Biais Cognitifs et Prise de Risque Managériale : Validation Empirique dans le Contexte Tunisien

Le contexte de prise de décision est entaché par des biais cognitifs. Se basant sur un échantillon de 46 entreprises tunisiennes cotées durant 1997-2006, nous avons d’abord observé l’influence de trois biais (sur-confiance, mimétisme et illusion de contrôle) sur la perception du risque et ensuite, nous avons analysé la relation entre cette perception et la prise de risque effective. Nos résultats concluent à l’existence d’une relation positive entre le biais de sur-confiance et de mimétisme et la prise de risque et à une relation négative entre le biais de l’illusion de contrôle et la prise de risque managériale.In this article, we analyse three cognitive biases which are overconfidence, illusion of control and herding. We investigate whether theses cognitive biases have an impact on managerial risk-taking. Using a sample of 46 Tunisian firms during the period 1997-2006, we put on evidence that a positive association exists between overconfidence, herding and managerial risk-taking. Nevertheless, the illusion of control bias has a negative impact on the proportion of Tunisian managers to take risks.Basándose en una muestra compuesta de 46 empresas tunecinas numeradas durante 1997-2006, procedimos en dos etapas: inicialmente, observamos la influencia de estas tres inclinaciones sobre la percepción del riesgo y en un segundo momento, analizamos la relación entre esta percepción y la toma de riesgo efectiva. Este planteamiento nos permitió concluir a la existencia de una relación positiva entre la inclinación de sobre confianza y la inclinación de mimetismo y la toma de riesgo y a una relación negativa entre la inclinación de la ilusión de control y la toma de riesgo de gestión

IMPACT DE LA QUALITE DU RESULTAT COMPTABLE SUR LE COUT DES FONDS PROPRES DES ENTREPRISES TUNISIENNES

En se basant sur le modèle de Fama et French (1993), nous avons essayé de mesurer l'impact de la qualité du résultat comptable sur le coût des fonds propres des entreprises tunisiennes. La revue de la littérature nous renseigne que plus la qualité de l'information – véhiculée par le résultat comptable – est meilleure, moins sera le risque informationnel, ce qui réduira in fine le coût des fonds propres. En effet, les investisseurs apprécieront davantage les entreprises dont la qualité de leurs résultats comptables est supérieure puisqu'ils seront incités à diversifier leurs portefeuilles, ce qui améliore le cours du titre et réduit le coût des fonds propres.Résultat comptable; asymétrie informationnelle; coût des fonds propres

RELATIVE AND ABSOLUTE RELIABILITY OF KARATE SPECIFIC AEROBIC TEST (KSAT) IN EXPERIENCED MALE ATHLETES

The present investigation was conducted to evaluate the relative and absolute reliability and the minimal detectable change (MDC95% of the karate specific aerobic test (KSAT) in male karate athletes. Sixteen subjects (age: 22.2±3.7 years, height: 175.7±6.7 cm, body mass: 72.7±7.2 kg and karate experience: 9.2±4.5 years) participated in this study and performed the KSAT twice (test-retest). Reliability of time to exhaustion (TE) was very good, with intraclass correlation coefficient ICC(3.1)>0.90, standard errors of measurement SEM<5% and 95% limits of agreement (LOA) -15.8 ± 74.7 s. The MDC95% of the KSAT was 81.42 s, rated as “satisfactory”. The dependent t test showed no significant difference between peak heart rate (HRpeak), peak lactate concentration (Lapeak) and rating of perceived exertion (RPE) between test and retest (P>0.05). Effect size for all variables was dz≤0.2, rated as trivial. Thus, when using the present test as a measure of aerobic fitness, a change greater than 9.4%(81.42 s) is necessary to be confident (at the 95% level) that the change in time to exhaustion reflects improvement and exceeds the measurement error. The KSAT is a reliable tool that can be used by practitioners for assessing aerobic fitness in experienced karate athletes

Expression, distribution et fonction du récepteur B1 des kinines dans la rétine lors du diabète et de la néovascularisation choroïdienne chez le rat

