Counting of Enzymatically Amplified Affinity Reactions in Hydrogel Particle-Templated Drops

Counting of numerous compartmentalized enzymatic reactions underlies quantitative and high sensitivity immunodiagnostic assays. However, digital enzyme-linked immunosorbent assays (ELISA) require specialized instruments which have slowed adoption in research and clinical labs. We present a lab-on-a-particle solution to digital counting of thousands of single enzymatic reactions. Hydrogel particles are used to bind enzymes and template the formation of droplets that compartmentalize reactions with simple pipetting steps. These hydrogel particles can be made at a high throughput, stored, and used during the assay to create ~500,000 compartments within 2 minutes. These particles can also be dried and rehydrated with sample, amplifying the sensitivity of the assay by driving affinity interactions on the hydrogel surface. We demonstrate digital counting of β-galactosidase enzyme at a femtomolar detection limit with a dynamic range of 3 orders of magnitude using standard benchtop equipment and experiment techniques. This approach can faciliate the development of digital ELISAs with reduced need for specialized microfluidic devices, instruments, or imaging systems.

Laser Self-Trapping in Optical Tweezers for Nonlinear Particles

The optical tweezers are used to trap the particles embedded in a suitable fluid. The optical trap efficiency is significantly enhanced for nonlinear particleswhich response to the Kerr effect. The optical transverse gradient force makes these particles’ mass density in trapping region increasing, and the Kerr medium can be created. When the laser Gaussian beam propagates through it, the self-focusing, and consequentlyself-trappingcan appear. In this paper, a model describing the laser self-trapping in nonlinear particle solution of optical tweezers is proposed. The expressions for the Kerr effect, effective refractive index of nonlinear particle solution and the intensity distribution of reshaped Gaussian laser beam are derived, and the self-trapping of laser beam is numerically investigated. Finally, the guide properties of nonlinear particles-filled trapping region and guiding condition are analysed and discussed.

Quaternionic quantum particles: new solutions

If Ψ is a quaternionic wave function, then iΨ ≠ Ψi. Thus, there are two versions of the quaternionic Schrödinger equation (QSE). In this article, we present the second possibility for solving the QSE, following from a previous article. After developing the general methodology, we present the quaternionic free particle solution and the scattering of the quaternionic particle through a scalar barrier.

Alteration of Physical and Chemical Properties of Clays Subjected to Pressure

Clays represent complex polymineral formations. The properties of clays, including sorption, are largely determined by the structure of their crystal lattice, mineral composition and particle size distribution, as well as by environmental conditions. The mineral composition of clays is represented by the energy on the surface of particles; and the particle size distribution is represented by the active surface area of particles. These two complex parameters mainly determine the sorption activity of clays. To change the sorption activity of clays, the latter are subjected to mechanical treatments, thermal modifications, and chemical activations with the use of chemical agents such as acids, alkalis, salts at various exposure times. Therefore, a study of patterns of changes in the structure and sorption properties of clays subjected to pressure was conducted. Experimental studies have shown that if kaolin is subjected to pressure, defects are formed in the structural pack of kaolinite mineral due to the removal of Al3+, Fe3+/2+, Mg2+, Si4+ ions from it. In this case, pressure has the maximum influence on the removal of Al3+ ions from the pack. As a result of the removal of ions, the formation of the defects deforms the crystal lattice of kaolinite. Data obtained through IR spectroscopy confirm the increase of defectiveness (irregularity) of the structure of kaolinite. It has been revealed that when kaolin is subjected to a pressure of 0–150 MPa, the sorption activity mostly depends on рН of the diffuse layer particle solution ZрН = 73 % and crystallite defectiveness degree ZМк = 24 %. The specific surface area of particles ZSsa = 1 % and kaolinite pack defectiveness Zс = 2 % do not have any significant influence on sorption. If kaolin is subjected to a pressure of 150–800 MPa, kaolin sorption activity mostly depends on kaolinite pack defectiveness Zс = 74 % and crystallite pack defectiveness ZМк = 19 %. The specific surface area of particles ZSsa = 3 % and рН of the diffuse layer particle solution ZрН =4 % do not have any significant influence on sorption.

