Search Frictions in Physical Capital Markets as a Propagation Mechanism

We build a Dynamic General Equilibrium model with search frictions for the allocation of physical capital and investigate its implications for the business cycle. While the model is in principle capable of generating substantial internal propagation to small exogenous shocks, the quantitative effects are modest once we calibrate the model to fit firm-level capital flows. We then extend the model with credit market frictions that lead to countercyclical default and countercyclical risk premia as in the data. Countercyclical default directly affects capital reallocation and has important general equilibrium income effects on labor supply. Yet, for calibrations in line with observed consumption dynamics, we find that even in this extended model, search frictions in physical capital markets play only a small role for business cycle fluctuations.Capital allocation frictions, search and matching, credit frictions, business cycles, dynamic general equilibrium

Analyse ontogénique de l'expression du gène codant la protéine kinase ZPK

ZPK est une nouvelle protéine sérine/thréonine kinase cytoplasmique dont la fonction cellulaire n’est pas encore établie. Dans le but d'élucider son rôle potentiel au cours du développement embryonnaire, nous avons effectué une analyse spatiale et temporelle de l'expression de l'ARNm de ZPK par hybridation in situ sur des embryons de souris entre les jours 11.5 et 17.5 de la période de gestation. La première expression de ZPK est détectée dans les cellules neuroépithéliales du cerveau dès le jour 11 du développement embryonnaire. Avec le temps, on observe une expression de ZPK dans la couche granulaire de la peau, dans les cellules épithéliales des villosités intestinales, dans les cellules acineuses du pancréas ainsi que dans les cellules épithéliales des tubules rénaux. Cette expression survient uniquement dans ces organes au moment où ces populations de cellules entament des événements morphogénétiques associés au processus de différenciation terminale. Dans l'ensemble, les résultats démontrent que ZPK est préférentiellement exprimé dans des populations de cellules différenciées ou en voie de différenciation terminale. Les résultats obtenus dans cette étude suggèrent que ZPK jouerait possiblement un rôle dans l'induction ou le maintien de l'état différencié de certaines populations de cellules

Costly Capital Allocation with Credit Market Frictions as a Propagation Mechanism *

Abstract Evidence from firm-level data shows that capital separation and reallocation are important phenomena. Aggregate gross investment flows are thus substantially larger than the net flows reported in the national accounts. Furthermore, separation rates vary inversely with the cycle while reallocation rates are strongly procyclical. This suggests that capital stocks are more volatile and procyclical than in standard business cycle models. We build a search-and-matching model for capital with endogenous separation due to costly state verification to capture these firm-level characteristics about capital flows. We find that compared to the frictionless counterpart but also compared to models of financial frictions without costly capital reallocation, our model generates substantial internal amplification and matches surprisingly well the persistence in U.S. output growth. This suggests that credit market frictions in combination with costly capital allocation have important business cycle effects. * We thank Alain Delacroix, Jean Imbs, Etienne Wasmer and seminar participants of the Journées du CIRPÉE 2005, HEC Montréal, the Bank of Canada, Paris I, the Swiss National Bank and HEC Lausanne for helpful comments. Financial support from FQRSC, SSHRC (Kurmann) and PAFARC-UQAM (Petrosky-Nadeau) is gratefully acknowledged

Effect of pelvic stabilization and hip position on trunk extensor activity during back extension exercises on a roman chair

Objective: To assess the effect of pelvic stabilization and hip position on the electromyographic activity of trunk extensors during Roman chair exercise. A secondary objective was to compare genders. Design: Repeated measures. Subjects: Eleven men and 11 women volunteers. Methods: Five trunk flexion-extension cycles for 3 Roman chair conditions: (i) pelvis unrestrained; (ii) pelvis restrained; and (iii) hip at 40° flexion. Electromyographic signals were recorded on the back muscles, as well as on the gluteus maximus and biceps femoris. The percentage of electro¬myographic amplitude relative to the maximal activity was used to assess the level of muscular activation of each muscle group across the exercises. Results: For both genders, the Roman chair conditions did not influence the activity of the back and gluteus muscles. The hip-at-40°-flexion condition significantly reduced the activity of the biceps femoris (average of 4–18%) relative to the other 2 conditions. Gender differences were observed on the activity of the biceps femoris in all Roman chair conditions. Conclusion: The hip-at-40°-flexion condition would allow the Roman chair exercise to train the targeted back muscles more specifically by overloading them over a longer duration in order to induce physiological changes

Occupational health and safety risks: Towards the integration into project management

a b s t r a c t Project management in industrial settings in many cases is deficient with respect to integrating OHS risks. This deficiency manifests itself as problems affecting the safety of industrial practices and is explained generally by poor knowledge of OHS within organizations and project teams. We present, through this paper, a critical review and provide an overview of research and industrial practices aimed at systematic integration of OHS risks into the execution of projects, based on published scientific literature. We thus introduce some of the tools, methods and approaches being developed or adapted to integrate OHS and a general description of the current status of this integration in various fields. Our focus includes, in fact, laws, management systems, OHS risk management throughout project life cycle and efforts to integrate OHS risk management to industrial safety practices including approaches using historical data and industrial interventions. We conclude that publications identified are mainly derived from the construction industry and we stress that the objectives, methodologies and results are largely heterogeneous. The integration of OHS risk is not systematic in all industrial fields despite the changing and improving laws and management systems. In order to complete the overview of OHS integration, we will suggest future reviews and research that specifically investigates other innovative OHS applications and many analyses of recent industrial accidents. Complete synopsis will give opportunities for researchers to use or improve methods and approaches to promote OHS risk management in the manufacturing sector that suffer from lack of knowledge in this area

