Specific Structure Research Articles

Facile fabrication of AgBr/HCCN hybrids with Z-scheme heterojunction for efficient photocatalytic hydrogen evolution

Constructing a Z-scheme heterojunction with enhanced photocatalytic hydrogen evolution for graphitic carbon nitride-based (g-C3N4) composites is challenging because integrating g-C3N4 with other semiconductors, without specific band structure design, typically results in type I or type II heterojunctions. These heterojunctions have lower redox ability and limited enhancement in photocatalysis. Herein, we select highly crystalline carbon nitride (HCCN) as a proof-of-concept substrate. For the first time, we develop a AgBr nanosphere/HCCN composite photocatalyst that features an all-solid-state direct Z-scheme heterojunction for visible-light photocatalytic hydrogen evolution. The electron transfer mechanism is initially studied from the band structures and Fermi levels of HCCN and AgBr. It is subsequently confirmed by X-ray photoelectron spectroscopy (XPS), and electron microscopy. The close heterojunction contact and the built-in electron field of the Z-scheme heterojunction promote the migration and separation of photogenerated electrons and holes in the composite photocatalyst. Due to the redistribution of charge carriers, the photocatalyst shows superior redox capability and a markedly enhanced hydrogen evolution performance compared to its individual components. Combining all the advantages, AgBr nanosphere/HCCN reached an apparent quantum efficiency (AQE) of 6 % under the illumination of 410 nm, which is 4 times higher than that of the single HCCN component.

Cucurbit[6]uril builds a water channel for improving the water/salt selectivity of polybenzimidazole

Polybenzimidazole (PBI) has garnered significant interest in desalination due to its exceptional chemical stability and mechanical strength, but suffers from poor water permeability. In this work, different contents of hydroxylated Cucurbit [6]uril (CB [6] were added to PBI to build a “water transport channel”. The effects of CB [6] addition on the chemical structure and surface morphology were analyzed by FTIR, SEM, and Zeta potential, respectively. Based on the solution-diffusion model, the effect of CB [6] on the water/salt transport properties of PBI membranes was thoroughly investigated. The results show that appropriate CB [6] doping can enhance water sorption of PBI through the special “outer hydrophilic and inner hydrophobic cavity” structure, and boost water diffusion with the channeling effect of the hydrophobic CB [6] cavity. While the complexation between the carbonyl group in CB [6] and Na+ ions slightly increased salt sorption, the specific cavity structure of CB [6] can significantly decrease salt diffusion by blocking salt ions and increasing transport path tortuosity. The cavity effect of CB [6] was further confirmed by hybridizing CB [6] with biphenylsulfonyl-substituted PBI when the cavity can be occupied. Therefore, the introduction of CB [6] improves the water/salt diffusion selectivity and then the permeability selectivity of PBI. Notably, the PBI@CB [6] membrane with a 0.25 wt% CB [6] loading exhibited a 40-fold increase in water permeability coefficient compared to pure PBI, while experiencing only a slight decrease in salt permeability coefficient, water/salt selectivity almost exceeding the empirical upper bound line of polymers. This work provides a theoretical foundation for the development of high-performance desalination membranes based on macrocyclic molecules such as CB [6].

Simulation and fabrication of in vitro microfluidic microelectrode array chip for patterned culture and electrophysiological detection of neurons

To enable the detection and modulation of modularized neural networks in vitro, this study proposes a microfluidic microelectrode array chip for the cultivation, compartmentalization, and control of neural cells. The chip was designed based on the specific structure of neurons and the requirements for detection and modulation. Finite-element analysis of the chip’s flow field was conducted using the COMSOL Multiphysics software, and the simulation results show that the liquid within the chip can flow smoothly, ensuring stable flow fields that facilitate the uniform growth of neurons within the microfluidic channels. By employing MEMS technology in combination with nanomaterial modification techniques, the microfluidic microelectrode array chip was fabricated successfully. Primary hippocampal neurons were cultured on the chip, forming a well-defined neural network. Spontaneous electrical activity of the detected neurons was recorded, exhibiting a 23.7% increase in amplitude compared to neuronal discharges detected on an open-field microelectrode array. This study provides a platform for the precise detection and modulation of patterned neuronal growth in vitro, potentially serving as a novel tool in neuroscience research.

