Structural Conversion Research Articles

Liquid sculpture and curing of bio-inspired polyelectrolyte aqueous two-phase systems

Aqueous two-phase systems (ATPS) provide imperative interfaces and compartments in biology, but the sculpture and conversion of liquid structures to functional solids is challenging. Here, inspired by phase evolution of mussel foot proteins ATPS, we tackle this problem by designing poly(ionic liquids) capable of responsive condensation and phase-dependent curing. When mixed with poly(dimethyl diallyl ammonium chloride), the poly(ionic liquids) formed liquid condensates and ATPS, which were tuned into bicontinuous liquid phases under stirring. Selective, rapid curing of the poly(ionic liquids)-rich phase was facilitated under basic conditions (pH 11), leading to the liquid-to-gel conversion and structure sculpture, i.e., the evolution from ATPS to macroporous sponges featuring bead-and-string networks. This mechanism enabled the selective embedment of carbon nanotubes in the poly(ionic liquids)-rich phase, which showed exceptional stability in harsh conditions (10 wt% NaCl, 80 oC, 3 days) and high (2.5 kg/m2h) solar thermal desalination of concentrated salty water under 1-sun irradiation.

Thermo-sensitive injectable hydrogel loading with elemene-loaded liposomes for enhanced anti-tumor effect.

Due to the heterogeneity and the complexity of the tumor microenvironment, combination therapy, especially the combination of chemotherapy and photothermal therapy (PTT), had received increasing attention. However, the co-delivery of small molecule drugs for chemotherapy and photothermal agents was a key issue. Herein, we prepared a novel thermo-sensitive hydrogel loading with elemene (ELE)-loaded and nano graphene oxide (NGO)-based liposomes for enhanced combined therapy. ELE was applied as the model drug for chemotherapy because it was a natural sesquiterpene drug with broad-spectrum and efficient antitumor activity. NGO was applied as drug carrier and photothermal agent simultaneously due to its two-dimensional structure and high photo-thermal conversion efficacy. NGO was further modified with glycyrrhetinic acid (GA) to improve its water dispersion, biocompatibility and tumor-targeting ability. ELE was loaded by GA-modified NGO (GA/NGO) to prepare the liposomes designated as ELE-GA/NGO-Lip, which was further mixed with chitosan (CS) solution and β-glycerin sodium phosphate (β-GP) solution to prepare the thermo-sensitive hydrogel designated as ELE-GA/NGO-Lip-gel. The obtained ELE-GA/NGO-Lip-gel had the gelling temperature of 37°C, temperature and pH-response gel dissolution and high photo-thermal conversion effect. More importantly, ELE-GA/NGO-Lip-gel upon 808nm laser irradiation had relative high anti-tumor efficiency against SMMC-7721 cells in vitro. This research might provide a potent platform for the application of thermos-sensitive injectable hydrogel in combined tumor therapy.

Mechanical Analysis of Junction Pier of Fuzhou-Xiamen High-Speed Railway Rigid-Frame Bridge

The continuous rigid structure bridge on both sides of the Quanzhou Bay Crossing Bridge uses double-limbed thin-walled flexible piers for the junction piers between the links, and the whole bridge has no bearings. In China, the monolithic bearing-free prestressed concrete continuous rigid-frame bridge is used in railway bridges. The junction pier between the two adjacent couplets is a double-leg thin-walled flexible pier. The single leg thin-walled pier is connected with half of the pier-top segment. During the construction process, the block with numbered zero on the top of the pier is temporarily anchored and connected. Symmetrical cantilevered baskets are used on both sides for construction, and after the mid-pier cantilevered construction is completed, the temporary anchoring device for the block with numbered zero is removed. Because the structural system conversion is required in the construction, the mechanical properties of the junction pier will change greatly before and after the conversion, so it is very necessary to calculate and analyze it to master. In this paper, the finite element model of the connecting pier is established accurately, the stress and deformation of each part of the connecting pier under unfavorable working conditions is analyzed in detail, the seismic spectrum analysis under the action of common earthquake and rare earthquake is carried out, and the stress and deformation law of the structure is expounded, which can provide some reference for the construction of similar projects in the future.

