bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coarse particulate organic matter dynamics in small streams: towards linking function to physical structure
Authors: RICHARDSON JOHN S. , HOOVER TRENT M. , LECERF ANTOINE 
Published: July 2009

Summary1. Organic matter derived from terrestrial vegetation (detritus) is a key basal resource in many food webs, including those of streams. Once detritus enters a stream, it is either retained or transported, but the rates of within‐reach retention depend on structural characteristics of the stream channel, physical properties of the detrital particles and hydrology. Each of these attributes varies in time and space and the magnitude of variation may be affected by structural changes wrought by land‐use. We developed a heuristic model framework in an attempt to find a minimal model that captures the essential temporal dynamics of coarse particulate detritus in small streams.2. The dynamics of our minimal model are driven by several frequently measured variables. Rate of litter breakdown, average transport distance of a particle, discharge and temperature are the primary variables. In addition, we tested the effects of altering assumptions about the nature of particle type and the effect of channel roughness on transport rates.3. The model produced patterns of detrital standing stocks generally similar to those measured by empirical studies in small streams. Discharge‐dependent transport relations are relatively rare, but our assumed pattern of a sigmoid relationship between transport and discharge produced reasonable outputs.4. We parameterised the model using data for small streams in coastal British Columbia, Canada. The outputs of the model indicate that channel roughness has a more profound effect on small, mobile particles, such as conifer needles, than on angiosperm leaves, such as alder. The model also indicates that the largest proportion of detritus is broken downin situin all model scenarios.5. A major limitation to this model and the literature is a scarcity of detail of leaf interception and entrainment processes in streams. Progress towards integrating ecosystem functions and the dynamics of hydromorphology require integrating these physical drivers with biological processes. We present our model to emphasise that progress towards generalisable models of detrital dynamics is possible if links between physical structure and function can be made explicit.
Low‐level effects of inert sediments on temperate stream invertebrates
Authors: LARSEN S. , ORMEROD S. J. 
Published: July 2009

Summary1. The delivery, entrainment and deposition of inert fine sediments are among the most significant contributors to stream and river impairment worldwide. Associated ecological effects have been observed frequently, but specific experiments to identify sensitivity and avoidance behaviour in stream organisms are few, particularly in headwaters.2. In a field‐experiment, we added fine sand at low levels (c. 4–5 kg m−2) to 10 m reaches of two replicate headwater streams in the Usk catchment (Wales, U.K.) over two periods (autumn and summer). Upstream reaches were used as control in a classic before‐after‐control‐impact design. Invertebrate drift and benthic composition were measured for 2 days before and 1 day after sediment impact.3. Sediment addition significantly increased overall drift density (by 45%) and propensity (by 200%), with effects largest on the night following addition rather than immediately (i.e. within 9 h). The mayflies Baetis rhodani, B. muticus and Ecdyonurus spp., simuliid and chironomid dipterans, and helodid beetles were the strongest contributors.4. There were no marked effects on benthic composition, but density declined in treated reaches by 30–60%, particularly in B. rhodani, Ecdyonurus spp. and Leuctra hippopus + L. moselyi.5. All effects were consistent between both seasons and streams.6. These data show how even low‐level, short‐term, increases in fine sediment loading to upland, stony streams can reduce overall benthic density through increased drift. We suggest that the likely cause of the delayed drift response was a change in habitat quality which prompted avoidance behaviour. Longer‐term experiments are required to assess whether these effects reduce fitness or explain the losses of some types of organisms observed recently in sediment‐impaired reaches of this and other catchments.
Response of grazing impacts of an algivorous fish (Pseudogastromyzon myersi: Balitoridae) to seasonal disturbance in Hong Kong streams
Authors: YANG GRACE Y. , DUDGEON DAVID 
Published: July 2009

