bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms of fluid flow and fluid–rock interaction in fossil metamorphic hydrothermal systems inferred from vein–wallrock patterns, geometry and microstructure
Authors: Oliver Nicholas H. S. , Bons Paul D.
Published: March 2003

Comparison of mass transfer patterns, geometry and microstructures developed within and around veins allows the interpretation of processes of fluid flow during deformation, metamorphism and mineralization. A classification of vein types based on the degree of interaction with wallrock (using petrological, geochemical or isotopic indicators) can be used to identify a range of processes, from closed system behaviour in which the vein mass is derived from local wallrock, through to open system behaviour in which the vein mass is derived externally. Microstructural characteristics, such as wallrock selvages, multiple growth events recorded by vein seams and vein crystal morphology, also help to constrain mass transfer patterns during vein formation. We present a range of processes for vein formation, including: (i) the formation of closed system fibrous veins by dissolution–precipitation creep, including varieties in which tensile failure is not required; (ii) pressure‐ or kinetically dependent closed system segregation veins in which transfer of soluble components from wallrock to vein leaves behind a residual selvage; (iii) similar vein–selvage patterning, but with mass imbalances between vein and wallrock requiring fluid advection through both interconnected fracture networks and in the surrounding permeable rock; and (iv) the proposed formation of veins by fluid ascent in mobile hydrofractures, in which isotopic or chemical disequilibrium within and around the vein suggests that the crack and fluid within it moved essentially as one. The postulate of rapid fluid and mass transfer via such mobile hydrofractures has implications for the release of volatiles from metamorphic terrains. Also, consideration of a broad range of possible vein‐forming mechanisms is highly desirable when dealing with mineral deposits found in deformed, metamorphosed rocks, because closed system veining may produce patterns that, if erroneously recognized as being open systems, could lead to false interpretations of the role of tectonic fracturing in ore genesis.
The significance of pockmarks to understanding fluid flow processes and geohazards
Authors: Hovland M. , Gardner J. V. , Judd A. G.
Published: March 2003

Underwater gas and liquid escape from the seafloor has long been treated as a mere curiosity. It was only after the advent of the side‐scan sonar and the subsequent discovery of pockmarks that the scale of fluid escape and the moon‐like terrain on parts of the ocean floor became generally known. Today, pockmarks ranging in size from the ‘unit pockmark’ (1–10 m wide, < 0.6 m deep) to the normal pockmark (10–700 m wide, up to 45 m deep) are known to occur in most seas, oceans, lakes and in many diverse geological settings.

In addition to indicating areas of the seabed that are ‘hydraulically active’, pockmarks are known to occur on continental slopes with gas hydrates and in association with slides and slumps. However, possibly their potentially greatest significance is as an indicator of deep fluid pressure build‐up prior to earthquakes. Whereas only a few locations containing active (bubbling) pockmarks are known, those that become active a few days prior to major earthquakes may be important precursors that have been overlooked.

Pockmark fields and individual pockmarks need to be instrumented with temperature and pressure sensors, and monitoring should continue over years. The scale of such research calls for a multinational project in several pockmark fields in various geological settings.
Fluid flow and stability of the US continental slope offshore New Jersey from the Pleistocene to the present
Authors: Dugan B. , Flemings P. B.
Published: March 2003

We predict that portions of the New Jersey continental slope were unstable approximately 0.5 million years ago. This instability was caused by rapid sediment loading during a Pleistocene sea‐level lowstand and by flow focusing in underlying, permeable Miocene strata. The simulated instability is consistent with soft‐sediment deformation and small slumps in Pleistocene strata of the Hudson Apron. Stability of the New Jersey margin has increased since 0.3 Ma because sedimentation rate has decreased. Today, the modelled factor of safety (FS) for the upper slope is approximately 1.5 whereas in the lower slope it exceeds 3. We predict that sedimentation rate is a dominant factor on slope stability. When rapid and asymmetric loading of a highly permeable sedimentary layer occurs, the location of instability can shift seaward to regions where sedimentation rates are low. Stability calculations use pressures and effective stresses predicted by a coupled sedimentation‐fluid flow model. This hydrodynamic analysis demonstrates how the interplay of sedimentation and fluid migration affects the distribution, timing, and size of sedimentary failures.
Palaeomagnetic dating of fluid‐flow events in dolomitized rocks along the Highland Boundary Fault, central Scotland
Authors: Elmore R. D. , Parnell J. , Engel M. H. , Baron M. , Woods S. , Abraham M. , Davidson M.
Published: March 2003

