bluuebunny/crossref_metadata_2025_split huggingface dataset:
Litterfall dynamics and nitrogen use efficiency in two evergreen temperate rainforests of southern Chile
Authors: Pérez Cecilia A. , Armesto Juan J. , Torrealba Cristian , Carmona Martín R. 
Published: November 2003

Abstract  In unpolluted regions, where inorganic nitrogen (N) inputs from the atmosphere are minimal, such as remote locations in southern South America, litterfall dynamics and N use efficiency of tree species should be coupled to the internal N cycle of forest ecosystems. This hypothesis was examined in two evergreen temperate forests in southern Chile (42°30′S), a mixed broad‐leaved forest (MBF) and a conifer forest (CF). Although these forests grow under the same climate and on the same parental material, they differ greatly in floristic structure and canopy dynamics (slower in the CF). In both forests, biomass, N flux, and C/N ratios of fine litterfall were measured monthly from May 1995 to March 1999. There was a continuous litter flux over the annual cycle in both forests, with a peak during autumn in the CF. In the MBF, litterfall decreased during spring. In both forests, the C/N ratios of litterfall varied over the annual cycle with a maximum in autumn. Annual litterfall biomass flux (Mean ± SD = 3.3 ± 0.5 vs 2.0 ± 0.5 Mg ha−1) and N return (34.8 ± 16 vs 9.1 ± 2.8 kg N ha−1) were higher in the MBF than in the CF. At the ecosystem level, litterfall C/N was lower in the MBF (mean C/N ratio = 60.1 ± 15, n = 3 years) suggesting decreased N use efficiency compared with CF (mean C/N ratio = 103 ± 19.6, n = 3 years). At the species level, subordinated (subcanopy) tree species in the MBF had significantly lower C/N ratios (<50) of litterfall than the dominant trees in the CF and MBF (>85). The litterfall C/N ratio and percentage N retranslocated were significantly correlated and were lower in the MBF. The higher net N mineralization in soils of the MBF is related to a lower N use efficiency at the ecosystem and species level.
Effects of cover reduction on mulgara Dasycercus cristicauda (Marsupialia: Dasyuridae), rodent and invertebrate populations in central Australia: Implications for land management
Authors: Masters Pip , Dickman Chris R. , Crowther Mathew 
Published: November 2003

Abstract  This study investigates the effect of cover reduction on the mulgara, Dasycercus cristicauda, a small marsupial classified as vulnerable to extinction, which occurs in areas of central Australia dominated by hummock grasslands. Loss or degradation of spinifex has been implicated in population declines of this species previously, but the importance of cover in maintaining quality habitat remains speculative. To determine the effect on D. cristicauda of cover reduction, caused by the harvesting of spinifex, we monitored population changes and changes in prey resources (rodents and invertebrates) before and after spinifex harvesting took place at a site near the Ayers Rock Resort, Northern Territory, Australia. Ten plots, each of 8.75 ha, were established and sampled from May 1994 to October 1995. Harvesting took place on five plots in August 1994, which reduced spinifex cover from 46 to 21% and the amount of spinifex >0.25 m high from 42 to 2%. Harvesting did not significantly affect the number of D. cristicauda known to be alive or captured despite other studies indicating that cover is an important habitat attribute. There was also no evidence that cover reduction impacted on the biomass of the invertebrate food resources. However, there was a significant reduction in the number of rodents captured. The lack of a response to cover reduction by D. cristicauda is possibly because the cover of Triodia remained high enough (above 15%) to sustain animals, and harvested areas were relatively small. This study therefore suggests that D. cristicauda can tolerate a moderate local reduction in cover of its preferred habitat. However, it remains possible that other land use practices that cause severe reduction of cover (including clearing for mining or fire prevention, grazing which may result in spinifex reduction through trampling, and fire management) will have more dramatic effects on D. cristicauda. Evaluation of such effects should be a priority for future research.
Characterizing fish–habitat associations in streams as the first step in ecological restoration
Authors: Bond N. R. , Lake P. S. 
Published: November 2003

