bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in the turnover of Rubisco and levels of mRNAs of rbcL and rbcS in rice leaves from emergence to senescence
Authors: Suzuki Y. , Makino A. , Mae T.
Published: March 2003

Changes in the amount of ribulose 1,5‐bisphosphate carboxylase/oxygenase (Rubisco; EC 4·1·1·39) synthesized and degraded and the levels of rbcL and rbcS mRNAs were examined in the eighth leaf blades of rice from emergence to senescence. Synthesis of Rubisco was very active during leaf expansion, became quite low at the time of full expansion and then declined further during senescence. The changes in the levels of rbcL and rbcS mRNAs co‐ordinated approximately with those in the amount of Rubisco synthesized. Thus, it is suggested that the amount of Rubisco synthesized is determined primarily by the levels of rbcL and rbcS mRNAs during the life span of the leaves. Degradation of Rubisco started just before the time of full expansion and became far more active than its synthesis during senescence. Since the synthesis of Rubisco during senescence scarcely contributed to its amount, it can be concluded that the degradation of Rubisco is the major determinant for the amount of Rubisco in senescent leaves. The decline in the level of rbcL mRNA occurred much earlier in the developmental stage and proceeded at a much faster rate than that of rbcL DNA, indicating that the level of rbcL DNA is not a major determinant for the level of rbcL mRNA in senescent leaves of rice.
Earlier arrival of some farmland migrants in western Poland
Authors: Tryjanowski Piotr , Kuźniak Stanisław , Sparks Tim
Published: March 2003

A dataset consisting of observations on the first arrival dates (FAD) of 16 species of birds from a locality in western Poland during the period 1913–1996 is presented and analysed. For 14 of the 16 species, there is evidence of a trend towards earliness in recent years. In the 1970–1996 period this trend was significant for Pied Wagtail, Wood Pigeon, Black Redstart and Barn Swallow, and marginally significant for a further four species: European Serin, Blackcap, Common Nightingale and Red‐backed Shrike. Only two species showed the opposite trend in the 1970–1996 period: Lesser Whitethroat and Whinchat, of which only the former is (marginally) significant. The trend towards earliness was more pronounced for short‐distance (European) migrants than for long‐distance (African) migrants. Short‐distance migrants generally displayed a correlation with spring temperatures in the breeding locality, a feature less obvious in the long‐distance migrants.
The relative importance of dispersal limitation of vascular plants in secondary forest succession in Muizen Forest, Belgium
Authors: Verheyen Kris , Hermy Martin
Published: March 2003

Distribution patterns (frequency and percentage cover) of 18 forest plant species were studied in 34 ha of mixed deciduous forest (Muizen Forest, north Belgium). Stands varied in age between 6 and more than 223 years and both slow and fast colonizing species were studied.

 Detailed land use history data were combined with the species distribution maps to identify species‐specific colonization sources and calculate colonization distances.

 A multiple logistic regression model was constructed with four covariables: pH (which can impose limits on the potential species‐distribution), secondary forest age, distance from nearest colonization source and age–distance interaction, to allow us to account for the gradual completion of colonization over time.

 We could distinguish species which are limited by both dispersal and recruitment (Primula elatior, Arum maculatum and Lamium galeobdolon), mainly by dispersal (Anemone nemorosa, Deschampsia cespitosa), mainly by recruitment (Paris quadrifolia and Polygonatum multiflorum) and by neither (Geum urbanum, Ranunculus ficaria, Glechoma hederacea, Aegopodium podagraria, Ajuga reptans, Adoxa moschatellina and Oxalis acetosella).

 The low colonizing capacity of ancient forest plants cannot be attributed to a single cause; rather both dispersal and recruitment are limiting but the relative importance varies.
New approach to optical diffraction tomography yielding a vector equation of diffraction tomography and a novel tomographic microscope
Authors: Lauer V.
Published: March 2003

We first obtain a frequency‐space equation of diffraction tomography for the electric field vector, within the first‐order Born approximation, using a simplified formalism resulting from using three‐dimensional spatial frequencies and replacing outgoing waves by linear combinations of homogeneous plane waves. A coherent optical diffraction tomographic microscope is then described, in which a sample is successively illuminated by a series of plane waves having different directions, each scattered wave is recorded by phase‐shifting interferometry, and the object is then reconstructed from these recorded waves. The measurement process in this device is analysed taking into account the illuminating wave, the wave scattered by the sample, the reference wave, and the phase relations between these waves. This analysis yields appropriate equations that take into account the characteristics of the reference wave and compensate random phase shifts. It makes it possible to obtain a high‐resolution three‐dimensional frequency representation in full conformity with theory. The experimentally obtained representations show index and absorptivity with a resolution limit of about a quarter of a wavelength, and have a depth of field of about 40 µm.
Nanosecond fluorescence resonance energy transfer‐fluorescence lifetime imaging microscopy to localize the protein interactions in a single living cell
Authors: Elangovan M. , Day R. N. , Periasamy A.
Published: March 2003