Palaeomagnetic and geochemical studies of Cambrian–Ordovician serpentinite in the Highland Border Complex (HBC), a tectonic terrane along the Highland Boundary Fault (HBF) in Scotland, indicate that the HBF was a conduit for fluids in the Carboniferous–Permian. The fluids caused dolomitization, silicification, and haematite authigenesis. Both red dolomitized serpentinite and relatively unaltered serpentinite were sampled at multiple localities. The unaltered serpentinite contains a poorly defined magnetization with westerly declinations that resides in magnetite and has a pole which plots well off the apparent polar wander path. Most specimens of the red dolomitized serpentinite contain a magnetization with southerly declinations and negative inclinations that resides in haematite. A regional fold test suggests that this magnetization post‐dates tilting and the pole positions for the different locations fall on the Carboniferous to Permian part of the apparent polar wander path. In some specimens of red dolomitized serpentinite, alternating field (AF) demagnetization prior to thermal treatment removes a component with a similar direction. Dolomitized basement rocks along the fault contain a similar although apparently slightly older magnetization. Fluid inclusion and geochemical studies indicate that the fluids were hydrothermal in origin (110–240°C) and had a range of sources. The Carboniferous–Permian magnetization in haematite is interpreted as a chemical remanent magnetization that formed when warm fluids moved along the fault zone and caused haematite authigenesis. The component removed by AF treatment is interpreted as a thermal resetting of primary magnetite by the fluids. The variability of the palaeomagnetic, fluid inclusion, and stable isotope results suggests that there were probably multiple flow events that caused the alteration. The origin of the fluids could be related to the intrusion of late Carboniferous dikes in central Scotland and/or to reactivation of the HBF in the Carboniferous–Permian.
Perceived temperature effects on microwave heated meals and meal components
Authors: Ryynänen Suvi , Tuorila Hely , Hyvönen Lea
Published: March 2003

Two experiments were carried out to evaluate the effect of serving temperature on the pleasantness of microwave heated ready meals and meal components. Serving temperature clearly affected sensory attributes and the pleasantness of the meal components. However, while instrumental measurements had indicated large differences in temperatures between two microwave heated ready meals with different arrangement of meal components, the consumer panel perceived only small differences in some sensory attributes. Regardless of temperature differences, the overall pleasantness of the two microwave heated meals was judged to be similar. We concluded that serving temperature is critical for the pleasantness of food but, to the extent that it varied in microwave heating, it did not have a major impact on the overall pleasantness of the meal. Possibly in long‐term use, very uneven temperature distribution may become a nuisance and therefore, the arrangement of meal components with a more uniform temperature distribution is recommended.
Geographic gradients in body size: a clarification of Bergmann's rule
Authors: Blackburn Tim M. , Gaston Kevin J. , Loder Natasha
Published: March 2003

1997 marked the sesquicentenary of the publication by Carl Bergmann of the observation that, in general, large‐bodied animal species tend to live further north than their small‐bodied relatives. This has been dubbed Bergmann's rule in his honour. However, more than 150 years on, we appear to be little closer to a general understanding of the rule, or even to any consensus as to whether it exists. This is due in large part to confusion about the taxonomic level at which the rule is considered to operate, and to the conflation of pattern and mechanism. In this paper, we attempt to resolve this confusion by highlighting its sources, and by providing a definition of Bergmann's rule that is practical and useful, yet that retains the essential features of its original formulation. We conclude by briefly reviewing the mechanisms proposed to explain Bergmann's rule as we define it.
Ants that associate with Lycaeninae butterfly larvae: diversity, ecology and biogeography
Authors: Fiedler Konrad
Published: March 2003

Field data on associations of butterfly larvae with ants were collated for 435 species of the subfamily Lycaeninae to analyse patterns in the identity, diversity and ecology of attendant ants. Worldwide, members of at least fifty‐three ant genera from six subfamilies associate with Lycaeninae larvae. All these ant genera also forage for other liquid carbohydrate food sources. Species of Crematogaster and Camponotus constitute by far the most important ant associates of Lycaeninae larvae. Diversity of butterfly–ant associations, as measured by Hurlbert rarefaction, is highest in the Oriental, Australian and Nearctic faunal regions, and lower in Africa and the Palaearctic. The Neotropical region could not be assessed separately due to paucity of data. Multiple regression analyses revealed that the number of Lycaeninae species associated with a particular ant genus in a facultatively mutualistic manner is largely determined by the ecological prevalence and geographical distribution, but does not correlate with species richness, of an ant genus. This opportunism is suggested to be the key variable supporting the geographically and taxonomically widespread occurrence of ant–caterpillar mutualism in the Lycaeninae. Obligate interactions are much more specific and almost exclusively involve ecologically dominant ants with long‐lived colonies. Neither species richness nor geographical distribution of an ant genus are significant predictors. In such associations, the role of ants shifts from visitors to hosts, and patterns of host use and specificity resemble those known from inquiline ant guests.
Patterns of isozyme variation as indicators of biogeographic history in Pilgerodendron uviferum (D. Don) Florín
Authors: Premoli A. C. , Souto C. P. , Rovere A. E. , Allnut T. R. , Newton A. C.
Published: March 2003

