Добірка наукової літератури з теми "Effet local cumulé"

Abstract The Loess Plateau of China consists of dissected flat tablelands with steep gullies. To evaluate the effect of topography on local circulation and cumulus generation over the Loess Plateau, numerical simulations of atmospheric boundary layer (ABL) development were conducted using a cloud-resolving nonhydrostatic model. Two types of numerical simulation were carried out under two sets of bottom boundary conditions: real terrain and flat terrain. The differences in ABL development and cumulus generation between the flat- and real-terrain conditions are described and the local circulation structures induced by ABL development are illustrated. More cumulus clouds were generated over the real terrain than over the flat terrain. In the real-terrain case, large amounts of cumulus cloud were generated on the windward slopes and on the edge of the tableland, with updrafts caused by thermal generation and a local circulation developing with horizontal and vertical scales of several kilometers. Cumulus clouds clearly developed at the top of the ABL because the water vapor is nonhomogeneously lifted by the local circulation on windward slopes and on edge of the tableland. Thus, the topography of the Loess Plateau plays an important role in cumulus generation.

The aim of this study was to investigate the effect of different oocytes harvesting methods on retrieval and quality of oocyte from ovarian of local cows. The ovaries (n = 600) were collected from 300 non-pregnant cows their ages ranged between (3-10 years old), slaughtered at the abattoir of Babylon province during the period between September 2017 to March 2018. The oocytes were collected by slicing method, puncture method and aspiration of follicle method and classified according to layers of cumulus cells and the homogenous of cytoplasm into three groups , first group : good quality oocytes with more than 3 layers of cumulus cells and homogeneous of cytoplasm, second group : fair quality oocytes with less than 3 layers of cumulus cells and homogeneous of cytoplasm , third group : poor quality oocytes , denuded oocyte from cumulus cells with heterogeneous cytoplasm . The results showed that the total number of oocytes recovered and the number of oocytes recovered per ovary was significantly higher (P<0.05) by using slicing method (1639 and 8.195 ± 1.03 respectively) compared with the Puncture (923 and 4.610 ± 0.86 respectively ) and aspiration of follicle method (776 and 3.880 ± 0.34 respectively). The results of study also indicated that the total number of oocytes recovered , the average number of oocyte per ovary and the percentage of well recovered by slicing method (751,3.750 ± 0.95 and 45.90 % respectively) and puncture technique (399,1.99 ± 0.03 and 43.30 % respectively) were significantly higher ( P<0.05) compared with aspiration of follicle (299 , 1.14 ± 0.01 and 29.60 % respectively). We conclude from this study that slicing method is the appropriate and good method for oocyte recovering with ideal morphological aspect and quality.

Abstract This study examines shallow cumulus cloud fields and their surface shortwave radiative effects using large-eddy simulation (LES) along with observations across multiple days at the Atmospheric Radiation Measurement Southern Great Plains atmospheric observatory. Pronounced differences are found between probability density functions (PDFs) of downwelling surface solar irradiance derived from observations and LES one-dimensional (1D) online radiation calculations. The shape of the observed PDF is bimodal, which is only reproduced by offline three-dimensional (3D) radiative transfer calculations, demonstrating PDF bimodality as a 3D radiative signature of continental shallow cumuli. Local differences between 3D and 1D radiative transfer calculations of downwelling surface solar irradiance are, on average, larger than 150 W m−2 on one afternoon. The differences are substantially reduced when spatially averaged over the LES domain and temporally averaged over the diurnal cycle, but systematic 3D biases ranging from 2 to 8 W m−2 persist across different days. Covariations between the domain-averaged surface irradiance, framed as a surface cloud radiative effect, and the simulated cloud fraction are found to follow a consistent diurnal relationship, often exhibiting hysteresis. In contrast, observations show highly variable behavior. By subsampling the LES domain, it is shown that this is due to the limited sampling density of inherently 3D observations. These findings help to define observational requirements for detecting such relationships, provide valuable insight for evaluating weather and climate models against surface observations as they push to ever higher resolutions, and have important implications for future assessments of solar renewable energy potential.

