High-performance,transparent conducting oxides based on cadmium stannate

We discuss the modeling of thin films of transparent conducting oxides and we compare the predictions with the observed properties of cadmium stannate. Thin films of this material were deposited using radio-frequency magnetron sputtering. The Drude free-carrier model is used to model the optical and electrical properties. The model demonstrates the need for high mobilities. The free-carrier absorbance in the visible spectrum is used as a comparative figure-of-merit for cadmium stannate and tin oxide. This shows that free-carrier absorbance is much less in cadmium stannate than in tin oxide. X-ray diffraction shows that annealed films consist of a single-phase spinel structure. The post-deposition annealing sequence is shown to be crucial to forming a single phase, which is vital for optimal optical and electrical properties. The films are typically high mobility (up to 65 cm² V^?1 s^?1) and have carrier concentrations as high as 10²¹ cm^?3. Resistivities are as low as 1.3 10^?4 Ω. cm, the lowest values reported for cadmium stannate. Atomic force microscopy indicates that the root-mean-square surface roughness is approximately ±15Å. Cadmium stannate etches readily in both hydrofluoric and hydrochloric acid, which is a commanding advantage over tin oxide.     

MCT液相外延薄膜的生长和特性

用开管水平液相外延系统从富Te溶剂中生长了不同x值的MCT薄膜。经X射线衍射、Hall电学参数、红外光谱、扫描电镜、X射线能谱仪和电子通道花样分析测试,结果表明:外延薄膜表面平整,光学参数较好,纵向、横向组份均匀,晶体结构完整,电学参数较好,外延膜质量优良。短波材料(n型):载流子浓度3.54×10~(14)cm~(-3),迁移率1.63×10~4cm~2V~(-1)s~(-1);中波材料(n型):载流子浓度9.95×10~(14)cm~(-3),迁移率为1.76×10~4cm~2V~(-1)s~(-1);原生长波材料(n型):载流子浓度为2.15×10~(15)cm~(-3),迁移率2.00×10~4cm~2V~(-1)s~(-1)。     

Transformation of calcium cyanamide and its inhibitory effect on urea nitrification in some tropical soils

Transformation of calcium cyanamide and its inhibitory effect on urea nitrification was studied in some tropical soils. Three soils, from Onne, Mokwa and Samaru, representing different agro-climatological zones of Nigeria were incubated with calcium cyanamide, urea or a mixture of both for eight weeks at 30 °C and at field capacity moisture content. The recovery of inorganic N (NH ₄ ⁺ plus NO ₂ ^- plus NO ₃ ^- )from calcium cyanamide varied from 64% to 87% in different soils. Most of the inorganic N accumulated was in NH ₄ ⁺ form. Nitrification of the accumulated NH ₄ ⁺ in all the soils was slow.Urea (75 mg N kg^–1 soil) was completely nitrified within a week in the Samaru and Mokwa soils whereas in the Onne soil the rate of nitrification was slow. Addition of CaCN₂ at the rate of 10 mg N kg^–1 soil generally delayed ammonification of urea and nitrification was severely inhibited in all the soils. Addition of CaCN₂ at the rate of 20 mg N kg^–1 soil further reduced the ammonification of urea and completely inhibited the nitrification. High recovery of inorganic N from calcium cyanamide and its effective reduction of nitrification of urea make it suitable source of N for plants in the tropics, provided it is managed to avoid phyto-toxicity.     

On the degradation process in electrophotographic cadmium sulphide binder layers

The two stages of degradation in electrophotographic cadmium sulphide binder layers-fatigue and ageing are investigated. The dependences of the photoinduced decay of the potential and the contrast potential vs the exposure time during the first cycle and in fatigue show that this process probably occurs in the bulk of the semiconductor particles. The changes of the photoinduced decay of the potential during the second stage of degradation, ageing, may be associated with changes in the barrier structure.     

Successively pulse plated cadmium selenide films and their photoelectrochemical behaviour

In successive pulse plating, the pulse deposition is repeated after a definite duration of plating preceded by a mild cleaning of the electrode and with a fresh deposition bath for the same duration. In this study, CdSe films were deposited on Ti substrates by successive pulse plating from a bath containing CdSO₄ and SeO₂ at a current density of 80 mA cm⁻² and a duty cycle of 3·3% for a duration of 30 min. The films heat-treated to 550°C for 20 min in argon atmosphere, were polycrystalline with a hexagonal structure. At an illumination of 60 mW cm⁻², a conversion efficiency of 4·5% for the photoetched film and 1·7% for the chemically etched one were determined.     

