Distribution by Scientific Domains

Kinds of Criterion

  • alternative criterion
  • appropriate criterion
  • bayesian information criterion
  • convergence criterion
  • coulomb criterion
  • design criterion
  • deviance information criterion
  • diagnostic criterion
  • energy criterion
  • error criterion
  • evaluation criterion
  • exclusion criterion
  • failure criterion
  • griffith criterion
  • important criterion
  • inclusion criterion
  • information criterion
  • key criterion
  • least-square criterion
  • main criterion
  • new criterion
  • one criterion
  • optimality criterion
  • performance criterion
  • proposed criterion
  • response criterion
  • selection criterion
  • simple criterion
  • single criterion
  • stability criterion
  • stopping criterion
  • stress criterion
  • useful criterion
  • yield criterion

  • Terms modified by Criterion

  • criterion b
  • criterion c
  • criterion measure
  • criterion standard
  • criterion validity
  • criterion value

  • Selected Abstracts


    ADDICTION, Issue 3 2009
    No abstract is available for this article. [source]


    Yeong-Jeu Sun
    ABSTRACT In this paper, the instability for a class of singular systems with discrete and distributed time delays is investigated. Simple instability criterion, which is a delay-dependent criterion, is derived to guarantee the instability of such systems. Finally, a numerical example is given to illustrate the use of the main result. [source]

    Thermally Conducting Partially Ionized Plasma in a Variable Magnetic Field

    S. Shaikh
    Abstract An infinitely extending homogenous partially ionized plasma endowed with several physical mechanisms and permeated by a variable magnetic field is considered. The combined effect of these parameters, namely, Hall currents, finite conductivity, ion viscosity, collision with neutrals and thermal conductivity on the gravitational instability of the plasma is studied. It is found that the several mechanisms play different physical roles in the perturbed problem. Jeans' Criterion is analyzed in the framework of Tsallis' statistics for possible modifications due to the presence of nonextensive effects. A simple generalization of the Jeans' criterion is obtained and the standard values are obtained in the limiting case q = 1, q being the nonextensive parameter. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Recruitment of burbot (Lota lota L.) in Lake Erie: an empirical modelling approach

    M. A. Stapanian
    Stapanian MA, Witzel LD, Cook A. Recruitment of burbot (Lota lota L.) in Lake Erie: an empirical modelling approach. Ecology of Freshwater Fish 2010: 19: 326,337. Published 2010. This article is a US Government work and is in the public domain in the USA Abstract,,, World-wide, many burbot Lota lota (L.) populations have been extirpated or are otherwise in need of conservation measures. By contrast, burbot made a dramatic recovery in Lake Erie during 1993,2001 but declined during 2002,2007, due in part to a sharp decrease in recruitment. We used Akaike's Information Criterion to evaluate 129 linear regression models that included all combinations of one to seven ecological indices as predictors of burbot recruitment. Two models were substantially supported by the data: (i) the number of days in which water temperatures were within optimal ranges for burbot spawning and development combined with biomass of yearling and older (YAO) yellow perch Perca flavescens (Mitchill); and (ii) biomass of YAO yellow perch. Warmer winter water temperatures and increases in yellow perch biomass were associated with decreases in burbot recruitment. Continued warm winter water temperatures could result in declines in burbot recruitment, particularly in the southern part of the species' range. [source]

    The Malleability of Undiscounted Utilitarianism as a Criterion of Intergenerational Justice

    ECONOMICA, Issue 279 2003
    Geir B. Asheim
    Discounting future utilities is often justified by the ethically motivated objective of protecting earlier generations from the excessive saving that seems to be implied by undiscounted utilitarianism in productive economies. We question this justification of discounting by showing that undiscounted utilitarianism has sufficient malleability within important classes of technologies: any efficient and non-decreasing allocation can be the unique optimum according to an undiscounted utilitarian criterion for some choice of utility function. [source]

    Small-variation linear model of the three-phase double-fed induction motor under synchronous operation: stability

