Room-temperature ferromagnetism in transparent transition metal-doped titanium dioxide

Dilute magnetic semiconductors and wide gap oxide semiconductors are appealing materials for magnetooptical devices. From a combinatorial screening approach looking at the solid solubility of transition metals in titanium dioxides and of their magnetic properties, we report on the observation of transparent ferromagnetism in cobalt-doped anatase thin films with theconcentration of cobalt between 0 and 8%. Magnetic microscopy images reveal a magnetic domain structure in the films, indicating the existence of ferromagnetic long-range ordering. The materials remain ferromagnetic above room temperature with a magnetic moment of 0.32 Bohr magnetons per cobalt atom. The film is conductive and exhibits a positive magnetoresistance of 60% at 2 kelvin.     

Giant Magnetoresistance at Low Fields in Discontinuous NiFe-Ag Multilayer Thin Films

A series of sputtered multilayers of Ni(80)Fe(20)-Ag was prepared to examine the giant magnetoresistance effect before and after annealing. For a wide range of NiFe and Ag thicknesses, no giant magnetoresistance was observed in the unannealed films. After annealing, a large, negative magnetoresistance was observed of order 4 to 6% in applied fields of order 5 to 10 oersteds at room temperature. The appearance of giant managetoresistance is concurrent with the breakup of the NiFe layers, which is attributable to a magnetostatic interaction that favors local antiparallel alignment of the moments in adjacent layers. These structures may be of significant practical importance as sensors that require large changes in resistance at low fields, such as magnetoresistive heads used in magnetic recording systems.     

Thousandfold change in resistivity in magnetoresistive la-ca-mn-o films

A negative isotropic magnetoresistance effect more than three orders of magnitude larger than the typical giant magnetoresistance of some superlattice films has been observed in thin oxide films of perovskite-like La(0.67)Ca(0.33)MnOx. Epitaxial films that are grown on LaAIO(3) substrates by laser ablation and suitably heat treated exhibit magnetoresistance values as high as 127,000 percent near 77 kelvin and approximately 1300 percent near room temperature. Such a phenomenon could be useful for various magnetic and electric device applications if the observed effects of material processing are optimized. Possible mechanisms for the observed effect are discussed.     

偏最小二乘分光光度法同时测定茶叶中良量铁、钴和镍

痕量Fe(Ⅱ）、Co（Ⅱ）和Ni（Ⅱ）与4－（2－吡啶偶氮）－间茶二酚（PAR）在pH＝8.7时发生显色反应，其吸收光谱相互严重重叠。本用偏最小二乘法（PLS）分光光度法成功地同时测定了模拟试样及茶叶是痕量铁、钴和镍。结果表明，PLS法是化学计量学中一种可适用于基体较复杂的实际试样中痕量组分同时分光光度测定的优良的多元计算方法。     

Co - H2O2-4,5-二溴邻硝基苯基荧光酮催化动力学光度法测定痕量钴(Ⅱ)

本文研究了Co(Ⅱ)在氢氧化钠介质中催化过氧化氢氧化4,5-二溴邻硝基苯基荧光酮(DBON - PF)褪色的新指示反应及影响反应速度的因素,建立了测定痕量钴的催化动力学光度新方法.方法检出限为8.5 ×10-12g/mL,Co(Ⅱ)含量在0ng/10mL～3.2ng/10mL范围内符合比尔定律,是光度法测定钴的高灵敏体系之一,本法选择性好,灵敏度高,应用于VB12中钴的测定,相对标准偏差为2.8％ ～3.4％,加标回收率为96％ ～ 104％,符合痕量分析的要求.     

