bluuebunny/crossref_metadata_2025_split huggingface dataset:
Teaching functional programming to first-year students
Authors: Joosten Stef , Van Den Berg Klaas , Van Der Hoeven Gerrit 
Published: November 2008

AbstractIn the period 1986–1991, experiments have been carried out with an introductory course in computer programming, based on functional programming. Due to thorough educational design and evaluation, a successful course has been developed. This has led to a revision of the computer programming education in the first year of the computer science curriculum at the University of Twente.This article describes the approach, the aim of the computer programming course, the outline and subject matter of the course, and the evaluation. Educational research has been done to assess the quality of the course.
Heap profiling of lazy functional programs
Authors: Runciman Colin , Wakeling David 
Published: November 2008

AbstractWe describe the design, implementation and use of a new kind of profiling tool that yields valuable information about the memory use of lazy functional programs. The tool has two parts: a modified functional language implementation which generates profiling information during the execution of programs, and a separate program which converts this information to graphical form. With the aid of profile graphs, one can make alterations to a functional program which dramatically reduce its space consumption. We demonstrate this in the case of a genuine example - the first to which the tool was applied - for which the results are strikingly successful.
Deciding type isomorphisms in a type-assignment framework
Authors: Di Cosmo Roberto 
Published: November 2008

AbstractThis paper provides a formal treatment of isomorphic types for languages equipped with an ML style polymorphic type inference mechanism. The results obtained make less justified the commonplace feeling that (the core of) ML is a subset of second order λ-calculus: we can provide an isomorphism of types that holds in the core ML language, but not in second order λ-calculus. This new isomorphism allows to provide a complete (and decidable) axiomatization of all the types isomorphic in ML style languages, a relevant issue for thetype as specificationsparadigm in library searches. This work is a very extended version of Di Cosmo (1992): we provide both a thorough theoretical treatment of the topic and describe a practical implementation of a library search system so that the paper can be used as a reference both by those interested in the formal theory of ML style languages, and by those simply concerned with implementation issues. The new isomorphism can also be used to extend the usual ML type-inference algorithm, as suggested by Di Cosmo (1992). Building on that proposal, we introduce a better type-inference algorithm that behaves well in the presence of non-functional primitives like references and exceptions. The algorithm described here has been implemented easily as a variation to the Caml-Light 0.4 system.
On the equivalence between CMC and TIM
Authors: Lins Rafael D. , Thompson Simon J. , Jones Simon Peyton 
Published: November 2008

AbstractIn this paper we present an equivalence between TIM, a machine developed to implement non-strict functional programming languages, and the set of Categorical Multi-Combinators, a rewriting system developed with similar aims. These two models of computation at first appear to be quite different, but we show a direct equivalence between them, thereby adding some new structure to the ‘design-space’ of abstract machines for non-strict languages.
Total unfolding: theory and applications
Authors: Lisper Björn 
Published: November 2008

AbstractUnfolding is a common technique in program transformations. Here, we present a computation model where unfolding is a simple generalisation of the usual concept of evaluation. The model is a variant of the well-known full substitution evaluation rule for recursive programs. The evaluation mechanism involved is symbolic substitution of function definitions followed by simplification. Simplification is expressed as a confluent rewrite strategy which uses three kinds of reductions: β-reduction, non-erasing reduction, and erasing reduction. Non-erasing reductions include simplification of constant subexpressions. Erasing reductions formalize the behaviour of nonstrict operations. In this computation model, we prove a termination theorem of symbolic unfolding relative to more instantiated calls. A possible application of the model is a technique called total unfolding, where a partially instantiated function call is unfolded until no more calls exist. Under certain conditions the result will be a first order term: such terms correspond to basic blocks in imperative programs and can be efficiently implemented by scheduling techniques. Possible applications are hardware synthesis, and code generation for parallel machines.
Generic functional programming with types and relations
Authors: Bird Richard , De Moor Oege , Hoogendijk Paul 
Published: November 2008

AbstractAgenericfunctional program is one which is parameterised by datatype. By installing specific choices, for example lists or trees, different programs are obtained that are, nevertheless, abstractly the same. The purpose of this paper is to explore the possibility of deriving generic programs. Part of the theory of lists that deals with segments is recast as a theory about ‘segments’ in a wide class of datatypes, and then used to pose and solve a generic version of a well-known problem.
Sparse matrix representations in a functional language
Authors: Grant P. W. , Sharp J. A. , Webster M. F. , Zhang X. 
Published: November 2008

