No description available.

This study set out to examine the Taiwan college students¡¦ underlying knowledge of English relative clauses in attempt to see what the factor(s) is/are that constrain(s) the learners¡¦ language acquisition process, whether it is the universal factor, the native language, or human general problem solving skill. Three predictor hypotheses were used in this investigation: NAPH, PDH, and SOHH, which are motivated by different theoretical backgrounds. The NPAH is based on the typological markedness, the PDH is based on the notion of human limited capacity of short term memory, and SOHH the combination of NPAH and PDH, and the structural difficulty of relative clause. The data from 84 non-English major college students of NSYSU were elicited using three kinds of tasks: sentence combination test, Chinese-English translation test, and grammaticality judgment test. 12 types of English relative clauses were analyzed in this study, namely SS, SO, SIO, SOPREP, SGEN, SOCOMP, OS, OO,OIO, OOPREP,OGEN, OOCOMP. In addition, the learners¡¦ avoidance strategies were extensively analyzed to see what was actually avoided as they were engaged in the formation of English relative clauses. Implicationally, the results suggest that Universal Grammar may be still operative in the minds of the adult FL language learners. Overall, we have the following findings: 1.The learners¡¦ acquisition of relative clauses is largely constrained by the universal markedness by NPAH, except GEN, and the order between IO and OPREP. 2.The retention of pronoun is largely constrained by the linguistic universals of NPAH, but Chinese also has certain influence on the learners¡¦ choice of supplying resumptive pronoun. 3.The learners largely did experience more difficulty in center-embedded relative clauses, which matches PDH. 4.Largely, SOHH is a valid prediction of the learners¡¦ acquisition of relative clauses. 5.The learners tended to avoid relativization on the positions low on the NPAH, except GEN. 6.The learners did frequently avoid OCOMP relatives and center-embedded relative clauses.

L’étude des réseaux protéiques perturbés au cours de l’infection par les petits virus oncogéniques amena, vers la fin des années 80, à la découverte de nombreux régulateurs clés de la division et de la survie cellulaire. Parmi ceux-ci, la protéine E4F1 fût initialement identifiée comme une cible de l’oncoprotéine virale E1A. Originellement identifié comme un facteur de transcription, E4F1 est également une ubiquitine-E3 ligase atypique pour d'autres facteurs de transcription tel que le suppresseur de tumeurs p53. Au travers de ses multiples activités, E4F1 est nécessaire à la prolifération des cellules somatiques et souches, et à la survie des cellules cancéreuses. De plus, les travaux de différents laboratoires dont le mien suggèrent qu’E4F1 se situe au carrefour de plusieurs voies de signalisation qui sont fréquemment altérées au cours de l’oncogenèse, et notamment la voie impliquant le suppresseur de tumeurs p53. Afin d’étudier les fonctions physiologiques in vivo d’E4f1, mon laboratoire d’accueil a développé plusieurs modèles de souris génétiquement modifiées. La caractérisation de ces modèles a permis de mettre en évidence un rôle majeur d'E4F1 dans l'homéostasie de la peau. Plus précisément, E4F1 régule le pool de cellules souches de l'épiderme au travers de son rôle dans une voie de signalisation qui implique la protéine p53 et deux de ces régulateurs en amont: Arf et Bmi1. Cependant, il semble que les effets d'E4F1 dans le contrôle du maintien des cellules souches s'étendent au delà de son rôle sur cette voie de signalisation. En effet, j'ai récemment pu démontrer qu'E4F1, au travers de ces fonctions transcriptionnelles, régule directement l'expression d'un sous-groupe de gènes impliqués dans la régulation de l'activité de la pyruvate déshydrogénase (PDH). La PDH est un complexe multimérique situé dans la mitochondrie qui catalyse la décarboxylation du pyruvate (le produit final de la glycolyse) en acétyl coenzyme A (AcCoA), liant ainsi le métabolisme du pyruvate au cycle de Krebs. J’ai pu montrer que l’inactivation d’E4f1 spécifiquement dans l'épiderme conduisait à une diminution importante de l’activité de PDH et à une reprogrammation métabolique de ces cellules. Cette reprogrammation a pour conséquence d'altérer le micro-environnement des cellules souches qui conduit à leur détachement de leur niche et aboutit in fine à une absence du renouvellement de l'épiderme. Cette partie de mes travaux a donc permis d'illustrer pour la première fois l'importance du métabolisme du pyruvate dans l'homéostasie des cellules souches de la peau. Sur la base de ces résultats, je poursuis l'analyse des fonctions d’E4f1 dans l'homéostasie de la peau en étudiant son rôle dans d'autres types cellulaires tels que les mélanocytes. / The multifunctional protein E4F1 is an essential regulator of normal skin homeostasis. During my Phd, I demonstrated that E4f1 inactivation in adult skin results in stem cell autonomous defects causing exhaustion of the epidermal stem cell (ESC) pool. At the molecular level, I identified E4F1 as a new regulator of the pyruvate dehydrogenase complex (PDC) in keratinocytes, an essential mitochondrial complex that converts pyruvate into Acetyl-CoEnzyme A. Using genetically engineered mouse models, I showed that E4F1-mediated control of PDH activity is required to maintain normal skin homeostasis. Consistently, E4F1 deficiency in basal keratinocytes resulted in deregulated expression of dihydrolipoamide acetlytransferase (Dlat), a gene encoding the E2 subunit of the PDC, and impaired PDH activity. The metabolic reprogramming of E4f1 KO keratinocytes associated with the redirection of the glycolytic flux towards lactate production and increased lactate secretion in their microenvironment, leading to enhanced activity of extra-cellular-matrix remodelling proteases Finally, these defects ended in alterations of the basement membrane, ESC mislocalization and the exhaustion of the ESC pool. In the second part of my thesis, I have evaluated the role of E4F1-mediated control of the PDC in melanocytes and showed that the metabolic activities of E4F1 are important for melanocyte function. Consistently, mice with E4f1-deficient melanocytes exhibited hair graying and skin pigmentation defects. Altogether, my data demonstrate the importance of E4f1-mediated control of pyruvate metabolism for normal skin homeostasis.

