References of "Lambert, Philippe"
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See detailSmoothed nonparametric maximum likelihood estimation of the risk distribution underlying bonus-malus systems
Denuit, Michel; Lambert, Philippe ULg

in Proceedings of the Casualty Actuarial Society (2001), LXXXVIII

Mixed Poisson distributions are widely used for modeling claim counts when the portfolio is thought to be heterogeneous. The risk (or mixing) distribution then represents a measure of this heterogeneity ... [more ▼]

Mixed Poisson distributions are widely used for modeling claim counts when the portfolio is thought to be heterogeneous. The risk (or mixing) distribution then represents a measure of this heterogeneity. The aim of this paper is to use a variant of the Patilea and Rolin [15] smoothed version of the Simar [20] Non-Parametric Maximum Likelihood Estimator of the risk distribution in the mixed Poisson model. Empirical results based on two data sets from automobile third-party liability insurance demonstrate the relevance of this approach. The design of merit-rating schemes is discussed in the second part of the paper. [less ▲]

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See detailOsmotic behaviour of in vitro produced bovine blastocysts in cryoprotectant solutions as a potential predictive test of survival
Kaidi, Safia; Donnay, I.; Lambert, Philippe ULg et al

in Cryobiology (2000), 41

The osmotic behavior of bovine blastocysts produced in vitro was filmed during exposure to and dilution of cryoprotectant solutions used for vitrification. The relationship between the changes in the ... [more ▼]

The osmotic behavior of bovine blastocysts produced in vitro was filmed during exposure to and dilution of cryoprotectant solutions used for vitrification. The relationship between the changes in the diameter of embryos and their subsequent survival was assessed. Embryos collected on Day 6 and Day 7 postinsemination were exposed to 10% glycerol (GLY) for 5 min, 10% GLY + 20% ethylene glycol (EG) for 5 min, and 25% Gly + 25% EG for 30 s, before dilution in 0.85 M galactose and finally in embryo transfer freezing medium (ETF). Embryos that had a higher probability of survival behaved as perfect osmometers, shrinking, reexpanding, or swelling according to an identical pattern, whereas embryos that deviated from this standard usually did not survive. The initial embryo diameter, duration of shrinkage and expansion in 10% glycerol, duration of reexpansion in ETF, and final embryo diameter were clearly predictive of the ability to hatch after culture in vitro. On a given day postinsemination, larger blastocysts were more likely than smaller blastocysts to survive and hatch after exposure to cryoprotectants with or without vitrification. [less ▲]

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See detailAlveolar clearance in horses with chronic obstructive pulmonary disease
Votion, Dominique ULg; Vandenput, Sandrina ULg; Duvivier, D. H. et al

in American Journal of Veterinary Research (1999), 60

OBJECTIVE: To assess sensitivity of scintigraphic alveolar clearance rate as an indicator of alveolar epithelium damage in horses. ANIMALS: 5 healthy horses (group A) and 5 with chronic obstructive ... [more ▼]

OBJECTIVE: To assess sensitivity of scintigraphic alveolar clearance rate as an indicator of alveolar epithelium damage in horses. ANIMALS: 5 healthy horses (group A) and 5 with chronic obstructive pulmonary disease (COPD; group B). PROCEDURE: Horses underwent clearance rate (k [%/min]) determination. Clearance rate of group-B horses was determined after remission of the disease following 2 months at pasture (remission 1), stabling in a controlled environment (remission 2), and during crisis induced by exposure to moldy hay and straw. Methacholine challenge test was performed at each investigation period to determine nonspecific pulmonary airway hyperresponsiveness. Pulmonary function tests (PFT) also were performed, and cell populations in bronchoalveolar lavage (BAL) fluid were determined on another occasion. RESULTS: Group-B horses had significantly faster mean clearance rate during crisis (k = 4.30+/-0.95%/min), compared with that for remission 1(k = 1.98+/-0.55%/min), which did not differ from the rate in group-A horses (k = 1.95+/-0.33%/min). Despite lack of clinical signs of COPD during remission when stabled in a controlled environment, an intermediate value was found (k = 3.20+/-0.72%/min). CONCLUSIONS: This technique allowed grading of lung damage induced by COPD, whereas use of PFT and determination of BAL fluid cell populations failed to differentiate between remission 1 and remission 2. CLINICAL RELEVANCE: Determination of alveolar clearance rate by use of scintigraphy is a sensitive indicator of lung damage. A modified clearance rate was found despite the lack of clinical and functional changes [less ▲]

