Online data services at the Belgian Marine Datacentre

Over the past few years, the Management Unit of the North Sea Mathematical Models (MUMM) has built up a centre of human and technical expertise oriented towards the management and the analysis of marine environmental data. The Belgian Marine Data Centre (BMDC) serves as national repository and processing centre for marine and environmental data and ensures a continuous and scientifically sound data flow between data producers and end-users of marine and environmental data collected in the frame of national and international research and monitoring programmes. The data cover most domains of oceanology as there are: physico-chemical, optical parameters, biodiversity, hydrodynamics, sedimentology, geography and human interest. Most of the datasets relate to the Belgian Continental Shelf, the Scheldt estuary and its surrounding areas.To promote the use of a high variety of data sets, different tools are constantly being developed and are presented on our website (www.mumm.ac.be/datacentre). An interface to the integrated database on the quality of the marine environment was developed. This database mainly contains the results of measurements and observations in situ and laboratory analyses of air, water, sediment and biota samples. Besides an extensive inventory of the database and an advanced request form with several selection criteria, some more straightforward queries and geographical selection tools are being developed for a faster and easier access to a specific dataset. Data can freely be downloaded. Once the data are obtained, a spatial analysis tool is freely and online available for the visualization on an interactive map. A lot of documentation accompanying the data is online available. The strongest feature of this system is the common underlying structure for different kinds and sources of data. This opens the possibility to compare biodiversity data, physico-chemical data, sedimentological data and historical data.Another database at MUMM, the real-time data acquisition system ‘ODAS’ stores the physical and chemical parameters measured onboard of the research vessel RV Belgica since 1984. The along -track data are published online shortly after the end of the measurement campaign together with all other information like the campaign reports, cruise tracks, … This is a valuable source of basic information for the scientists

Online data services at the Belgian Marine Datacentre

Over the past few years, the Management Unit of the North Sea Mathematical Models (MUMM) has built up a centre of human and technical expertise oriented towards the management and the analysis of marine environmental data. The Belgian Marine Data Centre (BMDC) serves as national repository and processing centre for marine and environmental data and ensures a continuous and scientifically sound data flow between data producers and end-users of marine and environmental data collected in the frame of national and international research and monitoring programmes. The data cover most domains of oceanology as there are: physico-chemical, optical parameters, biodiversity, hydrodynamics, sedimentology, geography and human interest. Most of the datasets relate to the Belgian Continental Shelf, the Scheldt estuary and its surrounding areas.To promote the use of a high variety of data sets, different tools are constantly being developed and are presented on our website (www.mumm.ac.be/datacentre). An interface to the integrated database on the quality of the marine environment was developed. This database mainly contains the results of measurements and observations in situ and laboratory analyses of air, water, sediment and biota samples. Besides an extensive inventory of the database and an advanced request form with several selection criteria, some more straightforward queries and geographical selection tools are being developed for a faster and easier access to a specific dataset. Data can freely be downloaded. Once the data are obtained, a spatial analysis tool is freely and online available for the visualization on an interactive map. A lot of documentation accompanying the data is online available. The strongest feature of this system is the common underlying structure for different kinds and sources of data. This opens the possibility to compare biodiversity data, physico-chemical data, sedimentological data and historical data.Another database at MUMM, the real-time data acquisition system ‘ODAS’ stores the physical and chemical parameters measured onboard of the research vessel RV Belgica since 1984. The along -track data are published online shortly after the end of the measurement campaign together with all other information like the campaign reports, cruise tracks, … This is a valuable source of basic information for the scientists

Current-driven microwave oscillations in current perpendicular-to-plane spin-valve nanopillars

We study the current and temperature dependences of the microwave voltage emission of spin-valve nanopillars subjected to an in-plane magnetic field and a perpendicular-to-plane current. Despite the complex multilayer geometry, clear microwave emission is shown to be possible and spectral lines as narrow as 3.8 MHz (at 150 K) are observed.Comment: To appear in Applied Physics Letter

Revealing species communities in a spatial and temporal overlap

Storing physical and chemical values, optical spectra and sediment granulometry is already a cumbersome task; dealing with biological data even falls into a different category. Biologists tend to focus their attention to species of their interest while other specimens in the same sample are often underestimated. Meanwhile taxonomists are continuously revising the taxonomy resulting in a complete new set of relations between these taxa. Keeping track with both and meanwhile having a dataset up to date seems endless. At the Belgian Marine Data Centre we tried to think outside the box and came up with a solution to content both biologists and data managers. The last thing we aimed at is to create another web index to refer species, therefore we hooked up with the existing web based referencing systems. The need to get data about different food webs in a spatial and temporal overlap is answered by our hierarchical storage of taxa which allows selecting a predator at species level and at the same time selecting different prey species at lower taxonomic levels. As these species, and also the scientists, usually are not confined into ‘latitude longitude squares’ we elaborated the spatial selection tool which defines user specific polygons to base the selection of data upon. We will briefly present the structure of our relational database but specific attention will go out to the taxonomic and spatial parts. Incentives and discomforts to organize the data in this way, and our current web interface, will be demonstrated

Thermally nucleated magnetic reversal in CoFeB/MgO nanodots

Power consumption is the main limitation in the development of new high performance random access memory for portable electronic devices. Magnetic RAM (MRAM) with CoFeB/MgO based magnetic tunnel junctions (MTJs) is a promising candidate for reducing the power consumption given its non-volatile nature while achieving high performance. The dynamic properties and switching mechanisms of MTJs are critical to understanding device operation and to enable scaling of devices below 30 nm in diameter. Here we show that the magnetic reversal mechanism is incoherent and that the switching is thermally nucleated at device operating temperatures. Moreover, we find an intrinsic thermal switching field distribution arising on the sub-nanosecond time-scale even in the absence of size and anisotropy distributions or material defects. These features represent the characteristic signature of the dynamic properties in MTJs and give an intrinsic limit to reversal reliability in small magnetic nanodevices

Sub-ns spin-transfer switching: compared benefits of free layer biasing and pinned layer biasing

We analyze the statistical distribution of switching durations in spin-transfer switching induced by current steps, and discuss biasing strategies to enhance the reproducibility of switching durations. We use a macrospin approximation and model the effect of finite temperature as a Boltzmann distribution of initial magnetization states (adiabatic limit). We compare three model spin-valves: a spin-valve with a free layer whose easy axis is parallel to the pinned layer magnetization (standard geometry), a pinned layer with magnetization tilted with respect to the free layer easy axis (pinned layer biasing), and a free layer whose magnetization is pulled away from easy axis by a hard axis bias (free layer biasing). In the conventional geometry, the switching durations follow a broad regular distribution, with an extended long tail comprising very long switching events. For the two biasing strategies, the switching durations follow a multiply-stepped distribution, reflecting the precessional nature of the switching, and the statistical number of precession cycles needed for reversal. We derive analytical criteria to avoid switching events lasting much longer than the average switching duration, in order to achieve the highest reproducibilities. Depending on the current amplitude and the biasing strength, the width of the switching time distribution can be substantially reduced, the best reproducibility being achieved for free layer biasing at overdrive current of a few times unity.Comment: submitted to Phys Rev.