Abstract  Habitat availability is often regarded as the primary factor that limits population and community recovery in degraded ecosystems, and physical habitat is thus often targeted in restoration. The identification of which habitat(s) to attempt to restore is a critical step in the restoration process, but one for which there is often a paucity of useful information. Here we examine the distribution of fish in three lowland streams in Victoria, Australia, that have been degraded by severe sedimentation. We aim to identify habitats that are associated with high abundances of native fish, and that thus might be appropriate to target in habitat restoration. Associations between native fish abundances and physical habitat characteristics were examined at three spatial scales (among streams, among sites and within sites) to determine the types of habitat to which fish respond, and the scales over which these responses occur. Of the four species of native fish found in the streams, three (Galaxias olidus Günther, Gadopsis marmoratus (Richardson) and Nanoperca australis Günther) showed significant habitat associations at small spatial scales (i.e. within sites). In particular, these species were generally found in deeper water, and in close proximity to cover (typically either coarse or fine woody debris or vegetation). Differences in habitat availability among sites and streams were less influential, except in the case of G. marmoratus, which was completely absent from both the ephemeral streams. Although our results suggest that these species collectively respond to habitat at several spatial scales, fish distributions were allied to the presence of habitat structure at the scale of metres, the smallest spatial scale examined. We hypothesize that fish abundances are currently limited by the low availability of habitat at these small spatial scales. It may therefore be possible to increase fish abundances in these creeks by augmenting the amount of available habitat via stream restoration.
Effect of abiotic factors on the foraging strategy of the orb‐web spider Argiope keyserlingi (Araneae: Araneidae)
Authors: Herberstein M. E. , Fleisch A. F. 
Published: November 2003

Abstract  Environmental conditions such as light level, background contrast and temperature might influence a spider's prey capture success and risk of predation. Thus it may often be advantageous for spiders to adjust web‐building behaviour in response to variation in these environmental conditions. This hypothesis was examined in a study of the construction of webs and web decorations (conspicuous strands of silk at the hub of the web) of the orb‐web spider Argiope keyserlingi. Web decorations are thought to have one or more separate functions. They may attract prey, deter predators or advertise the web to oncoming birds, thus preventing web damage. In this series of experiments, relationships between weather parameters and the construction of webs and web decorations were considered. In complementary laboratory experiments, A. keyserlingi spiders were exposed to two different light levels (700 and 90 lx), background contrasts (black and white) and temperature conditions (20 and 26°C). Of the available weather parameters, only temperature was significantly related to web decorating behaviour but not to web size. In the laboratory, temperature also influenced web‐decorating behaviour, and spiders in dim light (700 lx) constructed larger webs and longer decorations. Background contrast did not significantly alter web size or web decorations. These data suggest that when prey availability is reduced at low temperatures, spiders may use web decorations to attract prey to the web. Similarly, in dim light, spiders may build more and larger decorations to increase the visual signal to approaching prey or to advertise the web to oncoming birds.
Use of a polymeric device to deliver growth factors to a healing fracture
Authors: Wong Wicky C. F. , Yu Yan , Wallace Andrew L. , Gianoutsos Mark P. , H. Sonnabend David , Walsh William R. 
Published: November 2003

