NiFe-MOF和氮氧自由基协同增强甾醇电催化氧化

传统甾醇中间体氧化采用重金属铬作为氧化剂,存在毒性大和环境污染等问题。电催化氧化(ECO)以其高效、环保、可控的优点备受青睐,被认为是一种可替代传统工艺的方法。然而,目前ECO面临低电流密度和低时空产率的挑战。本研究采用一步溶剂热法在石墨毡上制备自支撑NiFe-MOF纳米片电催化剂,并耦合NiFe-MOF与氮氧自由基(4-乙酰氨-2,2,6,6-四甲基哌啶-1-氧)协同电催化策略以提高ECO性能。研究发现碱性电解液可重构NiFe-MOF催化剂,从而提高催化活性。此外,连续流动强化传质,成功实现以100 mA·cm^(-2)的大电流密度对19-羟基-4-雄甾烯-3,17-二酮(1a)的选择性电催化氧化,且选择性高达98%,时空产率可达15.88 kg·m^(-3)·h^(-1),是间歇电反应器的35倍。寿命测试发现经10次循环反应后,NiFe-MOF/ACT协同体系对ECO仍具有较高的转化率。通过增大NiFe-MOF面积,将其组装至连续流动式电反应器并进行ECO恒电流电解,可达到12.99 kg·m^(-3)·h^(-1)的时空产率。该工作提出一种NiFe-MOF/ACT协同电催化氧化策略,为实现甾醇选择性氧化提供新的见解。

高活性方形氧化铅与可视化电解槽协同促进电催化臭氧生产

臭氧是一种环境友好型氧化剂,可直接用于消毒、杀菌和废水处理,对于维护和促进公共卫生安全至关重要.由于臭氧容易分解,不利于储存,因此需要现制即用.目前臭氧生成技术主要包括:电晕放电法和电催化臭氧生产(EOP)技术.相较于电晕放电法,EOP是一种本质安全的臭氧生产技术.然而,该工艺相较于电晕放电技术电能消耗量大,为了使其更具商业可行性,有必要开发高活性且低成本的电催化剂.此外,合理的电解槽设计对于实现高效EOP过程也至关重要.然而,目前研究主要集中在提高EOP催化剂活性方面,对电解槽的结构设计优化的关注较少.本文通过开发高效电催化剂进而将其应用于结构优化后的电解槽中,实现了更加高效的EOP过程.本文采用水热方法成功制备了一种具有较高EOP活性的方形氧化铅(PbO_(x)-CTAB-120)电催化剂.在标准三电极测试系统中,电流密度为50 mA cm^(-2)的测试条件下,法拉第效率(FE)可达20.7%,与商用β-PbO_(2)(17.1%)相比提高了21.1%.此外,设计了具有平行流场的可视化EOP电解槽,该可视化电解槽在传质和传热方面具有明显优势,有利于实现更加高效的EOP过程.将催化剂PbO_(x)-CTAB-120组装至可视化电解槽中,在1.0 A cm^(-2)的测试电流密度下,电解液为超纯水,该体系气态臭氧产量可以达到588 mg h^(-1)g^(-1)catalyst,比能量消耗(PEOP)为56 Wh g^(-1)gaseous ozone.体系臭氧产量约为商用β-PbO_(2)在传统电解槽中产量的2倍,并且PEOP降低率超过62%.原位18O同位素标记差分电化学质谱和密度泛函理论计算结果表明,PbO_(x)-CTAB-120电催化剂在EOP过程中遵循晶格氧机理路径,晶格氧迁移产生的氧空位能有效稳定OOH^(*)和O_(2)^(*)反应中间体,因此有利于催化剂在EOP过程中保持较好的反应活性和稳定性.同时,还利用先进的高速摄像可视化工具和计算流体力学(CFD)仿真模拟研究了平行流场EOP电解槽的运行过程和高效传质传热的原理.CFD模拟结果表明,与传统流场模型相比,平行流场对应的出口气泡停留时间更长,说明平行流场更有利于产物气泡从出口逸出,即气泡容易快速扩散,与实验结果一致.因此,PbO_(x)-CTAB-120电催化剂与新型可视化电解槽相结合,有助于在超纯水中实现较好的气态臭氧产率和较低比能耗.此外,二者的结合充分发挥了电催化剂的EOP活性和电解槽的传质特性所带来的优势,实现了反应性和传输性的协同增强,从而极大促进了原位有机污染物降解效率.综上所述,本文在制备高效阳极催化剂的基础上,同时利用优化电解槽结构实现了提升臭氧产率和降低过程能耗,为高活性电催化剂与优化的电解槽耦合以实现高效EOP过程及其有效应用提供参考.