Visualizing and quantifying protein–protein interactions is a recent trend in biomedical imaging. The current advances in fluorescence microscopy, coupled with the development of new fluorescent probes such as green fluorescent proteins, allow fluorescence resonance energy transfer (FRET) to be used to study protein interactions in living specimens. Intensity‐based FRET microscopy is limited by spectral bleed‐through and fluorophore concentration. Fluorescence lifetime imaging (FLIM) microscopy and lifetime measurements are independent of change in fluorophore concentration or excitation intensity, and the combination of FRET and FLIM provides high spatial (nanometre) and temporal (nanoseconds) resolution. Because only the donor fluorophore lifetime is measured, spectral bleed‐through is not an issue in FRET–FLIM imaging. In this paper we describe the development of a nanosecond FRET–FLIM microscopy instrumentation to acquire the time‐resolved images of donor in the presence and the absence of the acceptor. Software was developed to process the acquired images for single and double exponential decays. Measurement of donor lifetime in two different conditions allowed us to calculate accurately the distance between the interacting proteins. We used this approach to quantify the dimerization of the transcription factor CAATT/enhancer binding protein alpha in living pituitary cells. The one‐ and two‐component analysis of the donor molecule lifetime in the presence of acceptor demonstrates the distance distribution between interacting proteins.
Hydrogen peroxide‐mediated phosphorylation of ERK1/2,  Akt/PKB and JNK in cortical neurones: dependence  on Ca2+ and PI3‐kinase
Authors: Crossthwaite Andrew J. , Hasan Sumaera , Williams Robert J.
Published: March 2003

Primary cortical neurones exposed to an oxidative insult in the form of hydrogen peroxide (H2O2) for 30 min showed a concentration‐dependent increase in oxidative stress followed by␣a␣delayed NMDA receptor‐dependent cell death measured␣24 h later. Extracellular signal‐regulated protein kinase (ERK1/2), c‐jun N‐terminal kinase (JNK) and the kinase Akt/PKB may regulate neuronal viability in response to oxidative insults. Using phospho‐specific antibodies, a 15‐min stimulation of neurones with H2O2 (100 µm−1 mm) produced a concentration‐dependent phosphorylation of ERK1/2 and Akt/PKB that was partly dependent on extracellular Ca2+ and phosphatidylinositol 3‐kinase (PI3‐K). Higher concentrations of H2O2 (1 mm) also stimulated a phosphorylation of JNK which was totally dependent on extracellular Ca2+ but not PI3‐K. H2O2‐induced phosphorylation of ERK1/2, Akt/PKB or JNK were unaffected by the NMDA channel blocker MK801. Blocking ERK1/2 activation with the upstream inhibitor U0126 (10 µm) enhanced H2O2‐induced (100–300 µm range) neurotoxicity and inhibited H2O2‐mediated phosphorylation of the cyclic AMP regulatory binding protein (CREB), suggesting that ERK1/2 signals to survival under these conditions. At higher concentrations (mm), H2O2‐stimulated a phosphorylation of c‐jun. It is likely, therefore, that subjecting neurones to moderate oxidative‐stress recruits pro‐survival signals to CREB but during severe oxidative stress pro‐death signals through JNK and c‐jun are dominant.
Dietary folate deficiency and elevated homocysteine levels endanger dopaminergic neurons in models of Parkinson's disease
Authors: Duan Wenzhen , Ladenheim Bruce , Cutler Roy G. , Kruman Inna I. , Cadet Jean Lud , Mattson Mark P.
Published: March 2003

Although the cause of Parkinson's disease (PD) is unknown, data suggest roles for environmental factors that may sensitize dopaminergic neurons to age‐related dysfunction and death. Based upon epidemiological data suggesting roles for dietary factors in PD and other age‐related neurodegenerative disorders, we tested the hypothesis that dietary folate can modify vulnerability of dopaminergic neurons to dysfunction and death in a mouse model of PD. We report that dietary folate deficiency sensitizes mice to MPTP‐induced PD‐like pathology and motor dysfunction. Mice on a folate‐deficient diet exhibit elevated levels of plasma homocysteine. When infused directly into either the substantia nigra or striatum, homocysteine exacerbates MPTP‐induced dopamine depletion, neuronal degeneration and motor dysfunction. Homocysteine exacerbates oxidative stress, mitochondrial dysfunction and apoptosis in human dopaminergic cells exposed to the pesticide rotenone or the pro‐oxidant Fe2+. The adverse effects of homocysteine on dopaminergic cells is ameliorated by administration of the antioxidant uric acid and by an inhibitor of poly (ADP‐ribose) polymerase. The ability of folate deficiency and elevated homocysteine levels to sensitize dopaminergic neurons to environmental toxins suggests a mechanism whereby dietary folate may influence risk for PD.
Cholesterol‐dependent modulation of dendrite outgrowth  and microtubule stability in cultured neurons
Authors: Fan Qi‐Wen , Yu Wei , Gong Jian‐Sheng , Zou Kun , Sawamura Naoya , Senda Takao , Yanagisawa Katsuhiko , Michikawa Makoto
Published: March 2003

