bluuebunny/crossref_metadata_2025 huggingface dataset:
The political nature of taxation in Visigothic Spain
Authors: Castellanos Santiago
Published: July 2004

This paper is an attempt to analyse taxation from a wide‐ranging social perspective. Earlier studies of this topic have focused on institutional aspects of taxation and produced statistical information of great value. The historian who is trying to understand the social structures of the past should, however, examine the significance, nature and function of taxation in its wider historical context. In this sense, and in the specific case of post‐Roman, or Visigothic, Spain, a study of the social aspects of taxation reveals new meanings of the term ‘politics’, showing it to involve far more than a single inflexible concept independent of social factors. On the one hand, one should not equate taxation with fiscality, because the latter is one part (that concerning the fiscus or royal patrimony) of the wider whole comprised by the former: the capacity of the regnum to yield tribute, which is in turn related to revenue extracted by the aristocracy. It was the fiscal dimension of taxation that allowed the Visigothic kingdom to survive in Spain for two centuries. On the other hand, the centre, occupied by different sectors of the potentes, negotiated with other groups of these same potentes. These negotiations underlay military support for the centre, as well as provoking crises and mistrust when they were bypassed. Taxation was an integral part of such negotiations.
Triple scheme of learning support design for scientific discovery learning based on computer simulation: experimental research
Authors: Zhang Jianwei , Chen Qi , Sun Yanquing , Reid David J.
Published: July 2004

Abstract
Learning support studies involving simulation‐based scientific discovery learning have tended to adopt an ad hoc strategies‐oriented approach in which the support strategies are typically pre‐specified according to learners' difficulties in particular activities. This article proposes a more integrated approach, a triple scheme for learning support design on the basis of the systematic analysis of the internal conditions of scientific discovery learning. The triple learning support scheme involves: (a) interpretative support that helps learners with knowledge access and the generation of meaningful and integrative understandings; (b) experimental support that scaffolds learners in systematic and valid experimental activities; and (c) reflective support that increases learners' self‐awareness of the discovery processes and prompts their reflective abstraction and integration. Two experiments were conducted with eighth graders (13‐year‐olds) to examine the effects of these learning supports embedded into a simulation program on floating and sinking. The overall results support the main hypotheses that learning supports in a simulation environment should be directed towards the three perspectives to invite meaningful, systematic, and reflective discovery learning.
A study of learning time patterns in asynchronous learning environments
Authors: Hwang Wu‐Yuin , Wang Chin‐Yu
Published: July 2004

Abstract
This research makes use of learning time intensity, burst evaluating equations, and state denotation approaches to evaluate the learning time characteristics of students. Through comparing learning time intensity, six burst styles and three diligence styles are categorized. From the statistical results and interaction content analysis, some pedagogical phenomena were found. The first finding is that the more diligent learners were, the higher the quality and quantity of their interaction. The second is that learners whose learning time intensity was mainly located in the early period of the course and whose interaction content included many complaints were suspected to be possible dropouts. The third finding is that learners whose learning time intensity was mainly located in the later period had achievements that were significantly different from those of the regular periodical reading learners whose learning time intensity was distributed in all periods of the course. The above findings raise some issues and suggestions for those concerned with proposing asynchronous courses. As students can pace their own learning in an asynchronous learning environment, it is hard to avoid getting used to intermittent intensive reading. Instructors should consider seriously how to guide students to learn in a proper sequence through a well‐scheduled instructional programme. It is necessary to encourage students to exercise self‐discipline in regular on‐line reading for better learning outcomes.
A constructivist mobile learning environment supported by a wireless handheld network
Authors: Zurita Gustavo , Nussbaum Miguel
Published: July 2004

AbstractThere is a need to incorporate constructivist environments in the pedagogical practice. A constructivist learning environment allows students to build up their own knowledge (based on previous one) while working jointly among them in a reflexive process directed by the teacher. Wireless interconnected handhelds can introduce a space that favours constructivism and collaboration in order to achieve creation of new knowledge. We have developed a constructivist learning environment supported by handhelds, for the teaching of reading for first graders. This environment was compared to an equivalent constructivist environment without technological support, obtaining significant different learning results.
Investigating the use of ICT‐based concept mapping techniques on creativity in literacy tasks
Authors: Riley Nigel R. , Åhlberg Mauri
Published: July 2004

AbstractThe key research question in this small‐scale study focuses on the effects that an ICT (information and communications technologies)‐based concept mapping intervention has on creativity and writing achievement in 10–11‐year‐old primary age pupils. The data shows that pupils using a concept mapping intervention significantly improve their NFER non‐verbal reasoning age‐standardised scores over a control group with a higher baseline whose scores remain constant. Evidence linking this with using ICT‐based concept mapping remains inconclusive. Correlation studies show that writing achievement and creativity are linked and that writing achievement and concept mapping connectivity are linked. However, there is no conclusive evidence for linking concept mapping connectivity with creativity. Findings show that concept mapping components increase post‐test and that concept mapping ability can be evaluated using a connectivity index that may have some predictive value in assessing writing achievement. The findings suggest that ICT‐based concept mapping provides a reliable framework from which to structure writing and that ICT enhances learning and use of this representational technique and provides opportunities for developing innovative and educationally valid practices.
The effects of discovery learning and expository instruction on the acquisition of definitional and intuitive knowledge
Authors: Swaak Janine , De Jong Ton , Van Joolingen Wouter R.
Published: July 2004