Abstract The helicopter-borne instrument payload known as the Airborne Cloud Turbulence Observation System (ACTOS) was used to study the entrainment and mixing processes in shallow warm cumulus clouds. The characteristics of the mixing process are determined by the Damköhler number, defined as the ratio of the mixing and a thermodynamic reaction time scale. The definition of the reaction time scale is refined by investigating the relationship between the droplet evaporation time and the phase relaxation time. Following arguments of classical turbulence theory, it is concluded that the description of the mixing process through a single Damköhler number is not sufficient and instead the concept of a transition length scale is introduced. The transition length scale separates the inertial subrange into a range of length scales for which mixing between ambient dry and cloudy air is inhomogeneous, and a range for which the mixing is homogeneous. The new concept is tested on the ACTOS dataset. The effect of entrained subsaturated air on the droplet number size distribution is analyzed using mixing diagrams correlating droplet number concentration and droplet size. The data suggest that homogeneous mixing is more likely to occur in the vicinity of the cloud core, whereas inhomogeneous mixing dominates in more diluted cloud regions. Paluch diagrams are used to support this hypothesis. The observations suggest that homogeneous mixing is favored when the transition length scale exceeds approximately 10 cm. Evidence was found that suggests that under certain conditions mixing can lead to enhanced droplet growth such that the largest droplets are found in the most diluted cloud regions.

Abstract. We investigate the effects of thermal radiation on cloud development in large-eddy simulations (LESs) with the UCLA-LES model. We investigate single convective clouds (driven by a warm bubble) at 50 m horizontal resolution and a large cumulus cloud field at 50 and 100 m horizontal resolutions. We compare the newly developed 3-D Neighboring Column Approximation with the independent column approximation and a simulation without radiation and their respective impact on clouds. Thermal radiation causes strong local cooling at cloud tops accompanied by a modest warming at the cloud bottom and, in the case of the 3-D scheme, also cloud side cooling. 3-D thermal radiation causes systematically larger cooling when averaged over the model domain. In order to investigate the effects of local cooling on the clouds and to separate these local effects from a systematically larger cooling effect in the modeling domain, we apply the radiative transfer solutions in different ways. The direct effect of heating and cooling at the clouds is applied (local thermal radiation) in a first simulation. Furthermore, a horizontal average of the 1-D and 3-D radiation in each layer is used to study the effect of local cloud radiation as opposed to the domain-averaged effect. These averaged radiation simulations exhibit a cooling profile with stronger cooling in the cloudy layers. In a final setup, we replace the radiation simulation by a uniform cooling of 2.6 K day−1. To focus on the radiation effects themselves and to avoid possible feedbacks, we fixed surface fluxes of latent and sensible heat and omitted the formation of rain in our simulations. Local thermal radiation changes cloud circulation in the single cloud simulations, as well as in the shallow cumulus cloud field, by causing stronger updrafts and stronger subsiding shells. In our cumulus cloud field simulation, we find that local radiation enhances the circulation compared to the averaged radiation applications. In addition, we find that thermal radiation triggers the organization of clouds in two different ways. First, local interactive radiation leads to the formation of cell structures; later on, larger clouds develop. Comparing the effects of 3-D and 1-D thermal radiation, we find that organization effects of 3-D local thermal radiation are usually stronger than the 1-D counterpart. Horizontally averaged radiation causes more clouds and deeper clouds than a no radiation simulation but, in general less-organized clouds than in the local radiation simulations. Applying a constant cooling to the simulations leads to a similar development of the cloud field as in the case of averaged radiation, but less water condenses overall in the simulation. Generally, clouds contain more liquid water if radiation is accounted for. Furthermore, thermal radiation enhances turbulence and mixing as well as the size and lifetime of clouds. Local thermal radiation produces larger clouds with longer lifetimes. The cloud fields in the 100 and 50 m resolution simulations develop similarly; however, 3-D local effects are stronger in the 100 m simulations which might indicate a limit of our 3-D radiation parameterization.