Development of a National Guide for Designing the Structure of Makeshift Hospital: With Focus on Pandemics

Background: Epidemics are threats to communities and their health. The preparedness of makeshift hospitals in epidemics in management, planning, implementation, and structure to provide appropriate and timely services is essential. Studies show that the incidence command system and the operational fact sheet based on task descriptions and instructions in makeshift hospitals are not considered. This study is designed to develop an appropriate organizational structure for makeshift hospitals. Materials and Methods: This was a descriptive-analytical cross-sectional study in two stages, including review and expert panel studies, to develop a national fact sheet guide and the structure of makeshift hospitals. Results: Based on the nature of disasters, makeshift hospitals should have specific structures. In the structure designed for a makeshift hospital, according to the center’s services and time of activation, it is necessary to have a manager, management, and executive staff. A medical specialist, such as an infectious or pulmonary specialist, is essential, depending on the situation. Considering the limited resources in developing countries and the importance of managing resources (financial, human, and equipment) and improving the quality of health services, it will be helpful to formulate a management structure and implement operational worksheets in the least possible time. Conclusion: The use of command and management structure will improve decision-making in critical situations, especially in cases of epidemics, the need for quarantine, and the provision of services to injured patients.

Boosting the output performance of triboelectric nanogenerators via surface engineering and structure designing.

Triboelectric nanogenerators (TENGs) have been utilized in a wide range of applications, including smart wearable devices, self-powered sensors, energy harvesting, and high-voltage power sources. The surface morphology and structure of TENGs play a critical role in their output performance. In this review, we analyze the working mechanism of TENGs with the aim to improve their output performance and systematically summarize the morphological engineering and structural design strategies for TENGs. Additionally, we present the emerging applications of TENGs with specific structures and surfaces. Finally, we discuss the potential future development and industrial application of TENGs. By deeply exploring the surface and structural design strategy of high-performance TENGs, it is conducive to further promote the application of TENGs in actual production. We hope that this review provides insights and guidance for the morphological and structural design of TENGs in the future.

Analysis and Design of a Novel Hybrid Modular Multilevel Converter With Time-Sharing Alternative Arm Converter

This paper proposes a time-sharing principle-based modular multilevel converter (TS-MMC) for medium- to high-voltage power transmission applications, which is designed with a lightweight running feature. The TS-MMC consists of cascaded switch stacks (CSSs) and alternative arm converters (AACs), integrating the merits of both the MMC and the two-level voltage source converter (VSC). In TS-MMC, the AACs shape the required multilevel arm waveforms, and the CSSs arrange the AACs operating at different intervals for producing the desirable output waveforms. By applying a “time-sharing” principle for the AACs, a dramatic reduction of the sub-module (SM) number is achieved. Additionally, the TS-MMC does not require any arm inductors, whereas only three inductors are equipped in AC side. Moreover, featured by the specific structure, the DC fault blocking capability of the TS-MMC is also enabled. Furthermore, to explore the performance of the TS-MMC, mathematical model and control strategy of the TS-MMC are provided. Finally, the simulation and experimental results are carried out to verify the feasibility of the TS-MMC.

Adsorption of typical dyes in water by sponge based covalent organic frameworks: Pore size and mechanism

