High Mobility 3D Dirac Semimetal (Cd3As2) for Ultrafast Photoactive Terahertz Photonics

The Dirac semimetal cadmium arsenide (Cd₃As₂), a 3D electronic analog of graphene, has sparked renewed research interests for its novel topological phases and excellent optoelectronic properties. The gapless nature of its 3D electronic band facilitates strong optical nonlinearity and supports Dirac plasmons that are of particular interest to realize high-performance electronic and photonic devices at terahertz (1 THz = 4.1 meV) frequencies, where the performance of most dynamic materials are limited by the tradeoff between power-efficiency and switching speed. Here, all-optical, low-power, ultrafast broadband modulation of terahertz waves using an ultrathin film (100 nm, λ/3000) of Cd₃As₂ are experimentally demonstrated through active tailoring of the photoconductivity. The measurements reveal the photosensitive metallic behavior of Cd₃As₂ with high terahertz electron mobility of 7200 cm² (Vs)⁻¹. In addition, optical fluence dependent ultrafast charge carrier relaxation (15.5 ps), terahertz mobility, and long momentum scattering time (157 fs) comparable to superconductors that invoke kinetic inductance at terahertz frequencies are demonstrated. These remarkable properties of 3D Dirac topological semimetal envision a new class of power-efficient, high speed, compact, tunable electronic, and photonic devices.     

Effect of concentration of cadmium sulfate solution on structural,optical and electric properties of Cd1-xZnxS thin films

Cd1-xZnxS thin films were deposited by chemical bath deposition(CBD)on the glass substrate to study the influence of cadmium sulfate concentration on the structural characteristics of the thin film.The SEM results show that the thin film sur-faces under the cadmium sulfate concentration of 0.005 M exhibit better compactness and uniformity.The distribution dia-grams of thin film elements illustrate the film growth rate changes on the trend of the increase,decrease,and increase with the increase of cadmium sulfate concentration.XRD studies exhibit the crystal structure of the film is the hexagonal phase,and there are obvious diffraction peaks and better crystallinity when the concentration is 0.005 M.Spectrophotometer test results demonstrate that the relationship between zinc content x and optical band gap value Eg can be expressed by the equation Eg(x)=0.59x2+0.69x+2.43.Increasing the zinc content can increase the optical band gap,and the absorbance of the thin film can be improved by decreasing the cadmium sulfate concentration,however,all of them have good transmittance.At a concen-tration of 0.005 M,the thin film has good absorbance in the 300-800 nm range,80％transmittance,and band gap value of 3.24 eV,which is suitable for use as a buffer layer for solar cells.     

移动式加载系统中运送动载对支撑架的影响

在对桥梁支撑架进行加载预压时,采用新型可移动式加载系统可以弥补传统加载预压试验中存在的缺陷,但设计时需考虑可移动式加载系统中运输小车的运送荷载作用.通过建立可移动式加载系统的三维分析模型,采用数值模拟的方法分析加载过程中运送动载对桥梁支撑架的影响规律,并分析了不同运送速度条件下运送荷载对桥梁支撑架的动力响应规律.结果表明:随着加载的进行,小车动荷载所占总荷载的比重降低,支撑架杆件动静力响应峰值之间的相对差值逐步降低;随着小车运行速度增大动力响应峰值呈非线性增长,小车运行速度越大动力响应峰值增长越快.     

Synthesis and coloring properties of Cd（S1-xSex） pigments by precipitate-hydrothermal method

Cd（S1-xSex） pigments （red to yellow） were synthesized by precipitate-hydrothermal method. The structure, morphology and hue of the powder were characterized by X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, energy dispersive X-ray spectroscopy （EDAX） and CIE chromaticity. The optimum synthesis conditions were obtained and reaction mechanism was further analyzed as well. The results show that molar ratio of S to Se, pH value and hydrothermal reaction conditions have great effects on the hues of the pigments. Pigments with vivid hues are obtained under the conditions that pH value is about 13.0, hydrothermal reaction condition is at 140 ℃ for 4 h or at 160 ℃ for 6 h. The reaction mechanism is that Se^2- of Cd（S1-xSex） substitutes S^2- of CdS and then forms a continuous solid solution.     

