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Guanylatkinase: Von einem aktiven Enzym zu einem inaktiven Multidomänen-Protein.Spangenberg, Oliver 02 May 2001 (has links)
No description available.
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Essays on multivariate volatility and dependence models for financial time seriesNoureldin, Diaa January 2011 (has links)
This thesis investigates the modelling and forecasting of multivariate volatility and dependence in financial time series. The first paper proposes a new model for forecasting changes in the term structure (TS) of interest rates. Using the level, slope and curvature factors of the dynamic Nelson-Siegel model, we build a time-varying copula model for the factor dynamics allowing for departure from the normality assumption typically adopted in TS models. To induce relative immunity to structural breaks, we model and forecast the factor changes and not the factor levels. Using US Treasury yields for the period 1986:3-2010:12, our in-sample analysis indicates model stability and we show statistically significant gains due to allowing for a time-varying dependence structure which permits joint extreme factor movements. Our out-of-sample analysis indicates the model's superior ability to forecast the conditional mean in terms of root mean square error reductions and directional forecast accuracy. The forecast gains are stronger during the recent financial crisis. We also conduct out-of-sample model evaluation based on conditional density forecasts. The second paper introduces a new class of multivariate volatility models that utilizes high-frequency data. We discuss the models' dynamics and highlight their differences from multivariate GARCH models. We also discuss their covariance targeting specification and provide closed-form formulas for multi-step forecasts. Estimation and inference strategies are outlined. Empirical results suggest that the HEAVY model outperforms the multivariate GARCH model out-of-sample, with the gains being particularly significant at short forecast horizons. Forecast gains are obtained for both forecast variances and correlations. The third paper introduces a new class of multivariate volatility models which is easy to estimate using covariance targeting. The key idea is to rotate the returns and then fit them using a BEKK model for the conditional covariance with the identity matrix as the covariance target. The extension to DCC type models is given, enriching this class. We focus primarily on diagonal BEKK and DCC models, and a related parameterisation which imposes common persistence on all elements of the conditional covariance matrix. Inference for these models is computationally attractive, and the asymptotics is standard. The techniques are illustrated using recent data on the S&P 500 ETF and some DJIA stocks, including comparisons to the related orthogonal GARCH models.
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Implication du récepteur aux cannabinoïdes CB2 dans le développement de la voie rétinothalamiqueDuff, Gabriel 08 1900 (has links)
Durant le développement du système visuel, les cellules ganglionnaires de la rétine
(CGRs) envoient des axones qui seront influencés par divers signaux guidant leur cône de croissance, permettant ainsi la navigation des axones vers leurs cibles terminales. Les endocannabinoïdes, des dérivés lipidiques activant les récepteurs aux cannabinoides (CB1 et CB2), sont présents de manière importante au cours du
développement. Nous avons démontré que le récepteur CB2 est exprimé à différents
points du tractus visuel durant le développement du hamster. L’injection d’agonistes et d’agonistes inverses pour le récepteur CB2 a modifié l’aire du cône de croissance et le nombre de filopodes présents à sa surface. De plus, l’injection d’un gradient d’agoniste du récepteur CB2 produit la répulsion du cône de croissance tandis qu’un analogue de l’AMPc (db-AMPc) produit son attraction. Les effets du récepteur CB2 sur le cône de croissance sont produits en modulant l’activité de la protéine kinase A(PKA), influençant la présence à la membrane cellulaire d’un récepteur à la nétrine-1 nommé Deleted in Colorectal Cancer (DCC). Notamment, pour que le récepteur CB2 puisse moduler le guidage du cône de croissance, la présence fonctionnelle du récepteur DCC est essentielle.. Suite à une injection intra-occulaire d’un agoniste inverse du récepteur CB2, nous avons remarqué une augmentation de la longueur des branches collatérales des axones rétiniens au niveau du LTN (noyau lateral terminal). Nous avons également remarqué une diminution de la ségrégation des projections ganglionnaires au niveau du dLGN, le noyau genouillé lateral dorsal, chez les animaux transgéniques cnr2-/-, ayant le gène codant pour le récepteur CB2 inactif. Nos données suggèrent l’implication des endocannabinoïdes et de leur récepteur CB2 dans la modulation des processus de navigation axonale et de ségrégation lors du
développement du système visuel. / Retinal projection navigation towards their visual targets is regulated by guidance
molecules and growth cone transduction mechanisms. Here, we show that cannabinoid receptor 2 (CB2R) is widely expressed throughout the visual pathway during development and in cultured retinal ganglion cells (RGCs) and cortical neurons. Both the number of filopodia and the surface area of the growth cone (GC) are modulated by CB2R activity in a PKA-dependant manner. Furthermore, DCC is required for CB2R induced morphological changes of the GC. CB2R agonists induce GC chemorepulsion. Treatments altering CB2R activity change retinal explants projections length. These effects are specific to CB2R as no changes were observed in cnr2 knockout mouse. A single intraocular injection of AM630 increases retinal projection branch length and aberrant projections were also observed. Moreover, we report defect in eye-specific segregation of retinal projections in the dLGN in cnr2-/- mice. These findings highlight the modulatory role of endocannabinoids and their CB2R during axon guidance.
