Normality

Distribution by Scientific Domains

Kinds of Normality

  • asymptotic normality
  • multivariate normality

  • Terms modified by Normality

  • normality assumption

  • Selected Abstracts


    Pain, Normality, and the Struggle for Congruence: Reinterpreting Residential Care for Children and Youth

    FAMILY RELATIONS, Issue 4 2004
    Anne M. Prouty Lyness
    No abstract is available for this article. [source]


    An Omnibus Test for Univariate and Multivariate Normality,

    OXFORD BULLETIN OF ECONOMICS & STATISTICS, Issue 2008
    Jurgen A. Doornik
    Abstract We suggest a convenient version of the omnibus test for normality, using skewness and kurtosis based on Shenton and Bowman [Journal of the American Statistical Association (1977) Vol. 72, pp. 206,211], which controls well for size, for samples as low as 10 observations. A multivariate version is introduced. Size and power are investigated in comparison with four other tests for multivariate normality. The first power experiments consider the whole skewness,kurtosis plane; the second use a bivariate distribution which has normal marginals. It is concluded that the proposed test has the best size and power properties of the tests considered. [source]


    Weighted Normality-Based Estimator in Correcting Correlation Coefficient Estimation Between Incomplete Nutrient Measurements

    BIOMETRICS, Issue 1 2000
    C. Y. Wang
    Summary. Consider the problem of estimating the correlation between two nutrient measurements, such as the percent energy from fat obtained from a food frequency questionnaire (FFQ) and that from repeated food records or 24-hour recalls. Under a classical additive model for repeated food records, it is known that there is an attenuation effect on the correlation estimation if the sample average of repeated food records for each subject is used to estimate the underlying long-term average. This paper considers the case in which the selection probability of a subject for participation in the calibration study, in which repeated food records are measured, depends on the corresponding FFQ value, and the repeated longitudinal measurement errors have an autoregressive structure. This paper investigates a normality-based estimator and compares it with a simple method of moments. Both methods are consistent if the first two moments of nutrient measurements exist. Furthermore, joint estimating equations are applied to estimate the correlation coefficient and related nuisance parameters simultaneously. This approach provides a simple sandwich formula for the covariance estimation of the estimator. Finite sample performance is examined via a simulation study, and the proposed weighted normality-based estimator performs well under various distributional assumptions. The methods are applied to real data from a dietary assessment study. [source]


    Expectations and experience of labial reduction: a qualitative study

    BJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 12 2007
    R Bramwell
    Objective, To understand women's reasons for undergoing labial reduction surgery, their expectations and experiences. Design, A retrospective qualitative study. Setting, British National Health Service Hospital. Sample, Six women who had experienced surgery for labial reduction. Method, Qualitative study using semi-structured interviews. Results, Results relating to ,Normality and defect', ,Sex lives' and ,The process of accessing surgery' are presented in this study. The women had seen their presurgery genital appearance as ,defective' and sought a ,normal' genital appearance. They thought that their presurgery genital appearance impacted on their sex lives, but their expectations of the effects of surgery on their sex lives were not all fulfilled. Information about labial surgery came from both the popular media and the health services. An emphasis on, for example, physical discomfort rather than appearance may have been used to legitimise a request for surgery. The process of accessing surgery had exposed them to potentially conflicting messages about their genital appearance. Conclusions, Women presenting for labial reduction may have unrealistic expectations of surgery, but their perceptions and expectations are long-standing and seem to be based on strong cultural norms. The gynaecologist is also meeting those women who have already negotiated the referral process. As demand for this surgery appears to be increasing, further research is needed. These findings may add to the case for the potential value of specialist staff to provide psychosocial interventions within gynaecology services. [source]


    Multiparameter immunophenotyping by flow cytometry in multiple myeloma: The diagnostic utility of defining ranges of normal antigenic expression in comparison to histology,

    CYTOMETRY, Issue 4 2010
    Elisa Cannizzo
    Abstract Background: Numerous studies have reported on the immunophenotype of plasma cells (PCs) in monoclonal gammopathy of undetermined significance (MGUS) and in plasma cell myeloma (PCM), but very few have examined the immunophenotype of normal PCs. In this study, an objective definition of normal range of expression for each antigen was found on normal control PCs. Using these new ranges of normal expression (new method) is different from using a static 20% of PCs cut-off for all antigens as described in the literature (traditional method). These newly calculated normal ranges for each antigen were applied to our data, and compared to histologic and immunohistochemical findings. Methods: Bone marrow samples from 46 patients with PC neoplasms and 15 normal controls were studied. A minimum of 100 PC were analyzed for each patient and control sample. An 8-color staining method was applied to study the immunophenotype of PCs, using a BD FACSCanto II. Results: By the new ranges of normality calculated in this study it was determined that different antigens have different level of expression on polyclonal PCs. CD19 correlated with histology by both the traditional and new methods, but had superior correlation by the new method. Conclusions: This report is the first 8-color immunophenotypic study of PCM in which a "range of normal expression" for each antigen is defined. This is a critical step to help distinguish between a normal and neoplastic PC immunophenotype and discern which antigens are of diagnostic importance. © 2010 Clinical Cytometry Society [source]


