bluuebunny/crossref_metadata_2025_split huggingface dataset:
Petroleum infiltration of high‐grade basement, South Norway: Pressure‐Temperature‐time‐composition (P–T–t–X) constraints
Authors: Munz I. A. , Yardley B. W. D. , Gleeson S. A. 
Published: March 2003

AbstractFluid inclusion data provide pressure–temperature–time–composition (P–T–t–X) constraints for an episode of petroleum infiltration of the crystalline basement in South Norway. Petroleum inclusions associated with pyrobitumen occur in postmetamorphic quartz veins in the Modum Complex. Three groups of fluid compositions have been shown, ranging from CH4 ± CO2 to condensates with alkanes up to C15. The range in fluid composition is a result of petroleum decomposition at high temperature. Globular and massive pyrobitumen occurs in the quartz veins or in associated vein systems. Reflectance (%Rm) measurements of 3.20–3.35 correspond to a maximum temperature of 207–214°C for the pyrobitumen associated with group II and III inclusions. Geothermometry of chlorites included in the quartz show results of 226–231°C. Pressure conditions of trapping for all three groups of inclusion fluids have been estimated to 520–985 bar at 220°C. The pressure range is probably a result of fluctuations caused by repeated fracture opening and sealing due to seismic activity coupled with mineral growth. A lack of systematic textural relationships between the three groups of inclusions and similar pressure–temperature estimates for all fluid types indicate trapping at similar times and a process of rapid change. Fluid migration in fractures from an overlying, overpressured sedimentary basin into a dry, crystalline basement best explains the observed P–T–t–X constraints.
The role of patch area and habitat diversity in explaining native plant species richness in disturbed suburban forest patches in northern Belgium
Authors: Honnay O. , Endels P. , Vereecken H. , Hermy M. 
Published: March 2003

SummaryRelatively easy measurable patch characteristics (especially habitat diversity measures) have proven to be valuable indicators of forest plant species richness in forest fragments of relatively undisturbed areas. Urban and suburban forest patches, however, are characterized by a specific landscape ecological context implying that specific processes may influence ecosystem functioning and hence that other abiotic indicators for plant diversity are more appropriate. We studied the relation between functional ecological plant species groups and suburban forest patch characteristics such as patch area, habitat diversity and isolation. Some components of species richness were related to the isolation of the patches. In contrast to previous similar large‐scale fragmentation studies in more rural areas, further results stressed the overwhelming importance of patch area relative to habitat variables in determining species richness. This suggests (1) the occurrence of density‐dependent species extinction processes in small forest patches; or (2) the existence of external deterministic factors which put a major constraint on species richness in small patches. We tend to support the latter hypothesis and propose forest disturbance and associated black cherry (Prunus serotina Ehrh.) invasion as such a possible external factor. Small forest patches may be more sensitive to disturbance and biological invasion due to various reasons. Hence large forest patches are to be preferred for plant conservation in the suburban area.
Species richness and endemism of plant and bird communities along two gradients of elevation, humidity and land use in the Bolivian Andes
Authors: Kessler Michael , Herzog Sebastian K. , Fjeldså Jon , Bach Kerstin 
Published: March 2003

Abstract.We studied the patterns of species richness and range–size rarity (as a measure of endemism) of two plant groups (Pteridophyta, Bromeliaceae) and birds along two gradients of elevation, humidity and human land use in a forested Andean valley. Both transects covered the transition from an arid valley bottom through a cloud forest zone to relictual high‐elevation Polylepis forest, but transects differed in overall precipitation. Plants were surveyed in 88 plots of 400 m2 each, while birds were detected primarily through visual observations and tape recordings over areas of 0.3–1.5 km2. Global range sizes of all species were mapped on 1°‐grids and range‐size rarity was calculated as the mean inverse range size of all species recorded in elevational steps of 200 m. Patterns of species richness and range–size rarity were mainly unrelated between and within study groups. Monotonic increases and decreases and hump‐shaped patterns were observed for species richness as well as range–size rarity. Several of these patterns can be interpreted in the light of the ecological requirements of each taxonomic group, e.g. dependence of fern species richness on humidity or of bird richness on habitat complexity. Species richness of ferns and birds peaked at higher elevations along the less rainy transect, possibly as a result of higher levels of solar radiation and ecosystem productivity. Patterns of species richness and endemism of the study groups are causally unrelated and cannot be used to predict those of other groups at the spatial scale of this study. Human impact was highest in areas of mostly low to intermediate species richness, but was often high in zones of high endemism.
Differential rates of invasion in three related alien oak gall wasps (Cynipidae: Hymenoptera)
Authors: Walker P. , Leather S. R. , Crawley M. J. 
Published: March 2003