SummaryThe oocyte is known from recent studies in the mouse, cow, sheep and human to be a central regulator of follicular cell function. However, in the pig, little information is known about the regulation of cumulus expansion by oocyte-secreted factors and oocyte quality. We investigated the possible effects of oocyte-secreted factors during in vitro maturation on cumulus expansion and on porcine oocytes as judged by subsequent embryonic development after parthenogenetic activation. Cumulus–oocyte complexes (COC) from antral follicles of pig ovaries collected from a local abattoir were divided into control and treatment groups and were cultured in tissue culture medium 199 supplemented with follicle-stimulating hormone. Treatment groups consisted of increasing numbers of denuded oocytes (DO) co-cultured with COC (at ratios of COC to DO of 1:1, 1:2, 1:3, 1:4 and 1:5). After incubation for 44 h, cumulus expansion and maturation rates were assessed and oocytes were activated parthenogenetically. Cumulus expansion in the 1 COC:4 DO and 1 COC:5 DO groups was low and altered because full dispersion of the outer layer did not occur. Cell viability was not affected, as measured by the automated cell counter, but scanning electron microscopy revealed only a scanty extracellular matrix. Blastocyst rate was significantly higher in the 1 COC:4 DO (34.4%) and in the 1 COC:5 DO (34.9%) groups (p < 0.05) when compared with other groups. Maturation rate, cleavage rate and total cell number showed no significant difference between control and treatment groups. Amplification by reverse transcription polymerase chain reaction (RT-PCR) showed up-regulation of growth differentiation factor 9 (GDF9) in the cumulus cells in the 1 COC:4 DO group at 44 h. We conclude that denuded porcine oocytes could improve the maturation of COC as evidenced by increased blastocyst development in the 1 COC:4 DO, even though cumulus expansion was poor. This improvement could be a result of the GDF9 up-regulation.

The Ban minipig is a local breed characterized by small ovaries with a scant number of follicles available for in vitro maturation (IVM). The combination of eCG and hCG has been used successfully to control estrus in pig breeding programs. In this paper we present the first results of IVF in this breed in comparison with 2 types of oocyte preparation: (1) from animals not receiving gonatotropin treatment (group 1, n = 9); and (2) from animals receiving an injection of mixed pregnant mare serum gonadotropin and hCG, 300 IU/animal, for 3 days before oocyte collection (group 2, n = 4). All animals were 1 to 3 years old and with body weights that varied from 8 to 12 kg. At the time of collection, the ovaries were observed for follicle development; the cumulus–oocyte complexes (COCs) were aspirated using a 18-gauge needle. COCs of categories A (with more than 4 layers of cumulus cells) and B (with 2 to 4 layers of cumulus cells) were collected and matured in vitro as described previously (Kikuchi et al. 2002 Biol. Reprod. 66, 1033–1041) at 39�C under 5% CO2 in air. Matured oocytes with expanding cumulus cells were inseminated using male Ban minipig epididymal semen frozen by the methods reported by Kikuchi et al. (1998 Theriogenology 50, 615–623). The frozen–thawed spermatozoa were pre-incubated for 1 h in modified medium-199 adjusted to pH 7.8 in the incubator at 37�C. The capacitated spermatozoa were diluted and added to drops of fertilization medium (Fig-FM; Suzuki et al. 2002 Int. J. Androl. 123, 135–142) containing oocytes; the final concentration of sperm was 106/mL. After 3 h of co-incubation, attached spermatozoa and cumulus cells were removed from oocytes and the oocytes were the cultured in vitro as described previously (Kikuchi et al. 2002). The results obtained from 4 replicates showed that the number of follicles with a diameter larger than 2 mm and the rates of oocytes categorized as A and B were significantly lower (P &lt; 0.05; ANOVA test) in the nontreated animals (0.0 and 67.5%, respectively) than in the treated group (25.5 and 87.1%, respectively). The rates of oocytes with a clearly expanding cumulus obtained after IVM were 78.6 (n = 136) and 88.1% (n = 101) for groups 1 and 2, respectively. The rates of cleaved embryos and embryos developed to the compact morula stage were 47.2 and 9.1% (n = 39), respectively, for group 1; and 89.1 and 18.8% (n = 101), respectively, for group 2. In conclusion, gonadotropin treatment before the collection of oocytes is recommended for application of IVM–IVF to local Ban minipigs. This work was supported by a grant from the VAST-Japan Society for the Promotion of Science Project.