The effects of Pleistocene glaciations on the genetic characteristics of the most austral conifer in the world, Pilgerodendron uviferum, were analysed with specific reference to the hypothesis that the species persisted locally in ice‐free areas in temperate South America. It was expected that genetic variation would decrease with latitude, given that ice fields were larger in southern Patagonia and thus refugia were probably located towards the northern distributional limit of the species as suggested by the fossil record. In addition, an increase in among‐population genetic divergence was expected with increasing distance to putative glacial refugia. We examined the relationship between location and within‐population variability indices of 20 Pilgerodendron populations derived from isozyme analyses. We analysed possible refugia hypotheses by the distribution of allele frequencies using multivariate discriminant analysis. The degree of genetic differentiation with geographical distance between all population pairs was investigated by Mantel tests. Results indicated that Pilgerodendron populations are highly monomorphic, probably reflecting past population bottlenecks and reduced gene flow. Southernmost populations tend to be the least genetically variable and were therefore probably more affected by glacial activity than northern ones. Populations located outside ice limits seem to have been isolated during the glacial period. The presence of centres of genetic diversity, together with the lack of a significant correlation between genetic and geographical distances and the absence of geographical patterns of allelic frequencies at most analysed alleles, may indicate that Pilgerodendron did not advance southward after the last glaciation from a unique northern refugium, but spread from several surviving populations in ice‐free areas in Patagonia instead.
Taxonomic resolution of the genus Bythotrephes Leydig using molecular markers and re‐evaluation of its global distribution
Authors: Therriault Thomas W. , Grigorovich Igor A. , Cristescu Melania E. , Ketelaars Henk A. M. , Viljanen Markku , Heath Daniel D. , Macisaac Hugh J.
Published: March 2003

Bythotrephes Leydig is a predatory, onychopod cladoceran native to Eurasia that typically inhabits oligo‐ and mesotrophic water bodies of the Palaearctic region. It recently invaded 70 North American lakes, prompting a re‐evaluation of the taxonomic status, global distribution, and determinants of local occurrence and abundance. European studies have reported two distinct species, B. longimanus, which lacks a kink on the caudal process, and B. cederstroemi, which possesses one. We employed sequencing of the mitochondrial gene cytochrome c oxidase subunit I (COI) in addition to Directed Amplification of Minisatellite‐region DNA (DAMD) using polymerase chain reactions (PCRs) to assay the genetic nature of these ‘species’. These analyses revealed that the two taxa are consistent with a single, common species, Bythotrephes longimanus Leydig 1860, thus resolving the nomenclatural issue. Furthermore, a common haplotype was identified between Lake Ontario and Lake Puruvesi, Finland, suggesting a potential invasion corridor via the nearby Baltic Sea. Statistical analysis revealed that the two forms also occur in similar habitats in Eurasia and North America. Habitat characteristics of water bodies in Northern Europe, where both forms are found and occasionally co‐occur, do not differ statistically. Similarly, no significant differences were detected between characteristics of Eurasian habitats that support longimanus‘forms’ and those of inland lakes in North America that support cederstroemi‘forms’. Human activities have had a strong effect on the distribution of Bythotrephes in both Europe and North America. Global and local distributions have been affected by ballast water transfer and by boating and fishing activities, respectively. Cultural eutrophication, oligotrophication and acidification alter the suitability of habitats for fish predators, and may indirectly influence Bythotrephes’ local occurrence and abundance.
Substitution patterns in congeneric arachnid species in the northern Alps
Authors: Muster Christoph
Published: March 2003

Complementary abundance gradients of substituting congeneric arachnids along the northern margin of the Alps are described, and the possible historical and contemporary factors that have produced these distributions are explored. The intensities of activity of epigeous arachnids were determined in pitfall traps along seven altitudinal transects approximately 35 km apart in the Bavarian Alps (Germany) and in the county of Salzburg (Austria). No supraregional gradient of physical factors exists within the region investigated. Six pairs of congeners show vicariances or alternating abundance gradients. For each species pair, the abundance gradient is represented in diagrams and compared with a graphic model of substitution types. Three patterns are evident: strict vicariances, abrupt replacement in a narrow belt, and gradual substitution over a wide zone of sympatric occurrence. The different extent of range overlap suggests distinctive classes and intensities of interspecific interactions. With regard to biogeographic histories, one prevailing pattern emerged: endemic species of the eastern Alps are replaced by Eurosiberian counterparts towards the west. It appears that geographical abundance variation reflects colonization history.
The role of Late Holocene climate variability in the expansion of yellow birch in the western Great Lakes region
Authors: Jackson Stephen T. , Booth Robert K.
Published: March 2003

