Optimal Time Decay of the Vlasov-Poisson-Boltzmann System in R3{\mathbb{R}}^3

The Vlasov-Poisson-Boltzmann System governs the time evolution of the distribution function for the dilute charged particles in the presence of a self-consistent electric potential force through the Poisson equation. In this paper, we are concerned with the rate of convergence of solutions to equilibrium for this system over ${\mathbb{R}}^3$. It is shown that the electric field which is indeed responsible for the lowest-order part in the energy space reduces the speed of convergence and hence the dispersion of this system over the full space is slower than that of the Boltzmann equation without forces, where the exact difference between both power indices in the algebraic rates of convergence is 1/4. For the proof, in the linearized case with a given non-homogeneous source, Fourier analysis is employed to obtain time-decay properties of the solution operator. In the nonlinear case, the combination of the linearized results and the nonlinear energy estimates with the help of the proper Lyapunov-type inequalities leads to the optimal time-decay rate of perturbed solutions under some conditions on initial data.Comment: 37 page

Electrophysiological characterization of drug response in hSC-derived cardiomyocytes using voltage-sensitive optical platforms

Introduction: Voltage-sensitive optical (VSO) sensors offer a minimally invasive method to study the time course of repolarization of the cardiac action potential (AP). This Comprehensive in vitro Proarrhythmia Assay (CiPA) cross-platform study investigates protocol design and measurement variability of VSO sensors for preclinical cardiac electrophysiology assays. Methods: Three commercial and one academic laboratory completed a limited study of the effects of 8 blinded compounds on the electrophysiology of 2 commercial lines of human induced pluripotent stem-cell derived cardiomyocytes (hSC-CMs). Acquisition technologies included CMOS camera and photometry; fluorescent voltage sensors included di-4-ANEPPS, FluoVolt and genetically encoded QuasAr2. The experimental protocol was standardized with respect to cell lines, plating and maintenance media, blinded compounds, and action potential parameters measured. Serum-free media was used to study the action of drugs, but the exact composition and the protocols for cell preparation and drug additions varied among sites. Results: Baseline AP waveforms differed across platforms and between cell types. Despite these differences, the relative responses to four selective ion channel blockers (E-4031, nifedipine, mexiletine, and JNJ 303 blocking IKr, ICaL, INa, and IKs, respectively) were similar across all platforms and cell lines although the absolute changes differed. Similarly, four mixed ion channel blockers (flecainide, moxifloxacin, quinidine, and ranolazine) had comparable effects in all platforms. Differences in repolarisation time course and response to drugs could be attributed to cell type and experimental method differences such as composition of the assay media, stimulated versus spontaneous activity, and single versus cumulative compound addition. Discussion: In conclusion, VSOs represent a powerful and appropriate method to assess the electrophysiological effects of drugs on iPSC-CMs for the evaluation of proarrhythmic risk. Protocol considerations and recommendations are provided toward standardizing conditions to reduce variability of baseline AP waveform characteristics and drug responses

Realization and Properties of Biochemical-Computing Biocatalytic XOR Gate Based on Enzyme Inhibition by a Substrate

We consider a realization of the XOR logic gate in a process biocatalyzed by an enzyme (here horseradish peroxidase: HRP), the function of which can be inhibited by a substrate (hydrogen peroxide for HRP), when the latter is inputted at large enough concentrations. A model is developed for describing such systems in an approach suitable for evaluation of the analog noise amplification properties of the gate. The obtained data are fitted for gate quality evaluation within the developed model, and we discuss aspects of devising XOR gates for functioning in "biocomputing" systems utilizing biomolecules for information processing

To see or not to see: investigating detectability of Ganges River dolphins using a combined visual-acoustic survey