Microtubule‐associated protein 2 (MAP2) is a neuron‐specific cytoskeletal protein enriched in dendrites and cell bodies. MAP2 regulates microtubule stability in a phosphorylation‐dependent manner, which has been implicated in dendrite outgrowth and branching. We have previously reported that cholesterol deficiency causes tau phosphorylation and microtubule depolymerization in axons (Fan et al. 2001). To investigate whether cholesterol also modulates microtubule stability in dendrites by modulating MAP2 phosphorylation, we examined the effect of compactin, a 3‐hydroxy‐3‐methylglutaryl coenzyme A (HMG‐CoA) reductase inhibitor, and TU‐2078 (TU), a squalene epoxidase inhibitor, on these parameters using cultured neurons. We have found that cholesterol deficiency induced by compactin and TU, inhibited dendrite outgrowth, but not of axons, and attenuated axonal branching. Dephosphorylation of MAP2 and microtubule depolymerization accompanied these alterations. The amount of protein phosphatase 2 A (PP2A) and its activity in association with microtubules were decreased, while those unbound to microtubules were increased. The synthesized ceramide levels and the total ceramide content were increased in these cholesterol‐deficient neurons. These alterations caused by compactin were prevented by concurrent treatment of cultured neurons with β‐migrating very‐low‐density lipoproteins (β‐VLDL) or cholesterol. Taken together, we propose that cholesterol‐deficiency causes a selective inhibition of dendrite outgrowth due to the decreased stability of microtubules as a result of inhibition of MAP2 phosphorylation.
Modulation of Aβ peptides by estrogen in mouse models
Authors: Zheng H. , Xu H. , Uljon S. N. , Gross R. , Hardy K. , Gaynor J. , Lafrancois J. , Simpkins J. , Refolo L. M. , Petanceska S. , Wang R. , Duff K.
Published: March 2003

Clinical studies have shown that estrogen deprivation through menopause is a risk factor in both the initiation and progression of Alzheimer's disease (AD) and that estrogen replacement therapy may be protective. One of the major pathological features in the human AD brain is the senile plaque, a proteinaceous structure composed mainly of heterogeneous peptides collectively known as A‐beta (Aβ). In vitro studies have linked estrogen with Aβ modulation, suggesting that one‐way that estrogen depletion at menopause may exacerbate the features of AD is through Aβ accumulation. To test this, two studies were performed on transgenic models of amyloidosis. Firstly, transgenic mice without detectable amyloid aggregates were subjected to ovariectomy and estradiol supplementation, and Aβ levels were assessed. Secondly, the effects of estrogen modulation were assessed in mice at an age when plaques would be forming initially. Overall, Aβ levels were higher in estrogen‐deprived mice than intact mice, and this effect could be reversed through the administration of estradiol. These data suggest that, in vivo, estrogen depletion leads to the accumulation of Aβ in the CNS, which can be reversed through replacement of estradiol. These results provide evidence that post‐menopausal estrogen depletion may be linked to an increased risk of AD through Aβ modulation.
Overexpression of c‐Fos is sufficient to stimulate tyrosine hydroxylase (TH) gene transcription in rat pheochromocytoma  PC18 cells
Authors: Sun Baoyong , Tank A. William
Published: March 2003

The AP1 site within the tyrosine hydroxylase gene proximal promoter is essential for the response of the gene to numerous stimuli. Stimulation of this gene is often associated with induction of the AP1 transcription factor, c‐Fos. However, many stimuli activate or induce multiple transcription factors that interact with this AP1 site or other sites within the gene's proximal promoter. Hence, it remains unclear whether c‐Fos induction by itself is sufficient to stimulate the tyrosine hydroxylase gene. In this study we produce rat pheochromocytoma PC18 cells that overexpress c‐Fos under control of the tet‐inducible system. We demonstrate that induction of c‐Fos leads to dramatic stimulation of tyrosine hydroxylase gene transcription rate measured using nuclear run‐on assays. This stimulation is closely associated quantitatively with the induction of c‐Fos and does not apparently require phosphorylation of c‐Fos. The response is partially dependent on the AP1 site within the tyrosine hydroxylase proximal promoter. However, the response of the proximal promoter to c‐Fos induction is relatively small compared with that of the endogenous gene. Consequently, our results suggest that c‐Fos exerts its influence on the tyrosine hydroxylase gene via multiple mechanisms that are dependent and independent of the proximal promoter AP1 site.
Dopamine D4 receptors are heterogeneously distributed in the striosomes/matrix compartments of the striatum
Authors: Rivera Alicia , Cuéllar Beatriz , Girón Francisco J. , Grandy David K. , De La Calle Adelaida , Moratalla Rosario
Published: March 2003

Two important aspects of striatal function, exploratory behaviour and motor co‐ordination, require the integrity of the dopamine D4 receptor subtype. These receptors are also implicated in the pathophysiology of certain neuropsychiatric disorders. However, the distribution of D4 receptors in the striatum has not yet been described and this situation impairs our understanding of the anatomical substrate in which D4 receptors function. We developed a D4 receptor‐specific anti‐body that has permitted us to investigate the regional and cellular localization of the receptor in the neostriatum of the rat, mouse, cat and monkey. The subcellular distribution and the synaptic organization of this receptor were also determined in the rat striatum. We found moderate levels of D4 receptor expression in the caudoputamen and lower levels in the nucleus accumbens. These receptors were expressed in cell bodies and in the neuropil and were heterogeneously distributed among different striatal compartments, being more abundant in striosomes than in the matrix. At the subcellular level, the receptor immunoreactivity was mainly localized to dendritic shafts and spines. The prominent immunoreactivity observed in the striosomes indicates that integrative processes involved in D4‐mediated limbic behaviours occurs through the striosomes rather than accumbens, whereas the motor behaviour is based in the striatal matrix.
Essential role of caspase‐11 in activation‐induced cell death of rat astrocytes
Authors: Suk Kyoungho , Kim Sun Yeou , Kim Hocheol
Published: March 2003