Summary1. Manipulative experiments were carried out in four Hong Kong streams (two shaded, two unshaded) to investigate the impact of grazing by an algivorous fish, Pseudogastromyzon myersi, on benthic algal biomass and assemblage composition. Experiments were conducted and repeated during both the dry and wet seasons to determine whether spate‐induced disturbance modified any grazing effect. Treatments comprised fish exclusion and inclusion via closed and open cages, with a no‐cage treatment used as a control for the cage effect. Treatments were maintained for 4 weeks in each experimental run.2. Grazing by P. myersi reduced benthic algal biomass and the organic matter content of periphyton in open cages and the no‐cage treatment relative to closed cages. The similarity between open‐cage and no‐cage treatments was evidence that the overall difference among treatments was caused by limiting fish access to closed cages and not merely an artifact of caging. Grazing effects were broadly similar in all streams, but there was a significant statistical interaction between treatments and seasons.3. Analysis of dry‐season data matched the overall trend in inter‐treatment differences, confirming the effects of grazing by P. myersi on algal biomass and periphyton organic matter. Significant differences in algal assemblage composition between closed‐cage and no‐cage treatments during the dry season reflected reductions in the abundance of erect, stalked diatoms (Gomphonema) and filamentous cyanobacteria (Homeothrix). Removal of these vulnerable overstorey algae by P. myersi resulted in greater abundance of understorey diatoms (Achnanthes and Cocconeis) in the no‐cage treatment in all streams during the dry season. The composition of algal assemblages in open cages was intermediate between the other two treatments.4. Although fish densities were greater in all streams during the wet season, spate‐induced disturbance obscured grazing effects and there were no significant differences among treatments attributable to fish grazing. Seasonal variation in impacts of P. myersi grazing provides support for the harsh‐benign hypothesis, and confirms that biotic factors are less important controls of stream algal biomass and assemblage structure during periods (i.e. the wet season in Hong Kong) when abiotic disturbances are frequent or intense.
Transport and settlement of organic matter in small streams
Authors: HOOVER TRENT M. , MARCZAK LAURIE B. , RICHARDSON JOHN S. , YONEMITSU NOBORU 
Published: July 2009

Summary1. After it enters streams, terrestrially derived organic matter (OM) rapidly absorbs water. Using field and laboratory experiments, we examined how this process affected the buoyancy, settling velocity, transport distance and retention locations of four types of organic matter typically found in Pacific coastal streams (‘flexible’ red alder leaves and three ‘stiff’ particle types – Douglas‐fir needles, red cedar fronds and Douglas‐fir branch pieces).2. Immersion in water rapidly changed the physical characteristics of alder leaves, Douglas‐fir needles and red cedar fronds, which all reached constant still‐water settling velocities after only a few days of soaking. In contrast, the settling velocity of branch pieces continued to increase for 13 days, eventually reaching much higher values than any other OM type. Dried alder leaves became negatively buoyant after only two days of immersion, while other types took substantially longer (up to 24 days) before the specific gravity of all particles was >1.3. We released saturated OM particles in an experimental channel and found that all particle types travelled further in a fast, shallow ‘riffle’ than a slow, deep ‘pool’. Comparisons with a passive settlement null model indicated that leaves were retained more rapidly than expected in the riffle (by large protruding stones), while the three stiff particle types travelled further than expected (probably due to turbulent suspension) and were retained when they settled in deeper water between larger stones. In pools, passive settlement appeared to dominate the retention of all OM types, with leaves travelling furthest.4. These retention patterns corresponded well with those observed when saturated OM particles collected in the field were released in two pools and two riffles in a second‐order coastal stream.5. When the experimental channel and in‐stream data were combined, the retention rates of the three stiff OM types were closely related to calculated Rouse numbers (Rouse number = particle settling velocity/shear velocity), whereas the retention rate of alder leaves was not. This suggests that different physical mechanisms are responsible for the retention of leaves and stiff OM types in shallow streams.
Regression modelling of correlated data in ecology: subject‐specific and population averaged response patterns
Authors: Fieberg John , Rieger Randall H. , Zicus Michael C. , Schildcrout Jonathan S. 
Published: July 2009