Tunable lipid-coated nanoporous silver sheet for characterization of protein-membrane interactions by surface-enhanced Raman scattering (SERS)

Membrane environments affect protein structures and functions through protein-membrane interactions in a wide range of important biological processes. To better study the effects from the lipid’s hydrophilic and hydrophobic interaction with protein on different membrane regions, we developed the lipid-coated nanoporous silver sheets to provide tunable supported lipid monolayer/bilayer environments for in situ surface-enhanced Raman vibrational spectroscopy (SERS) characterizations. Under the controllable surface pressure, lipid monolayer/bilayer was coated along the microscopic curved surface of nanoporous silver sheets to serve as a cell membrane mimic as well as a barrier to avoid protein denaturation while empowering the high SERS enhancements from the underlying metallic bases allowing detection sensitivity at low physiological concentrations. Moreover, we fine-tuned the lipid packing density and controlled the orientation of the deposited lipid bilayers and monolayers to directly monitor the protein structures upon interactions with various membrane parts/positions. Our results indicate that lysozyme adopted the α-helical structure in both hydrophilic and hydrophobic interaction with lipid membrane. Interestingly, alpha-synuclein folded into the α-helical structure on the negatively charged lipid heads, whereas the hydrophobic lipid tails induced the β-sheet structural conversion of alpha-synuclein originated from its unstructured monomers. These direct observations on protein hydrophilic and hydrophobic interaction with lipid membrane might provide profound insights into the formation of the β-sheet-containing alpha-synuclein oligomers for further membrane disruptions and amyloid genesis associated with Parkinson’s disease. Hence, with the controllability and tunability of lipid environments, our platform holds great promise for more general applications in investigating the influences from membranes and the correlative structures of proteins under both hydrophilic and hydrophobic effects.Graphical

Research on energy‐saving technology of loader hydraulic torque converter based on MATLAB dynamic characteristic simulation

AbstractAt present, hydraulic transmission loaders have high automatic adaptability and convenient operation, but their transmission efficiency is low, and the intelligent degree of energy consumption regulation is limited. Strengthening the research of locking device in torque converter is an important measure to effectively reduce energy consumption. Therefore, the research uses MATLAB software and torque converter parameters to build the external characteristic curves of the engine and torque converter, and builds the dynamic model based on the working principle and locking process of the lockup clutch. The research and experimental analysis are carried out from three aspects of the lockup dynamic process of the torque converter, the lock‐up and unlocking conditions, and the change of the lockup oil pressure of the clutch. The results show that the speed difference range between pump wheel and turbine (233.08–365.44 rpm) is much lower than that of other cases (409.68–616.23 rpm) when the engine and torque converter are matched. And the fuel rate is the highest when the throttle opening of the loader is 70%, about 38%. The above results show that the locking structure of the hydraulic torque converter of the loader can effectively reduce the working vibration and improve the service life and fuel rate. And its energy‐saving application effect has an important enlightening effect on the performance optimization and resource utilization of construction machinery, and provides new ideas for improvement.

Nanoarchitectonics and Applications of Gallium‐Based Liquid Metal Micro‐ and Nanoparticles

AbstractIn recent years, gallium‐based liquid metal (GLM) is an attractive material because of its excellent characteristics such as ultra‐low melting point, high fluidity, high conductivity, self‐healing and so on. GLMs have unique properties at micro and nano scales, such as core‐shell structure, sinterability, biocompatibility and photothermal conversion ability and so on, which promote the development of relevant application directions. Therefore, various preparation methods of GLM particles and conductive connection of GLM nanoparticles through various sintering methods are reviewed in this paper. In addition, GLM particles also show great prospects in flexible circuits, sensor detection, medical treatment, energy production and other fields

Heterozygosity for cervid S138N polymorphism results in subclinical CWD in gene-targeted mice and progressive inhibition of prion conversion

