Enhancing ion selectivity by tuning solvation abilities of covalent-organic-framework membranes.

Understanding the molecular-level mechanisms involved in transmembrane ion selectivity is essential for optimizing membrane separation performance. In this study, we reveal our observations regarding the transmembrane behavior of Li+ and Mg2+ ions as a response to the changing pore solvation abilities of the covalent-organic-framework (COF) membranes. These abilities were manipulated by adjusting the lengths of the oligoether segments attached to the pore channels. Through comparative experiments, we were able to unravel the relationships between pore solvation ability and various ion transport properties, such as partitioning, conduction, and selectivity. We also emphasize the significance of the competition between Li+ and Mg2+ with the solvating segments in modulating selectivity. We found that increasing the length of the oligoether chain facilitated ion transport; however, it was the COF membrane with oligoether chains containing two ethylene oxide units that exhibited the most pronounced discrepancy in transmembrane energy barrier between Li+ and Mg2+, resulting in the highest separation factor among all the evaluated membranes. Remarkably, under electro-driven binary-salt conditions, this specific COF membrane achieved an exceptional Li+/Mg2+ selectivity of up to 1352, making it one of the most effective membranes available for Li+/Mg2+ separation. The insights gained from this study significantly contribute to advancing our understanding of selective ion transport within confined nanospaces and provide valuable design principles for developing highly selective COF membranes.

After the pandemic is before the pandemic: Rethinking urban priorities, assumptions and planning approaches.

The global covid-pandemic had significant impacts upon cities and city planning in the short, medium and longer term. Early severe disruptions to city living and working patterns prompted interventions from planners and the suspension of plans, largely based on projections of pre-pandemic data and trends. Longer term thinking has begun to settle into a pattern of reactions and approaches depending upon the characteristics of the city. This paper explores some of the responses to the pandemic and how cities are adapting and evolve towards a 'new normal' and what this might mean for planning and planners in future. Two questions are posed for future research following from this. First, will planners require new skills and knowledge going forward as cities adapt and evolve and, second, how can we better comprehend the full spectrum of responses and trajectories of city planning post-pandemic.

Terahertz Bessel metalens with an extended non-diffractive length and a high efficiency.

In this paper, we propose a reflective terahertz (THz) Bessel metalens that utilizes polarization-insensitive sub-wavelength metal resonator-dielectric-metal structures. The Bessel metalens is configured with the superposition of hyperboloidal and conical phase profiles, resulting in a high-efficiency and long non-diffractive length Bessel beam. Our experimental results demonstrate that the proposed Bessel metalens has a focusing efficiency of 72.1% and a non-diffractive length of 239λ. This device has promising aspects in the fields of THz imaging systems and other miniaturized and integrated scenes that require non-diffractive Bessel beams.

Features and spatial effects of urban development and decline in resource-oriented cities: The case of Jilin, China.

Transforming resource-based cities into sustainable economic development is a great challenge for policy-makers in many countries. However, the economic-centered evaluation system tends to breed the undesirable view of "GDP only" or "brown growth" in the previous case studies which is inconsistent with the long-run and sustainable development of resource-based cities. To fill in this research gap, this paper takes Jilin province in northeast China as a case study to explore urban development problems faced by major resource-based cities during resource depletion. This research constructs a stratified indicator system and conducts an in-depth analysis of the features and spatial effects of urban decline. For this analysis, this paper jointly uses the methods of entropy-weighted TOPSIS, analytic hierarchical process (AHP), and spatial effect model based on a database from 2000 to 2019. The findings of this study show that the current transformation of resource-based cities in Jilin province is generally ineffective and difficult to maintain long-run and sustainable development due to its historical reasons and industrial development background. According to the results, the resource-based cities in Jilin province show an unstable development because of factors such as barriers to the physical renewal of resources, rigid industrial structure, insufficient backup resources, and institutional and policy constraints. Also, the transformation of these cities into sustainable economic development is still facing demographic, social, and ecological difficulties.

[Pathological voice detection based on gammatone short time spectral self-similarity].