Abstract
Types of learning with a strong emphasis on the responsibility of the learner (such as discovery learning) are gaining popularity over traditional forms of (expository) instruction. Discovery learning distinguishes itself by the central role of learning processes such as hypothesis generation (induction), experiment design, and data interpretation. Expository instruction pays more attention to directly ‘exposing’ definitions and equations to learners. In the current study, students worked with either a simulation (discovery learning) or a hypertext learning environment (expository instruction) with the same domain content. Each of the environments contained a large number of assignments. The study followed a pre‐test, post‐test design. To measure the knowledge acquired a definitional knowledge test, an intuitive knowledge test (where both correctness and speed of answering are aspects that are measured) and a test in which relations needed to be explained were administered. It was predicted that the hypertext group would outperform the simulation group on the definitional knowledge test and it was expected that the simulation group would perform better on the intuitive knowledge test. Results showed that both the interaction with the simulation and with the hypertext resulted in substantial learning gains. It was found that the hypertext group performed better on the definitional knowledge test. On the intuitive knowledge test the hypertext scored better than the simulation group on the correctness of the items but not on the time needed to answer items. On the explanation test there was no difference between the two groups. An analysis of interaction processes as recorded in the logfiles indicates that the differences between both environments in their actual usage were less distinctive than expected. In the simulation group many students followed the assignments given and did not engage in self‐guided discovery. Since the assignments were rather directive, this resulted in ‘discovery behaviour’ that focused on generating outcomes; outcomes that were also, and more directly presented in the hypertext environment. For research and practice, this implies that simulations are to be considered only when clear benefits of discovery are expected, and only with complex domains, sufficient learning time and freedom for students in the assignments to engage in discovery.
Karstification as geomorphological evidence of river incision: the karst of Cousance and the Marne valley (eastern Paris Basin)
Authors: Jaillet Stéphane , Pons‐Branchu Edwige , Brulhet Jacques , Hamelin Bruno
Published: July 2004

The Cousance karst (located between the valleys of the Saulx and Marne) has been studied to determine the temporal records of river incision in the eastern Paris Basin, around the ANDRA experimental nuclear waste repository. Two generations of karst are recognized. The first is a palaeophreatic karst indicative of an old base level, now uplifted +75 m above the underground streams. It is underlain and drained by a second generation of karst with active sinks, which records the vertical evolution following the entrenchment of the River Marne. Ten U/Th dates of speleothems from shafts in the karst show that there were discontinuous growth episodes, mainly during isotopic stages 3 and 5 (between 102.4 ± 1.2 and 49.4 ± 0.4 ka bp) but also during isotopic stage 2 at 16.3 ± 0.1 and 20.9 ± 0.3 ka bp. These dates provide an absolute age limit for the start of vertical development of the karst, at the latest during isotope stage 5c.
Pseudotachylytes from Corsica: fossil earthquakes from a subduction complex
Authors: Austrheim Håkon , Andersen Torgeir B.
Published: July 2004

Subduction zones are the most seismically active tectonic environment on Earth. Here we report fault‐rock evidence of palaeoearthquakes from a subduction complex. Pseudotachylyte veins formed by shear heating on faults at seismic strain rates contain dendrites, spherulites and acicular minerals characteristic of blueschist facies conditions. The veins have been found in both mantle peridotite and gabbro. Our discovery from Corsica opens a new avenue of research towards understanding mechanisms related to subduction zone earthquakes and the conditions at which these are released.
Ion microprobe and ID‐TIMS U–Pb dating on zircon grains from leg 173 amphibolites: evidence for Permian magmatism on the West Iberian margin
Authors: Gardien V. , Paquette J. L.
Published: July 2004

In this paper, we report evidence for Permian magmatism at the ocean–continent transition zone of the West Iberian margin, by dating magmatic intrusion of amphibolite precursors drilled at site 1067 during ODP leg 173. The P–T conditions recorded by the amphibolites indicate that the latter was emplaced at the bottom of a 25‐km‐thick crust. Subhedral to rounded and colourless zircon grains were obtained from samples at the base of the cored section. ID‐TIMS dating on these zircon grains yielded a lower intercept age of 247 ± 5 Ma and a poorly defined upper intercept around 2 Ga. In situ dating of single zircons by ion‐microprobe (CAMECA IMS 1270) provided an age of 246 ± 5 Ma. This Permian age is interpreted as a minimum estimate for the emplacement of the gabbroic melts at the base of the Hercynian crust during the early stage of rifting between the Iberia–Newfoundland conjugate margins.
Brittle deformation in the inner NW Alps: from early orogen‐parallel extrusion to late orogen‐perpendicular collapse
Authors: Champagnac Jean‐Daniel , Sue Christian , Delacou Bastien , Burkhard Martin
Published: July 2004