Les kinines sont d'importants médiateurs peptidiques impliqués dans la perméabilité vasculaire, le tonus vasomoteur et l'expression de cytokines pro-inflammatoires. De nombreuses études ont mis en évidence le rôle du récepteur B1 des kinines (RB1) dans l'inflammation systémique et celle de la rétine. L’inflammation joue un rôle prépondérant dans la rétinopathie diabétique et la dégénérescence maculaire liée à l’âge (DMLA), deux pathologies qui représentent les premières causes de cécité dans la population active et la population retraitée. L’objectif principal de cette thèse consiste à évaluer l’implication du RB1 dans ces deux pathologies oculaires. Les objectifs spécifiques sont définis comme suit : 1) étudier l'effet inflammatoire du RB1 et les altérations vasculaires conséquentes dans la rétine de modèles animaux de diabète et de néovascularisation choroïdienne ; 2) préciser la localisation cellulaire du RB1 dans ces rétines ; 3) évaluer la possibilité de traiter ces pathologies par un antagoniste du RB1 ; 4) étudier l’interaction possible entre le RB1 et le facteur de croissance de l’endothélium vasculaire (VEGF), connu pour son rôle clé dans la néovascularisation choroïdienne. Nos résultats confirment le rôle néfaste du RB1 dans les phases aiguës et avancées de la rétinopathie diabétique dans un modèle de diabète de type 1 induit par la streptozotocine (STZ) chez le rat. Le RB1 est fortement localisé sur les cellules endothéliales, la glie et les cellules ganglionnaires dans la rétine STZ. Les taux d'ARNm des récepteurs B1 et B2 des kinines, du VEGF et de son récepteur VEGF-R2 sont significativement élevés à 2 et 6 semaines dans la rétine STZ par rapport à la rétine contrôle. Les niveaux d'ARNm du RB1 demeurent augmentés à 6 mois. L’expression des récepteurs B1 (ARNm et immunodétection) et B2 (ARNm) est amplifiée par l’injection intravitréenne d’un agoniste du RB1 (R-838). En revanche, l’inhibition intravitréenne du RB1 (siRNA-RB1) inhibe l'expression génique des récepteurs des kinines, du VEGF et du VEGF-R2 dans la rétine STZ (Article 1). Les résultats du 2e article soulignent la contribution du RB1 dans une néovascularisation d’origine choroïdienne (CNV) dans un modèle de dégénérescence maculaire liée à l’âge chez le rat. Le RB1 est détecté par immunofluorescence sur les cellules endothéliales et gliales et il est co-localisé avec le VEGF-R2 sur les vaisseaux sanguins des rétines CNV. L’effet de l’application topique d’un antagoniste du RB1 (R-954) ou l’injection intravitréenne d’un anti-VEGF a été étudié sur la surexpression de plusieurs médiateurs inflammatoires impliqués dans la CNV. Ces deux traitements réduisent significativement la surexpression (ARNm) des récepteurs B1 et B2 des kinines, du TNF et de l’ICAM-1 dans la rétine CNV. L’anti-VEGF bloque aussi la surexpression de VEGF, VEGF-R2, HIF-1, MCP-1 et VCAM-1, tandis que le R-954 inhibe l'expression des médiateurs inflammatoires IL-1β et COX-2. Il est important de noter qu’un traitement topique avec le R-954 bloque l’hyperperméabilité vasculaire et l’infiltration leucocytaire dans les modèles de rétinopathie diabétique et de DMLA et diminue la taille de la CNV. Dans un 3e article, nous avons étudié les altérations morphologiques du lit vasculaire rétinien dans un modèle héréditaire de diabète de type 2, le rat Goto-Kakizaki (GK). Nous avons observé une accumulation de lipides dans la rétine et la choroïde associée à la surexpression du RB1 et du VEGF, à la production de macrophages et à la réactivité de la microglie. L’ensemble de ces études supporte un rôle délétère pour le RB1 dans la rétinopathie diabétique et la DMLA et pour lesquelles l’application topique d’un antagoniste de ce récepteur (R-954) peut s’avérer une nouvelle approche thérapeutique.Kinins are potent peptide autacoids involved in different physiological functions associated to enhanced vascular permeability, vascular tone and the expression of proinflammatory cytokines. Numerous studies have demonstrated the role of the kinin B1 receptor (B1R) in systemic and retinal inflammation. Inflammation plays a major role in diabetic retinopathy (DR) and age-related macular degeneration (AMD), two pathologies that represent the leading causes of blindness in the working and the retired population. The main objective of this thesis is to evaluate the involvement of B1R in these two ocular pathologies. Specific objectives are defined as follows: 1) to study the inflammatory effect of B1R and the consequent vascular alterations in retina of animal models of diabetes and choroidal neovascularization; 2) to specify the cellular localization of B1R in these retinas; 3) to evaluate the possibility of treating these pathologies by an B1R antagonist; 4) to investigate the possible interaction between B1R and vascular endothelial growth factor (VEGF), known for its key role in choroidal neovascularization. Our results confirm the detrimental role of B1R in the acute and advanced phases of diabetic retinopathy in streptozotocin-induced type 1 diabetes in rats. B1R is highly localized on endothelial cells, glial and ganglion cells in the STZ retina. The mRNAs expression of kinin B1 and B2 receptors, VEGF and VEGF-R2 are significantly elevated at 2 and 6 weeks in the STZ retina compared to control retina. B1R mRNA levels remain increased at 6 months. The expression of the B1 (mRNA and immunodetection) and B2 (mRNA) receptors is amplified by the intravitreal injection of a B1R agonist (R-838). In contrast, intravitreal inhibition of B1R (siRNA-RB1) inhibits gene expression of both kinin receptors, VEGF and VEGF-R2 in the STZ retina (Article 1). The results of the second article highlight the contribution of B1R in choroidal neovascularization (CNV) in a rat model of age-related macular degeneration. B1R is detected by immunofluorescence on endothelial and glial cells and co-located with VEGF-R2 on blood vessels of CNV retinas. The effect of topical application of B1R antagonist (R-954) or intravitreal injection of anti-VEGF was studied on the overexpression of several inflammatory iv mediators involved in CNV. These two treatments significantly reduce the overexpression (mRNA) of the B1 and B2 receptors of kinins, TNF-α and ICAM-1 in the CNV retina. Anti- VEGF also blocks the overexpression of VEGF, VEGF-R2, HIF-1, MCP-1 and VCAM-1, while R-954 inhibits the expression of inflammatory mediators IL-1β and COX-2. It is important to note that topical treatment with R-954 blocks vascular hyperpermeability and leukocyte infiltration in models of diabetic retinopathy and AMD and decreases the size of CNV. In a third article, we studied the morphological alterations of retinal vascular bed in a hereditary type 2 diabetes model, the Goto-Kakizaki rat (GK). We observed an accumulation of lipids in the retina and choroid associated with overexpression of B1R and VEGF, macrophage production and microglia reactivity. Collectively, these studies support a deleterious role for B1R in diabetic retinopathy and AMD and for which the topical application of an antagonist of this receptor (R-954) may be a new therapeutic approach