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Analysis of Interdependencies among Central European Stock Markets / Analysis of Interdependencies among Central European Stock MarketsMašková, Jana January 2011 (has links)
The objective of the thesis is to examine interdependencies among the stock markets of the Czech Republic, Hungary, Poland and Germany in the period 2008-2010. Two main methods are applied in the analysis. The first method is based on the use of high-frequency data and consists in the computation of realized correlations, which are then modeled using the heterogeneous autoregressive (HAR) model. In addition, we employ realized bipower correlations, which should be robust to the presence of jumps in prices. The second method involves modeling of correlations by means of the Dynamic Conditional Correlation GARCH (DCC-GARCH) model, which is applied to daily data. The results indicate that when high-frequency data are used, the correlations are biased towards zero (the so-called "Epps effect"). We also find quite significant differences between the dynamics of the correlations from the DCC-GARCH models and those of the realized correlations. Finally, we show that accuracy of the forecasts of correlations can be improved by combining results obtained from different models (HAR models for realized correlations, HAR models for realized bipower correlations, DCC-GARCH models).
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Hidrólise e fermentação de papel em lisímetro para recuperação de compostos de interesse biotecnológico / Hydrolysis and fermentation of office paper in lysimeter for recovery of compounds of biotechnological interestLívia Silva Botta 26 August 2016 (has links)
Neste trabalho avaliou-se a produção de compostos de interesse biotecnológico potenciais vetores energéticos a partir de papel em lisímetros (20L), usando-se consórcio microbiano enriquecido do fluido de rúmen. Para tanto, foi realizado um delineamento composto central (DCC) para verificar a influência de três variáveis independentes na conversão de papel sulfite a hidrogênio e outros compostos orgânicos em lisímetro de bancada. As variáveis testadas foram massa de papel (X1: 500g, 750g e 1000g), teor de umidade papel (X2: 50%, 65% e 80%), e temperatura (X3:35°C, 45°C e 55°C). As respostas avaliadas no DCC foram produção de hidrogênio (Y1; mmol), ácido acético (Y2; mg/L), etanol (Y3; mg/L) e metanol (Y4; mg/L). Para o monitoramento dos lisímetros em relação à hidrólise e fermentação do papel, foram analisados biogás (H2, N2, CO2 e CH4) e a concentração de compostos no percolado, como açúcares totais, demanda química de oxigênio (DQO), ácidos orgânicos voláteis (AOVs) e álcoois. Além disso, monitorou-se o pH, alcalinidade e sólidos totais. Sequenciamento massivo do gene RNAr 16S via Plataforma Illumina foi usado para identificação dos micro-organismos do fluido de rúmen in natura, do consórcio enriquecido, e daqueles dos lisímetros R2, R5 e R9. Produção de hidrogênio só foi observada nos lisímetros R1 (25 mmol), R2 (35 mmol) e R5 (3 mmol), sendo os três com umidade inicial de 80%. Em R1 e R2, observou-se elevadas concentrações de ácido acético, de 21.500 e 17.000 mg/L, respectivamente, provavelmente devido à ocorrência de homoacetogênese. Sob temperatura termofílica, especialmente em R5, observou-se consumo de hidrogênio, e produção de etanol (2.300 mg/L) e metanol (5.600 mg/L). Na condição de 80% de umidade (R1, R2, R5, R6), verificou-se maiores percentuais de remoção de papel e atividade fermentativa mais acentuada, ao passo que abaixo de 80%, o desenvolvimento microbiano foi desfavorecido, independente da temperatura. Verificou-se consumo muito reduzido de papel e baixas concentrações de AOVs e álcoois para R3, R4, R7 e R8, todos com 50% umidade. Em R9 e R10, operados a 45 °C e 65% de umidade, também verificou-se produção atenuada de AOVs e álcoois, com ausência de hidrogênio. Por meio do DCC, observou-se efeito estatisticamente significativo da umidade do papel na produção de hidrogênio, ácido acético e etanol. Em