Internal parts of the Alps have undergone widespread extensional deformation in the course of their Neogene exhumation history. Palaeostress inversion methods are used to map the prevailing stress fields and their evolution through time. Here we present new data from 100 sites with a total of about 2000 faults/striae couples, covering a large portion of the inner north‐western Alps. Palaeostress tensors are mostly extensional, although one‐third of them are transcurrent. The dominant direction of minimum horizontal stress axes (σ3) is in an orogen‐parallel (N30° to N70°) orientation around the bend of the north‐west alpine arc. A comparison between this older (Neogene, post‐metamorphic) stress field with the current stress and strain field determined from seismotectonics and geodesy indicates a change in deformation mode from early orogen‐parallel extrusion to a late and ongoing orogen‐perpendicular spreading.
Effects of the hydrothermal circulation on the strain field of the Campanian Plain (southern Italy)
Authors: Milano G. , Petrazzuoli S. , Ventura G.
Published: July 2004

Focal mechanisms of earthquakes and fault‐slip data have been collected to constrain the strain regime acting in the hydrothermal zone and surrounding areas of the Campanian Plain (southern Italy), a NW–SE elongated structural depression. The NW–SE striking faults bounding the depression move in response to a NE–SW striking regional extension. Within the depression, an extended hydrothermal circulation occurs related to the Vesuvius, Campi Flegrei and Ischia active volcanoes. In this zone, the strike of the extension is N–S. Results from a finite element model constrained by the collected data show that the presence of a lower rigidity zone due to the hydrothermal circulation may explain (a) the observed deflection of the direction of regional extension, and (b) why large magnitude earthquakes occur at the boundaries of the hydrothermal zone and not along the faults delimiting the structural depression.
Origin of silicate minerals in carbonatites from Alnö Island, Sweden: magmatic crystallization or wall rock assimilation?
Authors: Vuorinen Jaana Hode , Skelton Alasdair D. L.
Published: July 2004

Textural, electron microprobe and whole rock geochemical evidence from carbonatites and associated silicate rocks on Alnö Island, Sweden, suggest that the carbonatite, at the time of emplacement, could have been an (almost) pure CaCO3 liquid with a high volatile (H2O–CO2) content and that most silicate minerals, which are ubiquitously present, are either (1) assimilated from the surrounding wall rock, by progressive and coupled fragmentation and corrosion; or (2) by‐products of corrosive interaction between the carbonatite liquid and the wall rock. This interpretation is supported by balancing a reaction to describe interaction between carbonatite and a cpx + ne‐bearing (ijolite) wall rock. Although our analysis does not preclude the possibility that fenitizing agents (e.g. Na, Fe) were transported by the carbonatite liquid, these components are not required to drive the observed mineralogical changes in the carbonatite.
Selectivity of weed harrowing in lupin
Authors: Jensen R K , Rasmussen J , Melander B
Published: July 2004

Three field experiments were conducted in lupin in 1997, 1998 and 1999 to study two aspects of selectivity of post‐emergence weed harrowing; the ability of the crop to resist soil covering (the initial damage effect), and the ability of the crop to tolerate soil covering (the recovery effect). Each year soil covering curves and crop tolerance curves were established in three early growth stages of lupin. Soil covering curves connected weed control and crop soil cover in weedy plots, and crop tolerance curves connected crop yield and crop soil cover in weed‐free plots. The experiments showed that both resistance and tolerance were unaffected by the growth stage of lupin within the range from the cotyledon to the 7–8 leaf growth stages. Tolerance to soil covering was also unaffected by year whereas the ability of the crop to resist soil covering was highly affected by year. Lupin showed high tolerance to soil covering but a rather low ability to resist soil covering. Harrowing at multiple growth stages supported the finding that lupin is fairly tolerant to soil covering. Advantages and disadvantages of using soil covering as a measure of crop damage is discussed. In conclusion, weed harrowing in lupin showed positive prospects because of high tolerance to crop soil cover.
Germination response of Phalaris paradoxa L. seed to different light qualities
Authors: Taylor I N , Peters N C B , Adkins S W , Walker S R
Published: July 2004

The influence of different light regimes on the germination of Australian and English populations of Phalaris paradoxa L. (awned canary‐grass) seed was investigated to determine the impact of changing tillage practices on weed infestation. Seeds of all biotypes were highly viable, but differed in levels of innate dormancy (26–99%). In one experiment seed from a single Australian biotype, either enclosed in the spikelet glumes or having the spikelet glumes removed, were exposed to nine light treatments. Germination was stimulated by red and white light, but was inhibited by far‐red light. Time to 50% germination was less for seed enclosed in the spikelet glumes than for naked caryopses, although the final percentage of seed germinating when still enclosed in the spikelet glumes was significantly lower than for naked caryopses. In another experiment, six Australian and English biotypes with varying dormancy characteristics were exposed to eight light treatments. Red light did not stimulate germination in the deeply dormant biotype, however stimulated all other biotypes. Germination in darkness was below 20% in all biotypes except for one where germination was 51%. To overcome dormancy seeds were imbibed and placed in darkness at 16°C for either 7 or 14 days prior to exposure to red or white light for a single 15‐min period. Dormancy in all biotypes was overcome indicating that a period of burial may decrease the dormancy level and increase seed sensitivity to light. This increased light sensitivity suggests that exposure to light during tillage may stimulate germination in P. paradoxa seed.
Cytotoxic constituents of Alectra and Striga species
Authors: Rank C , Rasmussen L S , Jensen S R , Pierce S , Press M C , Scholes J D
Published: July 2004