This study addressed the ambiguity surrounding the relationship between the pore size of covalent organic frameworks (COFs) and their adsorption capacity and rate. To achieve this, we synthesized COFs with five distinct pore sizes (COF1-COF5) and conducted a comprehensive analysis using kinetic models. Our findings indicated that the adsorption capacity and rate of methyl orange (MO) increased linearly with the pore size of COFs, from 1.25 nm to 2.57 nm. Notably, COF3, with a pore size of 2.57 nm, exhibited the highest adsorption performance for MO, boasting an impressive capacity of 43.07 mg/g. Furthermore, we tackled the challenge of COFs powder recovery by employing a one-pot synthesis method to create SP-COFs, where COFs powder was loaded onto polyurethane sponge. Through rigorous adsorption and analytical experiments, we demonstrated that SP-COF3 achieved rapid recovery while efficiently adsorbing MO, maintaining a high removal efficiency of over 95% even after 8 reuse cycles. The mechanism underlying MO adsorption on SP-COF3 was attributed to electrostatic interaction and hydrogen bonding, with the possibility of π-π interaction also being considered. Overall, this study provides valuable new insights into the tailored synthesis of COFs with specific structures and functionalities, shedding light on the crucial relationship between pore size and adsorption behavior. The development of SP-COFs presents a promising approach to enhance the practical application of COFs as highly efficient adsorbents.

How the nature and charge of metal cations affect vibrations in acetone solvent molecules.

Vibrational spectra of a series of gas-phase metal 1+ and 2+ ions solvated by acetone molecules are collected to investigate how the metal charge, number of solvent molecules and nature of the metal affect the acetone. The spectra of Cu+(Ace)(N2)2, Cu+(Ace)4, and M2+(Ace)4, where M = Co, Ni, Cu, and Zn are measured via photodissociation by monitoring fragment ion signal as a function of IR wavenumber. The spectra show a red shift of the CO stretch and a blue shift of the C-C antisymmetric stretch. DFT calculations are carried out to provide the simulated spectra of possible isomers to be compared with the observed vibrational spectra, and specific structures are proposed. The red shift of the CO stretch increases as the number of acetone molecules decreases. Higher charge on the metal leads to a larger red shift in the CO stretch. Although all of the M2+ complexes have very similar red shifts, they are predicted to have different geometries due to their different electron configurations. Unexpectedly, we find that the calculated red shift in the CO stretch in M+/2+(Ace) is highly linearly correlated with the ionization energy of the metal for a wide range of metal cations and dications.

Synthesis of high-quality nano-H-ZSM-5 single crystals zeolite from montmorillonite and MTO catalytic studies

Clay is a rich aluminosilicate resource with unique advantages as a raw material for zeolites production. However, synthesizing nanosized single-crystalline zeolites through a simple approach using clay remains a significant challenge. In this paper, acid-washed montmorillonite (MSR) was used to prepare nano-H-ZSM-5 single crystals with high crystallinity, uniform grain size and permeable straight pores under the induction of a small amount of organic template tetrapropylammonium hydroxide (TPAOH). Through temperature-staged treatment, the nucleation and growth process of zeolite were decoupled, ultimately achieving precise control over the size of the nano-single crystals. Mechanistic study showed that the low-temperature aging process produces smaller structural units which probably derived from the geopolymer topology of the clay, providing more active sites for zeolite nucleation, leading to the rapid crystallization during the high-temperature process. The porous structure promotes material diffusion, inhibits aromatic cycling and reduces carbon formation in the pores. The large specific surface area and nanoscale multilayer pore structure delay carbon accumulation and increase carbon holding capacity. These properties make nano-ZSM-5 single crystals an excellent choice for high olefin selectivity and long catalytic life in the methanol-to-olefin reaction. This synthetic route provides a general strategy for preparing nanosized zeolite single crystals from clay.

Strategies for utilizing covalent organic frameworks as host materials for the integration and delivery of bioactives.

Covalent organic frameworks (COFs), a new and developing class of porous framework materials, are considered a type of promising carrier for the integration and delivery of bioactives, which have diverse fascinating merits, such as a large specific surface area, designable and specific porosity, stable and orderly framework structure, and various active sites. However, owing to the significant differences among bioactives (including drugs, proteins, nucleic acid, and exosomes), such as size, structure, and physicochemical properties, the interaction between COFs and bioactives also varies. In this review, we firstly summarize three strategies for the construction of single or hybrid COF-based matrices for the delivery of cargos, including encapsulation, covalent binding, and coordination bonding. Besides, their smart response release behaviors are also categorized. Subsequently, the applications of cargo@COF biocomposites in biomedicine are comprehensively summarized, including tumor therapy, central nervous system (CNS) modulation, biomarker analysis, bioimaging, and anti-bacterial therapy. Finally, the challenges and opportunities in this field are briefly discussed.