Abstract. Pollen records from the western Great Lakes region of North America show substantial increases in birch pollen percentages during the late Holocene. The vegetational and population dynamics underlying the birch increase have received little attention, in part because of the inability to discriminate among species of birch based on pollen morphology. We used analyses of pollen and plant macrofossils from four lakes in the Upper Peninsula of Michigan to document that the birch pollen increase represents a regional expansion of yellow birch (Betula alleghaniensis) populations, which was initiated c. 4500 years ago. Whether yellow birch invaded the region at this time or simply expanded from small, previously established populations is not clear, although it probably did not grow near our study sites before the expansion. The initial expansion occurred during an independently documented period of high moisture and high water levels in Lake Michigan. A subsequent expansion in yellow birch abundance and distribution occurred c. 3000 years ago, coinciding with a second period of increased moisture and high lake‐levels. The yellow birch expansion may have been modulated by millennial‐scale climate variability, with most rapid expansion occurring during relatively wet periods.
Responses of ‘resistant’ vertebrates to habitat loss and fragmentation: the importance of niche breadth and range boundaries
Authors: Swihart Robert K. , Gehring Thomas M. , Kolozsvary Mary Beth , Nupp Thomas E.
Published: March 2003

Abstract.An ability to predict species’ sensitivities to habitat loss and fragmentation has important conservation implications, and numerous hypotheses have been proposed to explain interspecific differences observed in human‐dominated landscapes. We used occupancy data collected on 32 species of vertebrates (16 mammals and 16 amphibians) in an agricultural landscape of Indiana, USA, to compare hypotheses that focus on different causal mechanisms underlying interspecific variation in responses to habitat alteration: (1) body size; (2) morphology and development; (3) behaviour; (4) niche breadth; (5) proximity to range boundary; and multiple‐process models combining main effects and interactions of hypotheses (1)–(2) and (4)–(5). The majority of habitat alteration occurred over a century ago and coincided with extinction of several species; thus, our study dealt only with variation in responses of extant species that often are considered ‘resistant’ to human modifications of native habitat. Corrected Akaike scores and Akaike weights provided strongest support for models incorporating niche breadth and proximity to range boundary. Measures of dietary and habitat breadth obtained from the literature were negatively correlated with sensitivity to habitat alteration. Additionally, greater sensitivity was observed for species occurring at the periphery of their geographical ranges, especially at northern or western margins. Body size, morphological, developmental and behavioural traits were inferior predictors of tolerance to fragmentation for the species and landscape we examined. Our findings reinforce the importance of niche breadth as a predictor of species’ responses to habitat alteration. They also highlight the importance of viewing the effects of habitat loss and fragmentation in a landscape within a biogeographical context that considers a species’ level of adaptation to local environmental conditions.
Morphological variations of lobate phytoliths from grasses in China and the south‐eastern United States
Authors: Lu Houyuan , Liu Kam‐Biu
Published: March 2003

Abstract. Phytolith analysis of grasses is a useful tool in palaeoenvironmental and archaeobotanical research. Lobate phytolith is one of the most important morphotypes of grass phytoliths. This study describes morphological variations of diagnostic lobate phytoliths and produces a tentative classification scheme based on 250 modern grass species from China and the south‐eastern U.S.A. Eighty‐five grass species were found to contain lobate phytoliths. They are derived mainly from Panicoideae, but also include the Chloridoideae, Oryzoideae and Arundinoideae subfamilies. Twenty‐five lobate morphological types were observed from different subfamilies, genera or tribes of grasses, based on two important parameters: (1) the length of the lobate shank and (2) the shape of the outer margin of the two lobes. The identification of grass tribe or even genus is possible based on the differences in lobate shape parameters or the composition of assemblages. However, not all of the lobate assemblages have a definite relationship with the genera that produce them, because grasses can only produce a limited range of lobate shapes that often overlap from one genus to another. Several C3 grasses and Chloridoideae subfamily grasses also produce characteristic lobate phytoliths. The variations of lobate morphologies can be related to environmental factors, especially moisture. Typical hygrophytic grasses tend to yield lobate phytoliths with very short shank, whereas typical xerophytic grasses tend to produce lobate phytoliths with a very long shank. The potential link between phytolith morphology, grass taxonomy and environmental conditions opens the possibility that phytolith morphology may be used as a proxy in palaeoclimatic reconstruction.
Beta‐blocker treatment in heart failure
Authors: Bouzamondo A , Hulot J S , Sanchez P , Cucherat M , Lechat P
Published: March 2003

Heart failure treatment has markedly changed during the last few decades, with demonstration of benefit of afterload reduction by vasodilator therapy and introduction of the concept of the deleterious consequences of the neuro‐hormonal compensatory stimulation. Blockade of beta‐adrenergic receptors, initially contra‐indicated in heart failure, provide a marked reduction of mortality and morbidity in combination with diuretics and angiotensin‐converting enzyme inhibitors, as demonstrated in many clinical trials.

