An Experimental Digital Library Platform - A Demonstrator Prototype for the DigLib Project at SICS

Within the framework of the Digital Library project at SICS, this thesis describes the implementation of a demonstrator prototype of a digital library (DigLib); an experimental platform integrating several functions in one common interface. It includes descriptions of the structure and formats of the digital library collection, the tailoring of the search engine Dienst, the construction of a keyword extraction tool, and the design and development of the interface. The platform was realised through sicsDAIS, an agent interaction and presentation system, and is to be used for testing and evaluating various tools for information seeking. The platform supports various user interaction strategies by providing: search in bibliographic records (Dienst); an index of keywords (the Keyword Extraction Function (KEF)); and browsing through the hierarchical structure of the collection. KEF was developed for this thesis work, and extracts and presents keywords from Swedish documents. Although based on a comparatively simple algorithm, KEF contributes by supplying a long-felt want in the area of Information Retrieval. Evaluations of the tasks and the interface still remain to be done, but the digital library is very much up and running. By implementing the platform through sicsDAIS, DigLib can deploy additional tools and search engines without interfering with already running modules. If wanted, agents providing other services than SICS can supply, can be plugged in

The influence of macrofaunal burrow spacing and diffusive scaling on sedimentary nitrification and denitrification: An experimental simulation and model approach

The influence of burrow spacing on nitrification and denitrification was simulated experimentally using sediment plugs of different thicknesses immersed in aerated seawater reservoirs. Different plug thicknesses mimic different distances between oxygenated burrow centers and produce similar changes in aerobic–anaerobic reaction balances as a function of diffusive transport scaling. The thicknesses used were roughly equivalent to transport scales (interburrow spacing) that could be produced by burrow abundances of ~400 to 50,000 m-2, depending on burrow lumen radii (e.g., 0.05–1 cm). Following the exposure of anoxic sediment plugs to aerated water, an efficient aerobic nitrification zone was established within the first ~2–3 millimeters of sediment. At pseudo-steady state, the thinnest plug (2 mm) simulating highest burrow density, was entirely oxic and the denitrification rate nil. Denitrification was stimulated in anoxic regions of the thicker plugs (5, 10, and 20 mm) compared to the initial value in experimental sediment. Maximum nitrification rates and the highest denitrification/nitrification ratio between oxic nitrification and adjacent denitrification zones occurred for the intermediate plug thickness of 5 mm. Of the oxic/anoxic composites, the thickest plug showed the least efficient coupling between nitrification/denitrification zones (lowest denitrification/nitrification ratio). Both the thickness of the oxic layer and the total net remineralization of dissolved inorganic N varied inversely with plug thickness. A set of diffusion–reaction models was formulated assuming a range of possible nitrification kinetic functions. All model forms predicted optimal nitrification–denitrification and ammonification–denitrification coupling with relative oxic–anoxic zonation scales comparable to intermediate plug thicknesses (5–6 mm). However, none of the commonly assumed kinetic forms for nitrification could produce the observed NO-3 profiles in detail, implying that natural sediment populations of nitrifiers may be less sensitive to O2 than laboratory strains. Our experimental and model results clearly show that rates of N remineralization and the balance between stimulation/inhibition of denitrification are highly dependent on sedimentary biogenic structure and the particular geometries of irrigated burrow distributions

Coupled anoxic nitrification/manganese reduction in marine sediments

Pore water and solid phase distributions of oxygen, manganese, and nitrogen from hemipelagic and shelf sediments sometimes indicate a close coupling between the manganese and nitrogen redox cycles. Reaction coupling must be sustained in part by biological reworking of Mn-oxide-rich surface sediments into underlying anoxic zones. Surface sediment from Long Island Sound (USA) was used in laboratory experiments to simulate such intermittent natural mixing processes and subsequent reaction evolution. Mixed sediment was incubated anoxically under either diffusively open (plugs) or closed conditions (jars). In closed anoxic incubations, pore water NO3 2 increased regularly to a maximum (up to 17 mM) after one to several days, and was subsequently depleted. Mn21 was produced simultaneously with NO3 2. NO2 2 was also clearly produced and subsequently reduced, with a formation-depletion pattern consistent with coupled nitrificationdenitrification in the anoxic sediment. Manipulative additions of Mn-oxides (5–10 mmol g21 net) demonstrated that net anoxic NO3 2 production correlated directly with initial Mn-oxide content. During initial net NO3 2 production there was no evidence for SO4 22 reduction. A direct correlation was also observed between anoxic nitrification rates and estimated sulfate reduction rates; the larger nitrification rates, the larger the eventual net sulfate reduction rates. Diffusively-open incubations using sediment plugs of four different thicknesses (2, 5, 10 and 20 mm) exposed to anoxic overlying water, also showed net production of pore water NO3 2 (;15–20 mM) despite the absence of NO3 2 in the overlying water for at least five days. In general, higher nitrate concentrations were maintained in the open relative to the closed incubations, due most likely to lower concentrations of dissolved reductants for NO3 2 in the open system. These experiments imply simultaneous coupling between the benthic nitrogen, manganese, and sulfur redox cycles, involving anoxic nitrification and sulfide oxidation to SO4 22. Anoxic nitrate production during Mn reduction indicates that nitrification and denitrification can occur simultaneously in subsurface sediments, without vertical stratification. The existence of anoxic nitrification implies new reaction pathways capable of increasing coupled sedimentary nitrificationdenitrification, particularly in bioturbated or physically mixed deposits