AbstractThis paper investigates several sparse matrix representation schemes and associated algorithms in Haskell for solving linear systems of equations arising from solving realistic computational fluid dynamics problems using a finite element algorithm. This work complements that of Wainwright and Sexton (1992) in that a Choleski direct solver (with an emphasis on its forward/backward substitution steps) is examined. Experimental evidence comparing time and space efficiency of these matrix representation schemes is reported, together with associated forward/backward substitution implementations. Our results are in general agreement with Wainwright and Sexton's.
Functional Pearl
Authors: Hutton Graham , Meijer Erik 
Published: November 2008

AbstractA representation changer is a function that converts a concrete representation of an abstract value into a different concrete representation of that value. Many useful functions can be recognised as representation changers; examples include compilers and arithmetic functions such as addition and multiplication. Functions that can be specified as the right inverse of other functions are special cases of representation changers. In recent years, a number of authors have used a relational calculus to derive representation changers from their specifications. In this paper, we show that the generality of relations is not essential, and representation changers can be derived within the more basic setting of functional programming. We illustrate our point by deriving a carry-save adder and a base-converter, two functions which have previously been derived relationally.
Isomers of the dodecylbenzene in marine sediments from the Todos os Santos Bay, Bahia, Brazil
Authors: Souza Santos V.L.C. , Raymundo C.C. , Tavares T. 
Published: November 2008

Abstract
Linear alkylbenzenes(LAB) have been investigated in surficial sediments from the Todos os Santos Bay, the largest on the Brazilian coast. The presence of these compounds in the environment has been related to sewage pollution because they are manufactured for the preparation of surfactants used in detergent formulations. They are usually present as an homologous series of compounds with a side chain varying from 10 to 14 carbon atoms attached to a benzene ring.
The sediment samples were collected from the intertidal area of 13 stations situated in the bay. The dried samples were solvent extracted, and after clean up and fractionation of the lipid extract by column chromatography the fraction containing the LABs were separated and identified by high resolution gas chromatography and gas chromatography coupled to mass spectrometry. Surprisingly, only the isomers of dodecylbenzene were found. The compounds were present in all stations and the concentrations ranged from 0.063 to 50.2 mg g−1 total organic carbon. These values were considered very high compared to those cited in the literature.
It is not yet clear if the origin of these compounds in the sediments is related to detergent formulations. However, the results suggest that they possibly originated from a point source and dispersed in the bay probably due to water movements in the area.
Brazilian mangroves
Authors: Schaeffer-Novelli Y. , Cintrón-Molero G. , Soares M.L.G. , De-Rosa T. 
Published: November 2008

Abstract
Of Brazil’s 7408 km of coastline 6786 km contain mangrove forests, covering some 25,000 km2. Only one coastal state, Rio Grande do Sul, lacks mangrove coverage. Mangroves occur from the border with French Guiana, just above the Equator (04°30′N) to well beyond the Tropic of Capricorn, reaching 28°30′S, near Laguna (Santa Catarina State).
Because the term mangrove may be applied to various levels of observation, specifying the proper spacio-temporal scale is important to describe system behavior. In this paper we describe a nested hierarchy of organization levels constituted of patches, stands, settings, coastal segments and large marine ecosystems. Each of these describes an organization that has evolved to facilitate energy dissipation at its relevant scale, and can be related to a geographic unit.
We expect that the framework presented here will be useful for the study of mangrove ecosystem health, assessment of ecosystem pathology, and the development of models for the management and conservation of this resource.
The large lake ecosystems of northern Canada
Authors: Evans M.S. 
Published: November 2008

Abstract
The Great Lakes of northern Canada are relatively understudied ecosystems in comparison to the better-investigated Laurentian Great Lakes. This chain of lakes extends north from Lake Winnipeg (a shallow prairie lake) to Wollaston Lake and Lake Athabasca (moderately deep arboreal lakes) to Great Slave Lake (a deep subarctic lake) to Great Bear Lake (a deep lake located in the Arctic Circle). Many of these lakes have experienced minor localized anthropogenic impacts. Impacts include mining and fishing in the north and agricultural and urban impacts in the south. While most of these lakes are located in the relatively undeveloped regions of Canada, the northward migration of natural resource-based industries such as forestry, mining, agriculture and oil and gas operations may potentially affect their ecosystem health. Research programs are required to better understand the natural features of these ecosystems to further protect them from anthropogenically driven change. Long-term monitoring programs are also required to protect fish, water quality and other ecosystem features. An emerging problem is meeting northern community concerns with environmental protection while providing the economic base for an increasingly modern lifestyle.
Trace element bioavailability in Lake Baikal
Authors: Grosheva E.I. , Voronskaya G.N. , Pastukhove M.V. 
Published: November 2008

