Evaluation de L’impact de L’entrepreneuriat sur la Croissance Economique au Cameroun: une Analyse Econométrique

L’entrepreneuriat est au cœur des politiques de développement. Les gouvernements se trouvent toutefois confrontés à un défi nouveau, car favoriser l’entreprenariat en tant qu’institution socioéconomique est une démarche qui diffère très sensiblement de celle à adopter pour concevoir et mettre en œuvre d’autres mesures de politique économique. Pour dynamiser la création d’entreprise, le gouvernement Camerounais a élaboré des programmes et politiques afin d‘encourager davantage l’activité entrepreneuriale pour une économie qui se veut émergente. En vue d’évaluer l’impact de l’entrepreneuriat sur la  croissance  économique au Cameroun sur la période de 2005 à 2020, nous avons appliqué la méthode d’estimation ARDL (Autoregressive Distributed Lag). Les résultats montrent qu’à court terme, l’impact de l’entrepreneuriat sur la croissance est positif et significatif. À long terme, nous constatons un résultat similaire car l’entrepreneuriat exerce un effet positif et significatif. Ces résultats sous-entendent que les pouvoirs publics doivent davantage mettre un accent sur la création des start-ups.   Entrepreneurship is at the heart of developing policies. Governments are at all times faced with challenges because promoting entrepreneurship as a socio-economic institution is a significant approach different from that to be adopted to design and implement other measures of economic policies. To boost business creation, the Cameroonian government has developed programs and policies to further encourage entrepreneurial activity in an emerging economy. To encourage entrepreneurial activity in an emerging economy. To evaluate the entrepreneurship impact on economic growth in Cameroon over the period of 2005 to 2020, we applied the ARDL (Autoregressive Distributed Lag) estimation method. The results show that in the short term, the entrepreneurship impact on growth is positive and significant. In the long term, we find a similar result because entrepreneurship exercises a positive and significant effect. These results imply that public authorities should put more emphasis on the creation of start-ups

A Journey Into State-Space Models

Questa tesi riguarda la modellizzazione di serie storiche generate da processi latenti, utilizzando modelli "state-space". Vengono proposti nuovi modelli e metodologie per poi applicarli ad una variet\ue0 di casi tipici presenti in finanza ed economia. La tesi \ue8 suddivisa in sei capitoli. Il primo capitolo presenta le motivazioni della ricerca, i suoi obiettivi e la presentazione dei contenuti. Il secondo capitolo approfondisce il concetto di modelli "state-space", riporta e discute le procedure di filtraggio pi\uf9 comuni, e chiarisce alcune definizioni, propriet\ue0 e concetti matematici che verranno usati nei capitoli successivi. Nel Capitolo 3 viene proposto un nuovo modello "state-space" per tener conto delle asimmetrie ("skewness") nelle osservazioni, nel quale l'assunzione di normalit\ue0 non \ue8 pi\uf9 necessaria. La distribuzione normale viene, infatti, sostituita con la distribuzione "close skew-normal" che \ue8 pi\uf9 flessibile ed include la distribuzione normale. Imponendo una struttura auto-regressiva all'equazione di stato e un errore di misura distribuito secondo una "close skew-normal", si costruisce una versione "skewed" del noto filtro di Kalman. Quindi, nel Capitolo 4 si considera la metodologia di filtraggio robusta proposta da Calvet, Czellar and Ronchetti (2015, "Robust Filtering", Journal of the American Statistical Association) con una distribuzione t di Student per ottenere previsioni accurate che tengono conto di valori anomali e di errori di specificazione, sia per i modelli "finite state-space" sia "infinite state-space". Il Capitolo 5 presenta i fondamenti per la costruzione di modelli a volatilit\ue0 stocastica con errori "close skew-normal" nelle osservazioni. Infine, il Capitolo 6 riassume il contributo della tesi e discute possibili future estensioni della ricerca.This thesis is concerned with the modelling of time series driven by unobservable processes using state space models. New models and methodologies are proposed and applied on a variety of real life examples arising from finance and economics. The dissertation is comprised of six chapters. The first chapter motivates the thesis, provides the objectives and discusses the outline of the dissertation contents. In the second chapter, we define the concept of state space modelling, review some popular filtering procedures and recall some important definitions, properties and mathematical concepts that will be used in the subsequent chapters. In Chapter three, we propose a new state-space model that accounts for asymmetry, relaxing the assumption of normality and exploiting the close skew-normal distribution which is more flexible and extends the Gaussian distribution. By allowing a stationary autoregressive structure in the state equation, and a close skew-normal distributed measurement error, we also construct a skewed version of the well known Kalman filter. Then in Chapter four, we adapt the robust filtering methodology of Calvet, Czellar and Ronchetti (2015, "Robust Filtering", Journal of the American Statistical Association) to build a robust filter with Student-t observation density that provides accurate state inference accounting for outliers and misspecification; this for both finite and infinite state-space models. In the fifth chapter, we provide the foundations for the construction of stochastic volatility models with close skew-normal errors in the observation equation. The summary of the thesis, future works and possible extensions appear in Chapter six

