7,786 research outputs found

    Financial Turmoil in the Banking Sector and the Asian Lamfalussy Process: The Case of Four Economies

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    This paper investigates the prevailing financial regulatory structures and impact of the current financial turmoil on banking performance in four economies: the People's Republic of China (PRC); Hong Kong China; Singapore; and Taipei,China. Both the PRC and Hong Kong, China operate under a fragmented financial regulatory structure, while Singapore and Taipei,China have integrated structures. We examine the role of an integrated financial regulatory structure in helping financial institutions mitigate the impact of the financial crisis, using financial indicators of banks' capital structure and operating performance in these four economies between 2003 and 2008. Our analysis of the indicators reveals that banking performance under a fragmented financial regulatory structure is not worse than under integrated regulation. This implies that financial regulatory structure is not the main reason why Asian financial institutions suffered only limited losses from the current global financial crisis. However, given the growing complexity of the global financial system, and the relative weakness of current financial regulatory structures in Asia, this paper suggests that East Asian governments should refer to the Lamfalussy Process in the European Union and set up an Asia Financial Stability Dialogue to facilitate policy coordination for regional financial sector stability and development.asian financial regulation; global financial crisis; asian banking; prc; asian financial institutions; asian financial sector

    Angiotensin II Type 2 Receptor (AT2R) in Glomerulogenesis

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    Les données épidémiologiques indiquent que le diabète maternel est associé de manière significative aux anomalies congénitales des reins et des voies urinaires (CAKUT), ce qui implique un risque accru de CAKUT chez la progéniture des mères diabétiques par rapport à la population globale. Les causes de CAKUT sont multifactorielles, impliquant des facteurs génétiques et environnementaux. Le récepteur de l’angiotensine II de type 2 (AT2R) est l’un des gènes candidats impliqués dans le CAKUT humain et murin. Bien que de nombreuses études soutiennent l’influence des facteurs génétiques et environnementaux sur le développement rénal et la pathogenèse de CAKUT, les effets du gène AT2R et du milieu hyperglycémique in utero sur le développement rénal et les effets à long terme chez les enfants de mères diabétiques ne sont pas clairs. Cette thèse a pour objectif d'étudier l'influence de chaque facteur individuellement, ainsi que l'interaction entre ces deux facteurs. Premièrement, nous avons examiné si le déficit en AT2R (AT2RKO) altère la glomérulogenèse via la formation, la maturation et l'intégrité des podocytes. Nous avons observé que la glomérulogenèse était diminuée chez les embryons E15 AT2RKO, mais le nombre de néphrons ne présentaient aucune différence entre les nouveaux-nés AT2RKO et les souris de type sauvage. Les souris AT2RKO présentaient une dysplasie rénale avec un volume de touffes glomérulaires et un nombre de podocytes inférieurs à l’âge de trois semaines. Nos études ont démontré que la perte d’AT2R via l’augmentation de la génération des dérivés réactifs de l’oxygène (ROS) induite par la NADPH oxydase 4 (Nox4) stimulait l’interaction avec la protéine Hhip (‘Hedgehog interacting protein’), ce qui déclenchait en outre soit l’apoptose des podocytes par l’activation des voies de la caspase- 3 et de la p53, soit la transition épithéliale-mésenchymateuse des podocytes (EMT) par l’activation de la signalisation TGFβ1–Smad2/3. L'ARNm de Hhip glomérulaire était régulé positivement dans les biopsies rénales chez les patients atteints de glomérulosclérose segmentaire focale (FSGS). Les résultats suggèrent que le déficit en AT2R est associé à une perte ou un dysfonctionnement des podocytes et est dû, au moins en partie, à une expression accrue de Hhip ectopique dans les podocytes. Deuxièmement, nous avons cherché à établir les mécanismes sous-jacents par lesquels un milieu hyperglycémique in utero et un régime riche en graisses (HFD) après le sevrage accélèrent la programmation périnatale des lésions rénales. Nous avons observé que la progéniture des mères atteintes de diabète sévère avait un phénotype de restriction de croissance intra-utérine (IUGR) et avait développé une hypertension légère et des signes d'atteinte rénale à l'âge adulte. De plus, la progéniture nourrie avec une HFD post-sevrage présentait un rattrapage rapide de la croissance puis des lésions rénales associées à une augmentation de l’expression rénale de TGFβ1 et du collagène