Summary 1. Statistical methods that assume independence among observations result in optimistic estimates of uncertainty when applied to correlated data, which are ubiquitous in applied ecological research. Mixed effects models offer a potential solution and rely on the assumption that latent or unobserved characteristics of individuals (i.e. random effects) induce correlation among repeated measurements. However, careful consideration must be given to the interpretation of parameters when using a nonlinear link function (e.g. logit). Mixed model regression parameters reflect the change in the expected response within an individual associated with a change in that individual’s covariates [i.e. a subject‐specific (SS) interpretation], which may not address a relevant scientific question. In particular, a SS interpretation is not natural for covariates that do not vary within individuals (e.g. gender). 2. An alternative approach combines the solution to an unbiased estimating equation with robust measures of uncertainty to make inferences regarding predictor–outcome relationships. Regression parameters describe changes in the average response among groups of individuals differing in their covariates [i.e. a population‐averaged (PA) interpretation]. 3. We compare these two approaches [mixed models and generalized estimating equations (GEE)] with illustrative examples from a 3‐year study of mallard (Anas platyrhynchos) nest structures. We observe that PA and SS responses differ when modelling binary data, with PA parameters behaving like attenuated versions of SS parameters. Differences between SS and PA parameters increase with the size of among‐subject heterogeneity captured by the random effects variance component. Lastly, we illustrate how PA inferences can be derived (post hoc) from fitted generalized and nonlinear‐mixed models. 4. Synthesis and applications. Mixed effects models and GEE offer two viable approaches to modelling correlated data. The preferred method should depend primarily on the research question (i.e. desired parameter interpretation), although operating characteristics of the associated estimation procedures should also be considered. Many applied questions in ecology, wildlife management and conservation biology (including the current illustrative examples) focus on population performance measures (e.g. mean survival or nest success rates) as a function of general landscape features, for which the PA model interpretation, not the more commonly used SS model interpretation may be more natural.
Climate change, connectivity and conservation decision making: back to basics
Authors: Hodgson Jenny A. , Thomas Chris D. , Wintle Brendan A. , Moilanen Atte 
Published: July 2009

Summary 1. The challenge of climate change forces us to re‐examine the assumptions underlying conservation planning. 2. Increasing ‘connectivity’ has emerged as the most favoured option for conservation in the face of climate change. 3. We argue that the importance of connectivity is being overemphasized: quantifying the benefits of connectivity per se is plagued with uncertainty, and connectivity can be co‐incidentally improved by targeting more concrete metrics: habitat area and habitat quality. 4. Synthesis and applications. Before investing in connectivity projects, conservation practitioners should analyse the benefits expected to arise from increasing connectivity and compare them with alternative investments, to ensure as much biodiversity conservation and resilience to climate change as possible within their budget. Strategies that we expect to remain robust in the face of climate change include maintaining and increasing the area of high quality habitats, prioritizing areas that have high environmental heterogeneity and controlling other anthropogenic threatening processes.
Specimen thickness dependence of hydrogen evolution during cryo‐transmission electron microscopy of hydrated soft materials
Authors: YAKOVLEV S. , MISRA M. , SHI S. , LIBERA M. 
Published: July 2009

SummaryThe evolution of hydrogen from many hydrated cryo‐preserved soft materials under electron irradiation in the transmission electron microscope can be observed at doses of the order of 1000 e nm−2 and above. Such hydrogen causes artefacts in conventional transmission electron microscope or scanning transmission electron microscopy (STEM) imaging as well as in analyses by electron energy‐loss spectroscopy. Here we show that the evolution of hydrogen depends on specimen thickness. Using wedge‐shaped specimens of frozen‐hydrated Nafion, a perfluorinated ionomer, saturated with the organic solvent DMMP together with both thin and thick sections of frozen‐hydrated porcine skin, we show that there is a thickness below which hydrogen evolution is not detected either by bubble observation in transmission electron microscope image mode or by spectroscopic analysis in STEM electron energy‐loss spectroscopy mode. We suggest that this effect is due to the diffusion of hydrogen, whose diffusivity remains significant even at liquid nitrogen temperature over the length scales and time scales relevant to transmission electron microscopy analysis of thin specimens. In short, we speculate that sufficient hydrogen can diffuse to the specimen surface in thin sections so that concentrations are too low for bubbling or for spectroscopic detection. Significantly, this finding indicates that higher electron doses can be used during the imaging of radiation‐sensitive hydrated soft materials and, consequently, higher spatial resolution can be achieved, if sufficiently thin specimens are used in order to avoid the evolution of hydrogen‐based artefacts.
Impact of rituximab‐associated B‐cell defects on West Nile virus meningoencephalitis in solid organ transplant recipients
Authors: Levi Marilyn E. , Quan Dianna , Ho Joseph T. , Kleinschmidt‐DeMasters B. K. , Tyler Kenneth L. , Grazia Todd J. 
Published: July 2009