影响钴在新疆荒漠区土壤中的形态分布因素研究

[目的]考察不同pH、重金属钻初始浓度、陈化时间和离子强度对土壤中钴化学形态分布和生物有效性的影响。[方法]采取经典Tessier连续提取技术。[结果]随着处理土壤pH的升高,有机物结合态含量呈下降趋势,两者间有极显著的负相关（相关系数=0．800～,P〈0．01）,残渣态随pH升高呈上升趋势,生物有效性在pH5时达到最大值。在研究初始钴浓度范围内,随着外源钴浓度的浓度的增加,土壤中钴的碳酸盐结合态和可交换态所占总钴的比例减小,生物有效性系数（K）呈明显的递减趋势,当钴浓度大于250mg／L时,K递减趋势较大;土壤环境离子强度在O．01mol／L附近时,除残渣态外各形态钴在土壤中分布的比例达到最大值,当离子强度大于0．01mol／L时,生物有效性系数降低,限制了土壤中钴的迁移性。在考察陈化时间内,土壤陈化10d时,钴的生物有效性系数最大。[结论]各形态含量均随土壤介质pH、重金属钴初始浓度、陈化时间和离子强度有所变化,不同程度地影响着重金属钴在土壤中的富集状况。     

氯化钴在大菱鲆饲料中的安全性评价

通过研究饲料中的氯化钴对大菱鲆幼鱼的存活、生长性能、血清生理生化指标、抗氧化酶活力、消化酶活力、血清和肝脏中VB12含量、肌肉和肝脏中钴的残留量、肝脏和肠道组织结构的影响来评估氯化钴在海水鱼饲料中的安全性。通过在基础饲料中添加氯化钴制剂来配制4种具有不同氯化钴含量(0、8、40及80 mg/kg,不计结晶水重量)的等氮等能的实验饲料,每个饲料处理设6个重复,每个重复养殖30尾大菱鲆;养殖实验为期10周。实验结果表明:饲料中添加氯化钴对试验鱼的存活没有显著影响(P0.05),但饲料中80 mg/kg的氯化钴显著降低了大菱鲆的特定生长率、终末体重、摄食率、肝体比和脏体比(P0.05);饲料中高剂量氯化钴(40和80 mg/kg)显著降低了大菱鲆血清过氧化氢酶、谷草转氨酶和碱性磷酸酶活力以及大菱鲆胃淀粉酶和胰蛋白酶活力(P0.05);大菱鲆的血糖含量、血清和肝脏中VB12含量、肝脏和肌肉中钴的残留量均随饲料中钴的添加量增加而显著升高(P0.05);饲料中添加氯化钴对大菱鲆的肠道组织结构没有产生明显影响,但饲料中添加40和80 mg/kg的氯化钴增宽了肝脏肝血窦。研究结果表明:实验条件下,氯化钴在大菱鲆饲料中的添加量8 mg/kg是安全的。     

Zinc and Cobalt: Effect on the Iron Metabolism of Ustilago sphaerogena

The ferrichrome content of cells of the smut fungus Ustilago sphaerogena during growth in a medium deficient in zinc increases with increase in the cobalt of the medium from 0 to 3 X 10(-5)M. The addition of zinc to such cultures prevents the accumulation of ferrichrome. The results suggest that zinc is involved in the utilization of iron via a process which can be blocked by cobalt.     

Spin-polarized resonant tunneling in magnetic tunnel junctions

Insertion of a thin nonmagnetic copper Cu(001) layer between the tunnel barrier and the ferromagnetic electrode of a magnetic tunnel junction is shown to result in the oscillation of the tunnel magnetoresistance as a function of the Cu layer thickness. The effect is interpreted in terms of the formation of spin-polarized resonant tunneling. The amplitude of the oscillation is so large that even the sign of the tunnel magnetoresistance alternates. The oscillation period depends on the applied bias voltage, reflecting the energy band structure of Cu. The results are encouraging for the development of spin-dependent resonant tunneling devices.     

Enhanced intergrain tunneling magnetoresistance in half-metallic CrO2 films

Low-field tunneling magnetoresistance was observed in films of half-metallic CrO2 that were grown by high-pressure thermal decomposition of CrO3. High-temperature annealing treatments modified the intergrain barriers of the as-grown films through surface decomposition of CrO2 into insulating Cr2O3, which led to a threefold enhancement of the low-field magnetoresistance. This enhancement indicates the potential of this simple method to directly control the interface barrier characteristics that determine the magnetotransport properties.     

