Temporary Agency Work and Firm Competitiveness: Evidence from German Manufacturing Firms

This paper addresses the relationship between the utilization of temporary agency workers by firms and their competitiveness measured by unit labor costs, using a rich, newly built, data set of German manufacturing enterprises. The analysis is conducted by applying different panel data models while taking the inherent selection problem into account. Making use of dynamic panel data models allows us to control for firm specific fixed effects as well as for potential endogeneity of explanatory variables. The results indicate a U-shaped relationship between the extent that temporary agency workers are used and the competitiveness of firms.temporary agency work, competitiveness, firm performance, manufacturing

Generic sample preparation combined with high-resolution liquid chromatography- time-of-flight mass spectrometry for unification of urine screening in doping-control laboratories

A unification of doping-control screening procedures of prohibited small molecule substances—including stimulants, narcotics, steroids, ß2-agonists and diuretics—is highly urgent in order to free resources for new classes such as banned proteins. Conceptually this may be achieved by the use of a combination of one gas chromatography–time-of-flight mass spectrometry method and one liquid chromatography–time-of-flight mass spectrometry method. In this work a quantitative screening method using high-resolution liquid chromatography in combination with accurate-mass time-of-flight mass spectrometry was developed and validated for determination of glucocorticosteroids, ß2-agonists, thiazide diuretics, and narcotics and stimulants in urine. To enable the simultaneous isolation of all the compounds of interest and the necessary purification of the resulting extracts, a generic extraction and hydrolysis procedure was combined with a solid-phase extraction modified for these groups of compounds. All 56 compounds are determined using positive electrospray ionisation with the exception of the thiazide diuretics for which the best sensitivity was obtained by using negative electrospray ionisation. The results show that, with the exception of clenhexyl, procaterol, and reproterol, all compounds can be detected below the respective minimum required performance level and the results for linearity, repeatability, within-lab reproducibility, and accuracy show that the method can be used for quantitative screening. If qualitative screening is sufficient the instrumental analysis may be limited to positive ionisation, because all analytes including the thiazides can be detected at the respective minimum required levels in the positive mode. The results show that the application of accurate-mass time-of-flight mass spectrometry in combination with generic extraction and purification procedures is suitable for unification and expansion of the window of screening methods of doping laboratories. Moreover, the full-scan accurate-mass data sets obtained still allow retrospective examination for emerging doping agents, without re-analyzing the samples

Evidence of the indirect hormonal activity of prohormones using liver S9 metabolic bioactivation and an androgen bioassay

Prohormones such as dehydroepiandrosterone (DHEA) are steroid precursors that do not show hormonal activity by themselves. Abuse of these prohormones in cattle fattening is hard to prove because of strong in vivo metabolism and the difficulty to detect metabolites which are not significantly above endogenous levels. The aim of the present work was to develop an in vitro assay capable of detecting the indirect hormonal activity of prohormones that might be present in feed supplements and injection preparations. Sample extracts were incubated with a bovine liver S9 fraction in order to mimic the in vivo metabolic activation. Subsequently incubated extracts were exposed to a highly androgen-specific yeast bioassay to detect hormonal activity. Metabolic activation of DHEA, 4-androstene-3,17-dione (4-adione) and 5-androstene-3,17-diol (5-adiol) resulted in an increased androgenic activity caused by the formation of the active androgen 17ß-testosterone (17ß-T), as shown by ultra-performance liquid chromatography and time-of-flight mass spectrometry with accurate mass measurement. The developed in vitro system successfully mimics the hydroxysteroid dehydrogenase (HSD)- and cytochrome P450-mediated in vivo metabolic transitions, thus allowing assessment of both bioactivity and chemical identification without the use of animal experiments. Screening of unknown supplement samples claimed to contain DHEA resulted in successful bioactivation and positive screening results according to the androgen yeast biosenso

'Houd de veldwachters van de voedselveiligheid in ere'

Laboratoria kunnen steeds preciezer meten, op steeds slimmere manieren. Maar dat levert geen garanties op voor de voedselveiligheid. Dat vindt Michel Nielen van onderzoeksinstituut RIKILT en hoogleraar Organische chemie. De veranderende rol van de overheid in de voedselveiligheid heeft ons kwetsbaarder gemaakt voor grootschalige incidente