relação à temperatura, verificou-se efeito positivo estatisticamente significativo na produção de hidrogênio e ácido acético. Por fim, para a massa de papel não se verificou nenhum efeito sobre as respostas analisadas. Os gêneros de bactérias mais abundantes foram: Prevotella no fluido de rúmen in natura (F.N.) Dysgonomonas no fluido de rúmen enriquecido e em R2 (35°C), Thermicanus em R5 (55°C) e Phaeospirillum em R9 (45ºC). A umidade foi o parâmetro mais determinante para promover a hidrólise e fermentação do papel; a temperatura foi a principal variável de influência na estrutura das comunidades microbianas dos lisímetros, confirmada pelas diferentes rotas metabólicas observadas sob temperatura mesofílica e termofílica; e os rendimentos de produção dos compostos não foram influenciados pela massa de papel adicionada aos lisímetros. / This study evaluated the production of compounds of biotechnological interest and potential energy vectors from office paper in lysimeters (20L), using a microbial consortium purified from rumen fluid. A central composite design (CCD) was performed to verify the influence of three independent variables on paper conversion to hydrogen and other organic compounds in bench lysimeter. The tested variables were: mass of paper (x1: 500g, 750g and 1000g), moisture content (x2: 50%, 65% and 80%), and incubation temperature (x3: 35°C, 45°C and 55°C). The dependent variables of CCD were production of hydrogen (Y1: mmol), acetic acid (Y2: mg/L), ethanol (Y3:mg/L) and metanol (Y4:mg/L). For monitoring the lysimeters in relation to paper hydrolysis and fermentation, analyses of biogas (H2, N2, CO2 and CH4) and the organic compounds' concentrations in the leachate, such as, total sugars, chemical oxygem demand, volatile organic acids (VOA's) and alcohols were conducted during operation. Alcalinity, pH and total solids content of the leachate were also monitored. Massive sequencing of rRNA 16S (Illumina) was carried out for identification of the microorganisms of the in natura rumen fluid, the purified consortium, and those collected from lysimeters R2, R5 and R9. Hydrogen production was detected only in lysimeters R1 (25 mmol), R2 (35 mmol) and R5 (3 mmol), all of them operated with 80% of moisture content. In R1 and R2, high concentrations of acetic acid, of 21.500 and 17.000, respectively, were due to the likely occurrence of homoacetogenesis. Under thermophilic temperature, especially R5, the hydrogen production was detected in low quantity, and the highlight was the production of ethanol and methanol, with concentrations around 2.300 and 5.600 mg/L, respectively. At 80% moisture condition (R1, R2, R5, R6), high percentages of paper removal and sharp fermentative activity were observed. However, at lower moisture conditions, the microbial growth was unfavored, independent of the temperature. Low paper consumption and reduced concentrations of OVA's and alcohols were detected in R3, R4, R7 and R8, all of them operated with 50% of moisture content. In R9 and R10, operated at 45°C and 65% of moisture, there was also attenuated production of VOA\'s and alcohols, with absence of hydrogen. According to CCD statistical analysis, paper moisture content had positive effect statistically significative on hydrogen, acetic acid and etanol production. The temperature had positive effect on hydrogen and acetic acid production. And the mass of paper dit not have effect statistically significative for any dependent variables. The most abundant bacterial genus was: Prevotella in the in natura rumen fluid (F.N.) Dysgonomonas in the purified consortium and R2 (35 oC), Thermicanus in R5 (55°C) and Phaeospirillum in R9 (45° C). In conclusion, moisture content was the main parameter to promote paper hydrolysis and fermentation; temperature was the principal variable that influenced the structure of microbial community, confirmed by the different metabolic route observed under mesophilic and thermophilic conditions; and the production yields of the compounds were not influenced by the mass of paper added to the lysimeters.