No description available.

The ability to adapt fuel usage to nutrient availability is termed metabolic flexibility, and is influenced by activity of the pyruvate dehydrogenase complex (PDC). The Virginia lines of chickens are a unique model of anorexia and obesity that have resulted from 56 generations of artificial selection for high (HWS) or low (LWS) juvenile body weight. We hypothesized that hyperphagia and obesity in juvenile HWS chickens are associated with altered fatty acid oxidation efficiency and metabolic flexibility in tissues associated with energy sensing and storage, and relative cellular hypertrophy in white adipose tissue. Hypothalamus, liver, Pectoralis major, gastrocnemius, abdominal fat, clavicular fat and subcutaneous fat were collected from juvenile (56-65 day-old) HWS and LWS chickens for metabolic, gene expression and histological assays. The HWS chickens had reduced fatty acid oxidation efficiency in abdominal fat (P < 0.0001) and reduced rates of oxidation in abdominal fat and gastrocnemius (P < 0.0001) as compared to LWS. There was reduced citrate synthase activity in white adipose tissue (P < 0.0001) and greater metabolic inflexibility in skeletal muscle (P = 0.006) of HWS compared to LWS. Greater pyruvate dehydrogenase kinase 4 (PDK4) and forkhead box O1 (FoxO1) mRNA were found in skeletal muscle and white adipose tissue of 56-day-old HWS than LWS. Expression of peroxisome proliferator-activated receptor γ (PPARγ) in all adipose tissue depots was greater (P < 0.05) in LWS than in HWS chickens. The HWS chickens had larger (P < 0.0001) and fewer (P < 0.0001) adipocytes per unit area than LWS. These results suggest that the HWS chickens have impaired metabolic flexibility and fatty acid oxidation efficiency due to an up-regulation of pyruvate dehydrogenase activity to accommodate the influx of acetyl CoA from fatty acid oxidation in skeletal muscle and white adipose tissue. These metabolic adaptations can be linked to differences in gene expression regulation and body composition between the lines. Adipocyte cellularity data are consistent with greater oxidative efficiency in the adipose tissue of LWS, because of the greater number of unfilled cells in all depots that were sampled. Results can be extrapolated to agricultural production in the understanding of factors regulating the amount of lipid deposition in chicken carcass fat. Results may also provide insight into eating disorders and the development of obesity. / Master of Science