Abstract
Nuclear physical methods of analysis were used for the determination of some trace elements in the ecosystem of Lake Baikal (water, bottom sediments and the water organisms, phytoplankton, zooplankton, zoobenthos and fish). Our observations suggest that the health status of the Lake Baikal is good and bioavailability of toxic elements is very low.
A preliminary bioassessment of Lake Baikal sediment toxicity in the vicinity of a pulp and paper mill
Authors: Munawar M. , Munawar I.F. , Sergeant D. , Wenghofer C. 
Published: November 2008

Abstract
The chemical and toxicological information given in this short communication is based on two sediment samples of limited amount taken from Lake Baikal. The samples received detailed chemical assessment since information about Lake Baikal sediments is scarce. The sediments were tested for sediment bound toxicity by liquid phase (Microtox) and solid phase (Hyalella) assays. The organic and inorganic chemical analyses were carried out with current technology followed in Canada, which may be useful for comparisons with other aquatic ecosystems. A wide range of organic compounds such as organochlorine pesticides, chlorinated diphenyl ethers, polychlorinated biphenyls, chlorinated dibenzo-p-dioxins and furans, coplanar polychlorinated biphenyls and polyaromatic hydrocarbons comprised the suite of compounds analysed for environmental levels. Generally, the full scan for high-resolution gas chromatography/high-resolution mass spectrometry electron impact analysis showed somewhat similar profiles for both the near-shore and off-shore stations. However, organic analysis indicated the near-shore station to be relatively more contaminated than the off-shore station. These chemical results were not supported by the Microtox and Hyalella bioassay experiments. The bioassays suggested that the near-shore and off-shore sediment samples were non-toxic. The necessity of performing both chemical as well as biological evaluations with a battery of assays is once again emphasized for ecosystem health assessment.
Biological and chemical monitoring after pilot remediations in the delta of the rivers Rhine and Meuse
Authors: den Besten P.J. , Postma J.F. , Wegener J.W.M. , Keidel H. , Klink A. , Mol J. , van de Guchte C. 
Published: November 2008

Abstract
Two pilot projects were carried out to investigate the effects of sediment remediation. One project was situated in a groyne section of the Nieuwe Merwede, a watercourse in the Rhine delta. The second was situated in a creek named Spijkerboor, which receives water from the river Meuse. For both sites it was concluded earlier that sediment pollution posed a high risk to the ecosystem. The remediations consisted of partial excavation of the contaminated sediments, followed by application of a clean layer of sandy material on top of the remaining contaminated sediment. Before and at various times after the remediation, the following investigations were carried out: physical–chemical analyses of sediment, benthic community structure observations, bioaccumulation measurements and sediment bioassays. After the remediation, a new silty sediment top layer was formed with lower contaminant levels exhibiting a lower toxicity. In the remediated site in the Nieuwe Merwede, chironomids, oligochaetes and nematodes reappeared within 3–7 months at normal densities, while in the Spijkerboor recolonization by chironomids and nematodes proceeded more slowly. After 2 years, in both the remediated sites chironomids and nematodes were present in densities much higher than before the remediation. Bivalves showed a low recolonization rate in both sites. In non-remediated, polluted reference sites also a lower sediment toxicity and a nearly comparable recovery of the benthic community was observed, probably the result of natural sedimentation of material with lower contaminant levels. Because of the natural improvement of sediment quality, the net effects of remediation were negligible in the Spijkboor. For the Nieuwe Merwede, after 2 years still lower contaminant levels were observed in the remediated site compared to the non-remediated site, resulting in lower bioaccumulation in oligochaetes. However, the contaminant levels in sediment and biota still do not meet all environmental quality objectives. Based on the outcame of this study it is recommended that the priority for remedial action is made dependent on the rate of natural covering with sediments from the rivers Rhine and Meuse.
Biomonitoring for effective management of wastewater discharges and the health of the river environment
Authors: Dickens C.W.S. , Graham P.M. 
Published: November 2008