    Four- and five-color flow cytometry analysis of leukocyte differentiation pathways in normal bone marrow: A reference document based on a systematic approach by the GTLLF and GEIL,,

    CYTOMETRY, Issue 1 2010
    Christine Arnoulet
    Abstract Background: The development of multiparameter flow cytometry (FCM) and increasingly sophisticated analysis software has considerably improved the exploration of hematological disorders. These tools have been widely applied in leukaemias, lymphomas, and myelodysplasias, yet with very heterogeneous approaches. Consequently, there is no extensive reference document reporting on the characteristics of normal human bone marrow (BM) in multiparameter FCM. Here, we report a reference analysis procedure using relevant antibody combinations in normal human BM. Methods: A first panel of 23 antibodies, constructed after literature review, was tested in four-color combinations (including CD45 in each) on 30 samples of BM. After evaluation of the data, a second set of 22 antibodies was further applied to another 35 BM samples. All list-modes from the 65 bone marrow samples were reviewed collectively. A systematised protocol for data analysis was established including biparametric representations and color codes for the three major lineages and undifferentiated cells. Results: This strategy has allowed to obtain a reference atlas of relevant patterns of differentiation antigens expression in normal human BM that is available within the European LeukemiaNet. This manuscript describes how this atlas was constructed. Conclusions: Both the strategy and atlas could prove very useful as a reference of normality, for the determination of leukemia-associated immunophenotypic patterns, analysis of myelodysplasia and, ultimately, investigation of minimal residual disease in the BM. © 2009 Clinical Cytometry Society [source]


    Marketing Category Forecasting: An Alternative of BVAR-Artificial Neural Networks¶

    DECISION SCIENCES, Issue 4 2000
    James J. Jiang
    ABSTRACT Analyzing scanner data in brand management activities presents unique difficulties due to the vast quantity of the data. Time series methods that are able to handle the volume effectively often are inappropriate due to the violation of many statistical assumptions in the data characteristics. We examine scanner data sets for three brand categories and examine properties associated with many time series forecasting methods. Many violations are found with respect to linearity, normality, autocorrelation, and heteroscedasticity. With this in mind we compare the forecasting ability of neural networks that require no assumptions to two of the more robust time series techniques. Neural networks provide similar forecasts to Bayesian vector autoregression (BVAR), and both outperform generalized autoregressive conditional herteroscedasticty (GARCH) models. [source]


    Distribution of Aggregate Utility Using Stochastic Elements of Additive Multiattribute Utility Models

    DECISION SCIENCES, Issue 2 2000
    Herbert Moskowitz
    ABSTRACT Conventionally, elements of a multiattribute utility model characterizing a decision maker's preferences, such as attribute weights and attribute utilities, are treated as deterministic, which may be unrealistic because assessment of such elements can be imprecise and erroneous, or differ among a group of individuals. Moreover, attempting to make precise assessments can be time consuming and cognitively demanding. We propose to treat such elements as stochastic variables to account for inconsistency and imprecision in such assessments. Under these assumptions, we develop procedures for computing the probability distribution of aggregate utility for an additive multiattribute utility function (MAUF), based on the Edgeworth expansion. When the distributions of aggregate utility for all alternatives in a decision problem are known, stochastic dominance can then be invoked to filter inferior alternatives. We show that, under certain mild conditions, the aggregate utility distribution approaches normality as the number of attributes increases. Thus, only a few terms from the Edgeworth expansion with a standard normal density as the base function will be sufficient for approximating an aggregate utility distribution in practice. Moreover, the more symmetric the attribute utility distributions, the fewer the attributes to achieve normality. The Edgeworth expansion thus can provide a basis for a computationally viable approach for representing an aggregate utility distribution with imprecisely specified attribute weights and utilities assessments (or differing weights and utilities across individuals). Practical guidelines for using the Edgeworth approximation are given. The proposed methodology is illustrated using a vendor selection problem. [source]


    Crown fragment reattachment: report of an extensive case with intra-canal anchorage

    DENTAL TRAUMATOLOGY, Issue 2 2010
    Gustavo M. S. Oliveira
    Initially, the fractured crown was splinted to the adjacent teeth with orthodontic wire and composite resin. Subsequently, the crown fragment was reattached by means of a fiber post using a hybrid composite resin. Early stage success was achieved with the observance of normality in function, esthetics, and health of the tooth and surrounding periodontal structures. An athletic mouthguard was fabricated to prevent further trauma. Advantages, disadvantages, and prognosis of the treatment presented are discussed. [source]