    D. Pereira Gonzaga
    Abstract The double-fed induction motor (DFIM) is analysed in this paper with regard to stability. Firstly, its characteristic equation is obtained by means of a linear model for small variations, with the stator resistance equal to zero. The range of speeds for which the DFIM/Load system presents stable synchronous operation is obtained by applying the Routh,Hurwitz Criterion to the characteristic equation. Secondly, by employing the equation for the steady-state electromagnetic torque, with a non-zero stator resistance, another range of speeds giving stable synchronous operation is obtained, and confirmed by some experimental results. In order to confirm the stability, some results of the DFIM/Load system simulation and the characteristic equation root-locus are also presented. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Sex differences in genetic and environmental determinants of pulse pressure

    Katrina J. Scurrah
    Abstract Pulse pressure (PP) is an independent risk factor for cardiovascular disease. PP rises with age, more so in women. We examined sex differences in the correlations and variance components of PP in adult subjects from 767 nuclear families, enriched with those containing twins, from the Victorian Family Heart Study. After adjusting for age, we found no significant differences in the means or variances of PP in males and females. Under the assumption of no sex differences, the proportions of variance due to shared genes, shared environment, and individual-specific environment were 20%, 23% and 57%, respectively. However, same-sex relative pairs had significantly higher correlations than opposite-sex pairs (P=0.005), implying the existence of sex-dependent effects. Extensions to the simple variance components model suggested three possible explanations for these differences: smaller genetic correlation between opposite-sex pairs (,G,MF=0.45, P=0.007); smaller environmental correlation between opposite-sex pairs (P=0.0003); or different environmental and genetic correlations obtained by estimating genetic, environmental, and individual variance components separately for males and females (not nested, Akaike's Information Criterion (AIC) smaller by 6.69). Under the last model, the genetic component of PP variance is greater for males (1.62 vs 0.33) while the environmental component is greater for females (1.84 vs 0), which would have implications for the planning of gene discovery studies, since heritability would be higher in males. However, the second (environmental) approach best fits the data according to the AIC. Genetic explanations for sex differences in phenotypic correlations may be misleading unless shared environmental factors are also considered. PP illustrates a phenotype in which sex dependency represents an important component of phenotypic determination that can be revealed by detailed variance components modelling. Genet. Epidemiol. 2006. © 2006 Wiley-Liss, Inc. [source]

    Bayesian inference in a piecewise Weibull proportional hazards model with unknown change points

    J. Casellas
    Summary The main difference between parametric and non-parametric survival analyses relies on model flexibility. Parametric models have been suggested as preferable because of their lower programming needs although they generally suffer from a reduced flexibility to fit field data. In this sense, parametric survival functions can be redefined as piecewise survival functions whose slopes change at given points. It substantially increases the flexibility of the parametric survival model. Unfortunately, we lack accurate methods to establish a required number of change points and their position within the time space. In this study, a Weibull survival model with a piecewise baseline hazard function was developed, with change points included as unknown parameters in the model. Concretely, a Weibull log-normal animal frailty model was assumed, and it was solved with a Bayesian approach. The required fully conditional posterior distributions were derived. During the sampling process, all the parameters in the model were updated using a Metropolis,Hastings step, with the exception of the genetic variance that was updated with a standard Gibbs sampler. This methodology was tested with simulated data sets, each one analysed through several models with different number of change points. The models were compared with the Deviance Information Criterion, with appealing results. Simulation results showed that the estimated marginal posterior distributions covered well and placed high density to the true parameter values used in the simulation data. Moreover, results showed that the piecewise baseline hazard function could appropriately fit survival data, as well as other smooth distributions, with a reduced number of change points. [source]

    Incorporating movement into models of grey seal population dynamics

    Summary 1One of the most difficult problems in developing spatially explicit models of population dynamics is the validation and parameterization of the movement process. We show how movement models derived from capture,recapture analysis can be improved by incorporating them into a spatially explicit metapopulation model that is fitted to a time series of abundance data. 2We applied multisite capture,recapture analysis techniques to photo-identification data collected from female grey seals at the four main breeding colonies in the North Sea between 1999 and 2001. The best-fitting movement models were then incorporated into state-space metapopulation models that explicitly accounted for demographic and observational stochasticity. 3These metapopulation models were fitted to a 20-year time series of pup production data for each colony using a Bayesian approach. The best-fitting model, based on the Akaike Information Criterion (AIC), had only a single movement parameter, whose confidence interval was 82% less than that obtained from the capture,recapture study, but there was some support for a model that included an effect of distance between colonies. 4The state-space modelling provided improved estimates of other demographic parameters. 5The incorporation of movement, and the way in which it was modelled, affected both local and regional dynamics. These differences were most evident as colonies approached their carrying capacities, suggesting that our ability to discriminate between models should improve as the length of the grey seal time series increases. [source]

