基于商用坐标测量机的3D微纳米计量

以测量精度为1μm的商用坐标测量机（CMM）为基础,构建了测量范围为25mm×40mm×25mm、测量不确定度约为O．15μm的PTB微纳米专用坐标测量机．研究了CMM的运动控制系统、恒温室的空调系统以及CMM的被动隔振系统等对测量结果的影响．由测量结果可以看出,CMM的运动控制系统产生的噪声水平约为其他误差源的2倍．通过FFT运算,发现未优化系统的短时最大漂移量发生频率为750Hz,对应为运动控制的工作频率．文中还介绍了测量力为1州光纤探针的测量原理,并给出了对2．5mm短轴的测量结果．     

A unified statistical framework for monitoring multivariate systems with unknown source and error signals

This article proposes a unified multivariate statistical monitoring framework that incorporates recent work on maximum likelihood PCA (MLPCA) into conventional PCA-based monitoring. The proposed approach allows the simultaneous and consistent estimation of the PCA model plane, its dimension and the error covariance matrix. This paper also invokes recent work on monitoring non-Gaussian processes to extract unknown Gaussian as well as non-Gaussian source signals from recorded process data. By contrasting the unified framework with PCA-based process monitoring using a simulation example and recorded data from two industrial processes, the proposed approach produced more accurate and/or sensitive monitoring models.     

Speciation analysis of gadolinium-based MRI contrast agents in blood plasma by hydrophilic interaction chromatography/electrospray mass spectrometry

The first analytical method for simultaneous speciation analysis of five of the most important gadolinium-based magnetic resonance imaging (MRI) contrast agents in blood plasma samples was developed. Gd-DTPA (Magnevist), Gd-BT-DO3A (Gadovist), Gd-DOTA (Dotarem), Gd-DTPA-BMA (Omniscan), and Gd-BOPTA (Multihance) were separated by hydrophilic interaction liquid chromatography (HILIC) and detected with electrospray mass spectrometry (ESI-MS). Spiking experiments of blank plasma with Magnevist and Gadovist were performed to determine the analytical figures of merit and the recovery rates. The limits of detection ranged from 1 x 10 (-7) to 1 x 10 (-6) mol/L depending on the ionization properties of the individual compounds, and limits of quantification ranged from 5 x 10 (-7) to 5 x 10 (-6) mol/L. The linear concentration range comprised 2 orders of magnitude. With application of this method, blood plasma samples of 10 healthy volunteers, with Magnevist or Gadovist medication, were analyzed for Gd-DTPA and Gd-BT-DO3A, respectively. The obtained results were successfully validated with inductively coupled plasma-optical emission spectroscopy (ICP-OES).     

Development of a countergradient parking system for gradient liquid chromatography with online biochemical detection of serine protease inhibitors

A gradient HPLC approach in combination with a countergradient system for online biochemical detection (BCD) to screen for inhibitors of serine proteases is described. For gradient separations, this novel countergradient system was developed to produce a biocompatible constant solvent composition in the BCD. The countergradient system is based on retaining complete gradients in an additional preparative HPLC column, followed by subsequent and reversible elution to the separation column effluent. Major advantages compared with existing countergradient systems are that no additional LC pumps are needed and enhanced stability. The developed countergradient system was systematically characterized applying different gradient programs. Inhibitors eluting in a postcolumn continuous flow analysis interfere with the enzymatic release of fluorescent 7-amino-4-methylcoumarin (AMC) from an AMC-labeled peptide. The inhibitory activity of eluting substances is sensitively detected as the degree of reduced fluorescence intensity. This biochemical detection system (BCD) for proteases was validated with three known inhibitors of the benzamidine type. Their IC 50 values were in good accordance with the results of conventional plate reader assays. Finally, a small library of protease inhibitors was successfully screened with the combination of the BCD and the countergradient system.     

Liquid chromatography/coordination ion spray-mass spectrometry for the analysis of rubber vulcanization products

Liquid chromatography/coordination ion spray-mass spectrometry has been used for the identification of reaction products in a model rubber vulcanization process. After LC separation using reversed-phase conditions, AgBF(4) in acetonitrile was added, and strong signals were observed for silica-rubber coupling agents and products of the reaction between these and alkenes. The method performs best for substances containing sulfur chains with chain lengths between two and eight sulfur atoms, but sulfur-free compounds containing triethoxysilyl groups were detected as well. For the latter, the postcolumn addition of NaBF(4) proved to be a suitable alternative. Besides the coupling agents, various reaction products, including sulfur-chain bridged alkenes were identified.     