Comparative Analysis of Branch Diameter Variations in ’Cherry Gala’ Apple Trees

This study presents a detailed characterization of the branch architecture of the ’Cherry Gala’ apple variety, conducted in Azrou region, Morocco, with a focus on two distinct stages of growth. The main objective was to measure and analyze the diameters at the base and extremity of various architectural components, including the trunk, scaffold branches, and specific fruit-bearing structures like dard, bourse, and fruiting spurs. Our analysis revealed that the variation in diameter at the base was not significantly different between stages for fruiting spurs and dard, but was significant for bourse. Conversely, the diameter at the extremity showed significant variation for fruiting spurs and bourse, but not for dard. Additionally, the study found a predominance of bearing branches, which constituted 44% of the total. However, crowned twigs, simple twigs, and woody twigs, representing only 5% of the branches, were excluded from the analysis due to their low numbers. The study also established significant correlations between the base and extremity diameters across different types of branches. These findings provide valuable insights into the structural dynamics of ’Cherry Gala’ apple trees, which could be instrumental in optimizing orchard management practices and enhancing yield predictions. Future research could benefit from incorporating these structural aspects with fruit production data for a more holistic understanding of apple tree growth and productivity

Event-Triggered Distributed Secondary Control With Model-Free Predictive Compensation in AC/DC Networked Microgrids Under DoS Attacks.

This article presents an event-triggered distributed secondary control with predictive compensation based on the model-free predictive control under Denial-of-Service (DoS) attacks in ac/dc-networked microgrids. First, models of ac/dc networked microgrids in both electric network and communication network are established. On this premise, event-triggered distributed secondary control is proposed to solve the problems of strong communication burden and low-power distribution accuracy. Besides, aiming at the impact of DoS attacks on distributed secondary control, a compensation algorithm based on model-free predictive control is designed to estimate the control variables when the DoS attack occurs, which can improve the control performance and maintain the stable operation without a specific system structure system. Then, the convergence of event-triggered distributed secondary control with the condition of whether DoS attacks happen are analyzed. Finally, the effectiveness of the proposed control is verified on the hardware-in-loop (HIL) simulation platform consisting of the RT-LAB simulator, MATLAB/Simulink simulation model, and DSP controller.

A chiral metal cluster triggers enantiospecific electronic transport.

Chirality is a geometric property of matter that can be present at different scales, especially at the nanoscale. Here, we investigate the manifestation of chirality in electronic transport through a molecular junction. Spinless electronic transport through a chiral molecular junction is not enantiospecific. However, when a chiral metal cluster, C3-Au34, is attached to the source electrode, a different response is obtained in spinless electronic transport between R and L systems: this indicates the crucial role of chiral clusters in triggering enantiospecific spinless electronic transport. In contrast, when an achiral metal cluster, C3v-Au34, is attached, no change in conductance occurs between enantiomeric systems. Using the non-equilibrium green's function method, we characterized this phenomenon by calculating the transmission and conductance of spin-unpolarized electrons. Our theoretical results highlight the importance of metal clusters with specific sizes and chiral structures in electronic transport and support previously published experimental results that exhibited enantiospecific scanning tunneling measurements with intrinsically chiral tips.

Towards a structural and functional analysis of the immunoglobulin-fold proteome.

The immunoglobulinfold (Igfold) domain is a super-secondary structural motif consisting of a sandwich with two layers of β-sheets that is present in many proteins with very diverse biological functions covering a wide range of physiological processes. This domain presents a modular architecture built with β strands connected by variable length loops that has a highly conserved structural core of four β-strands and quite variable β-sheet extensions in the two sandwich layers that enable both divergent and convergent evolutionary mechanisms in the known Igfold proteome. The central role of this Igfold's structural plasticity in the evolutionary success of antibodies in our immune system is well established. Nature has also utilized this Igfold in all domains of life in many different physiological contexts that go way beyond the immune system. Here we will present a structural and functional overview of the utilization of the Igfold in different biological processes and in different cellular contexts to highlight some of the innumerable ways that this structural motif can interact in multidomain proteins to enable their diversity of functions. This includes shareable specific protein structure visualizations behind those functions that serve as starting points for further explorations of the biomolecular interactions spanning the Igfold proteome. This overview also highlights how this Igfold is being utilized through natural adaptation, engineering, and even building from scratch for a range of biotechnological applications.