Levi ME, Quan D, Ho JT, Kleinschmidt‐DeMasters BK, Tyler KL, Grazia TJ. Impact of rituximab‐associated B‐cell defects on West Nile virus meningoencephalitis in solid organ transplant recipients. Clin Transplant 2009 DOI: 10.1111/j.1399‐0012.2009.01044.x © 2009 John Wiley & Sons A/S.Abstract:  Evidence suggests that West Nile virus (WNV) neuroinvasive disease occurs more frequently in both solid organ and human stem cell transplant recipients. The effect of concomitant anti‐B‐cell therapy with rituximab, a CD20+ monoclonal antibody, on WNV infection in this population, however, has not been reported. We describe a case of a patient with alpha‐1‐antitrypsin deficiency who underwent single lung transplantation in 2005 and was maintained on tacrolimus, cytoxan and prednisone. More recently, she had received two courses of rituximab for recurrent A2–A3 grade rejection with concomitant capillaritis and presented six months later with rapid, fulminant WNV meningoencephalitis. Her diagnosis was made by cerebrospinal fluid (CSF) PCR but serum and CSF WNV IgM and IgG remained negative. She received WNV‐specific hyperimmune globulin (Omr‐Ig‐Am®) through a compassionate protocol. She experienced a rapidly progressive and devastating neurological course despite treatment and died three wk after onset of her symptoms. Autopsy revealed extensive meningoencephalomyelitis.
Late conversion of tacrolimus to sirolimus in a prednisone‐free immunosuppression regimen in renal transplant patients
Authors: Chhabra Darshika , Grafals Monica , Cabral Brian , Leventhal Joseph , Parker Michele , Gallon Lorenzo 
Published: July 2009

Chhabra D, Grafals M, Cabral B, Leventhal J, Parker M, Gallon L. Late conversion of tacrolimus to sirolimus in a prednisone‐free immunosuppression regimen in renal transplant patients. Clin Transplant 2009: DOI: 10.1111/j.1399‐0012.2009.01047.x © 2009 John Wiley & Sons A/S.Abstract: Background:  One of the most important causes of graft loss is chronic nephrotoxicity from calcineurin inhibitors. The aim of this study was to evaluate the feasibility and to assess the impact on rejection risk, graft loss and renal allograft function of converting patients from tacrolimus (Tac) to sirolimus (SRL) at one yr post‐transplantation (Tx) using a prednisone‐free immunosuppressive regimen.Methods:  Two hundred fifty‐five kidney transplant patients were induced with Alemtuzumab and maintained on a steroid‐free regimen with Tac and mycophenolate mofetil. Thirty‐seven stable patients (14%) were converted from Tac to SRL at one yr post‐Tx.Results:  The two groups were demographically similar. Mean post‐tx follow‐up was 2.8 ± 0.2 yr. Patient and graft survival were not statistically different. There was no significant difference in acute rejection episodes between the SRL and Tac groups (21% vs. 15%, p = 0.2). Calculated glomerular filtration rate (GFR), in the SRL group at 2.8 yr post‐tx, was 69 ± 13 mL/min from the one month post‐tx GFR of 53 ± 19 and 59 ± 23 mL/min from the one month post‐tx GFR of 56 ± 21 mL/min in the Tac group.Conclusions:  Using a prednisone‐free regimen, the conversion of Tac to SRL at one yr post‐Tx was not associated with an increased risk of acute rejection or graft loss.
Influence of Exogenous Glycine Betaine on Gas Exchange and Biomass Production in Sunflower (Helianthus annuus L.) under Water Limited Conditions
Authors: Iqbal N. , Ashraf M. , Ashraf M. Y. 
Published: July 2009