Decimation of cereal growth and yields by hemiparasitic Striga species cannot be accounted for entirely by the removal of host‐plant resources. The production of toxic compounds by the parasite has been suggested. An investigation of three species of the economically important Striga and the related Alectra vogelii has now resulted in the isolation of eight iridoid glucosides (mussaenosidic acid, mussaenoside, gardoside methyl ester, bartsioside, isoaucubin, melittoside, aucubin and eurostoside), two caffeoyl phenylethyl glycosides (calceolarioside  A and verbascoside) as well as shikimic acid and trigonelline, all identified by NMR spectroscopy. The iridoids are potent cytotoxins and probably represent an anti‐herbivore defence system common to Scrophulariaceae (sensu lato). This has the potential to explain differences in tolerance apparent for contrasting host taxa and cultivars. The nature of the iridoids present also provides additional validation of the recent transferral of parasitic Scrophulariaceae (s.l.) to Orobanchaceae.
Joint action of amino acid biosynthesis‐inhibiting herbicides
Authors: Kudsk P , Mathiassen S K
Published: July 2004

The joint action of binary mixtures of the amino acid biosynthesis‐inhibiting herbicides glyphosate, glufosinate‐ammonium, metsulfuron‐methyl and imazapyr was assessed in pot experiments applying the Additive Dose Model (ADM). Plants of Sinapis arvensis or S. alba were sprayed with seven doses of the herbicides alone and binary fixed‐ratio mixtures of the four herbicides. In total, 73 binary mixtures were studied in six separate experiments. Mixtures of glyphosate and glufosinate‐ammonium were less phytotoxic than predicted by ADM whether commercial formulations or technical grade products were applied. In contrast, mixtures of glyphosate and metsulfuron‐methyl, glyphosate and imazapyr, glufosinate‐ammonium and metsulfuron‐methyl, glufosinate‐ammonium and imazapyr, and metsulfuron‐methyl and imazapyr either followed ADM or were synergistic. Synergism was observed most frequently for mixtures of glyphosate or glufosinate‐ammonium with metsulfuron‐methyl. Synergism was also more pronounced for commercial formulations of glyphosate and glufosinate‐ammonium than for the corresponding technical grade formulations, implying that synergism was caused by the presence of the formulation constituents of the commercial glyphosate and glufosinate‐ammonium formulations in the spray solution.
Locating quantitative trait loci associated with Orobanche crenata resistance in pea
Authors: Valderrama M R , Román B , Satovic Z , Rubiales D , Cubero J I , Torres A M
Published: July 2004

Orobanche crenata (broomrape) is a root parasite that represents the major constraint for pea (Pisum sativum) cultivation in the Mediterranean area and the Middle East. The efficacy of available control methods is minimal and breeding for O. crenata resistance is considered the most promising strategy of control. Only moderate levels of incomplete resistance are available in pea germplasm. In order to identify and map the quantitative trait loci (QTL) controlling the trait, 115 F2 plants derived from the cross between a susceptible and a resistant parent were analysed using isozymes, random amplified polymorphic DNA and sequence tagged site markers. F2‐derived F3 lines were studied for O. crenata resistance under field conditions. The linkage map was constructed with MAPMAKER V2.0. Of 217 markers, 120 could be mapped into 21 linkage groups. Linkage groups consisted of 13 to two marker loci covering 1770 cM. The mean inter‐marker distance was 17.64 cM. Simple interval mapping (SIM) and composite interval mapping (CIM) were performed using QTL Cartographer. The CIM approach using five cofactors was clearly the most efficient way to locate putative QTL. Two QTL for O. crenata resistance (Ocp1 and Ocp2), explaining only a moderate portion of the observed variation (9.6% and 11.4% respectively), were detected.
The Chemical Synthesis of Rat Relaxin and the Unexpectedly High Potency of the Synthetic Hormone in the Mouse
Authors: Büllesbach Erika E. , Schwabe Christian
Published: July 2004

Rat relaxin, as isolated from ovaries, has been described in the literature as a low potency hormone in the mouse symphysis pubis assay. Searching for an explanation, a helix‐breaking glycine residue in the B chain seemed to be the most auspicious perturbation. Rat relaxin was chemically synthesized and analyzed by reverse‐phase high performance liquid chromatography, amino acid composition, mass spectrometry and circular dichroic spectroscopy. Analogs of rat relaxin were synthesized either with aspartic acid in place of the helix‐breaking glycine residue in the receptor‐binding region of the B chain or with Asp‐Leu‐Val instead of Gly‐Tyr‐Val at positions B14‐B16. In receptor‐binding assays [B14D, B15L, B16V]relaxin was a better ligand than rat relaxin, whereas the [B14D]relaxin was less potent. In the mouse symphysis pubis assay, both analogs were less potent than unmodified rat relaxin, but the [B14D, B15L, B16V]relaxin was better than [B14D]relaxin. In contrast to previous reports on native rat relaxin, the chemically synthesized rat relaxin proved to be as active as human and porcine relaxin with respect to the standard mouse assay system. Glycine, which is considered to be a perturbator in an α helix, is not only tolerated in the B14 position but is required for full biological potency.
Effect of Hyperglycemia on the Polyol Pathway in Rat Kidney During the Perinatal Period
Authors: Freund Nicole , Prieur Béatrice , Bismuth Jeanne , Delaval Evelyne
Published: July 2004