    A model for the species,area,habitat relationship

    K. A. Triantis
    Abstract Aim, To propose a model (the choros model) for species diversity, which embodies number of species, area and habitat diversity and mathematically unifies area per se and habitat hypotheses. Location, Species richness patterns from a broad scale of insular biotas, both from island and mainland ecosystems are analysed. Methods, Twenty-two different data sets from seventeen studies were examined in this work. The r2 values and the Akaike's Information Criterion (AIC) were used in order to compare the quality of fit of the choros model with the Arrhenius species,area model. The classic method of log-log transformation was applied. Results, In twenty of the twenty-two cases studied, the proposed model gave a better fit than the classic species,area model. The values of z parameter derived from choros model are generally lower than those derived from the classic species,area equation. Main conclusions, The choros model can express the effects of area and habitat diversity on species richness, unifying area per se and the habitat hypothesis, which as many authors have noticed are not mutually exclusive but mutually supplementary. The use of habitat diversity depends on the specific determination of the ,habitat' term, which has to be defined based on the natural history of the taxon studied. Although the values of the z parameter are reduced, they maintain their biological significance as described by many authors in the last decades. The proposed model can also be considered as a stepping-stone in our understanding of the small island effect. [source]

    Assessment of Complete Isthmus Block After Ablation of Typical Atrial Flutter: Can We Rely on a Single Criterion?


    Extreme College Drinking and Alcohol-Related Injury Risk

    ALCOHOLISM, Issue 9 2009
    Marlon P. Mundt
    Background:, Despite the enormous burden of alcohol-related injuries, the direct connection between college drinking and physical injury has not been well understood. The goal of this study was to assess the connection between alcohol consumption levels and college alcohol-related injury risk. Methods:, A total of 12,900 college students seeking routine care in 5 college health clinics completed a general Health Screening Survey. Of these, 2,090 students exceeded at-risk alcohol use levels and participated in a face-to-face interview to determine eligibility for a brief alcohol intervention trial. The eligibility interview assessed past 28-day alcohol use and alcohol-related injuries in the past 6 months. Risk of alcohol-related injury was compared across daily drinking quantities and frequencies. Logistic regression analysis and the Bayesian Information Criterion were applied to compute the odds of alcohol-related injury based on daily drinking totals after adjusting for age, race, site, body weight, and sensation seeking. Results:, Male college students in the study were 19% more likely (95% CI: 1.12,1.26) to suffer an alcohol-related injury with each additional day of consuming 8 or more drinks. Injury risks among males increased marginally with each day of consuming 5 to 7 drinks (odds ratio = 1.03, 95% CI: 0.94,1.13). Female participants were 10% more likely (95% CI: 1.04,1.16) to suffer an alcohol-related injury with each additional day of drinking 5 or more drinks. Males (OR = 1.69, 95% CI: 1.14,2.50) and females (OR = 1.81, 95% CI: 1.27,2.57) with higher sensation-seeking scores were more likely to suffer alcohol-related injuries. Conclusions:, College health clinics may want to focus limited alcohol injury prevention resources on students who frequently engage in extreme drinking, defined in this study as 8+M/5+F drinks per day, and score high on sensation-seeking disposition. [source]

    Criterion for the Avoidance of Edge Cracking in Layered Systems

    M. Y. He
    When fabricating multilayers with brittle constituents, a prevalent design strategy is to choose fabrication conditions and thermal expansion coefficients that impose in-plane compression on the brittle layers. In such designs, a small zone of out-of-plane tension is induced at the edges that can cause cracks to form and extend, especially along the midplane. The associated stresses and energy release rates have been analyzed, revealing a fail-safe criterion, attributed to the existence of a maximum possible energy release rate, Gmax. Equating this maximum to the toughness defines a fail-safe parameter expressing the influence of the layer thickness, the misfit stress, and the toughness. When fail-safe designs cannot be realized, thin interlayers can be interposed in a manner that diminishes Gmax, broadening accessibility. The roles of misfit stress and interlayer thickness in attaining this condition are derived. [source]