S-layer proteins as supporting scaffoldings for functional lipid membranes

A great challenge is the coupling of very sensitive microelectronic devices to wet biological systems in the generation of biomimetic sensors. Lipid membranes on solid supports (electrodes or semiconductors) may become the matrix of future bioelectronic devices probing and controlling biomolecular processes for scientific and technical applications. A sufficient electrical isolation between the coupling region and the surrounding electrolyte is mandatory. An attached lipid membrane with integral natural or designed proteins may be the material of choice if the biological components are kept in a proper environment. To retain the fluidity and stability of the lipid membrane and to provide an ion reservoir and space for bulky integral proteins, a separating layer composed of crystalline arrays of monomolecular proteinaceous subunits, termed S-layer, can be self-assembled on metal or semiconductor surfaces. In this way S-layer-supported lipid membranes are biomimetic structures mimicking the supramolecular principle of archeal cell envelopes. These composite architectures may ascend toward exciting new key devices, particularly in fields of membrane protein-based biosensors or lab-on-a-chip technology.     

Metabolite identification of a radiotracer by electrochemistry coupled to liquid chromatography with mass spectrometric and radioactivity detection

Radioligands, which specifically bind to a receptor or enzyme (target), enable molecular imaging of the target expression by positron emission tomography (PET). One very promising PET tracer is (S)-1-(4-(2-[(18)F]-fluoroethoxy)benzyl)-5-[1-(2-methoxymethylpyrrolidinyl)sulfonyl]isatin (isatin), a caspase-3 inhibitor, which has been developed at the University Hospital of Mu?nster to image cell death (apoptosis). The translation of this novel tracer from preclinical evaluation to clinical examinations requires biodistribution studies, which characterize the pharmakodynamics and metabolic fate of the compound. This information is used to further optimize the radioligands and to interpret radioactive signals from tissues upon injection of the radioligand in vivo with respect to their specificity. The analysis of the metabolism of radioligands is hampered by the low amount of the compound being typically injected (nano/picomolar amount per injection). In the present study, electrochemistry (EC) is applied to elucidate the oxidative metabolism pathway of the radiotracer. Previous studies have demonstrated that EC can be utilized as a complementary tool to conventional in vitro approaches in drug metabolism studies. Thereby, potential oxidative metabolites of the isatin are determined by EC coupled to electrospray ionization mass spectrometry (EC/ESI-MS). Moreover, using EC/liquid chromatography (LC) and ESI-ion trap MS(n), structural elucidation of the oxidation products is performed. Comparatively to EC, in vitro metabolism studies with rat liver microsomes are conducted. Finally, the developed LC/ESI-MS method is applied to determine metabolites in body fluids and cell extracts from in vivo studies with the nonradioactive ((19)F) and radioactive isatin ((18)F). On the basis of the electrochemically generated oxidation products of the radioligand, the major radioactive metabolite occurring in vivo was successfully identified.     

Simultaneous tridiagonalization of two symmetric matrices

We show how to simultaneously reduce a pair of symmetric matrices to tridiagonal form by congruence transformations. No assumptions are made on the non‐singularity or definiteness of the two matrices. The reduction follows a strategy similar to the one used for the tridiagonalization of a single symmetric matrix via Householder reflectors. Two algorithms are proposed, one using non‐orthogonal rank‐one modifications of the identity matrix and the other, more costly but more stable, using a combination of Householder reflectors and non‐orthogonal rank‐one modifications of the identity matrix with minimal condition numbers. Each of these tridiagonalization processes requires O(n³) arithmetic operations and respects the symmetry of the problem. We illustrate and compare the two algorithms with some numerical experiments. Copyright © 2003 John Wiley & Sons, Ltd.     

Liquid chromatography with on-line electrochemical derivatization and fluorescence detection for the determination of phenols

A new methodological approach for the determination of monosubstituted phenols is described. After liquid chromatographic separation of the analytes, an on-line electrochemical derivatization is carried out and the reaction products are detected fluorometrically. Phenols are oxidized in the electrochemical cell to form fluorescent dimers and higher oligomers, which were identified by on-line electrochemistry/mass spectrometry. Major advantages of the proposed method include enhanced selectivity and sensitivity. Without prior enrichment of the analytes, limits of detection down to 2 x 10(-9) M (20 fmol) may be reached for selected phenols, e.g., for 4-octylphenol, 4-ethylphenol, and 4-(1-indanyl)phenol. Only readily available instrumentation is required for these measurements.