. The commonly cited parameter Ztd (frequency dependence of susceptibility) reaches 30% at room temperature (RT) for one sample with a blocking temperatures just below RT, while Ztd = 0 at RT for a superparamagnetic sample with smaller grains. These results thus exemplify that Zfd is not limited to 15%, as a number of studies suggest, and that Zfd = 0 must not be taken to imply the absence of superparamagnetic grains.

SUMMARYInitially, Grid technologies were principally associated with supercomputer centres and large-scale scientific applications in physics and astronomy. They are now increasingly seen as being relevant to many areas of e-Science and e-Business. The emergence of the Open Grid Services Architecture (OGSA), to complement the ongoing activity on Web Services standards, promises to provide a service-based platform that can meet the needs of both business and scientific applications. Early Grid applications focused principally on the storage, replication and movement of file-based data. Now the need for the full integration of database technologies with Grid middleware is widely recognized. Not only do many Grid applications already use databases for managing metadata, but increasingly many are associated with large databases of domain-specific information (e.g. biological or astronomical data). This paper describes the design and implementation of OGSA-DAI, a service-based architecture for database access over the Grid. The approach involves the design of Grid Data Services that allow consumers to discover the properties of structured data stores and to access their contents. The initial focus has been on support for access to Relational and XML data, but the overall architecture has been designed to be extensible to accommodate different storage paradigms. The paper describes and motivates the design decisions that have been taken, and illustrates how the approach supports a range of application scenarios. The OGSA-DAI software is freely available from http://www.ogsadai.org.uk.

Abstract. Stable single-domain (SSD) grains were mixed separately with superparamagnetic, pseudosingle-domain, and multidomain (MD) magnetite/maghemite particles in order to test the linearity of various magnetic parameters as a function of mixing ratio. Hysteresis loops, isothermal remanent magnetization acquisition curves, DC demagnetization curves, and low-temperature thermal demagnetization curves were measured on the mixtures. The experiments demonstrate that magnetization parameters are linearly dependent on the mixing ratio, while more complex parameters, e.g., coercivities, do not behave linearly as a function of mixing ratio. Armed with linearity, we apply a mathematical technique which, given a database of type curves, uses singular value decomposition to solve for the various concentrations of the magnetic phases in the mixture and a Monte Carlo simulation to determine the error in the inversion. We then test the technique on numerical mixtures, on the physical mixtures, and on a small set of natural samples from Lake Pepin, Minnesota. Finally, the magnetic behavior of the mixture of MD and SSD grains is considered, and two more mixture strains of MD and SSD grains (numerically produced) are considered to facilitate this discussion.

We have conducted a new set of rock magnetic experiments on samples of remagnetized Paleozoic carbonates of eastern North America. These experiments were designed to investigate the origin of the unusual hysteresis behavior of these rocks, by evaluating (1) the importance of ferrimagnetic pyrrhotite as a remanence carrier, and (2) the sources of low-field susceptibility. Low-temperature measurements of saturation isothermal remanent magnetization (SIRM) indicate that the pyrrhotite magnetic transition at 32 K is absent in the Trenton and Onondaga limestones of New 'York. This transition is observed but poorly expressed in the Knox Group of east Tennessee: room-temperaeare SIRMs, cooled to 10 K in zero field, lose a small fraction of their intensity between 30 and 35 K. Samples from all three formations show a broad peak in IRM intensity at about 200 K, which is typical of pyrrhotite. In the Trenton and Onondaga samples, the ferrimagnetic component of low-field susceptibility is significantly larger than the ratio Mrs/Hcr, and is thus probably due dominantly to magnetite; in some of the Knox samples the reverse is true, suggesting an important pyrrhotite contribution. For all of the samples, the ferrimagnetic susceptibility, normalized by the saturation magnetization, is anomalously high, about a factor of 5 or 10 higher than the typical value for magnetite. We believe that this indicates a very substantial contribution from superparamagnetic particles. Strong frequency dependence of susceptibility and very high ratios of anhysteretic to saturation remanence confirm the importance of ultrafine particles, spanning the superparamagnetic--single-domain boundary.All three of these chemically remagnetized carbonates units exhibit the following properties, which have not previously been found together for any rock or synthetic analog, and which therefore appear to constitute a diagnostic set of rockmagnetic criteria for recognizing chemically-remagnetized rocks: Mrs/M s --0.89 (Hcr/Hc)-0'6; kjM s --50 gm/A; ARM/SIRM --20%; ka/(Mrs/Hcr) --50. of saturation remanence to saturation magnetization (Mrs/Ms) and reinanent to bulk coercivity (Hcr/Hc) [Jackson, 1990a]. In this study we investigate a possible alternative explanation for the unusually high values of these two hysteresis ratios, namely an unrecognized and significant contribution from ferrimagnetic pyrrhotite. Although it is clear that pyrrhotite is not responsible for the characteristic late Paleozoic natural remanent magnetization (NRM) of these rocks (which unblocks at temperatures above the Curie temperature of pyrrhotite, about 325øC), there are several reasons to suspect that pyrrhotite may be partially responsible for their unusual bulk magnetic properties. First, Freeman [1986] reported abundant ferrimagnetic pyrrhotite in magnetic extracts from the Helderberg limestone, despite the fact that Scotese et al. [ 1982] saw evidence of only pure magnetite in their thermomagnetic analysis of Helderberg extracts. Second, the coexistence of pyrrhotite with magnetit...

OpenStreetMap (OSM) data are widely used but their reliability is still variable. Many contributors to OSM have not been trained in geography or surveying and consequently their contributions, including geometry and attribute data inserts, deletions, and updates, can be inaccurate, incomplete, inconsistent, or vague. There are some mechanisms and applications dedicated to discovering bugs and errors in OSM data. Such systems can remove errors through user-checks and applying predefined rules but they need an extra control process to check the real-world validity of suspected errors and bugs. This paper focuses on finding bugs and errors based on patterns and rules extracted from the tracking data of users. The underlying idea is that certain characteristics of user trajectories are directly linked to the type of feature. Using such rules, some sets of potential bugs and errors can be identified and stored for further investigations.