Ultrasensitive Pb2+ detection by glutathione-capped quantum dots

Water-soluble and stable quantum dots (QDs), CdTe and CdZnSe, are applied for ultrasensitive Pb(2+) detection. These QDs are capped with glutathione (GSH) shells. GSH and its polymeric form, phytochelatin, are employed by nature to detoxify heavy metal ions. As a result of specific interaction, the fluorescence intensity of GSH-capped QDs is selectively reduced in the presence of heavy metal ions such as Pb(2+). The detection limit of Pb(2+) is found to be 20 nM due to the superior fluorescence properties of QDs. Detailed studies by spectroscopy, microscopy, and dynamic light scattering show that competitive GSH binding of Pb(2+) with the QD core changed both the surface and photophysical properties of the QDs. Fluorescence of QDs is quenched, and QD aggregation occurs. Coupling the GSH-capped QDs with a high-throughput detection system, we have developed a simple scheme for quick and ultrasensitive Pb(2+) detection without the need for additional electronic devices. In the presence of ionic mixtures, our system is still capable of Pb(2+) detection with a detection limit as low as 40 nM. The system only becomes less sensitive when the ionic mixture is present at a very high concentration (i.e., > or =50 microM).     

Ringing phenomenon of the fiber ring resonator

A resonator fiber-optic gyro (R-FOG) is a high-accuracy inertial rotation sensor based on the Sagnac effect. A fiber ring resonator is the core sensing element in the R-FOG. When the frequency of the fiber ring resonator input laser is swept linearly with time, ringing of the output resonance curve is observed. The output field of the fiber ring resonator is derived from the superposition of the light transmitted through the directional coupler directly and the multiple light components circulated in the fiber ring resonator when the frequency of the laser is swept. The amplitude and phase of the output field are analyzed, and it is found that the difference in time for different light components in the fiber ring resonator to reach a point of destructive interference causes the ringing phenomenon. Finally the ringing phenomenon is observed in experiments, and the experimental results agree with the theoretical analysis well.     

A two-dimensional CVIB imaging system with a snake-based tracking algorithm

Quantitative ultrasound tissue characterization based on integrated backscatter (IB) has shown great potential in detecting myocardial ischemia. The magnitude of the cyclic variation in IB (CVIB) has recently been considered as one of the most promising parameters in assessing regional myocardial contractile performance. Our laboratory previously developed a novel ultrasonic fusion imaging method based on the CVIB. However, the major problem for clinical applications of this technique and other existing analytical methods based on IB is that the myocardial tissue can't be traced effectively without the cardiologist's intervention. In order to solve this problem, this paper presents a snake-based tracking algorithm to trace myocardial tissue automatically. A mathematical method is also introduced to extend the application of the snake model for detecting non-closed contours. The system developed in our previous research was redesigned to synchronize the radio frequency signal, the electrocardiographic signal, and the video signal, which allows verification of the system. Our results suggest that the system using the auto-tracking method increases the accuracy of detecting myocardial ischemia.     

EFFECT OF Na,K AND Ce ON CRACK PROPAGATION RESISTANCE FOR ALLOY 8090

The crack propagation resistance for alloy 8090 sheet decreases with the increase of content ofNa and K impurities.An improvement over the fracture toughness and crack initiation resist-ance for the alloy containing Na and K within certain limit may be made by adding 0.05%Ce.This beneficial modification would not be manifested if the alloy contained more Na andK.One of the reasons why Na and K injure the toughness of the alloy might be due to thatthey cause the precipitation of T_1 phase along grain and subgrain boundaries and acceleratethe abnormal growth of recystallized grains.     

MATHEMATICAL MODELLING OF FLOW PHENOMENA IN METAL BATH COVERED WITH MOLTEN SLAG

By use of the two-component LDA and high speed camera,the water model of the flow fieldin metal bath under molten slag layer has been tested.On the basis of experimental results,theflow boundary conditions of liquid metal at the slag-metal interface of a gas injecting bathwere deduced.The flow field and the turbulent parameters of the metal bath covered with slagwere solved by the vorticity-stream function method.The results reveal that the flow velocity,turbulent energy and circulating rate of the melt under slag are lower than that of withoutslagcover.Another one “dead zone” of the lowest turbulent energy is formed in the top layerunder cover of slag near the ladle linning.     