Streptococcus mutans is a facultative member of the oral plaque and is associated with dental caries. It is able to survive long periods of sugar starvation. The purpose of this project was to explore specific avenues that S. mutans may use in order to cope with carbohydrate deprivation. Intracellular polysaccharide (IPS) is accumulated by S. mutans when grown in excess sugar, and can contribute towards the cariogenicity of S. mutans. Inactivation of the glgA gene, encoding a putative glycogen synthase, prevented accumulation of IPS in batch cultures grown with excess glucose or sucrose. Inactivation of the pul gene, encoding a putative pullulanase which is thought to be involved in IPS catabolism, did not prevent IPS accumulation. IPS was found to be important for the persistence of S. mutans grown in batch culture with excess glucose, and then starved of glucose. In these conditions, the IPS was largely used up within one day of starvation, and yet survival of the parental strain was extended by at least 15 days beyond that of the glgA and pul mutants; potentially, some feature of IPS metabolism, distinct from providing nutrients, is important for persistence. IPS was not needed for persistence when sucrose was carbon source or when mucin was present in batch cultures. IPS accumulation was not clearly demonstrated in biofilm conditions. When grown in condition permissive for IPS accumulation, biofilms of the glgA and pul mutants did not show decreased survival, compared to the parental strain. It is plausible that, within a biofilm, S. mutans can use alternative sources of energy (like the extracellular matrix) to compensate for the lack of IPS. To look at specific genes upregulated by sugar starvation, microarrays analysis was performed on S. mutans batch cultures. Some of the genes upregulated by starved, stationary phase bacteria, appeared to be organized in an operon, thought to encode components of the pyruvate dehydrogenase (PDH) complex. Northern Blot analysis showed that pdhD and the downstream genes, pdhA, pdhB and pdhC, form an operon that is transcribed predominantly in stationary phase. Inactivation of pdhD impaired survival of both batch cultures and biofilms. Analysis with fluorescent reporters revealed a distinct expression pattern for the pdh promoter, with less than 1% of stationary phase bacteria displaying pdh expression. When first detected, after one day of sugar starvation, expression was in individual bacteria. At later times, expressing bacteria were often in chains. The lengths of chains increased with time suggesting growth and division. It is likely that the pdh-expressing sub-population is able to persist for extend times in stationary phase. / Microbiology and Immunology

No description available.

1.55-µm high-speed modelocked semiconductor lasers are theoretically and experimentally studied for various coherent photonic system applications. The modelocked semiconductor lasers (MSLs) are designed with high-speed (>5 GHz) external cavity configurations utilizing monolithic two-section curved semiconductor optical amplifiers. By exploiting the saturable absorber section of the monolithic device, passive or hybrid mode-locking techniques are used to generate short optical pulses with broadband optical frequency combs. Laser frequency stability is improved by applying the Pound-Drever-Hall (PDH) frequency stabilization technique to the MSLs. The improved laser performance after the frequency stabilization (a frequency drifting of less than 350 MHz), is extensively studied with respect to the laser linewidth (~ 3 MHz), the relative intensity noise (RIN) (< -150 dB/Hz), as well as the modal RIN (~ 3 dB reduction). MSL to MSL, and tunable laser to MSL synchronization is demonstrated by using a dual-mode injection technique and a modulation sideband injection technique, respectively. Dynamic locking behavior and locking bandwidth are experimentally and theoretically studied. Stable laser synchronization between two MSLs is demonstrated with an injection seed power on the order of a few microwatt. Several coherent heterodyne detections based on the synchronized MSL systems are demonstrated for applications in microwave photonic links and ultra-dense wavelength division multiplexing (UD-WDM) system. In addition, efficient coherent homodyne balanced receivers based on synchronized MSLs are developed and demonstrated for a spectrally phase-encoded optical CDMA (SPE-OCDMA) system.

This research advances the current understanding of the carbonation reaction in porous materials by investigating pH changes during the hardening process of lime, the role of pore-water in the dissolution process of calcium hydroxide and the effects of pore size on precipitation of calcium carbonate solid phases. To achieve this, carbonation is studied within a thin film of an aqueous solution of calcium hydroxide, that simulates the conditions existing in porous media once most of the liquid water has evaporated. The research introduces novel approaches such as the use of specially manufactured micro-electrodes used to measure pH variations during the carbonation process. The effect of pore size on the solid phases precipitated by carbonation is investigated using a novel lime based material called nano-lime. Influence of pore-water on the hardening process of lime is studied in formulated lime using impedance spectroscopy: an electrochemical technique which is new in the study of lime based materials. Overall, results demonstrate that the micro-electrodes can operate reliably in very alkaline environments such as those produced by the dissolution of lime. Their potentiometric response, in fact, was found to be Nernstian up to pH 14. Furthermore, the electrode response proved to be sufficiently sensitive and reproducible to differentiate, on the basis of pH, between the formation of calcite and vaterite. It is likely that these micro-electrodes are currently the only analytical tools capable of monitoring high pHs in confined places and, for this reason, they can be considered highly valuable for the study of chemical processes involving very alkaline waters. The study on the role of pore-water in the hardening process of formulated lime has, instead, demonstrated the potential of impedance spectroscopy as a non-destructive technique for real time in situ monitoring of the reaction between lime and hydraulic additives.

In diploma thesis is theoretically described structure of PDH, SDH and multiplexing of PDH to SDH. Measurement of first level PDH and SDH is described too. A design of new laboratory network was based on theoretical information and the network was build. SDH nodes MSH11CP and other equipment in laboratory entourage are used in new laboratory network in a way that laboratory network is the most similar to real telecommunication network. Operation manual for SDH nodes type MSH11CP is described next in the thesis. New three laboratory tasks are described in the thesis. These tasks make use of design of new network and a reference of nodes operation manual. New three tasks are implemented in new laboratory network, in laboratory of transmission technologies. In these new laboratory tasks are possible to create a transmission path and measure this service, including settings and verification of a backup path.