Electrophoresis in capillary cells with detection gap

A novel design of the detection zone in multicapillary arrays used for electrophoretic separation is presented. The use of a detection gap (DG), in which the reflective surfaces separating the channels of the array are eliminated, is proposed to improve the illumination and detection of the separated DNA fragments. The electric field compression in the DG is achieved by optimization of the gap geometry. The results of the computer simulation and experiment demonstrate no substantial band-broadening in the DG. We believe that the proposed method will be useful for application in the microfabricated devices.     

Coupling of SPME with MCC/UV–IMS as a tool for rapid on-site detection of groundwater and surface water contamination

The combination of headspace solid phase microextraction (HS-SPME) [1] with fast chromatographic pre-separation by means of multi-capillary columns (MCC) coupled to an ion mobility spectrometer equipped with a 10.6 eV photoionisation source was applied to rapid on-site monitoring of ground and surface water contaminations. Under field conditions, water contaminants were directly detectable down to the upper g/L range. The potential of the developed method is illustrated by measurements of BTEX, naphthalene, chlorinated alkenes and chlorinated benzenes in water. Practical results from investigations of contaminated groundwater at a former gasworks site and groundwater from the site of a metal processing plant, focusing on the key substances benzene, naphthalene and tetrachloroethene, demonstrate the feasibility of the system for field studies.Dedicated to the memory of Wilhelm Fresenius. One of the authors (D. Klockow) feels very much indebeted to Prof. Fresenius because of the steady support and advice he received through him, as a professional and as a private person.     

Inverse-preserving Linear Maps Between Spaces of Matrices over Fields

Suppose F is a field different from F2, the field with two elements. Let Mn（F） and Sn（F） be the space of n × n full matrices and the space of n ×n symmetric matrices over F, respectively. For any G1, G2 ∈ {Sn（F）, Mn（F）}, we say that a linear map f from G1 to G2 is inverse-preserving if f（X）^-1 = f（X^-1） for every invertible X ∈ G1. Let L （G1, G2） denote the set of all inverse-preserving linear maps from G1 to G2. In this paper the sets .L（Sn（F）,Mn（F））, L（Sn（F）,Sn（F））, L （Mn（F）,Mn（F）） and L（Mn （F）, Sn （F）） are characterized.     

引力的曲率平方理论

利用法坐标对局部等效原理、以及局部等效原理在构造曲率平方可重整拉氏量中的作用进行了论证．得到了曲率平方引力的场方程、其线性近似以及有质引力粒子的Ｙｕｋａｗａ势的表式．     

Influence of field evaporation treatment on the field emission properties of carbon nanotubes array

Field evaporation was used in the post-fabrication treatment of a carbon nanotubes (CNTs) array and effectively modified the CNTs morphology in favor of the field emission under a moderate field. After the field evaporation treatment, the uniformity of the emission site distribution improved but the onset voltage rose. Using the Fowler-Nordheim theory, the actual onset field and the evaporation field around the CNT were calculated to be −4.6-5 and 9-12 V/nm, respectively. These values are close to those obtained from the individual CNT samples. The above results have provided an alternative to modify the configuration of an array sample and demonstrated the feasibility of tackling the problem of the disparity in the field emission capability of different CNTs in an array.     

Formation of aligned ZnO nanorods on self-grown ZnO template and its enhanced field emission characteristics

We report a novel method for producing aligned ZnO nanorods (ANR) on self-grown ZnO template in a single step process involving growth of ZnO by vapor transport, followed by quenching of growing ZnO flux in liquid nitrogen. In the present study Zn powder turns into ZnO sheet under oxygen flow at ∼900 °C and bottom surface of the sheet acts as template for the growth of ANR. It is revealed from XRD and EDAX analysis that the bottom of the sheet is Zn rich region and acts as self catalyst for the growth of ANR. The grown nanorods have length up to several tens of micrometers with diameters ranging from ∼100 to 150 nm. Microstructural analysis of ANR indicates the fractal like configuration. The field emission properties have been investigated for ANR with fractal geometry using the ANR on self-grown ZnO template as a cathode directly. The turn-on electric field required to draw current density of ∼1.0 μA/cm² has been found to be ∼0.98 V/μm. The field enhancement factor based on Fowler-Nordheim (F-N) plot was found to be ∼7815 for ANR. The fractal geometry of ANR has been shown to be advantageous for achieving improved field emission features. The present investigations of synthesis involving formation of ANR over self-grown ZnO template, together with fractal configuration of the as-synthesized ANR, are first of their type.     

Discretization error for the maximum of a Gaussian field

The paper considers the difference between (a) the true maximum of a Gaussian field on a square and (b) its maximum on a regular grid. This difference is called the discretization error. A kind of Slepian model is used to study the behavior of the field around the location of the maximum. We show that the normalized discretization error can be bounded by a quantity that converges to a uniform variable, depending on the Hessian matrix at the point of the maximum. The bound is applied to simulated and real data (satellite positioning data).     

电磁波检测

当今无线通讯技术迅猛发展,如何对变电所及输电线与移动电话基地台所产生的电磁场强度进行评估,便成为一个重要的工作.通过分析电磁波特征,论述了对这些电磁波辐射设施所产生的电磁场强度检测的方法.     

永磁体外部磁场的不均匀性研究

从永磁体的分子电流观点、退磁场、工艺等出发, 以矩形永磁体为例, 从理论上分析了影响永磁体外部磁场不均匀性的各种因素.研究结果表明, 永磁体外部磁场宏观不均匀性(好场区均匀度和面积相对大小) 和空间距离及永磁体的外形设计密切相关. 退磁场对永磁体外部磁场微观不均匀性有着复杂影响. 永磁体工艺如粉末颗粒、取向度、烧结凝固、机械加工等将影响永磁体外部磁场的不均匀性, 如磁化偏角、对称性、光滑性等. 关键词： 永磁体 外部磁场 不均匀性 退磁场     

FJ中子屏蔽层设计及虚拟装配

基于单元块的概念设计,对FJ中子屏蔽层进行了空间布局,并提出命名方法。基于真空室扇区与扇区接口确定的虚拟设计空间,将三维模型特征数字化。通过反求设计方法,对FJ中子屏蔽层进行了结构设计。为缩短设计周期,提高设计效率,采用了骨架建模和Instance建模方法。同时,对FJ中子屏蔽层进行了虚拟装配。