Abstract
The management of wastewater effluents in South Africa has to date been based on physico-chemical standards although recently the assimilative capacity of the receiving stream has been included but not widely implemented. Very few assessments of the success of these management practices in protecting the downstream aquatic environment have been done. Bioassessments using benthic macro invertebrates were conducted up and down stream of a number of wastewater works to measure the degree of impact that the works were having on the stream ecosystems. A significant deterioration in the benthic invertebrate fauna downstream of most of the wastewater works was observed. This was particularly noticeable where the receiving stream was of good quality while there was little change in poor quality receiving streams. This was confirmed using ordination techniques. The ordination diagrams displayed how community composition varied with important environmental variables although some of these may be surrogates for other unmeasured variables. It was revealed that river flow and the dilution of the effluent were the most important of the measured variables explaining the variability in the biota. Escherichia coli and soluble phosphorus were also shown to be important with suspended solids also significant. Most of the wastewater works, in the month prior to the biological investigation, had complied with their permit requirements. The exceptions, found on infrequent occasions at different works, were soluble phosphorus, chlorine, E. coli and conductivity. One permit requirement that was consistently ignored was a statement forming part of the effluent standards permit system which states that the effluent should not contain constituents that are poisonous or injurious to animal (including aquatic) life. No systems for monitoring this criterion were in place. Despite the general compliance with regulations governing wastewater treatment a lack of adequate effluent dilution appeared to be the major cause of degradation of the downstream biota. These wastewater works are found in a region that does not have an abundant supply of water for dilution so treatment of the effluent to a condition that is not injurious to aquatic life becomes a necessity. Thus it appears that the physico-chemical standards used to characterise and manage wastewater treatment in South Africa are inadequate to protect the downstream environment in the vicinity below many wastewater works.
The role of physical biotopes in determining the conservation status and flow requirements of British rivers
Authors: Padmore C.L. 
Published: November 2008

Abstract
This paper examines the practical use of physical biotopes as the basic component of instream physical habitat. These are identified by dominant flow type as a particular combination of substrate and hydraulic parameters will have a characteristic surface flow type. Eleven rivers representing a range of geomorphological features and physical biotopes were selected, and depth, velocity, and substrate data were collected at metre intervals in subjectively-spaced transects. Flow type was recorded at each sample “cell” and transects classified on the basis of dominant flow type. Combined hydraulic indices were calculated in order to characterise more completely a particular biotope and to facilitate comparisons among different discharges and sites.
The subjective classification of flow types was tested statistically by discriminant analysis and units were shown to be hydraulically discrete in terms of Froude number and other combined hydraulic indices. Identification of physical biotopes by flow types has been incorporated into the Environment Agency’s (formerly National Rivers Authority) River Habitat Survey (RHS). The RHS is based on 500 m reaches selected randomly within a stratified selection from a national grid, to characterise the physical features of rivers in England and Wales, and to provide an objective method for assessing habitat quality.
Biotope mapping at different flows was undertaken to establish how the biotope sequence differs among sites and with increasing discharge. Threshold discharges at which biotopes change are related to flow duration data to predict annual patterns of biotope ‘patchiness’ and ‘diversity’. Flows may then be manipulated to maintain ‘natural’ or ‘desirable’ biotopes. Sustainable management of aquatic systems and their biota would require flow management of critical reaches or biotopes, at key life-stages of target organisms.
Assessment of the alterations of the aquatic environment downstream from a polluted tributary of the river Po (Italy)
Authors: Viganò L. , Barbiero G. , Buffagni A. , Mingazzini M. , Pagnotta R. 
Published: November 2008

Abstract
A comprehensive evaluation of the results of many recent and ongoing studies has been performed in an attempt to assess which stressors are acting and what alterations could be derived for the aquatic organisms of the river Po downstream from one of its tributaries, the river Lambro. With this aim in view, this stretch of the river Po was compared with the immediate upper reach which is characterized by an overall good quality. The comparison was based on four categories of indicators, that is, watershed stress, physical-habitat alteration, and in particular chemical exposure and biological responses both of which were thoroughly examined. The reach located downstream of the river Lambro was found to be contaminated by a complex mixture of pollutants that were detected at low/moderate concentration values. This makes the area representative of what can be considered as a ‘grey’ level of pollution, that is the most frequent condition of watercourses worldwide. Nevertheless, the effects derived from such moderate/low levels of contamination for aquatic life are difficult to assess. Most of the indicators were found to be changed downstream of the river Lambro and different kinds of alterations were observed in both resident species and laboratory-test organisms. Although more information is necessary to understand less evident impairments as, for example, of the fish community, it can be concluded that a continuous interaction between chronic toxicity and trophic enrichment is the process that characterizes this riverine environment and affects the community. On the grounds of these findings, some suggestions are also proposed pertaining to ‘grey’ areas and their investigation.