Stable Skeleton Research Articles

Rapid mechano-chemical ball-milling synthesis of novel low-cost petroleum pitch based porous organic polymers for ammonia adsorption

Ammonia (NH3) inevitably experiences emission and leakage during its production, transition and application. Therefore, the development of effective NH3 adsorption and storage methods has become an important issue of concern. Porous organic polymers (POPs) with low density and high porosity structure are expected to be used for the capture of NH3. In this work, a series of POPs (PP-BM-1, PP-BM-2 and PP-BM-3) were developed by using a cheap petrochemical by-product petroleum pitch (PP) as raw material and three different crosslinking agents through fast and high-efficient ball-milling synthetic strategy (reaction time: 2 h). The resulting polymers exhibited stable skeleton, high BET surface area (580–867 m2 g−1) and abundant micro-pores, which were beneficial for the adsorption of NH3. The characterization results of NH3 adsorption indicated that the adsorption capacities of resulting polymers could up to 14.97 and 12.86 mmol g−1 at 273 K and 298 K, respectively. The POPs also showed good recyclability, with only a slight decrease in NH3 capacity after 5 adsorption/desorption cycles. Overall, this study could provide a new approach for the design and synthetic strategy of NH3 adsorption materials, which with a promising prospect for large-scale production and widespread application.

An Efficient and Stable MXene-Immobilized, Cobalt-Based Catalyst for Hydrogen Evolution Reaction

Hydrogen (H2) is considered to be the best carbon-free energy carrier that can replace fossil fuels because of its high energy density and the advantages of not producing greenhouse gases and air pollutants. As a green and sustainable method for hydrogen production, the electrochemical hydrogen evolution reaction (HER) has received widespread attention. Currently, it is a great challenge to prepare economically stable electrocatalysts for the HER using non-precious metals. In this study, a Co/Co3O4/Ti3C2Tx catalyst was synthesized by supporting Co/Co3O4 with Ti3C2Tx. The results show that Co/Co3O4/Ti3C2Tx has excellent HER activity and durability in 1 mol L−1 KOH, and the overpotential and Tafel slope at 10 mA·cm−2 were 87 mV and 61.90 mV dec−1, respectively. The excellent HER activity and stability of Co/Co3O4/Ti3C2Tx can be explained as follows: Ti3C2Tx provides a stable skeleton and a large number of attachment sites for Co/Co3O4, thus exposing more active sites; the unique two-dimensional structure of Ti3C2Tx provides an efficient conductive network for rapid electron transfer between the electrolyte and the catalyst during electrocatalysis; Co3O4 makes the Co/Co3O4/Ti3C2Tx catalyst more hydrophilic, which can accelerate the release rate of bubbles; Co/Co3O4 can accelerate the adsorption and deionization of H2O to synthesize H2. This study provides a new approach for the design and preparation of low-cost and high-performance HER catalysts.

All-solid-waste-derived CaO-based sorbents for simultaneously enhanced calcium looping CO2 capture and thermochemical energy storage

Calcium looping (CaL) process relying on CaO as high-temperature CO2 sorbents is a prospective alternative technology for simultaneously cyclic CO2 capture and thermochemical energy storage. However, the cyclic stability and the energy storage density of the CaO-based sorbents decay drastically over repeated carbonation-calcination cycles. Herein, we yielded CaO-based sorbents derived from all industrial solid wastes with carbide slag (CS) as precursor and coal fly ash (CFA) as stabilizer featuring superior carbonation characteristics, stable CO2 cyclic uptake and high thermochemical energy storage density over multiple operation cycles. The optimal sorbent (CCS–H-G-CFA-D) exhibited a high initial CO2 uptake of 0.38 gCO2/gsorbent, superior cyclic stability with an average decay rate of 1.05% per cycle and remarkably stable energy storage density of 1375 kJ/kg, retaining 89.5% after 10 repeated cycles. Thereby, the simultaneously enhanced cyclic CO2 capture and thermochemical energy storage are attributed to adding CFA stabilizers in CS-derived CaO-based sorbents, forming stable skeleton to alleviate sintering, improving the uniform mixing degree between sorbent particles and promoting the carbonation reaction via synergistic effect. This simple and eco-friendly approach of cost-effective sorbents totally derived from industrial solid wastes provides a new avenue for large-scale practical CO2 capture and energy storage processes.

