bluuebunny/crossref_metadata_2025_split huggingface dataset:
Compositional similarity and the distribution of geographical range size for assemblages of native and non‐native species in urban floras
Authors: La Sorte Frank A. , McKinney Michael L. 
Published: October 2006

ABSTRACTThere is evidence that, within a region, non‐native species introduced from nearby sources (extralimital native) promote homogenization and non‐native species introduced from distant sources (exotic) promote differentiation of species composition. A possible explanation for these associations is that they are related to differences in the distribution of geographical range size. We test this by examining geographical ranges, delineated within a defined region, for assemblages of vascular plants in eight urban floras in the USA. Across floras, native species had the largest, least variable ranges and the greatest proportion of shared species. Exotic species had the most variable ranges with concentrations of species with small and large ranges and the lowest proportion of shared species. Extralimital natives had concentrations of species with intermediate‐sized ranges and intermediate proportions of shared species. These results suggest that patterns of compositional similarity were associated with the relative strength and equality of two opposing patterns within species range size distributions: species with small vs. large ranges. In general, concentrations of species with small ranges promoted low levels and concentrations of species with large ranges promoted high levels of compositional similarity. However, patterns documented for exotic species will likely continue to develop, possibly taking on new forms, depending on how geographical distributions and the rate of introductions of exotic species change over time. Our findings also suggest that processes underlying these patterns have operated at two spatiotemporal scales. The first scale reflects historical consequences of anthropogenic activities occurring within regional extents that have promoted the introduction of extralimital natives; the second scale reflects modern consequences of anthropogenic activities operating at an increasingly global extent that have promoted the introduction of exotic species.
Species richness correlations among primary producers in boreal forests
Authors: Dynesius Mats , Zinko Ursula 
Published: October 2006

ABSTRACTClose correlations in species numbers may make it possible to indirectly assess the species richness of difficult taxonomic groups by investigating indicator groups, for which data are more easily collected. We asked if species numbers correlate among the four dominating groups of primary producers in boreal forests (liverworts, macrolichens, mosses, and vascular plants) and if substrate affiliation of species (ground vs. other substrates), sample plot size (0.01–1000 m2), and stand age (young vs. old) influence correlation strength. We used three sets of study plots from northern Sweden each including wide ranges of species richness. Although there are large differences in the ecophysiology and substrate use of vascular plants and the two bryophyte groups (mosses and liverworts), we found strong positive correlations among them not previously reported from boreal forests. In contrast, no correlation in total species richness was found between macrolichens and the two bryophyte groups, despite large overlaps in their ecology. We suggest that the positive correlations among land plants (liverworts, mosses, and vascular plants) are linked to positive relationships between site moisture and species number for all three groups. In contrast, total species number of macrolichens has not been shown to be strongly associated with moisture. However, ground‐living lichens and mosses correlated negatively in old forests. This may relate to the inability of macrolichens to exploit shaded and wet old forest ground, a habitat that is used by many moss species. Furthermore, lichens and mosses of ‘other substrates’ correlated positively in old forests, probably because the amount of boulders was positively related to species richness in both groups. Generally, correlations became stronger with increasing plot size, whereas stand age had relatively little influence. We conclude that vascular plants could be used as an indicator group for species richness of mosses and liverworts in boreal landscapes.
Why are ferns regularly over‐represented on state and provincial rare plant lists?
Authors: Wild Matthew , Gagnon Daniel , Bouchard André 
Published: October 2006

ABSTRACTSeveral recent studies have suggested that rare species are not randomly distributed throughout plant taxa. This would appear to apply to North American ferns, which are frequently over‐represented on local lists of rare plant species. However, such lists often paint a skewed portrait of the true situation because of our tendency to recognize the rarity of well‐known and charismatic species while ignoring that of lesser‐known or less‐appreciated species. In order to verify if this over‐representation of ferns is a real and consistent trend throughout local floras in North America, we used data from what we consider to be the most complete and objective available database: NatureServe Explorer (http://www.natureserve.org/explorer/). We compiled data on total vascular plant species, total fern species, as well as rare vascular plant species and rare fern species for each North American subnational (Canadian province or US state) flora. Rare species were defined as those belonging to one of NatureServe's ‘at risk’ categories. The null hypothesis that the contribution of rare ferns to total rare species did not differ from their contribution to the total vascular flora was assessed using χ2. Out of 64 subnational floras, we obtained significantly higher values than expected in 28 cases, and significantly lower in only one case. Similar trends hold true for individual fern families. These tendencies could be related to several factors of anthropogenic, biological, climatological, evolutionary, and geographical origin. However, we believe that the main reason is related to scale, namely the geopolitical units at which rarity is often studied. Our results illustrate one of the problems of a parochial approach to conservation, where the perceived rarity of an entire taxon is exaggerated because of the scale at which rarity is addressed.
Comparing agglomerative clustering and three weed classification frameworks to assess the invasiveness of alien species across spatial scales
Authors: Lawes Roger A. , Murphy Helen T. , Grice Anthony C. 
Published: October 2006