We have previously shown that rat astrocytes undergo apoptosis upon inflammatory activation. Nitric oxide (NO) produced by activated astrocytes was the major cytotoxic mediator in this type of autoregulatory apoptosis. However, an inhibitor of nitric oxide synthase did not completely block the apoptosis of activated astrocytes, suggesting the presence of other apoptotic pathways. Here, we present evidence that caspase‐11 is an essential molecule in NO‐independent apoptotic pathway of activated astrocytes. Inflammatory activation (lipopolysaccharide, interferon‐γ, and tumor necrosis factor‐α treatment) of rat astrocyte cultures and C6 glioma cells led to the induction of caspase‐11 followed by activation of caspases‐11, ‐1, and ‐3. In contrast, NO donors induced activation of caspase‐3 only. Inactivation of caspase‐11 by the transfection of dominant negative mutant or treatment with the caspase inhibitors rendered the astrocytes partially resistant to the apoptosis following inflammatory activation, but not NO donor exposure. These results indicate that inflammatory stimuli not only induce the production of cytotoxic NO, but also␣initiate NO‐independent apoptotic pathway through the induction of caspase‐11 expression.
Generation of reactive oxygen species by the mitochondrial electron transport chain
Authors: Liu Yuanbin , Fiskum Gary , Schubert David
Published: March 2003

Generation of reactive oxygen species (ROS) by the mitochondrial electron transport chain (ETC), which is composed of four multiprotein complexes named complex I–IV, is believed to be important in the aging process and in the pathogenesis of neurodegenerative diseases such as Parkinson's disease. Previous studies have identified the ubiquinone of complex III and an unknown component of complex I as the major sites of ROS generation. Here we show that the physiologically relevant ROS generation supported by the complex II substrate succinate occurs at the flavin mononucleotide group (FMN) of complex I through reversed electron transfer, not at the ubiquinone of complex III as commonly believed. Indirect evidence indicates that the unknown ROS‐generating site within complex I is also likely to be the FMN group. It is therefore suggested that the major physiologically and pathologically relevant ROS‐generating site in mitochondria is limited to the FMN group of complex I. These new insights clarify an elusive target for intervening mitochondrial ROS‐related processes or diseases.
ELISA analysis of β‐secretase cleavage of the Swedish amyloid precursor protein in the secretory and endocytic pathways
Authors: Steinhilb Michelle L. , Turner R. Scott , Gaut James R.
Published: March 2003

Limiting beta amyloid (Aβ) production could become an important therapeutic target in Alzheimer's disease (AD). Aβ is derived by the sequential cleavage of amyloid precursor protein (APP) by β‐ and γ‐secretases. A double missense mutation in APP found in a Swedish pedigree (APPsw) elevates Aβ40 and Aβ42 production. Aβ production and, therefore, β‐secretase cleavage of APPsw reportedly occur in the endoplasmic reticulum (ER), Golgi and endocytic compartments. However, the relative contribution of β‐secretase cleavage occurring in each compartment has not been determined. Experiments described here use a novel ELISA to measure the β‐cleaved product, APPswβ. Using this ELISA, we provide new information regarding the relative amount of β‐secretase cleavage of APPsw that occurs in secretory and endocytic pathways. Using a dilysine retrieval motif to retain APPsw in the ER, we discovered that less than 15% of the β‐secretase cleavage was still detected. Experiments utilizing endocytosis‐impaired mutants of APPsw revealed that little or no β‐secretase cleavage of APPsw appears to take place through endocytosis. Surprisingly, deletion of the entire cytoplasmic tail increased both APPswβ and Aβ secretion, suggesting that protein interactions with this region normally impede β‐secretase cleavage. These results suggest that APPsw is cleaved by β‐secretase late in the secretory pathway.
Modulation of cannabinoid agonist binding by 5‐HT in the rat cerebellum
Authors: Devlin Mark G. , Christopoulos Arthur
Published: March 2003

Cross‐talk between cannabinoid CB1 and serotonin 5‐HT receptors in rat cerebellar membranes was investigated using radioligand binding. In competition against the CB1 antagonist, [3H]SR141716A, the agonist, WIN 55,212‐2 yielded a biphasic isotherm. The majority of binding was to a high‐affinity state that was significantly reduced by the GTP analogue, Gpp(NH)p. Interestingly, 5‐HT enhanced the high‐affinity binding constant of WIN 55,212‐2 while attenuating the proportion of high‐affinity binding. 5‐HT also significantly reduced the proportion of high‐affinity binding of the cannabinoid agonist, HU 210, but had no effect on the agonist, CP 55,940. The effect of 5‐HT on WIN 55,212‐2 binding was inhibited by the 5‐HT2 receptor antagonist ritanserin as well as Gpp(NH)p, suggesting a dependence on the 5‐HT2 receptor and on G protein‐receptor interactions, respectively. Subsequent [3H]WIN 55,212‐2 dissociation kinetic experiments revealed that 5‐HT promoted a slower‐dissociating species of radiolabelled agonist‐receptor complex. Our findings support a membrane‐delimited cross‐talk between two G protein‐coupled receptors that are co‐localized in certain cells of the central nervous system. Intriguingly, the cannabinoid agonist dependence of the 5‐HT modulatory effect suggests that agonist‐specific conformations of the CB1 receptor may also be important in determining the extent of this cross‐talk.
In situ13CO2 pulse‐labelling of upland grassland demonstrates a rapid pathway of carbon flux from arbuscular mycorrhizal mycelia to the soil
Authors: Johnson D. , Leake J. R. , Ostle N. , Ineson P. , Read D. J.
Published: March 2003

The flux of pulse‐derived 13C from upland pasture plants to the external mycelium of their arbuscular mycorrhizal (AM) symbionts was traced and quantified over a 7‐d post‐labelling period.