Fully conjugated radical-doped COF for near-infrared photothermal conversion, C-3 thiocyanation of indoles and oxidative coupling of amines

Radical-doped covalent organic frameworks (COFs) have received much interest as it confers additional functions such as photomodulated electrical conductivity, magnetism, and photochromism. Such COFs are relatively underexplored, however, mainly due to the lack of suitable highly photoactive building blocks. Herein, a rare radical-doped fully conjugated COF (PDI-COF) was rationally designed and prepared by incorporating photoactive perylenediimides (PDIs) into its framework. Characterization of the product PDI-COF not only confirmed its porous and stable skeleton, but also revealed the radical derived from photoinduced electron transfer between the PDI and electron donor. The fully conjugated and radical-doped characteristics enable the effective realization of near-infrared photothermal conversion in this COF. Moreover, this radical-doped COF can efficiently generate superoxide radical anions under light irradiation, which promote the photocatalytic C-3 thiocyanation of indoles and the oxidative coupling of amines in high yield and good recyclability at room temperature and without additives. This study demonstrates that introducing a photoactive organic dye into a COF is an effective approach to photothermal conversion materials and metal-free porous photocatalysts for application in photothermal therapy and photocatalytic organic synthesis.

Tailored 2D conjugated polymers for pseudocapacitive proton storage

2D conjugated polymers (2D-CPs) are currently attracting substantial attention as host materials in electrochemical energy storage. They show some intriguing properties, such as high conductivity (by elevating the conjugated degree), adjustable redox activity (by controlling the monomers), and stable skeleton structure (low solubility in electrolytes). Herein, two aza-based 2D-CPs with different conjugation degrees are designed and developed for pseudocapacitive proton storage. The detailed electrochemical analysis shows that the highly conjugated 2D-CP (2D-HCP) demonstrates an inferior performance compared to partially conjugated 2D-CP (2D-PCP), especially in terms of the high-rate performance. Though combining various in-situ/ex-situ spectroscopy analyses and theoretical simulation, the reason behind this performance is revealed and is associated with the different solid-state proton diffusion kinetics in these two 2D-CPs. We believe this new understanding can be leveraged to design and develop more suitable 2D-CPs for electrochemical energy storage.

Study of Various Modalities of Management of Lower One-third Leg Defects in a Tertiary Care Hospital

Background: Lower extremity reconstruction is essential to plastic surgery and focuses on treating wounds and defects secondary to trauma, cancer, or chronic disease processes. Anatomical features of the lower third of the leg like subcutaneous bone surrounded by tendons with no muscles and vessels in isolated compartments with little intercommunication between them make the coverage of the wounds in the region a challenging problem. Aim: to study the various modalities of surgical management of lower 1/3rd leg defects. The study also aims to study the defect size and region in planning various flaps possible in the reconstruction ladder. Methods: The study was conducted from September 2014 to June 2017 on patients admitted to the Department of Burns, Plastic & Reconstructive Surgery and referred patients from the Department of General Surgery & Orthopaedic Surgery, S C B Medical College & Hospital, Cuttack. The Study includes all lower 3rd Leg defect varieties for different surgical treatment modalities. Results: Various reconstructive methods were used to cover the lower 1/3rdleg defects; the maximum was the free muscle transfer in 9 cases. The following typical flap used was the reverse sural flap. Conclusion: The goal in lower limb reconstruction involves needing a stable skeleton, allowing weight-bearing status, with adequate soft tissue coverage to nourish and protect the underlying bone. What one would use for reconstruction depends upon the surgeon’s familiarity and comfort levels with the technique as much as the various circumstances.