Comparison of In Vivo and In Vitro Digestibility in Rabbits

SIMPLE SUMMARY: We tested the Ankom Daisy(II) Incubator as an alternative to the in vivo procedures for measuring the in vitro dry matter digestibility of diets for rabbits. The results were variable according to the methods. Among those tested in the trial, the enzymatic one was more effective than those based on fecal inocula. We conclude that the Ankom Daisy(II) Incubator can be used to estimate the in vivo dry matter digestibility of rabbit diets, but the choice of the method proved to be fundamental for the reproducibility of results. ABSTRACT: The apparent dry matter digestibility of diets for rabbits was measured in vivo (ADMD(vv)) and in vitro with the Ankom Daisy(II) Incubator. Four diets were tested: low fiber (LF), LF + 5% of pregerminated fenugreek seeds (PGFS) (LF5), LF + 10% PGFS (LF10), and high fiber (HF). For the ADMD(vv), feces samples were collected from 56 White New-Zealand × Californian rabbits fed the 4 diets; animals were randomly allocated into 4 groups and housed in individual cages. For the in vitro trial, 3 methods were tested: fecal inoculum (FA) with Kansans State buffer; fecal inoculum with artificial saliva (FB); and multienzyme (ENZ). Fecal inocula were collected at slaughtering from the distal colon of rabbits fed ad libitum the LF diet. For FA and FB methods, the digestibility was measured at 36 and 48 h. The in vitro methods ranked the apparent dry matter digestibility of diets in the same order as in vivo, but ENZ values were always higher than FA and FB at 36 and 48 h. The prediction equations of in vivo digestibility with the ENZ method showed higher coefficient of determination (R(2) = 0.69) and lower SE (0.190) than FA and FB; also, reproducibility was higher with ENZ (CV = 3.1%). In conclusion, different methods can be applied to the Ankom Daisy(II) Incubator to study the digestibility in rabbits. In our trial, the better reproducibility was observed with the multienzyme method than FA and FB were probably related to the variability of inocula

