Rate Of Change In Response Research Articles

Investigating the Consolidation Behaviour of Cement-Bentonite Barrier Materials Containing PFA and GGBS

Cement-Bentonite (CB) barriers are expected to become a sustainable and reliable engineering solution. The deformation of CB is of interest to engineers to comprehend, particularly how CB responds to changes in loading during its construction and service life. The purpose of this study was to examine how samples of CB mixtures behaved during consolidation. This study investigated: (1) the influence of curing time and constituent materials on the consolidation properties of CB samples, (2) the volumetric change and the rate of volumetric change in response to a specific loading condition via consolidation tests. For this purpose, a laboratory consolidation test with a load range of 50 to 3200 kPa was carried out in accordance with BS 1377-7:1990 using the oedometer apparatus. This study discovered that the consolidation characteristics of CB samples are similar to those of overconsolidated soil. The CB sample became more resistant to consolidation under varying loads as curing progressed. The presence of more bentonite resulted in an increase in the recompression index. The inclusion of GGBS contributed to the consolidation characteristics of CB through the following mechanisms: (1) the significant decrease of the degree of consolidation with a curing period longer than 28 days, despite the slow strength development of the early-age curing; (2) the increase of the preconsolidation pressure; and the addition of GGBS was found to be more effective than the addition of more bentonite in increasing the preconsolidation pressure. Doi: 10.28991/CEJ-2023-09-03-02 Full Text: PDF

Tree symbioses sustain nitrogen fixation despite excess nitrogen supply

AbstractSymbiotic nitrogen fixation (SNF) is a key ecological process whose impact depends on the strategy of SNF regulation—the degree to which rates of SNF change in response to limitation by N versus other resources. SNF that is obligate or exhibits incomplete downregulation can result in excess N fixation, whereas a facultative SNF strategy does not. We hypothesized that tree‐based SNF strategies differed by latitude (tropical vs. temperate) and symbiotic type (actinorhizal vs. rhizobial). Specifically, we expected tropical rhizobial symbioses to display strongly facultative SNF as an explanation of their success in low‐latitude forests. In this study we used 15N isotope dilution field experiments in New York, Oregon, and Hawaii to determine SNF strategies in six N‐fixing tree symbioses. Nitrogen fertilization with +10 and +15 g N m−2 year−1 for 4–5 years alleviated N limitation in all taxa, paving the way to determine SNF strategies. Contrary to our hypothesis, all six of the symbioses we studied sustained SNF even at high N. Robinia pseudoacacia (temperate rhizobial) fixed 91% of its N (%Ndfa) in controls, compared to 64% and 59% in the +10 and +15 g N m−2 year−1 treatments. For Alnus rubra (temperate actinorhizal), %Ndfa was 95%, 70%, and 60%. For the tropical species, %Ndfa was 86%, 80%, and 82% for Gliricidia sepium (rhizobial); 79%, 69%, and 67% for Casuarina equisetifolia (actinorhizal); 91%, 42%, and 67% for Acacia koa (rhizobial); and 60%, 51%, and 19% for Morella faya (actinorhizal). Fertilization with phosphorus did not stimulate tree growth or SNF. These results suggest that the latitudinal abundance distribution of N‐fixing trees is not caused by a shift in SNF strategy. They also help explain the excess N in many forests where N fixers are common.

Unifying biological field observations to detect and compare ocean acidification impacts across marine species and ecosystems: what to monitor and why