Lightweight TiC based cermet fabricated by a pre-solid phase sintering-assisted pressureless infiltration process

This paper introduces a novel process, known as pre-solid phase sintering-assisted pressureless infiltration (PSPS-PI), aimed at addressing issues related to the segregation of hard particles and excessive porosity in the manufacturing of lightweight cermet based on TiC. The PSPS-PI process involves compressing a green TiC powder compact with a minor Ni powder addition, followed by vacuum-based solid-phase sintering to create a fully consolidated TiC preform. This study explores the influence of TiC particle size and Ni content on the microstructure and properties of TiC–Cu composites, conducting a comparison with direct pressureless infiltration (D-PI). The results indicate that the high-melting-point Ni element promotes the formation of sintering necks between TiC and Ni, aiding in the consolidation of TiC particles. The stable skeleton ensures that TiC particles remain in their initial positions during subsequent pressureless infiltration, effectively preventing TiC powder segregation. TiC and Ni create a dissolutive wetting system during pressureless infiltration. The formation of the Ni2SnTi intermetallic compound significantly enhances the wettability with Cu alloy, leading to a reduction in porosity and the occurrence of crack defects within the composite. As particle size decreases, the preform's porosity decreases, resulting in a reduced proportion of soft metal binder and lower residual stress. Consequently, finer TiC powder leads to improved cermet hardness and a reduction in the number of micro-crack defects. In general, PSPS-PI allows for the attainment of low porosity, a uniform microstructure, enhanced hardness, and outstanding wear resistance in the lightweight cermet based on TiC with the appropriate TiC particle size (D50 = 10.2 μm), achieving a remarkable hardness of 642.9 (Hv30) and excellent toughness.

CT-based investigation on internal structure evolution for high-speed railway graded aggregate materials during vibratory compaction

The research gap on the internal structure evolution (ISE) of the high-speed railway graded aggregate (HRGA) materials during vibratory compaction has resulted in challenges in exploring its compaction physical-mechanical properties. Based on a self-developed vibratory compaction instrument (SVCI), a new assessment framework was established to evaluate physical-mechanical evolution properties during vibratory compaction, including the revised dry density ρrd, the revised soil stiffness Krb, and the revised modulus of subgrade reaction K20. The X-Ray computed tomography (X-Ray CT) tests of an HRGA specimen at different compaction stages were carried out to characterize the physical-mechanical evolution properties. The results show that during vibratory compaction, the ρrd presents a rapidly increasing-slowly increasing-continuously stable evolution, while Krb and K20 shows a rapidly increasing-slowly decreasing characteristic. The compaction locking point Tlp is proposed to quantify the inflection point of mechanical properties during vibratory compaction, which is related to the gradation types of the HRGA materials. Before achieving the compaction locking point Tlp, coarse grains gradually deflect toward horizontal orientation to form a stable skeleton with insignificant crushing. Approximately 60% of coarse grains in the horizontal direction can achieve a stable skeleton under the action of the excitation force. After achieving Tlp, the coarse grains present the localized crushing phenomenon at the contact points due to further compaction, and it indicates the destruction of the stable skeleton. The overall shape of the coarse grains remains unchanged, but their surface corners are gradually rounded. The experimental results can make a significant contribution to the filed for further investigating the vibratory compaction mechanism and enhancing the compaction quality control system.

Boosting the Intrinsic Stability of Lithium Metal Anodes by an Electrochemically Active Encapsulating Framework

AbstractThe lithium metal anode (LMA) is a promising technology to promote the energy density of secondary batteries. However, the coupled growth of surface corrosion and deposited lithium with high reactivity causes capacity fading and safety hazards, especially at high temperatures. Great efforts have been focused on preventing the LMA from direct contact with electrolytes to extend its lifespan, but few pay attention to its stability at high temperatures, which is crucial to battery safety. Herein, a 3D Li22Sn5‐based interpenetrated skeleton is introduced into the bulk of LMA with mechanical kneading, which enables a LMA with fast and stable cycles at high temperatures and improved safety under thermal abuse. The Li22Sn5 skeleton acts as a solid electrolyte inside the bulk, allowing rapid Li+ ion transport and homogenous lithium stripping/plating into the porous bulk through Li/Li22Sn5 interface. The encapsulating framework expands the electrochemically active area and limits its exposure to the electrolyte, enabling a LMA with steady cyclability even at 60 °C. Trapping lithium inside the thermally stable skeleton postpones the catastrophic exothermal reactions between lithium and electrolytes. The strategy for constructing a 3D encapsulating lithiophilic framework is promising for creating safe and stable lithium metal batteries working under harsh circumstances.