Application and Progress of Machine Learning in Pesticide Hazard and Risk Assessment.

Long-term exposure to pesticides is associated with the incidence of cancer. With the exponential increase in the number of new pesticides being synthesized, it becomes more and more important to evaluate the toxicity of pesticides by means of simulated calculations. Based on existing data, machine learning methods can train and model the predictions of the effects of novel pesticides, which have limited available data. Combined with other technologies, this can aid the synthesis of new pesticides with specific active structures, detect pesticide residues, and identify their tolerable exposure levels. This article mainly discusses support vector machines, linear discriminant analysis, decision trees, partial least squares, and algorithms based on feedforward neural networks in machine learning. It is envisaged that this article will provide scientists and users with a better understanding of machine learning and its application prospects in pesticide toxicity assessment.

Physiological sensing system integrated with vibration sensor and frequency gel dampers inspired by spider.

Recent advances in bioelectronics in mechanical and electrophysiological signal detection are remarkable, but there are still limitations because they are inevitably affected by environmental noise and motion artifacts. Thus, we develop a gel damper-integrated crack sensor inspired by the vibration response of the viscoelastic cuticular pad and slit organs in a spider. Benefitting from the specific crack structure design, the sensor possesses excellent sensing behaviors, including a low detection limit (0.05% strain), ultrafast response ability (3.4 ms) and superior durability (>300 000 cycles). Such typical low-amplitude fast response properties allow the ability to accurately perceive vibration frequency and waveform. In addition, the gel damper exhibits frequency-dependent dynamic mechanical behavior that results in improved stability and reliability of signal acquisition by providing shock resistance and isolating external factors. They effectively attenuate external motion artifacts and low-frequency mechanical noise, resulting in cleaner and more reliable signal acquisition. When the gel damper is combined with the crack-based vibration sensor, the integrated sensor exhibits superior anti-interference capability and frequency selectivity, demonstrating its effectiveness in extracting genuine vocal vibration signals from raw voice recordings. The integration of damping materials with sensors offers an efficient approach to improving signal acquisition and signal quality in various applications.

A structural study on a specific Li-ion ordered complex in dimethyl carbonate-based dual-cation electrolytes.

Dimethyl carbonate (DMC) is a linear carbonate solvent commonly used as an electrolyte for electric double-layer capacitors (EDLCs) and Li-ion batteries. However, there are serious problems with the use of DMC as an electrolyte solvent: (1) low ionic conductivity when using Li salts (e.g. LiBF4) and (2) liquid-liquid phase separation when using spiro-type quaternary ammonium salts (e.g. SBPBF4). Dual-cation electrolytes, i.e., bi-salt (SBPBF4 and LiBF4) in DMC, are promising candidates to avoid the phase separation issue and to enhance the total and Li+ conductivities. Herein, we reported a specific Li-ion structure in DMC-based dual-cation electrolytes by combining high-energy X-ray total scattering (HEXTS) and all-atom molecular dynamics (MD) simulations. Quantitative radial distribution function analysis based on experimental and simulation results revealed that the phase-separated SBPBF4/DMC (i.e., the bottom phase of 1 M SBPBF4/DMC) forms long-range ion ordering based on the structured SBP+-BF4- ion pairs. When adding LiBF4 salt into SBPBF4/DMC (i.e., dual-cation electrolyte), the ordered SBP+-BF4- structure disappeared owing to the formation of Li-ion solvation complexes. We found that in the dual-cation electrolyte Li ions form multiple Li+-Li+ ordered complexes in spite of relatively low Li-salt concentration (1 M), being a promising Li+-conducting medium with reduced Li salt usage and low viscosity.