Evaluation de L’impact de L’entrepreneuriat sur la Croissance Economique au Cameroun : Une Analyse Econometrique

L’objectif de cette présente étude est d’évaluer l’impact de l’entrepreneuriat sur la  croissance  économique au Cameroun sur la période de 2005 à 2020. L’entrepreneuriat est au cœur des politiques de développement. Les gouvernements se trouvent toutefois confrontés à un défi nouveau, car favoriser l’entreprenariat en tant qu’institution socioéconomique est une démarche qui diffère très sensiblement de celle à adopter pour concevoir et mettre en œuvre d’autres mesures de politique économique. Portant, pour dynamiser la création d’entreprise, le gouvernement Camerounais a élaboré des programmes et politiques afin encourager davantage l’activité entrepreneuriale pour une économie qui se veut émergente. Nous avons appliqué la méthode d’estimation ARDL (Autoregressive Distributed Lag). En plus, les résultats montrent qu’à court terme, l’impact de l’entrepreneuriat sur la croissance est positif et significatif.  A long terme, nous constatons un résultat similaire car l’entrepreneuriat exerce un effet positif et significatif. Ces résultats sous-entendent que les pouvoirs publics doivent davantage mettre un accent sur la création des start-ups.   The objective of this study is to assess the impact of entrepreneurship on economic growth in Cameroon over the period from 2005 to 2020. Entrepreneurship is at the heart of development policies. However, governments face a new challenge because fostering entrepreneurship as a socio-economic institution is a very different approach to designing and implementing other economic policy measures. To boost business creation, the Cameroonian government has developed programs and policies to further encourage entrepreneurial activity for an economy that wants to be emerging. We applied the ARDL (Autoregressive Distributed Lag) estimation method. In addition, the results show that in the short term, the impact of entrepreneurship on growth is positive and significant. In the long term, we find a similar result because entrepreneurship exerts a positive and significant effect. These results imply that public authorities should put more emphasis on the creation of start-ups

Evaluation de L’impact de L’entrepreneuriat sur la Croissance Economique au Cameroun : Une Analyse Econometrique

L’objectif de cette présente étude est d’évaluer l’impact de l’entrepreneuriat sur la  croissance  économique au Cameroun sur la période de 2005 à 2020. L’entrepreneuriat est au cœur des politiques de développement. Les gouvernements se trouvent toutefois confrontés à un défi nouveau, car favoriser l’entreprenariat en tant qu’institution socioéconomique est une démarche qui diffère très sensiblement de celle à adopter pour concevoir et mettre en œuvre d’autres mesures de politique économique. Portant, pour dynamiser la création d’entreprise, le gouvernement Camerounais a élaboré des programmes et politiques afin encourager davantage l’activité entrepreneuriale pour une économie qui se veut émergente. Nous avons appliqué la méthode d’estimation ARDL (Autoregressive Distributed Lag). En plus, les résultats montrent qu’à court terme, l’impact de l’entrepreneuriat sur la croissance est positif et significatif.  A long terme, nous constatons un résultat similaire car l’entrepreneuriat exerce un effet positif et significatif. Ces résultats sous-entendent que les pouvoirs publics doivent davantage mettre un accent sur la création des start-ups.   The objective of this study is to assess the impact of entrepreneurship on economic growth in Cameroon over the period from 2005 to 2020. Entrepreneurship is at the heart of development policies. However, governments face a new challenge because fostering entrepreneurship as a socio-economic institution is a very different approach to designing and implementing other economic policy measures. To boost business creation, the Cameroonian government has developed programs and policies to further encourage entrepreneurial activity for an economy that wants to be emerging. We applied the ARDL (Autoregressive Distributed Lag) estimation method. In addition, the results show that in the short term, the impact of entrepreneurship on growth is positive and significant. In the long term, we find a similar result because entrepreneurship exerts a positive and significant effect. These results imply that public authorities should put more emphasis on the creation of start-ups

Le travail des enfants : uniquement un problème de pauvreté ?