Optimization of aggregates skeleton using laser-scanning technology and discrete element method

The skeletonof aggregates hasasignificanteffecton the performance of porous asphalt mixtures. In this study, laser-scanning technology was utilized to obtain two-dimensional digital images of four groups of aggregates with different particlesizes. Digitalimage processing technology was used to obtain the basic dimensional indicessuch asarea, perimeter, and equivalent ellipse of aggregate particles. Based ontheseindices, the morphological characteristics of theaggregates,including aspect, roundness, andangularity,were evaluated.Then,virtual uniaxial penetration tests were simulated via the discrete element method (DEM) and verified by the results of laboratory uniaxial penetration tests. On this basis, the visualization design of the optimal main skeleton for the porous asphalt mixture was conducted. Results show that the shapes of the aggregateswereclose to cubes. Aggregates with sizes greater than 4.75 mmhada more significant structural effect on the skeleton than those with sizes smaller than 2.36 mm. Coarse aggregatescouldform a stable skeleton by interlocking with each other, whereas the skeleton formed by fine aggregateswasfragile. Coarse aggregates primarilywithstoodthe external load while fine aggregates primarilylimitedthe displacement of coarse aggregates. The optimal main skeleton designed by combining the DEM with the laser-scanning technology can provide new possibilities for the gradation design of porous asphaltmixtures.

Navigating Visible‐Light‐Triggered (aza and thia) Paternò‐Büchi Reactions for the Synthesis of Heterocycles

AbstractHarnessing visible light to trigger (aza and thia) Paternò‐Büchi reaction injects new vitality into [2+2] photocyclization reaction and enable impressive reactivity modes. The popular (aza and thia) Paternò‐Büchi reaction is one of the most efficient ways to synthesize strained four‐membered heterocycles. Recently, visible‐light‐triggered (aza and thia) Paternò‐Büchi reactions have received considerable attentions as this strategy has overcome some long‐standing challenges, and remarkable achievements have been made within this field. Strained four‐membered heterocyclics with favorable properties provide a perfect combination of stable skeletons for pharmaceutical chemistry and reaction intermediates for further transformation. In this review, we highlight the most recent advances in visible‐light‐triggered (aza and thia) Paternò‐Büchi reaction with an emphasis on reaction mechanism and applications. Organization of the review follows a subdivision according to reaction type and substrate classes.

Survey of Noise-Against Techniques for Extracting Stable Skeleton

Stable skeletons are promising as a compact, concise, and efficient descriptor since they can reflect much critical information about the original object, such as topology, connectivity, etc. However, extracting stable skeletons from images is very challenging since most existing skeleton extraction methods, also named skeletonization methods in some literature, are sensitive to noise, which limits the application of the skeletons in the recognition field. Many denoising methods have been proposed to extract stable skeletons to overcome this problem. However, up to now, there are few review papers to conclude these denoising methods and present their pros and cons. Therefore, In this paper, we survey existing denoising techniques for extracting stable skeletons from images. We first categorize these denoising methods, analyze their core idea, and then present their pros and cons for comparison. In addition, we also offer the potential research direction and possibly challenge.

Hydro-mechanical behavior of unsaturated intact paleosol and intact loess

Many geo-hazards occurred in regions incorporating loess-paleosol sequences. Understanding the hydro-mechanical behavior of unsaturated intact paleosol and intact loess is a prerequisite to address these geo-hazards. So far, the loess has been extensively investigated, while the study of paleosol is rare. This study investigates the unsaturated hydro-mechanical behavior of intact paleosol and intact loess, including water retention, compression, and collapse. The study of intact loess serves as a benchmark for that of intact paleosol. Results show that the intact paleosol and intact loess have similar air entry value (AEV) and average degree of hysteresis in WRC, although the former soil has a 20.2% smaller void ratio and a 38.8% larger clay fraction. This could be attributed to the larger volume of mega-pores (diameter > 360 μm) owned by the intact paleosol, which offset density and clay fraction effects on the AEV and hysteresis in WRC. On the other hand, the intact paleosol has a smaller structure permitted space (i.e. the area bounded by the compression curves of reconstituted and intact specimens) than the intact loess at a given suction. This is because that point-to-point and point-to-face contacts are widely observed between particles in the intact loess, while face-to-face particle contacts dominate in the intact paleosol. The former particle arrangement results in a metastable skeleton, while a stable skeleton is expected for the latter particle arrangement. In addition, the maximum collapse potential of the intact paleosol, which is calculated by the compression curves under suctions of 200 kPa and zero, is 42.8% smaller than that of the intact loess, mainly because of the metastable skeleton of the latter soil.