Detection of animals during visual surveys is rarely perfect or constant, and failure to account for imperfect detectability affects the accuracy of abundance estimates. Freshwater cetaceans are among the most threatened group of mammals, and visual surveys are a commonly employed method for estimating population size despite concerns over imperfect and unquantified detectability. We used a combined visual-acoustic survey to estimate detectability of Ganges River dolphins (Platanista gangetica gangetica) in four waterways of southern Bangladesh. The combined visual-acoustic survey resulted in consistently higher detectability than a single observer-team visual survey, thereby improving power to detect trends. Visual detectability was particularly low for dolphins close to meanders where these habitat features temporarily block the view of the preceding river surface. This systematic bias in detectability during visual-only surveys may lead researchers to underestimate the importance of heavily meandering river reaches. Although the benefits of acoustic surveys are increasingly recognised for marine cetaceans, they have not been widely used for monitoring abundance of freshwater cetaceans due to perceived costs and technical skill requirements. We show that acoustic surveys are in fact a relatively cost-effective approach for surveying freshwater cetaceans, once it is acknowledged that methods that do not account for imperfect detectability are of limited value for monitoring

Preparation of a one-dimensional hierarchical MnO@CNT@Co-N/C ternary nanostructure as a high-performance bifunctional electrocatalyst for rechargeable Zn-air batteries

Developing high-performance bifunctional electrocatalysts for both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a significant challenge for the implementation of rechargeable Zn-air batteries. Herein, MnO2nanotubes (NTs) are prepared as both templates and oxidants to grow polypyrrole (PPy) nanotubes (NTs), on which a zeolite imidazole framework-67 (ZIF-67) is grown. Following that, a single calcination step transforms MnO2, PPy and ZIF-67 into MnO nanoparticles, carbon nanotubes (CNTs) and Co-N doped carbon materials (Co-N/C), respectively to form a one-dimensional (1D) hierarchical ternary nanocomposite. In this composite, the CNTs encapsulate the MnO particles to effectively prevent their further agglomeration. The separated MnO particles possess a mixed valence of Mn2+/4+inside the CNTs, which can greatly facilitate electrolyte diffusion and electron transfer during the redox reactions. Furthermore, the Co-N/C and micro-CNTs formed on the CNT provide multiple catalytic active sites (Co-Nx, Co-O, and C-N moieties). At the optimized calcination temperature of 700 °C, MnO@CNT@Co-N/C exhibits excellent ORR/OER catalytic performance with a ΔEvalue of 0.81 V while maintaining structural and compositional stability. Remarkably, the rechargeable Zn-air battery fabricated with MnO@CNT@Co-N/C as the air electrode catalyst displays a higher peak power density (200.8 mW cm−2) and improved cyclability (300 h) at 5 mA cm−2compared to a precious metal commercial catalyst, indicating the potential application of this composite in energy storage and conversion technology.</p

Template-assisted synthesis of high-efficiency bifunctional catalysts with roller-comb-like nanostructure for rechargeable zinc-air batteries

One-dimensional (1D) nanomaterials which are rich in multiple transition metal-nitrogen-carbon active sites have great potential as catalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Herein, a roller-comb-like 1D nanostructure is synthesized by a template-assisted method with pyrolysis to create such bifunctional catalysts. Initially, two zeolite imidazole frameworks (ZIF-8 and ZIF-67) are simultaneously grown on polypyrrole (PPy) nanotubes, which are then calcined into 1D N doped carbon nanotubes (NCNTs) modified with Zn, Co nanoparticles and micro-CNTs. The simultaneous formation of two ZIFs on the PPy tubes reduces their particle sizes, which subsequently increases the density of metal nanoparticles on the 1D CNTs. Importantly, the co-deposition of both Zn and Co nanoparticles is a necessary condition to generate a large amount of micro-CNTs, which are embedded with metal nanoparticles at their ends, promoting the connectivity between the metal active sites. The temperature effect on the morphology, composition and properties of pyrolysis products was investigated in detail, which identified that the catalyst synthesised at 800 °C exhibited the best bifunctional ORR/OER performance with a ΔE value as low as 0.73 V. A rechargeable Zn-air battery assembled with this catalyst achieves an excellent peak power density of 194.3 mW cm−2.</p