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See detailAnalysing financial returns using regression models based on non-symmetric stable distributions
Lambert, Philippe ULg; Lindsey, James ULg

in Journal of the Royal Statistical Society : Series C (Applied Statistics) (1999), 48

The daily evolution of the price of Abbey National shares over a 10-week period is analysed by using regression models based on possibly non-symmetric stable distributions. These distributions, which are ... [more ▼]

The daily evolution of the price of Abbey National shares over a 10-week period is analysed by using regression models based on possibly non-symmetric stable distributions. These distributions, which are only known through their characteristic function, can be used in practice for interactive modelling of heavy-tailed processes. A regression model for the location parameter is proposed and shown to induce a similar model for the mode. Finally, regression models for the other three parameters of the stable distribution are introduced. The model found to fit best allows the skewness of the distribution, rather than the location or scale parameters, to vary over time. The most likely share return is thus changing over time although the region where most returns are observed is stationary. [less ▲]

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See detailOn the appropriateness of marginal models for repeated measurements in clinical trials
Lindsey, James ULg; Lambert, Philippe ULg

in Statistics in Medicine (1998), 17

Although models developed directly to describe marginal distributions have become widespread in the analysis of repeated measurements, some of their disadvantages are not well enough known. These include ... [more ▼]

Although models developed directly to describe marginal distributions have become widespread in the analysis of repeated measurements, some of their disadvantages are not well enough known. These include producing profile curves that correspond to no possible individual, possibly showing that a treatment is superior on average when it is poorer for each individual subject, implicitly generating complex and implausible physiological explanations, including underdispersion in subgroups, and sometimes corresponding to no possible probabilistic data generating mechanism. We conclude that such marginal models may sometimes be appropriate for descriptive observational studies, such as sample surveys in epidemiology, but should only be used with great care in causal experimental settings, such as clinical trials. [less ▲]

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See detailScintigraphical Evaluation of Alveolar Clearance in Horses
Votion, Dominique ULg; Vandenput, Sandrina ULg; Duvivier, D. H. et al

in Veterinary Journal (1998), 156(1), 51-58

This study proposed a standardized method for measuring alveolar epithelium membrane permeability in the horse. The normal rate of clearance (%.min-1) from lung into blood of nebulized 99mTc-DTPA has been ... [more ▼]

This study proposed a standardized method for measuring alveolar epithelium membrane permeability in the horse. The normal rate of clearance (%.min-1) from lung into blood of nebulized 99mTc-DTPA has been established for healthy horses (Group A) compared with values obtained with horses suffering from chronic obstructive pulmonary disease (COPD; Group B). The 99mTc-DTPA clearance was measured in the caudoventral (R1) and in the half caudal (R2) parts of the left lung during different time intervals. The two regions aimed to define the influence of the airways on measured clearance (R2 contained proportionally more conducting airways than R1). It was concluded that a comparison of groups of subjects may be performed in R2 and on data collected during a 20 min period. The normal clearance rate in R2 was 1.80 +/- 0.46%.min-1 (T1/2R2 = 40.99 +/- 12.45 min) in Group A. In Group B, a significantly faster 99mTc-DTPA transfer rate was found (4.17 +/- 0.83%.min-1 or T1/2R2 = 17.17 +/- 3.38min). Bronchoalveolar lavage (BAL) suggested that the increased permeability measured in Group B could be the result of lung inflammatory responses. Our results have demonstrated the ability of the 99mTc-DTPA clearance test to detect alveolar epithelial damage in horses. Furthermore, we were able to show that a regional analysis of the alveolar-capillary barrier integrity may be performed satisfactorily in the equine patient. [less ▲]

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See detailPredictions in overdispersed series of counts using an approximate predictive likelihood
Lambert, Philippe ULg

in Journal of Forecasting (1997), 16

The generalized autoregression model or GARM, originally used to model series of non-negative data measured at irregularly spaced time points (Lambert, 1996a), is considered in a count data context. It is ... [more ▼]

