A Review of In‑Situ Techniques for Probing Active Sites and Mechanisms of Electrocatalytic Oxygen Reduction Reactions

Electrocatalytic oxygen reduction reaction(ORR)is one of the most important reactions in electrochemical energy technologies such as fuel cells and metal–O2/air batteries,etc.However,the essential catalysts to overcome its slow reaction kinetic always undergo a complex dynamic evolution in the actual catalytic process,and the concomitant intermediates and catalytic products also occur continuous conversion and reconstruction.This makes them difficult to be accurately captured,making the identification of ORR active sites and the elucidation of ORR mechanisms difficult.Thus,it is necessary to use extensive in-situ characterization techniques to proceed the real-time monitoring of the catalyst structure and the evolution state of intermediates and products during ORR.This work reviews the major advances in the use of various in-situ techniques to characterize the catalytic processes of various catalysts.Specifically,the catalyst structure evolutions revealed directly by in-situ techniques are systematically summarized,such as phase,valence,electronic transfer,coordination,and spin states varies.In-situ revelation of intermediate adsorption/desorption behavior,and the real-time monitoring of the product nucleation,growth,and reconstruction evolution are equally emphasized in the discussion.Other interference factors,as well as in-situ signal assignment with the aid of theoretical calculations,are also covered.Finally,some major challenges and prospects of in-situ techniques for future catalysts research in the ORR process are proposed.

In-situ/operando techniques to identify active sites for thermochemical conversion of CO_(2) over heterogeneous catalysts

The catalytic conversion of CO_(2) to fuels or chemicals is considered to be an effective pathway to mitigate the greenhouse effect. To develop new types of efficient and durable catalysts, it is critical to identify the catalytic active sites, surface intermediates, and reaction mechanisms to reveal the relationship between the active sites and catalytic performance. However, the structure of a heterogeneous catalyst usually dynamically changes during reaction, bringing a great challenge for the identification of catalytic active sites and reaction pathways. Therefore, in-situ/operando techniques have been employed to real-time monitor the dynamic evolution of the structure of active sites under actual reaction conditions to precisely build the structure–function relationship. Here, we review the recent progress in the application of various in-situ/operando techniques in identifying active sites for catalytic conversion of CO_(2) over heterogeneous catalysts. We systematically summarize the applications of various optical and X-ray spectroscopy techniques, including Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS), in identifying active sites and determining reaction mechanisms of the CO_(2) thermochemical conversion with hydrogen and light alkanes over heterogeneous catalysts. Finally, we discuss challenges and opportunities for the development of in-situ characterization in the future to further enlarge the capability of these powerful techniques.

Technique and experiment of active direct gas pressure measurement in coal roadway

An active measurement method and its principle was introduced consideringthe low success rate,special difficulty,and long measurement time of the direct gas pressuremeasurement currently used in coal roadways.The technology of drilling,boreholesealing depth,borehole sealing length,sealing control of the measuring process,compensatorycomputation of gas loss quantity and other key techniques were discussed.Finally,based on the latest instrument the authors developed,a series of experiments of directgas pressure measurement in the coal roadways of the Jincheng and Tongchuanmine district,were carried out.The experimental results show that active gas pressuremeasurement technique has advantages as follows:(1) the application scope of direct gaspressure measurement technique is wide and it does not have the restriction of coalhardness,coal seam fissure and other conditions;(2) the measured results are credible,which can be tested by the same gas pressure value acquired from a different borehole inthe same place;(3) the measurement process is convenient and quick,it takes about 2 to3 days to acquire the gas pressure value in a coal seam.

Techniques of Activating Textbooks for Intensive Reading

This paper presents four teaching techniques of activating the textbook for intensive reading which include:injecting contemporary elements into the text,relating the text to students' life,questioning about the text challengingly and ingeniously,and spicing up the text.

Activation characteristics analysis on concealed fault in the excavating coal roadway based on microseismic monitoring technique

In order to effectively monitor the concealed fault activation process in excavation activities, based on the actual condition of a working face containing faults with high outburst danger in Xin Zhuangzi mine in Huainan, China, we carried out all-side tracking and monitoring on the fault activation process and development trend in excavation activities by establishing a microseismic monitoring system. The results show that excavation activities have a rather great influence on the fault activation. With the working face approaching the fault, the fault activation builds up and the outburst danger increases; when the excavation activities finishes, the fault activation tends to be stable. The number of microseismic events are corresponding to the intensity of fault activation, and the distribution rules of microseismic events can effectively determine the fault occurrence in the mine. Microseismic monitoring technique is accurate in terms of detecting geologic tectonic activities, such as fault activations lying ahead during excavation activities. By utilizing this technique, we can determine outburst danger in excavation activities in time and accordingly take effective countermeasures to prevent and reduce the occurrence of outburst accidents.