 Mesh cores, which allowed in‐growth of native AM mycelium but were impenetrable to roots, were inserted into unlimed and limed plots and the surrounding vegetation was exposed to 13CO2 at ambient CO2 concentrations.

 Release of 13CO2 from cores colonized by AM mycelium peaked 9–14 h after labelling and declined within 24 h after severance of mycelial connections to roots. Between 5 and 8% of carbon lost by plants was respired by AM mycelium over the first 21 h after labelling. Liming increased the amount of carbon fixed by plants and subsequently allocated to fine roots and AM mycelium.

 The results demonstrate for the first time under field conditions that AM mycelia provide a rapid and important pathway of carbon flux from plants to the soil and atmosphere.
Effects of arbuscular mycorrhizal fungi on severity of root rot of bananas caused byCylindrocladium spathiphylli
Authors: Declerck S. , Risede J. M. , Rufyikiri G. , Delvaux B.
Published: March 2003

The interaction between four arbuscular mycorrhizal (AM) fungi,Glomussp.,G. proliferum,G. intraradicesandG. versiforme, and the root‐rot fungusCylindrocladium spathiphylli, and subsequent effects on growth and phosphorus nutrition of banana (Musa acuminata, AAA, cv. Grande Naine) were investigated under glasshouse conditions. Overall, root infection byC. spathiphyllireduced the growth of banana plants, but preinoculation with AM fungi significantly attenuated this detrimental effect. Lower disease severity, stimulation of growth and increase of shoot P content were observed for the plants inoculated with one of the four AM fungi.Glomussp. andG. proliferuminduced the largest increase in growth parameters and shoot P content as compared toG. intraradicesandG. versiforme, in the presence as well as in the absence ofC. spathiphylli. Root damage caused byC. spathiphylliwas decreased in the presence of AM fungi, but the inoculation of mycorrhizal plants withC. spathiphyllialso decreased the intensity of AM fungal root colonization, indicating a clear interaction between the two organisms.
A Propeller Thrust and Torque Dynamometer for Wind Tunnel Models
Authors: Molland A. F. , Turnock S. R.
Published: March 2003

The design, construction and calibration of a propeller thrust and torque dynamometer is described. The dynamometer was constructed primarily for the testing of model ship propellers when working upstream of a rudder. An outline of the specialised design requirements is given. The basic design concepts are described together with the reasons for the choice of flexures and their dimensions, strain gauges, circuits, bridge voltages and instrumentation. A brief description of the calibration process is given and the calibration results are described and discussed. It was found that there were no interactions between the components, a satisfactory overall measuring accuracy was achieved and the dynamometer had performed well in service. It is concluded that the overall design approach, concept and design details were satisfactory and suitable for this particular application.
Halogen contents of eclogite facies fluid inclusions and minerals: Caledonides, western Norway
Authors: Svensen H. , Jamtveit B. , Banks D. A. , Austrheim H.
Published: March 2003

Primary multiphase brine fluid inclusions in omphacite and garnet from low‐ to medium‐temperature eclogites have been analysed for Cl, Br, I, F, Li and SO4. Halogen contents and ratios provide information about trapped lower crustal fluids, even though the major element (Na, K, Ca) contents of inclusion fluids have been modified by fluid–mineral interactions and (step‐) daughter‐crystal formation after trapping. Halogens in the inclusion fluids were analysed with crush–leach techniques. Cl/Br and Cl/I mass ratios of eclogite fluids are in the range 31–395 and 5000–33 000, respectively. Most fluids have a Cl/Br ratio lower than modern seawater and a Cl/I ratio one order of magnitude lower than modern seawater. Fluids with the lowest Cl/Br and highest Cl/I ratios come from an eclogite that formed by hydration of granulite facies rocks, and may indicate that Br and I are fractionated into hydrous minerals. Reconstructions indicate that the inclusion fluids originally contained 500–4000 ppm Br, 1–14 ppm I and 33–438 ppm Li. Electron microprobe analyses of eclogite facies amphibole, biotite, phengite and apatite indicate that F and Cl fractionate most strongly between phengite (F/Cl mass ratio of 1469 ± 1048) and fluid (F/Cl mass ratio of 0.008), and the least between amphibole and fluid. The chemical evolution of Cl and Br in pore fluids during hydration reactions is in many ways analogous to Cl and Br in seawater during evaporation: the Cl/Br ratio remains constant until the aH2O value is sufficiently lowered for Cl to be removed from solution by incorporation into hydrous minerals.
Heterogeneous growth of cordierite in low P/T Tsukuba metamorphic rocks from central Japan
Authors: Miyazaki K.
Published: March 2003