    Fractional Bayesian Lag Length Inference in Multivariate Autoregressive Processes

    Mattias Villani
    The posterior distribution of the number of lags in a multivariate autoregression is derived under an improper prior for the model parameters. The fractional Bayes approach is used to handle the indeterminacy in the model selection caused by the improper prior. An asymptotic equivalence between the fractional approach and the Schwarz Bayesian Criterion (SBC) is proved. Several priors and three loss functions are entertained in a simulation study which focuses on the choice of lag length. The fractional Bayes approach performs very well compared to the three most widely used information criteria, and it seems to be reasonably robust to changes in the prior distribution for the lag length, especially under the zero-one loss. [source]

    Reformulating PTSD for DSM-V: Life after Criterion A

    Chris R. Brewin
    The diagnosis of posttraumatic stress disorder has been criticized on numerous grounds, but principally for three reasons (a) the alleged pathologizing of normal events, (b) the inadequacy of Criterion A, and (c) symptom overlap with other disorders. The authors review these problems along with arguments why the diagnosis is nevertheless worth retaining in an amended form. A proposal for the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) is put forward that involves abolishing Criterion A, narrowing the B criteria to focus on the core phenomena of flashbacks and nightmares, and narrowing the C and D criteria to reduce overlap with other disorders. The potential advantages and disadvantages of this formulation are discussed. [source]

    Effects of repeated burning on species richness in a Florida pine savanna: A test of the intermediate disturbance hypothesis

    Brian Beckage
    Wunderlin (1982) except for Aristida beyrichiana; which follows Peet (1993). Vouchers for each species were collected and deposited at the University of Central Florida herbarium Abstract. We studied the effect of burning frequency on the density and species richness of understory flowering stems in a Florida sandhill. Flowering stems were censused weekly for 54 weeks in six sites that had been burned one to six times in the previous 16 years. We concurrently measured overstory characteristics such as species composition, density and basal area. We used maximum likelihood and Akaike's Information Criterion to compare linear, quadratic, saturating, and null models of community response to repeating burning. We did not find a relationship between species richness, diversity or flowering stem density and fire frequency. Tree density was related to fire frequency and may represent an indirect pathway for fire effects on understory characteristics. While we found no support for the Intermediate Disturbance Hypothesis, an analysis of our experimental design indicated that we had low statistical power. We develop the hypothesis that a saturating model of response to fire best describes understory species richness in our system. We test this hypothesis using the most extensive published fire data set we are aware of and find support for a saturating model. [source]

    On Lindemann's Melting Criterion

    H.-J. Hoffmann
    Schmelzen; Schmelztemperatur; Schmelzkriterium; Lindemann-Kriterium Abstract Lindemann's empirical melting criterion is applied using data of the solid chemical elements. The respective expression which depends on the melting temperature, the molar mass and the molar volume correlates fairly well with the Debye temperatures. However, it seems incapable to predict inversely the melting temperatures with the other parameters given. Thus, Lindemann's criterion has no empirical relevance in addition to its scientific deficits. Über das Schmelzkriterium von Lindemann Das empirische Schmelzkriterium nach Lindemann wird an Hand von Daten der festen chemischen Elemente geprüft. Der betreffende Ausdruck, der von Schmelztemperatur, Molmasse und Molvolumen abhängt, korreliert recht gut mit der Debye-Temperatur. Es gelingt jedoch nicht mit befriedigender Genauigkeit, die Schmelztemperaturen aus der Umkehrung dieses Ausdrucks bei gegebenen anderen Parametern vorherzusagen. Neben den anderen bekannten Mängeln hat das Lindemann-Kriterium somit auch keine empirische Vorhersagekraft. [source]

    Toward a cure for type 1 diabetes mellitus: diabetes-suppressive dendritic cells and beyond