New method for multibody dynamics based on unknown constraint force

This paper presents a new method for the dynamics of multibody systems based on unknown constraint force. The method can uniformly solve multibody systems with typical configurations, including the system with rigid-flexible coupling, the system in tree topology, and the system with loop constraints. Unlike common methods, the proposed method can model the loop system without “cutting off” loop constraints, leading to the exact same modelling process as the tree-like system performs. Based on gr...     

骏枣精油的超临界CO2萃取工艺及其组成分析

以新疆骏枣为原料,采用超临界二氧化碳萃取技术对骏枣精油进行萃取分离,通过单因素和正交试验优化骏枣精油的萃取工艺,最后采用顶空-固相微萃取(headspace solid phase microextraction,HS-SPME)和气相色谱-质谱联用仪(gas chromatography-mass spectrometry,GC-MS)对骏枣精油成分进行分析。结果表明:超临界二氧化碳萃取骏枣精油最佳工艺为:乙醇作携带剂,萃取压力25 MPa,萃取温度32℃,夹带剂流速0.3 mL/min,萃取时间3 h,骏枣精油的萃取率可达1.224%。经GC-MS分析,共检出68种物质,结构推断59种,占总峰面积的91.737%,其中主要包括酸类、烷烃类、酮类、酯类以及少量的醛类、醇类等。各类物质中焦糖香味的麦芽醇和5-羟甲基糠醛,杏仁气味苯甲酸和糠醛以及奶香味的3-羟基-2-丁酮都可能是骏枣精油的主要香气成分。     

A Review on Engineering Design for Enhancing Interfacial Contact in Solid-State Lithium–Sulfur Batteries

The utilization of solid-state electrolytes(SSEs) presents a promising solution to the issues of safety concern and shuttle effect in Li–S batteries, which has garnered significant interest recently. However, the high interfacial impedances existing between the SSEs and the electrodes(both lithium anodes and sulfur cathodes) hinder the charge transfer and intensify the uneven deposition of lithium, which ultimately result in insufficient capacity utilization and poor cycling stability. Hence,the...     

Understanding ultra-dispersed CeOx modified iridium clusters as bifunction electrocatalyst for high-efficiency water splitting in acid electrolytes

Designing bifunctional catalysts with high catalytic activity and durability for electrochemical water splitting has become a promising approach to producing clean and sustainable hydrogen fuels.With high specific surface area and ultra-small size,metal clusters have become a kind of promising catalysts.By introducing Ce species,the noble metal iridium(Ir) can be electronically modulated,thus reduce the activation energy of intermediate,and improve the intrinsic catalytic activity for practical ...     

Photocatalytic degradation of tetracycline hydrochloride with visible light-responsive bismuth tungstate/conjugated microporous polymer

Conjugated microporous polymer (CMP) is an emerging organic semiconductor with π-conjugated skele-tons,and the bandgap of CMP can be flexibly modulated to harvest visible light.Based on the diversity and adjustability of monomers in CMP,we designed and synthesized donor-accepter (D-A) type BTN-CMP through Sonogashira-Hagihara cross-coupling polymerization,further in-situ constructing series of inorganic/organic Z-scheme BW/BTN-n composite in the presence of Bi2WO6.After optimization,the tetracycline hydrochloride (Co =10 mg·L-1) degradation efficiency reached 84％ with BW/BTN-2 as cata-lyst in 90 min under visible light irradiation,the apparent rate constant k1 is 0.017 min-1,which is 1.7 and 5.7 times higher than bare Bi2WO6 and BTN-CMP.X-ray photoelectron spectra and UV-Vis diffuse spectra showed that the enhanced photocatalytic activity originated from the tight heterojunction between Bi2WO6 and BTN-CMP,which can extend the light absorption range and facilitate the separation and transport of photogenerated charges in the interface of heterojunction.The active species trapping experiments and electron spin resonance technique revealed that h+ was the dominant active species during the photodegradation process of tetracycline hydrochloride (TCH).The present study demon-strated the feasibility to construct inorganic/organic composite for the photocatalytic degradation of environmental pollutants.