The MetabolomeExpress Project: enabling web-based processing, analysis and transparent dissemination of GC/MS metabolomics datasets

<p>Abstract</p> <p>Background</p> <p>Standardization of analytical approaches and reporting methods via community-wide collaboration can work synergistically with web-tool development to result in rapid community-driven expansion of online data repositories suitable for data mining and meta-analysis. In metabolomics, the inter-laboratory reproducibility of gas-chromatography/mass-spectrometry (GC/MS) makes it an obvious target for such development. While a number of web-tools offer access to datasets and/or tools for raw data processing and statistical analysis, none of these systems are currently set up to act as a public repository by easily accepting, processing and presenting publicly submitted GC/MS metabolomics datasets for public re-analysis.</p> <p>Description</p> <p>Here, we present MetabolomeExpress, a new File Transfer Protocol (FTP) server and web-tool for the online storage, processing, visualisation and statistical re-analysis of publicly submitted GC/MS metabolomics datasets. Users may search a quality-controlled database of metabolite response statistics from publicly submitted datasets by a number of parameters (eg. metabolite, species, organ/biofluid etc.). Users may also perform meta-analysis comparisons of multiple independent experiments or re-analyse public primary datasets via user-friendly tools for t-test, principal components analysis, hierarchical cluster analysis and correlation analysis. They may interact with chromatograms, mass spectra and peak detection results via an integrated raw data viewer. Researchers who register for a free account may upload (via FTP) their own data to the server for online processing via a novel raw data processing pipeline.</p> <p>Conclusions</p> <p>MetabolomeExpress <url>https://www.metabolome-express.org</url> provides a new opportunity for the general metabolomics community to transparently present online the raw and processed GC/MS data underlying their metabolomics publications. Transparent sharing of these data will allow researchers to assess data quality and draw their own insights from published metabolomics datasets.</p

Attitude reconstruction of ROSETTA's Lander PHILAE using two-point magnetic field observations by ROMAP and RPC-MAG

AbstractAs part of the European Space Agency׳s ROSETTA Mission the Lander PHILAE touched down on comet 67P/Churyumov–Gerasimenko on November 12, 2014. The magnetic field has been measured onboard the orbiter and the lander. The orbiter׳s tri-axial fluxgate magnetometer RPC-MAG is one of five sensors of the ROSETTA Plasma Consortium. The lander is also equipped with a tri-axial fluxgate magnetometer as part of the ROSETTA Lander Magnetometer and Plasma-Monitor package (ROMAP). This unique setup makes a two point measurement between the two spacecrafts in a relatively small distance of less than 50km possible. Both magnetometers were switched on during the entire descent, the initial touchdown, the bouncing between the touchdowns and after the final touchdown. We describe a method for attitude determination by correlating magnetic low-frequency waves, which was tested under different conditions and finally used to reconstruct PHILAE׳s attitude during descent and after landing. In these cases the attitude could be determined with an accuracy of better than ±5°. These results were essential not only for PHILAE operations planning but also for the analysis of the obtained scientific data, because nominal sources for this information, like solar panel currents and camera pictures could not provide sufficient information due to the unexpected landing position

Gravitational gradients by tensor analysis with application to spherical coordinates

This contribution deals with the derivation of explicit expressions of the gradients of first, second and third order of the gravitational potential. This is accomplished in the framework of tensor analysis which naturally allows to apply general formulae to the specific coordinate systems in use in geodesy. In particular it is recalled here that when the potential field is expressed in general coordinates on a 3D manifold, the gradient operation leads to the definition of the covariant derivative and that the covariant derivative of a tensor can be obtained by application of a simple rule. When applied to the gravitational potential or to any of its gradients, the rule straightforwardly provides the expressions of the higher-order gradients. It is also shown that the tensor approach offers a clear distinction between natural and physical components of the gradients. Two fundamental reference systems---a global, bodycentric system and a local, topocentric system, both body-fixed---are introduced and transformation rules are derived to convert quantities between the two systems. The results include explicit expressions for the gradients of the first three orders in both reference systems