Counting absolute number of molecules using unique molecular identifiers

Advances in molecular biology have made it easy to identify different DNA or RNA species and to copy them. Identification of nucleic acid species can be accomplished by reading the DNA sequence; currently millions of molecules can be sequenced in a single day using massively parallel sequencing. Efficient copying of DNA-molecules of arbitrary sequence was made possible by molecular cloning, and the polymerase chain reaction. Differences in the relative abundance of a large number of different sequences between two or more samples can in turn be measured using microarray hybridization and/or tag sequencing. However, determining the relative abundance of two different species and/or the absolute number of molecules present in a single sample has proven much more challenging. This is because it is hard to detect individual molecules without copying them, and even harder to make defined number of copies of molecules. We show here that this limitation can be overcome by using unique molecular identifiers (umis), which make each molecule in the sample distinct

High-throughput chromatin accessibility profiling at single-cell resolution.

Here we develop a high-throughput single-cell ATAC-seq (assay for transposition of accessible chromatin) method to measure physical access to DNA in whole cells. Our approach integrates fluorescence imaging and addressable reagent deposition across a massively parallel (5184) nano-well array, yielding a nearly 20-fold improvement in throughput (up to ~1800 cells/chip, 4-5 h on-chip processing time) and library preparation cost (~81¢ per cell) compared to prior microfluidic implementations. We apply this method to measure regulatory variation in peripheral blood mononuclear cells (PBMCs) and show robust, de novo clustering of single cells by hematopoietic cell type

FRÅN BONDESTAFETT TILL JÄRNVÄG: POSTVÄSENDET SOM EXEMPEL PÅ INFRASTRUKTUR OCH FÖRVALTNING I SVERIGE 1600-1870

Magnus Linnarsson: Från bondestafett till järnväg: Postväsendet som exempel på infrastruktur og förvaltning i Sverige 1600-1870 När det svenska postväsendet inrättades 1636 skapades en stafett av särskilt avdelade postbönder som transporterade posten. Stafettsystemet utgjorde postens grundläggande infrastruktur tills postbönderna i slutet av 1800-talet ersattes av transporter med postdiligens och järnväg. I artikeln analyseras den svenska postbondeinstitutionens tillkomst och avskaffande. Den svenska statens val att använda sig av postbönder var unikt i Europa och förklaras som en del av en etablerad lösning för resursmobilisering inom den svenska statsförvaltningen, så kallad indelning. Trots flera försök att ersätta postbönderna med ett annat system, fortlevde postbondeinstitutionen under 230 år. Författaren argumenterar för att systemets uthållighet berodde på den svenska statens svaga förvaltningsstrukturer under perioden. Förvaltningens begränsade resurser motverkade större institutionella förändringar av postsystemet innan industrialiseringen på 1800-talet

Effects of acceleration in the Gz axis on human cardiopulmonary responses to exercise

The aim of this paper was to develop a model from experimental data allowing a prediction of the cardiopulmonary responses to steady-state submaximal exercise in varying gravitational environments, with acceleration in the Gz axis (a g) ranging from 0 to 3g. To this aim, we combined data from three different experiments, carried out at Buffalo, at Stockholm and inside the Mir Station. Oxygen consumption, as expected, increased linearly with a g. In contrast, heart rate increased non-linearly with a g, whereas stroke volume decreased non-linearly: both were described by quadratic functions. Thus, the relationship between cardiac output and a g was described by a fourth power regression equation. Mean arterial pressure increased with a g non linearly, a relation that we interpolated again with a quadratic function. Thus, total peripheral resistance varied linearly with a g. These data led to predict that maximal oxygen consumption would decrease drastically as a g is increased. Maximal oxygen consumption would become equal to resting oxygen consumption when a g is around 4.5g, thus indicating the practical impossibility for humans to stay and work on the biggest Planets of the Solar Syste