Abstract. Approximately one-quarter of the CO2 emitted to the atmosphere annually from human activities is absorbed by the ocean, resulting in a reduction of seawater pH and shifts in seawater carbonate chemistry. This multi-decadal process, termed “anthropogenic ocean acidification” (OA), has been shown to have detrimental impacts on marine ecosystems. Recent years have seen a globally coordinated effort to measure the changes in seawater chemistry caused by OA, with best practices now available for these measurements. In contrast to these substantial advances in observing physicochemical changes due to OA, quantifying their biological consequences remains challenging, especially from in situ observations under real-world conditions. Results from 2 decades of controlled laboratory experiments on OA have given insight into the likely processes and mechanisms by which elevated CO2 levels affect biological process, but the manifestation of these process across a plethora of natural situations has yet to be fully explored. This challenge requires us to identify a set of fundamental biological and ecological indicators that are (i) relevant across all marine ecosystems, (ii) have a strongly demonstrated link to OA, and (iii) have implications for ocean health and the provision of ecosystem services with impacts on local marine management strategies and economies. This paper draws on the understanding of biological impacts provided by the wealth of previous experiments, as well as the findings of recent meta-analyses, to propose five broad classes of biological indicators that, when coupled with environmental observations including carbonate chemistry, would allow the rate and severity of biological change in response to OA to be observed and compared. These broad indicators are applicable to different ecological systems, and the methods for data analysis suggested here would allow researchers to combine biological response data across regional and global scales by correlating rates of biological change with the rate of change in carbonate chemistry parameters. Moreover, a method using laboratory observation to design an optimal observing strategy (frequency and duration) and observe meaningful biological rates of change highlights the factors that need to be considered when applying our proposed observation strategy. This innovative observing methodology allows inclusion of a wide diversity of marine ecosystems in regional and global assessments and has the potential to increase the contribution of OA observations from countries with developing OA science capacity.

Setting the stage: How abrupt climate change, geomorphic thresholds, and drought control flood response in the lower Tennessee River, USA

Extreme floods, with multi-century to millennia recurrence intervals, arise from a combination of antecedent watershed characteristics and unusual or rare atmospheric circulations that occur too infrequently to discern drivers from instrumental records. Few stream gauge records in the United States contain 100 years or more of annual peak flow data, meaning rare extreme floods are underrepresented in the peak flow population. We synthesized approximately 8,000 years of paleoflood hydrologic data from multiple studies and various landforms (floodplains, rock shelters, and caves) conducted in the Tennessee River Valley between Chattanooga, Tennessee, and Florence, Alabama, to examine Holocene flood variability. Extreme floods (>11,000 m3/s) clustered around ∼7,900, 6,000–4,900, and ∼1,000–80 cal yrs BP. More moderate floods occurred between 4,800 and 2,000 cal yrs BP. We compared flood variability in the Tennessee Valley to Holocene paleorecords available in North America. All periods of extreme flooding occurred during large-scale, abrupt climate transitions that lacked a distinct directionality of temperature change (i.e., warm to cool or cool to warm). Our findings indicate that extreme floods clustered in times when (1) warm-season precipitation increased, (2) abrupt increases in precipitation followed episodes of drought, and (3) the rate of change in the hydroclimate regimes was greater than the rate of morphological change in response to increased moisture, thus, exceeded geomorphic thresholds. Internal river basin factors such as drought-induced watershed changes and river morphological changes are key flood drivers that set the stage for flood response to changes in precipitation. Our findings suggest that anticipated changes to drought and precipitation intensity due to modern climate change may increase extreme floods, particularly for urban and regulated rivers not given the space for adjusting to higher precipitation variability.

West Coast vegetation shifts as a response to climate change over the past 130,000 years: geographic patterns and process from pollen data

ABSTRACT We compiled pollen sequences from lake and offshore cores at least 6,000 years old (6 ka) for the Mediterranean and Marine ecoregions of the US West Coast. Principal Component Analysis highlighted vegetation differences in core-tops, the Holocene Thermal Maximum (6 ka) and Last Glacial Maximum (LGM, 19 ka). Core-top and HTM ordination produced clusters that reflected geographic clusters in the Sierra Nevada, and the Pacific Northwest coast. Little change in these clusters between 6-0 ka suggested that vegetation communities in coastal and alpine settings persisted, despite warmer global temperatures. PCA outliers reflect distinct pollen assemblages that often were isolated sites or bordered the Great Basin. During the LGM, greater shrub and herb presence in the Marine ecoregion interior indicated enhanced aridity, while conifer presence in coastal and Southern California indicated moist conditions. Qualitatively, tree taxa from the Last Interglacial (~130–120 ka) showed how vegetation shifted over 6–10 kyr from alder, to oak, then redwood, a successional pattern that began again at the Late Glacial (~15 ka). In future West Coast pollen studies, sampling and chronologic control at centennial resolution will enable further study of more time periods and rates of vegetation change in response to climate.

A retrospective analysis of changes in lymphocyte levels in patients with multiple sclerosis during and after Tecfidera® treatment.