Facile synthesis of GSH-triggered skeleton-cleavable hyperbranched polymer prodrug as unimolecular micelles for tumor-specific camptothecin delivery

Prodrug unimolecular micelles based on dendrimers or hyperbranched polymers have attracted intense interest in tumor chemotherapy. The preparation of the former one is usually cumbersome, while the stable skeleton in the latter one restricts the drug release. Here, GSH-triggered skeleton-cleavable hyperbranched polymer prodrug was designed via a “Bottom-up” construction strategy, by the self-condensing vinyl polymerization (SCVP) of GSH-sensitive prodrug monomer MA-SS-CPT and PEGMA with a GSH-sensitive inimer MA-SS-Br. It could self-assemble into stable unimolecular micelles, possessing GSH-triggered drug release and disintegration of the hyperbranched skeleton. So, they showed an excellent tumor-specific CPT release in the in vitro drug release and consequently tumor-specific cytotoxicity with an enhanced tumor cell growth inhibition than the free CPT.

Range of motion required for Auslan: a biomechanical analysis.

Auslan is used by the Australian deaf community and relies heavily on hand, wrist, and elbow movement. Upper limb injury or dysfunction may require surgical intervention to alleviate pain and provide a stable skeleton for function, leading to partial or complete reduction in motion. The aim of this study was to assess the wrist, forearm, and elbow motion required to communicate via Auslan, to tailor optimal interventions in this population. A biomechanical analysis was conducted on two native Auslan communicators, who signed 28 pre-selected and common Auslan words and phrases. Sagittal plane wrist and elbow motion was found to be of greater importance than axial plane forearm rotation. Relative elbow flexion and generous wrist motion was common for many of the words and phrases, while end-range elbow extension was not recorded. The maintenance of wrist and elbow motion should be prioritized when selecting surgical interventions for patients who communicate using Auslan.

Improvement of selenium adsorption performance at high temperature by CaO/ZSM-5 composite sorbents

ABSTRACT Selenium in flue gas from coal combustion, released into the atmosphere, will affect the environment and human health greatly. The adsorption method can achieve good control of selenium emission, by using CaO as adsorbent, but CaO is easy to sinter at high temperature, resulting in the decrease of adsorption capacity. Therefore, thermostability ZSM-5 molecular sieve was added to prepare composite adsorbent to improve the adsorption performance for selenium at high temperature. CaO/ZSM-5 composite adsorbent was prepared by impregnation method, and its adsorption performance and mechanism were studied. The results show that the composite adsorbent shows stronger adsorption capacity at high temperatures. The mixing ratio has a great influence on the microstructure of the composite adsorbent influencing the adsorption capacity. When the ratio is 1:1, the adsorption efficiency of the composite adsorbent shows a good performance. At 900°C, the adsorption efficiency of Z1C1(ZSM-5/CaO = 1:1 wt%) can still maintain 67%, which is 32% higher than that of CaO. Si and Al in the composite adsorbent have different effects on the improvement of microstructure. The existence of Si is conducive to maintaining the stable skeleton of the composite adsorbent, improving anti-sintering, while the addition of Al tends to improve the porosity, furtherly ameliorating the structure of the composite adsorbent for high-temperature adsorption.

Noise-Against Skeleton Extraction Framework and Application on Hand Gesture Recognition

Extracting stable skeletons from noisy images is a challenging problem since the skeletonization method is prone to be affected by inner and border noise. Although many methods have been proposed in the past for increasing the antinoise ability of skeletonization methods, most of them either only overcome border noise or, at the cost of lost topology, degrade the effects of two noises. In this paper, we propose a skeleton extraction framework to enhance the robustness of the existing skeletonization method against both inner and border noise. In our approach, we first use the different scales of Gaussian filters to smooth the input image and obtain multiple representations. Then, binarization and skeletonization were performed to produce a series of binary images and a series of skeletal images. Next, we use our measure on these binary and skeletal images to find the most suitable skeleton. Since our measure considers both the skeleton image changes and binary image changes caused by using a filter, the selected skeleton is sufficiently robust and has all the necessary skeletal branches. The inner noise experiment and border noise experiment are conducted for comparison. From the perspective of the measure of the rate of variation in the skeleton, the proposed framework can reduce the inner noise by approximately 92% and the border noise by approximately 40%. In addition, the experiment on static hand gesture recognition has demonstrated that the introduction of our framework can increase up to 11% mean recognition accuracy.