Quantifying Respiratory Airborne Particle Dispersion Control Through Improvised Reusable Masks: The Physics of Non-Pharmaceutical Interventions for Reducing SARS-COV-2 (COVID-19) Airborne Transmission

Background: For much of the SARS-CoV-2 (COVID-19) pandemic, many countries have struggled to offer definitive guidance on the wearing of masks or face coverings to reduce the highly infectious disease transmission resulting from a lack of compelling evidence on the effectiveness of communities wearing masks, and slow acceptance that aerosols are a primary SARS-CoV-2 disease transmission mechanism. Recent studies have shown that masks have been effective in several countries and populations, leaving only a lack of quantitative data on the control of airborne dispersion from human exhalation. This current study specifically has the objective to quantify the effectiveness of non-medical grade washable masks or face coverings in controlling airborne dispersion from exhalation (both droplet and aerosol) by measuring changes in direction, particle cloud velocities, and concentration. Design: This randomized effectiveness study used a 10% NaCl nebulized polydisperse particle solution (0.3 um up to 10 um in size) delivered by an exhalation simulator to conduct 94 experiment runs with combinations of 8 different fabrics, 5 mask designs, and airflows for both talking and coughing. Multiple particle sensors were instrumented to measure reduction in aerosol dispersion. Results: Three-way multivariate analysis of variance establishes that fabric, mask design, and exhalation breath level have a statistically significant effect on changing direction, reducing velocity, or concentrations of airborne particles (Fabric: P = < .001, Wilks' Λ = .000; Mask design: P = < .001, Wilks' Λ = .000; Breath level: P = < .001, Wilks' Λ = .004). There were also statistically significant interaction effects between combinations of all primary factors. Conclusions and Relevance: The application of facial coverings or masks can significantly reduce the airborne dispersion of aerosolized particles from exhalation by diffusing the particle cloud direction and slow down its travel speed. Consequently, the results indicate that wearing masks when coupled with social distance can decrease the potentially inhaled dose of SARS-CoV-2 aerosols or droplets especially where infectious contaminants may exist in shared air spaces. The conclusion is well aligned with the concept of "time-distance-shielding" from hazardous materials emergency response. However, the effectiveness varies greatly between the specific fabrics and mask designs used.

Interaction-tailored organization of large-area colloidal assemblies

Colloidal lithography is an innovative fabrication technique employing spherical, nanoscale crystals as a lithographic mask for the low cost realization of nanoscale patterning. The features of the resulting nanostructures are related to the particle size, deposition conditions and interactions involved. In this work, we studied the absorption of polystyrene spheres onto a substrate and discuss the effect of particle–substrate and particle–particle interactions on their organization. Depending on the nature and the strength of the interactions acting in the colloidal film formation, two different strategies were developed in order to control the number of particles on the surface and the interparticle distance, namely changing the salt concentration and absorption time in the particle solution. These approaches enabled the realization of large area (≈cm2) patterning of nanoscale holes (nanoholes) and nanoscale disks (nanodisks) of different sizes and materials.

Geometric Unification of Electromagnetism and Gravitation

Using four equations, a recently proposed classical field theory that geometrically couples electromagnetism to gravitation in a fundamentally new way is reviewed. Maxwell&rsquo;s field equations are a consequence of the new theory as are Einstein&rsquo;s field equations augmented by a term that can replicate both dark matter and dark energy. To emphasize the unification brought to electromagnetic and gravitational phenomena by the new theory specific solutions are investigated: a spherically-symmetric charged particle solution, a cosmological solution representing a homogeneous and isotropic universe, and solutions representing electromagnetic and gravitational waves. A unique feature of the new theory is that both charge and mass density are treated as dynamic fields, this as opposed to their treatment in the classical Maxwell and Einstein field equations where they are introduced as external entities. This feature suggests a procedure for quantizing the mass, charge and angular momentum that characterize particle-like solutions. Finally, antimatter, which is naturally accommodated by the new theory, and its interaction with a gravitational field is investigated.