This paper examines the spatial statistics of matrix minerals and complex patterned cordierite porphyroblasts in the low‐pressure, high‐temperature (low P/T) Tsukuba metamorphic rocks from central Japan, using a density correlation function. The cordierite‐producing reaction is sillimanite + biotite + quartz = K‐feldspar + cordierite + water. The density correlation function shows that quartz is distributed randomly. However, the density correlation functions of biotite, plagioclase and K‐feldspar show that their spatial distributions are clearly affected by the formation of cordierite porphyroblasts. These observations suggest that cordierite growth occurred through a selective growth mechanism: quartz adjacent to cordierite has a tendency to prevent the growth of cordierite, whereas other matrix minerals adjacent to cordierite have a tendency to enhance the growth of cordierite. The density correlation functions of complex patterned cordierite porphyroblasts show power‐law behaviour. A selective growth mechanism alone cannot explain the origin of the power‐law behaviour. Comparison of the morphology and fractal dimension of cordierite with two‐dimensional sections from a three‐dimensional diffusion‐limited aggregation (DLA) suggests that the formation of cordierite porphyroblasts can be modelled as a DLA process. DLA is the simple statistical model for the universal fractal pattern developed in a macroscopic diffusion field. Diffusion‐controlled growth interacting with a random field is essential to the formation of a DLA‐like pattern. The selective growth mechanism will provide a random noise for the growth of cordierite due to random distribution of quartz. Therefore, a selective growth mechanism coupled with diffusion‐controlled growth is proposed to explain the power‐law behaviour of the density correlation function of complex patterned cordierite. The results in this paper suggest that not only the growth kinetics but also the spatial distribution of matrix minerals affect the progress of the metamorphic reaction and pattern formation of metamorphic rocks.
Calculation of partial melting equilibria in the system Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O (NCKFMASH)
Authors: White R. W. , Powell R. , Holland T. J. B.
Published: March 2003

A thermodynamic model for haplogranitic melts in the system Na2O–CaO–K2O–Al2O3–SiO2–H2O (NCKASH) is extended by the addition of FeO and MgO, with the data for the additional end‐members of the liquid incorporated in the
Holland & Powell (1998) internally consistent thermodynamic dataset. The resulting dataset, with the software

thermocalc, is then used to calculate melting relationships for metapelitic rock compositions. The main forms for this are P–T and T–X pseudosections calculated for particular rock compositions and composition ranges. The relationships in these full‐system pseudosections are controlled by the low‐variance equilibria in subsystems of NCKFMASH. In particular, the solidus relationships are controlled by the solidus relationships in NKASH, and the ferromagnesian mineral relationships are controlled by those in KFMASH. However, calculations in NCKFMASH allow the relationships between the common metapelitic minerals and silicate melt to be determined. In particular, the production of silicate melt and melt loss from such rocks allow observations to be made about the processes involved in producing granulite facies rocks, particularly relating to open‐system behaviour of rocks under high‐grade conditions.
Diffusion control of garnet growth, Harpswell Neck, Maine, USA
Authors: Spear F. S. , Daniel C. G.
Published: March 2003

A detailed analysis of chemical zoning in two garnet crystals from Harpswell Neck, Maine, forms the basis of an interpretation of garnet nucleation and growth mechanisms. Garnet apparently nucleates initially on crenulations of mica and chlorite and quickly overgrows the entire crenulation, giving rise to complex two‐dimensional zoning patterns depending on the orientation of the thin section cut. Contours of Ca zoning cross those of Mn, Fe and Mg, indicating a lack of equilibrium among these major garnet constituents. Zoning of Fe, Mg and Mn is interpreted to reflect equilibrium with the rock matrix, whereas Ca zoning is interpreted to be controlled by diffusive transport between the matrix and the growing crystal.

Image analysis reveals that the growth of garnet is more rapid along triple‐grain intersections than along double‐grain boundaries. Moreover, different minerals are replaced by garnet at different rates. The relative rate of replacement by garnet along double‐grain boundaries is ordered as muscovite > chlorite > plagioclase > quartz. Flux calculations reveal that replacement is limited by diffusion of Si along double‐grain boundaries to or from the local reaction site. It is concluded that multiple diffusive pathways control the bulk replacement of the rock matrix by garnet, with Si and Al transport being rate limiting in these samples.
Melt segregation in the continental crust: distribution and movement of melt in anatectic rocks
Authors: Sawyer E. W.
Published: March 2003

The grain‐ and outcrop‐scale distribution of melt has been mapped in anatectic rocks from regional and contact metamorphic environments and used to infer melt movement paths. At the grain scale, anatectic melt is pervasively distributed in the grain boundaries and in small pools; consequently, most melt is located parallel to the principal fabric in the rock, typically a foliation. Short, branched arrays of linked, melt‐bearing grain boundaries connect melt‐depleted parts of the matrix to diffuse zones of melt accumulation (protoleucosomes), where magmatic flow and alignment of euhedral crystals grown from the melt developed.

