Several sensors such as star trackers, Sun sensors, and horizon sensors are used for this purpose. The development of other methods can help control engineer with newer options to design their systems. Here, an innovative sensor for determining the attitude of a spacecraft is presented. The proposed sensor measures the Lorentz force vector due to the interaction between the magnetic field of the Earth, and the high linear velocity of the spacecraft. This sensor is composed of three series of orthogonal variable capacitors. The capacitors are connected in parallel to increase the total capacitance. The capacitors have movable plates which actuated by alternating current with specific frequency. Due to very high speed of spacecraft relative to magnetic field of earth in low orbit, the Lorentz force is exerted on the charges of the capacitor plates. The plates have same velocity as the spacecraft does. The applied Lorentz force to the plates affects their motion so that the harmonic can be seen in the output. Measuring the amplitude of the mentioned harmonic results in measurement of a component of the Lorentz force in the direction of capacitors. Installing the three capacitors orthogonally can measure the three rectangular components of the Lorentz force. This vector will be in the body frame of the spacecraft. The two-plate and three-plate capacitor are the two different proposed mechanisms and their performance is compared. Once the Lorentz force is known as a vector in the body frame, it can be applied along with data from another sensor to determine the attitude of the spacecraft. Based on simulation results, achievable resolution is better than 3°, which can be improved by further research.

Thin-felt microfibrous-structured Au-α-Fe2O3/ns-γ-Al2O3/Al-fiber catalyst for high-throughput CO oxidation

Gold nanoparticles supported on Fe2O3 are a promising type of catalyst for CO oxidation. One challenge for their application in the real world is developing novel monolithic catalytic packings to meet the fundamental criteria (for example, high catalyst utilization efficiency and low pressure drop) needed for such high-throughput reaction process. Herein, a highly active and efficient thin-felt microfibrous-structured Au-α-Fe2O3/ns-γ-Al2O3/Al-fiber catalyst with unique form factor and high permeability is fabricated for the low-temperature CO oxidation. Initially, thin-felt Al-fiber felt (60 μm diameter; 85 vol% voidage) undergoes a steam-only oxidation and calcination to create a 0.7 μm mesoporous layer of γ-Al2O3 nanosheets (ns-γ-Al2O3) along with the Al-fiber. Subsequently, α-Fe2O3 is hydrothermally grown onto the ns-γ-Al2O3 layer followed by Au nanoparticle deposition via urea-assistant deposition-precipitation method. As-resulted microfibrous-structured Au-α-Fe2O3/ns-γ-Al2O3/Al-fiber catalysts effectively and efficiently couple the low-temperature activity and improved water vapor tolerance with enhanced catalyst accessibility and high permeability. The promising microfibrous-structured catalyst with only 0.14 wt% Au and 1.4 wt% α-Fe2O3 is capable of fully or 40% oxidizing CO into CO2 at 25 °C or 0 °C for a feed gas of 2 vol% CO and 0.3 vol% water vapor in air at a high linear velocity of 0.7 cm s−1, using a high gas hourly space velocity of 25,200 mL g−1 cat h−1. Moreover, the microfibrous-structured catalyst performs robustly for at least 232 h under the changeable temperature conditions. Interestingly, 3D hierarchical porous flake structure of α-Fe2O3 nano-sheets is detected other than the irregular micron-sized particles, leading to a 3-fold increase in the intrinsic activity (TOF of 0.46 s-1 for the Au-α-Fe2O3/ns-γ-Al2O3/Al-fiber vs. 0.11 s−1 for the Au-α-Fe2O3 powder at 25 °C).

Investigating the Effect of Column Geometry on Separation Efficiency using 3D Printed Liquid Chromatographic Columns Containing Polymer Monolithic Phases.