Objectif : La présente étude vise à évaluer et à prioriser le niveau de satisfaction des utilités attendues des cultivars d’igname auprès 1032 acteurs locaux de la filière igname au Sud-ouest des Savanes Sèches au Togo. Méthodologie et résultats: Le brainstorming, le scoring et les avis d’experts, ont permis la définition de quinze descripteurs d’utilités des cultivars, dont les notes d’appréciation ont révélé une corrélation positive significative entre attributs. L’ensemble des attributs a été priorisé en trois classes selon la loi 80/20 (la loi de Pareto). Valeur marchande, nom de cultivar à connotation d’image et gros et longs tubercules ont constitué la principale classe d’attributs avec des notes moyennes d’utilités significatives et respectivement de 9,52 ; 7,28 et 2,28. Ils ont satisfait à 63,91% des utilités cumulées attendues des attributs de tous les cultivars. De tous, le lieu de production à image de qualité (0,80) et la résilience aux divers stresseurs, (0,34) ont été faiblement apprécié. Les effets de l’âge et du sexe des participants sur les notes d’appréciation de l’utilité n‘ont pas été perçus. Conclusion et application des résultats: Les utilités cumulées attendues ont été satisfaites à 63,91% par 20% des attributs en culture d’igname et une faible atteinte d’utilité cumulée de 36,07% par 80% du reste des attributs. De futurs programmes d’amélioration variétale pourront prendre en compte la satisfaction des utilités attendues des ignames. Une piste de production labélisée des tubercules et de leurs transformations élargies aux potentialités de tous les cultivars peuvent constituer une application à envisager sur la base des présents résultats et limiter ainsi l’érosion génétique de la culture d’igname. Mots clés : ignames, attributs, priorisation, utilités attendues, Savanes Sèches, Togo. Gnon et al., J. Appl. Biosci. 2020 Evaluation d’utilités attendues des attributs de cultivars de l’igname : base d’une gestion locale de l’agrobiodiversité de Dioscorea spp au Sud-ouest des Savanes Sèches au Togo (Afrique de l’Ouest) 15765 Evaluation of expected utilities of yam cultivar attributes : a local base for agrobiodiversty management of Dioscorea spp in Southwest Dry Savannahs in Togo (West Africa) ABSTRACT Objectives: The present study aims to evaluate and prioritize the level of satisfaction of the expected utilities of yam cultivars by local actors of the yam sector in the South-West of Dry Savannah in Togo. Methodology and results: The scoring and the expert opinions, allowed the definition of fifteen cultivar attribute descriptors by 1032 actors of the yam sector followed by their prioritization in three distinct classes by the law 80/20. The average utilities of the main attributes: market value, cultivar name with image connotation and large and long tubers were respectively 9.52; 7.28 and 2.28. They represented 63.91% of the expected cumulative utilities of all attributes. The effects of age and sex on expected utility ratings were not seen in this study. Conclusion and application of the findings: 20% of the attributes fulfilled 63.91% of cumulative utilities expected in yam culture and posing the problem of the low cumulative utility of 36.07% by 80% of the attributes. Thus, future research to improve a satisfaction of utilities of the 80% of attributes is necessary. Future varietal improvement programs, may take into account the satisfaction of the expected utilities of yams. A path of labeled production of tubers and their transformations extended to the potential of all cultivars may constitute an application to be considered on the basis of the present results and thus limit the genetic erosion of the yam crop. Keywords: yams, attributes, prioritization, expected utilities, Dry Savannahs, Togo.

The objectives of the current study were to evaluate the effects of supplemental nano-selenium (NSe) and nano-zinc oxide (NZn-O) particles during in vitro maturation (IVM) on DNA damage of cumulus cells, glutathione (GSH) concentration in bovine oocytes, subsequent embryo development and re-expansion rate of vitrified warmed blastocysts. The current study was conducted on bovine ovaries obtained from a local abattoir and transported to the laboratory in sterile phosphate buffer saline with antibiotics at 37°C, within 1 h after slaughter. Ovaries were pooled, regardless of stage of the oestrous cycle of the donor. Only cumulus-intact complexes with evenly granulated cytoplasm were selected for IVM. Experimental design included the following: Experiment 1 studied the effect of addition of 1.0 µg/mL NSe or NZn-O to IVM medium on DNA damage of cumulus cells; Experiment 2 evaluated the effects of NSe or NZn-O on intracellular glutathione in oocytes and cumulus cells; in Experiment 3, the development of oocytes matured in IVM medium supplemented with 1.0 µg/mL NSe or NZn-O was investigated; and in Experiment 4, the effects of adding 1.0 µg/mL NSe and NZn-O to in vitro fertilisation media on vitrified oocytes and embryos were investigated. The DNA damage in cumulus cells decreased with supplemental NSe and NZn-O at concentration of 1 µg/mL in the IVM medium (180.2 ± 21.4, 55.8 ± 4.3 and 56.6 ± 3.9 for the control and NSe and NZn-O groups respectively). Total GSH concentrations increased following supplementation with 1 µg/mL NSe and 1 µg/mL NZn-O, compared with the control group. Re-expansion rate of vitrified warmed blastocysts in experimental media containing NSe and NZn-O with ethylene glycol was higher than that of the control. In conclusion, providing NSe and NZn-O during oocyte maturation significantly increased both intracellular GSH concentration and DNA integrity of cumulus cells. Optimal embryo development was partially dependent on the presence of NSe and NZn-O during IVM. NSe and NZn-O during oocyte maturation act as a good cryoprotective agents of vitrified, warmed blastocysts.