Accumulation of heavy metals in two crop seeds due to soil contamination as determined by neutron activation analysis techniques

Samples of two crop seeds (corn and sesame) grown on different contaminated soil sources were collected and prepared for neutron activation analysis. Soil contamination sources were organic waste compost applied to soil amendments namely, sewage sludge(Bs) and municipal solid waste (MSW) at 4%, 6% and 8% respectively. The non destructive NAA technique was used to determine some trace elements accumulation in plant seeds. Results revealed that increasing rate of tested organic waste resulted in dramatic increase in tested heavy metals levels in seeds(i.e., Fe, Zn, Co, Cr, Sc and Hg). Sesame seeds showed higher affinity to accumulate trace elements than corn grains in most tested elements. Moreover, MSW addition enhanced the accumulation of tested metals in seeds more than Bs compost.

Photocatalytic Activity of TiO_(2) Coatings Fabricated on Al_(2)O_(3) by Mechanical Coating Technique

The titanium coatings were prepared on Al_(2)O_(3) balls by mechanical coating technique (MCT),and then the coatings were oxidized to titanium oxides(TiO_(2)) films at 300-600 ℃.The effects of different milling time and oxidation temperature on thickness of films were studied.The composition and microstructure of the films were analyzed by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS).The results show that the thickest coatings with an average thickness of 20 μm were obtained at the milling time of 15 h.In addition,with the increase of the oxidation temperature,the oxidation of the film is increased.When the milling time is 15 h,the oxidation temperature is 500 ℃,and the addition of photocatalyst is 1 g/mL.The films have the best photocatalytic performance when the degradation rate of methyl orange solution reaches the maximum value of 74.9 %,and the films have a good reusability.

Fluorescent Voltage Imaging Technique for the Measurement of Molluscan Neural Activities

The electrophysiological methods using microelectrodes are not appropriate for the simultaneous measurement of neural activities of many neurons. To overcome the difficulty, the fluorescent imaging technique using voltage sensitive dyes can be a powerful technique. The voltage sensitive dyes, however, generally exhibit a relatively small change in their fluorescence intensities, resulting in a low S/N ratio. Additionally, they often exhibit photobleaching and phototoxity. We have therefore improved the fluorescent voltage imaging technique by using a LED as the light source and an electron multiplying (EM)-CCD camera as the fluorescence detector. In this study, we applied our imaging system for the measurement of two kind of molluscan neural activities;one of which is involved in the olfactory processing of the land slug Limax valentianus and the other is involved in the feeding rhythm of the pond snail Lymnaea stagnalis. The system enabled us to measure the neural activities for a long time with a high speed and a high S/N ratio, and the obtained results showed some new physiological findings.

