Embedded nanostructures revealed in three dimensions

Nanotechnology creates a new challenge for materials characterization because device properties now depend on size and shape as much as they depend on the traditional parameters of structure and composition. Here we show that Z-contrast tomography in the scanning transmission electron microscope has been developed to determine the complete three-dimensional size and shape of embedded structures with a resolution of approximately 1 cubic nanometer. The results from a tin/silicon quantum dot system show that the positions of the quantum dots and their size, shape, structure, and formation mechanism can be determined directly. These methods are applicable to any system, providing a unique and versatile three-dimensional visualization tool.     

均匀磁场中的辐射带电粒子的经典运动

在经典电动力学的基础上,讨论了辐射阻尼影响下非相对论性带电粒子在均匀磁场中的经典运动.导出了辐射带电粒子的运动方程（阿伯拉罕-洛仑兹方程）,利用微扰法求解该运动方程的初值,得到了带电粒子的轨道方程,得出带电粒子辐射功率随时间的变化规律,并讨论了所得结果的适用性.     

Scroll-shaped waves of chemical activity in three dimensions

Ferric ions catalyze the oxidation of malonate by bromate in acid solution, sometimes at a spatially uniform, steady rate, but sometimes in a self-regenerating three-dimensional wave which resembles a rotating scroll, often with its axis closed in a ring. In cross section perpendicular to the axis, one sees an involute spiral emerging from a thin cylindrical core. This "dissipative structure" organizes reaction stages periodically in space and time everywhere except along its rotation axis, which may therefore be a thermodynamically unique locus.     

论罗杰斯人本主义教育思想的三重维度

罗杰斯人本主义教育思想以全新的视角阐述了一种新型教育方式。在新时代,重温罗 杰斯人本主义教育思想对高校思想政治教育工作仍具有时代价值。     

玉米果穗轴截面在籽粒产量预测中的应用

玉米杂交种田间测产是玉米育种和栽培科技成果评价的一项必要工作。研究了用果穗轴截面预测单株籽粒产量的方法,结果表明:(1)果穗轴截面承载力为2.02 g/cm2左右,是一个比较稳定的参数;(2)单株籽粒产量大约是果穗轴截面积的2.02倍;(3)单株籽粒产量的预测平均值与实际平均值十分接近,误差较少;(4)单株籽粒产量的预测平均值与种植密度的乘积能较准确地估计出单位面积籽粒产量,是一种简单易行、准确可靠的测产方法。     

Forming electrical networks in three dimensions by self-assembly

Self-assembly of millimeter-scale polyhedra, with surfaces patterned with solder dots, wires, and light-emitting diodes, generated electrically functional, three-dimensional networks. The patterns of dots and wires controlled the structure of the networks formed; both parallel and serial connections were generated.     

Composites reinforced in three dimensions by using low magnetic fields

The orientation and distribution of reinforcing particles in artificial composites are key to enable effective reinforcement of the material in mechanically loaded directions, but remain poor if compared to the distinctive architectures present in natural structural composites such as teeth, bone, and seashells. We show that micrometer-sized reinforcing particles coated with minimal concentrations of superparamagnetic nanoparticles (0.01 to 1 volume percent) can be controlled by using ultralow magnetic fields (1 to 10 milliteslas) to produce synthetic composites with tuned three-dimensional orientation and distribution of reinforcements. A variety of structures can be achieved with this simple method, leading to composites with tailored local reinforcement, wear resistance, and shape memory effects.     

Simulation of airflow and particle motion in a direct-flow spray dryer

The airflow motion in an upright direct-flow drying chamber is modeled with a heat carrier centrally fed to a cone of centrifugally sprayed dry milk particles. The calculations to describe this process are presented. Taking account of the gas dynamics of submerged jet motion, the derived dependences are compared with the results of testing a commercial spray dryer with a capacity of 500 kg of evaporated moisture per hour.     