We performed a review of all clinical trials that compare beta‐blockers vs. placebo in chronic heart failure. Beta‐blockers with different pharmacological profiles have been tested, mainly metoprolol, bisoprolol, bucindolol and carvedilol. With progressive dose increment, tolerance of such treatment was generally good, left ventricular function improved, hospitalisations for heart failure were less frequent and mortality was reduced. The meta‐analysis of the 16 randomised trials, with at least one death in each treatment group, provides a 24% relative risk reduction for such hospitalisations (95% CI=19%–29%) and 22% reduction for mortality (95% CI=16%–28%). Heterogeneity of beta‐blocker effect for mortality was found and related to the non‐significant benefit obtained in the BEST trial with bucindolol. When such a trial is excluded, the effect model analysis shows that relative risk reduction (beta‐blocker induced benefit) is constant whatever the severity of the disease. The mechanism of beta‐blocker induced benefit remains unclear, but is at least partly related to left ventricular function improvement and prevention of severe ventricular arrhythmias.

In conclusion, beta‐blocker treatment has become an established therapy for heart failure, in combination with diuretics and ACE inhibitors. Complementary informations will be needed to clarify the mechanism of benefit and to define the best therapeutic strategy according to the individual characteristics of patients with heart failure.
Adverse drug reactions: keeping up to date
Authors: Aronson Jeffrey K. , Derry Sheena , Loke Yoon K.
Published: March 2003

The amount of published literature on adverse drug reactions is overwhelming; for example, the serial publication Side Effects of Drugs Annual lists and critically discusses over 3000 references each year. As a group, pharmacotherapeutics journals publish more papers on adverse drug reactions than journals that cover other fields, but even so they publish a minority of the total number of papers, and no single journal or group of journals can be highlighted as being a frequent source of primary information. Non‐specialists must therefore rely on secondary literature (reviews) and tertiary literature (critical summaries) for information. Most of the primary published literature is in the form of anecdotal reports (30%) and formal studies or randomized controlled trials (35%). The anecdotal reports vary in quality; a new serial publication devoted to this type of article would bring some of the literature together and would improve the quality of reporting. Although many of the randomized controlled trials are of good quality and large enough to reveal benefit, most are too small to provide robust information about adverse drug reactions. Systematic reviews are too few in number (only 1.25% of publications on adverse drug reactions cited in Side Effects of Drugs Annual); more are needed.
Psychomotor and cognitive effects of piribedil, a dopamine agonist, in young healthy volunteers
Authors: Schück Stéphane , Bentué‐Ferrer Danièle , Kleinermans Diane , Reymann Jean‐Michel , Polard Elisabeth , Gandon Jean‐Marc , Allain Hervé
Published: March 2003

Piribedil is a dopamine agonist acting on D2 and D3 central nervous system dopamine receptors. This drug has been administered to 12 young healthy male volunteers (age 22 ± 2 years) according to a single center randomized, double‐blind, two ways cross‐over, placebo controlled trial, including a washout period of one week. Placebo and piribedil were administered by a single intravenous infusion over 2 h (3 mg). Psychomotor performance and cognitive functions were assessed through a standardized and computerized psychometric tests battery and a continuous electroencephalogram (EEG) mapping. Piribedil improved simple reaction time (P=0.02), immediate (P=0.045 and 0.004), and delayed free recall (P=0.05), dual coding test (P=0.02) and increased theta and fast beta waves on the EEG (P < 0.05 and 0.001, respectively). No deleterious effect was observed on the tests exploring attention and concentration via the other procedures. It is concluded that a single intravenous perfusion of piribedil 3 mg improves alertness and the information processing speed within the central nervous system, in healthy volunteers.
Gender differences in adverse drug reactions: analysis of spontaneous reports to a Regional Pharmacovigilance Centre in France
Authors: Montastruc Jean‐Louis , Lapeyre‐Mestre Maryse , Bagheri Haleh , Fooladi Atoussa
Published: March 2003

The aim of this study was to investigate putative gender‐related differences in adverse drug reactions (ADRs). Data were ADRs recorded in the database of the French Midi‐Pyrénées Pharmacovigilance Centre in 1998. A total of 927 ADRs were spontaneously reported to the Centre in 1998, of which 53.1% were in females (difference vs. males not statistically significant). There was no statistically significant difference in the incidence of reported ADRs in males (3.6/10 000 inhabitants) vs. females (3.9/10 000 inhabitants) for the total population of the Midi‐Pyrénées area. The number of reported ADRs was similar across different age groups (10‐year age ranges). However, ‘serious’ ADRs were more frequently reported in males in the 0–9 and 60–69 age groups (and in females between 20 and 29 years old). There were significantly more neuropsychiatric (69 vs. 43, P=0.05) and fewer cardiovascular (8 vs. 2, P=0.05) ADRs reported in females than in males. ADRs were more frequently reported in females for some classes of drugs (such as genito‐urinary, sex hormone, antineoplastic, antiparasitic and respiratory drugs). These results confirm that female gender is a risk factor for the development of ADRs.
Effects of nicardipine and clonidine on cognitive functions and electroencephalography in hypertensive patients
Authors: Denolle T. , Sassano P. , Allain H. , Bentué‐Ferrer D. , Breton S. , Cimarosti I. , Ouatara B. , Merienne M. , Gandon J.‐M.
Published: March 2003