Imaging surface plasmon resonance for multiplex microassay sensing of mycotoxins

A prototype imaging surface plasmon resonance-based multiplex microimmunoassay for mycotoxins is described. A microarray of mycotoxin–protein conjugates was fabricated using a continuous flow microspotter device. A competitive inhibition immunoassay format was developed for the simultaneous detection of deoxynivalenol (DON) and zearalenone (ZEN), using a single sensor chip. Initial in-house validation showed limits of detection of 21 and 17 ng/mL for DON and 16 and 10 ng/mL for ZEN in extracts, which corresponds to 84 and 68 µg/kg for DON and 64 and 40 µg/kg for ZEN in maize and wheat samples, respectively. Finally, the results were critically compared with data obtained from liquid chromatography-mass spectrometry confirmatory analysis method and found to be in good agreement. The described multiplex immunoassay for the rapid screening of several mycotoxins meets European Union regulatory limits and represents a robust platform for mycotoxin analysis in food and feed sample

Aqueous Phase Separation:a novel and sustainable approach for membrane preparation

This thesis investigates and demonstrates how polymeric membranes can be prepared using the new and more sustainable aqueous phase separation (APS) approach. Polymeric membranes are used on huge scales for kidney dialysis, wastewater treatment, drinking water production, and as a less energy intensive alternative to conventional industrial separation processes. However, the vast majority of polymeric membranes are produced via an unsustainable and environmentally unfriendly process which uses large amounts of reprotoxic chemicals like N methyl 2 pyrrolidinone (NMP) and dimethylformamide (DMF). Unlike the conventional methods the APS approach uses a water based system using a pH or salinity switch instead of toxic organic solvents to prepare membranes. This allows for a more sustainable membrane production process without the use of reprotoxic solvents. This thesis investigates the single-polyelectrolyte approach, where a responsive polyelectrolyte solution is precipitated by a pH switch. Two different polyelectrolytes are used, poly(4 vinyl pyridine) (P4VP) which is soluble in acids and insoluble in base, and polystyrene-alt-maleic acid (PSaMA) which is soluble at neutral and basic conditions and insoluble in acid. Using a variety of parameters such as polymer concentration, acid type and concentration, salt type and concentration both open microfiltration (MF) and ultrafiltration (UF) membranes as well as dense nanofiltration (NF) membranes are prepared. These membranes can match commercially available membranes with retention in aqueous environments, have high mechanical stability and are resistant to various organic solvents. This demonstrates that the single-polyelectrolyte APS approach can match the versatility of conventional preparation methods. While there still plenty of room for improvement, this thesis marks the beginning of a new method that has the potential to significantly improve the sustainability of the membrane industry

Veterinary treatment of cows with isoxsuprine for a caesarian section may temporarily lead to residues in hair of both cow and calf

Isoxsuprine is a beta-agonist that can be used for growth promotion in cattle, but it is also used as registered veterinary medicine. To investigate if veterinary treatment of cows could lead to residues of isoxsuprine in the hair of their newborn calves, an animal experiment was performed. Four cows, treated on veterinary indication with isoxsuprine lactate (Duphaspasmin) before a caesarian section, were included in the experiment. Hair samples from cows and from their calves were analyzed. The animals were shaved every week for 16 weeks and levels of isoxsuprine were measured in hair. In the cows, the levels of isoxsuprine were highest (>15 µg/kg) just after administration of the isoxsuprine lactate. After two weeks in two cows, a sort of plateau was reached and then the levels decreased. After approximately 10-15 weeks the levels were around the CCa level of the method used (0.5 µg/kg). In calves, for the first two weeks after birth, no isoxsuprine was found above CCa level in three of the four animals. At about 20-30 days old, a maximum concentration of 4 µg/kg was found. Then the levels dropped again under the CCa level, after 60 days no levels above CCa level were found. In one animal, the levels never reached CCa level. We conclude that veterinary treatment of cows with isoxsuprine may temporarily lead to low levels of isoxsuprine in the hair of their newborn calves which can be measured for a maximum of 60 days after birth