放牧羊钴缺乏症的防治

选某牧场患有慢性钴缺乏病症状的羊120只(5～6月龄)，随机分为4组，每组30只。采用3种方法对其进行治疗。结果表明：3种方法均可防治本牧场羊钴缺乏。口服硫酸钴对提高羊的生产性能(增重)效果最好；钴丸组对增强缺钴羊机体免疫力及其造血、糖代谢等生理功能上效果最佳；施钴肥的效果稍逊色于其他方法，但因其方便、实用，也可作为本牧场防治钴缺乏的一种方法。     

喷施硫酸钴对紫花苜蓿产量及微量元素吸收的影响

[目的]研究苜蓿对钴的吸收利用规律及苜蓿体内微量元素之间的相互关系。[方法]在叶面喷施试验中,设喷施硫酸钴3个Co水平:100、300、600mg/kg,研究了不同施钴水平对紫花苜蓿干草产量和微量元素含量及积累量的影响。[结果]喷施硫酸钴可以显著提高苜蓿干草产量,其中施钴量为300mg/kg的处理效果最好,比对照CK(清水)提高27.53%。喷施硫酸钴可显著提高苜蓿钴和锌的含量,显著降低苜蓿硼、硒的含量,对苜蓿钼、铁、锰、铜含量没有显著的影响。喷施硫酸钴可显著提高苜蓿钴、硼、铁、锰、铜、锌等微量元素营养物质积累量,除钴积累量以施钴量为600mg/kg的处理最高外,其余元素积累量都以施钴量为300mg/kg的处理最高。喷施硫酸钴可显著降低苜蓿硒的积累量,对苜蓿钼积累量没有显著的影响。[结论]不同施钴水平对苜蓿体内微量元素的含量和微量元素营养物质的积累量影响不同。     

钴对泰和鸡产蛋性能的影响

８０只泰和鸡随机分成４组，每组２０只，分别喂给含钴０．２６，５．２６，５０．２６，１００．２６ｍｇ／ｋｇ的日粮４个月，观察鸡的体重、采食量、产蛋率、平均蛋重、蛋壳质量，试验末期检测鸡肝钴的含量。结果表明：日粮钴的本底含量（０．２６ｍｇ／ｋｇ）即能满足泰和鸡的需要，添加５ｍｇ／ｋｇ钴有利于发挥泰和鸡的最佳产蛋性能；钴对鸡的体重、平均蛋重、蛋壳质量无显性影响；肝钴含量与日粮钴含量呈高度正相关。     

钴室扩源能力计算及安全性评估

根据最新国际防护标准，采用QAD-CG程序，对上海市农业科学院钴源室的各点屏蔽参数进行验算得出如下结论该钴室扩源至3.7×10     

云南土壤钴背景值及其特征初探

云南土壤钴含量呈对数正态分布,背景值高于全国,比较高的是石灰土、水稻土、红壤,比较低的是黄棕壤、砖红壤、亚高山草甸土。云南土壤的水平地带和垂直地带钴背景值分布有着明显的变化规律;由于成土母质母岩的不同,土壤中的钴背景值有明显的差异;发育于不同成土母质母岩的红壤,钴背景值也有很大差异;发育于同种成土母质母岩上的不同土类的钴背景值也有差异;土壤钴背景值在滇中和滇西北局部地区较高。     