The generalized autoregression model or GARM, originally used to model series of non-negative data measured at irregularly spaced time points (Lambert, 1996a), is considered in a count data context. It is first shown how the GARM can be expressed as a GLM in the special case of a linear model for some transform of the location parameter. The Butler approximate predictive likelihood (Butler, 1986, Rejoinder) is then used to define likelihood prediction envelopes. The width of these intervals is shown to be slightly wider than the Fisher (1959, pp. 128-33) and Lejeune and Faulkenberry (1982) predictive likelihood-based envelopes which assume that the parameters have fixed known values (equal to their maximum likelihood estimates). The method is illustrated on a small count data set showing overdispersion. [less ▲]

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See detailModelling irregularly sampled profiles of nonnegative dog triglyceride responses under different distributional assumptions
Lambert, Philippe ULg

in Statistics in Medicine (1996), 15

General methodology for modelling series of non-negative data observed at unequally spaced times is developed. The parameterization enables both the importance of the serial association, as well the order ... [more ▼]

General methodology for modelling series of non-negative data observed at unequally spaced times is developed. The parameterization enables both the importance of the serial association, as well the order of this dependence to be expressed. An example is given where the effects of three fibre based diets on dog triglyceride profiles are analysed and compared. Many different types of models based on common distributions such as the normal, exponential, gamma, Weibull and log-normal observations are presented. Comparison of possibly non-nested models fitted on the same data set is made using the Akaike criterion. [less ▲]

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See detailModelling of repeated series of count data measured at unequally spaced times
Lambert, Philippe ULg

in Journal of the Royal Statistical Society : Series C (Applied Statistics) (1996), 45

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See detailDynamic generalized linear models and repeated measurements
Lindsey, James ULg; Lambert, Philippe ULg

in Journal of Statistical Planning & Inference (1995), 47

The dynamic generalized linear model for non-normal data is extended for use in repeated measurements, when series of observations are available for more than one individual. Examples are given for count ... [more ▼]

The dynamic generalized linear model for non-normal data is extended for use in repeated measurements, when series of observations are available for more than one individual. Examples are given for count and duration data. [less ▲]

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See detailPhysical Properties of Particles of Ipratropium and Clenbuterol Generated by Equipment Suitable for the Inhalation of Drugs by Calves
Genicot, Bruno; Lapp, K.; Close, Roland et al

in Research in Veterinary Science (1995), 59(2), 164-167

When solutions of ipratropium and clenbuterol were atomised at 300 kPa and 450 kPa in equipment suitable for the inhalation of drugs by calves, the numbers, velocities and diameters of the particles ... [more ▼]

When solutions of ipratropium and clenbuterol were atomised at 300 kPa and 450 kPa in equipment suitable for the inhalation of drugs by calves, the numbers, velocities and diameters of the particles produced were similar. When the pressure was increased to 600 kPa more of the particles were less than 2 microns in diameter and fewer were more than 7 microns in diameter, the fractions of the total mass of the solution generated in these size ranges were similarly increased and decreased, and the velocities of the particles were increased. At any given pressure, the numbers of particles of different sizes, and the proportions of the total mass generated, were similar for the solutions of ipratropium and clenbuterol, but a solution of saline produced more particles with a diameter less than 3 microns. Particles from the solution of ipratropium had the highest velocity and particles from the solution of clenbuterol had the lowest velocity. [less ▲]

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See detailTechnical Study of Some Major Parameters Influencing the Performances of an Aerosol Delivery Equipment Suitable for Calves
Genicot, Bruno; Peckova, M.; Close, Roland et al

in Veterinary Research (1994), 25(5), 468-77

Aerosol delivery equipment, suitable for the treatment of bovine respiratory dysfunctions and including 2 parallelly positioned jet nebulizers, was studied in depth in order to determine the optimal ... [more ▼]

Aerosol delivery equipment, suitable for the treatment of bovine respiratory dysfunctions and including 2 parallelly positioned jet nebulizers, was studied in depth in order to determine the optimal working conditions in the field. Indeed, some factors might reasonably alter the performance of this equipment. Among these factors, the influences of the parallel position of jet nebulizers (in order to accommodate the breathing requirements of the cattle and achieve a rapid treatment), of the long feed pipe delivering compressed air (in order to keep the animal away from the compressor unit), and finally of the ambient temperature were studied, this equipment being essentially used during the winter season. This equipment could accommodate the breathing needs of cattle weighing up to 225 kg if a pressure of 600 kPa was developed upstream to the nebulizers. The rate of atomization was significantly reduced when working at ambient air temperatures (272.25 K < T < 274.65 K) close to those encountered in winter. This was especially true when pressure upstream to the nebulizers did not exceed 500 kPa. The immersion of the feed pipe for compressed air in hot water led to an increase in the rate of atomization without raising evaporative water losses, and reduced the drop in temperature in the nebulizer solution. Finally, the rate of atomization significantly increased when the face mask including the nebulizers was maintained so that the nebulizers were in a vertical position or at an angle not less than 60 degrees with respect to the ground. [less ▲]