BackgroundThere are currently no best practice recommendations for lymphocyte subset monitoring for patients with multiple sclerosis (pwMS) on disease-modifying therapies including Tecfidera® (dimethyl fumarate, DMF). However, there have been several cases of pwMS on DMF without severe lymphopenia who had high CD4:CD8 T cell ratios and went on to develop progressive multifocal leukoencephalopathy.ObjectiveOur objective was to characterize the changes in immune profile during and after DMF treatment in pwMS.MethodsA retrospective analysis of longitudinal data from 299 pwMS who have been treated with DMF at the Fraser Health Multiple Sclerosis Clinic in British Columbia, Canada. The blood test results were taken from January 1, 2013 to April 1, 2020.ResultsOur results suggest that CD8+ T cells had the highest proportional decrease compared to other lymphocyte subset populations and overall lymphocyte count in response to DMF treatment. CD56+ Natural Killer cells were similarly decreased in response to DMF treatment. CD4:CD8 T cell ratio was the measurement that had the highest rate of change in response to DMF initiation and discontinuation.ConclusionCD8+ T cell count and CD4:CD8 T cell ratio may be a more sensitive measurement of the immune landscape of patients with MS on DMF.

Neural Field Theory of Corticothalamic Attention With Control System Analysis.

Neural field theory is used to analyze attention by extending an existing model of the large-scale activity in the corticothalamic system to incorporate local feedbacks that modulate the gains of neural connectivity as part of the response to incoming stimuli. Treatment of both activity changes and connectivity changes as part of a generalized response enables generalized linear transfer functions of the combined response to be derived. These are then analyzed and interpreted via control theory in terms of stimulus-driven changes in system resonances that were recently shown to implement data filtering and prediction of the inputs. Using simple visual stimuli as a test case, it is shown that the gain response can implement attention by evaluating two main features of the stimuli: the magnitude and the rate of change, by increasing the weight placed on the rate of change in response to sudden changes, while reducing the contribution of stimuli value in tandem. These changes of filter parameters are shown to improve the prediction of the upcoming stimuli based on its recent time course. This outcome is analogous to controller-parameter tuning for performance enhancement in engineering control theory.

Quantifying the System-Level Resilience of Thermal Power Generation to Extreme Temperatures and Water Scarcity

Severe weather events, such as extreme temperatures and water scarcity, can have significant impacts on the operation of critical electrical power infrastructure and, consequently, pose major threats to its resilience. Differently from existing studies that focus on the impact of extreme weather on individual power plants, this article quantifies the resilience of thermal power generation to extreme temperatures and the different levels of water availability from a system-level perspective. This article starts by introducing the fundamental engineering models of thermal power plants’ cooling systems. A system-level quantification methodology is then proposed, which also introduces a multicoordinate resilience-oriented metric that assesses system vulnerability through the concepts of conditional value-at-risk and its rate of change in response to changes in the considered weather conditions. The numerical results obtained using a simplified version of the British transmission system not only demonstrate that the proposed framework is well suited to quantify the system-level resilience of the test system to extreme temperatures and different levels of water availability and scarcity but also highlight the benefits of using the newly defined resilience metric in such studies.

Biosensor for maltose quantification and estimation of maltase activity

The aim of this study was to create a laboratory model of an amperometric microbial biosensor for maltose quantification in the presence and absence of starch and to estimate the use of the model in the study of maltase activity of the culture-receptor. The biosensor for maltose was developed on the basis of a Clark-type oxygen electrode, coupled with a bioreceptor, which contained bacterial cells immobilized on the membrane. The determination of maltose concentration was based on measuring the rate of electrode current change in response to addition of the analyte. The detection limit of the biosensor was 1 µM maltose, a linear interval of standard curve was observed from 14 µM up to 1.9 mM of maltose. The microbial biosensor demonstrated good sensitivity to maltose, 36.02 nА (M·s)-1. Combination of bioreceptors on the basis of fungus and bacterium allowed of using the biosensor for quantification of maltose in the presence of starch. Changes in metabolism of the culture-receptor had an effect on the biosensor response. It indicated that the developed model was a tool of simple construction and easy-to-use in the study of maltase activity of the immobilized culture-receptor.