ABSTRACTTo prioritize weed management at the catchment scale, information is required on the species present, their relatively frequency, abundance, and likely spread and impact. The objective of this study was to classify the invasiveness of alien species that have invaded the Upper Burdekin Catchment in Queensland, Australia, at three spatial scales. A combination of three published weed classification frameworks and multivariate techniques were employed to classify species based on their frequency and cover at a range of spatial scales. We surveyed the Upper Burdekin Catchment for alien species, and for each species determined the following distribution indices — site frequency, total cover, transect frequency per site frequency and quadrat frequency per site frequency, cover per quadrat when present, cover per transect when present, and cover per site when present. These indices capture the effect of species abundance and frequency between sites (site frequency and total cover), within sites (transect frequency per site and cover per transect when present), and within transects (quadrat frequency per site frequency and cover per site). They were used to classify the species into seven groups using a hierarchical cluster analysis. The relationship between the indices was explored to determine how effective the small scale, site‐specific indices were at predicting the broader, landscape‐scale patterns. Strong correlations were observed between transect frequency per site and frequency (r2 = 0.89) and cover per transect when present and total cover (r2 = 0.62). This suggests that if a weed is abundant at the site level, it has the potential to occupy large areas of the catchment. The species groupings derived from the application of the three published weed classification frameworks were compared graphically to the groupings derived from the cluster analysis. One of the frameworks classified species into three groups. The other two frameworks classified species into four groups. There was a high degree of subjectivity in applying the frameworks to the survey data. Some of the data were of no relevance to the classification frameworks and were therefore ignored. We suggest that the weed classification frameworks should be used in conjunction with existing multivariate techniques to ensure that classifications capture important natural variations in observed data that may reflect invasion processes. The combined use of the frameworks and multivariate techniques enabled us to aggregate species into categories appropriate for management.
Prospects for population expansion of the exotic aoudad (Ammotragus lervia; Bovidae) in the Iberian Peninsula: clues from habitat suitability modelling
Authors: Cassinello Jorge , Acevedo Pelayo , Hortal Joaquín 
Published: October 2006

ABSTRACTWe studied the geographical distribution and habitat suitability of an introduced ungulate, the aoudad (Ammotragus lervia), that is currently expanding its range in south‐eastern Iberian Peninsula. We assessed the niche of the species using Ecological Niche Factor Analysis (ENFA) on (1) environmental variables (climate and habitat type), and (2) potential aoudad landscape avoidance and human disturbance variables. We compared both niche descriptions to study the impact of human interference on niche selection of the species. ENFA models were calibrated using data on the population expanded from the original release location, in Sierra Espuña mountains, and validated using data from another free‐ranging population, originated independently in the Alicante province. The habitat suitability model for the purely environmental niche predicts a potential distribution along a SW–NE axis in the study area, following the Cordillera Sub‐Bética mountain range, being constrained by low winter precipitation, high altitude, high terrain slope, and the presence of forest. In addition to these ecological traits, roads and landscape use restricted the environmental range potentially available for the species. Since the aoudad is a potential competitor of native ungulates and a threat to endemic flora, prospects for its potential dispersion might be of great conservation value.
Biogeochemical modelling of the rise in atmospheric oxygen
Authors: CLAIRE M. W. , CATLING D. C. , ZAHNLE K. J. 
Published: October 2006

ABSTRACTUnderstanding the evolution of atmospheric molecular oxygen levels is a fundamental unsolved problem in Earth's history. We develop a quantitative biogeochemical model that simulates the Palaeoproterozoic transition of the Earth's atmosphere from a weakly reducing state to an O2‐rich state. The purpose is to gain an insight into factors that plausibly control the timing and rapidity of the oxic transition. The model uses a simplified atmospheric chemistry (parameterized from complex photochemical models) and evolving redox fluxes in the Earth system. We consider time‐dependent fluxes that include organic carbon burial and associated oxygen production, reducing gases from metamorphic and volcanic sources, oxidative weathering, and the escape of hydrogen to space. We find that the oxic transition occurs in a geologically short time when the O2‐consuming flux of reducing gases falls below the flux of organic carbon burial that produces O2. A short timescale for the oxic transition is enhanced by a positive feedback due to decreasing destruction of O2as stratospheric ozone forms, which is captured in our atmospheric chemistry parameterization. We show that one numerically self‐consistent solution for the rise of O2involves a decline in flux of reducing gases driven by irreversible secular oxidation of the crust caused by time‐integrated hydrogen escape to space in the preoxic atmosphere, and that this is compatible with constraints from the geological record. In this model, the timing of the oxic transition is strongly affected by buffers of reduced materials, particularly iron, in the continental crust. An alternative version of the model, where greater fluxes of reduced hydrothermal cations from the Archean seafloor consume O2, produces a similar history of O2and CH4. When climate and biosphere feedbacks are included in our model of the oxic transition, we find that multiple ‘Snowball Earth’ events are simulated under certain circumstances, as methane collapses and rises repeatedly before reaching a new steady‐state.
Mineral activity–composition relations and petrological calculations involving cation equipartition in multisite minerals: a logical inconsistency
Authors: HOLLAND T. J. B. , POWELL R. 
Published: October 2006