Prions are proteinaceous infectious particles that replicate by structural conversion of the host-encoded cellular prion protein (PrPC), causing fatal neurodegenerative diseases in mammals. Species-specific amino acid substitutions (AAS) arising from single nucleotide polymorphisms within the prion protein gene (Prnp) modulate prion disease pathogenesis, and, in several instances, reduce susceptibility of homo- or heterozygous AAS carriers to prion infection. However, a mechanistic understanding of their protective effects against clinical disease is missing. We generated gene-targeted mouse infection models of chronic wasting disease (CWD), a highly contagious prion disease of cervids. These mice express wild-type deer or PrPC harboring the S138N substitution homo- or heterozygously, a polymorphism found exclusively in reindeer (Rangifer tarandus spp.) and fallow deer (Dama dama). The wild-type deer PrP-expressing model recapitulated CWD pathogenesis including fecal shedding. Encoding at least one 138N allele prevented clinical CWD, accumulation of protease-resistant PrP (PrPres) and abnormal PrP deposits in the brain tissue. However, prion seeding activity was detected in spleens, brains, and feces of these mice, suggesting subclinical infection accompanied by prion shedding. 138N-PrPC was less efficiently converted to PrPres in vitro than wild-type deer (138SS) PrPC. Heterozygous coexpression of wild-type deer and 138N-PrPC resulted in dominant-negative inhibition and progressively diminished prion conversion over serial rounds of protein misfolding cyclic amplification. Our study indicates that heterozygosity at a polymorphic Prnp codon can confer the highest protection against clinical CWD and highlights the potential role of subclinical carriers in CWD transmission.

QSPR Analysis of Some Drug Candidates Investigated for COVID-19 via New Topological Coindices

The COVID-19 outbreak has appeared as a matchless global threat against all humanity. Even the most developed countries have been shocked by the adversities of the COVID-19 pandemic affecting social life, especially human health. All over the world, researchers still have been studying to develop new medicines the combat outbreak. A topological index can be thought of as the conversion of a chemical structure to a real number. Topological indices are often used to provide information about the physicochemical properties and biological properties of molecules. Topological coindices are the numeric values, obtained by the complement graph of a molecular structure, which is used in Quantitative Structure Property/Activity Relationship (QSPR/QSAR) studies to evaluate the physicochemical and biological properties of compounds. In this study, we construct some new topological coindices and define the concept of CoNM -polynomial. Owing to these polynomials we pass the difficulty of calculating the topological coindices. The computing process is done for the molecular graph structure of fixed analogs of Lopinavir, Favipiravir and Ritonavir. Afterward, obtained values are evaluated in QSPR modeling via linear and quadratic regression analysis to examine some physicochemical properties of the analog medicines such as enthalpy of vaporization (E), flash point (FP), molar refractivity (MR), polarizability (P), surface tension (T), molar volume (MV).

Fluoride Retention in Root Dentin following Surface Coating Material Application.

This study aimed to use an in-air micro-particle-induced X-ray/gamma emission (in-air µPIXE/PIGE) system to evaluate tooth-bound fluoride (T-F) in dentin following the application of fluoride-containing tooth-coating materials. Three fluoride-containing coating materials (PRG Barrier Coat, Clinpro XT varnish, and Fuji IX EXTRA) and a control were applied to the root dentin surface of human molars (n = 6, total 48 samples). Samples were stored in a remineralizing solution (pH 7.0) for 7 or 28 days and then sectioned into two adjacent slices. One slice of each sample was immersed in 1M potassium hydroxide (KOH) solution for 24 h and rinsed with water for 5 min for the T-F analysis. The other slice did not undergo KOH treatment and was used to analyze the total fluoride content (W-F). The fluoride and calcium distributions were measured in all the slices using an in-air µPIXE/PIGE. Additionally, the amount of fluoride released from each material was measured. Clinpro XT varnish demonstrated the highest fluoride release among all the materials and tended to show high W-F and T-F and lower T-F/W-F ratios. Our study demonstrates that a high fluoride-releasing material shows high fluoride distribution into the tooth structure and low conversion from fluoride uptake by tooth-bound fluoride.

Photo- and Temperature-Induced Reversible Structural Transformation between Dodecanuclear and Pentadecanuclear Gold(I) Sulfido Complexes.