    PEDIATRIC DIABETES, Issue 3pt2 2008
    Nick Giannoukakis
    Abstract:, Insulin has been the gold standard therapy for diabetes since its discovery and commercial availability. It remains the only pharmacologic therapy for type 1 diabetes (T1D), an autoimmune disease in which autoreactive T cells specifically kill the insulin-producing beta cells. Nevertheless, not even molecularly produced insulin administered four or five times per day can provide a physiologic regulation able to prevent the complications that account for the morbidity and mortality of diabetic patients. Also, insulin does not eliminate the T1D hallmark: beta-cell-specific autoimmunity. In other words, insulin is not a ,cure'. A successful cure must meet the following criteria: (i) it must either replace or maintain the functional integrity of the natural, insulin-producing tissue, the endocrine islets of Langerhans' and, more specifically, the insulin-producing beta cells; (ii) it must, at least, control the autoimmunity or eliminate it altogether; and (iii) it must be easy to apply to a large number of patients. Criterion 1 has been partially realized by allogeneic islet transplantation. Criterion 2 has been partially realized using monoclonal antibodies specific for T-cell surface proteins. Criterion 3 has yet to be realized, given that most of the novel therapies are currently quasi-patient-specific. Herein, we outline the current status of non-insulin-based therapies for T1D, with a focus on cell-based immunomodulation which we propose can achieve all three criteria illustrated above. [source]

    Can Justice be a Criterion for Bible Translation?

    Helga Kuhlmann
    First page of article [source]

    Examining the extinction risk of specialized folivores: a comparative study of Colobine monkeys

    Jason M. Kamilar
    Abstract Species extinctions are nonrandom with some taxa appearing to possess traits that increase their extinction risk. In this study, eight predictors of extinction risk were used as independent variables to predict the IUCN category of a subfamily of specialized folivorous primates, the Colobinae. All data were transformed into phylogenetically independent contrasts and were analyzed using bivariate regressions, multiple regression, and a maximum likelihood approach using Akaike's Information Criterion to assess model performance. Once an outlier was removed from the data set, species that devote a smaller proportion of their diet to mature leaf consumption appear to be at a greater risk of extinction. Also, as female body mass increases, so does extinction risk. In contrast, as maximum latitude and the number of habitat types increase, extinction risk appears to decrease. These findings emphasize the importance of examining detailed dietary variation for predicting extinction risk at a relatively fine taxonomic scale and, consequently, may help improve conservation management. Am. J. Primatol. 70:816,827, 2008. © 2008 Wiley-Liss, Inc. [source]

    Donor-Estimated GFR as an Appropriate Criterion for Allocation of ECD Kidneys into Single or Dual Kidney Transplantation

    R. Snanoudj
    It has been suggested that dual kidney transplantation (DKT) improves outcomes for expanded criteria donor (ECD) kidneys. However, no criteria for allocation to single or dual transplantation have been assessed prospectively. The strategy of DKT remains underused and potentially eligible kidneys are frequently discarded. We prospectively compared 81 DKT and 70 single kidney transplant (SKT) receiving grafts from ECD donors aged >65 years, allocated according to donor estimated glomerular filtration rate (eGFR): DKT if eGFR between 30 and 60 mL/min, SKT if eGFR greater than 60 mL/min. Patient and graft survival were similar in the two groups. In the DKT group, 13/81 patients lost one of their two kidneys due to hemorrhage, arterial or venous thrombosis. Mean eGFR at month 12 was similar in the DKT and SKT groups (47.8 mL/min and 46.4 mL/min, respectively). Simulated allocation of kidneys according to criteria based on day 0 donor parameters such as those described by Remuzzi et al., Andres et al. and UNOS, did not indicate an improvement in 12-month eGFR compared to our allocation based on donor eGFR. [source]