Improving infants’ stress-induced cortisol regulation through attachment-based intervention: A randomized controlled trial

Attachment-based parenting interventions have shown positive effects on early cortisol regulation, a key biomarker. Evaluations to date have focused on diurnal cortisol production in high-risk infants. It is important to understand whether attachment-based intervention may also improve stress-induced cortisol production in typically developing infants. This randomized controlled trial tested an enhanced model of U.S. Early Head Start (EHS) services that combined home-based EHS with a brief, attachment-based parenting intervention, Attachment and Biobehavioral Catch-up (ABC). The trial included 153 low-income mothers and their infants (M age 12.4 months [SD = 4.1]). Control participants received home-based EHS plus 10 weekly books. Intent-to-treat analyses using multilevel models revealed a significant indirect intervention effect on infants’ rates of cortisol change in response to a series of mild stressors. The intervention increased maternal sensitivity, which in turn improved cortisol regulation, particularly infants’ rates of cortisol recovery. The findings illustrate the efficacy of EHS plus ABC for supporting infants’ stress-induced cortisol regulation and implicate sensitive maternal behavior as the underlying driver of the intervention effect. Findings are discussed in terms of the preventative value of attachment-based parenting interventions that improve both parenting and infants’ physiological regulation.

Xylem diameter changes during osmotic stress, desiccation and freezing inPinus sylvestrisandPopulus tremula

Trees experience low apoplastic water potential frequently in most environments. Low apoplastic water potential increases the risk of embolism formation in xylem conduits and creates dehydration stress for the living cells. We studied the magnitude and rate of xylem diameter change in response to decreasing apoplastic water potential and the role of living parenchyma cells in it to better understand xylem diameter changes in different environmental conditions. We compared responses of control and heat-injured xylem of Pinus sylvestris (L.) and Populus tremula (L.) branches to decreasing apoplastic water potential created by osmotic stress, desiccation and freezing. It was shown that xylem in control branches shrank more in response to decreasing apoplastic water potential in comparison with the samples that were preheated to damage living xylem parenchyma. By manipulating the osmotic pressure of the xylem sap, we observed xylem shrinkage due to decreasing apoplastic water potential even in the absence of water tension within the conduits. These results indicate that decreasing apoplastic water potential led to withdrawal of intracellular water from the xylem parenchyma, causing tissue shrinkage. The amount of xylem shrinkage per decrease in apoplastic water potential was higher during osmotic stress or desiccation compared with freezing. During desiccation, xylem diameter shrinkage involved both dehydration-related shrinkage of xylem parenchyma and water tension-induced shrinkage of conduits, whereas dehydration-related shrinkage of xylem parenchyma was accompanied by swelling of apoplastic ice during freezing. It was also shown that the exchange of water between symplast and apoplast within xylem is clearly faster than previously reported between the phloem and the xylem. Time constant of xylem shrinkage was 40 and 2 times higher during osmotic stress than during freezing stress in P. sylvestris and P. tremula, respectively. Finally, it was concluded that the amount of water stored in the xylem parenchyma is an important reservoir for trees to buffer daily fluctuations in water relations.

Direct and indirect genetic and fine-scale location effects on breeding date in song sparrows.

Quantifying direct and indirect genetic effects of interacting females and males on variation in jointly expressed life-history traits is central to predicting microevolutionary dynamics. However, accurately estimating sex-specific additive genetic variances in such traits remains difficult in wild populations, especially if related individuals inhabit similar fine-scale environments. Breeding date is a key life-history trait that responds to environmental phenology and mediates individual and population responses to environmental change. However, no studies have estimated female (direct) and male (indirect) additive genetic and inbreeding effects on breeding date, and estimated the cross-sex genetic correlation, while simultaneously accounting for fine-scale environmental effects of breeding locations, impeding prediction of microevolutionary dynamics. We fitted animal models to 38years of song sparrow (Melospiza melodia) phenology and pedigree data to estimate sex-specific additive genetic variances in breeding date, and the cross-sex genetic correlation, thereby estimating the total additive genetic variance while simultaneously estimating sex-specific inbreeding depression. We further fitted three forms of spatial animal model to explicitly estimate variance in breeding date attributable to breeding location, overlap among breeding locations and spatial autocorrelation. We thereby quantified fine-scale location variances in breeding date and quantified the degree to which estimating such variances affected the estimated additive genetic variances. The non-spatial animal model estimated nonzero female and male additive genetic variances in breeding date (sex-specific heritabilities: 0·07 and 0·02, respectively) and a strong, positive cross-sex genetic correlation (0·99), creating substantial total additive genetic variance (0·18). Breeding date varied with female, but not male inbreeding coefficient, revealing direct, but not indirect, inbreeding depression. All three spatial animal models estimated small location variance in breeding date, but because relatedness and breeding location were virtually uncorrelated, modelling location variance did not alter the estimated additive genetic variances. Our results show that sex-specific additive genetic effects on breeding date can be strongly positively correlated, which would affect any predicted rates of microevolutionary change in response to sexually antagonistic or congruent selection. Further, we show that inbreeding effects on breeding date can also be sex specific and that genetic effects can exceed phenotypic variation stemming from fine-scale location-based variation within a wild population.