The activity of the polyol pathway was studied in developing rat kidney. For this purpose, sorbitol content, aldose‐reductase activity and sorbitol‐dehydrogenase activity were determined in papilla from fetuses and 24‐h‐old neonates. After birth, no significant difference was observed in sorbitol content, whereas sorbitol‐dehydrogenase activity decreased and aldose‐reductase activity doubled. Changes in aldose‐reductase activity were due to an increased number of enzymatic sites but not with a change in affinity. Low levels of sorbitol were found in fetal and neonatal medulla together with low levels of urine osmolarity. In neonates, sorbitol contents were tenfold lower than in the adult, probably as a result of a lower affinity and a lower number of enzymatic aldose‐reductase sites. Attempts to increase the activity of polyol pathway in fetal kidney were made by means of hyperglycemic animals; this approach resulted in an increase of aldose‐reductase activity without any change in sorbitol content. Our results indicate that, in fetal and neonatal kidneys, aldose‐reductase activity is probably not the limiting factor for sorbitol synthesis; another parameter, such as the availability of NADPH, might explain the low efficiency of the polyol pathway during the perinatal period.
Analysis of Phosphorylation and Mutation of Tyrosine Residues of Calmodulin on Its Activation of the Erythrocyte Ca2+‐transporting ATPase
Authors: Sacks David B. , Lopez Maria M. , Li Zhigang , Kosk‐Kosicka Danuta
Published: July 2004

The role played by the phosphorylation sites of calmodulin on its ability to activate the human erythrocyte Ca2+‐transporting ATPase (Ca2+‐ATPase) was evaluated. Phosphorylation of mammalian calmodulin on serine/threonine residues by casein kinase II decreased its affinity for Ca2+‐ATPase by twofold. In contrast, tyrosine phosphorylation of mammalian calmodulin by the insulin‐receptor kinase did not significantly alter calmodulin‐stimulated Ca2+‐ATPase activity. Two variant calmodulins, each containing only one tyrosine residue (the second Tyr is replaced by Phe) were also examined: [F138]calmodulin, a mutant containing tyrosine at position 99, and wheat germ calmodulin which has tyrosine at position 139. The concentrations of [F138]calmodulin and wheat germ calmodulin required for half‐maximal activation of Ca2+‐ATPase were tenfold and fourfold higher, respectively, than mammalian calmodulin.

Phosphorylation at Tyr99 of [F138]calmodulin shifted its affinity for Ca2+‐ATPase towards that of mammalian calmodulin. However, phosphorylation at Tyr139 of wheat germ calmodulin had essentially no effect on its interaction with Ca2+‐ATPase. Thus, all of the observed effects of both phosphorylation and substitution of residues of calmodulin are on its affinity for Ca2+‐ATPase, not on Vmax. The effects are dependent on the site of phosphate incorporation. Replacement of tyrosine with phenylalanine has a larger effect than phosphorylation of tyrosine, suggesting that the observed functional alterations reflect a secondary conformational change in the C‐terminal half of calmodulin, the region that is important in its activation of Ca2+‐ATPase.
Eradication of two exotic ants from Kakadu National Park
Authors: Hoffmann Benjamin D. , O'Connor Simon
Published: July 2004

Kakadu is a global icon for nature conservation, but like similar sites elsewhere it is constantly under threat from exotic species. This apparent eradication of two highly invasive ant species is a clear example that such projects are achievable, and lessons learnt from such successes will assist the ongoing fight against alien species.
Changes in vegetation patterns on the margins of a constructed wetland after 10 years
Authors: Garde Leigh M. , Nicol Jason M. , Conran John G.
Published: July 2004

Summary  A constructed urban wetland in Adelaide was surveyed 18 months and 10 years after construction to see how shoreline vegetation, soil electrical conductivity (EC), texture and pH changed over time and to provide data for future site management. Multivariate analysis detected four plant associations at 18 months: salt‐tolerant taxa on conductive clays; a weed‐dominated community on lower EC soil; and two smaller waterlogged, low EC clusters dominated by Common Reed (Phragmites australis) and Sea Club‐Rush (Bolboschoenus caldwellii), respectively. At 10 years, site cover and heterogeneity was higher, with the margins dominated by Phragmites and salt‐tolerant species. EC was much lower and more uniform, and the soils were heavier and more alkaline. Managed storm water flushing apparently lowered soil EC, but possibly also disturbed the shoreline. However, weeds were still common, and the potential for domination by Phragmites at the expense of other native shoreline species means that ongoing monitoring and hydrological and vegetation management are essential to maintain site habitat diversity.
A trial re‐introduction of the Greater Stick‐nest Rat (Leporillus conditor) in arid South Australia
Authors: Moseby Katherine Elizabeth , Bice Jacqueline Kate
Published: July 2004

