Capital Utilisation and Retirement

This empirical analysis aims at assessing the effect of the economic climate and the intensity of capital utilisation on companies' capital retirement behaviour. It is conducted using individual company data, as well as original data on the degree of utilisation of production factors. The sample includes 6,998 observations over the period 1996-2008. This database is, to our knowledge, unique for the empirical analysis of the intensity of capital utilisation on firms' capital retirement behaviour. We adjust for endogeneity biases by means of instrumental variables. The main results obtained from the estimation of capital retirement models may be summarised as follows: i) The retirement rate decreases with the variations in cyclical pressures measured by the changes in output and the workweek of capital; this relation corresponds to a countercyclical decelerator effect on capital retirement; ii) The capital retirement rate increases with the structural intensity of capital utilisation; this effect, which corresponds to a wear and tear one, is nevertheless small compared to the decelerator one; iii) The profit rate does not have a significant impact on the retirement rate. Compared with the existing literature, here mainly Mairesse and Dormont (1985), the contribution of these results is to show, through the use of unique survey data, that the effect of the intensity of capital utilisation on capital retirement is structurally positive, via a wear and tear effect, and cyclically negative, via a decelerator effect which completes that already taken into account via the effect of changes in value added.Capital; Capital measure; Capital retirement; Capital utilisation

Capital Utilisation and Retirement

This empirical analysis aims at assessing the effect of the economic climate and the intensity of capital utilisation on companies' capital retirement behaviour. It is conducted using individual company data, as well as original data on the degree of utilisation of production factors. The sample includes 6,998 observations over the period 1996-2008. This database is, to our knowledge, unique for the empirical analysis of the intensity of capital utilisation on firms' capital retirement behaviour. We adjust for endogeneity biases by means of instrumental variables. The main results obtained from the estimation of capital retirement models may be summarised as follows: i) The retirement rate decreases with the variations in cyclical pressures measured by the changes in output and the workweek of capital; this relation corresponds to a countercyclical decelerator effect on capital retirement; ii) The capital retirement rate increases with the structural intensity of capital utilisation; this effect, which corresponds to a wear and tear one, is nevertheless small compared to the decelerator one; iii) The profit rate does not have a significant impact on the retirement rate. Compared with the existing literature, here mainly Mairesse and Dormont (1985), the contribution of these results is to show, through the use of unique survey data, that the effect of the intensity of capital utilisation on capital retirement is structurally positive, via a wear and tear effect, and cyclically negative, via a decelerator effect which completes that already taken into account via the effect of changes in value added

Les voies de signalisation calciques impliquées dans la réponse à l’étirement dans les artères intrapulmonaires. Modifications dans l’hypertension pulmonaire