Effect of column geometry on the liquid chromatographic separations using 3D printed liquid chromatographic columns with in-column polymerized monoliths has been studied. Three different liquid chromatographic columns were designed and 3D printed in titanium as 2D serpentine, 3D spiral, and 3D serpentine columns, of equal length and i.d. Successful in-column thermal polymerization of mechanically stable poly(BuMA-co-EDMA) monoliths was achieved within each design without any significant structural differences between phases. Van Deemter plots indicated higher efficiencies for the 3D serpentine chromatographic columns with higher aspect ratio turns at higher linear velocities and smaller analysis times as compared to their counterpart columns with lower aspect ratio turns. Computational fluid dynamic simulations of a basic monolithic structure indicated 44%, 90%, 100%, and 118% higher flow through narrow channels in the curved monolithic configuration as compared to the straight monolithic configuration at linear velocities of 1, 2.5, 5, and 10 mm s-1, respectively. Isocratic RPLC separations with the 3D serpentine column resulted in an average 23% and 245% (8 solutes) increase in the number of theoretical plates as compared to the 3D spiral and 2D serpentine columns, respectively. Gradient RPLC separations with the 3D serpentine column resulted in an average 15% and 82% (8 solutes) increase in the peak capacity as compared to the 3D spiral and 2D serpentine columns, respectively. Use of the 3D serpentine column at a higher flow rate, as compared to the 3D spiral column, provided a 58% reduction in the analysis time and 74% increase in the peak capacity for the isocratic separations of the small molecules and the gradient separations of proteins, respectively.

High-resolution separation of neodymium and dysprosium ions utilizing extractant-impregnated graft-type particles

An efficient method for rare metal recovery from environmental water and urban mines is in high demand. Toward rapid and high-resolution rare metal ion separation, a novel bis(2-ethylhexyl) phosphate (HDEHP)-impregnated graft-type particle as a filler for a chromatography column is proposed. To achieve rapid and high-resolution separation, a convection-flow-aided elution mode is required. The combination of 35μm non-porous particles and a polymer-brush-rich particle structure minimizes the distance from metal ion binding sites to the convection flow in the column, resulting in minimized diffusional mass transfer resistance and the convection-flow-aided elution mode. The HDEHP-impregnated graft-type non-porous-particle-packed cartridge developed in this study exhibited a higher separation performance for model rare metals, neodymium (III) and dysprosium (III) ions, and a narrower peak at a higher linear velocity, than those of previous HDEHP-impregnated fiber-packed and commercially available Lewatit® VP OC 1026-packed cartridges.

A High-Sensitivity, Integrated Absorbance and Fluorescence Detection Scheme for Probing Picoliter-Volume Droplets in Segmented Flows.

Droplet-based microfluidic systems that incorporate flowing streams of pL-volume droplets surrounded by a continuous and immiscible carrier phase have attracted significant recent attention due to their utility in complex chemical and biological experimentation. Analysis of pL droplets, generated at kHz frequencies and moving at high linear velocities, is almost exclusively achieved using fluorescence-based detection schemes. To extend the applicability of such optical detection schemes, we herein report the development of a simple and cost-effective optofluidic platform, integrating liquid-core PDMS waveguides, that allows the accurate measurement of absorbance within individual pL-volume droplets moving within segmented flows. Using such an approach, differential measurements of "sample "and "reference" droplets can be acquired at 1 kHz and yield detection limits of 400 nM for fluorescein in water. Significantly, the presented technique enables simultaneous fluorescence and absorbance interrogation of rapidly moving droplets in a fully automated manner. Proof of principle is demonstrated through the titration and monitoring of pH gradients in real time.

Interactive Leader–Follower Consensus of Multiple Quadrotors Based on Composite Nonlinear Feedback Control

In this paper, an interactive leader-follower configuration of multiple quadrotors is considered, which means that the leaders can react with respect to the followers. In order to analyze the consensus of such a multiquadrotor system, an interaction matrix is proposed. The convergence condition of the trajectory tracking error is then proved to be related to the smallest eigenvalue of the interaction matrix. In order to achieve an aggressive formation, we develop a bounded composite nonlinear feedback-based formation controller with hyperbolic functions as a main contribution. Simulation and real-time experimental results show that the formation task is achieved with small overshoot and rapid response speed. Real-time experiments show four quadrotors following a circular reference trajectory with high linear velocity up to 2.7 m/s.

Tribological behavior and energy dissipation characteristics of nano-Al2O3-reinforced PTFE-PPS composites in sliding system

Nanoparticles are increasingly being used to improve the friction and wear performance of polymers. In this study, we investigated the tribological behavior and energy dissipation characteristics of nano-Al2O3-reinforced polytetrafluoroethylene-polyphenylene sulfide (PTFE-PPS) composites in a sliding system. The tribological behaviors of the composites were evaluated under different normal loads (100–300 N) at a high linear velocity (2 m/s) using a block-on-ring tester. Addition of the nano-Al2O3 filler improved the antiwear performance of the PTFE-PPS composites, and the friction coefficient increased slightly. The lowest wear rate was obtained when the nano-Al2O3 content was 3% (volume fraction). Further, the results indicated a linear correlation between wear and the amount of energy dissipated, even though the wear mechanism changed with the nano-Al2O3 content, independent of the normal load applied.