Injectable Self‑Healing Adhesive pH‑Responsive Hydrogels Accelerate Gastric Hemostasis and Wound Healing

Endoscopic mucosal resection(EMR)and endoscopic submucosal dissection(ESD)are well-established therapeutics for gastrointestinal neoplasias,but complications after EMR/ESD,including bleeding and perforation,result in additional treatment morbidity and even threaten the lives of patients.Thus,designing biomaterials to treat gastric bleeding and wound healing after endoscopic treatment is highly desired and remains a challenge.Herein,a series of injectable pH-responsive selfhealing adhesive hydrogels based on acryloyl-6-aminocaproic acid(AA)and AA-g-N-hydroxysuccinimide(AA-NHS)were developed,and their great potential as endoscopic sprayable bioadhesive materials to efficiently stop hemorrhage and promote the wound healing process was further demonstrated in a swine gastric hemorrhage/wound model.The hydrogels showed a suitable gelation time,an autonomous and efficient self-healing capacity,hemostatic properties,and good biocompatibility.With the introduction of AA-NHS as a micro-cross-linker,the hydrogels exhibited enhanced adhesive strength.A swine gastric hemorrhage in vivo model demonstrated that the hydrogels showed good hemostatic performance by stopping acute arterial bleeding and preventing delayed bleeding.A gastric wound model indicated that the hydrogels showed excellent treatment effects with significantly enhanced wound healing with type I collagen deposition,α-SMA expression,and blood vessel formation.These injectable self-healing adhesive hydrogels exhibited great potential to treat gastric wounds after endoscopic treatment.

Multi-Label Chinese Comments Categorization: Comparison of Multi-Label Learning Algorithms

Multi-label text categorization refers to the problem of categorizing text througha multi-label learning algorithm. Text classification for Asian languages such as Chinese isdifferent from work for other languages such as English which use spaces to separate words.Before classifying text, it is necessary to perform a word segmentation operation to converta continuous language into a list of separate words and then convert it into a vector of acertain dimension. Generally, multi-label learning algorithms can be divided into twocategories, problem transformation methods and adapted algorithms. This work will usecustomer's comments about some hotels as a training data set, which contains labels for allaspects of the hotel evaluation, aiming to analyze and compare the performance of variousmulti-label learning algorithms on Chinese text classification. The experiment involves threebasic methods of problem transformation methods: Support Vector Machine, Random Forest,k-Nearest-Neighbor;and one adapted algorithm of Convolutional Neural Network. Theexperimental results show that the Support Vector Machine has better performance.

Wearable patches for transdermal drug delivery

Transdermal drug delivery systems(TDDs) avoid gastrointestinal degradation and hepatic first-pass metabolism, providing good drug bioavailability and patient compliance. One emerging type of TDDs is the wearable patch worn on the skin surface to deliver medication through the skin. They can generally be grouped into passive and active types, depending on the properties of materials,design principles and integrated devices. This review describes the latest advancement in the development of wearable patches, focusing on the integration of stimulus-responsive materials and electronics.This development is deemed to provide a dosage, temporal, and spatial control of therapeutics delivery.

Determination of Content of Hyperin and Luteolin in Vernonia cinerea (L.) Less.