Abstract. Three related species of oak gall wasps,Andricus corruptrix(Schlechtendal),A. kollari(Hartig) andA. lignicola(Hartig) have entered Britain since the introduction of Turkey oak,Quercus cerrisL. in 1735. Their lifecycles involve alternating generations between an agamic generation on the native oak species (Q. petraea,Q. robur andtheir hybridQ. x. rosacea), and a smaller, sexual generation on the alienQ. cerris. In examining the distributions of these insects andQ. cerris, we hypothesized that: (1) the invasion will spread more rapidly in places where both host trees are equally abundant than through regions where one of the tree species is substantially less common than the other; (2) interspecific competition between these bud‐galling species will lead to a negative correlation between their abundances at a particular site; (3) differential recruitment of natural enemies from the native hymenopteran fauna will slow the rate of spread in a species‐specific manner.A. kollariarrived nearly 200 years ago and is now found throughout the British Isles, wherever Turkey oak is grown.A. lignicolaandA. corruptrixhave been here for 30 years, after establishing in S.E. England.A. lignicolais in its final rapid stages of range expansion across England, southern Scotland and N.E. Scotland.A. corruptrixis just beginning to spread through Central and S.W. England. It has occupied proportionally fewer sites behind its invasion front than have the other two species, but is no less abundant at these sites. Nevertheless, distance leaps of up to 50 km were identified inA. lignicolain N.E. Scotland, and the possibility of long‐distance transport of infected trees through the horticulture and forestry trades remains. The co‐occurrence of mature individuals of both hostQuercusspecies does appear to have increased their rates of colonization inA. lignicolaandA. corruptrix. There is no evidence, however, to suggest that interspecific competition between the three alien gall formers is an important factor in determining their distributions and abundance within their invaded ranges. All three species have recruited parasitoids and inquilines rapidly from the native fauna; attack rates were highly variable, but showed no evidence of density dependence across sites.
Grazing and community structure as determinants of invasion success by Scotch broom in a New Zealand montane shrubland
Authors: Bellingham P. J. , Coomes D. A. 
Published: March 2003

Abstract. Scotch broom (Cytisus scoparius (L.) Link; Fabaceae) is a problematic invasive plant in many countries, and while attention has been paid to traits that make it a successful invader, there has been less focus on the properties of ecosystems that it invades. We conducted an experiment in a New Zealand montane shrubland with tussock grasses that has been invaded by Scotch broom to determine features that rendered it susceptible to invasion. We planted broom seedlings into the shrubland (control) and into three treatments: (1) resident shrubs removed, (2) tussocks removed and (3) shrubs and tussocks removed. We measured broom seedling mortality and growth over two growing seasons. The site was grazed by sheep in the first season, and scarcely grazed in the second, wetter season. Survivorship across all treatments after 19 months was 42%, and was lowest where shrubs were retained but tussocks removed. Broom seedlings grew taller and had greater leaf areas in treatments that retained shrubs. Neighbouring (within 49 cm) shrubs had no effects on survivorship or growth of broom seedlings. Neighbouring tussocks increased survivorship of broom seedlings but depressed their growth. Grazing by sheep was the most important determinant of survivorship and growth of broom seedlings, and effects were uniform regardless of experimental treatments. Initial high mortality of seedlings (48% in the first 3 months) was due to grazing, and height growth was often negative during periods of grazing. In the second growing season when the site was less grazed and there was greater rainfall, there was a rapid increase in height across all treatments. Continued grazing of the site by sheep is likely to be the chief means of retarding the invasion.
Large‐scale terrestrial gastropod community composition patterns in the Great Lakes region of North America
Authors: Nekola Jeffrey C. 
Published: March 2003