The aim of this study was to investigate the cognitive and electroencephalography (EEG) short‐term effects of a calcium antagonist, nicardipine, compared to placebo and clonidine (which, having known sedative effects, acted as a negative control) for 15 days in elderly hypertensive patients with memory complaints. Nicardipine and clonidine were compared with placebo in a double‐blind, randomized, three‐way cross‐over controlled study after a 2‐week placebo run‐in period. This was a phase II clinical study carried out on out‐patients in a single research centre. Fifteen elderly (63 ± 10 years) hypertensive patients, without dementia but with memory complaints, were included. Psychomotor performance and cognition were assessed using both an extensive battery of validated psychometric tests (which evaluated attention and vigilance, body sway and memory) and an EEG profile. Cardiovascular parameters measured were blood pressure and heart rate. No detrimental effects of nicardipine were found on attention, vigilance, body sway or memory. Nicardipine produced a significant increase in alpha EEG energies, which may indicate possible alerting effects. In contrast, clonidine induced well‐known deleterious sedative effects in psychometric tests and in EEG analysis (decrease in alpha and increase in delta and theta waves). The two drugs produced equivalent decreases in blood pressure at steady state. In conclusion, clonidine induced well‐known sedative effects, while nicardipine did not impair central nervous system activity and may have had some short‐term alerting effects in elderly hypertensive patients with memory complaints. This study supports the hypothesis of a dissociation between blood pressure and direct drug effects on the central nervous system.
Piribedil‐induced sleep attacks in Parkinson's disease
Authors: Tan E. K.
Published: March 2003

‘Sleep attacks’, episodes of sudden onset of sleep without any prodromal symptoms, were initially described in patients with Parkinson's disease (PD) taking the newer dopamine agonists pramipexole and ropinirole. Piribedil, a nonergot agonist with both D2 and D3 agonist action, is an effective antiparkinsonian medication. However, there are very few reports of Piribedil‐induced sleep attacks in PD. Among 50 PD patients seen at our Movement Disorder Clinic who had recently taken Piribedil, we identified three (6%) who satisfied the clinical description of sleep attacks. Here we provide details of the clinical characteristics of Piribedil‐induced sleep attacks in these PD patients.
Lower reference limit for maximal oxygen uptake in men and women
Authors: Davis James A. , Storer Thomas W. , Caiozzo Vincent J. , Pham Patrick H.
Published: March 2003

Maximal oxygen uptake (O2max) is an important measure of exercise tolerance and low values may have clinical significance. Our purpose was to develop the necessary statistics – prediction equations and standard errors of estimate (SEE) – so that the lower reference limit for O2max can be predicted for men and women. The subjects were healthy, non‐smoking, sedentary men (n=115) and women (n=115) aged 20–70 years who performed 15 W min−1 cycle ergometer exercise tests. Three equations were developed for each gender using multiple linear regression with the non‐exercise predictor variables of age and height, age and mass, and age and fat‐free mass (FFM). The assumptions of regression analysis were examined and the predicted residual sum of squares (PRESS) method was used to cross‐validate each equation. Healthy and diseased individual subject data from the literature were used to externally validate our lower reference limit statistics. The equations developed meet the assumptions of regression analysis and have an accuracy similar to the non‐exercise prediction equations in the literature with R2 values of ∼0·581. The PRESS method revealed that the equations are generalizable, i.e. may be used in future studies without a significant loss of accuracy. The lower reference limit predictions for the healthy and diseased individual subject data from the literature produced few miscategorizations unless the subjects were obese and mass was used as a predictor variable. In conclusion, the equations and SEE generated in this study can be used to predict an accurate and valid O2max lower reference limit for a given subject.
Simultaneous non‐invasive assessment of arterial stiffness and haemodynamics – a validation study
Authors: Kööbi Tiit , Kähönen Mika , Iivainen Tiina , Turjanmaa Väinö
Published: March 2003

The purpose of the study was to estimate the reliability of whole‐body impedance cardiography (ICGWB)‐derived pulse wave velocity (PWV) and stroke volume index to pulse pressure (SI/PP) measurements. The repeatability and reproducibility of ICGWB parameters were also determined. Agreement between the impedance and Doppler ultrasound‐based PWV measurements was estimated in 25 healthy subjects in two consecutive measurements. Impedance‐derived SI/PP (SIICG/PP) estimates were compared with simultaneously measured SI/PP based on thermodilution (SITD/PP) and direct Fick (SIFICK/PP) methods in 30 surgical patients. PWV measured between the aortic arch and popliteal artery using the impedance technique with selective electrode configuration (PWVIS) agreed well with the Doppler ultrasound method (PWVDOPP), the bias (PWVDOPP – PWVIS) and precision (± SD of differences) being 0·00 and 0·79 m s−1, respectively. PWV derived from the whole‐body and popliteal impedance plethysmograms (PWVICG) overestimated slightly PWVDOPP values. The repeatability value for PWVIS was excellent, being 0·54 m s−1. The reproducibility values for PWVDOPP and PWVIS were very similar (2·17 and 2·42 m s−1, respectively). Changes in PWVIS correlated strongly with changes in PWVDOPP (r=0·74; P<0·0001), indicating that both methods reflected the true physiological variation in PWV. The agreement between SIICG/PP and SITD/PP or SIFICK was almost identical to the agreement between the SITD/PP and SIFICK/PP. In conclusion,whole‐body impedance cardiography provides handy and reliable means of evaluating arterial stiffness on the basis of PWV and SI/PP simultaneously with conventional haemodynamic parameters. The method is highly repeatable and reproducible.
Dispersal Can Limit Local Plant Distribution
Authors: Primack Richard B. , Miao S.L.
Published: March 2003