Comparison between the Nereis diversicolor and Nereis virens marine worms in the transformation of ingested hydrocarbons

A feeding experiment was conducted on the marine worm Nereis diversicolor to compare the fate of a hydrocarbon mixture during the gut passage in this species with the hydrocarbon breakdown process demonstrated for Nereis virens. Hydrocarbon dissolution/solubilization processes in the gut of N. diversicolor were found to have similar qualitative and quantitative importance in the hydrocarbon transformation as those observed in N. virens

2-D optical quantification of particle reworking activities in marine surface sediments

Particle and solute transport by faunal activities may significantly influence rates and pathways of organic matter mineralization during early diagenesis in surface sediments. One of the most frequently utilized techniques to quantify benthic biological reworking activities involves the calculation of a biodiffusion coefficient (Db) estimated from model predictions of 1-D tracer distribution patterns. This technique is labor-intensive and time-demanding. Furthermore, it is normally used for measurements over several days and averages overall transport mechanisms from 3-D to 1-D on a cm scale. In the frame of this work, we developed a new technique based on the nondestructive screening of fluorescent particles (luminophores) using optical discrimination and CCD camera detection of fluorescence (2-D). At a site characterized by a dense population of the brittle star Amphiura filiformis and a high biodiffusion coefficient (obtained from 1-D distributions; Db=35.5±3.7 cm−2 year−1; n=3), the optical reworking coefficient (ORC), estimated from the 2-D luminophore distribution patterns, was calculated (ORC=27.4±9.1 View the MathML source cm−2 h−1; n=24). A nondestructive 2-D approach to quantify particle reworking may provide a powerful and complementary tool to further understand particle transport by the benthic fauna in surface sediments. The optical technique for 2-D detection of luminophores is relatively fast and easy to perform, with the ability to detect small scale (mm) particle movements on a time resolution of minutes or less

Consolidation through resourcing in last-mile logistics

This paper assesses how various ways of organizing last-mile logistics impact resource utilization, and, in turn, opportunities for consolidating goods. The paper combines a conceptualization of resourcing and consolidation derived from the literature with an analysis of contemporary last-mile logistics options in the Swedish retail market. Based on the analysis of three forms of last-mile logistics - consumer logistics, retailer logistics, and hybrid logistics - the paper discusses how resourcing for fixed, mobile, and coordination resources can enable consolidation in terms of time, place, and form. Drawing from the Swedish context, the paper calls for additional research combining country-specific studies while examining similarities and differences in last-mile logistics, particularly concerning factors that enable or hinder consolidation as well as how such potentials are realized in practice. Although consolidation clearly appears in the rich literature on last-mile logistics, this paper focuses on how consolidation can be achieved through resourcing and offers additional insights into current frameworks for last-mile logistics in retailing

Nitrogen removal in marine environments: recent findings and future research challenges

Respiratory reduction of nitrate (denitrification) is recognized as the most important process converting biologically available (fixed) nitrogen to N2. In current N cycle models, a major proportion of global marine denitrification (50–70%) is assumed to take place on the sea floor, particularly in organic rich continental margin sediments. Recent observations indicate that present conceptual views of denitrification and pathways of nitrate reduction and N2 formation are incomplete. Alternative N cycle pathways, particularly in sediments, include anaerobic ammonium oxidation to nitrite, nitrate and N2 by Mn-oxides, and anaerobic ammonium oxidation coupled to nitrite reduction and subsequent N2 mobilization. The discovery of new links and feedback mechanisms between the redox cycles of, e.g., C, N, S, Mn and Fe casts doubt on the present general understanding of the global N cycle. Recent models of the oceanic N budget indicate that total inputs are significantly smaller than estimated fixed N removal. The occurrence of alternative N reaction pathways further exacerbates the apparent imbalance as they introduce additional routes of N removal. In this contribution, we give a brief historical background of the conceptual understanding of N cycling in marine ecosystems, emphasizing pathways of aerobic and anaerobic N mineralization in marine sediments, and the implications of recently recognized metabolic pathways for N removal in marine environments

Transportation as a loosely coupled system: a fundamental challenge for sustainable freight transportation

In view of the pressing need to reduce the negative environmental impact of freight transportation we argue that it is essential to take account of the organization of the freight transportation system when considering how to address various individual activities and parts of the system. To support a transition to a more sustainable freight transportation system this paper examines the way in which different parts of the system interact and the way this can impact the scope for profound change. Taking loosely coupled systems (Weick, 1976) as a starting point, we scrutinize the couplings within and between three system layers of the freight transportation system: the supply chain layer, the transportation layer, and the infrastructure layer. In addition, we address two interfaces connecting these layers: the market for transportation services, and the traffic using the infrastructure. We find that tight couplings dominate in the supply chain and infrastructure layers and that these couplings depend on loose couplings in the transportation layer and the two interfaces. The pattern of couplings identified in the freight transportation system can explain several positive outcomes, such as flexibility and efficiency. But there are also major negative aspects of the loosely coupled nature of the system that create resistance to change and present a barrier in the drive for increased sustainability. The paper concludes that the identified couplings and system features have important implications for policies aiming to change the freight transportation system in ways that lead to significant reduction in the reliance on oil