    Gastric myoelectrical activity post-chemoradiotherapy and esophagectomy: a prospective study using subscapular surface recording

    DISEASES OF THE ESOPHAGUS, Issue 1 2004
    P. M. Lawlor
    SUMMARY., The aims of this study were to prospectively evaluate gastric function in esophageal cancer patients after chemoradiotherapy and following surgery, using cutaneous electrogastrography (EGG). Twenty-three patients with esophageal adenocarcinoma were recruited to the study. A subset of patients (n = 11) underwent neoadjuvant chemoradiotherapy and were also studied at 14 days after treatment. All patients underwent EGG studies prior to and following surgery, at 3 months postoperatively. Ten of these patients were also studied at medians of 6 months and 12 months after surgery. Twenty normal volunteers were used as controls. Post-operative EGG studies were monitored with a modified technique; the electrodes being placed in the subscapular region in the area of the transposed stomach. Following neoadjuvant treatment there was a significant increase in abnormal gastric myoelectrical activity involving changes in tachygastrias and decreased motility as measured by power ratio. Post-operatively there was a significant increase in bradygastria which persisted at 6 months but not at 12 months. There was a corresponding decrease in normogastria which persisted at 6 months and to a lesser extent at 12 months. Dominant frequency remained significantly depressed at 3, 6 and 12 months. Gastric myoelectrical activity is normal in untreated esophageal cancer. Neoadjuvant chemoradiotherapy causes a disruption to normal myoelectrical activity involving reduced motility and tachygastrias. Surgery causes a depression in dominant frequency with a reduced incidence of normogastria at 3 months and 6 months but with a tendency towards normality at 12 months. [source]


    An evidence-based approach to planning tobacco interventions for Aboriginal people

    DRUG AND ALCOHOL REVIEW, Issue 1 2004
    ROWENA G. IVERS
    Abstract Systematic reviews have shown that interventions such as the delivery of cessation advice by heath professionals and the use of nicotine replacement therapy are effective at increasing cessation rates, however little is known about whether such interventions are appropriate and effective for and thus transferable to Aboriginal Australians. The aim of this paper was to assess whether evidence of effectiveness for brief interventions for cessation and nicotine patches from studies conducted in other populations was likely to be transferable to Aboriginal people in the NT. This paper involved assessment of systematic reviews of evidence for the use of brief interventions for smoking cessation and the use of nicotine replacement therapy, when planning two such interventions for delivery to Aboriginal people. Emerging themes are discussed. There were many factors which were likely to mean that these brief advice on cessation and the use of nicotine patches were likely to be less effective when implemented in Aboriginal communities. The planned interventions were delivered in primary care, and were of low intensity. Few studies included in systematic reviews were set in the developing world or in minority populations. Many features of the context for delivery, such as the normality of the use of tobacco among Aboriginal people, the low socio-economic status of this population and cultural issues, may have meant that these interventions were likely to be less effective when delivered in this setting. Further research is required to assess effectiveness of tobacco interventions in this population, as evidence from systematic reviews in other populations may not be directly transferable to Aboriginal people. [source]


    Estimation of Nonlinear Models with Measurement Error

    ECONOMETRICA, Issue 1 2004
    Susanne M. Schennach
    This paper presents a solution to an important econometric problem, namely the root n consistent estimation of nonlinear models with measurement errors in the explanatory variables, when one repeated observation of each mismeasured regressor is available. While a root n consistent estimator has been derived for polynomial specifications (see Hausman, Ichimura, Newey, and Powell (1991)), such an estimator for general nonlinear specifications has so far not been available. Using the additional information provided by the repeated observation, the suggested estimator separates the measurement error from the "true" value of the regressors thanks to a useful property of the Fourier transform: The Fourier transform converts the integral equations that relate the distribution of the unobserved "true" variables to the observed variables measured with error into algebraic equations. The solution to these equations yields enough information to identify arbitrary moments of the "true," unobserved variables. The value of these moments can then be used to construct any estimator that can be written in terms of moments, including traditional linear and nonlinear least squares estimators, or general extremum estimators. The proposed estimator is shown to admit a representation in terms of an influence function, thus establishing its root n consistency and asymptotic normality. Monte Carlo evidence and an application to Engel curve estimation illustrate the usefulness of this new approach. [source]