Stimuli-responsive structural transformation has attracted much attention for its potential to mimic the behavior of biological transformations and functions. Here, two unprecedented dodecanuclear and pentadecanuclear gold(I) sulfido clusters (denoted trans-Au12 and trans-Au15, respectively) with impressive stimuli-responsive interconversion have been obtained by taking advantage of the judiciously designed tridentate phosphine ligand Ltrans as the building block. Both UV light and temperature can be applied to trigger the structural conversions between trans-Au12 and trans-Au15. In addition, NMR, high-resolution electrospray ionization mass spectrometry, and UV-vis absorption spectroscopy have been employed to monitor the transformation process and decipher the mechanism of structural conversion. This work not only provides a paradigm to investigate photo-induced cluster-to-cluster transformation based on polydentate phosphine ligands but also offers a new direction for the construction of the stimuli-responsive materials.

On-line intermittent growth of carbon nanotubes in a self-made tapered fluidized bed reactor at different inlet distances

The effect of the gas inlet distance on the quality and yield of carbon nanotubes (CNTs) is studied through the on-line intermittent method via a previous self-made tapered fluidized bed reactor (TFBR). The CNTs are catalytically grown on the Fe-Co-Mo/Al2O3 and Fe/Mo/Vermiculite catalyst at different inlet distances (DIDs), which clarify the effect of inlet distance and explore the optimum location. The whole process of CNTs growth in the TFBR without a distributor is explored. The effects of DIDs on catalyst flow and CNTs growth are discussed as well. Additionally, the morphology, quantity and quality of multi-walled carbon nanotubes (MWCNTs) are systematically characterized by using scanning electron microscopes (SEM), Brunauer Emment Teller (BET) and Raman Spectra. The results show that the CNTs prepared at 50 mm from the bottom of the cone have lower ash content and defect, and higher quality compared to other locations. That is, the airflow from 1/2–3/4 of the cone bottom could improve the catalytic performance of the catalyst, which results in the CNTs prepared have an excellent structure and high-efficiency carbon conversion rate.

EASRAPP: An Open-Source Semiautomatic Python GUI-Based Application for Extraction and Analysis of Surface Ruptures in a Large Earthquake

Abstract Earthquake surface ruptures record the kinematics of the rupture behavior and rheology of the fault zone. General methods of acquiring coseismic surface ruptures, including the field geological survey and the visual interpretation of remote sensing images, are generally time consuming and challenging to obtain detailed features of surface ruptures. Here, we developed an open-source semiautomatic Python graphical user interface-based application named EASRAPP (An Application for Extraction and Analysis of Surface Ruptures). EASRAPP is a graphical Python application that provides an interactive, user-friendly framework for semiautomatically extracting and analyzing earthquake surface ruptures and associated quantitative parameters. It consists of four main modules for obtaining the region of interest for surface ruptures in a remote sensing image, extracting surface ruptures, editing the vector extraction results, and analyzing the width of the surface rupture zone and strikes of all surface ruptures. Moreover, some additional functions are available, including data structure conversion for vector and raster data, vector merging, raster mosaicing, and batch cropping from multiple large images to many small images. EASRAPP is written in Python 3, based on several open-source Python packages such as Tkinter, SciPy, and so forth. Because of its modular design, it is convenient to modify the code and add new functionalities to a collaborative development environment. Furthermore, the output of the editing module may serve as a machine learning or deep learning training dataset, and offer conditions for detailed kinematic analysis and acquiring accurate width of the active fault deformation zone. EASRAPP was tested on a single unmanned aerial vehicle image to demonstrate all modules and tools. In addition, EASRAPP was also applied to other drone and satellite images to extract surface ruptures from recent and historical earthquakes. Our results indicate that: (1) the tool can quickly extract the fine structures of surface fractures, (2) EASRAPP can be used to extract surface ruptures generated by historical events, and (3) it can be applied to high-resolution aerial and satellite images.