The acoustic detection method based on machine learning and signal processing is an important method of pathological voice detection and the extraction of voice features is one of the most important. Currently, the features widely used have disadvantage of dependence on the fundamental frequency extraction, being easily affected by noise and high computational complexity. In view of these shortcomings, a new method of pathological voice detection based on multi-band analysis and chaotic analysis is proposed. The gammatone filter bank was used to simulate the human ear auditory characteristics to analyze different frequency bands and obtain the signals in different frequency bands. According to the characteristics that turbulence noise caused by chaos in voice will worsen the spectrum convergence, we applied short time Fourier transform to each frequency band of the voice signal, then the feature gammatone short time spectral self-similarity (GSTS) was extracted, and the chaos degree of each band signal was analyzed to distinguish normal and pathological voice. The experimental results showed that combined with traditional machine learning methods, GSTS reached the accuracy of 99.50% in the pathological voice database of Massachusetts Eye and Ear Infirmary (MEEI) and had an improvement of 3.46% compared with the best existing features. Also, the time of the extraction of GSTS was far less than that of traditional nonlinear features. These results show that GSTS has higher extraction efficiency and better recognition effect than the existing features.

Anomalous thermo-osmotic conversion performance of ionic covalent-organic-framework membranes in response to charge variations.

Increasing the charge density of ionic membranes is believed to be beneficial for generating high output osmotic energy. Herein, we systematically investigated how the membrane charge populations affect permselectivity by decoupling their effects from the impact of the pore structure using a multivariate strategy for constructing covalent-organic-framework membranes. The thermo-osmotic energy conversion efficiency is improved by increasing the membrane charge density, affording 210 W m-2 with a temperature gradient of 40 K. However, this enhancement occurs only within a narrow window, and subsequently, the efficiency plateaued beyond a threshold density (0.04 C m-2). The complex interplay between pore-pore interactions in response to charge variations for ion transport across the upscaled nanoporous membranes helps explain the obtained results. This study has far-reaching implications for the rational design of ionic membranes to augment energy extraction rather than intuitively focusing on achieving high densities.

Thermo-Osmotic Energy Conversion Enabled by Covalent-Organic-Framework Membranes with Record Output Power Density.

A vast amount of energy can be extracted from the untapped low-grade heat from sources below 100 °C and the Gibbs free energy from salinity gradients. Therefore, a process for simultaneous and direct conversion of these energies into electricity using permselective membranes was developed in this study. These membranes screen charges of ion flux driven by the combined salinity and temperature gradients to achieve thermo-osmotic energy conversion. Increasing the charge density in the pore channels enhanced the permselectivity and ion conductance, leading to a larger osmotic voltage and current. A 14-fold increase in power density was achieved by adjusting the ionic site population of covalent organic framework (COF) membranes. The optimal COF membrane was operated under simulated estuary conditions at a temperature difference of 60 K, which yielded a power density of ≈231 W m-2 , placing it among the best performing upscaled membranes. The developed system can pave the way to the utilization of the enormous supply of untapped osmotic power and low-grade heat energy, indicating the tremendous potential of using COF membranes for energy conversion applications.

The synergetic effect of an aqua ligand and metal site on the performance of single-atom catalysts in H2O2 synthesis: a density functional theory study.

Studying the effect of the coordination field on the catalytic property is critical for the rational design of outstanding electrocatalysts for H2O2 synthesis. Herein, via density functional theory (DFT) calculations and ab initio molecular dynamic (AIMD) simulations, we built an effective computational framework to identify the synergetic effect of an aqua ligand and metal ion on the 2e- ORR catalytic performance under gas condition and aqua solvent. Specifically, the screening results of 29 single-atom catalysts (SACs), TM@C6N6 (TM = transition metal), indicated that Cu@C6N6 features excellent catalytic property with thermal stability, lowest 2e- ORR overpotential (0.02 V) and high selectivity of 99.99%. Once an aqua ligand binds with the Cu site, the activity is reduced to the overpotential of 0.42 V and the selectivity decreased slightly (99.98%) due to the reduction of the adsorption strength for the reaction intermediates. A combination of geometric structures and electronic properties revealed that such changes are correlated with the charge of the Cu site. Furthermore, based on molecular orbital theory, the essence of the high catalytic property deeply lies in the effect of the moderate electron back donation bond (dyz & dxz→) between Cu and O2. This work will provide a route to better design high-performance SACs for H2O2 synthesis effectively.

