Måling af produktivitet over tid: det metodiske grundlag for dynamisk benchmarking i DEA

Dynamisk benchmarking vedrører måling af ændringer i produktivitet over tid, som kan beskrives ved et Total Factor Productivity indeks. Dette indeks beskriver nettoeffekten af i) ændringer i best practice og ii) catching up effekten defineret som ændringen i den enkelte virksomheds positionering i forhold til best practice. I den foreliggende artikel beskrives, hvordan Data Envelopment Analysis kan benyttes til estimation af et Total Factor Productivity indeks, og hvordan dette indeks kan dekomponeres multiplikativt i to delkomponenter, der beskriver ændringer i best practice hhv. catching up effekter. Der gives en geometrisk intuition for dekomponeringen suppleret med et taleksempel og en mere matematisk stringent fremstilling

Måling af produktivitet over tid: det metodiske grundlag for dynamisk benchmarking i DEA

Dynamisk benchmarking vedrører måling af ændringer i produktivitet over tid, som kan beskrives ved et Total Factor Productivity indeks. Dette indeks beskriver nettoeffekten af i) ændringer i best practice og ii) catching up effekten defineret som ændringen i den enkelte virksomheds positionering i forhold til best practice. I den foreliggende artikel beskrives, hvordan Data Envelopment Analysis kan benyttes til estimation af et Total Factor Productivity indeks, og hvordan dette indeks kan dekomponeres multiplikativt i to delkomponenter, der beskriver ændringer i best practice hhv. catching up effekter. Der gives en geometrisk intuition for dekomponeringen suppleret med et taleksempel og en mere matematisk stringent fremstilling

Cryogen-Free dissolution Dynamic Nuclear Polarization polarizer operating at 3.35 T, 6.70 T and 10.1 T

Purpose: A novel dissolution dynamic nuclear polarization (dDNP) polarizer platform is presented. The polarizer meets a number of key requirements for in vitro, pre-clinical and clinical applications. Method: It uses no liquid cryogens, operates in continuous mode, accommodates a wide range of sample sizes up to and including those required for human studies, and is fully automated. Results: It offers a wide operational window both in terms of magnetic field, up to 10.1 T, and temperature, from room temperature down to 1.3 K. The polarizer delivers a 13C liquid state polarization for [1-13C]pyruvate of 70%. The build-up time constant in the solid state is approx. 1200 s (20 min), allowing a sample throughput of at least one sample per hour including sample loading and dissolution. Conclusion: We confirm the previously reported strong field dependence in the range 3.35 to 6.7 T, but see no further increase in polarization when increasing the magnetic field strength to 10.1 T for [1-13C]pyruvate and trityl. Using a custom dry magnet, cold head and recondensing, closed-cycle cooling system, combined with a modular DNP probe, automation and fluid handling systems; we have designed a unique dDNP system with unrivalled flexibility and performance.Comment: 16 pages, 8 figure

The subunit composition of human extracellular superoxide dismutase (EC-SOD) regulate enzymatic activity

<p>Abstract</p> <p>Background</p> <p>Human extracellular superoxide dismutase (EC-SOD) is a tetrameric metalloenzyme responsible for the removal of superoxide anions from the extracellular space. We have previously shown that the EC-SOD subunit exists in two distinct folding variants based on differences in the disulfide bridge pattern (Petersen SV, Oury TD, Valnickova Z, Thøgersen IB, Højrup P, Crapo JD, Enghild JJ. Proc Natl Acad Sci USA. 2003;100(24):13875–80). One variant is enzymatically active (aEC-SOD) while the other is inactive (iEC-SOD). The EC-SOD subunits are associated into covalently linked dimers through an inter-subunit disulfide bridge creating the theoretical possibility of 3 dimers (<it>aa</it>, <it>ai </it>or <it>ii</it>) with different antioxidant potentials. We have analyzed the quaternary structure of the endogenous EC-SOD disulfide-linked dimer to investigate if these dimers in fact exist.</p> <p>Results</p> <p>The analyses of EC-SOD purified from human tissue show that all three dimer combinations exist including two homo-dimers (<it>aa </it>and <it>ii</it>) and a hetero-dimer (<it>ai</it>). Because EC-SOD is a tetramer the dimers may combine to generate 5 different mature EC-SOD molecules where the specific activity of each molecule is determined by the ratio of aEC-SOD and iEC-SOD subunits.</p> <p>Conclusion</p> <p>This finding shows that the aEC-SOD and iEC-SOD subunits combine in all 3 possible ways supporting the presence of tetrameric enzymes with variable enzymatic activity. This variation in enzymatic potency may regulate the antioxidant level in the extracellular space and represent a novel way of modulating enzymatic activity.</p