Showing papers by "Zhong Chen published in 2023"

Ligands-triggered evolution of catalytic intermediates during periodate activation via soluble Mn(II) for organic contaminants’ abatement

Abstract: Homogenous catalysis technology could be flexibly combined with existing water treatment facilities, which presents broad applicational prospects and deserves systematic study. This work reinvestigated the periodate (IO 4 − , PI) activation process mediated by hydrated Mn II ions and highlighted the critical involvement of the in-situ formed colloidal MnO 2 (Mn IV ). Mn II ions were directly oxidized to colloidal Mn IV in the Mn II /PI system, and the nascent Mn IV could in turn activate PI to form Mn IV -PI* complex as the reactive oxidant. Besides, several kinds of ligands were introduced into the Mn II /PI oxidation system to explore their influences. Nitrilotriacetic acid (NTA) outperformed other selected ligands and could significantly enhance PI activation to degrade organic contaminants, which could achieve a removal efficiency of ~99% within seconds. Interestingly, the presence of NTA completely altered the catalytic pathways rather than just accelerating the generation of reactive oxidants. Combining the results of sulfoxide-probe transformation tests and the 18 O isotope-tracer experiments, we proposed that the high-valent manganese-oxo (Mn V -oxo) species was the dominant reactive oxidant generated in the Mn II /NTA/PI system, and the metastable Mn III complex was the precursor of the Mn V -oxo species. Notably, maintaining the Mn II high-spin d 5 center and stabilizing the in-situ formed Mn III intermediates were the crucial premises for the evolution of the catalytic oxidation process triggered by functional ligands. This work clarified the critical involvement of functional ligands during PI activation via soluble Mn II and might also inspire the designing of heterogeneous catalyst modification for the water treatment technology. • Nascent colloidal Mn IV contributed to PI activation in Mn II /PI system. • NTA could significantly enhance the performance of PI activation via soluble Mn II . • Mn III -NTA complex was the primary catalytic intermediates in the Mn II /NTA/PI system. • High-valent Mn V -oxo species was identified as the reactive oxidant in Mn II /NTA/PI system.

Effect of Moderate and Vigorous Aerobic Exercise on Incident Diabetes in Adults With Obesity: A 10-Year Follow-up of a Randomized Clinical Trial.

Abstract: This randomized clinical trial assesses the long-term effect of vigorous and moderate exercise on incident diabetes over a 10-year follow-up after a 12-month exercise intervention.

Rapid high‐fidelity T2* mapping using single‐shot overlapping‐echo acquisition and deep learning reconstruction

Abstract: To develop and evaluate a single‐shot quantitative MRI technique called GRE‐MOLED (gradient‐echo multiple overlapping‐echo detachment) for rapid T2*$$ {T}_2^{\ast } $$ mapping.

Single-Layer MoS2: A Two-Dimensional Material with Negative Poisson’s Ratio

Abstract: Negative Poisson’s ratio (NPR) materials have broad applications such as heat dissipation, vibration damping, and energy absorption because of their designability, lightweight quality, and high strength ratio. Here, we use first-principles calculations to find a two-dimensional (2D) auxetic material (space group Rm), which exhibits a maximum in-plane NPR of −0.0846 and a relatively low Young’s modulus in the planar directions. Calculations show that the NPR is mainly related to its unique zigzag structure and the strong interaction between the 4d orbital of Mo and the 3p orbital of S. In addition, molecular dynamics (MD) simulations show that the structure of this material is thermodynamically stable. Our study reveals that this layered MoS2 can be a promising 2D NPR material for nanodevice applications.