Summary  Eight Greater Stick‐nest Rats (Leporillus conditor S.) were re‐introduced into a 8 ha release pen within the Arid Recovery Reserve, South Australia, in September 1998. Their weight, reproductive condition, activity, habitat use and grazing impacts were investigated during the 8 month experimental trial. Greater Stick‐nest Rats increased in weight and bred successfully after the end of summer (April 1999). They consumed native vegetation including Bladder Saltbush (Atriplex vesicaria), Ruby Saltbush (Enchylaena tomentosa) and Sturt's Pigface (Gunniopsis quadrifida) but Sturt's Pigface was most heavily browsed and no monitored plants died from over‐browsing during the trial. Rats preferred dune habitat and the two largest female rats maintained discrete activity areas and shelter sites. Nocturnal activity of adult male rats was centred around adult females with both sexes generally staying within 150 m of daytime shelter sites. Shelter sites were commonly within dead Umbrella Wattle (Acacia ligulata) or Narrow‐leafed Hopbush (Dodonaea viscosa) shrubs covered in low vegetation, and rats also adapted burrows of other species to use as below‐ground components. Although supplementary water was provided and may have ensured survival over the hot summer months, the trial release was considered a success and a full‐scale re‐introduction of the Greater Stick‐nest Rat was conducted in 1999.
A Dependence Metric for Possibly Nonlinear Processes
Authors: Granger C. W. , Maasoumi E. , Racine J.
Published: July 2004

Abstract.  A transformed metric entropy measure of dependence is studied which satisfies many desirable properties, including being a proper measure of distance. It is capable of good performance in identifying dependence even in possibly nonlinear time series, and is applicable for both continuous and discrete variables. A nonparametric kernel density implementation is considered here for many stylized models including linear and nonlinear MA, AR, GARCH, integrated series and chaotic dynamics. A related permutation test of independence is proposed and compared with several alternatives.
Bayesian Subset Model Selection for Time Series
Authors: Unnikrishnan N. K.
Published: July 2004

Abstract. This paper considers the problem of subset model selection for time series. In general, a few lags which are not necessarily continuous, explain lag structure of a time‐series model. Using the reversible jump Markov chain technique, the paper develops a fully Bayesian solution for the problem. The method is illustrated using the self‐exciting threshold autoregressive (SETAR), bilinear and AR models. The Canadian lynx data, the Wolfe's sunspot numbers and Series A ofBox and Jenkins (1976)are analysed in detail.
Analysis of low count time series data by poisson autoregression
Authors: Freeland R. K. , McCabe B. P. M.
Published: July 2004

Abstract.  This study provides new methods of assessing the adequacy of the Poisson autoregressive time‐series model for count data. New expressions are given for the score function and the information matrix and these lead to the construction of new types of residuals for this model. However, these residuals often need to be supplemented by formal statistical procedures and an overall test of the model adequacy is given via the information matrix equality that holds for correctly specified models. The techniques are applied to a monthly count data set of claimants for wage loss benefit, in order to estimate the the expected duration of claimants in the system.
Error bounds and asymptotic expansions for toeplitz product functionals of unbounded spectra
Authors: Lieberman Offer , Phillips Peter C. B.
Published: July 2004

Abstract.  This paper establishes error orders for integral limit approximations to traces of powers (to the pth order) of products of Toeplitz matrices. Such products arise frequently in the analysis of stationary time series and in the development of asymptotic expansions. The elements of the matrices are Fourier transforms of functions which we allow to be bounded, unbounded, or even to vanish on [−π, π], thereby including important cases such as the spectral functions of fractional processes. Error rates are also given in the case in which the matrix product involves inverse matrices. The rates are sharp up to an arbitrarily small ɛ > 0. The results improve on the o(1) rates obtained in earlier work for analogous products. For the p = 1 case, an explicit second‐order asymptotic expansion is found for a quadratic functional of the autocovariance sequences of stationary long‐memory time series. The order of magnitude of the second term in this expansion is shown to depend on the long‐memory parameters. It is demonstrated that the pole in the first‐order approximation is removed by the second‐order term, which provides a substantially improved approximation to the original functional.
Behaviour of Dickey–Fuller Unit‐Root Tests Under Trend Misspecification
Authors: Kim Tae‐Hwan , Leybourne Stephen , Newbold Paul
Published: July 2004

Abstract.  We analyse the case where a unit‐root test is based on a Dickey–Fuller regression the only deterministic term of which is a fixed intercept. Suppose, however, as could well be the case, that the actual data‐generating process includes a broken linear trend. It is shown theoretically, and verified empirically, that under the I(1) null and I(0) alternative hypotheses the Dickey–Fuller test can display a wide range of different characteristics depending on the nature and location of the break.
Large sample properties of parameter least squares estimates for time‐varying arma models
Authors: Francq Christian , Gautier Antony
Published: July 2004

Abstract.  This paper considers estimation of ARMA models with time‐varying coefficients. The ARMA parameters belong to d different regimes. The changes in regime occur at irregular time intervals. Consistency and asymptotic normality of least squares and quasi‐generalized least squares estimators are shown.
CHARACTERIZING AND QUANTIFYING PHOTOINHIBITION IN INTERTIDAL MICROPHYTOBENTHOS1
Authors: Blanchard Gérard F. , Guarini Jean‐Marc , Dang Christian , Richard Pierre
Published: July 2004