de type IV, à la production de ROS et à une accumulation de lipides rénaux, mais sans hypertension systémique. Des études in vitro ont démontré que le HFD ou les acides gras libres accéléraient le processus de programmation périnatale des lésions rénales, via une expression accrue de CD36 et de la protéine de liaison aux acides gras (Fabp4) qui cible les ROS, le facteur nucléaire-kappa B et le TGFβ1. Ces résultats indiquent que l'exposition précoce à l'HFD chez les enfants de mères diabétiques ayant subi une IUGR augmente le risque d'apparition de lésions rénales à l’âge adulte, mais pas d'hypertension. En résumé, AT2R joue un rôle essentiel dans la glomérulogenèse et influence l'intégrité et la fonction du podocyte via des altérations de l'expression de Hhip. En outre, les enfants de mères diabétiques ont un risque accru d'hypertension et de lésions rénales; la surnutrition postnatale accélère les lésions rénales chez ces enfants. Bien que le gène AT2R et le milieu hyperglycémique in utero aient tous les deux un impact sur le développement du rein et sur les maladies rénales ultérieures, l'interaction entre ces deux facteurs doit encore faire l'objet d'études supplémentaires.Epidemiologic data indicate that maternal diabetes significantly associates with congenital anomalies of the kidney and urinary tract (CAKUT), which implies an increased chance of CAKUT in the offspring of mothers with diabetes compared to the general population. The causes of CAKUT are multifactorial, involving genetic and environmental factors. The angiotensin II receptor type 2 (AT2R) is one of the candidate genes to be implicated in both human and murine CAKUT. Although numerous studies support the influence of genetic and environmental factors on kidney development and the pathogenesis of CAKUT, the impacts of the AT2R gene and hyperglycemic milieu in utero on kidney development and long-term outcomes in the offspring of diabetic mothers remain unclear. This thesis aims to investigate the influence of each factor individually, as well as their interaction. Firstly, we investigated whether AT2R deficiency (AT2R knock-out (KO)) impairs glomerulogenesis via podocytes formation, maturation and integrity. We observed that glomerulogenesis is decreased in AT2RKO embryos at embryonic day 15 (E15), but actual nephron numbers are no different between AT2RKO and wild-type newborn mice. AT2RKO mice exhibited renal dysplasia with lower glomerular tuft volume and reduced podocyte numbers at the age of three weeks. Our studies demonstrated that loss of AT2R via NADPH oxidase 4 (Nox4)-derived reactive oxygen species (ROS) generation stimulates ectopic hedgehog interacting protein (Hhip) expression, which further triggers either podocyte apoptosis by the activation of the caspase-3 and p53 pathways or podocyte epithelial–to– mesenchymal transition (EMT) by the activation of TGFβ1–Smad2/3 signaling. Glomerular Hhip mRNA is upregulated in kidney biopsies of patients with focal segmental glomerulosclerosis (FSGS). The results suggest that AT2R deficiency is associated with podocyte loss/dysfunction and is mediated, at least in part, via increased ectopic Hhip expression in podocytes. Secondly, we aimed to establish the underlying mechanisms by which a hyperglycemic milieu in utero and a post-weaning high-fat diet (HFD) accelerate the perinatal programming of kidney injury. We observed that the offspring of dams with severe maternal diabetes have an intrauterine growth restriction (IUGR) phenotype and develop mild hypertension and evidence of kidney injury in adulthood. Moreover, those offspring fed with a post-weaning HFD result in rapid catch-up growth and subsequent profound kidney injury associated with the augmentation of renal TGFβ1 and collagen type IV expression, increased production of ROS, and accumulation of renal lipids, but not systemic hypertension. In vitro studies demonstrated that HFD or free fatty acids accelerate the process of perinatal programming of kidney injury, via increased CD36 and fatty acid-binding protein 4 (Fabp4) expression, which targets ROS, nuclear factor-kappa B and TGFβ1 signaling. These results indicate that early postnatal exposure to HFD in IUGR offspring of diabetic dams increases the risk of later developing kidney injury, but not hypertension. In summary, AT2R plays an essential role in glomerulogenesis and influences the podocyte integrity and function via alterations of Hhip expression. In addition, the offspring of diabetic mothers have an increased risk of hypertension and kidney injury; postnatal overnutrition further accelerates kidney injury in those offspring. Although both AT2R and hyperglycemic milieu in utero have an impact on kidney development and later kidney diseases, the interaction between these two factors still needs further studies