Pulmonary hypertension (PH) is the main disease of the pulmonary circulation. This pathology ischaracterized by an increase of the intrapulmonary arterial (PA) pressure at rest (> 25 mmHg). This pressureexerts stretch forces on pulmonary arterial smooth muscle cells (PASMC). Stretch-activated channels (SAC)are present in PASMC and are able to transform a mechanical stimulus of stretch into a biological responseof contraction, a phenomenon called myogenic tone. Ca2+ is a second messenger that can be mobilizedfrom both the extracellular medium and intracellular Ca2+ stores. An increase of the intracellular Ca2+concentration ([Ca2+]i) leads to PASMC contraction. Using patch-clamp, microspectrofluorimetry,immunostainings and a pharmacological approach, we highlight Ca2+ signaling pathways induced by stretchin PASMC. Experiments were performed in normal rats and in two models of PH (chronically hypoxic ratsand monocrotaline rats). We showed that in normal rats a stretch induces a Ca2+ influx through SAC whichis amplified by (1) a plasma membrane hyperpolarization by BKCa channels and (2) a Ca2+ amplification bysubplasmalemnal ryanodine receptor 1 (RyR) of the sarcoplasmic reticulum (SR). Besides, mitochondria areinvolved in buffering cytoplasmic Ca2+. In PH rats, the Ca2+ influx by SAC and the Ca2+ release by RyR areenhanced due to a reorganization of intracellular Ca2+ stores. Furthermore, a functional associationbetween SR and caveolae conduce to a much greater amplification of the stretch-induced Ca2+ increase inPH rats. Finally, we showed that the mechanosensitive channel Piezo1 is expressed in PA. To conclude, thespatial organization of Ca2+ stores in PASMC is important for cell signaling and plays a casual role in PH.L’hypertension pulmonaire (HTP) est la principale pathologie de la circulation pulmonaire. Elle secaractérise par une augmentation maintenue de la pression dans les artères intrapulmonaires (AIP) (> à 25mmHg au repos). Cette pression exerce des forces d’étirement au niveau des cellules musculaires lisses desartères intrapulmonaires (CML d’AIP). Au niveau des CML, des canaux mécanosensibles appelés des SAC(« stretch-activated channels ») permettent de transformer un stimulus mécanique d’étirement en uneréponse biologique de contraction : c’est le tonus myogénique. Le Ca2+ est un second messager cellulairequi peut être aussi bien mobilisé depuis le milieu extracellulaire que depuis les réserves calciquesintracellulaires. Une augmentation de sa concentration cytoplasmique induit la contraction des CML. Grâceà des techniques de patch-clamp, de microspectrofluorimétrie, d’immunomarquages et à une approchepharmacologique, nous avons mis en évidence les voies de signalisations calciques qui sont mises en placeà la suite d’un étirement des CML d’AIP. Les expériences ont été réalisées à la fois chez des rats normaux etsur deux modèles de rats présentant une HTP (rats hypoxique chroniques et rats monocrotalines). Lesrésultats montrent que chez les rats normaux un étirement induit un influx de Ca2+ par les SAC. Cet influxcalcique est amplifié par (1) une hyperpolarisation de la membrane plasmique via l’activation de canauxBKCa, (2) une sortie de Ca2+ par les récepteurs à la ryanodine de type 1 (RyR1) du réticulum sarcoplasmique(RS) sous-membranaire. Afin de rétablir l’homéostasie calcique, les mitochondries tamponnent le Ca2+cytosolique. Chez les rats souffrant d’HTP, l’influx de Ca2+ par les SAC et l’amplification calcique par les RyRsont plus importants. Cette amplification est due à une réorganisation des réserves calciquesintracellulaires, notamment chez les rats monocrotalines. De plus, une association fonctionnelle entre lesréserves calciques du RS et les cavéoles conduit à des réponses calciques plus importantes après unétirement chez les rats HTP. Enfin, nous avons mis en évidence la présence de canaux mécanosensiblesPiezo1 dans les AIP de rats. En conclusion, l’organisation spatiale des partenaires calciques au sein des CMLd’AIP est importante pour la signalisation cellulaire et joue un rôle majeur dans l’HTP

La stratégie d'entreprise et la présence de rémunération variable dans le secteur syndiqué au Québec

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Assessment of mechanical properties of isolated bovine intervertebral discs from multi-parametric magnetic resonance imaging

BACKGROUND: The treatment planning of spine pathologies requires information on the rigidity and permeability of the intervertebral discs (IVDs). Magnetic resonance imaging (MRI) offers great potential as a sensitive and non-invasive technique for describing the mechanical properties of IVDs. However, the literature reported small correlation coefficients between mechanical properties and MRI parameters. Our hypothesis is that the compressive modulus and the permeability of the IVD can be predicted by a linear combination of MRI parameters. METHODS: Sixty IVDs were harvested from bovine tails, and randomly separated in four groups (in-situ, digested-6h, digested-18h, digested-24h). Multi-parametric MRI acquisitions were used to quantify the relaxation times T1 and T2, the magnetization transfer ratio MTR, the apparent diffusion coefficient ADC and the fractional anisotropy FA. Unconfined compression, confined compression and direct permeability measurements were performed to quantify the compressive moduli and the hydraulic permeabilities. Differences between groups were evaluated from a one way ANOVA. Multi linear regressions were performed between dependent mechanical properties and independent MRI parameters to verify our hypothesis. A principal component analysis was used to convert the set of possibly correlated variables into a set of linearly uncorrelated variables. Agglomerative Hierarchical Clustering was performed on the 3 principal components. RESULTS: Multilinear regressions showed that 45 to 80% of the Young’s modulus E, the aggregate modulus in absence of deformation H(A0), the radial permeability k(r) and the axial permeability in absence of deformation k(0) can be explained by the MRI parameters within both the nucleus pulposus and the annulus pulposus. The principal component analysis reduced our variables to two principal components with a cumulative variability of 52-65%, which increased to 70-82% when considering the third principal component. The dendograms showed a natural division into four clusters for the nucleus pulposus and into three or four clusters for the annulus fibrosus. CONCLUSIONS: The compressive moduli and the permeabilities of isolated IVDs can be assessed mostly by MT and diffusion sequences. However, the relationships have to be improved with the inclusion of MRI parameters more sensitive to IVD degeneration. Before the use of this technique to quantify the mechanical properties of IVDs in vivo on patients suffering from various diseases, the relationships have to be defined for each degeneration state of the tissue that mimics the pathology. Our MRI protocol associated to principal component analysis and agglomerative hierarchical clustering are promising tools to classify the degenerated intervertebral discs and further find biomarkers and predictive factors of the evolution of the pathologies