Cet article analyse les déterminants du travail des enfants âgés de 5 à 14 ans au Cameroun, en insistant sur les facteurs de vulnérabilité (état de pauvreté et chocs négatifs sur les revenus). L’étude utilise les données microéconomiques de la troisième Enquête camerounaise auprès des ménages (Ecam III). Le modèle probit bivarié mobilisé montre que le niveau de vie mesuré par le revenu a un effet négatif sur le travail des enfants et positif sur leur scolarisation. Ces effets sont néanmoins faibles après instrumentation du revenu. Par ailleurs, les variables de choc indiquent qu’une baisse brutale de revenu est positivement associée à un travail plus fréquent des enfants, tandis que la possession de terres, dont l’exploitation nécessite de la force de travail, tend à l’accroître.This study analyses the determinants of the supply of labour by children aged 5 to 14 in Cameroon while highlighting the effects of vulnerability factors (poverty and negative shocks). The study uses microeconomic data from the third Cameroon Household Survey (CHS III). The bivariate probit model that we use show that, all things being equal, the standard of living measured by income, has a negative effect on child labour, but significantly affects child schooling. However, these effects weaken after the instrumentation of income. Moreover, the shock variables indicate that a sharp fall in income is positively associated with higher frequencies of child labour, meanwhile land ownership, which requires more labour force than income for farming purposes, also tends to increase child labour

Clostridium perfringens Epsilon Toxin Targets Granule Cells in the Mouse Cerebellum and Stimulates Glutamate Release

Epsilon toxin (ET) produced by C. perfringens types B and D is a highly potent pore-forming toxin. ET-intoxicated animals express severe neurological disorders that are thought to result from the formation of vasogenic brain edemas and indirect neuronal excitotoxicity. The cerebellum is a predilection site for ET damage. ET has been proposed to bind to glial cells such as astrocytes and oligodendrocytes. However, the possibility that ET binds and attacks the neurons remains an open question. Using specific anti-ET mouse polyclonal antibodies and mouse brain slices preincubated with ET, we found that several brain structures were labeled, the cerebellum being a prominent one. In cerebellar slices, we analyzed the co-staining of ET with specific cell markers, and found that ET binds to the cell body of granule cells, oligodendrocytes, but not astrocytes or nerve endings. Identification of granule cells as neuronal ET targets was confirmed by the observation that ET induced intracellular Ca2+ rises and glutamate release in primary cultures of granule cells. In cultured cerebellar slices, whole cell patch-clamp recordings of synaptic currents in Purkinje cells revealed that ET greatly stimulates both spontaneous excitatory and inhibitory activities. However, pharmacological dissection of these effects indicated that they were only a result of an increased granule cell firing activity and did not involve a direct action of the toxin on glutamatergic nerve terminals or inhibitory interneurons. Patch-clamp recordings of granule cell somata showed that ET causes a decrease in neuronal membrane resistance associated with pore-opening and depolarization of the neuronal membrane, which subsequently lead to the firing of the neuronal network and stimulation of glutamate release. This work demonstrates that a subset of neurons can be directly targeted by ET, suggesting that part of ET-induced neuronal damage observed in neuronal tissue is due to a direct effect of ET on neurons

Effects of Low Amyloid-β (Aβ) Concentration on Aβ1-42 Oligomers Binding and GluN2B Membrane Expression.

Numerous studies have shown that amyloid-β (Aβ) modulate intracellular metabolic cascades and an intracellular Ca2+ homeostasis and a cell surface NMDA receptor expression alteration in Alzheimer's disease (AD). However most of these findings have been obtained by using non-physiological Aβ concentrations. The present study deals with the effect of low Aβ concentrations on cellular homeostasis. We used nerve growth factor-differentiated PC12 cells and murine cortical neurons sequentially treated with low chronic monomeric or small oligomeric Aβ concentrations and high acute oligomeric Aβ concentrations to bring out a priming effect of chronic treatment on subsequently high Aβ concentrations-elicited cellular response. Both cell types indeed displayed an enhanced capacity to bind oligomeric Aβ after monomeric or small oligomeric Aβ application. Furthermore, the results show that monomeric Aβ1-42 application to the cells induces an increase of the Ca2+-response and of the membrane expression of the extrasynaptic subunit of the NMDA receptor GluN2B in PC12 cells, while the opposite effects were observed in cultured neurons. This suggests a sequential interaction of Aβ with the cellular plasma membrane involving monomers or small Aβ oligomers which would facilitate the binding of the deleterious high molecular Aβ oligomers. This mechanism would explain the slow progression of AD in the human nervous system and the deep gradient of neuronal death observed around the amyloid plaques in the nervous tissue.journal articleresearch support, non-u.s. gov't2015importe

Skeletal-specific expression of Fgd1 during bone formation and skeletal defects in faciogenital dysplasia (FGDY; Aarskog syndrome)