Heavy metals in maternal and cord blood

Heavy metal concentrations have been determined in maternal and cord blood samples collected from mothers in the age group 20-25 years with full-term neonates (37-40 weeks). The concentrations of Pb, Cd, Cu and Zn were found to be low in cord blood as compared to mother's blood and the ratio between cord blood and maternal blood for the respective elements was found to be approximately 0.80, 0.86, 0.47 and 0.40. On the other hand, the concentrations of Fe and Mg in the mother's blood were found to be lower than those in the cord blood. Prenatal exposure to lead in Mumbai, though low (5.1 microg/dl), is approximately 2-3 times higher than that observed in Canada or Italy. A strong correlation (r = 0.79) between the maternal and cord blood lead levels has been observed during the present study.     

Growth responses of three ornamental plants to Cd and Cd-Pb stress and their metal accumulation characteristics

Up to now, there was no document on ornamental plants that had been applied to phytoremediation, which can remedy contaminated environment and beautify it at the same time. Thus, the growth responses and possible phytoremediation ability of three ornamental plants selected from the previous preliminary experiments were further examined under single Cd or combined Cd-Pb stress. The results showed that these tested plants had higher tolerance to Cd and Pb contamination and could effectively accumulate the metals, especially for Calendula officinalis and Althaea rosea. For C. officinalis, it grew normally in soils containing 100 mg kg(-1) Cd without suffering phytotoxicity, and the Cd concentration in the roots was up to 1084 mg kg(-1) while the Cd concentration in the shoots was 284 mg kg(-1). For A. rosea, the Cd accumulation in the shoots was higher than that in the roots when the Cd concentration in soils was <100 mg kg(-1), and reached 100 mg kg(-1) as the criteria of a Cd hyperaccumulator when the Cd concentration in soils was 100 mg kg(-1). Their accumulation and tolerance to Cd and Pb were further demonstrated through the hydroponic-culture method. And A. rosea had a great potential as a possible Cd hyperaccumulator under favorable or induced conditions. Furthermore, the interactive effects of Cd and Pb in the three ornamentals were complicated, not only additive, antagonistic or synergistic, but also related to many factors including concentration combinations of heavy metals, plant species and various parts of plants. Thus, it can be forecasted that this work will provide a new way for phytoremediation of contaminated soils.     

Recovery of surfactant SDS and Cd2+ from permeate in MEUF using a continuous foam fractionator

The purpose of this study was to investigate the use of foam fractionation to recover valuable surfactant (SDS) and metal ion (Cd²⁺) in the permeate of micellar-enhanced ultrafiltration (MEUF). The effects of operating factors, such as time, air flow rate, feed flow rate, liquid height, foam height, feed surfactant concentration, ethanol concentration and temperature on separation characteristics were studied in the continuous operation. When the concentrations of surfactant (SDS) and metal ion (Cd²⁺) in the feed solution were 500 mg/L and 10 mg/L, an enrichment ratio of 3.1 was achieved for SDS along with 52% removal fraction, as well as 99.35% Cd²⁺ was removed, after optimization of different process parameters. As the optimized results, the air and liquid flow rates were 100 L/h and 5 L/h, liquid and foam heights were 45 cm and 66 cm, respectively, sparger pore size was 10 μm. The Cd²⁺ concentration in the effluent was lower than 0.1 mg/L which could meet the integrated wastewater discharge standard (the first grade of national discharge standards in China).     

精锑中铜、铅、镉、锌、硒五元素的极谱快速连续测定研究

本文除提出了在１０％ＨＣｌＯ４－２．６％Ｈ３ＰＯ４－０．４％ＨＣＯＯＨ中测定微量铜、铅、镉、锌的新体系外,并巧妙地将作者原测硒体系结合起来,快速简便地完成题示之测定。方法己用于大批生产,效果良好。还对电极过程作了论述。     

镍粉性能对镉镍电池性能的影响

镍粉是影响电池性能的主要因素之一。研究了Ｔ２１０ 镍粉、Ｔ２５５ 镍粉及电解超细镍粉对镍电极、镉电极性能的影响,以及分别用此３ 种镍粉处理镉电极后对电池性能的影响。参考各镍粉的其它特点,提出了合理使用范围及方法。     

工业用大容量镉镍蓄电池仍将持续发展

介绍了工业用大容量镉镍碱性蓄电池的特点以及在航空、电力、铁路交通、通讯等领域的应用情况,并与铅酸,金属氢化物镍电池和锂离子电池进行了简单比较,表明镉镍碱性蓄电池在高功率应用领域,尤其在低温条件下具有不可替代性。随着现代化进一步发展,镉镍碱性蓄电池仍将持续发展。由于镉镍电池存在镉污染,因此,无论生产过程还是用后回收,都应有严格的管理措施,确保最大限度地控制对环境污染,充分发挥该系列电池的有益作用。