This study characterizes the short‐term influence of the sustained saturating irradiance encountered by the microphytobenthos inhabiting intertidal mudflats. The kinetics of photoinhibition in epipelic microalgae from intertidal mudflats were investigated in the laboratory. Previously isolated benthic microalgae were exposed to a saturating photon flux density (PFD) for periods ranging from 0 to 180 min; every 30 min, a photosynthesis‐irradiance curve was established to quantify the effect of the saturating PFD on both parameters αB, the photosynthetic efficiency, and PmB, the photosynthetic capacity. The αB decreased from the beginning of light exposure until the end, whereas PmB first slightly increased and then diminished from 90 min exposure onward. It turned out that epipelic microphytobenthos undergoes photoinhibition after about 90 min of saturating PFD. The possible ecological consequences of these ecophysiological results are discussed.
MOLECULAR CHARACTERIZATION OF THE ASSIMILATORY NITRATE REDUCTASE GENE AND ITS EXPRESSION IN THE MARINE GREEN ALGA DUNALIELLA TERTIOLECTA (CHLOROPHYCEAE)1
Authors: Song Bongkeun , Ward Bess B.
Published: July 2004

Nitrate is used as a nutrient for growth by many organisms through the nitrate assimilation pathway. The key enzyme involved in nitrate assimilation is nitrate reductase (NR). Transcriptional regulation of NR genes has been studied in various phototrophic eukaryotes from freshwater or terrestrial habitats. Here, we describe the first NR gene from a marine phytoplankton, the green alga Dunaliella tertiolecta Butcher. Its sequence is very similar to that of the other green algae, but its intron structure and transcriptional regulation differ significantly. A partial genomic NR gene fragment was cloned using direct PCR amplification with degenerate primers, and rapid amplification of cDNA ends was performed to obtain a complete NR gene from a cDNA of D. tertiolecta. The complete NR gene of D. tertiolecta is 2.7 kb in size and is similar at the amino acid level to the NRs from freshwater green algae Chlorella vulgaris (50.6%), Chlamydomonas reinhardtii (58.4%), and Volvox carteri (59.4%). Transcriptional regulation of D. tertiolecta NR was examined in response to different nitrogen sources and during the diel cycle. Dunaliella tertiolecta NR transcript was induced by nitrate and repressed by ammonium. In addition, transcription was not induced under nitrogen depletion. Induction of NR transcript responded to the diel cycle, and transcript levels were maximized within an hour after the beginning of the light period. The induction and repression of NR transcript were much slower than reported in freshwater green algae, which may be related to the size of internal nitrogen pools.
EFFECTS OF LOWERING TEMPERATURE DURING CULTURE ON THE PRODUCTION OF POLYUNSATURATED FATTY ACIDS IN THE MARINE DIATOM PHAEODACTYLUM TRICORNUTUM (BACILLARIOPHYCEAE)1
Authors: Jiang Hanming , Gao Kunshan
Published: July 2004

The composition of fatty acids and contents of eicosapentaenoic acid (EPA) and polyunsaturated fatty acids (PUFAs) of the economically important marine diatom, Phaeodactylum tricornutum (Bohlin), were investigated to see whether reducing the culture temperature enhances the production of EPA and PUFAs. The contents of EPA and PUFAs of P. tricornutum were found to be higher at lower temperature when cultured at 10, 15, 20, or 25°C. When the cells grown at 25°C were shifted to 20, 15, or 10°C, the contents per dry mass of PUFAs and EPA increased to the maximal values in 48, 24, and 12 h, respectively. The highest yields of PUFAs and EPA per unit dry mass (per unit volume of culture) were 4.9% and 2.6% (12.4 and 6.6 mg·L−1), respectively, when temperature was shifted from 25 to 10°C for 12 h, both being raised by 120% compared with the control. The representative fatty acids in the total fatty acids, when temperature was lowered from 25 to 10°C, decreased proportionally by about 30% in C16:0 and 20% in C16:1(n−7) but increased about 85% in EPA. It was concluded that lowering culture temperature of P. tricornutum could significantly raise the yields of EPA and PUFAs.
INORGANIC NITROGEN AND PHOSPHORUS UPTAKE KINETICS INPALMARIA PALMATA(RHODOPHYTA)1
Authors: Martínez Brezo , Rico Jose M.
Published: July 2004

The N and P uptake responses were studied in a northern Spanish population of the edible red seaweedPalmaria palmata(Linnaeus) Kuntze. The fronds were incubated at different concentrations, and the nutrient depletion in the medium was measured at successive times to calculate uptake rates.Palmaria palmatauptake response was biphasic and nonsaturable for inorganic P. This would allow the species to exploit transient pulses of high P concentration in natural and fertilized conditions. Such a response is a common feature of algae avoiding nutrient deficiency. At average concentrations measured in the ocean, the response was nonsaturable for inorganic N sources, except for ammonium in autumn and winter when it is not the major N source. In contrast to the general rule of ammonium being taken at a higher rate than nitrate, we found similar affinity for both nutrients corresponding to the minor role of ammonium as N source for field populations over the year.
DOMOIC ACID PRODUCTION By PSEUDO‐NITZSCHIA SERIATA (BACILLARIOPHYCEAE) IN SCOTTISH WATERS1
Authors: Fehling Johanna , Green David H. , Davidson Keith , Bolch Christopher J. , Bates Stephen S.
Published: July 2004