AbstractThis study investigated whether the exogenous application of glycine betaine (GB) could alleviate the adverse effects of water deficit on sunflower. Two sunflower lines, Gulshan‐98 and Suncross, were subjected to water deficit at the vegetative or the reproductive stages of plant growth. Three levels (0, 50 and 100 mmol l−1) of GB were applied as a pre‐sowing seed treatment or as a foliar spray at the time of initiation of water deficit at the vegetative or reproductive stages. Foliar application of GB at the time of initiation of water deficit treatments showed a marginal increase in shoot biomass in drought‐stressed plants. Exogenously supplied GB as a foliar spray also showed a positive role in reducing the effects of water deficit on net CO2 assimilation rate, transpiration rate and sub‐stomatal CO2 concentration in both sunflower lines. Pre‐sowing seed treatment with GB had no effects on the above‐mentioned physiological and growth attributes in both normally irrigated and drought‐stressed plants. Taken together, foliar application of GB increased net CO2 assimilation rate which in turn showed a slight increase in growth of water‐stressed plants but this increase was not related to stomatal regulation.
Effects of simulated tidal and deep breathing on immature airway contraction to acetylcholine and nerve stimulation
Authors: ANSELL Thomas K. , NOBLE Peter B. , MITCHELL Howard W. , WEST Adrian R. , FERNANDES Lynette B. , MCFAWN Peter K. 
Published: July 2009

ABSTRACTBackground and objective: In adults, respiratory movements, such as tidal and deep breaths, reduce airway smooth muscle force and cause bronchodilation. Evidence suggests that these beneficial effects of oscillatory strain do not occur in children, possibly because of reduced coupling of the airways to lung tissue or maturational differences in the intrinsic response of the airways to oscillatory strain.Methods: The bronchodilator effects of oscillatory strain were compared in isolated airway segments from immature (3–4 weeks and 8–10 weeks old) and mature (18–20 weeks old) pigs. The lumen of fluid‐filled bronchi was volume‐oscillated to simulate tidal breaths and 0.5×, 2× and 4× tidal volumes. Contractions to acetylcholine and electrical field stimulation were recorded from the lumen pressure and were compared under oscillating and static conditions. Airway stiffness was determined from the amplitude of the lumen pressure cycles and the volume of oscillation.Results: Volume oscillation reduced contractions to acetylcholine and electrical field stimulation in an amplitude‐dependent manner and the percentage reduction was the same for the different stimuli across all age groups. There was no difference in the relaxed dynamic stiffness of airways from the different age groups.Conclusions: The intrinsic response of the airway wall to equivalent dynamic strain did not differ in airways from pigs of different ages. These findings suggest that mechanisms external to the airway wall may produce age‐related differences in the response to lung inflation during development.
Residual fraction as a parameter to predict bladder outlet obstruction in men with lower urinary tract symptoms
Authors: Ku Ja Hyeon , Cho Sung Yong , Oh Seung‐June 
Published: July 2009

Objectives:  To determine whether noninvasive tests including the residual fraction are reliable for the diagnosis of bladder outlet obstruction (BOO).Methods:  A total of 212 men (median age 68, range 44–89 years) were included in the present study. The median serum prostate‐specific antigen level and prostate volume were 1.3 ng/mL (range 0.2 to 9.4) and 37.9 mL (range 11.3 to 148.0), respectively.Results:  Among the variables analyzed in the multivariate model, the likelihood of BOO varied by the total prostate volume, with a 3.6‐fold higher odds for ≥40 mL than for <40 mL (odds ratio [OR], 3.616; 95% confidence interval [CI], 1.217–10.749; P = 0.021). In the same model, a low maximal flow rate (Qmax) (OR, 2.840; 95% CI, 1.260–6.401; P = 0.012) and high residual fraction (OR, 7.103; 95% CI, 1.924–26.225; P = 0.003) were associated with an increased likelihood of BOO. The sensitivity and specificity for predicting BOO using a total prostate volume of 40 mL or greater were 73.7% and 65.2%, respectively. Using a Qmax cut‐off of 12 mL/s or less for predicting BOO, the sensitivity and specificity were 77.2% and 54.2%, respectively. Prediction of the BOO by the residual fraction only had a sensitivity and specificity, for a residual fraction of less than 20%, of 75.4% and 67.7%, respectively.Conclusions:  The presence or absence of BOO might be predicted using non‐invasive methods. The residual fraction may help with patient management by better predicting the likely patient classification from pressure‐flow studies.