    EXPERIMENTAL AND NUMERICAL STUDIES OF DRILL-STRING DYNAMICS

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    A drill string is the transmission component of rotary drill-rig system used for mining petroleum and natural gas resources. The drill-string system is essentially a long slender structure whose length can be in kilometers. Additionally, the drill-string is subject to discontinuous forces from interactions with the wellbore, which can cause erratic torsion oscillations and stick-slip motions. Here, a unique scaled experimental apparatus has been constructed to understand the dynamics of one section of the drill-string subjected to stick-slip interactions with an outer shell. In both the experimental and modeling efforts, the drill-string system is studied as a slender rod with large discs on either end, with the bottom disc being enclosed within a shell, which is representative of a borehole. The experimental setup allows for studies of stick-slip interactions between a drill-string like system and an outer shell, unlike the prior studies. A series of careful experiments are conducted with special attention to parameters such as the drive speed, the mass imbalance, and the nature of contact between the bottom disc and the outer shell. The experimental results indicate that the rotor motions can be divided into different phases, with each phase being characterized by its own unique features that include bumping, sticking, slipping, and rolling characteristics. In order to gain insights into the drill-string dynamics, reduced-order models have been developed inclusive of a novel drill-string wellbore force-interaction model that can account for stick-slip behavior. Both the experimental observations and model predictions are found to be in agreement, in terms of the system dynamics. Furthermore, parametric studies have been conducted and the findings are presented in the form of experimental and numerical simulation results, and the qualitative changes observed in the dynamics are discussed. These findings suggest that the drill-string curvature and contact friction plays an important role in determining the present of erratic motions. This dissertation effort provides clues to how the drive speed can be used as a control parameter to move the system out of regions of undesired dynamics and how the drill-string motions can be influenced to keep them close to the borehole center

    Chemical-biochemical process and ventilation study of the change in gaseous pollutants in ventilated swine buildings

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    The chemical analysis consists of sampling ammonia, methane, hydrogen sulfide, and carbon dioxide by Gas Chromatography/Mass Spectrometry (GC/MS). The results of the chemical-biochemical control experiment show that: (1) the chemical-bacteria additives slightly reduced the methane and carbon dioxide release, while the same additives did not show any effect on the reduction of ammonia; (2) the hydrogen sulfide contents of the swine manure continued to be low. Methane, ammonia, and carbon dioxide levels generated from stored swing manure were 3.76 and 2.2 ppm of methane, 0.35 and 0.11 ppm of ammonia, and 1000 and 470 ppm of carbon dioxide for treated and untreated manure, respectively;An emission model based on the two-film resistance theory is presented. Based on the model, the gases liquid phase resistance appears to control are nitrogen, oxygen, carbon dioxide, hydrogen sulfide, and methane, while ammonia is controlled by gas phase resistance. The average emission rate of methane, ammonia, and carbon dioxide at 15°C are 0.02, 1.52, and 0.50 g/min for untreated samples, and 0.04, 3.91, and 1.06 g/min for treated samples, respectively;A multiple airflow regions model is presented from the standpoint of the matrix method for dynamic system analysis. The model includes the local flow rate and internal mean-age of polluted air. The starting point in the model formulation is the flow matrix Q, consisting of the total flow rate between each airspace. At last, the local flow rates are also contained in the inverse flow matrix, Q[superscript](-1). The model calculation is in 3-D lumped form of control volumes representing conservation of airflow rate. The model shows that gaseous pollutant distribution is similar to the measured data from the research literature and field chamber test. The results also indicated that the mean-holding time, local mean-age, local flow-rate, and entrainment ratio of airflow can describe the dynamic behavior of gaseous pollutants in ventilated airspaces

    Gate-Tunable Tunneling Resistance in Graphene/Topological Insulator Vertical Junctions

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    Graphene-based vertical heterostructures, particularly stacks incorporated with other layered materials, are promising for nanoelectronics. The stacking of two model Dirac materials, graphene and topological insulator, can considerably enlarge the family of van der Waals heterostructures. Despite well understanding of the two individual materials, the electron transport properties of a combined vertical heterojunction are still unknown. Here we show the experimental realization of a vertical heterojunction between Bi2Se3 nanoplate and monolayer graphene. At low temperatures, the electron transport through the vertical heterojunction is dominated by the tunneling process, which can be effectively tuned by gate voltage to alter the density of states near the Fermi surface. In the presence of a magnetic field, quantum oscillations are observed due to the quantized Landau levels in both graphene and the two-dimensional surface states of Bi2Se3. Furthermore, we observe an exotic gate-tunable tunneling resistance under high magnetic field, which displays resistance maxima when the underlying graphene becomes a quantum Hall insulator
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