In 1999, a 49,000 km2 area in western Scottish waters was closed to shellfish harvesting due to the amnesic shellfish poisoning (ASP) toxin domoic acid (DA). The only previously confirmed DA producer identified had been Pseudo‐nitzschia australis Frenguelli. The toxin has appeared every year since and has led to more harvesting closures. We isolated and cultured two strains of Pseudo‐nitzschia seriata f. seriata (P. T. Cleve) H. Peragallo from western Scottish waters in 2001 and 2002. They were identified using TEM analysis of their morphological fine structure and sequencing of the internal transcribed spacer (ITS)1, 5.8S, ITS2, and partial large subunit (LSU) rDNA. The morphology of the Scottish P. seriata f. seriata strains differed slightly, for example, in the number of poroid rows, from descriptions in identification keys. Comparison of P. seriata sequences with those of two co‐occurring Pseudo‐nitzschia australis isolates showed an overall divergence of only 0.012. Sequence divergence between both species was highest in the ITS1 region (0.036). Combined morphological and genetic approaches are needed to identify closely related Pseudo‐nitzschia species. The P. seriata strains grew successfully at 15°C, suggesting that although seen as a psychrophilic species, it may also occur at higher water temperatures. All isolates produced DA in stationary phase (measured on day 25): 0.16–0.23 pg DA·cell−1 in P. seriata and 0.15–1.68 pg DA·cell−1 in P. australis. Our study is the first to identify P. seriata f. seriata as a DA producer in Scottish waters and indicates that at least it and P. australis can be responsible for ASP toxicity in that region.
THE SEXUAL LIFE CYCLES OF PFIESTERIA PISCICIDA AND CRYPTOPERIDINIOPSOIDS (DINOPHYCEAE)1
Authors: Parrow Matthew W. , Burkholder JoAnn M.
Published: July 2004

Sexual life cycle events in Pfiesteria piscicida and cryptoperidiniopsoid heterotrophic dinoflagellates were determined by following the development of isolated gamete pairs in single‐drop microcultures with cryptophyte prey. Under these conditions, the observed sequence of zygote formation, development, and postzygotic divisions was similar in these dinoflagellates. Fusion of motile gamete pairs each produced a rapidly swimming uninucleate planozygote with two longitudinal flagella. Planozygotes enlarged as they fed repeatedly on cryptophytes. In <12 h in most cases, each planozygote formed a transparent‐walled nonmotile cell (cyst) with a single nucleus. Zygotic cysts did not exhibit dormancy under these conditions. In each taxon, dramatic swirling chromosome movements (nuclear cyclosis) were found in zygote nuclei before division. In P. piscicida, nuclear cyclosis occurred in the zygotic cyst or apparently earlier in the planozygote. In the cryptoperidiniopsoids, nuclear cyclosis occurred inthe zygotic cyst. After nuclear cyclosis, a single cell division occurred in P. piscicida and cryptoperidiniopsoid zygotic cysts, producing two offspring that emerged as biflagellated cells. These two flagellated cells typically swam for hours and fed on cryptophytes before encysting. A single cell division in these cysts produced two biflagellated offspring that also fed before encysting for further reproduction. This sequence of zygote development and postzygotic divisions typically was completed within 24 h and was confirmed in examples from different isolates of each taxon. Some aspects of the P. piscicida sexual life cycle determined here differed from previous reports.
GENE SEQUENCE DIVERSITY AND THE PHYLOGENETIC POSITION OF ALGAE ASSIGNED TO THE GENERA PHAEOPHILA AND OCHLOCHAETE (ULVOPHYCEAE, CHLOROPHYTA)1
Authors: O'Kelly Charles J. , Wysor Brian , Bellows Wendy K.
Published: July 2004

The phylogenetic position of microfilamentous marine green algae assigned to the species Phaeophila dendroides, Entocladia tenuis (Phaeophila tenuis, and Ochlochaete hystrix was examined through phylogenetic analyses of nuclear‐encoded small subunit rDNA and chloroplast‐encoded tufA gene sequences. These analyses placed the P. dendroides strains within the Ulvophyceae, at the base of a clade that contains representatives of the families Ulvaceae, Ulvellaceae, and the species Bolbocoleon piliferum, supporting an earlier hypothesis that P. dendroides constitutes a distinct lineage. Substantial divergence in both nuclear and plastid DNA sequences exists among strains of P. dendroides from different geographic localities, but these isolated strains are morphologically indistinguishable. The lineage may have an accelerated rate of gene sequence evolution relative to other microfilamentous marine green algae. Entocladia tenuis and O. hystrix are placed neither in the P. dendroides clade nor in the Ulvellaceae as previous taxonomic schemes predicted but instead form a new clade or clades at the base of the Ulvaceae. Ruthnielsenia gen. nov. is proposed to accommodate Kylin's species, which cannot be placed in Entocladia (=Acrochaete), Phaeophila, or Ochlochaete. Ruthnielsenia tenuis (Kylin) comb. nov., previously known only from Atlantic coasts, is reported for the first time from the Pacific coast of North America (San Juan Island, WA, USA). Isolates of R. tenuis from the Atlantic and Pacific coasts of North America have identical small subunit rDNA and tufA gene sequences.