Decreasing Magnetic-Field Inhomogeneity by Inlaying the RF Coil Into a Tubular Bracket

Abstract: The homogeneous magnetic field is highly desired for achieving high-resolution nuclear magnetic resonance (NMR) spectra. Inevitably, however, nonzero magnetic susceptibility (non-ZMS) structures near the detection region, such as radio-frequency (RF) coils and brackets among others, accentuate the magnetic field inhomogeneity ( $\beta $ ) and broaden NMR spectral lines. In this study, we discover that when cylindrical sensors are perpendicular to the applied magnetostatic field, inlaying the RF coil into a tubular bracket that coaxially overlays the tube can reduce $\beta $ within the detection region of this RF coil. This inlay depth can be optimized by enforcing magnetic dipole fields induced by the RF coil to equal those of the materials replaced by this RF coil. Based on this mechanism, we have developed an inlaid-coil sensor for a lab-built compact NMR spectrometer, which is merely additionally installed with a tubular Teflon bracket. Simulated results demonstrate that, as this depth approaches the optimal theoretical value, $\beta $ within the detection region gradually decreases, supporting our identification of such a mechanism. Furthermore, experimental results reveal that the inlaid-coil sensor can acquire higher-resolution NMR spectra than the bracketless sensor can, validating the compensation mode based on this mechanism. This approach can achieve magnetostatic-field compatibility among different materials inside cylindrical sensors perpendicular to the imposed magnetostatic field. Hopefully, our study can help provide a guide for the magnetostatic-field design of complex cylindrical sensors in emerging NMR technologies such as microsystems, hyperpolarization, and in situ detection.

The Influence of Wind-Induced Response in Urban Trees on the Surrounding Flow Field

Abstract: In recent years, cities have experienced frequent climate changes and deteriorating wind environments. Urban vegetation has become an important measure to improve local microclimates with its flexible configuration. Leaves and branches also reorient with the direction of wind, affecting the airflow through the tree. However, trees are usually considered as stationary porous media areas and are not influenced by wind speed in existing numerical simulation studies. Therefore, by considering the response of a tree under natural wind, this study established a fitted relationship between porosity and wind speed by measuring the porosity of trees at different wind speeds in the field. A numerical model of the wind response of the tree was developed, and the tree drag coefficient was changed using the additional source term method to verify the feasibility of the model by measuring the wind environment behind the tree. To understand the effect of the wind-induced response on the surrounding flow field and its variation pattern, the surrounding flow fields of stationary tree (T-S) and wind-induced tree (T-D) at different wind speeds were compared and analyzed. The effect of porosity and height-to-width ratio under the wind-induced response of trees on the wind environment were quantified. It was found that at different wind speeds, as the wind speed increases, the tree porosity gradually increases and the drag coefficient decreases accordingly. The effective shading distance after wind response was 2.4H, which was 0.3H less compared to vertically fixed trees. The minimum wind speed increased linearly with plant porosity, and the minimum wind speed occurrence location and wind speed recovery distance were linearly and negatively correlated with tree height-to-width ratio. Therefore, the flow field around the tree was simulated to provide references for guiding tree planting and mitigating urban wind environments.

Roles of acyl‐coenzyme A synthetase family members in airway epithelia cells

Abstract: Background The fundamental initial step in the metabolic process of fatty acids (FA) is facilitated by Acyl-coenzyme A synthetase (ACS). ACS enables FAs to engage in both anabolic and catabolic pathways by creating thioester bonds with CoA, thus triggering their activation. This paper demonstrated the effect of in vitro cells on the ACS family of key enzymes in FA metabolism in response to inflammatory or lipid stimulating factors and provided insight into the relevant metabolic mechanisms. Methods The expression levels of 27 ACS family members were assessed across various lung epithelial cell lines, such as HBE, SPC-1A, or NCI-H460, in response to external challenges including lipopolysaccharide (LPS), lysophosphatidylcholine (lysoPC), cigarette smoking extract (CSE), cholesterol, and interference with the ACSL5 gene in response to FASN, CPT1A inhibitors. Results Our data showed that ACSF2 was highly expressed in SPC-A1 and NCI-H460 cells compared with HBE cell, while ACSL4 and ACSVL4 were lower expressed. The 27 ACS family genes associated with FA metabolism varied under several different exogenous stimuli.

Whose Oxygen Atom Is Transferred to the Products? A Case Study of Peracetic Acid Activation via Complexed MnII for Organic Contaminant Degradation.