Abstract:Previous ordination studies of land snail community composition have been limited to four or fewer habitat types from sites separated by no more than 300 km. To investigate the nature of large‐scale patterns, North American land snail assemblages at 421 sites, representing 26 habitat types and covering a 1400 × 800 km area, were ordinated using global, nonmetric multi‐dimensional scaling (NMDS). These data were then subjected to model‐based cluster analysis and kmeans clustering to identify the main compositional groups and most important environmental covariables. Six primary compositional groups were identified. Three of these largely represent upland forest and rock outcrop sites, while the remaining largely represent either lowland forest, lowland grassland or upland grassland habitats. The geographical location and moisture level of sites also influences community composition. A strong compositional difference exists between sites having duff vs. turf soil surface layers. Only 8% of sites were improperly classified when soil surface architecture was used as the sole predictor variable. Fully 43% of taxa exhibited significant preferences towards one of these surface types, while only 15% of relatively common (10 + occurrence) taxa showed no preferences. Twelve groups of closely related taxa within the same genus had members that favoured different surface types, indicating that differential selection pressures have existed over evolutionary time scales. While turf faunas appeared unaffected by anthropogenic disturbance, duff faunas were strongly impacted, suggesting that their conservation will require protection of soil surface architecture.
Effect of endogenous catecholamine on myocardial stunning in a simulated ischemia model
Authors: Ishiguro Yoshiki , Morgan James P. 
Published: March 2003

During ischemia, large amounts of catecholamine are released to the myocardium from the sympathetic nerve endings in the heart. It has not been clearly shown whether the released catecholamine has detrimental or beneficial effects on postischemic myocardial contractile function. The aim of the present study was to investigate the effect of endogenous catecholamine released during ischemia on myocardial contractile function, using ferret papillary muscles in a stimulated ischemia model.Papillary muscles were excised and mounted in organ baths containing oxygenated physiological salt solution at 37 °C. In order to eliminate the effect of endogenous catecholamine, a subset of animals was reserpinized for 2 days prior to the experiments. Muscles were stabilized for 1 h, and stretched to the length at which maximal isometric tension developed. Ischemia was simulated by changing the solution to liquid fluorocarbon bubbled with 95% N2 and 5% CO2. After 20 min of ischemia, the bathing medium was replaced with oxygenated physiological salt solution and developed tension was measured for 60 min. Pharmacologic agents with specific effects on myocardial autonomic pathways were used to investigate the cellular mechanisms of the observed effects.Tension recovery of reserpinized muscles was significantly better than control muscles (65.5 ± 2.8% vs. 54.9 ± 5.0%, P < 0.01). Exogenously administered β‐adrenergic antagonists did not attenuate stunning in control muscles; whereas forskolin and carbachol exacerbated stunning.These results indicate that catecholamine released during ischemia exacerbates myocardial stunning and overrides the effect of clinically relevant concentrations of β‐adrenergic antagonists, which may limit their ability to protect myocardium from acute ischemic insult. The effect of endogenous catecholamine was simulated by forskolin, but not attenuated by carbachol, which suggests that changes in the contractile apparatus activated by excess cyclic AMP were relevant to the mechanical dysfunction that developed.
Relationships between the antihypertensive effects of bisoprolol and levels of plasma atrial natriuretic peptide in hypertensive patients
Authors: Baláti Beáta , Phung Henry , Pousset Françoise , Isnard Richard , Boisvieux Anne , Carayon Alain , Komajda Michel , Lechat Philippe 
Published: March 2003