Review on modeling and control of megawatt liquid flow energy storage system

Flow battery has recently drawn great attention due to its unique characteristics, such as safety, long life cycle, independent energy capacity and power output. It is especially suitable for large-scale storage system and has a good application prospect. In this paper, the overall structure of the megawatt-level flow battery energy storage system is introduced, and the topology structure of the bidirectional DC converter and the energy storage converter is analyzed. Secondly, the influence of single battery on energy storage system is analyzed, and a simulation model of flow battery energy storage system suitable for large power grid simulation is summarized. The model of the whole system of flow battery is summarized from the grid-connected side and the energy storage system itself. The model of flow battery energy storage system should not only accurately reflect the operation characteristics of flow battery itself, but also meet the simulation requirements of large power grid in terms of simulation accuracy and speed. Finally, the control technology of the flow battery energy storage system is discussed and analyzed. The multi-DC/DC control strategy on the DC side and the parallel operation control strategy of the energy storage converter on the AC side are compared and analyzed. The advantages and disadvantages of each control method are analyzed accurately, which can provide reference for the modeling and control strategy of the megawatt flow battery energy storage system.

Two-step structural changes in M3 muscarinic receptor activation rely on the coupled Gq protein cycle

G protein-coupled receptors (GPCRs) regulate diverse intracellular signaling pathways through the activation of heterotrimeric G proteins. However, the effects of the sequential activation–deactivation cycle of G protein on the conformational changes of GPCRs remains unknown. By developing a Förster resonance energy transfer (FRET) tool for human M3 muscarinic receptor (hM3R), we find that a single-receptor FRET probe can display the consecutive structural conversion of a receptor by G protein cycle. Our results reveal that the G protein activation evokes a two-step change in the hM3R structure, including the fast step mediated by Gq protein binding and the subsequent slower step mediated by the physical separation of the Gαq and Gβγ subunits. We also find that the separated Gαq-GTP forms a stable complex with the ligand-activated hM3R and phospholipase Cβ. In sum, the present study uncovers the real-time conformational dynamics of innate hM3R during the downstream Gq protein cycle.

Output power regulation system for portable micro fuel cell systems

This article presents an output power regulation system for micro fuel cells to help enhance the stability of the fuel cell in a portable micro power system. The structure of an MCU-controlled DC-DC converter is proposed. Then, the output characteristics of a selected fuel cell stack and the DC-DC converter’s power control functions are estimated by a system-level model. Based on the simulation results, the model provides a power regulation system which is implemented, and the test shows that it fulfills its intended function and the output power is regulated to a fixed level of 5 W–40 W with good efficiency.

Bipolar DC output fed grounded DC-AC converter for photovoltaic application

Introduction. In recent years the usage of electricity has increased tremendously as the electrical needs and loads got increased. Hence the researchers focused on the electricity generation from renewable sources in order to promote sustainable green environment. Owing to the lesser cost and more reliable high efficiency system with reduced use of equipments became prominent for the grid connected photovoltaic single phase systems. The novelty of this proposed converters are to reduce total power loss and to analyze the performance of the converter under various modulation index and to have lesser harmonics using sinusoidal pulse width modulation technique for both T-type and F-type inverter. Interest of the work is to merge two DC-DC converters which have same output voltage in order to have transformer less utilization of power. This has given pathway to develop a new DC-DC converter network by merging the common input nodes of CUK and SEPIC converter. Purpose. This similar structure of both converters made it easy to combine the input stages of and to get bipolar output. Methods. Here we can get bipolar output without the utilization of transformer which minimizes the overall size of the proposed system. In this paper, a combined CUK-SEPIC based grid connected transformerless inverter for photovoltaic application is suggested. Results. The suggested converter is simulated using MATLAB and the results were discussed. Further the circuit is extended with a 1 kW F-type inverter to demonstrate grid connection of the converter. Practical value. This converter can be implemented for photovoltaic applications for obtaining the bipolar DC output from the DC source.