Field tests of performance and their relationship to age and anthropometric parameters in adolescent handball players

Handball performance is influenced by age, anthropometric characteristics, technical skills, tactical understanding, and physical abilities. The aims of this study were (i) to determine differences in anthropometric characteristics and physical performance between adolescent handball players across age categories, and (ii) to determine which anthropometric and maturity variables have the greatest relative importance in fitness for this sport. Seventy-nine male handball players drawn from a team in the elite Tunisian Handball league [U18 ( = 10); U17 ( = 12); U16 ( = 17); U15 ( = 18); and U14 ( = 22)] volunteered for the investigation. Assessments included sprint performances; change in direction tests (T-half test and Illinois modified test); jumping tests (squat jump; counter movement jump; countermovement jump with aimed arms; five-jump test); medicine ball throwing; handgrip force; back extensor force and selected anthropometric measurements. The individual's age category affected all measurements, with U17 and U18 players showing larger body measurements and significantly better absolute results on all physical tests than U14, U15 and U16 contestants. Scores for the majority of physical performance tests were closely inter-correlated. We conclude that U17 and U18 players show significantly better absolute results than the younger players on all physical tests. Multiple linear regressions, using block-wise entry, indicate that age is the strongest predictor of jump and sprint performances. Several anthropometric characteristics, including body mass, standing height and lower limb length were closely correlated with performance test scores, but after allowing for age only body mass added to the prediction of jumping ability

Effect of somatic cell count on milk composition and mozzarella cheese quality

The aim of this study was to investigate the effect of somatic cell count (SCC) on mozzarella cheese quality. Three categories of raw milk were selected: low (SCC 987 000 cells/ml). Cheeses were produced on the same day of milk collection and were vacuum packed in plastic bags and analysed weekly for 60 days at cold storage (4 °C). As somatic cell count increases, casein content, casein as a percentage of true protein, lactose content, and titratable acidity decrease significantly in raw milk. No significant differences were observed in moisture, fat, and total protein contents among mozzarella cheese samples from the different SCC categories. However, cheese samples produced from high SCC milk had significantly higher pH (6.83) compared to samples produced with low and medium SCC milk, 5.58 and 5.46, respectively. The extension of proteolysis was not significant for cheese samples made from raw milk with low SCC during the first 30 days of cold storage. Proteolysis levels increased significantly on the 15th storage day for cheeses made with medium and high SCC, whereas significant increases were only observed on the 45th storage day for cheeses made with low SCC

Impact of Nitrogen Fertilization on Fusarium Foot and Root Rot and Yield of Durum Wheat

This study investigated the influence of nitrogen fertilization on Fusarium foot and root rot. Disease index, percentage of white heads, grain yield, weight of 1000 grains and nitrogen content were evaluated in durum wheat after artificial inoculation with Fusarium culmorum under field conditions. The trial was conducted using Karim wheat cultivar during growing season 2016/17. Five nitrogen rates, 0, 50, 100,150 and 200 kg N/ha were evaluated. Nitrogen supply at higher rates (150 and 200 kg/ha) significantly increased disease index, the percentage of white heads, the grain yield, the weight of 1000 grains and nitrogen content. These results suggest that high amounts of nitrogen fertilization may increase infection of wheat by Fusarium foot and root rot disease by influencing the plant physiology

Lower quarter Y balance test: reliability and relation to anthropometric parameters

This study aimed to analyze the Lower Quarter Y Balance Test (Y-BT) reliability in prepubescent male soccer players, as well as the relation between this dynamic balance test performance and some anthropometric parameter