The FAST module: an add-on unit for driving commercial scanning probe microscopes at video rate and beyond

We present the design and the performance of the FAST (Fast Acquisition of SPM Timeseries) module, an add-on instrument that can drive commercial scanning probe microscopes (SPM) at and beyond video rate image frequencies. In the design of this module, we adopted and integrated several technical solutions previously proposed by different groups in order to overcome the problems encountered when driving SPMs at high scanning frequencies. The fast probe motion control and signal acquisition are implemented in a way that is totally transparent to the existing control electronics, allowing the user to switch immediately and seamlessly to the fast scanning mode when imaging in the conventional slow mode. The unit provides a completely non-invasive, fast scanning upgrade to common SPM instruments that are not specifically designed for high speed scanning. To test its performance, we used this module to drive a commercial scanning tunneling microscope (STM) system in a quasi-constant height mode to frame rates of 100 Hz and above, demonstrating extremely stable and high resolution imaging capabilities. The module is extremely versatile and its application is not limited to STM setups but can, in principle, be generalized to any scanning probe instrument.     

Macrobenthos community structural changes off Cesenatico coast (Emilia Romagna, Northern Adriatic), a six-year monitoring programme

Soft bottom macrobenthos at a station located off Cesenatico (Emilia Romagna, Northern Adriatic Sea) was investigated seasonally for six years from July 1996 to July 2002. Species composition and abundance of the community have been studied in relation to fluctuation in the water environment parameters, sediment texture patterns and mucilage, that occurred mainly in the water column at the study site. Three major Po river flow peaks occurred in November 1996, October 2000 and May 2002; after these events the community was reduced to minimum abundance values (total density<2000 individuals m(-2)). In the period between the first two episodes the river discharge remained rather low and conditions of increased salinity, lower nutrients and chl a and good oxygen saturation were experienced. The fossorial Crustacean Ampelisca diadema became dominant in the community between the first two river flow events, reaching maximum density of 10,200 individuals m(-2) and substituting the bivalve Corbula gibba, indicator of sediment instability. Species richness increased in the same period. The role of Ampelisca as a facilitator in structuring the community is discussed. Corbula gibba never recovered to initial densities, apart from an abundance peak that occurred in the summer of 2000. Faunal composition seemed to evolve slowly towards a higher degree of structural complexity (positive trend in diversity and evenness index). In the study site near-bottom mucilage events occurred in the summers of 1997, 1998, 2002; they appeared uncorrelated with the observed changes in the community structure. Multivariate analysis of community structure (MDS, ANOSIM) illustrates that community changes in this station are driven mainly by hydrographical conditions influencing sediment texture patterns and trophic resources for the benthos.     

Natural and NH<Subscript>4</Subscript><Superscript>+</Superscript>-enriched zeolitite amendment effects on nitrate leaching from a reclaimed agricultural soil (Ferrara Province,Italy)

In this paper we report an overview of the main outcomes of a 3-years experimental cultivation carried out in an Italian reclaimed agricultural field amended with different types of zeolitites (rock containing > 50% of zeolites), under cereals cultivation (Sorghum vulgare Pers, Zea mays and Triticum durum). The aim of the experiment was to exploit the properties of zeolite-rich volcanic rocks (zeolitites) for reducing the excessively high NO₃^? content in the soil and in waters flowing out the sub-surface drainage system of the field and flushing into the surface water system, reducing concomitantly also chemical fertilization application rates (up to 50%). Zeolitites were tested both in their natural state and in a NH₄⁺-enriched form, obtained through an enrichment process with NH₄⁺-rich zoo-technical effluents (pig slurry). NO₃^? content in soils and in waters discharged through SSDS were periodically monitored during the experimentation and crop yield quantified. Results showed that, for three consecutive cultivation cycles, the overall NO₃^? concentrations in water extracts was reduced by 45% in the zeolitite treated soils, while in SSDS waters the reduction reached the 64%. Notwithstanding the lower N input from chemical fertilizers, crop yield was not negatively affected in the zeolitite amended soils with respect to the control. Zeolitite addition increased thus soil NH₄⁺ retention and probably influenced several pathways of N losses, allowing a better fertilizer use efficiency by plants and a reduction of the overall NO₃^? concentrations in the surface waters.