In this issue ofWeather

The first paper this month is Neil Wells’ examination of the effect of the warmth of the North Atlantic Ocean on the climate of northwestern Europe: ‘The North Atlantic Ocean and climate change in the UK and northern Europe’ on p. 3. Although the topic of the moderation of temperature changes in western high latitudes is a favourite for geography students at school, Dr Wells adds much in his article, describing the many factors that keep northwestern Europe warm through the winter. The North Atlantic is a powerful heat pump, exceeding the effects of the North Pacific, despite the larger size of the latter. Continuous measurement in depth has increased our understanding of water flows and the advection of both temperature and salinity within the oceans. We are presented with a record of the changes in these factors over recent years – an area of increasing study in the oceanographic community related to climate and its rate of change in response to anthropogenic forcing. Malcolm Walker's last paper on p. 10 describes the life of researcher and former RMetS President Prof. P. A. Sheppard. Lewis Fry Richardson is well known as the developer of the principle of numerical weather prediction years before the invention of the electronic computer and he tested the proposal by bringing mathematicians together to work in parallel to calculate the future state of the atmosphere. This spurred an image of a ‘forecasting ­factory’, organised along the lines of mass ­production, that might have been developed in order to forecast the weather. Stephen Conlin imagined what this factory might have looked like and his painting is reproduced on the front cover of the journal. In ‘An artist's impression of Richardson's fantastic forecast factory’ on p. 14, Peter Lynch describes this painting in detail in relation to the forecasting process described by Richardson more than 190 years ago. Wednesday 1 July 2015 was the warmest day of last year for much of the UK, but this brought the hazards described by John Turnpenny in his short article ‘Missing the expected in the Cairngorms, 1 July 2015’ on p. 18.

Rapid Prototyping of Inspired Gas Delivery System for Pulmonary MRI Research.

Specific ventilation imaging (SVI) is a noninvasive magnetic resonance imaging (MRI)-based method for determining the regional distribution of inspired air in the lungs, useful for the assessment of pulmonary function in medical research. This technique works by monitoring the rate of magnetic resonance signal change in response to a series of imposed step changes in inspired oxygen concentration. The current SVI technique requires a complex system of tubes, valves, and electronics that are used to supply and rapidly switch inspired gases while subjects are imaged, which makes the technique difficult to translate into the clinical setting. This report discusses the design and implementation of custom three-dimensional (3D) printed hardware that greatly simplifies SVI measurement of lung function. Several hardware prototypes were modeled using computer-aided design software and printed for evaluation. After finalization of the design, the new delivery system was evaluated based on O2 and N2 concentration step responses and validated against the current SVI protocol. The design performed rapid switching of supplied gas within 250 ms and consistently supplied the desired concentration of O2 during operation. It features a reduction in the number of commercial hardware components, from five to one, and a reduction in the number of gas lines between the operator's room and the scanner room, from four to one, as well as a substantially reduced preparation time from 25 to 5 min. 3D printing is well suited to the design of inexpensive custom MRI compatible hardware, making it particularly useful in imaging-based research.

The effect of hydration on the risk of friction blister formation on the heel of the foot

Friction blister research has focused on prevention and treatment approaches rather than exploring the pathophysiology of the friction blister. Increased skin hydration has been purported to be a key risk factor in friction blister development. This study aimed to test the effect of increased skin surface hydration on the risk of friction blister creation. The skin on one foot was hydrated by soaking the foot in water. Intermittent loading was carried out until an observable change of 3°C was evident using infrared thermography. The contra lateral foot acted as a control. Skin hydration and elasticity was measured using electrical capacitance and negative pressure respectively. The rate of temperature change of the hydrated group was significantly greater than that of the non-hydrated foot group (P=0.001) and showed a strong positive correlation (r=0.520) with skin surface hydration. Weak negative correlations were seen between skin elasticity and rate of temperature change in response to load application (r=-0.166) and skin surface hydration and elasticity at baseline (r=-0.195). In controlled experimental conditions increased skin surface hydration increases the rate of temperature change of the skin in response to load application and consequently increases the risk of blister creation.