Abstract: Identifying reactive species in advanced oxidation process (AOP) is an essential and intriguing topic that is also challenging and requires continuous efforts. In this study, we exploited a novel AOP technology involving peracetic acid (PAA) activation mediated by a MnII-nitrilotriacetic acid (NTA) complex, which outperformed iron- and cobalt-based PAA activation processes for rapidly degrading phenolic and aniline contaminants from water. The proposed MnII/NTA/PAA system exhibited non-radical oxidation features and could stoichiometrically oxidize sulfoxide probes to the corresponding sulfone products. More importantly, we traced the origin of O atoms from the sulfone products by 18O isotope-tracing experiments and found that PAA was the only oxygen-donor, which is different from the oxidation process mediated by high-valence manganese-oxo intermediates. According to the results of theoretical calculations, we proposed that NTA could tune the coordination circumstance of the MnII center to elongate the O-O bond of the complexed PAA. Additionally, the NTA-MnII-PAA* molecular cluster presented a lower energy gap than the MnII-PAA complex, indicating that the MnII-peroxy complex was more reactive in the presence of NTA. Thus, the NTA-MnII-PAA* complex exhibited a stronger oxidation potential than PAA, which could rapidly oxidize organic contaminants from water. Further, we generalized our findings to the CoII/PAA oxidation process and highlighted that the CoII-PAA* complex might be the overlooked reactive cobalt species. The significance of this work lies in discovering that sometimes the metal-peroxy complex could directly oxidize the contaminants without the further generation of high-valence metal-oxo intermediates and/or radical species through interspecies oxygen and/or electron transfer.

An iterative method for solving a PDE with free boundary arising from pricing corporate bond with credit rating migration

Abstract: In this paper an iterative method is proposed to solve a partial differential equation (PDE) with free boundary arising from pricing corporate bond with credit grade migration risk. A iterative algorithm is designed to construct two sequences of fixed internal boundary problems, which produce two weak solution sequences. It is proved that both weak solution sequences are convergent. In each iteration step, an implicit-upwind difference scheme is used to solve the fixed internal boundary problem. It is shown that the scheme is stable and first-order convergent. Numerical experiments verify that the limit of the weak solution sequence is the solution of the free boundary problem. This method simplifies the free boundary problem solving, ensures the stability of the discrete scheme and reduces the amount of calculation.

Convex Dual Theory Analysis of Two-Layer Convolutional Neural Networks with Soft-Thresholding

Abstract: Soft-thresholding has been widely used in neural networks. Its basic network structure is a two-layer convolution neural network with soft-thresholding. Due to the network's nature of nonlinearity and nonconvexity, the training process heavily depends on an appropriate initialization of network parameters, resulting in the difficulty of obtaining a globally optimal solution. To address this issue, a convex dual network is designed here. We theoretically analyze the network convexity and numerically confirm that the strong duality holds. This conclusion is further verified in the linear fitting and denoising experiments. This work provides a new way to convexify soft-thresholding neural networks.

Continuous Flow Experimental Study on Ozonation of Ibuprofen Catalyzed by Silicate-Based Microfiltration Membrane

Abstract: In the treatment of drinking water, the ibuprofen (IBP) disinfection by-products, toxicity, and its impact on drinking water safety have caused widespread attention in domestic and overseas research areas. We studied the removal efficiency of IBP under the following conditions: combination of good catalytic activity of a silicate-based microfiltration membrane with the strong oxidizing ability of ozone in the continuous flow experiment mode and various influencing factors. This research revealed that with the increase of pH and hydraulic retention time, the removal efficiency of IBP exhibited an increasing trend; with the increase of alkalinity and humic acid concentration in water, the removal efficiency of IBP was obviously inhibited. Free radical inhibitors and electron spin resonance (ESR) analysis demonstrated that hydroxyl radical (∙OH) is an important active species during the reaction of ozone-catalyzed IBP with the silicate-based microfiltration membrane.