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Hidrólise e fermentação de papel em lisímetro para recuperação de compostos de interesse biotecnológico / Hydrolysis and fermentation of office paper in lysimeter for recovery of compounds of biotechnological interestBotta, Lívia Silva 26 August 2016 (has links)
Neste trabalho avaliou-se a produção de compostos de interesse biotecnológico potenciais vetores energéticos a partir de papel em lisímetros (20L), usando-se consórcio microbiano enriquecido do fluido de rúmen. Para tanto, foi realizado um delineamento composto central (DCC) para verificar a influência de três variáveis independentes na conversão de papel sulfite a hidrogênio e outros compostos orgânicos em lisímetro de bancada. As variáveis testadas foram massa de papel (X1: 500g, 750g e 1000g), teor de umidade papel (X2: 50%, 65% e 80%), e temperatura (X3:35°C, 45°C e 55°C). As respostas avaliadas no DCC foram produção de hidrogênio (Y1; mmol), ácido acético (Y2; mg/L), etanol (Y3; mg/L) e metanol (Y4; mg/L). Para o monitoramento dos lisímetros em relação à hidrólise e fermentação do papel, foram analisados biogás (H2, N2, CO2 e CH4) e a concentração de compostos no percolado, como açúcares totais, demanda química de oxigênio (DQO), ácidos orgânicos voláteis (AOVs) e álcoois. Além disso, monitorou-se o pH, alcalinidade e sólidos totais. Sequenciamento massivo do gene RNAr 16S via Plataforma Illumina foi usado para identificação dos micro-organismos do fluido de rúmen in natura, do consórcio enriquecido, e daqueles dos lisímetros R2, R5 e R9. Produção de hidrogênio só foi observada nos lisímetros R1 (25 mmol), R2 (35 mmol) e R5 (3 mmol), sendo os três com umidade inicial de 80%. Em R1 e R2, observou-se elevadas concentrações de ácido acético, de 21.500 e 17.000 mg/L, respectivamente, provavelmente devido à ocorrência de homoacetogênese. Sob temperatura termofílica, especialmente em R5, observou-se consumo de hidrogênio, e produção de etanol (2.300 mg/L) e metanol (5.600 mg/L). Na condição de 80% de umidade (R1, R2, R5, R6), verificou-se maiores percentuais de remoção de papel e atividade fermentativa mais acentuada, ao passo que abaixo de 80%, o desenvolvimento microbiano foi desfavorecido, independente da temperatura. Verificou-se consumo muito reduzido de papel e baixas concentrações de AOVs e álcoois para R3, R4, R7 e R8, todos com 50% umidade. Em R9 e R10, operados a 45 °C e 65% de umidade, também verificou-se produção atenuada de AOVs e álcoois, com ausência de hidrogênio. Por meio do DCC, observou-se efeito estatisticamente significativo da umidade do papel na produção de hidrogênio, ácido acético e etanol. Em relação à temperatura, verificou-se efeito positivo estatisticamente significativo na produção de hidrogênio e ácido acético. Por fim, para a massa de papel não se verificou nenhum efeito sobre as respostas analisadas. Os gêneros de bactérias mais abundantes foram: Prevotella no fluido de rúmen in natura (F.N.) Dysgonomonas no fluido de rúmen enriquecido e em R2 (35°C), Thermicanus em R5 (55°C) e Phaeospirillum em R9 (45ºC). A umidade foi o parâmetro mais determinante para promover a hidrólise e fermentação do papel; a temperatura foi a principal variável de influência na estrutura das comunidades microbianas dos lisímetros, confirmada pelas diferentes rotas metabólicas observadas sob temperatura mesofílica e termofílica; e os rendimentos de produção dos compostos não foram influenciados pela massa de papel adicionada aos lisímetros. / This study evaluated the production of compounds of biotechnological interest and potential energy vectors from office paper in lysimeters (20L), using a microbial consortium purified from rumen fluid. A central composite design (CCD) was performed to verify the influence of three independent variables on paper conversion to hydrogen and other organic compounds in bench lysimeter. The tested variables were: mass of paper (x1: 500g, 750g and 1000g), moisture content (x2: 50%, 65% and 80%), and incubation temperature (x3: 35°C, 45°C and 55°C). The dependent variables of CCD were production of hydrogen (Y1: mmol), acetic acid (Y2: mg/L), ethanol (Y3:mg/L) and metanol (Y4:mg/L). For monitoring the lysimeters in relation to paper hydrolysis and fermentation, analyses of biogas (H2, N2, CO2 and CH4) and the organic compounds' concentrations in the leachate, such as, total sugars, chemical oxygem demand, volatile organic acids (VOA's) and alcohols were conducted during operation. Alcalinity, pH and total solids content of the leachate were also monitored. Massive sequencing of rRNA 16S (Illumina) was carried out for