Updated survey of the steroid-converting enzymes in human adipose tissues

Over the past decade, adipose tissues have been increasingly known for their endocrine properties, that is, their ability to secrete a number of adipocytokines that may exert local and/or systemic effects. In addition to these hormonal peptides, adipose tissues have long been recognized as significant sites for steroid hormone transformation and action. We hereby provide an updated survey of the many steroid-converting enzymes that may be detected in human adipose tissues, their activities and potential roles. In addition to the now well-established role of aromatase and 11β-hydroxysteroid dehydrogenase (HSD) type 1, many enzymes have been reported in adipocyte cell lines, isolated mature cells and/or preadipocytes. These include 11βHSD type 2, 17β-HSDs, 3β-HSD, 5α-reductases, sulfatases and glucuronosyltransferases. Some of these enzymes are postulated to bear relevance for adipose tissue physiology and perhaps for the pathophysiology of obesity. This elaborate set of steroid-converting enzymes in the cell types of adipose tissue deserves further scientific attention. Our work on 20α-HSD (AKR1C1), 3αHSD type 3 (AKR1C2) and 17β-HSD type 5 (AKR1C3) allowed us to clarify the relevance of these enzymes for some aspects of adipose tissue function. For example, AKR1C2 expression down-regulation in preadipocytes seems to potentiate the inhibitory action of dihydrotestosterone on adipogenesis in this model. Many additional studies are warranted to assess the impact of intra-adipose steroid hormone conversions on adipose tissue functions and chronic conditions such as obesity, diabetes and cancer

The Mixed Lineage Kinase Leucine-Zipper Protein Kinase Exhibits a Differentiation-Associated Localization in Normal Human Skin and Induces Keratinocyte Differentiation upon Overexpression

Leucine-zipper protein kinase/dual leucine zipper bearing kinase/mitogen-activated protein kinase-upstream kinase is a recently described protein serine/threonine kinase which belongs to the mixed lineage kinase family. The overall pattern of expression of the leucine-zipper protein kinase/dual leucine zipper bearing kinase/mitogen-activated protein kinase-upstream kinase gene in embryonic and adult mouse tissues suggested that this kinase could be involved in the regulation of epithelial cell proliferation and differentiation. In order to get more insights into the potential role of leucine-zipper protein kinase in these cellular processes, we characterized its expression in normal human skin, both at the mRNA and protein levels. In situ hybridization, western blotting, and indirect immunofluorescence studies were conducted to localize leucine-zipper protein kinase on various human skin tissues. This is one of the first reports that leucine-zipper protein kinase has a very precise pattern of expression in human skin epithelia, as both mRNA and protein are restricted to the granular layer of the epidermis and inner root sheath of hair follicles. Detection of leucine-zipper protein kinase protein on skin from various body sites, donors of different ages as well as on reconstructed human skin always reveals that leucine-zipper protein kinase is present only in the very differentiated keratinocytes of epidermis and hair follicles. To determine directly whether leucine-zipper protein kinase exhibits any effect on cell growth and differentiation, keratinocytes were transfected with an expression vector harboring the leucine-zipper protein kinase cDNA. The presence of this construct in keratinocytes results in growth arrest together with a concomitant increase in filaggrin expression. Collectively, our results indicate that leucine-zipper protein kinase plays an active part in cellular processes related to terminal differentiation of epidermal keratinocytes

Human visceral and subcutaneous adipocyte isolation and dedifferentiation

Mature adipocytes have been recently shown to reverse their phenotype into fibroblast-like cells in vitro through a technique called ceiling culture. Mature adipocytes can also be isolated from fresh adipose tissue for depot-specific characterization of their function and metabolic properties. Here, we describe a well-established protocol to isolate mature adipocytes from adipose tissues using collagenase digestion, and subsequent steps to perform ceiling cultures. Briefly, adipose tissues are incubated in a Krebs-Ringer-Henseleit buffer containing collagenase to disrupt tissue matrix. Floating mature adipocytes are collected on the top surface of the buffer. Mature cells are plated in a T25-flask completely filled with media and incubated up-side down for a week. An alternative 6-well plate culture approach allows the characterization of adipocytes undergoing dedifferentiation. Adipocyte morphology drastically changes over time of culture. Immunofluorescence can be easily performed on slides cultivated in 6-well plate as demonstrated 65 by FABP4 immunofluorescence staining. FABP4 protein is present in mature adipocytes but down-regulated through dedifferentiation of fat cells. Mature adipocyte dedifferentiation may represent a new avenue for cell therapy and tissue engineering