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.

Thermal Tunable Narrow Linewidth External Cavity Laser With Thermal Enhanced FBG

We demonstrated a mode-hop-free external cavity laser (ECL) design incorporating a semiconductor gain chip and a fiber Bragg grating (FBG) with enhanced thermal sensitivity. The compact ECL features a narrow linewidth of 35 kHz and a high linear thermal tuning velocity of 65 pm/°C (8.125 GHz/°C), which is six times higher than that of normal FBG-based ECLs.

Preparation of NbOx/SiO2-coated structured packing material and it's catalytic performance in the gas-phase Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam

Potential industrial applicability of a NbOx/SiO2 catalyst material was strongly improved by fixing μm-particles onto a structured packing. The granular catalyst displays a high catalytic performance in producing ε-caprolactam via gas-phase Beckmann rearrangement. However, applicability is strongly hampered because a high linear gas velocity and a small particle size are necessary to avoid diffusion limitations. These requirements would lead to an unacceptably high pressure drop in an industrial reactor. The novel NbOx/SiO2 structured packing catalyst displays, at high WHSV in a tube reactor, a constant high ε-caprolactam yield (96%) for at least 32h time-on-stream, without any indication of deactivation.

One step derivatization with British Anti-Lewsite in combination with gas chromatography coupled to triple-quadrupole tandem mass spectrometry for the fast and selective analysis of inorganic arsenic in rice

We developed a new fast and selective analytical method for the determination of inorganic arsenic (iAs) in rice by a gas chromatography – tandem mass spectrometry (GC-MS/MS) in combination with one step derivatization of inorganic arsenic (iAs) with British Anti-Lewsite (BAL). Two step derivatization of iAs with BAL has been previously performed for the GC-MS analysis. In this paper, the quantitative one step derivatization condition was successfully established. The GC-MS/MS was carried out with a short nonpolar capillary column (0.25 mm × 10 m) under the conditions of fast oven temperature ramp rate (4 °C/s) and high linear velocity (108.8 cm/s) of the carrier gas. The established GC-MS/MS method showed an excellent linearity (r2 > 0.999) in a tested range (0.2–100.0 μg L−1), ultra-low limit of detection (LOD, 0.08 pg), and high precision and accuracy. The GC-MS/MS technique showed far greater selectivity (22.5 fold higher signal to noise ratio in rice sample) on iAs than GC-MS method. The gas chromatographic running time was only 2.5 min with the iAs retention time of 1.98 min. The established method was successfully applied to quantify the iAs contents in polished rice. The mean iAs content in the Korean polished rice (n = 27) was 66.1 μg kg−1 with the range of 37.5–125.0 μg kg−1. This represents the first report on the GC-tandem mass spectrometry in combination with the one step derivatization with BAL for the iAs speciation in rice. This GC-MS/MS method would be a simple, useful and reliable measure for the iAs analysis in rice in the laboratories in which the expensive and element specific HPLC-ICP-MS is not available.

FEATURES OF 2017A AND AlSi9Mg ALUMINUM ALLOYS FRICTION STIR WELDED WITH ROOT-SIDE HEATING

Aluminum alloys 2017A and AlSi9Mg (hypo-eutectic silumin) were friction stir welded with a relatively high linear velocity (over 1 m/min) and use of an additional heat source from the root side of the weld. Macrostructure investigation (with high-resolution images) showed no effect of heating on weld quality. The welding process caused significant fragmentation of the secondary phases in the AlSi9Mg alloy. Furthermore, it was proven that the material above the weld nugget was not mixed and contained micro-defects that were not caused by welding. Also, it contained cavities on the boundaries between Si-particles and the matrix. Based on hardness distribution, a slight strengthening of the cast alloy was observed at the bottom and middle parts of the weld. However, the hardness of the 2017A alloy initially decreased and then increased due to natural aging. This means that the FSW process produced a metastable state in the alloy.