Responsive polymers for analytical applications: A review

Stimuli-responsive polymers are capable of translating changes in their local environment to changes in their chemical and/or physical properties. This ability allows stimuli-responsive polymers to be used for a wide range of applications. In this review, we highlight the analytical applications of stimuli-responsive polymers that have been published over the past few years with a focus on their applications in sensing/biosensing and separations. From this review, we hope to make clear that while the history of using stimuli-responsive polymers for analytical applications is rich, there are still a number of directions to explore and exciting advancements to be made in this flourishing field of research.     

Optimal Error Estimates for Analytic Continuation in the Upper Half‐Plane

Analytic functions in the Hardy class H² over the upper half‐plane ?₊ are uniquely determined by their values on any curve Γ lying in the interior or on the boundary of ?₊ . The goal of this paper is to provide a sharp quantitative version of this statement. We answer the following question: Given f of a unit H² ‐norm that is small on Γ (say, its L² ‐norm is of order ? ), how large can f be at a point z away from the curve? When Γ ? ??₊ , we give a sharp upper bound on ∣f(z)∣ of the form ?^γ , with an explicit exponent γ = γ(z) ∈ (0, 1) and explicit maximizer function attaining the upper bound. When Γ ? ?₊ we give an implicit sharp upper bound in terms of a solution of an integral equation on Γ . We conjecture and give evidence that this bound also behaves like ?^γ for some γ = γ(z) ∈ (0, 1) . These results can also be transplanted to other domains conformally equivalent to the upper half‐plane. © 2020 Wiley Periodicals, Inc.     

The influence of hydrochloric acid treatment and temperature on the electro-physical properties of super-thin basalt fibers

Electro-physical parameters of super-thin basalt fiber (STBF) from Armenian basalt rocks are measured before and after hydrochloric acid treatment. It is shown that specific resistance and dielectric parameters of super-thin basalt fiber change essentially after hydrochloric acid treatment. The temperature dependence of these parameters was studied too. The probable cause of the change is an increase in the total amount of pores and modification of the share of pores of various sizes in STBF, followed by an increase of absorption of water molecules from the ambient medium. The results (in both alternating and direct electric fields) are interpreted within the framework of the dipole-relaxation mechanism of the polarization of water molecules in STBF pores.     

Low-temperature synthesis and characteristics of fractal graphene layers

Large scale fractal graphene layers are obtained by complex method of liquid phase exfoliation and self-organization. Atomic force microscopy (AFM) is used to study the surface properties of formed layers and to assess their thickness. Surface potential of graphene and potential transition between the graphene and substrate is measured by Kelvin probe method. The influence of the effect of dielectric confinement on the optical properties of graphene is discussed in this work. Raman scattering spectra were used for structural analysis and assessment of the level of defects. Current-voltage characteristics of graphene ribbons were measured and discussed for different number of layers.     

Dyes and Redox Couples with Matched Energy Levels: Elimination of the Dye‐Regeneration Energy Loss in Dye‐Sensitized Solar Cells

In dye‐sensitized solar cells (DSSCs), a significant dye‐regeneration force (ΔG_reg⁰≥0.5 eV) is usually required for effective dye regeneration, which results in a major energy loss and limits the energy‐conversion efficiency of state‐of‐art DSSCs. We demonstrate that when dye molecules and redox couples that possess similar conjugated ligands are used, efficient dye regeneration occurs with zero or close‐to‐zero driving force. By using Ru(dcbpy)(bpy)₂²⁺ as the dye and Ru(bpy)₂(MeIm)₂^3+//2+ as the redox couple, a short‐circuit current (J_sc) of 4 mA cm^?2 and an open‐circuit voltage (V_oc) of 0.9 V were obtained with a ΔG_reg⁰ of 0.07 eV. The same was observed for the N3 dye and Ru(bpy)₂(SCN)₂^1+/0 (ΔG_reg⁰=0.0 eV), which produced an J_sc of 2.5 mA cm^?2 and V_oc of 0.6 V. Charge recombination occurs at pinholes, limiting the performance of the cells. This proof‐of‐concept study demonstrates that high V_oc values can be attained by significantly curtailing the dye‐regeneration force.     

Hopf bifurcation in structural population models

We study a nonlinear PDE problem motivated by the peculiar patterns arising in myxobacteria, namely, counter‐migrating cell density waves. We rigorously prove the existence of Hopf bifurcations for some specific values of the parameters of the system. This shows the existence of periodic solutions for the systems under consideration. Copyright © 2016 John Wiley & Sons, Ltd.