Affinity analysis of a protein-aptamer complex using nonequilibrium capillary electrophoresis of equilibrium mixtures

We propose a new method that allows the use of low-affinity aptamers as affinity probes in quantitative analyses of proteins. The method is based on nonequilibrium capillary electrophoresis of the equilibrium mixture (NECEEM) of a protein with its fluorescently labeled aptamer. In general, NECEEM of a protein with a fluorescently labeled aptamer generates an electropherogram with three characteristic features: two peaks and an exponential curve. Two peaks correspond to (i) the equilibrium amount of free aptamer in the equilibrium mixture and (ii) the amount of the protein-aptamer complex that remains intact at the time of detection. The exponential part is ascribed to the complex decaying during separation under nonequilibrium conditions. Simple analysis of the three features in experiments with known concentrations of the protein can be used for the determination of the equilibrium dissociation constant, Kd, of the aptamer-protein complex. Similar analysis of the three features in the experiment with unknown concentration of the protein and known Kd value allows the determination of the protein concentration. In this proof-of-principle work, the NECEEM method was applied to the analysis of thrombin using a fluorescein-labeled aptamer under the conditions at which the protein-aptamer complex completely decayed during the separation. We demonstrated that, despite the decay, as few as 4 x 10(6) molecules of the protein could be detected with NECEEM without sacrificing the accuracy. This sensitivity is comparable with that reported by others for the aptamer-based equilibrium method. Thus, the proposed NECEEM-based method allows the use of aptamers for highly sensitive affinity analysis of proteins even when protein-aptamer complexes are unstable.     

Approximations for Maximum Transportation with Permutable Supply Vector and Other Capacitated Star Packing Problems

We describe approximation algorithms for the maximum transportation with permutable supply vector and related problems.     

Mutual diffusion in aqueous gel solutions

Concentration relations for mutual diffusion coefficients D_m(C) in water of polyelectrolyte gelatin macromolecules at different temperatures were studied by optical interferometry. It is shown that D_m(C) values are in agreement with scaling predictions and are similar to those observed for solutions of neutral macromolecules under θ-conditions. However, they are greatly influenced by the square-law term C², having a correlation to the conventional scaling law D_m ∝? C, and the mobility of solution components is influenced by physical gelation processes under certain thermodynamic conditions. It is demonstrated that the temperature relation of the diffusion coefficient at infinite dilution D₀(C → 0) for the three gelating samples with various physico-chemical properties can be described by a universal function.     

Dielectric constant of barium titanate/cyanoethyl ester of polyvinyl alcohol composite in comparison with the existing theoretical models

A unique method has been introduced to measure the dielectric constant of polymer/ceramic composites using an effective medium instead of using the general methods of preparing bulk sintered pellets or films. In this work, a new and a simple method has been applied to measure the dielectric constant of polyvinyl cyanoethylate/barium titanate composites. The results are obtained by dispersing the ceramic powders in the polymer of a relatively low dielectric constant value. The dielectric constant of the composites is measured with varying ceramic volume percentages. The obtained results are compared with the many available theoretical models that are generally in practice to predict the dielectric constant of the composites. Then these results are extrapolated to comprehend the dielectric constant values of ceramic particles as these values form the base for the design of the composite. The precision and simplicity of the method can be exploited for predictions of the properties of nanostructure ferroelectric polymer/ceramic composites.     

Design and Calibration of a mm-Wave Personal Exposure Meter for 5G Exposure Assessment in Indoor Diffuse Environments

For the first time, a mm-wave personal exposure meter (mm-PEM) for the 5th generation of mobile networks (5G) exposure assessment in indoor diffuse fields is presented. The design is based on simulations and on-phantom calibration measurements in a mm-wave reverberation chamber (RC) at 60 GHz. The mm-PEM consists of an array of nine antennas on the body. Using the mm-PEM, the incident power density (IPD) is measured in the unloaded RC, for the antenna(s) on the phantom and RC loaded with phantom. The uncertainty of the mm-PEM is then determined in terms of its response, which is defined as the ratio of antenna aperture for the above measurement scenarios. Using nine antennas, the designed meter has a response of 1.043 (0.17 dB) at 60 GHz, which is very close to 1 (0 dB), the desired ideal response value. The mm-PEM measured an IPD of 96.6 W m^??2 at 60 GHz in the RC, for an input power of 1 W. In addition, the average absorption cross-section of the phantom is determined as 225 cm², which is an excellent agreement with its physical dimensions.     

Terahertz Switching Focuser Based on Thin Film Vanadium Dioxide Zone Plate

In this paper, we propose a switchable focuser device based on a Fresnel zone plate (FZP) structure for terahertz (THz) applications. Each FZP contains seven rings, etched in thin VO₂ film with the designed focal lengths of 50 and 100 mm for 3.7-THz frequency. Temperature-induced VO₂ phase transition leads to the change in dielectric susceptibility of the material, which allows one to switch on and off the focusing properties of the device. The devices were tested with radiation of 3.1 and 3.7 THz emitted by quantum cascade lasers. Experimental results were compared with numerical simulations. In this article, we compare the FZP based on VO₂ films with different properties and show that a thicker VO₂ film reveals higher focusing efficiency, while a thinner one reveals a higher modulation ratio for the peak intensity at the focal point of FZP. We demonstrate experimentally the near-diffraction-limited size of the beam in the focal point of the device. Switching between two phase states of the VO₂ films results in up to the 38-fold change of intensity in the focal point.     

Sol–gel derived CeO2/α‐Al2O3 bilayer thin film as an anti‐coking barrier and its catalytic coke oxidation performance

A CeO₂/α‐Al₂O₃ bilayer was coated on a high temperature alloy (Incoloy 800H) by sol–gel dip‐coating and was evaluated for its potential as an anticoking barrier and coke oxidation catalyst. The bilayer effectively functioned as a barrier to metal surface catalyzed coking. The film prevented filamentous catalytic coking via blocking surface active metallic sites on the Incoloy substrate. Furthermore, the bilayer reduced the oxidation temperature of pyrolytic coke deposited on the film surface as compared to a bare oxidized Incoloy substrate, mostly owing to the oxidation catalytic activity of the CeO₂ layer. Finally, it is demonstrated that the presence of the α‐Al₂O₃ buffer layer is critically important to the overall performance. Without the α‐Al₂O₃ layer, a CeO₂ layer nearly completely lost both its barrier and oxidation catalytic functions. It is presumed that metallic species migrating from the substrate during high temperature treatments are responsible for the CeO₂ deactivation, likely by blocking catalytic sites on the CeO₂ surface. © 2018 American Institute of Chemical Engineers AIChE J, 64: 4019–4026, 2018     

Microscopic dose to lung from inhaled alpha emitters in humans

Because of the short range of alpha particles in tissue, the degree of uniformity of irradiation of the lung varies greatly depending on the form of the inhaled material. Animal studies have shown that the degree of dose uniformity influences the risk of lung cancer. This study investigates the radiation dose distribution of plutonium in human lung. Numerical maps of tissue configuration and target cell locations are obtained from histological sections of human lung tissue stained to enhance the identification of putative cell types for parenchymal lung cancers, i.e. alveolar type II cells and Clara cells. Monte Carlo simulations are used to obtain dose distribution around individual particles, and these distributions are used to compute dose distribution in volumes of lung tissue. Lung dose is characterised both by the degree of non-uniformity of irradiation and the relative degree of irradiation of all tissue versus the special cells of interest.