An effective technique for isolating adult activated Schwann cells

BACKGROUND： Schwann cells （SCs） are neuroglial cells of peripheral nerve and play a key role in repairing peripheral nerve injury; therefore, it provides an important evidence for transplantation of SCs which are characterized by active proliferation and adult high-purity in vitro after nerve injury in clinic, and also develops a new therapeutic way for nerve injury.OBJECTEVE： To investigate an effective technique for isolating adult activated Schwann cells,DESIGN： Controlled observational study.SETTING： Mudanjiang Medical College.MATERIALS： The experiment was completed at the Department of Medical Genetics of Harbin Medical University from March 2003 to April 2005. Health female Wistar rats, aged 2 months, weighting 150-160 g, were randomly divided into 3 groups with 5 in each group.METHODS： The right sciatic nerves from 15 Wistar rats were exposed and transected at the mid thigh under pentobarbital anesthesia （4 mg/kg, Lp）. Seven days later, the distal segments of the predegenerated nerves were removed and used to produce adult Schwann cell cultures. The distal segment of the predegenerated nerve, 20 mm in length, was resected. The nerve was cut into pieces 1 mm in length and incubated for 3 hours under CO2 at 37 ℃ with an enzyme mixture of 0.05% collagenase/dispase. Rats were divided into 3 groups： ① Group 1： The nerve fragments were explanted in poly-L-lysine and laminin-coated dishes with BS medium from the 1st to the 6th day, On the 6^th day, the fragments were removed into a new poly-L-lysine-laminin-coated dish and the BS medium was changed to BS with 10% FBS, The nerve fragments were replaced repeatedly in the same way in new dishes on the 12^th and the 18th days. ② Group 2： For the first 3 days, the nerve fragments were fed with BS with 10% FBS. This medium was changed to BS medium on the third day. The nerve fragments were removed to another dish on day 6 and BS medium was changed to BS with 25 mI.JL FBS. Hereafter the culture method was the same as for group 1. ③ Group 3： For the first 6 days, nerve fragments were incubated in a dish not coated with poly-L-lysine and laminin, in BS medium supplemented with 8×10^7 U/L of penicillin-streptomycin. On the 6th day, the nerve fragments were removed to a poly-L-lysine-laminin-coated dish and cultured in BS with 25 mI.JL FBS, On the 12th day, the nerve fragments were explanted a second dish and fed with BS containing 100 mL/L FBS. On the 18^th day, they were explanted to a third poly-L-lysine-laminin-coated dish, SCs were obtained from all 3 dishes on the 21st day, Finally, purity and density of SCs were identified and proliferation index was calculated at the same time.MAIN OUTCOME MEASURES ： Purity and density of SCs cultured with various methods in the three groups for 21 days.RESULTS ： ① Isolation and proliferation of SCs： In the group 1, they increased in number after 4 days and both purity and density of cultured SCs were significantly higher than those from group 2. In the group 2, there were few fibroblasts. In the group 3, both purity and density of cultured SCs were remarkably higher than in those from groups 1 or 2. Then optimal proliferation was soon seen and the rapid expansion of SC populations suppressed the development of contaminating fibroblasts. On the 21st day, SCs proliferated to achieve maximal density and were too crowded to be counted. With Chi-square test, the data of the purity and the density were analyzed from groups 1 to 3, the result indicated X^2=430.47, P 〈 0.05. ② Characterization and proliferation rate of SCs： Immunostaining for S100 protein was evident in the cell soma and the processes of all three groups in cultures of SCs. SCs in vitro demonstrated typical bior tri-polar morphology, had oval nuclei, and stained brightly for $100. The proliferation rate of SCs was assessed with double fluorescence staining for BrdU and S100 on the 21^st day of all three groups in cultures. About 40%-50% of the total SCs in the each group showed BrdU incorporation.CONCLUSION： The method is to use predegeneration in vivo, differential speed culture supplemented with the penicillin-streptomycin in low concentration, and changing of the concentration of FBS in the BS medium from 0 to 100 mL/L. This method allows remarkable suppression of fibroblast growth and attainment of SC proliferation and purity, in a short time, from adult nerves.

The Potential of Activated Carbon in the Treatment of Water for Human Consumption, a Study of the State of the Art and Its Techniques Used for Its Development

This review article addresses the use of biological activated carbon in water treatment and its techniques for its development, with the premise of analyzing the potential of Activated Carbon (AC) in the treatment of water for human consumption. For this end, it aims to identify the techniques used for the production of AC, use and its benefits, production from vegetable waste for water treatment. Activated carbon has the ability to selectively collect gases, liquids and impurities inside its pores, which is the reason it is widely used in filtration systems and for that the treatment of water, the coal fulfills the function of adsorbent, retaining in its pores certain types of impurities: large particles that cause undesirable color, taste or odor in the water. In the treatment of effluents, coal is used for clarification, deodorization and purification of effluents.

Creation of reversed phase high-performance liquid chromatographic technique to assay platelet-activating factor

Objective: To establish a new assay for platelet-activating factor (PAF), to compare it with bio-assay; and to discuss its significance in some elderly people diseases such as cerebral infarction and coronary heart disease. Methods: To measure PAF levels in 100 controls, 23 elderly patients with cerebral infarction and 65 cases with coronary heart disease by reversed phase high-performance liquid chromatographic technique (rHPLC). Results:rHPLC is more convenient, sensitive,specific, and less confusing, compared with bio-assay. The level of plasma PAF in patients with cerebral infarction was higher than that in the controls (P<0.01), and in patients with coronary heart disease. Conclusion: Detection of PAF with rHPLC is more reliable and more accurate. The new assay has important significance in PAF research.