Micellar Solutions of PMMA- b -PNIPAM in Water/Methanol Mixtures: Effect of Temperature on the Micellar Size, Core–shell Structure, and Interaction

In aqueous solution, diblock copolymers PMMA-b-PNIPAM having a short PMMA block and a long PNIPAM block form micelles with a PMMA core and a PNIPAM-rich shell. The same holds true for solutions in water containing small amounts of methanol. Here, we address the micellar structures for 10 g L–1 solutions of PMMA21-b-PNIPAM283 in 90:10 and 80:20 v/v water/methanol in wide temperature ranges across the respective cloud point temperature. Dynamic light scattering and synchrotron small-angle X-ray scattering reveal that the content of methanol strongly influences the temperature behavior of the overall micellar size upon heating to the cloud point temperature, the aggregation number of the micelles, their shell thickness, and their interactions. While the behavior in the 90:10 mixture is similar to that in neat water, in the 80:20 mixture, the micelles are significantly smaller and form clusters already below the cloud point temperature in water. Thus, by variation of the methanol content, the structure and interactions of the micelles can be controlled

Co-Nonsolvency Effect in Solutions of Poly(methyl methacrylate)bpoly(Nisopropylacrylamide) Diblock Copolymers in Water/Methanol Mixtures

The self-assembly of the thermoresponsive amphiphilic diblock copolymer PMMA21-b-PNIPAM283 is studied in different water/methanol mixtures. It consists of a short hydrophobic poly(methyl methacrylate) block and a long thermoresponsive poly(N-isopropylacrylamide) block. Adding methanol as a cosolvent causes the PNIPAM block, which is soluble in both pure water and pure methanol, to collapse due to the so-called co-nonsolvency effect. Meanwhile, the addition of methanol reduces the incompatibility of the PMMA block with water. By means of turbidimetry and differential scanning calorimetry, the solvent-composition-dependent phase diagram is constructed. Dynamic light scattering and synchrotron radiation-based small-angle X-ray scattering provide structural information at 20 °C in dependence on the solvent composition. In water-rich solvent mixtures, self-assembled spherical core–shell micelles are formed. The internal structure of the micelles is adjusted by the solvent compositions in two ways: methanol softens the PMMA micellar core, while it causes the shrinkage of the PNIPAM micellar shell. In methanol-rich solvent mixtures beyond the miscibility gap, the copolymers are molecularly dissolved chains. They are collapsed near the coexistence line, while they become random coils as the methanol content increases. We propose that the internal morphology of the micelles and the conformation of the dissolved chains depend strongly on the solvent composition, as a consequence of the superposed co-nonsolvency effect of PNIPAM and the overall enhanced solvation of PMMA when adding methanol

Sodium Dodecylbenzene Sulfonate Interface Modification of Methylammonium Lead Iodide for Surface Passivation of Perovskite Solar Cells

Perovskite solar cells (PSCs) have been developed as a promising photovoltaic technology because of their excellent photovoltaic performance. However, interfacial recombination and charge carrier transport losses at the surface greatly limit the performance and stability of PSCs. In this work, the fabrication of high-quality PSCs based on methylammonium lead iodide with excellent ambient stability is reported. An anionic surfactant, sodium dodecylbenzene sulfonate (SDBS), is introduced to simultaneously passivate the defect states and stabilize the cubic phase of the perovskite film. The SDBS located at grain boundaries and the surface of the active layer can effectively passivate under-coordinated lead ions and protect the perovskite components from water-induced degradation. As a result, a champion power conversion efficiency (PCE) of 19.42% is achieved with an open-circuit voltage (V$_{OC}$) of 1.12 V, a short-circuit current (J$_{SC}$) of 23.23 mA cm$^{–2}$, and a fill factor (FF) of 74% in combination with superior moisture stability. The SDBS-passivated devices retain 80% of their initial average PCE after 2112 h of storage under ambient conditions