AbstractEquipartition is an assumption that preserves the same relative fraction of the cations on each site, originally used just to distribute cations such as Fe and Mg over two or more sites during mineral recalculation. This approximation has been used in almost all thermometry and barometry applications in petrology involving pyroxene, amphibole, chlorite and biotite mica. It has also become the default approach used in deriving activity–composition relations in multisite minerals where details of element partitioning among the sites is unknown and therefore assumed to be random. It is shown that, where a third element, such as Al, resides on just one of the sites, equipartition introduces a serious logical and numerical inconsistency between the enthalpy and entropy of mixing. In particular, application of equipartition is demonstrated to be equivalent to treating the solution as one in which all cations reside on one type of site. For example, in the case of aluminous orthopyroxene the equipartition assumption implies that Fe, Mg and Al are distributed across two identical sites, and that end‐members such as Mg‐tschermak's pyroxene have enthalpies characterized by a totally disordered distribution of Mg and Al over the M2 and M1 sites. Clearly this is unsupportable, and solid solutions should be treated with appropriate thermodynamics for order–disorder. For phases where element partitioning data are unavailable, we offer a simple alternative strategy, using the ordering of Fe and Mg on M1 and M2 sites in biotite as an example.
Acute transfusion reactions in the pediatric intensive care unit
Authors: Gauvin France , Lacroix Jacques , Robillard Pierre , Lapointe Hélène , Hume Heather 
Published: October 2006

BACKGROUND: Acute transfusion reactions (ATRs) are probably underdiagnosed in critically ill children because associated symptoms can frequently be attributed to the patient’s underlying disease. This study was undertaken to determine the incidence, type, imputability, and severity of ATRs observed in a tertiary care pediatric intensive care unit (PICU).STUDY DESIGN AND METHODS: All transfusions of labile blood product administered to consecutive patients admitted to our PICU, between February 2002 and February 2004, were prospectively recorded. For each transfusion, the bedside nurse recorded the patient’s status before, during, and up to 4 hours after the transfusion, as well as the presence of any new sign or symptom suggesting an ATR. Three independent experts retrospectively reviewed all transfusion event reports and hospital charts. The presence, type, imputability, and severity of ATRs were adjudicated by consensus of two of three experts (Delphi method), with predefined criteria.RESULTS: A total of 2509 transfusions were administered to 305 patients during the study. Forty transfusion events (1.6%) were confirmed to be ATRs by expert consensus: 24 febrile nonhemolytic, 6 minor allergic, 4 isolated hypotension, 3 bacterial contamination, 1 major allergic (anaphylactic shock), 1 TRALI, and 1 hemolytic reaction. Imputability of ATRs was probable or possible in 35 cases (88%). ATRs led to an immediate vital threat in 15 percent of cases.CONCLUSION: Improved surveillance of transfusions given to PICU patients and better knowledge of these reactions by health care professionals should improve the safety of transfusions in the PICU.
A study of the agreement between patient self‐assessment and study personnel assessment of bleeding symptoms
Authors: Webert Kathryn E. , Cook Richard J. , Couban Stephen , Carruthers Julie , Heddle Nancy M. 
Published: October 2006