AbstractPrevious studies have demonstrated that beta‐blockade increases the levels of plasma atrial natriuretic peptide (ANP), but relationships between this effect and the antihypertensive action of beta‐blockade remain unknown. In this study we investigated the amplitude and determinants of bisoprolol‐induced ANP increase and the relationships between this increase and the antihypertensive effect of bisoprolol. Nineteen patients with mild to moderate hypertension were included in the study. In the first phase of the study (cross‐over, placebo controlled, randomized phase), the effects of 10 mg bisoprolol on plasma ANP at rest and during exercise were compared to placebo. The antihypertensive action of bisoprolol was then evaluated after a 2‐week period of treatment (10 mg/day) using ambulatory blood pressure monitoring. Bisoprolol significantly increased plasma ANP level at rest (from 30.6 ± 20.5 to 42.8 ± 35.6; P < 0.05) and also during exercise (from 54.7 ± 44.3 to 119.1 ± 159.9; pg/mL ± SD; P < 0.05). Plasma ANP at rest was not significantly correlated with left ventricular mass. After the 15 days of treatment, the bisoprolol‐induced daytime diastolic blood pressure reduction was significantly correlated to the initial bisoprolol‐induced plasma ANP increase (r=0.49, P=0.035). These results suggest that the antihypertensive effect of beta‐blocking agents could be partly mediated by an increase of ANP release.
Effects of athletic training on heart rate variability triangular index
Authors: Kouidi E. , Haritonidis K. , Koutlianos N. , Deligiannis A. 
Published: March 2003

SummaryThe purpose of this study was to assess the heart rate variability triangular index (HRVI) in elite track and field athletes. Sixty healthy males (mean aged 22·1 ± 3·5 years) −15 long distance runners (group A), 15 speed runners (Group B), 15 throwers (Group C) and 15 non‐trained subjects (Group D) were submitted to spiroergometric test, m‐mode echocardiography and 24‐h ambulatory ECG monitoring. The HRVI, mean heart rate, mean interval between two consecutive R waves of the QRS complexes (R–R interval) and standard deviation of the R–R (SDRR) were assessed through time domain method on computed 24‐h Holter recordings. The HRVI and the SDRR were 62·2 ± 9·6 and 220 ± 40 ms correspondingly in group A, 52·7 ± 6·0 and 210 ± 40 ms in B, 44·5 ± 5·3 and 180 ± 40 ms in C, 39·3 ± 6·4 and 180 ± 30 ms in D. The HRVI and the mean R–R were found to differ statistically between groups A, B and C versus D (P<0·05). However, the higher value in HRVI was found in group A. Maximal oxygen consumption (VO2max) was 62·0 ± 4·4 ml kg−1 min−1 in group A, 52·7 ± 6·0 in group B, 44·6 ± 5·3 in C and 41·6 ± 6·0 in D. The higher value in VO2max was also found in group A. The left ventricular mass index (LVMI) and end‐diastolic volume index (EDVI) were 136 g m−2 and 83 ml m−2 correspondingly in group A, 136 and 79 in B, 124 and 56 in C and 88 and 55 in group D. The HRVI was found to have a significant relationship with VO2max and EDVI only in group A. On the other hand, no significant relationships were found between HRVI and LVMI in all groups. It is concluded, that the enhanced HRVI in athletes is affected by exercise training pattern. Moreover, HRVI depends on the level of VO2max in endurance‐trained, but is independent from the extent of myocardial hypertrophy in all types of training.
Effect of standing on short term heart rate variability across age
Authors: Srinivasan K. , Sucharita S. , Vaz Mario 
Published: March 2003