Background:  Fracture healing is a cascade of events regulated by systemic and local factors. Local growth factors are believed to play an integral role. The present study evaluates the effects of basic fibroblast growth factor (bFGF) and insulin‐like growth factor‐1 (IGF‐1) using a controlled delivery system in a closed rodent femoral fracture model.Methods:  Female Wistar rats (n = 144) were used in the present study. Animals were randomly allocated to six groups, with each group divided into three time‐points of 2, 4 and 8 weeks. Two groups had growth factor administered. The others had no operation or sham operations. Growth factors were delivered to the fracture site using a specialised delivery system. This consisted of a Kirschner‐wire coated with ethylene vinyl acetate co‐polymer embedded with growth factors, inserted as an intramedullary nail. Fractures were effected with a three‐point bending device. Femurs were tested in four‐point bending and structural properties of peak load and stiffness were obtained from the load‐displacement graphs. Specimens were prepared for qualitative analysis under a light microscope and using immunohistochemistry, specimens were analysed for expression of bFGF, IGF‐1 and transforming growth factor β (TGF‐β).Results:  The growth factor‐treated groups exhibited larger calluses at 2 and 4 weeks. Four‐point bending showed weaker structural properties (stiffness and peak load) at 4 weeks in both growth factor‐treated groups. Administration of bFGF or IGF‐1 increased the ratio of cartilaginous to mesenchymal tissues in the fracture callus compared with non‐treated animals at 2 and 4 weeks. Immunostaining intensity and distribution of both growth factors in the treated groups was greater than the non‐treated groups.Conclusion:  Exogenous delivery of bFGF or IGF‐1 alters the course of fracture healing.
Transfer function index: is it a reliable method for vein graft surveillance?
Authors: Tan Chuan Ping , Civil Ian 
Published: November 2003

Introduction:  Duplex ultrasound scanning is currently the best available non‐invasive method for vein graft surveillance. However, it is expensive and its results are highly operator dependent. The aim of the present study is to compare, another non‐invasive method of graft surveillance, the transfer function index (TFI), with duplex ultrasound scanning in identifying significant stenoses in infrainguinal saphenous vein bypass grafts.Methods:  Initially a retrospective pilot study was carried out between 1 January and 30 June 2002. Patients were identified from the vascular surgical operation database. The ultrasound report and TFI result of each patient were reviewed. Then a prospective comparative study was carried out between 1 July and 31 December 2002. Duplex ultrasound and TFI studies were undertaken at the 3 month interval. Comparisons were made between the accuracy and predictive value of ultrasound versus TFI in assessing significant graft stenosis.Results:  In the present retrospective study TFI measurement was significantly lower in the at‐risk grafts than in the normal grafts (P = 0.001). In the prospective group TFI was again found to be significantly lower in the at‐risk group (mean TFI 0.86) than in the normal group (mean TFI 1.064, P = 0.001). The sensitivity and specificity of the TFI were 92% and 97%, respectively. The accuracy of TFI was calculated to be 98%.Conclusion:  TFI is an accurate non‐invasive method of vascular graft surveillance. TFI can be carried out in the vascular clinic and is quick and inexpensive. Normally TFI could replace duplex ultrasound surveillance, with ultrasound being reserved for those with an abnormal TFI.
Fixation of femoral fractures in multiple‐injury patients with combined chest and head injuries
Authors: Nau Thomas , Aldrian Silke , Koenig Franz , Vécsei Vilmos 
Published: November 2003

Background:  The purpose of the present paper was to study the effects of a femoral shaft fracture and its early stabilization on the morbidity, mortality, and outcome of multiple‐injury patients with combined blunt head and chest trauma. The clinical course of patients was analysed using a prospectively gathered data base.Methods:  Out of 352 multitrauma patients, from September 1992 to June 2000, we identified 28 patients with combined blunt chest and head trauma (abbreviated injury scale ≥ 2) and a femoral fracture as the study group. A total of 120 patients with combined chest and head trauma but without femoral fracture formed the control group. Parameters examined included injury severity, injury pattern, haemodynamics at admission, mortality, duration of ventilation, length of stay in intensive care unit, and outcome.Results:  There were no significant differences regarding the demographics and injury severity (injury severity score) between the two groups. No significant differences were found in terms of mortality, duration of ventilation\intensive care unit stay and outcome. Injury severity (P < 0.0001), age (P = 0.0153), and haemodynamics at admission (P = 0.0036) were shown to have a significant effect on mortality and outcome. Injury severity (P < 0.0001) and age (P = 0.017) had a significant effect on the duration of ventilation\intensive care unit stay.Conclusions:  The present study suggests that a femoral shaft fracture and its early stabilization in a multitrauma patient with combined chest and head injury do not adversely affect mortality and outcome and supports aggressive surgical management for these patients.
Measuring clinical audit and peer review practice in a diverse health care setting
Authors: Spigelman Allan D. , Swan Judith 
Published: November 2003