Effects of the nature of the doping salt and of the thermal pre-treatment and sintering temperature on spark plasma sintering of transparent alumina

A slurry of a-Al2O3 was doped with Mg, Zr and La nitrates or chlorides, in various amounts in the range 150-500 wt ppm and then freeze-dried to produce nanosized doped powder (~150 nm). The powder was sintered by SPS to yield transparent polycrystalline alpha alumina. The influence of the nature of the doping element and the starting salt, the thermal treatment before sintering and the sintering emperature on the transparency of the ceramics were investigated. The transparency of the ceramics of nanosized Al2O3 was shown to depend mainly on the way the powder was prepared, the nature of the doping salt also had an effect. Finally, a high real inline transmittance, reaching 48.1% was achieved after optimization

Intramolecular C-13 pattern in hexoses from autotrophic and heterotrophic C-3 plant tissues

The stable carbon isotope 13C is used as a universal tracer in plant eco-physiology and studies of carbon exchange between vegetation and atmosphere. Photosynthesis fractionates against 13CO2 so that source sugars (photosynthates) are on average 13C depleted by 20% compared with atmospheric CO2. The carbon isotope distribution within sugars has been shown to be heterogeneous, with relatively 13C-enriched and 13C-depleted C-atom positions. The 13C pattern within sugars is the cornerstone of 13C distribution in plants, because all metabolites inherit the 13C abundance in their specific precursor C-atom positions. However, the intramolecular isotope pattern in source leaf glucose and the isotope fractionation associated with key enzymes involved in sugar interconversions are currently unknown. To gain insight into these, we have analyzed the intramolecular isotope composition in source leaf transient starch, grain storage starch, and root storage sucrose and measured the site-specific isotope fractionation associated with the invertase (EC 3.2.1.26) and glucose isomerase (EC 5.3.1.5) reactions. When these data are integrated into a simple steady-state model of plant isotopic fluxes, the enzyme-dependent fractionations satisfactorily predict the observed intramolecular patterns. These results demonstrate that glucose and sucrose metabolism is the primary determinant of the 13C abundance in source and sink tissue and is, therefore, of fundamental importance to the interpretation of plant isotopic signals

Controle ativo de vibrações de baixas e altas frequências e ruído radiado de estruturas complexas

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia MecânicaEquipamentos industriais geramente são sujetos a vibrações mecânicas não desejadas que comprometem sua operação e integridade. Além disso, causam incômodo para o operador na forma de ruído. Desta observação surge a necessidade de controlar as vibrações e o ruído radiado. Atualmente existem várias abordagens de atenuação de ruído e vibrações as quais podem ser dividas em dois grupos: atenuação utilizando o controle passivo e o controle ativo. Quando o controle passivo não chega a ser possível ou eficiente, o controle ativo se torna necessário. Um sistema de controle ativo atenua a vibração ou ruído acústico medindo e contra-atuando a perturbação não desejada. O primeiro foco desta tese é prever a atenuação da perturbação, dependando do algorítmo de controle utilizado. A possibilidade de atenuar a radiação sonora de uma estrutura fechada é investigada nesse trabalho. O controle ativo é geralmente focalizado na região de baixas freqüências, porém este trabalho de pesquisa propõe uma solução para controlar globalmente a vibração de uma estrutura complexa em qualquer faixa de freqüência desejada. Todas as teorias desenvolvidas nesse trabalho foram comprovadas com experimentos