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See detailInduction of a Serotonin-S2 Receptor Blockade During Early or Late Stage of Acute Respiratory Distress Syndrome in Double-Muscled Calves: A Comparative Study
Genicot, Bruno; Mouligneau, Frédéric; Lindsey, J. K. et al

in Journal of Veterinary Medicine. A, Physiology, Pathology, Clinical Medicine (1993), 40(4), 241-248

Ninety-four Belgian White and Blue double-muscled calves were involved in this study which aimed to compare the efficacy of a serotonin-S2 receptor blockade at two different stages of an acute respiratory ... [more ▼]

Ninety-four Belgian White and Blue double-muscled calves were involved in this study which aimed to compare the efficacy of a serotonin-S2 receptor blockade at two different stages of an acute respiratory distress syndrome (ARDS), i.e. at the occurrence of first clinical signs or when another anti-inflammatory compound was clinically shown to be ineffective. Metrenperone, a 5-hydroxytryptamine (5-HT2) blocker, was injected (intramuscularly, 5 times, at 12 hourly intervals, dose rate: 0.1 mg/kg) to (1) 58 calves referred to our laboratory after a treatment (group I) which lasted from 3 to 5 days and which did not improve the clinical status of the animals and (2) 36 calves investigated as soon as first clinical signs occurred (group II). Following the severity of the ARDS, the animals from group I needed to be classified into 2 groups: group IA (moderate ARDS - n = 45) and group IB (severe ARDS - n = 13). For animals in group I, the antibacterial compound previously used was maintained and administered during 4 more days whilst the previous anti-inflammatory drug was suppressed and replaced by metrenperone administered as mentioned above. In group II, each animal was treated with ceftiofur sodium as an antibacterial agent. A clinical score and a breathing score were calculated at each step of the investigation period, i.e. before (T0) and 1 hour (T1) after the first treatment, during the interval 12H-48H (T2) which followed this treatment and 168 H (T3) after this treatment. Four clinical parameters were also taken into account separately: rectal and cutaneous temperatures, respiratory and heart rates.(ABSTRACT TRUNCATED AT 250 WORDS) [less ▲]

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See detailEfficiency of 5-Hydroxytryptamine Receptor Blockade as Therapeutic Measure During Acute Respiratory Distress Syndrome in Double-Muscled Cattle
Genicot, Bruno; Mouligneau, Frédéric; Lindsey, J. K. et al

in Zentralblatt für Veterinarmedizin. Reihe A (1993), 40(3), 185-193

During this investigation, which involved 58 Belgian White and Blue double-muscled calves affected by a naturally occurring Acute Respiratory Distress Syndrome, the clinical efficiency of a 5-HT2 receptor ... [more ▼]

During this investigation, which involved 58 Belgian White and Blue double-muscled calves affected by a naturally occurring Acute Respiratory Distress Syndrome, the clinical efficiency of a 5-HT2 receptor blockade with metrenperone (group A) was compared to the efficiency of a non-steroidal (flunixine meglumine--group B) and a steroidal (prednisolone sodium succinate--group C) antiinflammatory drug. Each animal of this trial was treated with ceftiofur sodium as antimicrobial agent. A clinical score and a breathing score were calculated at each step of the investigation period, i.e. before (T0) and 1 hour (T1), 12 hours (H), 24 H, 48H and 168 H (T3) after the first treatment, the interval 12H-48H being considered as period T2. Three clinical parameters were also taken into account separately: rectal and peripheral temperatures and heart rate. A significant improvement of the clinical score was registered at T2 in group A and at T3 in groups A and B, while this score did not significantly change in group C. In group A, the breathing score was significantly improved at T2 and T3, but not in groups B and C. Peripheral and rectal temperatures recorded at T1 were, in group A, significantly increased and decreased respectively, but not significantly changed in groups B and C. The proportions requiring change of treatment during the investigation period were significantly (P = 0.022) different in the three groups, being 5.6, 21.4 and 50.0% in groups A, B and C respectively.(ABSTRACT TRUNCATED AT 250 WORDS) [less ▲]

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