In vitro maturation is the crucial step for in vitro embryo production. It needs a large number of oocytes as source gamet cells recovered. The present study is aimed to assess the influence of corpus luteum on the average number oocytes harvested, COCs quality and subsequent maturation of immature oocytes recovered from sheep ovaries. Sheep ovaries were collected from local slaughterhouse and COCs were collected by using slicing method. Collected COCs were graded into three categories dependent upon cumulus cells surrounding them and the homogenous of cytoplasm. COCs were maturated in maturation media at 5% CO2 for 24 hours. Maturation of oocytes evaluated base on the expansion of cumulus cells and extrusion of the first polar body. There was significantly higher on average of COCs harvested from ovaries with corpus luteum compared without corpus luteum. The presence of Corpus luteum did not affect the COCs quality and ability to reach the maturation stage. However, there was a dramatic effect of cultured COCs quality on maturation rate both groups. Collectively, these results indicate that COCs quality is the main factor affecting the subsequent of oocytes matured in vitro. Keywords: Corpus luteum; cumulus oocyte complex; in vitro maturation; maturation rate; ovaries

La conception de processus robustes revêt une importance capitale dans divers secteurs, tels que le génie chimique et le génie des procédés. La nature de la robustesse consiste à s'assurer qu'un processus peut constamment produire les résultats souhaités pour les décideurs, même lorsqu'ils sont confrontés à une variabilité et à une incertitude intrinsèques. Un processus conçu de manière robuste améliore non seulement la qualité et la fiabilité des produits, mais réduit également de manière significative le risque de défaillances coûteuses, de temps d'arrêt et de rappels de produits. Il améliore l'efficacité et la durabilité en minimisant les déviations et les défaillances du processus. Il existe différentes méthodes pour améliorer la robustesse du système, telles que la conception d'expériences, l'optimisation robuste et la méthodologie de la surface de réponse. Parmi les méthodes de conception robuste, l'analyse de sensibilité pourrait être appliquée comme technique de soutien pour mieux comprendre comment les modifications des paramètres d'entrée affectent les performances et la robustesse. En raison du développement rapide en science de l’ingénieure, les modèles mécanistiques ne captant pas certaines parties des systèmes complexe, peuvent ne pas être l'option la plus appropriée pour d'analyse de sensibilité. Ceci nous amène à envisager l'application de modèles d'apprentissage automatique et la combiner avec l’analyse de sensibilité. Par ailleurs, la question de l'interprétabilité des modèles d'apprentissage automatique a gagné en importance, il est de plus en plus nécessaire de comprendre comment ces modèles parviennent à leurs prédictions ou à leurs décisions et comment les différents paramètres sont liés. Étant donné que leurs performances dépassent constamment celles des modèles mécanistiques, fournir des explications, des justifications et des informations sur les prédictions des modèles de ML permettent non seulement de renforcer leur fiabilité et leur équité, mais aussi de donner aux ingénieurs les moyens de prendre des décisions en connaissance de cause, d'identifier les biais, de détecter les erreurs et d'améliorer les performances globales et la fiabilité des systèmes. Diverses méthodes sont disponibles pour traiter les différents aspects de l'interprétabilité, ces dernières reposent sur des approches spécifiques à un modèle et sur des méthodes agnostiques aux modèles.Dans cette thèse, notre objectif est d'améliorer l'interprétabilité de diverses méthodes de ML tout en maintenant un équilibre entre la précision dans la prédiction et l'interprétabilité afin de garantir aux décideurs que les modèles peuvent être considérés comme robustes. Simultanément, nous voulons démontrer que les décideurs peuvent faire confiance aux prédictions fournies par les modèles ML. Les outils d’interprétabilité ont été testés pour différents scénarios d'application, y compris les modèles basés sur des équations, les modèles hybrides et les modèles basés sur des données. Pour atteindre cet objectif, nous avons appliqué à diverses applications plusieurs méthodes agnostiques aux modèles, telles que partial dependence plots, individual conditional expectations, accumulated local effects, etc