The distribution of melt (leucosome) and residual rocks (normally melanocratic) in outcrop provides different, but complementary, information. The residual rocks show where the melt came from, and the leucosomes preserve some of the channels through which the melt moved, or sites where it pooled. Different stages of the melt segregation process are recorded in the leucosome–melanosome arrays. Regions where melting and segregation had just begun when crystallization occurred are characterized by short arrays of thin, branching leucosomes with little melanosome. A more advanced stage of melting and segregation is marked by the development of residual rocks around extensive, branched leucosome arrays, generally oriented along the foliation or melting layer. Places where melting had stopped, or slowed down, before crystallization began are marked by a high ratio of melanosome to leucosome; because most of the melt has drained away, very few leucosomes remain to mark the melt escape path — this is common in melt‐depleted granulite terranes. Many migmatites contain abundant leucosomes oriented parallel to the foliation; mostly, these represent places where foliation planes dilated and melt drained from the matrix via the branched grain boundary and larger branched melt channel (leucosome) arrays collected. Melt collected in the foliation planes was partially, or fully, expelled later, when discordant leucosomes formed. Leucosomes (or veins) oriented at high angles to the foliation/layering formed last and commonly lack melanocratic borders; hence they were not involved in draining the matrix of the melting layer. Discordant leucosomes represent the channels through which melt flowed out of the melting layer.
Metastability of granulites and processes of eclogitisation in the UHP region of western Norway
Authors: Wain A. L. , Waters D. J. , Austrheim H.
Published: March 2003

The Flatraket Complex, a granulite facies low strain enclave within the Western Gneiss Region, provides an excellent example of metastability of plagioclase‐bearing assemblages under eclogite facies conditions. Coesite eclogites are found <200 m structurally above and <1 km below the Flatraket Complex, and are separated from it by amphibolite facies gneisses related to pervasive late‐orogenic deformation and overprinting. Granulites within the Flatraket Complex equilibrated at 9–11 kbar, 700–800°C. These predate eclogite facies metamorphism and were preserved metastably in dry undeformed zones under eclogite facies conditions. Approximately 5% of the complex was transformed to eclogite in zones of fluid infiltration and deformation, which were focused along lithological contacts in the margin of the complex. Eclogitisation proceeded by domainal re‐equilibration and disequilibrium breakdown of plagioclase by predominantly hydration reactions. Both hydration and anhydrous plagioclase breakdown reactions were kinetically linked to input of fluid. More pervasive hydration of the complex occurred during exhumation, with fluid infiltration linked to dehydration of external gneisses. Eclogite facies shear zones within the complex equilibrated at 20–23 kbar, 650–800°C, consistent with the lack of coesite and with the equilibration conditions of external HP eclogites. If the complex experienced pressures equivalent to those of nearby coesite eclogites (> 28 kbar), unprecedented metastability of plagioclase and quartz is implied. Alternatively, a tectonic break exists between the Flatraket Complex and UHP eclogites, supporting the concept of a tectonic boundary to the UHP zone of the Western Gneiss Region. The distribution of eclogite and amphibolite facies metamorphic overprints demonstrates that the reactivity of the crust during deep burial and exhumation is strongly controlled by fluid availability, and is a function of the protolith.
Petrology, geochronology, and tectonics of shear zones in the Zermatt–Saas and Combin zones of the Western Alps
Authors: Cartwright I. , Barnicoat A. C.
Published: March 2003

Metre to tens‐of‐metre wide, steeply dipping, greenschist facies shear zones that cut blueschists and eclogites of the Combin and Zermatt–Saas Zones at Täschalp and in adjacent areas of the western Alps were sites of extensive recrystallization driven by fluid flow and deformation. Rb–Sr data imply that these shear zones formed at 42–37 Ma with a systematic younging of structures northward toward, and into, the hangingwall of the Mischabel Structure. Shearing commenced at 400–475 °C and 400–500 MPa and continued as pressures and temperatures fell to 300–350 °C and 300–350 MPa. Individual shear zones were active for 2–3 Myr with later lower grade stages of shearing concentrated into narrow zones. Fluids that infiltrated the shear zones were water rich (XH2O > 0.9). Alteration zones around albite veins and at the margins of serpentinite bodies are penecontemporaneous with these shear zones and formed at approximately the same conditions. The eclogites were exhumed from c. 64 km at 44 Ma to 14–16 km at 42–41 Ma implying exhumation rates of 2–5 cm yr−1. Rapid exhumation was probably achieved by extension aided by buoyancy, following subduction of continental crust, and rapid erosion. The shear zones form part of a regional‐scale extensional system responsible for a significant portion of the exhumation of the subducted oceanic crust.
Determining the impact of health library services on patient care: a review of the literature
Authors: O’Connor Patrick
Published: March 2003

The impact of health library information has been studied in a number of settings and populations. This review examines both the methods employed and the outcomes reported in a series of impact studies conducted in four countries since the late 1980’s. It demonstrates that health library information can affect patient care outcomes in various ways and has high cognitive and clinical value in diagnosing and treating patients. But there remains no agreed technique or methodology for determining the level of this impact. In many cases evaluation of the health library’s impact will be located within a central process of evaluation of the greater organization to which the library belongs. Consequently, local ad hoc evaluation is rarely reported outside an organization. The author considers the question of whether it is worthwhile doing an impact study and what form it might take. The author concludes by identifying seminal papers on the topic.
e‐ducation: research and practice
Authors: Nulden U.
Published: March 2003

Abstract This paper proposes an integrated approach for information technology in an educational context. The paper suggests a framework for the design of computer assisted learning activities — e‐ducation. The framework captures three contemporary interrelated aspects of teaching and learning and is more pedagogical than it is analytical. The three aspects covered in the e‐ducation framework are electronic, engaged and empowered. An implementation of the framework is used to illustrate how e‐ducation can be applied in educational research and practice. The paper concludes that the e‐ducation framework contributes to both educational research and educational practice.
Attitudes affecting college students' preferences for distance learning
Authors: Katz Y. J.
Published: March 2003