Background:  A measurement system was devised to determine the extent of clinical audit and peer review across the Hunter Area Health Service, to compare changes over time and to assess the effect of the implementation of a policy on the conduct of patient safety meetings.Methods:  Two surveys were conducted over consecutive years (2001, 2002). A scoring system was developed based on a 12 point questionnaire. Ten points were given for a ‘yes’ response and zero for a ‘no’ response. Points were also given for frequency of meetings. Statistical analysis was by the Mann−Whitney U‐test. The questionnaire included items on clinical indicators, management of issues arising and whether meetings are multidisciplinary, chaired and points for action minuted and followed up.Results:  One‐hundred and five units provided data for the 2001 survey (100% response rate) and 109 units provided data for the 2002 survey (100% response rate). There was a significant increase in the median score in the 2002 survey (median 101; interquartile range 72−113) when compared with the 2001 Survey (median 91; interquartile range 51−110; P = 0.016). There was an improvement of 9% in units scoring in the highest quartile (90−120 points) and a decrease of 5% in units scoring in the lowest quartile (0−29 points).Conclusions:  This methodology allows for the quantitative measurement of audit and peer review activities across clinical units. It might assist clinicians, professional colleges and departments of health in the further development of the recertification\revalidation process.
Experience in the endoscopic management of large colonic polyps
Authors: Church James M. 
Published: November 2003

Background:  Large colonic polyps present a particular challenge to endoscopists because of the risks of significant haemorrhage, perforation, inadequate polypectomy, or trying to snare an unrecognized cancer. The alternative to endoscopic therapy of large polyps is surgical resection and although minimally invasive techniques are available, risks are significant. Although neither surgery nor endoscopy is a perfect way of treating large colonic polyps, endoscopic resection is usually tried first. Most series of endoscopic polypectomies are small, include both rectal and colonic polyps and have varying size and shape criteria. The purpose of the present study is to describe a large consecutive series of colonic polyps evaluated endoscopically, to determine the chances of performing a safe, effective endoscopic polypectomy.Methods:  All colonic polyps>20 mm in maximum dimension assessed during colonoscopy from 1989 to 2002 were reviewed. Rectal polyps were excluded. Demographic data for the patients were abstracted, as were data regarding the outcomes of polyp assessment and treatment. Primary end‐points were: the need for surgical resection, the incidence of postpolypectomy complications and the persistence of the index polyp at follow up. Independent variables included the endoscopically assessed size of the polyps, the year in which the polypectomy took place, the shape of the polyps and their location within the colon.Results:  During the period under review 311 large polyps were removed from 252 different patients. Of these, 263 polyps were removed endoscopically and 48 polyps were removed surgically. An additional 18 endoscopically removed polyps ultimately needed surgery for recurrence or malignancy. There were no deaths but 19 complications of endoscopic polypectomy (17 late haemorrhage and two postpolypectomy syndrome). At first follow up, 22% of polyps had persisted, this decreased to 14% at second follow up and 7% at third. Complications were more common in right sided polyps and in flat or sessile lesions. Pedunculated polyps never persisted or recurred and had the lowest rate of surgery. Larger polyps had higher rates of advanced histology, complications, polyp persistence and the need for surgery.Conclusions:  Polyp size, location and shape influence the results of endoscopic resection of large colonic polyps. Polyps>30 mm in maximum diameter are significantly more advanced histologically but also significantly more difficult to treat successfully than those <30 mm. However, size alone is rarely a contraindication to endoscopic resection.
Biomechanical analysis of five fixation techniques used in glenohumeral arthrodesis
Authors: Miller Bruce S. , Harper Wade P. , Gillies R. Mark , Sonnabend David H. , Walsh William R. 
Published: November 2003