[Objectives]To determine the content of hyperin and luteolin in Vernonia cinerea(L.)Less.,and to provide basic experimental data for experimental research and clinical application of V.cinerea(L.)Less.[Methods]The components to be determined were extracted by ultrasonic extraction,and the hyperin and luteolin in V.cinerea(L.)Less.were separated and determined by reversed-phase high performance liquid chromatography(chromatographic conditions:reverse C 18 column,methanol-0.4%phosphoric acid as mobile phase for gradient elution,flow rate of 1.0 mL/min,detector wavelength of 360 nm).[Results]The precision and repeatability of the experimental method were good,and the solution of V.cinerea(L.)Less.was stable within 18 h.There was a good linear relationship between the injection volume of hyperin and luteolin and the chromatographic peak area within the prescribed range,and the recovery rate was qualified.The content of hyperin and luteolin in V.cinerea(L.)Less.was 0.0665 mg/g(n=3)and 0.1004 mg/g(n=3),respectively.[Conclusions]The experimental method is sensitive,specific,stable,accurate and reliable,and can be used for the determination of hyperin and luteolin in V.cinerea(L.)Less.

Numerical Solutions of the Electromagnetic Scattering by Overfilled Cavities with Inhomogeneous Anisotropic Media

In this paper,the electromagnetic scattering from overfilled cavities with inhomogeneous anisotropic media is investigated.To solve the scattering problem,a Petrov-Galerkin finite element interfacemethod on non-body-fitted grids is presented.We reduce the infinite domain of scattering to a bounded domain problem by introducing a transparent boundary condition.The level set function is used to capture complex boundary and interface geometry that is not aligned with the mesh.Nonbody-fitted grids allow us to save computational costs during mesh generation and significantly reduce the amount of computer memory required.The solution is built by connecting two linear polynomials across the interfaces to satisfy the jump conditions.The proposed method can handle matrix coefficients produced by permittivity and permeability tensors of anisotropic media.The final linear system is sparse,making it more suitable for most iterative methods.Numerical experiments show that the proposed method has good convergence and realizability.Meanwhile,we discover that the absorbing properties of anisotropic media clearly and positively influence the reduction of radar cross section.It has also been demonstrated that the method can achieve second-order accuracy.

Miniaturization of mechanical actuators in skin-integrated electronics for haptic interfaces

Skin-integrated electronics,also known as electronic skin(e-skin);are rapidly developing and are gradually being adopted in biomedical fields as well as in our daily lives.E-skin capable of providing sensitive and high-resolution tactile sensations and haptic feedback to the human body would open a new e-skin paradigm for closed-loop human-machine interfaces.Here,we report a class of materials and mechanical designs for the miniaturization of mechanical actuators and strategies for their integration into thin,soft e-skin for haptic interfaces.The mechanical actuators exhibit small dimensions of 5 mm diameter and 1.45 mm thickness and work in an electromagnetically driven vibrotactile mode with resonance frequency overlapping the most sensitive frequency of human skin.Nine mini actuators can be integrated simultaneously in a small area of 2 cm×2 cm to form a 3×3 haptic feedback array,which is small and compact enough to mount on a thumb tip.Furthermore,the thin,soft haptic interface exhibits good mechanical properties that work properly during stretching,bending,and twisting and therefore can conformally fit onto various parts of the human body to afford programmable tactile enhancement and Braille recognition with an accuracy rate over 85%.

Review of accumulative failure of winding insulation subjected to repetitive impulse voltages

The premature failure phenomenon that occurs in solid insulation under the application of repetitive impulse voltages is known as the accumulative effect of impulse voltages on a solid dielectric.The accumulative failure of winding insulation is considered to be a core problem resulting from this phenomenon.The main problems include the accumulative failure of motor winding insulation under pulse-width modulation impulses and the accumulative failure of transformer winding insulation under the application of overvoltages,and these problems represent new challenges in the safe and stable operation of power grids.With regards to the above problems,this study reviews the results of recent research on the accumulative failure characteristics and mechanisms of winding insulation when subjected to repetitive impulse voltages.The challenges faced are discussed at the end of this study.