硫、钴对补饲尿素山羊瘤胃消化代谢的影响

用6只装有永久性瘤胃瘘管的本地空怀母山羊进行了三期试验。试验结果表明:基础日粮中添加硫或硫加钴均可提高瘤胃液PH,而只添加钴对PH无显著影响(P>0.05)。基础日粮中添加硫或钴,特别是钴,促进了瘤胃中氨的利用;增强了瘤胃中微生物合成蛋白质的能力。基础日粮中添加硫,降低了瘤胃中总挥发性脂肪酸(TVFA)的浓度,添加钴对总挥发性脂肪酸浓度无显著影响(P>0.05)。与T_1相比,T_2趋向于丙酸型发酵;T_3和T_4趋向于乙酸型发酵。四种日粮条件下,丁酸百分率无显著变化(P>0.05)。基础日粮中添加硫或钴均可提高瘤胃细菌蛋白的含量,而对瘤胃原虫蛋白含量无显著影响(P>0.05)。在山羊对尿素的利用方面,硫和钴对瘤胃内PH,氨氮浓度,三氯乙酸沉淀蛋白(TCA-P)含量,挥发性脂肪酸(VFA),细菌和原虫蛋白的影响无协同作用。     

Structure of an oxygen-carrying cobalt complex

Bis(3-fluorosalicylaldehyde) ethylenediimine cobalt(II), a reversible oxygen-carrying compound, has been crystallized as a tetramer with two oxygen molecules bound to the four cobalt atomns, each oxygen molecule bridging between two metal atoms. These dimers are further linked by two bonds between the oxygen atom of the salicylaldehyde and the cobalt atom. The oxygen-to-oxygen distance, 1.21 angstroms in molecular oxygen, has increased to 1.308(28) angstroms (where the number in parentheses is the estimated standard deviation) in this compound, the shortest distance yet observed in sutch a bridging arrangement.     

钴对泰和母鸡生殖内分泌活动的影响

将８０只泰和母鸡随机分成４组，每组２０只，分别喂给含钴０．２６ｍｇ／ｋｇ，５．２６ｍｇ／ｋｇ，５０．２６ｍｇ／ｋｇ，１００．２６ｍｇ／ｋｇ的日粮４个月。试验期间用放射免疫法监测鸡血浆中促黄体生成素（ＬＨ）、雌二醇（Ｅ２）和孕酮（Ｐ）含量的变化情况。观察钴对Ｅ２，Ｐ分泌的直接影响。结果表明：日粮钴能引起血浆ＬＨ和Ｐ值升高，但随着钴在机体内的蓄积，高钴组Ｐ值显下降；日粮然对Ｅ２的影响较小。     

高钴负荷对肉仔鸡血液粘度的影响及其与肉鸡腹水综合征发生发展的关系

300只AA肉仔鸡平均分成两组,一组为对照组,另一组为高钴负荷组（从5日龄起饮含钴80mg／L的水）。于5,30和45日龄每组随机抽取20只鸡,分别检测红细胞压积（PCV）、红细胞计数（RBC）、血红蛋白浓度（HB）、全血比粘度（BRV）和腹水心脏指数（AHI）;45日龄时扑杀所有试验鸡,观察腹水综合征发生情况。结果为：（1）高钴负荷鸡在30和45日龄时其PCV,RBC和HB显著高于对照鸡（P＜0．05）;（2）30和45日龄时高钴负荷鸡的BRV极显著高于对照鸡（P＜0．01）;（3）30和45日龄时高钴负荷鸡的AHI显著大于对照鸡（P＜0．05）,45日龄时高钴负荷鸡的腹水检出率倍增于对照鸡。本试验表明高钴负荷可诱发肉仔鸡红细胞增生,进而使血液粘度升高,最终导致右心肥大－腹水综合征。     

Ultrahigh-density nanowire arrays grown in self-assembled diblock copolymer templates

We show a simple, robust, chemical route to the fabrication of ultrahigh-density arrays of nanopores with high aspect ratios using the equilibrium self-assembled morphology of asymmetric diblock copolymers. The dimensions and lateral density of the array are determined by segmental interactions and the copolymer molecular weight. Through direct current electrodeposition, we fabricated vertical arrays of nanowires with densities in excess of 1.9 x 10(11) wires per square centimeter. We found markedly enhanced coercivities with ferromagnetic cobalt nanowires that point toward a route to ultrahigh-density storage media. The copolymer approach described is practical, parallel, compatible with current lithographic processes, and amenable to multilayered device fabrication.