High-performance single-atom Ni catalyst loaded graphyne for H2O2 green synthesis in aqueous media.

The electrochemical synthesis of hydrogen peroxide (H2O2) provides a greener and more efficient method compared with classic catalysts containing toxic metals. Herein, we used first-principles density functional theory (DFT) calculations to investigate 174 different single-atom catalysts with graphyne substrates, and conducted a three-step screening strategy to identify the optimal noble metal-free single atom catalyst. It is found that a single Ni atom loaded on γ-graphyne with carbon vacancies (Ni@V-γ-GY) displayed remarkable thermodynamic stability, excellent selectivity, and high activity with an ultralow overpotential of 0.03 V. Furthermore, based on ab-initio molecular dynamic and DFT calculations under the H2O solvent, it was revealed that the catalytic performance for H2O2 synthesis in aqueous phase was much better than that in gas phase condition, shedding light on the hydrogen bond network being beneficial to accelerate the transfer of protons for H2O2 synthesis.

7-Connected FeIII3-Based Bio-MOF: Pore Space Partition and Gas Separations.

We reported herein a new 3D bio-MOF (NbU-12) using a pore space partition strategy: MIL-88D was selected as a primary framework, and adenine connected two independent MIL-88D to form a self-interpenetrated structure. Because of this, the hexagonal channel in MIL-88D split into two small rectangular channels. Different from the reported series CPM-35 materials, NbU-12 simultaneously maximized the retention of open metal sites from MIL-88D and introduced a Watson-Crick face to the pore surface of NbU-12. Remarkably, NbU-12 exhibits an excellent selectivity performance toward C2H6/C2H4 and C2H6/CH4, which was proven by ideal adsorbed solution theory calculation and breakthrough experiments.

Highly Robust Tetranuclear Cobalt-Based 3D Framework for Efficient C2H2/CO2 and C2H2/C2H4Separations.

A novel noninterpenetrated tetranuclear cobalt(II)-based metal-organic framework, (NH4)2·[Co4(µ3-OH)2(ina)2(pip)3]·4EtOH·H2O (simplified as NbU-10·S), constructed by mix linkers was synthesized by a hydrothermal method. Interestingly, the presence of a hydrophobic benzene ring in the organic linker makes NbU-10·S exhibit high stability in high temperature and even in aqueous solution over a wide pH range of about 4-13. Magnetic studies showed that the tetranuclear cobalt(II) units in NbU-10·S show dominant antiferromangetic properties. However, in the absence of Lewis basic functional sites and open metal sites in the material, NbU-10 still displays high C2H2/CO2 and C2H2/C2H4 selectivity in ideal adsorbed solution theory calculations and dynamic breakthrough experiments. Moreover, density functional theory calculations were performed to identify the adsorption characteristics of different gas molecules.

[Clinical study of effect of tianzhi granule on senile vascular demetia].

OBJECTIVE: To investigate the clinical effect of Tianzhi Granule (TZK) on senile vascular dementia (VaD), which is classified as sthenia of liver-yang. METHOD: Two hundred VaD patients were treated with TZK (0.5 g/bag), which was taken one bag each, three times a day. The treatment course was one month and they were treated for rwo courses. RESULT: TZK could remarkably increase gnosia and activity, with no striking difference from that of positive control group (P > 0.05). Simultaneously, TZK could significantly improve the clinical syndrome of traditional Chinese medicine and viability. It could also drastically reduce the whole blood and plasma viscosity and improve erythrodegeneration and abnormality of aggregation index in the abnormal blood viscosity patients. CONCLUSION: TMC has certain effects on senile VaD.