    Robust principal component analysis and outlier detection with ecological data

    ENVIRONMETRICS, Issue 2 2004
    Donald A. Jackson
    Abstract Ecological studies frequently involve large numbers of variables and observations, and these are often subject to various errors. If some data are not representative of the study population, they tend to bias the interpretation and conclusion of an ecological study. Because of the multivariate nature of ecological data, it is very difficult to identify atypical observations using approaches such as univariate or bivariate plots. This difficulty calls for the application of robust statistical methods in identifying atypical observations. Our study provides a comparison of a standard method, based on the Mahalanobis distance, used in multivariate approaches to a robust method based on the minimum volume ellipsoid as a means of determining whether data sets contain outliers or not. We evaluate both methods using simulations varying conditions of the data, and show that the minimum volume ellipsoid approach is superior in detecting outliers where present. We show that, as the sample size parameter, h, used in the robust approach increases in value, there is a decrease in the accuracy and precision of the associated estimate of the number of outliers present, in particular as the number of outliers increases. Conversely, where no outliers are present, large values for the parameter provide the most accurate results. In addition to the simulation results, we demonstrate the use of the robust principal component analysis with a data set of lake-water chemistry variables to illustrate the additional insight available. We suggest that ecologists consider that their data may contain atypical points. Following checks associated with normality, bivariate linearity and other traditional aspects, we advocate that ecologists examine their data sets using robust multivariate methods. Points identified as being atypical should be carefully evaluated based on background information to determine their suitability for inclusion in further multivariate analyses and whether additional factors explain their unusual characteristics. Copyright © 2004 John Wiley & Sons, Ltd. [source]


    Oceanic influence on the precipitation of the south-east of Venezuela

    ENVIRONMETRICS, Issue 3 2002
    Lelys Guenni
    Abstract The Caroní catchment located in the south-east of Venezuela accounts for 70 per cent of the total hydropower energy of the country. On a year to year basis, it has been shown that low frequency large scale ocean-atmosphere phenomena are highly coupled to the hydroclimatology of the region, El Niño-Southern Oscillation (ENSO) being a major forcing mechanism of climatic and hydrological anomalies. Regional differences in amplitude and timing are due to complex orographic interactions, land surface-atmosphere feedback mechanisms and the evolution of dominant synoptic meteorological conditions. A detailed analysis of the relationship between rainfall and several large scale ocean-atmospheric variables was carried out to determine the potential use of large scale climatic information as predictors of the rainfall anomalies over the region. The problem was tackled in two ways: (a) first a seasonal dynamic rainfall model was fitted to monthly rainfall for different locations. In this case rainfall is assumed as a normal variate w which has been transformed to account for its departure from normality and truncated to account for the positive probability mass of zero values, which corresponds to negative values of the normal variable. The time series of the model parameters and the macroclimatic variables are inspected for their potential relationship with local rainfall via the stochastic model. (b) Second, dynamic linear regression models between the macroclimatic variables as predictors and the rainfall anomalies as predictant were fitted to evaluate and quantify the significance of these dependencies. Consistent patterns are observed with the Tropical Atlantic and Pacific ocean temperature anomalies, in which a significant negative relationship has been present since 1976, indicating an overall decrease (increase) in rainfall when the Pacific and the Tropical Atlantic are warmer (colder) than normal. In all cases the results suggest that the relationships between rainfall anomalies and the macroclimatic variables are not constant with time. Copyright © 2002 John Wiley & Sons, Ltd. [source]


    Models for the estimation of a ,no effect concentration'

    ENVIRONMETRICS, Issue 1 2002
    Ana M. Pires
    Abstract The use of a no effect concentration (NEC), instead of the commonly used no observed effect concentration (NOEC), has been advocated recently. In this article models and methods for the estimation of an NEC are proposed and it is shown that the NEC overcomes many of the objections to the NOEC. The NEC is included as a threshold parameter in a non-linear model. Numerical methods are then used for point estimation and several techniques are proposed for interval estimation (based on bootstrap, profile likelihood and asymptotic normality). The adequacy of these methods is empirically confirmed by the results of a simulation study. The profile likelihood based interval has emerged as the best method. Finally the methodology is illustrated with data obtained from a 21 day Daphnia magna reproduction test with a reference substance, 3,4-dichloroaniline (3,4-DCA), and with a real effluent. Copyright © 2002 John Wiley & Sons, Ltd. [source]


    Confidence intervals for the calibration estimator with environmental applications

    ENVIRONMETRICS, Issue 1 2002
    I. Müller
    Abstract The article investigates different estimation techniques in the simple linear controlled calibration model and provides different types of confidence limits for the calibration estimator. In particular, M-estimation and bootstrapping techniques are implemented to obtain estimates of regression parameters during the training stage. Moreover, bootstrap is used to construct several types of confidence intervals that are compared to the classical approach based on the assumption of normality. For some of these intervals, the second order asymptotic properties can be established by means of Edgeworth expansions. Two data sets,one on space debris and the other on bacteriological counts in water samples,are used to illustrate the method's environmental applications. Copyright © 2002 John Wiley & Sons, Ltd. [source]