De Novo Design of a Highly Selective Nonpeptide Fluorogenic Probe for Chymotrypsin Activity Sensing in a Living System.

Chymotrypsin, an extensively known proteolytic enzyme, plays a substantial role in maintaining physiological functions, including protein digestion, immune response, and tissue repair. To date, intense attention has been focused on the invention of efficient and sensitive chemical tools for chymotrypsin activity measurement. Among them, the "nonpeptide"-based chymotrypsin probe design strategy utilizing the esterase activity of chymotrypsin has been well-developed due to its low cost and high atom-economy feature. However, the ester-bond-based nature of these probes make them possibly vulnerable to esterases and active chemicals. These defects strictly restricted the application of the previously reported probes, especially for imaging in living systems. Therefore, to acquire fluorogenic probes with sufficient stability and specificity for chymotrypsin sensing in a complicated biological environment, a more stable skeleton for nonpeptide-based chymotrypsin probe construction is urgently needed. Herein, a novel nonpeptide-based fluorogenic probe for specific chymotrypsin activity sensing was designed and synthesized by the substitution of an ester-based linker with a heptafluorobutylamide moiety. The acquired probe, named TMBIHF, showed high selectivity toward various enzymes and reactive chemicals, while it retained high sensitivity and catalytic efficiency toward chymotrypsin. Moreover, TMBIHF was successfully applied for monitoring chymotrypsin activity and pancreas development in live zebrafish, specific sensing of exogenous and endogenous chymotrypsin in nude mice, and visualizing chymotrypsin-like activity-dependent cellular apoptosis, thus providing an alternative and reliable way for chymotrypsin-targeted biosensor or prodrug construction.

Advances in Fine Structure Optimizations of Layered Transition‐Metal Oxide Cathodes for Potassium‐Ion Batteries

AbstractPotassium‐ion batteries (PIBs) have attracted significant research interest in the context of driving the advancement of grid energy storage due to K's elemental abundance and high theoretical output voltage. The main challenge facing PIBs is to find suitable cathode materials with fast transport kinetics and stable framework structures to intercalate/de‐intercalate the large‐size K+. Among these candidates, transition‐metal layered oxides are have excellent potential and have been extensively exploited due to their stable skeleton structure, simple synthetic chemistry, and high working potential. Herein, the current research status and prospects of layered transition‐metal oxide cathodes are summarized, especially focussing on the fine structure optimization engineering and energy storage mechanism. In addition, a brief overview of the research on advanced characterization techniques for PIBs is introduced in detail. Finally, the main research directions and hot spots of new‐type transition‐metal layered oxide cathode are also predicted, in order to guide the future development of advanced PIBs.

Fast and Regulated Zinc Deposition in a Semiconductor Substrate toward High‐Performance Aqueous Rechargeable Batteries

AbstractRechargeable aqueous zinc‐ion batteries are considered as ideal candidates for large‐scale energy storage due to their high safety, eco‐friendliness, and low cost. However, Zn anode invites dendrite growth and parasitic reactions at anode‐electrolyte interface, impeding the practical realization of the battery. In this study, the electrochemical performance of the Zn‐metal anode is proposed to improve by using a 3D ZnTe semiconductor substrate. The substrate features high zincophilicity, high electronic conductivity and electron affinity, and a low Zn nucleation energy barrier to promote dendrite‐proof Zn deposition along the (002) crystal plane, while it also maintains high chemical stability against parasitic metal corrosion and hydrogen evolution reactions at surface, and a stable skeleton structure against the volume variation of anode. A Zn‐metal anode based on the telluride substrate shows a long cycle life of over 3300 h with a small voltage hysteresis of 48 and 320 mV at 1 and 30 mA cm−2, respectively. A zinc telluride@Zn//MnO2 full cell can operate for over 500 cycles under practical conditions in terms of lean electrolyte (18 µL mAh−1) and limited Zn metal ( negative/positive capacity ratio of 3:1, and a high mass loading of the cathode.