    Forecasting Models of Emergency Department Crowding

    Lisa M. Schweigler MD
    Abstract Objectives:, The authors investigated whether models using time series methods can generate accurate short-term forecasts of emergency department (ED) bed occupancy, using traditional historical averages models as comparison. Methods:, From July 2005 through June 2006, retrospective hourly ED bed occupancy values were collected from three tertiary care hospitals. Three models of ED bed occupancy were developed for each site: 1) hourly historical average, 2) seasonal autoregressive integrated moving average (ARIMA), and 3) sinusoidal with an autoregression (AR)-structured error term. Goodness of fits were compared using log likelihood and Akaike's Information Criterion (AIC). The accuracies of 4- and 12-hour forecasts were evaluated by comparing model forecasts to actual observed bed occupancy with root mean square (RMS) error. Sensitivity of prediction errors to model training time was evaluated, as well. Results:, The seasonal ARIMA outperformed the historical average in complexity adjusted goodness of fit (AIC). Both AR-based models had significantly better forecast accuracy for the 4- and the 12-hour forecasts of ED bed occupancy (analysis of variance [ANOVA] p < 0.01), compared to the historical average. The AR-based models did not differ significantly from each other in their performance. Model prediction errors did not show appreciable sensitivity to model training times greater than 7 days. Conclusions:, Both a sinusoidal model with AR-structured error term and a seasonal ARIMA model were found to robustly forecast ED bed occupancy 4 and 12 hours in advance at three different EDs, without needing data input beyond bed occupancy in the preceding hours. [source]

    A New Delay-Dependent Stability Criterion For Neutral Delay-Differential Systems

    Bin Yang
    ABSTRACT This paper investigates the problem of asymptotic stability for neutral delay-differential systems. Using the Lyapunov method, we derive a new delay-dependent sufficient condition for the stability of systems in terms of the linear matrix inequality (LMI). Numerical examples show that the results obtained in this paper significantly improve the estimate of stability limit over some existing results reported previously in the literature. [source]

    Is ,Best Proven' A Useless Criterion?

    BIOETHICS, Issue 4 2001
    Florencia Luna
    In this article I examine some proposals for modification of ethical documents regulating research, particularly, the problems that introducing certain economic clauses may pose. I evaluate suggestions that reject the notion of providing the ,best proven diagnostic and therapeutic method' in favor of ,the highest attainable therapeutic method' or ,the proven effective prophylactic, diagnostic and therapeutic methods'. I analyze the plausibility and problems of introducing a double standard and the consequences it may have in developing countries. Finally I highlight the impact these changes may imply for these countries. [source]

    Response Adaptive Designs with a Variance-penalized Criterion

    Yanqing Yi
    Abstract We consider a response adaptive design of clinical trials with a variance-penalized criterion. It is shown that this criterion evaluates the performance of a response adaptive design based on both the number of patients assigned to the better treatment and the power of the statistical test. A new proportion of treatment allocation is proposed and the doubly biased coin procedure is used to target the proposed proportion. Under reasonable assumptions, the proposed design is demonstrated to generate an asymptotic variance of allocation proportions, which is smaller than that of the drop-the-loser design. Simulation comparisons of the proposed design with some existing designs are presented. [source]

    Variable Selection for Logistic Regression Using a Prediction-Focused Information Criterion

    BIOMETRICS, Issue 4 2006
    Gerda Claeskens
    Summary In biostatistical practice, it is common to use information criteria as a guide for model selection. We propose new versions of the focused information criterion (FIC) for variable selection in logistic regression. The FIC gives, depending on the quantity to be estimated, possibly different sets of selected variables. The standard version of the FIC measures the mean squared error of the estimator of the quantity of interest in the selected model. In this article, we propose more general versions of the FIC, allowing other risk measures such as the one based on Lp error. When prediction of an event is important, as is often the case in medical applications, we construct an FIC using the error rate as a natural risk measure. The advantages of using an information criterion which depends on both the quantity of interest and the selected risk measure are illustrated by means of a simulation study and application to a study on diabetic retinopathy. [source]

    Akaike's Information Criterion in Generalized Estimating Equations

    BIOMETRICS, Issue 1 2001
    Wei Pan
    Summary. Correlated response data are common in biomedical studies. Regression analysis based on the generalized estimating equations (GEE) is an increasingly important method for such data. However, there seem to be few model-selection criteria available in GEE. The well-known Akaike Information Criterion (AIC) cannot be directly applied since AIC is based on maximum likelihood estimation while GEE is nonlikelihood based. We propose a modification to AIC, where the likelihood is replaced by the quasi-likelihood and a proper adjustment is made for the penalty term. Its performance is investigated through simulation studies. For illustration, the method is applied to a real data set. [source]