    End-to-end jejuno-ileal anastomosis following resection of strangulated small intestine in horses: a comparative study

    EQUINE VETERINARY JOURNAL, Issue 4 2005
    D. I. RENDLE
    Summary Reasons for performing study: Small intestinal resection and anastomosis is a relatively common procedure in equine surgical practice. This study was designed to test objectively the subjective opinions of surgeons at the Liphook Equine Hospital that an end-to-end jejuno-ileal anastomosis (JIA) is an effective and clinically justifiable procedure, contrary to conventional recommendations. Hypothesis: An end-to-end JIA carries no greater risk of morbidity and mortality than an end-to-end jejunojejunal anastomosis (JJA). Methods: A retrospective observational study was performed on a population of 100 horses that had undergone small intestinal resection and end-to-end anastomosis. Two groups were identified; Group 1 (n = 30) had undergone an end-to-end JIA and Group 2 (n = 70) an end-to-end JJA. The 2 populations were tested for pre- and intraoperative comparability and for their equivalence of outcomes. Results: The 2 populations were comparable in terms of their distributions of preoperative parameters and type of lesion present. The observations used as outcome parameters (incidence risk of post operative colic, incidence risk of post operative ileus, duration of post operative ileus, rates of functioning original anastomoses at the time of discharge and at 12 months, survival rates at 6 months and 12 months) were equivalent between the 2 groups. Conclusion: End-to-end JIA carries no greater risk of morbidity and mortality than an end-to-end JJA. Potential relevance: Surgeons faced with strangulating obstructions involving the jejuno-ileal junction in which there remains an accessible length of viable terminal ileum may reasonably perform an end-to-end JIA. This has the potentially significant advantage over a jejunocaecal anastomosis of preserving more anatomical and physiological normality to the intestinal tract. The study was, however, relatively small for an equivalence study and greater confidence would be gained with higher numbers. [source]


    Optimal Portfolio Allocation under Higher Moments

    EUROPEAN FINANCIAL MANAGEMENT, Issue 1 2006
    Eric Jondeau
    C22; C51; G12 Abstract We evaluate how departure from normality may affect the allocation of assets. A Taylor series expansion of the expected utility allows to focus on certain moments and to compute the optimal portfolio allocation numerically. A decisive advantage of this approach is that it remains operational even for a large number of assets. While the mean-variance criterion provides a good approximation of the expected utility maximisation under moderate non-normality, it may be ineffective under large departure from normality. In such cases, the three-moment or four-moment optimisation strategies may provide a good approximation of the expected utility. [source]


    Clonally rearranged T-cell receptor , chain genes in HTLV-I carriers with abnormal, non-flower-like, lymphocytes

    EUROPEAN JOURNAL OF HAEMATOLOGY, Issue 4 2005
    Maria M. Sales
    Abstract:,Background:,The diagnosis of Adult T-cell leukemia/lymphoma ATLL subtypes in human T-lymphotropic virus type I (HTLV-I) carriers based in morphology and immunophenotype of lymphocytes can be challenger. We propose that polymerase chain reaction (PCR) amplification of the rearranged TCR gene in HTLV-I healthy carriers would be a convenient method for establishing the nature of the circulating T lymphocytes in asymptomatic HTLV-I carriers, presenting only mild and inconclusive signals of deviation from normality. Methods:,Using PCR, we analyzed the genetic recombination pattern of the T-cell , -chain receptor gene (TCR - ,) in order to identify clonal expansion of peripheral blood T lymphocytes in 17 HTLV-I-positive healthy carriers and in nine normal HTLV-I-negative blood donors. To evaluate the performance of PCR in detection of clonality, we also analyzed 18 patients with post-thymic/mature T-cell malignancies presenting circulating abnormal lymphocytes. Results:,Seven of the 17 HTLV-I positive individuals presented circulating abnormal lymphocytes; monoclonal or oligoclonal expansion of T-cells was detected in five of the 17 HTLV-I-positive individuals, all of them presenting abnormal lymphocytes. Clonal expansion was not detected in any of the negative controls or in any of the 12 remaining healthy carriers. All patients in the positive control group tested positive by PCR and Southern blots. Southern blots were negative for all 17 healthy carriers. Conclusions:,PCR amplification of segments of rearranged TCR- , is reliable for allowing early detection of small populations of clonal T cells in blood samples from asymptomatic HTLV-I carriers, providing an additional alert in the follow-up of carriers with abnormal circulating lymphocytes. [source]