BACKGROUND: Clinical trials investigating new platelet transfusion therapies frequently require the assessment of bleeding for the study outcome. These assessments are commonly performed by study personnel and can be time‐consuming. The purpose of this study was to assess whether patients were able to reliably assess their bleeding status on a daily basis.STUDY DESIGN AND METHODS: Patients admitted to hospital to receive chemotherapy for acute leukemia or to undergo allogeneic peripheral blood progenitor cell transplant were included. Patients were given an introduction to a form for documenting the occurrence of 16 bleeding symptoms. Patients completed this form and were examined daily by a study assessor. A weekly health record review was also performed by a study assessor. The agreement between raters was determined by calculating the raw agreement, chance‐corrected agreement, and chance‐independent agreement.RESULTS: Thirty‐five patients completed 458 assessment forms that were paired with 559 forms completed by a study assessor with 450 matched forms available for analysis (mean, 12.86 per patient). Agreement for most individual bleeding symptoms was high. Thirteen items had agreement greater than 90 percent and all items had agreement greater than 77 percent. The lowest agreement was seen for skin symptoms: petechiae (89.2%), purpura (80.9%), and ecchymosis (77.6%). The negative predictive value of patient self‐assessment was high (range, 71.1%‐100%) whereas the positive predictive value was lower (range, 0%‐86.5%).CONCLUSION: The reliability was very good between patients and study assessors with the patients reporting excellent negative predictive value and variable positive predictive value.
Large‐scale expansion and transplantation of CD34+ hematopoietic cells: in vitro and in vivo confirmation of neutropenia abrogation related to the expansion process without impairment of the long‐term engraftment capacity
Authors: Boiron Jean‐Michel , Dazey Bernard , Cailliot Christian , Launay Béatrice , Attal Michel , Mazurier Frédéric , McNiece Ian K. , Ivanovic Zoran , Caraux Jean , Marit Gérald , Reiffers Josy 
Published: October 2006

BACKGROUND: Herein are reported the results obtained in all multiple myeloma patients transplanted with peripheral blood hematopoietic progenitor cells submitted to ex vivo expansion.STUDY DESIGN AND METHODS: Patients had blood progenitor cell mobilization with cyclophosphamide and filgrastim. CD34+ cells were expanded for 10 days in a medium containing granulocyte–colony‐stimulating factor (G‐CSF), stem cell factor, and megakaryocyte growth and development factor (MGDF). Twenty‐seven patients underwent transplantation with expanded and nonexpanded cells and 7 patients underwent transplantation with expanded cells only.RESULTS: The median fold cell expansion was 29.1. The number of colony‐forming unit–granulocyte‐macrophage (CFU‐GM) and CD34+ cells, and the long‐term culture‐initiating cell (LTC‐IC) activity increased with median fold values of 14.7, 2.75, and 2.25, respectively. Postmyeloablative neutropenia was abrogated in 24 of 27 patients transplanted with expanded cells plus nonexpanded cells. The median duration of severe neutropenia was 0 days and correlated with the number of cells and CFU‐GM infused. Survival was similar to that of a historical control group. Our LTC‐IC and NOD‐SCID mice studies showed that the expanded cells are able of sustaining long‐term hematopoiesis. Seven other patients received transplantation with expanded cells alone. Absolute neutropenia was abrogated in 6 patients. The median duration of neutropenia was 0 days. Two patients who received the lower number of total cells or CFU‐GM had brief secondary neutropenia, which resolved after G‐CSF injections.CONCLUSION: CD34+ cells expanded ex vivo can abrogate absolute and severe neutropenia after high‐dose therapy. The results of the amplification process are strongly related to the delay of hematopoietic recovery.
The Clinical Significance of Nonsustained Ventricular Tachycardia in Patients with Sustained Ventricular Tachyarrhythmias
Authors: Anderson Kelley P. , Mori Motomi ,   ESVEM Trial Investigators
Published: October 2006

Background: Nonsustained ventricular tachycardia (NSVT) predicts mortality in several disorders but its significance in patients with sustained ventricular tachyarrhythmias is unknown. We analyzed the clinical features and outcome associated with NSVT (>; 3 beats at >; 100 beats/min) recorded on a 48‐hour Holter in the absence of antiarrhythmic drugs.Methods: Patients enrolled in the ESVEM trial (n = 486) were grouped according to the duration of the longest recorded episode of NSVT, and in the second analysis, according to frequency of recorded episodes. Assessments were on an intention‐to‐treat basis.Results: Patients without NSVT were more likely to have ischemic heart disease and had significantly lower frequencies of single and paired premature ventricular complexes (PVCs). There were no significant differences with respect to age, sex, presenting arrhythmia, years since last myocardial infarction, functional class, or present ejection fraction. The cumulative probabilities of arrhythmia recurrence and all‐cause mortality at 4 years in patients without NSVT (60%± 7% and 32%± 6%, respectively) were not significantly different than those of patients with NSVT (63%± 3% and 41%± 3%, respectively). Cox regression models indicated that ejection fraction and functional class were significant predictors of outcome, but variables based on the presence, duration, and frequency of recorded episodes of NSVT were not.Conclusions: NSVT is common in patients with spontaneous and inducible sustained ventricular tachyarrhythmias and at least 10 PVCs/hour (ESVEM enrollment criteria), but is not a significant predictor of arrhythmia recurrence, sudden death, or all‐cause mortality in patients with these characteristics.