The ability of species to establish new populations at unoccupied sites is a critical feature in the maintenance of biological diversity, and it has taken on new importance as a result of global climate change and expected changes in species distribution. To examine the dispersal potential of plant species, seeds of four annual plant species were experimentally dispersed 40 to 600 m from existing populations in Massachusetts (U.S.A.) to 34 nearby unoccupied but apparently suitable sites. At three of these sites new populations were established that persisted for four generations and expanded slowly in area. At seven sites, a small initial population eventually died out. At the 24 other sites, new populations did not become established, indicating that the sites were in some way unsuitable, that not enough seeds arrived, or that conditions suitable for seed germination do not occur every year. These results suggest that some species may be unable to disperse naturally out of their existing ranges in response to global climate change, particularly if habitat fragmentation creates barriers to dispersal. These species may have to be assisted to reach suitable sites nearby to prevent their extinction in the wild.
Geometrical Factors and Metapopulation Dynamics of the Bush Cricket, Metrioptera bicolor Philippi (Orthoptera: Tettigoniidae)
Authors: Kindvall Oskar , Ahlén Ingemar
Published: March 2003

This paper presents a metapopulation study of the bush cricket, Metrioptera bicolor, living in a recently fragmented landscape. The species inhabits grass and heathland patches of varying area and isolation. Analyses are made of how these geometrical factors affect local population size and density, distribution pattern, and the probability of local extinction and colonization. The proportion of available patches occupied varied between 72 and 79% during 1985–1990. Unoccupied patches were smaller and more isolated than those that were occupied. Patches where populations became extinct during this period were smaller than those with persisting populations. Since local population size was well correlated with patch area, it was clear that stochastic extinctions only occurred in small populations. Critical patch size for population extinction was approximately half a hectare. Colonized patches were less isolated than those that had not been colonized. Critical inter‐patch distance for colonization was about 100 meters. The turnover was restricted to an identifiable share of the available patches. Only 33% of the patches were so small that extinction due to stochastic causes could be considered highly probable. This metapopulation will therefore most likely persist over a considerable period in its present spatial structure. There are apparent threats of further fragmentation, however, and nothing is known about the likelihood of large‐scale extinctions resulting from extremely unfavorable weather conditions. Nevertheless, our results show that it is appropriate to include geometrical factors in metapopulation models.
Rarity and Vulnerability: The Birds of the Cordillera Central of Colombia
Authors: KATTAN GUSTAVO H.
Published: March 2003

Abstract: The rarity of an organism is widely accepted as a good predictor of vulnerability, but rarity has been interpreted in a variety of ways. Rabinowitz et al. (1986) defined three dimensions of rarity for an analysis of the flora of the British Isles geographic distribution, habitat specificity, and local population size. They found the three factors to be independent, that is, each factor provides information not provided by the other two. In this paper, the method of Rabinowitz et al. is used to analyze the vulnerability of the cloud forest avifauna of the Cordillera Central of Colombia The method is extended by assigning a vulnerability index to each form of rarity and analyzing its taxonomic and ecological correlates.

I found that the three factors are not independent. Species with wide geographic distribution tend to have broad habitat specificity and high population densities. One‐third of the species have low population density, and most of these have restricted habitat specificity and narrow geographic ranges. Forty‐five percent of the birds in this sample are highly vulnerable because they have narrow distributions and require forest habitats.

The taxonomic and ecological analyses reveal that some groups of species are particularly vulnerable. Among insectivorous birds, woodcreepers, spinetails, and antbirds seem to be very vulnerable becuse they depend on forest habitats. Raptors show no clear pattern, but for frugivores a clear pattern emerges. Some families (e.g., parrots, cotingas), seem to be consistently vulnerable, independent of body size. Tanagers show a significant correlation between body size and vulnerability. An analysis of local vulnerability (determined by habitat specificity and population size, regardless of distribution) reveals that frugivorous birds of restricted habitat specificity are significantly larger. Similar findings have been reported by other studies.