Abstract Empirical studies that have examined psychological aspects of the use of Information and Communication Technology (ICT) have indicated that certain psychological attitudes of students towards the use of ICT are of paramount importance when evaluating the effective use of distance learning approaches to instruction and learning. Distance learning at the tertiary level, through the medium of ICT, is seemingly affected by the same psychological attitudes that are known to be related to other successful ICT applications to learning and instruction. In the present study the relationship between two distance learning ICT‐based configurations were examined. The results indicate that psychological attitudes held by students differentially facilitate efficient use of distance learning approaches. Satisfaction with learning, level of control of the learning process, and study motivation for distance learning are all positively related to the students' preferences for structured distance learning, whereas independence in learning is positively connected to students' preferences for the more open Internet functionality.
A virtual reality application for geometry classes
Authors: Song K.S. , Lee W.Y.
Published: March 2003

Abstract  In communicating information about geometric figures, one drawing may be worth many hundreds of words and, therefore, visualisation aids for complicated three‐dimensional (3‐D) solid objects are very helpful for both teacher and students. This paper describes the use of the Virtual Reality Modelling Language (VRML) to visualise 3‐D objects for middle school geometry classes in a networked environment and shows its usefulness for both teacher and students. In class, the teachers use VRML objects retrieved from their server and students are allowed to explore these objects accessing the teachers' server via the world‐wide web. A comparison of the test results from VRML‐based geometry classes and traditional classes, that solely depend on verbal explanation with paper and pencil, show that the application of VRML‐based 3‐D objects has a positive affect on students' learning of geometric topics.
Exploring the mechanisms through which computers contribute to learning
Authors: Karasavvidis I. , Pieters J.M. , Plomp T.
Published: March 2003

Abstract Even though it has been established that the incorporation of computers into the teaching and learning process enhances student performance, the underlying mechanisms through which this is accomplished have been largely unexplored. The present study aims to shed light on this issue. Two groups of 10 secondary school students were tutored by their geography teacher in how to solve correlational problems. Students in the one group used paper and pencil while students in the other group used a computer spreadsheet. All tutorials were videotaped, transcribed verbatim, and subsequently all transcripts were segmented and coded. The mean frequencies for teacher and student behaviours between the two conditions were then compared. Results indicated that teacher behaviour in the two conditions differed in terms of error feedback, factual and conceptual questions asked, regulation of students, and task management. Regarding student behaviours, the findings showed that the two conditions differed in terms of task engagement, goal setting, and explanations given. On the basis of these findings the issue of mechanisms is discussed and three main implications for the teaching and learning practice are drawn.
The effects of collaborative teamwork on secondary science
Authors: Chiu C.H.
Published: March 2003

Abstract This study investigated whether a collaborative team setting benefits secondary science learning in a network supported environment. Ninety‐four 10th grade (ages 16‐17) girl students, in two Earth Science classes in Taiwan, were assigned to two settings: collaborative teams and individuals. The students' scientific process skill development, attitude toward school science and attitude toward using and learning about computers were compared. It was found that both groups showed significant improvements in skills and attitudes. However, the students in the team situation did not demonstrate significantly better skills or attitudes than the students in the individual situation.
Promoting creative thinking through the use of ICT
Authors: Wheeler S. , Waite S.J. , Bromfield C.
Published: March 2003

Abstract A great deal has been written about the use of web‐based technologies such as the Internet in promoting learning in education. In schools, research has focused primarily on social interaction and group work, student achievement levels and curriculum development. Very little study seems to have been brought to bear upon the promotion of creative thinking by the use of online technologies, and this paper attempts to contribute to this field of study. This paper reports on a pilot study which has investigated the creative impact of information and communication technology (ICT) in a rural primary school in South‐west England. The school is unique because it provides a personal networked computer for each of its 41 Year 6 students (aged 10–11 years). A small group of students were interviewed about the learning activities they engaged in over the year, and this paper reports on initial findings with a special emphasis on creative working and thinking (n = 6). A model of creativity is presented with three discrete but related modes of activity — problem solving, creative cognition, and social interaction. The paper provides new findings about the nature of creativity in the context of computer based learning environments.
Factors influencing the abundance of Japanese encephalitis vectors in ricefields in India – I. Abiotic
Authors: Sunish I. P. , Reuben R.
Published: March 2003

Abstract. Mosquitoes of the Culex vishnui subgroup (Diptera: Culicidae) are the most important vectors of Japanese encephalitis (JE) and ricefields are their most productive breeding sites in south India, where predominant species of this subgroup are Culex tritaeniorhynchus Giles, Cx. pseudovishnui Colless and Cx. vishnui Theobald sensu stricto. The relationship of 13 abiotic variables with the abundance of Cx. vishnui subgroup immatures was investigated in transplanted rice fields for 3 years (1991–94) covering three different crop seasons. The results from the multiple regression model suggested paddy height (– ve), water temperature (+ ve), dissolved oxygen (– ve), ammonia nitrogen (– ve) and nitrate nitrogen (+ ve) to be the best predictor variables associated with the immature abundance, nearly always consistent in their effects within and between seasons. Application of synthetic nitrogenous fertilizers to the rice fields was followed by a rise in concentration of ammonia nitrogen and a subsequent increase in nitrate nitrogen level in the rice field water, during which an increase in the density of larval instars was observed.