SummaryThis study examined the response of heart rate variability measures to standing in three age groups of male subjects: Children (6–11 years), young adults (20–30 years) and elderly (60–70 years). Supine and standing heart rate variability indices were measured in all the subjects using power spectral analysis. The effect of posture on heart rate variability was assessed using the change in heart rate variability measures over resting values during the first 2 min following active standing. There was an attenuated response in normalized low frequency (LF) and high frequency (HF) power to standing in the elderly as compared with young adults and children. Heart rate variability responses to standing were highest in the young adults, followed by the children and the elderly, although the differences between the young adults and children were not significant. More studies are needed to characterize HRV responses to posture in children.
Natural Capital and Sustainable Development
Authors: COSTANZA ROBERT , DALY HERMAN E. 
Published: March 2003

Abstract: A minimum necessary condition for sustainability is the maintenance of the total natural capital stock at or above the current level. While a lower stock of natural capital may be sustainable, society can allow no further decline in natural capital given the large uncertainty and the dire consequences of guessing wrong. This “constancy of total natural capital” rule can thus be seen as a prudent minimum condition for assuring sustainability, to be relaxed only when solid evidence can be offered that it is safe to do so.We discuss methodological issues concerning the degree of substitutability of manufactured for natural capital, quantifying ecosystem services and natural capital, and the role of the discount rate in valuing natural capital. We differentiate the concepts of growth (material increase in size) and development (improvement in organization without size change). Given these definitions, growth cannot the sustainable indefinitely on a finite planet. Development may be sustainable, but even this aspect of change may have some limits. One problem is that current measures of economic well‐being at the macro level (i.e., the Gross National Product) measure mainly growth, or at best conflate growth and development. This urgently requires revision.Finally, we suggest some principles of sustainable development and describe why maintaining natural capital stocks is a prudent and achievable policy for insuring sustainable development. There is disagreement between technological optimists (who see technical progress as eliminating all resource constraints to growth and development) and technological skeptics (who do not see as much scope for this approach and fear irreversible use of resources and damage to natural capital). By maintaining natural capital stocks (preferably by using a natural capital depletion tax), we can satisfy both the skeptics (since resources will be conserved for future generations) and the optimists (since this will raise the price of natural capital depletion and more rapidly induce the technical change they predict).
Localization of a Contact Zone between Two Highly Divergent Mitochondrial DNA Lineages of the Brown Bear Ursus arctos in Scandinavia
Authors: TABERLET PIERRE , SWENSON JON E. , SANDEGREN FINN , BJÄRVALL ANDERS 
Published: March 2003

Abstract: In Europe the brown bear (Ursus arctos) is represented by two different mitochondrial DNA (mtDNA) lineages, which probably diverged about 0.85 million years ago. Scandinavia has been colonized by representatives of both lineages, from the north (eastern lineage) and from the south (western lineage), and now bears occur primarily in four main regions called female concentration areas. For management purposes the localization of the contact zone between these two genotypes is important. Using hairs as a source of DNA, 127 individual brown bears from throughout the Scandinavian populations were assayed for lineage assignment. A part of the mtDNA control region was amplified via the polymearase chain reaction, and the product was either sequenced (14 individuals) or digested with two diagnostic restriction endonucleases (113 individuals). Fifty‐six and 71 bears were assigned to the western and eastern lineages, respectively. The geographic distribution of the two genotypes allowed precise localization of the contact zone. Only two males from each lineage had crossed the border between the two lineages. We used dispersal data from bears radiomarked as yearlings to determine whether potential mtDNA introgressions agreed with the dispersal behavior of bears. The males in the “wrong” areas were all within the 95th‐percentile dispersal distance from the “correct” area. Females were more philopatric than males, and none were found in the wrong areas. The two female concentration areas flanking the contact zone were 134 km apart. Thus, radiotelemetry results on dispersal distances could explain the occurrence of the males in the wrong genetic area. In the absence of information concerning possible male‐mediated gene flow, a conservative management approach would be to consider the southern and the three northern female concentration areas as two distinct conservation units.Localización de una zona de contacto entre dos linajes de ADN mitocondrial muy divergentes del oso pardo Ursus arctos en Escandinavia