    Differentiating normal, abnormal, and disordered personality

    EUROPEAN JOURNAL OF PERSONALITY, Issue 4 2005
    W. John Livesley
    Interest in the interface between normality and psychopathology was renewed with the publication of DSM-III more than 20 years ago. The use of a separate axis to classify disorders of personality brought increased attention to these conditions. At the same time, the definition of personality disorder as inflexible and maladaptive traits stimulated interest in the relationship between normal and disordered personality structure and functioning. The evidence suggests that the traits delineating personality disorder are continuous with normal variation and that the structural relationships among these traits resemble the structures described by normative trait theories. Recognition that personality disorder represents the extremes of trait dimensions emphasizes the importance of differentiating normal, abnormal, and disordered personality. It is argued that while abnormal personality may be considered extreme variation, personality disorder is more than statistical variation. A definition of personality disorder is suggested based on accounts of the adaptive functions of personality. Copyright © 2005 John Wiley & Sons, Ltd. [source]


    Development of an Improved Technique for the Perfusion of the Isolated Caudal Lobe of Sheep Liver

    EXPERIMENTAL PHYSIOLOGY, Issue 5 2000
    A. M. Ali
    The study was designed to develop an improved technique for perfusing the isolated caudal lobe of sheep liver. Twenty caudal lobes were perfused for 3-4 h, in a non-recirculating mode, with Krebs-Henseleit bicarbonate buffer. The perfusion system was designed to give a constant flow. The hepatic viability and functional normality of the perfused lobe were assessed by measuring the perfusion flow rate, pH, K+ efflux, O2 uptake, substrate uptake, gluconeogenesis from propionate and amino acids, and ureagenesis from ammonia and amino acids. Liver tissue was sampled for histological examination, as well as for the determination of liver glycogen and wet: dry weight ratio. The perfusion flow rate and pH were both stable throughout the perfusion. The potassium concentration in the effluent perfusate did not increase during the perfusion, suggesting that there was no loss of viability or hypoxia. The perfused lobe extracted more than 50% of the O2 supply. The rate of oxygen consumption was comparable to the rate reported in vivo. The initial glycogen content was reduced by about 40% after 4 h perfusion. The wet: dry weight ratio was 3.6, consistent with the absence of tissue oedema. Urea production was stimulated when NH4Cl (0.3 mM) was added to the medium but there was no significant increase in urea release when alanine (0.15 mM), glutamine (0.2 mM) or lysine (0.2 mM) was added. Urea production, however, increased by about 171% when a physiological mixture of amino acids was added. Propionate (0.5 mM), alanine and glutamine stimulated glucose production but not lysine or the complete amino acid mixture. Glutamine release was lower than that reported in the rat liver. Changing the direction of flow also revealed an apparent difference between livers from sheep and rats in their metabolism of ammonia. The improved technique offers a simple practical and inexpensive approach to many problems in ruminant physiology and nutritional biochemistry. [source]


    Co-administration of immunomodulator tuftsin and liposomised nystatin can combat less susceptible Candida albicans infection in temporarily neutropenic mice

    FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 3 2004
    Masood A Khan
    Abstract In order to develop a prospective chemotherapeutic agent against opportunistic infections, it is important to know that host factors such as degree of immunological debility as well as recovery of immune functions to normality may contribute significantly to a successful elimination of the pathogens. We demonstrated previously that concomitant delivery of antimicrobial agents and immunomodulators to the pathogen harbouring-host contributes to the complete elimination of the deep-seated fungal infections (aspergillosis and candidiasis) in animals with normal immune status. Considering that neutropenic hosts are the main targets of such infections, it can be argued about the potential of the immunomodulator-based therapy in subjects with non-functional immune system. To resolve the hypothesis, we studied the role of immunomodulator tuftsin against experimental murine candidiasis in temporarily neutropenic Balb/c mice. The neutropenic mice were challenged with an isolate of Candida albicans that was showing less susceptibility to both free and liposomised-amphotericin B. The co-administration of tuftsin increased the efficiency of liposomised-polyene antibiotics (nystatin and amphotericin B) against experimental murine candidiasis in immunocompromised Balb/c mice. Pretreatment with liposomised tuftsin prior to C. albicans infection clearly enhanced protection against candidiasis, suggesting a prophylactic role of tuftsin in normal and temporarily neutropenic animals. [source]


    Gamma regression improves Haseman-Elston and variance components linkage analysis for sib-pairs