The effect of adjusting model inputs to achieve mass balance on time-dynamic simulations in a food-web model of Lake Huron

Ecopath with Ecosim (EwE) is a widely used modeling tool in fishery research and management. Ecopath requires a mass-balanced snapshot of a food web at a particular point in time, which Ecosim then uses to simulate changes in biomass over time. Initial inputs to Ecopath, including estimates for biomasses, production to biomass ratios, consumption to biomass ratios, and diets, rarely produce mass balance, and thus ad hoc changes to inputs are required to balance the model. There has been little previous research of whether ad hoc changes to achieve mass balance affect Ecosim simulations. We constructed an EwE model for the offshore community of Lake Huron, and balanced the model using four contrasting but realistic methods. The four balancing methods were based on two contrasting approaches; in the first approach, production of unbalanced groups was increased by increasing either biomass or the production to biomass ratio, while in the second approach, consumption of predators on unbalanced groups was decreased by decreasing either biomass or the consumption to biomass ratio. We compared six simulation scenarios based on three alternative assumptions about the extent to which mortality rates of prey can change in response to changes in predator biomass (i.e., vulnerabilities) under perturbations to either fishing mortality or environmental production. Changes in simulated biomass values over time were used in a principal components analysis to assess the comparative effect of balancing method, vulnerabilities, and perturbation types. Vulnerabilities explained the most variation in biomass, followed by the type of perturbation. Choice of balancing method explained little of the overall variation in biomass. Under scenarios where changes in predator biomass caused large changes in mortality rates of prey (i.e., high vulnerabilities), variation in biomass was greater than when changes in predator biomass caused only small changes in mortality rates of prey (i.e., low vulnerabilities), and was amplified when environmental production was increased. When standardized to mean changes in biomass within each scenario, scenarios when vulnerabilities were low and when fishing mortality was increased explained the most variation in biomass. Our findings suggested that approaches to balancing Ecopath models have relatively little effect on changes in biomass over time, especially when compared to assumptions about how mortality rates of prey change in response to changes in predator biomass. We concluded that when constructing food-web models using EwE, determining the effect of changes in predator biomass on mortality rates of prey should be prioritized over determining the best way to balance the model.

Analysis of Anterior Segment Dynamics Using Anterior Segment Optical Coherence Tomography Before and After Laser Peripheral Iridotomy

To evaluate changes in the speed of pupil constriction and in anterior segment parameters after laser peripheral iridotomy (LPI) in patients with angle closure using anterior segment optical coherence tomography. In this prospective observational study, videos of pupil and anterior segment changes in response to illumination were captured with real-time video recording using anterior segment optical coherence tomography and were analyzed frame by frame before and after LPI. Customized software was used to measure the speed of pupil constriction and changes in anterior chamber depth and anterior chamber area, as well as iris thickness at 750 μm from the scleral spur, at the sphincter muscle region (0.75 mm from the pupillary margin), and at the mid-iris location (half the distance between the scleral spur and the pupillary margin). Pupil diameter, angle opening distance, and trabecular-iris space area at 500 μm from the scleral spur were determined. The speed of pupil constriction was defined as the rate of pupil diameter change in response to illumination. Twenty-nine patients were included. Most were Chinese (26 of 29 [90%]) and female (18 of 29 [62%]). The anterior chamber area, angle opening distance at 500 μm from the scleral spur, and trabecular-iris space area at 500 μm from the scleral spur were significantly higher after LPI (P < .001). A significant increase was observed in the speed of pupil constriction after LPI (P < .005). In response to illumination, the rate of change in iris thickness at the sphincter muscle region and at 750 μm from the scleral spur was faster after LPI (P < .05). Similarly, an increase was observed in the speed of change of angle-opening distance at 500 μm from the scleral spur in response to illumination after LPI (P < .05). In patients with angle closure, changes in dynamic iridopupillary behavior are observed after LPI. The speed of pupillary constriction is faster after LPI.