Microstructure and properties of the joints of ZrO2 ceramic/ stainless steel brazed in vacuum with AgCuTi active filler metal

The ZrO2 ceranfic was successfully jointed to stainless steel by vacuum brazing with active filler metal. The AgCuTi active filler metal was used and the joining was performed at a temperature of 850 ℃ for 10 rain. The microstructures of the joints were characterized by metallographic microscopy, scanning electron microscopy （SEM）, and energy dispersive spectroscopy （EDS）. Metallographic microscopy analysis shows that the morphology of the cross section was a sandwich structure and the TiO is observed in the surface of ZrO2/ stainless steel. The diffusion and enrichment of the elements are the key roles in the brazing of ZrO2 ceramic and stainless steel. The formation of TiCu compounds inhibited the further diffusion of titanium into stainless steel or the ZrO2 ceramic to form TiO compound. In the experimental conditions, the average tensile strength is 80MPa for the joint of ZrO2 ceramic / AgCuTi/ stainless steel systems. A complete joint is formed between the ZrO2 ceramic and stainless steel with the leakage rate at the degree of 10 ^-12 Pa · m^3/s.

Efficiencies of Chemical Techniques for Rice Grain Freshness Analysis

Two chemical methods which are commonly used for rice grain freshness determination were investigated for their efficiencies. Method 1 is made of bromothymol blue indicator, and the principle is based on indicator＇s color which is changed in according to pH of the stored rice grains. Method 2 is based on peroxidase activity which deteriorates during storage of rice grains. Both methods were used for determination of fresh-aged rice index of six Thai-rice cultivars, four from non-waxy rice cultivars （KDML 105, Chai Nat 1, Chai Nat 2 and Phitsanulok 2） and two from waxy rice cultivars （San-pah-tawng and RD6）. Rice samples were kept in the forms of paddy and polished rice. Fresh-aged rice indices were determined using both methods every two weeks over the storage period of 24 weeks （six months）. It was found that both methods were capable of detecting fresh-aged rice indices. The color of chemical solutions changed with regards to the age of rice grains and it could be detected spectrophotometrically. Rice grains which have been kept as paddy provided more consistent results. Method 1 is recommended for industrial application as it is simple, efficient and inexpensive.

Control of Vehicle Active Front Steering Based on Active Disturbance Rejection Feedback Controller

A control method of active front steering(AFS)based on active disturbance rejection technique was proposed for solving the model nonlinearity and parameter decoupling control in the traditional control methods.The AFS controller consists of the proportional and derivative(PD)feed-forward controller and the active disturbance rejection feedback controller.To improve the steering response characteristics of a vehicle,a PD controller is designed to realize variable steering gear ratio,and to enhance the safety of vehicle when steering.An active disturbance rejection controller(ADRC)is designed to follow the expected yaw rate of the vehicle.According to the input and output of system,extended state observer(ESO)of ADRC can dynamically estimate internal and external disturbance of the system,thus easily realizing the model nonlinear and parameter decoupling control.The AFS controller is simulated and validated in Matlab and CarSim.The simulating results of double lane change(DLC)test and pylon course slalom(PCS)test show that the ADRC can well control the vehicle model to complete the road simulation test of DLC and PCS with small path tracking error.The simulating results of angle step test of steering wheel show that the vehicle under the control of ADRC demonstrates good lateral response characteristic.The controller regulates a wide range of parameters.The model has less precision requirements with good robustness.

Active Optics in LAMOST

Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is one of the major national projects under construction in China. Active optics is one of the most important technologies for new large telescopes. It is used for correcting telescope errors generated by gravitational and thermal changes. Here, however, we use this technology to realize the configuration of LAMOST,—a task that cannot be done in the traditional way. A comprehensive and intensive research on the active optics used in LAMOST is also reported, including an open-loop control method and an auxiliary closed-loop control method. Another important development is in our pre-calibration method of open-loop control, which is with some new features: simultaneous calculation of the forces and displacements of force actuators and displacement actuators; the profile of mirror can be arbitrary; the mirror surface shape is not expressed by a fitting polynomial, but is derived from the mirror surface shape formula which is highly accurate; a proof is given that the solution of the pre-calibration method is the same as the least squares solution.

Active X控件在DelPhi5中的开发应用

本文简要介绍了Ａｃｔｉｖｅ Ｘ技术、Ａｃｔｉｖｅ Ｘ控件，结合实例介绍了 Ａｃｔｉｖｅ Ｘ控件在Ｄｅｌｐｈｉ５中实现动态ＷＥＢ数据库数据查询的开发，并给出主要的程序代码．

The Effective Techniques of Dictation-based Vocabulary Teaching in English Classes

Dictation is a traditional but still widely applied method to teach language vocabulary,grammar structures and other language skills.Because of the teachers’negative opinions on dictation and improper ways of dictation conduction,dictation hasn’t received a satisfying expectation in English vocabulary teaching in China.This research attempts to find out some innovative dictation activities and some effective techniques which can help English teachers in China conduct dictation in these activities to promote the efficiency of language vocabulary teaching.