制度环境三维度及其交互作用对家庭农场创业绩效?的影响研究

家庭农场是新时代乡村振兴的新动力,其创业绩效与制度环境关系问题受到广泛关注。基于组织社会学的制度理论,选取浙江省的111个家庭农场作为样本数据,使用层次回归模型,分析制度环境的规制性要素、规范性要素和认知性要素三维度及其交互作用对家庭农场创业绩效的影响关系。结果表明,仅有认知性要素对家庭农场创业绩效具有直接显著的影响效果,而规制性要素和规范性要素对家庭农场创业绩效的直接影响效果不显著;虽然规制性要素和规范性要素无法直接促进家庭农场创业绩效显著提升,但它们均在认知性要素与家庭农场创业绩效之间扮演正向调节的角色。研究表明,有效提升家庭农场创业绩效需要协调发挥认知性要素的直接作用,规制性要素和规范性要素的调节作用。因此,从政府的角度来说应重点加强家庭农场主的职业培训,不断完善家庭农场的政策框架。     

Conditioned reinforcement in the goldfish

Goldfish were trained to press a lever on a 10:1 fixed-ratio schedule of reinforcement. They were extinguished under three conditions. Responding was followed by (i) solenoid noise and water delivery formerly associated with food reinforcement, (ii) solenoid noise only, or (iii) nothing. The number of extinction responses was largest in condition 1, less in condition 2, and smallest in condition 3, thus providing evidence for conditioned reinforcement in goldfish.     

Common pathogenetic mechanism for three tumor types in bilateral acoustic neurofibromatosis

Bilateral acoustic neurofibromatosis (BANF) is a genetic defect associated with multiple tumors of neural crest origin. Specific loss of alleles from chromosome 22 was detected with polymorphic DNA markers in two acoustic neuromas, two neurofibromas, and one meningioma from BANF patients. This indicates a common pathogenetic mechanism for all three tumor types. The two neurofibromas were among three taken from the same patient, and both showed loss of identical alleles demonstrating that the same chromosome suffered deletion in both tumors. The third neurofibroma from this patient showed no detectable loss of heterozygosity, which suggests the possibility of a more subtle mutational event that affects chromosome 22. In the two acoustic neuromas, only a portion of chromosome 22 was deleted, narrowing the possible chromosomal location of the gene that causes BANF to the region distal to the D22S9 locus in band 22q11. The identification of progressively smaller deletions on chromosome 22 in these tumor types may well provide a means to clone and characterize the defect.     

夏季3种生境森林内空气颗粒物变化特征

研究不同生境类型城市森林内空气颗粒物的变化特征及其影响因素,为休闲保健型城市森林的营造提供理论依据。于2015年夏季对深圳园山山麓(SL)、河谷(HG)和山脊(SJ)3种典型生境类型城市森林内的空气颗粒物(TSP、PM₁₀、PM_2.5、PM₁)进行昼夜24h监测,并同步观测气象因子,分析3种森林内颗粒物质量浓度的变化规律及影响因素。结果表明:1)深圳园山3种生境城市森林内TSP、PM₁₀质量浓度日均值都达到二类环境功能区质量要求,其中HG、SJ的TSP质量浓度甚至达到一类环境功能区质量要求(120μg/m3);PM_2.5质量浓度日均值都达到一类环境功能区质量要求(35μg/m3)。2)不同生境林地内各粒径颗粒物质量浓度存在差异,4种粒径颗粒物日均质量浓度在SJ均为最低(分别为85.51、58.82、14.29、5.13μg/m3);TSP、PM₁₀质量浓度在SL最高(分别为162.19、95.39μg/m3);PM_2.5、PM₁质量浓度在HG最高(分别为21.76、8.29μg/m3)。3)3种林地内4种粒径颗粒物质量浓度总体表现为白天低、夜间高的特点,高峰出现在01:00—07:00,低谷出现于11:00—15:00。4)3种林地间相对湿度、风速、气压等气象因子存在差异;林内4种粒径颗粒物质量浓度与温度、风速表现为显著负相关,与相对湿度呈显著正相关,颗粒物质量浓度变化受多种气象因子共同影响。基于上述研究认为,深圳园山3种生境类型城市森林均为人们提供了一个相对健康的森林游憩环境,人们在11:00—15:00进行森林游憩最为适宜。