Hydrological controls on carbon metabolism in wetlands

Governed by a series of non-linear feedback mechanisms among water, vegetation and decomposers, carbon storage within wetlands is important on a global scale. However, the effect that climatic fluctuations have on those mechanisms is not well documented. In this study, we introduce a mechanistic model connecting hydrology, vegetation and microbial biomass to investigate how changes in the climate signal propagate through wetland ecosystems, via vegetation and microbial dynamics, and attempt to quantify how net rates of wetland carbon metabolism change in response to a changing climate. Our particular focus is the dryland–wetland systems found in south-west Western Australia (SWWA), as they are expected to be sensitive to projected climatic changes due to their close linkage to the seasonal water delivery pattern. The model simulations investigate wetland carbon retention under different hydro-climatological conditions ranging across a regional gradient in the dryness index. The results indicate that short term and long term vegetation responses may be counter-intuitive due to adaptability in the water uptake strategy of the vegetation community partially decoupling biomass from water availability. Furthermore, changes in water delivery are not a good indicator for overall changes in wetland metabolism, defined as the net rate of carbon assimilation, due to the dominance of the soil carbon storages and their sensitivity to heightened bacterial metabolism rates with increasing temperatures. The results highlight that an optimum combination of water supply and vegetation leads to a higher percentage of carbon being stored in soils, therefore increasing the resistance of the carbon storage to changes in precipitation. The model presented here provides a first step to explain how changing patterns of rainfall, temperature and evapotranspiration can change carbon cycling characteristics and the carbon retention efficiency of dryland–wetlands.

Pupil dynamics in Chinese subjects with angle closure

To evaluate the speed of pupil constriction (SPC) in response to a standardized change in illumination from dark to light using anterior segment optical coherence tomography (AS-OCT) in eyes with closed angles, compared to those with open angles. This was a prospective, comparative, observational study. Study subjects with primary angle-closure glaucoma (PACG) and/or primary angle-closure (PAC) were recruited along with a group of normal as controls. Videos of iris and anterior segment changes in response to illumination were captured with real-time video recording from AS-OCT and analysed frame by frame, beginning from a dilated to a constricted pupil. Customized software was used to measure speed of iris constriction, anterior chamber depth (ACD), anterior chamber width (ACW), iris thickness, and pupil diameter (PD). SPC was defined as the rate of pupil diameter change in response to illumination. One hundred and sixty three Chinese subjects were recruited in this study. A total of 137 of 163 eligible videos (82.5%) were available for analysis, comprising 87 subjects with closed angles (all had undergone laser peripheral iridotomies before) and 50 with open angles. SPC was less in eyes with closed angles (1.22 mm/sec vs 1.56 mm/sec, p<0.001), after adjusting for age and ACW, and was positively correlated with axial length, ACD, anterior chamber angle status, PD in the dark, and iris thickness in the dark, (all r>0.2, all p<0.05). In multivariate analysis, SPC was independently associated with anterior chamber angle status (closed angle vs open angle) (β=0.276, p=0.016) and PD in dark (β= 0.129, p=0.009), after adjusting for age, ACW, ACD, iris thickness and vertical cup-to-disc ratio. Compared to those with open angles, eyes with closed angles in Chinese subjects have slower speed of pupil constriction in response to dark-light change, even after adjusting for biometric factors associated with angle closure. The results suggest that differences in irido-pupillary dynamics may play a role in the pathogenesis of angle closure.

Assessing the effects of ocean diffusivity and climate sensitivity on the rate of global climate change

ABSTRACTThe range in the projections of future climate warming can be attributed to the inherent uncertainty in the representation of climate model parameters and processes. In this study, we assess the effect of uncertainty in climate sensitivity and ocean heat uptake on the rate of future climate change. We apply a range of values for climate sensitivity and ocean diapycnal diffusivity in an ensemble of simulations using an intermediate-complexity climate model. We further use probability density functions to estimate the likelihood of each model outcome; using this framework, we calculate a range of likely rates of temperature change in response to a given future CO2 emissions scenario. From this analysis, the most probable maximum rate of temperature change lies between 0.3 and 0.5 °C/decade, with a most likely value of 0.36 °C/decade, which is more than twice the observed rate in the late twentieth century. We show that changes in ocean diffusivity have a significant effect on the rate of transient climate change for high values of climate sensitivity, while they have little influence when climate sensitivity is low. The highest rates of warming occur with high values of climate sensitivity and low values of ocean diffusivity. Such high rates of change could adversely affect the adaptive capacity of healthy functional ecosystems.