FGD1 encodes a guanine nucleotide exchange factor (GEF) that specifically activates the Rho GTPase Cdc42; FGD1 mutations result in Faciogenital Dysplasia (FGDY, Aarskog syndrome), an X-linked developmental disorder that adversely affects the formation of multiple skeletal structures. To further define the role of FGD1 in skeletal development, we examined its expression in developing mouse embryos and correlated this pattern with FGDY skeletal defects. In this study, we show that Fgd 1, the mouse FGD1 ortholog, is initially expressed during the onset of ossification during embryogenesis. Fgd 1 is expressed in regions of active bone formation in the trabeculae and diaphyseal cortices of developing long bones. The onset of Fgd 1 expression correlates with the expression of bone sialo-protein, a protein specifically expressed in osteoblasts at the onset of matrix mineralization; an analysis of serial sections shows that Fgd 1 is expressed in tissues containing calcified and mineralized extracellular matrix. Fgd1 protein is specifically expressed in cultured osteoblast and osteoblast-like cells including MC3T3-E1 cells and human osteosarcoma cells but not in other mesodermal cells; immunohistochemical studies confirm the presence of Fgd1 protein in mouse calvarial cells. Postnatally, Fgd 1 is expressed more broadly in skeletal tissue with expression in the perichondrium, resting chondrocytes, and joint capsule fibroblasts. The data indicate that Fgd 1 is expressed in a variety of regions of incipient and active endochondral and intramembranous ossification including the craniofacial bones, vertebrae, ribs, long bones and phalanges. The observed pattern of Fgd 1 expression correlates with FGDY skeletal manifestations and provides an embryologic basis for the prevalence of observed skeletal defects. The observation that the induction of Fgd 1 expression coincides with the initiation of ossification strongly suggests that FGD1 signaling plays a role in ossification and bone formation; it also suggests that FGD1 signaling does not play a role in the earlier phases of skeletogenesis. With the observation that FGD1 mutations result in the skeletal dysplasia FGDY, accumulated data indicate that FGD1 signaling plays a critical role in ossification and skeletal development. © 2000 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/35167/1/1015_ftp.pd

SERPINE2 Polymorphisms and Chronic Obstructive Pulmonary Disease

A number of genome-wide linkage analyses have identified the 2q33.3-2q37.2 region as most likely to contain the genes that contribute to the susceptibility to chronic obstructive pulmonary disease (COPD). It was hypothesized that the SERPINE2 gene, which is one of the genes located at the 2q33.3-2q37.2 region, may act as a low-penetrance susceptibility gene for COPD. To test this hypothesis, the association of four SERPINE2 single nucleotide polymorphisms (SNPs; rs16865421A>G, rs7583463A>C, rs729631C>G, and rs6734100C>G) with the risk of COPD was investigated in a case-control study of 311 COPD patients and 386 controls. The SNP rs16865421 was associated with a significantly decreased risk of COPD in a dominant model for the polymorphic allele (adjusted odds ratio [OR]=0.66, 95% confidence interval [CI]=0.45-0.97, P=0.03). In haplotype analysis, the GACC haplotype carrying the polymorphic allele at the rs16865421 was associated with a significantly decreased risk of COPD when compared to the AACC haplotype (adjusted OR=0.58, 95% CI=0.38-0.89, P=0.01), and this effect was evident in younger individuals (adjusted OR=0.30, 95% CI=0.14-0.64, P=0.002). This study suggests that the SERPINE2 gene contributes to the susceptibility to COPD

Calcineurin activation contributes to noise-induced hearing loss

Acoustic overstimulation increases Ca 2+ concentration in auditory hair cells. Because calcineurin is known to activate cell death pathways and is controlled by Ca 2+ and calmodulin, this study assessed the role of calcineurin in auditory hair cell death in guinea pigs after intense noise exposure. Immediately after noise exposure (4-kHz octave band, 120 dB, for 5 hr), a population of hair cells exhibited calcineurin immunoreactivity at the cuticular plate, with a decreasing number of positive-stained cells on Days 1–3. By Day 7, the levels of calcineurin immunoreactivity had diminished to near control, non-noise exposed values, concomitant with an increasing loss of hair cells. Staining of hair cell nuclei with propidium iodide (PI), restricted to calcineurin-immunopositive cells, indicated breakdown of cell membranes symptomatic of incipient cell death. The local application of the calcineurin inhibitors, FK506 and cyclosporin A, reduced the level of noise-induced auditory brain stem response threshold shift and hair cell death, indicating that calcineurin is a factor in noise-induced hearing loss. The results suggest that calcineurin inhibitors are of potential therapeutic value for long-term protection of the morphologic integrity and function of the organ of Corti against noise trauma. © 2004 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34869/1/20267_ftp.pd