    GENETIC EPIDEMIOLOGY, Issue 2 2004
    Mathew J. Barber
    Abstract Existing standard methods of linkage analysis for quantitative phenotypes rest on the assumptions of either ordinary least squares (Haseman and Elston [1972] Behav. Genet. 2:3,19; Sham and Purcell [2001] Am. J. Hum. Genet. 68:1527,1532) or phenotypic normality (Almasy and Blangero [1998] Am. J. Hum. Genet. 68:1198,1199; Kruglyak and Lander [1995] Am. J. Hum. Genet. 57:439,454). The limitations of both these methods lie in the specification of the error distribution in the respective regression analyses. In ordinary least squares regression, the residual distribution is misspecified as being independent of the mean level. Using variance components and assuming phenotypic normality, the dependency on the mean level is correctly specified, but the remaining residual coefficient of variation is constrained a priori. Here it is shown that these limitations can be addressed (for a sample of unselected sib-pairs) using a generalized linear model based on the gamma distribution, which can be readily implemented in any standard statistical software package. The generalized linear model approach can emulate variance components when phenotypic multivariate normality is assumed (Almasy and Blangero [1998] Am. J. Hum Genet. 68: 1198,1211) and is therefore more powerful than ordinary least squares, but has the added advantage of being robust to deviations from multivariate normality and provides (often overlooked) model-fit diagnostics for linkage analysis. Genet Epidemiol 26:97,107, 2004. © 2004 Wiley-Liss, Inc. [source]


    Loss of input from the mossy cells blocks maturation of newly generated granule cells

    HIPPOCAMPUS, Issue 7 2007
    Ana-Isabel Marqués-Marí
    Abstract The objective of this work is to check whether the input from the mossy cells to the inner molecular layer is necessary for the integration and maturation of the newly generated granule cells of the dentate gyrus (DG) in mice, and if after status epilepticus the sprouting of the mossy fibers can substitute for this projection. Newly generated cells were labeled by administration of 5-bromo-deoxyuridine either before or after pilocarpine administration. The neuronal loss in the hippocampus after administration of pilocarpine combined with scopolamine and diazepam seemed restricted to the hilar mossy cells. The maturation of the granule cells was studied using immunohistochemistry for calretinin and NeuN in combination with detection of 5-bromo-deoxyuridine. The sprouting of the mossy fibers was detected using Timm staining for zinc-rich boutons. In normal conditions, granule cells took about 2 weeks to lose the immature marker calretinin. After the loss of the mossy cells, newly generated granule cells remained expressing calretinin for more than a month, until the sprouting of the mossy fibers substituted for the projection of the mossy cells in the inner molecular layer of the DG. Therefore, a proper pattern of connectivity is necessary for the normal development and integration of newly generated granule cells in the adult brain. In a changed environment they cannot adapt transforming in other cell types; simply they are unable to mature. The sprouting of the mossy fibers, although aberrant and a probable source of epileptic activity, may be important for the correct physiology of the granule cells, restoring a likeness of normality in their connective environment. The survival of granule cells incorporated as mature neurons was increased after pilocarpine when compared with normal conditions. Thus, it is likely that the reorganization of the circuitry after the loss of the mossy cells facilitates the survival and incorporation of the newly generated granule cells. © 2007 Wiley-Liss, Inc. [source]


    Tail-dependence in stock-return pairs

    INTELLIGENT SYSTEMS IN ACCOUNTING, FINANCE & MANAGEMENT, Issue 2 2002
    Ines Fortin
    The empirical joint distribution of return pairs on stock indices displays high tail-dependence in the lower tail and low tail-dependence in the upper tail. The presence of tail-dependence is not compatible with the assumption of (conditional) joint normality. The presence of asymmetric tail-dependence is not compatible with the assumption of a joint student-t distribution. A general test for one dependence structure versus another via the profile likelihood is described and employed in a bivariate GARCH model, where the joint distribution of the disturbances is split into its marginals and its copula. The copula used in the paper is such that it allows for the existence of lower tail-dependence and for asymmetric tail-dependence, and is such that it encompasses the normal or t-copula, depending on the benchmark tested. The model is estimated using bivariate data on a set of European stock indices. We find that the assumption of normal or student-t dependence is easily rejected in favour of an asymmetrically tail-dependent distribution. Copyright © 2002 John Wiley & Sons, Ltd. [source]


    Mohr,Coulomb MiniCLoE model Uniqueness and localization studies, links with normality rule

    INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 1 2003
    R. Chambon
    Abstract This paper is devoted to a parametric study of a plane Mohr,Coulomb CLoE model. As CLoE models are designed with a consistency condition, it is possible to define a normality condition and to study its consequences. The positiveness of the second order work which implies the uniqueness of the solution of a small strain boundary value problem is studied firstly. Then the localization criterion is also studied. It is proved that normality has consequences similar to those for classical elasto plastic models. However if induced anisotropy is introduced in the hypoplastic CLoE model, some conclusions are no longer true. Finally plane strain experimental data are used to identify the parameters of the model. Copyright © 2002 John Wiley & Sons, Ltd. [source]