BF3-assisted insolubilization switching toward bilayer π-conjugated polymer film

The fabrication of a bilayer thin film by spin-coating on a π-conjugated polymer film is a crucial step in the processing of organic materials for optoelectronic applications. However, the process is difficult because it depends on a dramatic tuning of the polymer chemical structures used or an irreversible solid-state conversion of the chemical structure. Herein, we report a bilayer π-conjugated polymer film prepared by chemical modification of the polymer, i.e., BF3 coordination-insolubilization by desorption solubilization. Poly[(9,9-dioctylfluorene-2,7-diyl)-alt-(pyridine-2,6-diyl)] (PPF8) is soluble in many organic solvents, but its film became insoluble owing to the BF3 coordination. BF3-assisted insolubilization switching was easily investigated by color (fluorescence) changes. Further film formation on the insoluble film via spin-coating of a head-to-tail poly(3-hexylthiophene) (P3HT) solution produced the bilayer film. The PPF8 was able to remove the BF3 coordination by triethylamine vapor treatment.

Decoding the Roles of Amyloid-β (1-42)'s Key Oligomerization Domains toward Designing Epitope-Specific Aggregation Inhibitors.

Fibrillar amyloid aggregates are the pathological hallmarks of multiple neurodegenerative diseases. The amyloid-β (1-42) protein, in particular, is a major component of senile plaques in the brains of patients with Alzheimer's disease and a primary target for disease treatment. Determining the essential domains of amyloid-β (1-42) that facilitate its oligomerization is critical for the development of aggregation inhibitors as potential therapeutic agents. In this study, we identified three key hydrophobic sites (17LVF19, 32IGL34, and 41IA42) on amyloid-β (1-42) and investigated their involvement in the self-assembly process of the protein. Based on these findings, we designed candidate inhibitor peptides of amyloid-β (1-42) aggregation. Using the designed peptides, we characterized the roles of the three hydrophobic regions during amyloid-β (1-42) fibrillar aggregation and monitored the consequent effects on its aggregation property and structural conversion. Furthermore, we used an amyloid-β (1-42) double point mutant (I41N/A42N) to examine the interactions between the two C-terminal end residues with the two hydrophobic regions and their roles in amyloid self-assembly. Our results indicate that interchain interactions in the central hydrophobic region (17LVF19) of amyloid-β (1-42) are important for fibrillar aggregation, and its interaction with other domains is associated with the accessibility of the central hydrophobic region for initiating the oligomerization process. Our study provides mechanistic insights into the self-assembly of amyloid-β (1-42) and highlights key structural domains that facilitate this process. Our results can be further applied toward improving the rational design of candidate amyloid-β (1-42) aggregation inhibitors.

Ultra high step‐up soft‐switching DC/DC converter using coupled inductor and interleaved technique

AbstractIn this paper, a new ultra high step‐up soft‐switching DC/DC converter using coupled inductor and interleaved technique is presented. The primary side of the coupled inductors in up section and down section will be charged by the input power supply. The stored energy of the coupled inductors (at primary and secondary sides) is discharged to the output capacitors in up and down sections. Also, the capacitors on the coupled inductors path have clamped capacitors that cause the voltage stress across the power semiconductors to be low. Al diodes in up and down sections except output diodes are working at zero current switching turn‐off. Therefore, the reverse recovery problems of the proposed converter will be majorly solved. Therefore, power losses of the proposed converter will be decreased by using switches with lower on‐state resistance RDS(on) and lower rating power diodes. In addition, the leakage inductor causes to exclusive the current falling balance of the output diodes, significantly. In order to clarify the main advantages of the proposed converter, comparison between the proposed converter and other structures is provided. Finally, the proposed converter with turn ratio N(N2/N1) = 2 in about 300 W with operating 50 kHz is tested with real‐time TYPHOON HIL‐404 emulator in the laboratory.

Performance Analysis of Energy Balancing Methods for Matrix Modular Multilevel Converters

Modular multilevel converters (MMCs) achieve voltage scalability through the series connection of cells, each with its own capacitance. However, this converter structure using floating energy storage elements increases the control complexity significantly. The voltages of each capacitance must be controlled to their respective setpoints to ensure the correct operation of the converter. Relying on the use of circulating currents, which are unobservable at the converter terminals, the energy can be exchanged among the branches. Three control principles resulting in three different implementations are thoroughly explained and their dynamic performance is compared. The results are verified using a hardware-in-the-loop (HIL) platform simulating a hydro power plant using a matrix modular multilevel converter connected between a 6.6 kV grid and a 6 kV synchronous machine.