Zur Autoradiographie mehrerer Komponenten in einer Probe: Bestimmung der Verteilung von 24Na und 45Ca in Silikatbaustoffproben

Die einfachste Möglichkeit der autoradiographischen Abbildung mehrerer Radionuklide in einer Probe besteht bei genügend unterschiedlichen Halbwertszeiten. Ein Rechenbeispiel zeigt, daβ auch bei günstigen Abstufungen der Halbwertszeiten und spezifischen Aktivitaäten für praktishche Anwendungen nicht mehr als drei Radionuklide ohne gegenseitige Störung nacheinander autoradiographiert werden können. Bei der Unterschung von Silikatbaustoffproben wurde nach der Neutronenaktivierung erst die Verteilung der ²⁴Nu und danach die des ¹⁵Ca abgebildet.     

Numerical investigation of microchannel geometry for effective on-chip biofluid delivery by AC electrothermal effect

Although there exist tremendous needs for on-chip biofluid delivery, research in this field has yielded limited numbers of devices for real-world applications. One challenge is the difficulty for micropumps to meet the requirements of being low cost to fabricate, easy to integrate and effective for intended applications at the same time. This research focuses on AC electrothermal (ACET) micropumps based on planar interdigitated electrodes, due to their practicality in fabrication and operation, and compatibility with biochemical fluids. Our prior work has optimized the design of electrode dimensions for a fixed microchannel design. This work finds that microchannel dimensions can also affect ACET micropumps significantly, with respect to flow rate and electric impedance loading. This work first considers the constraints arising from impedance loading by ACET micropumps on power supplies, then the investigation describes several key parameters (threshold height, saturation thickness), to arrive at an appropriate microchannel geometry for the effective delivery of biofluids. The optimized microchannel is expected to incorporate well into a multifunctional lab-chip system to transport biofluids efficiently.     

Epitope mapping of monoclonal antibodies by mass spectrometry: Identification of protein antigens in complex biological systems

We describe the application of immunoaffinity extraction and mass spectrometry to the analysis of Ty1 Gag protein in lysates of Saccharomyces cerevisiae. A magnetic bead-conjugated monoclonal antibody was used to achieve selective extraction, the specificity of which was established by matrix-assisted laser desorption/ionization mass spectrometric (MS) analysis of an extract of the lysate of cells overexpressing the Ty1 Gag protein. MS analysis of similar extracts of lysates following tryptic hydrolysis confirmed selective extraction of the epitope-containing peptide fragment. Sufficient sensitivity was achieved to allow the application of this approach to the analysis of lysates of wild-type cells. Furthermore, the sequence of the epitope-containing peptide was confirmed by electrospray-tandem MS. To our knowledge, this constitutes the first report of the application of immunoaffinity extraction and tandem MS analysis to the characterization of an antigen recovered from a complex cellular system.     

The extremal structure of convex sets

Banach spaces contain convex sets having pathological sets of extreme points.     

Assignment games,chromatic number,and exchange theory

The exchange networks that social psychologists have studied can usefully be represented as game theoretic 2‐sided assignment games. Conceiving of these networks as 2‐sided assignment games opens up the possibility of studying N‐sided assignment games and games without cores. 2‐sided assignment games are special in that they always have cores, stable solutions in which every individual and subgroup behave rationally.

The implicit assignment of positions to categories of an N‐sided assignment game is related to coloring a graph. The color classes form sets of positions with potentially related interests. Color equivalence is compared to structural, regular, automorphic, and ecological positional equivalence.     

Bridging the Gap Between First and Second Semester General Chemistry: A Laboratory Exercise

A simple yet challenging exercise that reviews many fundamental chemical concepts and laboratory techniques from first semester general chemistry is offered for use in the first laboratory period of the second semester general chemistry course. This exercise is easy to do and involves a minimal amount of equipment and reagents. Students at the authors school like this exercise because they get good results, yet feel challenged because they have to think for themselves.     

Improving data quality in food composition databanks: a EuroFIR contribution

Food composition databanks (FCDBs) should provide nutrient composition data comparable over time at national and international levels. However, the linkage between national database compilers and permanent structures to support the upgrading and monitoring of nutrient values in foods are far from satisfactory. This paper focuses on European efforts to improve the quality of nutrient values entered into FCDBs, emphasizing initiatives under the EU Network of Excellence: European Food Information Resource (EuroFIR – NoE). The general concept of quality assurance is described and results obtained in the project’s first year are presented. A survey among EuroFIR partners aimed at evaluating the current situation in comparability of nutrient values suggests that an integrated approach has two requirements: the implementation of a quality management system (QMS) and a harmonized data-quality assessment system (DQAS) to select values from different sources. The use of reference materials (RMs) is a key criterion in deciding on comparability and reliability of candidate nutrient values. Consequently, results of a survey on food matrix reference materials are presented. These suggest that developments in RMs for nutrient analysis in foods have a great impact on the quality of data to be included in FCDBs.     

Acylation of aromatic ethers over solid acid catalysts: scope of the reaction with more complex acylating agents

Acylation of anisole with 2-phenylbutanoic acid derivatives, over zeolite catalysts, gives the corresponding 4-acyl derivatives with high regioselectivity. In an analogous way, 2,3-dihydrobenzofuran reacts with acid anhydrides or chlorides in the presence of catalytic quantities of zeolites to give the corresponding 5-acyl-2,3-dihydrobenzofurans. The zeolite can be recovered, regenerated and used again to give almost the same yield as with fresh zeolite. The reaction has been applied to the synthesis of ethyl (2,3-dihydrobenzofuran-5-yl)glyoxylate.