Unsupervised Multi-Domain Progressive Stain Transfer Guided by Style Encoding Dictionary.

In histopathology, the tissue slides are usually stained by common H&E stain or special stains (MAS, PAS, and PASM, etc.) to clearly show specific tissue structures. The rapid development of deep learning provides a good solution to generate virtual staining images to significantly reduce the time and labor costs associated with histochemical staining. However, most existing methods need to train a special model for every two stains, which consumes a lot of computing resources with the increasing of staining types. To address this problem, we propose an unsupervised multi-domain stain transfer method, GramGAN, which realizes the progressive transfer through cascaded Style-Guided blocks. For each Style-Guided block, we design a style encoding dictionary to characterize and store all the staining style information. In addition, we propose a Rényi entropy-based regularization term to improve the discrimination ability of different styles. The experimental results show that our method can realize accurate transferring among multiple staining styles with better performance. Furthermore, we build and publish a special stained image dataset suitable for glomeruli segmentation (including H&E staining), where the accuracy of glomeruli detection and segmentation can be significantly improved after transferring H&E-stained images to PAS-stained and PASM-stained ones by our method. The code is publicly available at: https://github.com/xianchaoguan/GramGAN.

Low‐cost fundoscopy simulation for everyone? Evaluation of knowledge gain and student satisfaction with the Kyoto Kagaku model

Purpose: To evaluate the influence of a relatively low‐cost fundoscopy simulator, the Kyoto Kagaku Model, on the subjective learning experience and an objective knowledge gain of medical students at Saarland University Medical Center, Homburg, Germany.Methods: Medical students at the Saarland University Medical Center were enrolled in a clinical course about fundoscopic examination and pathologies. The course consisted of a theoretical part, an introduction to the practical basics of ophthalmoscopy with the Kyoto Kagaku fundoscopy simulator, and a clinical practice with dilated pupils on each other (the classical ophthalmoscopy course). They then completed two questionnaires. The first one was about the subjective learning experience and was filled out shortly after the course, the second one about the objective clinical knowledge gain in ophthalmoscopy and was filled out before the start of ophthalmoscopy training and 1 week thereafter.Results: The medical students showed a significant (p < 0.001) gain in knowledge of the fundoscopic examination and pathologies after the course with the Kyoto Kaguka Fundoscopy Simulator. Specific anatomical structures in the fundus were identified significantly (p < 0.001) more often during the simulator training compared to the classical ophthalmoscopy course. 47% of the medical students preferred a simulator‐based course, 23% a classical ophthalmoscopy course and 30% a combination of both.Conclusion: Simulator‐based training is a valuable tool for teaching medical students (and aspiring resident physicians) various skills, including those related to ophthalmology. Hands‐on courses using the Kyoto Kagaku fundoscopy simulator have been successful in increasing medical students' interest in medical simulation and ophthalmology. This model, known for its relatively low cost, is a good immersive tool for teaching the basics of direct and indirect fundoscopic examination and various retinal pathologies. Although there are still challenges to overcome, such as accessibility and cost, the future of simulator‐based training in ophthalmology looks promising.

Beam Dynamics Studies for the Target Beamlines of the High Brilliance Neutron Source

The High Brilliance Neutron Source (HBS) belongs to the class of High Current Accelerator based Neutron Sources (Hi-CANS). The driver Linac for the HBS must be able to reliably accelerate a 100 mA proton beam to an energy of 70 MeV [2, 1, 3]. The beam is sent pulse-by-pulse to three different targets via a multiplexer in the High Energy Beam Transfer (HEBT) section. Each individual proton pulse behind the multiplexer has a specific time structure in order to optimally serve the different instruments grouped around one target station. The main development steps of the HEBT are the development of a three-field septum magnet, which is an essential part of the multiplexer magnet system, the beam dynamics integration of the multiplexer magnet system into the beamline, and the ion-optical layout of the individual target beamlines.