Robust process design holds paramount importance in various industries, such as process and chemical engineering. The nature of robustness lies in ensuring that a process can consistently deliver desired outcomes for decision-makers and/or stakeholders, even when faced with intrinsic variability and uncertainty. A robustly designed process not only enhances product quality and reliability but also significantly reduces the risk of costly failures, downtime, and product recalls. It enhances efficiency and sustainability by minimizing process deviations and failures. There are different methods to approach the robustness of a complex system, such as the design of experiments, robust optimization, and response surface methodology. Among the robust design methods, sensitivity analysis could be applied as a supportive technique to gain insights into how changes in input parameters affect performance and robustness. Due to the rapid development and advancement of engineering science, the use of physical models for sensitivity analysis presents several challenges, such as unsatisfied assumptions and computation time. These problems lead us to consider applying machine learning (ML) models to complex processes. Although, the issue of interpretability in ML has gained increasing importance, there is a growing need to understand how these models arrive at their predictions or decisions and how different parameters are related. As their performance consistently surpasses that of other models, such as knowledge-based models, the provision of explanations, justifications, and insights into the workings of ML models not only enhances their trustworthiness and fairness but also empowers stakeholders to make informed decisions, identify biases, detect errors, and improve the overall performance and reliability of the process. Various methods are available to address interpretability, including model-specific and model-agnostic methods. In this thesis, our objective is to enhance the interpretability of various ML methods while maintaining a balance between accuracy and interpretability to ensure decision-makers or stakeholders that our model or process could be considered robust. Simultaneously, we aim to demonstrate that users can trust ML model predictions guaranteed by model-agnostic techniques, which work across various scenarios, including equation-based, hybrid, and data-driven models. To achieve this goal, we applied several model-agnostic methods, such as partial dependence plots, individual conditional expectations, accumulated local effects, etc., to diverse applications

One of the great challenges in predicting the rate and geographical pattern of climate change is to faithfully represent the feedback effects of various cloud types that arise via different mechanisms in different parts of the atmosphere. Cirrus clouds are a particularly uncertain component of general circulation model (GCM) simulations of long-term climate change for a variety of reasons, as detailed below. First, cirrus encompass a wide range of optical thicknesses and altitudes. At one extreme are the thin tropopause cirrus that barely affect the short-wave albedo while radiating to space at very cold temperatures, producing a net positive effect on the planetary radiation balance and causing local upper troposphere warming, thus stabilizing the lapse rate. At the other extreme are thick cumulus anvil cirrus whose bases descend to the freezing level; these clouds produce significant but opposing short-wave and long-wave effects on the planetary energy balance while cooling the surface via their reflection of sunlight. In fact, satellite climatologies show a continuum of optical thicknesses between these two extremes (Rossow and Schiffer 1991). In a climate change, the net effect of cirrus might either be a positive or a negative feedback, depending on the sign and magnitude of the cloud cover change in each cloud-type category and the direction and extent of changes in their optical properties (see Stephens et al. 1990). Second, the dynamic processes that create cirrus are poorly resolved and different in different parts of the globe. In the tropics, small-scale convective transport of water from the planetary boundary layer to the upper troposphere is the immediate source of a significant fraction of the condensate in mesoscale cirrus anvils (see Gamache and Houze 1983), and ultimately the source of much of the water vapor that condenses out in large-scale uplift to form thinner cirrus. However, many observed thin cirrus cannot directly be identified with a convective source, suggesting that in situ upper troposphere dynamics and regeneration processes within cirrus (see Starr and Cox 1985) are important. In mid-latitudes, although summertime continental convection is a source of cirrus, in general cirrus is associated with mesoscale frontal circulations in synoptic-scale baroclinic waves and jet streaks (see Starr and Wylie 1990; Mace et al. 1995).