Background:  The purpose of the present study is to compare five fixation techniques in shoulder fusion. The most common complications resulting from shoulder fusion, non‐union and unacceptable arm position, might reflect a failure to achieve rigid fixation during the surgical procedure.Methods:  Twenty‐five shoulder fusions were carried out on human cadaveric specimens using the following techniques: screw fixation, external fixation, external fixation supplemented with screw fixation, single plate fixation and double plate fixation. Each specimen was tested on a servohydraulic machine to determine stiffness.Results:  There was a statistically significant difference in bending and torsional stiffness between all five fixation techniques. Normalized bending (B) and torsional stiffness (T), in descending order, were: double plate (B = 1.00, T = 1.00), single plate (B = 0.77, T = 0.89), external fixation with screws (B = 0.68, T = 0.74), external fixation alone (B = 0.40, T = 0.53), and screws alone (B = 0.13, T = 0.26).Conclusion:  The risk of the most common complications resulting from shoulder fusion might be minimized if these biomechanical findings are applied to surgical decision making.
Tumour involvement of the re‐excision specimen following clear local excision of breast cancer with positive margins
Authors: Ooi Corinne W. L. , Serpell Jonathan W. , Rodger Alan 
Published: November 2003

Background:  Breast conservation surgery and subsequent radiotherapy is an acceptable method of treating breast cancer. Complete excision of the primary tumour is important to minimize the risk of local recurrence. Re‐excision is usually carried out if the initial primary tumour excision shows positive margins. However, a significant proportion of re‐excision specimens are negative for tumour. The aim of the present study was to identify factors predicting a histologically positive re‐excision specimen.Methods:  The case records of all patients with invasive and in situ breast cancer referred to the William Buckland Radiotherapy Centre between January 1996 and December 2001 were reviewed. The factors evaluated were patient age, whether or not tumours were detected by screening mammography, use of hook‐wire needle localization, whether tumours were marked with orientating sutures, histopathological characteristics of the tumour and involvement of axillary nodes. Univariate analysis was performed.Results:  In the study period, a total of 1128 patients were reviewed. Of these, 742 underwent breast conservation surgery. Twenty‐nine (3.9%) of the 742 had positive surgical margins and underwent re‐excision. Data were insufficient for six, leaving 23 patients eligible for the study. The number of patients entering the study was small, limiting the statistical analysis. Of these, 21 patients had invasive cancer and two patients had ductal carcinoma in situ only. Of 23 re‐excisions, 11(48%) contained residual tumour. Univariate analysis of the data revealed no significant factors that were likely to predict tumour in the re‐excision specimen. The local recurrence after re‐excision in patients with positive margins was 4.3%.Conclusion:  The results suggest that it is not possible to predict which patients will have tumour in the re‐excision specimen. However, approximately 50% of re‐excision specimens showed residual cancer. Therefore it is recommended that all excisions with positive margins need further surgery.
Competitive coexistence in spatially structured environments: a synthesis
Authors: Amarasekare Priyanga 
Published: November 2003

AbstractTheoretical developments in spatial competitive coexistence are far in advance of empirical investigations. A framework that makes comparative predictions for alternative hypotheses is a crucial element in narrowing this gap. This review attempts to synthesize spatial competition theory into such a framework, with the goal of motivating empirical investigations that adopt the comparative approach. The synthesis presented is based on a major axis, coexistence in spatially homogeneous vs. heterogeneous competitive environments, along which the theory can be organized. The resulting framework integrates such key concepts as niche theory, spatial heterogeneity and spatial scale(s) of coexistence. It yields comparative predictions that can guide empirical investigations.