    Karst Collapse Mechanism and Criterion for Its Stability

    HE Keqiang
    Abstract Karst collapse, caused by natural or artificial abstraction of groundwater, has been a focus of environmental geological problems for its ever-increasing hazardousness. The potential erosion theory and vacuum suction erosion theory, which reveal the origin of karst collapse macroscopically, are popularly accepted. However, a mathematic prediction criterion for karst collapse cannot be established only by these two theories. From a new perspective, this paper attempts to explain the microcosmic mechanism of karst collapse on the basis of these two theories. When the shear stress surpasses the shear strength of soil, a certain point or a certain plane in the unconsolidated soil covering karst caves will fail under the mechanical effects of water and air as well as its load-pressure, and with the increase of damaged points, a breaking plane appears and the soil on karst caves is completely damaged; as a result, the karst ground collapses. On the basis of the Mohr-Coulomb failure theory and previous studies, the paper presents a prediction criterion of karst collapse. Finally, by taking, for example, nine typical cases of collapse caused by pumping tests in Guizhou, the paper gives the calculation process of the model and proves its reliability. [source]

    Hyperprolactinaemia in 271 women: up to three decades of clinical follow-up

    Katarina Berinder
    Summary Objective, To characterize women with hyperprolactinaemia at diagnosis and to assess the effect of treatment after long duration of the disease. Design, Retrospective chart review. Patients and measurements, Two hundred and seventy-one women with hyperprolactinaemia at the Karolinska University Hospital, Stockholm, Sweden between 1974 and 2002 were evaluated retrospectively. Criterion for inclusion was elevated S-PRL (, 20 µg/l) found on at least two occasions. Secondary hyperprolactinaemia was excluded. The patients were followed for a median time period of 111 (6,348) months. Two hundred and forty patients were treated with dopamine agonists, 17 underwent surgery, seven received radiotherapy and seven were followed without treatment. Results, Mean age at diagnosis was 31 (± 9·5) years and median PRL level was 72 (25,3500) µg/l. Menstrual disturbances were present in 87% of the women of reproductive age and 47% had galactorrhoea. Microadenomas were found in 63%, macroadenomas in 8% and idiopathic hyperprolactinaemia in 29%. Patients with menstrual disturbances had higher PRL levels than women with normal menstrual function (P < 0·001). We found no differences in PRL levels between patients with or without galactorrhoea (P = 0·578). At the end of clinical follow-up, menstrual cycle was normalized in 94% and galactorrhoea disappeared in 94%. In the medically treated patients, median PRL levels decreased from 70 (25,3100) to 13 (0,89) µg/l, (P < 0·0001). Normalization of PRL level was achieved in 71% of the patients and 80% showed a total or partial degree of tumour shrinkage. In the surgically treated patients, 53% had normal PRL levels without medication at follow-up. Conclusion, Medical treatment was effective in correcting hypogonadism, normalizing PRL levels and reducing tumour size in the majority of the patients after short-term treatment and also in the long run. However, the possibility of transsphenoidal surgery in specific cases must be considered. [source]


    Dimitris Vrakas
    One of the most promising trends in Domain-Independent AI Planning, nowadays, is state-space heuristic planning. The planners of this category construct general but efficient heuristic functions, which are used as a guide to traverse the state space either in a forward or in a backward direction. Although specific problems may favor one or the other direction, there is no clear evidence why any of them should be generally preferred. This paper presents Hybrid-AcE, a domain-independent planning system that combines search in both directions utilizing a complex criterion that monitors the progress of the search, to switch between them. Hybrid AcE embodies two powerful domain-independent heuristic functions extending one of the AcE planning systems. Moreover, the system is equipped with a fact-ordering technique and two methods for problem simplification that limit the search space and guide the algorithm to the most promising states. The bi-directional system has been tested on a variety of problems adopted from the AIPS planning competitions with quite promising results. [source]