Investigating the state-of-the-art in whole-body MR-based attenuation correction:an intra-individual, inter-system, inventory study on three clinical PET/MR systems

Objective We assess inter- and intra-subject variability of magnetic resonance (MR)-based attenuation maps (MRμMaps) of human subjects for state-of-the-art positron emission tomography (PET)/MR imaging systems. Materials and methods Four healthy male subjects underwent repeated MR imaging with a Siemens Biograph mMR, Philips Ingenuity TF and GE SIGNA PET/MR system using product-specific MR sequences and image processing algorithms for generating MRμMaps. Total lung volumes and mean attenuation values in nine thoracic reference regions were calculated. Linear regression was used for comparing lung volumes on MRμMaps. Intra- and inter-system variability was investigated using a mixed effects model. Results Intra-system variability was seen for the lung volume of some subjects, (p = 0.29). Mean attenuation values across subjects were significantly different (p < 0.001) due to different segmentations of the trachea. Differences in the attenuation values caused noticeable intra-individual and inter-system differences that translated into a subsequent bias of the corrected PET activity values, as verified by independent simulations. Conclusion Significant differences of MRμMaps generated for the same subjects but different PET/MR systems resulted in differences in attenuation correction factors, particularly in the thorax. These differences currently limit the quantitative use of PET/MR in multi-center imaging studies

Screening of a soil metatranscriptomic library by functional complementation of Saccharomyces cerevisiae mutants.

Metatranscriptomics applied to environmental transcripts provides unique opportunities to reveal microbial activity in the environment and to discover novel enzymes of potential use in biotechnological applications. Here, by functional complementation of a pho5(-) mutation (affecting a repressible acid phosphatase) and a his3(-) mutation in Saccharomyces cerevisiae, we identified fungal genes encoding an acid phosphatase and an imidazoleglycerol-phosphate dehydratase in a metatranscriptomic library, which was obtained by reverse-transcribed polyA fraction of total RNA extracted from the organic layer of a sugar maple forest soil, constructed in the modified yeast secretion vector pTEF-MF-SfiI A/B. Yeast transformants exhibiting phosphatase activity were identified in a colony-staining assay and transformants with his3(-)-complementing genes were detected by plating on histidine-deficient medium. In each screen one DNA insert was found and sequenced. The sequenced his3(-)-complementing gene showed strong similarity to a basidiomycete imidazoleglycerol-phosphate dehydratase (76% identity to a Phaffia rhodozyma enzyme). The candidate showing phosphatase activity was found to produce phosphatase extracellularly, the enzyme showing highest activity at pH 4 and between 40 and 50°C when 4-nitrophenyl phosphate was used as substrate. The sequenced insert showed strong similarity to a basidiomycete acid phosphatase (60% identity to Postia placenta)

Högre utbildning och miljöattityder

Det här kapitlet studerar sambandet mellan högre utbildning och miljöattityder. I den vetenskapliga litteraturen har det ofta hävdats att högre utbildning leder till förändringar i människors förmågor och värderingar, vilket i sin tur påverkar deras miljöattityder. Vi undersöker detta genom att studera förändring över tid i den allmänna miljöopinionen i Sverige, med särskilt fokus på skillnader i miljöattityder mellan grupper med respektive utan högre utbildning. Detta görs med utgångspunkt i de nationella SOM-undersökningar 1987–2016. Därefter studerar vi mer specifikt om högre utbildning är associerat med ett mer uttalat intresse för miljöfrågan, oro för miljöförstöringen och åsikter om olika miljöpolitiska förslag. Dessa analyser baseras på 2016 års SOM-undersökning. Resultaten visar att en högre utbildningsnivå vanligen leder till ett större miljöintresse och ökad oro för miljön. Utbildningsnivån tycks också spela roll för inställning till vissa miljöpolitiska förslag. Avslutningsvis diskuterar vi implikationerna av dessa resultat och ger förslag till fortsatt forskning.Climate change challenge. Solutions among students in economics, law and political scienc