The three‐dimensional classification of rarity used in this study provides a rapid, albeit preliminary, approach to identifying vulnerable species. To develop management practices adapted to each particular case, careful analysis of life history traits and detailed population and community studies are required.
An American Invasion of Great Britain: The Case of the Native and Alien Squirrel (Sciurus) Species
Authors: USHER MICHAEL B. , CRAWFORD TERENCE J. , BANWELL JEAN L.
Published: March 2003

Abstract: The invasion of Great Britain by the gray squirrel from America has posed many interesting problems in ecology and conservation (interactions with the native red squirrel) and in forest management (the gray squirrel severely damages young stands of deciduous trees). Since 1973, mapped data on the annual distribution of the two species in state‐managed forests have been published by the Forestry Commission.

Using the established methodology of annual ornithological index numbers, series of index numbers have been calculated to show the distributional dynamics of the two species. In Great Britain as a whole there has been rather limited change over the 15‐year period from 1973. However, this masks (1) the dramatic distributional decline in the red squirrel in Wales balanced by a modest expansion in Scotland, and (2) the substantial distributional increase in the gray squirrel in the small number of grid squares in Scotland in comparison with the relatively steady distribution in the large number of grid squares in England.

A new index, measuring the annual replacement of one species by the other species, indicates little overall change in England and Scotland, but a net advance of the gray squirrel in Wales. A series of Markovian matrices predicted that the red squirrel would persist in forests in Scotland and in some areas of England, but would be rare in Wales. Over Great Britain as a whole, the gray squirrel is likely to occur in about twice as many forest areas as the red squirrel.
Sea Turtle Conservation and Halfway Technology*
Authors: FRAZER NAT B.
Published: March 2003

Abstract: How we define a problem often determines what we are willing to consider as a solution. When we define the impending extinction of a sea turtle species solely in terms of there being too few turtles, we are tempted to think of solutions solely in terms of increasing the numbers of turtles. Hence, some of our attempts to conserve sea turtles involve “halfway technology,” which does not address the causes of or provide amelioration for the actual threats turtles face. Programs such as headstarting, captive breeding, and hatcheries may serve only to release more turtle into a degraded environment in which their parents have already demonstrated that they cannot flourish. Furthermore, captive programs may keep turtles from serving important ecological functions in the natural environment, or place them at some disadvantage relative to their natural counterparts once released. Such programs can be contrasted with more appropriate technologies that directly address and correct particular problems encountered by sea turtles without removing them from their natural habitat. For example, installing turtle excluder devices in shrimp trawl nets will reduce mortality of adults and larger juvenile sea turtles, and using low pressure sodium lighting on beaches may prevent hatchlings and nesting females from becoming disoriented. In the final analysis, we need clean and productive marine and coastal environments. Without a commitment to such long term goals, efforts to protect sea turtles will be futile.
Assessment of the Environmental Risk Posed by an Exotic Fish: The Proposed Introduction of Channel Catfish (Ictalurus punctatus) to New Zealand
Authors: TOWNSEND COLIN R. , WINTERBOURN MICHAEL J.
Published: March 2003

Abstract: In 1987, a proposal was made to introduce channel catfish (Ictalurus punctatus) into New Zealand for aquaculture. An environmental impact assessment in support of the proposal incorporated details of channel catfish biology, its value to people, diseases, the history of introductions elsewhere, and possible impacts on New Zealand biota should the species become established in the wild. Although information on the environmental impacts of channel catfish introduced to other countries was limited and inadequate for assessing potential effects on freshwater ecosystems in New Zealand, a permit was granted to import fertilized eggs. These were hatched in quarantine, and subject to the favorable outcome of environmental trials were to be released for aquaculture. Subsequently, the requirement for trials was abandoned and instead an independent, two‐man review team (the authors) was appointed to advise the Minister of Fisheries on whether the environmental risk posed by channel catfish was acceptable. The team considered the impact assessment and additional submissions from interested parties. The team concluded that there was a high probability that fish would escape and that they would be capable of breeding and growing in a wide range of freshwater environments throughout much of New Zealand.

Because channel catfish are omnivorous, they would probably prey on at least some native fish species and introduced salmonids, invertebrates including freshwater crayfish, and aquatic macrophytes. Competition to the detriment of other fishes was also considered likely. Furthermore, the low species diversity and ecological simplicity of fish communities in New Zealand could allow channel catfish opportunities not found within their natural range, as in parts of western North America where they have had significant impacts on freshwater communities. Because the evidence indicated that one or more valued species was likely to suffer a decline in abundance or distribution if channel catfish were introduced, the review team recommended that the environmental risk posed by the fish was unacceptable. The recommendation was accepted by the Minister of Fisheries and all the channel catfish held in quarantine were destroyed. This case clearly demonstrated weaknesses in the importation procedure in New Zealand and subsequently some changes have been made. In general, we recommend a four‐step importation procedure comprising (1) environmental impact assessment, (2) publicity, (3) independent review, and (4) implementation. We suggest that the second step is most crucial.