    Use of perioperative dialogues with children undergoing day surgery

    JOURNAL OF ADVANCED NURSING, Issue 1 2008
    Berith Wennström
    Abstract Title.,Use of perioperative dialogues with children undergoing day surgery Aim., This paper is a report of a study to explore what it means for children to attend hospital for day surgery. Background., Hospitalization is a major stressor for children. Fear of separation, unfamiliar routines, anaesthetic/operation expectations/experiences and pain and needles are sources of children's negative reactions. Method., A grounded theory study was carried out during 2005,2006 with 15 boys and five girls (aged 6,9 years) scheduled for elective day surgery. Data were collected using tape-recorded interviews that included a perioperative dialogue, participant observations and pre- and postoperative drawings. Findings., A conceptual model was generated on the basis of the core category ,enduring inflicted hospital distress', showing that the main problem for children having day surgery is that they are forced into an unpredictable and distressful situation. Pre-operatively, the children do not know what to expect, as described in the category ,facing an unknown reality'. Additional categories show that they perceive a ,breaking away from daily routines' and that they are ,trying to gain control' over the situation. During the perioperative period, the categories ,losing control' and ,co-operating despite fear and pain' are present and intertwined. Post-operatively, the categories ,breathing a sigh of relief' and ,regaining normality in life' emerged. Conclusion., The perioperative dialogue used in our study, if translated into clinical practice, might therefore minimize distress and prepare children for the ,unknown' stressor that hospital care often presents. Further research is needed to compare anxiety and stress levels in children undergoing day surgery involving the perioperative dialogue and those having ,traditional' anaesthetic care. [source]


    Living with a terminal illness: patients' priorities

    JOURNAL OF ADVANCED NURSING, Issue 6 2004
    Helen Carter BSc MD MBChB MPH
    Background., Our understanding of terminal illness and its consequences has been predominantly based on models derived from expert definition, rather than the patient's perspective. More recently, quality of life tools have been developed to enable patient choice in responses. However, an even broader approach may be needed to help identify goals for care for patients who are terminally ill. Aim., The aim of this paper is to report on an exploratory, qualitative study exploring what people living with terminal illness considered were the areas of priority in their lives. Methods., Ten people living with terminal cancer were interviewed. Analysis of the interviews incorporated principles of narrative analysis and grounded theory. Findings., Over 30 categories were identified and collated into five inter-related themes (personal/intrinsic factors, external/extrinsic factors, future issues, perceptions of normality and taking charge) encompassing the issues of importance to all participants. Each theme focused on ,life and living' in relation to life as it was or would be without illness. Practical issues of daily living and the opportunity to address philosophical issues around the meaning of life emerged as important areas. The central theme, ,taking charge', concerned with people's levels of life engagement, was integrally connected to all other themes. Conclusions., The findings suggest that the way in which health professionals manage patients' involvement in matters such as symptom relief can impact on existential areas of concern. Understanding patients' perspectives in relation to each theme may assist health professionals to develop management strategies appropriate to their needs. The findings challenge some aspects of traditional ,expert-defined' outcome measures. As this was an exploratory study, further work is needed to test and develop the model presented. [source]


    Physical indicators of cartilage health: the relevance of compliance, thickness, swelling and fibrillar texture

    JOURNAL OF ANATOMY, Issue 6 2003
    Neil D. Broom
    Abstract This study uses a bovine patella model to compare the relative merits of on-bone compliance and thickness measurements, free-swelling behaviour, and structural imaging with differential interference contrast (DIC) light microscopy to assess the biomechanical normality of the cartilage matrix. The results demonstrate that across a spectrum of cartilage tissues from immature, mature, through to mildly degenerate, and all with intact articular surfaces, there is a consistent pattern of increased free swelling of the isolated general matrix with age and degeneration. High swelling was always associated with major structural alterations of the general matrix that were readily imaged using DIC light microscopy. Conversely, for all tissue groups, no relationship was observed between thickness vs. compliance and compliance vs. general matrix swelling. Only in the proximal aspects of the normal mature and degenerate tissues was there a correlation between thickness and general matrix swelling. Free-swelling measurements combined with fibrillar texture imaging using DIC light microscopy are therefore recommended as providing a reliable and quick method of assessing the biomechanical condition of the cartilage general matrix. [source]


    The rate of learning-by-doing: estimates from a search-matching model

    JOURNAL OF APPLIED ECONOMETRICS, Issue 6 2010
    Julien Prat
    We construct and estimate by maximum likelihood a job search model where wages are set by Nash bargaining and idiosyncratic productivity follows a geometric Brownian motion. The proposed framework enables us to endogenize job destruction and to estimate the rate of learning-by-doing. Although the range of the observations is not independent of the parameters, we establish that the estimators satisfy asymptotic normality. The structural model is estimated using Current Population Survey data on accepted wages and employment durations. We show that it accurately captures the joint distribution of wages and job spells. We find that the rate of learning-by-doing has an important positive effect on aggregate output and a small impact on employment. Copyright © 2009 John Wiley & Sons, Ltd. [source]