Polymetallic complexes. part iii. schiff base complexes of cobalt(ii), copper(ii), cadmium(ii) and mercury(ii)

Eight polymetallic complexes have been synthesised of the composition M₂L₂._nB [M = Co(II), n = 4, B=H₂O, M = Cu(II), Cd(II) and Hg(II), n = 0] M₂L_2'.nB [M = Co(II), n = 4, B = H₂O; M = Cu(II), Cd(II) and Hg(II), n = 0], LH₂ = bi-bidentate Schiff base derived from benzoin with m-phenylenediamine; L'Hz = tridentate Schiff base derived from benzoin with o-aminophenol. Elemental analysis, conductance, magnetic susceptibility, i.r. and electronic spectral measurements have been done to characterise the complex compounds. A dinuclear octahedral configuration has been assigned to the cobalt(II) complexes and a dinuclear square planar structure to the copper(II) complexes. A tetrahedral configuration has been attributed to the cadmiurn(II) and mercury(II) complexes.     

Changes in mercury and cadmium concentrations and the feeding behaviour of beluga (Delphinapterus leucas) near Somerset Island, Canada, during the 20th century

Beluga (Delphinapterus leucas) continues to be an important food species for Arctic communities, despite concerns about its high mercury (Hg) content. We investigated whether Hg and cadmium (Cd) concentrations had changed during the 20th century in beluga near Somerset Island in the central Canadian Arctic, using well-preserved teeth collected from historical sites (dating to the late 19th century and 1926-1947) and during subsistence hunts in the late 1990s. Mercury concentrations in both historical and modern teeth were correlated with animal age, but 1990s beluga exhibited a significantly more rapid accumulation with age than late 19th century animals, indicating that Hg concentrations or bioavailability in their food chain had increased during the last century. The geometric mean tooth Hg concentration in modern 30 year old animals was 7.7 times higher than in the late 19th century, which corresponds to threefold higher concentrations in muktuk and muscle. Teeth from 1926 to 1947 were similar in Hg content to the late 19th century, suggesting that the increase had occurred sometime after the 1940s. In contrast, tooth Cd was not correlated with animal age and decreased during the last 100 years, indicating that anthropogenic Cd was negligible in this population. Late 19th century beluga displayed a greater range of prey selection (tooth delta15N values: 15.6-20.5 per thousand) than modern animals (delta15N: 17.2-21.1 per thousand). To prevent this difference from confounding the temporal Hg comparison, the Hg-age relationships discussed above were based on historical animals, which overlapped isotopically with the modern group. Tooth delta13C also changed to isotopically more depleted values in modern animals, with the most likely explanation being a significant shift to more pelagic-based feeding. Industrial Hg pollution is a plausible explanation for the recent Hg increase. However, without further investigation of the relationship between the range exploitation of modern beluga and their possible exposure to regional marine food chains with (naturally) higher Hg contents than their historical counterparts, we cannot unequivocally conclude that the increase was anthropogenically driven.     

Protective effect of the fruits of Terminalia arjuna against cadmium-induced oxidant stress and hepatic cell injury via MAPK activation and mitochondria dependent pathway

Cadmium (Cd), a highly toxic environmental pollutant, induces hepatic disorders. The present study has been undertaken to investigate the protective role of the fruit extract of Terminalia arjuna (AE) against Cd-induced oxidative liver impairment using a murine model. Cadmium reduced hepatocytes viability, activated MAPKs, disturbed Bcl-2 family protein balance, increased reactive oxygen species (ROS) production and induced apoptotic cell death by mitochondria dependent caspases-3 activation. AE treatment, however, suppressed all the apoptotic actions of cadmium. Similarly, mice treated with cadmium altered a number biomarkers related to hepatic oxidative stress and other apoptotic indices. Oral administration of AE both pre and post prevented all the Cd-induced hepatic damages.     

Synthesis and identification of artificial antigens for cadmium and copper

Cadmium and copper were conjugated to two carrier proteins using bifunctional chelators, including derivatives of ethylenediamine N,N,N′,N′-tetraacetic acid and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, to make artificial antigens for cadmium and copper. The artificial antigens were identified by nondenaturing gel electrophoresis, ultraviolet spectrophotometry, and graphite furnace atomic absorption spectrometry. Nondenaturing gel electrophoresis results revealed that the conjugate band migrations were different from those of the chelator-protein conjugates and carrier proteins alone. The ultraviolet spectrophotometry results revealed that the maximum absorption peak of the conjugates had only a little peak shift. The graphite furnace atomic absorption spectrometry results revealed that the metal content of the conjugates was much higher than that of the carrier proteins and chelator-protein conjugates. The results indicated that the artificial antigens for cadmium and copper were successfully synthesised and could be useful as immunising antigens.     

新显色剂NPNTT的合成及其与镉的显色反应

本文报道了1-(4-硝基苯基)-3-(4-硝基-噻唑)-三氮烯(NPNTT)的合成及其与镉的显色反应研究。在O(P聚乙二醇辛基苯基醚)的存在下,pH11.0的Na2B4O7-NaOH缓冲溶液中,该试剂能与镉发生显色反应,镉与NPNTT形成摩尔比为1:3型的配合物,在450nm处有一最大正吸收,在540nm处有一最大负吸收。以450nm为参比波长,540nm为测量波长进行双波长测定,表观摩尔吸光系数为5.23×105L/(mo·lcm),镉的浓度在0～400μg/L范围内符合比尔定律。用拟定方法测定废水中的微量镉,结果满意。