identification of the microorganisms of the in natura rumen fluid, the purified consortium, and those collected from lysimeters R2, R5 and R9. Hydrogen production was detected only in lysimeters R1 (25 mmol), R2 (35 mmol) and R5 (3 mmol), all of them operated with 80% of moisture content. In R1 and R2, high concentrations of acetic acid, of 21.500 and 17.000, respectively, were due to the likely occurrence of homoacetogenesis. Under thermophilic temperature, especially R5, the hydrogen production was detected in low quantity, and the highlight was the production of ethanol and methanol, with concentrations around 2.300 and 5.600 mg/L, respectively. At 80% moisture condition (R1, R2, R5, R6), high percentages of paper removal and sharp fermentative activity were observed. However, at lower moisture conditions, the microbial growth was unfavored, independent of the temperature. Low paper consumption and reduced concentrations of OVA's and alcohols were detected in R3, R4, R7 and R8, all of them operated with 50% of moisture content. In R9 and R10, operated at 45°C and 65% of moisture, there was also attenuated production of VOA\'s and alcohols, with absence of hydrogen. According to CCD statistical analysis, paper moisture content had positive effect statistically significative on hydrogen, acetic acid and etanol production. The temperature had positive effect on hydrogen and acetic acid production. And the mass of paper dit not have effect statistically significative for any dependent variables. The most abundant bacterial genus was: Prevotella in the in natura rumen fluid (F.N.) Dysgonomonas in the purified consortium and R2 (35 oC), Thermicanus in R5 (55°C) and Phaeospirillum in R9 (45° C). In conclusion, moisture content was the main parameter to promote paper hydrolysis and fermentation; temperature was the principal variable that influenced the structure of microbial community, confirmed by the different metabolic route observed under mesophilic and thermophilic conditions; and the production yields of the compounds were not influenced by the mass of paper added to the lysimeters.
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Implication du récepteur aux cannabinoïdes CB2 dans le développement de la voie rétinothalamiqueDuff, Gabriel 08 1900 (has links)
Durant le développement du système visuel, les cellules ganglionnaires de la rétine
(CGRs) envoient des axones qui seront influencés par divers signaux guidant leur cône de croissance, permettant ainsi la navigation des axones vers leurs cibles terminales. Les endocannabinoïdes, des dérivés lipidiques activant les récepteurs aux cannabinoides (CB1 et CB2), sont présents de manière importante au cours du
développement. Nous avons démontré que le récepteur CB2 est exprimé à différents
points du tractus visuel durant le développement du hamster. L’injection d’agonistes et d’agonistes inverses pour le récepteur CB2 a modifié l’aire du cône de croissance et le nombre de filopodes présents à sa surface. De plus, l’injection d’un gradient d’agoniste du récepteur CB2 produit la répulsion du cône de croissance tandis qu’un analogue de l’AMPc (db-AMPc) produit son attraction. Les effets du récepteur CB2 sur le cône de croissance sont produits en modulant l’activité de la protéine kinase A(PKA), influençant la présence à la membrane cellulaire d’un récepteur à la nétrine-1 nommé Deleted in Colorectal Cancer (DCC). Notamment, pour que le récepteur CB2 puisse moduler le guidage du cône de croissance, la présence fonctionnelle du récepteur DCC est essentielle.. Suite à une injection intra-occulaire d’un agoniste inverse du récepteur CB2, nous avons remarqué une augmentation de la longueur des branches collatérales des axones rétiniens au niveau du LTN (noyau lateral terminal). Nous avons également remarqué une diminution de la ségrégation des projections ganglionnaires au niveau du dLGN, le noyau genouillé lateral dorsal, chez les animaux transgéniques cnr2-/-, ayant le gène codant pour le récepteur CB2 inactif. Nos données suggèrent l’implication des endocannabinoïdes et de leur récepteur CB2 dans la modulation des processus de navigation axonale et de ségrégation lors du
développement du système visuel. / Retinal projection navigation towards their visual targets is regulated by guidance
molecules and growth cone transduction mechanisms. Here, we show that cannabinoid receptor 2 (CB2R) is widely expressed throughout the visual pathway during development and in cultured retinal ganglion cells (RGCs) and cortical neurons. Both the number of filopodia and the surface area of the growth cone (GC) are modulated by CB2R activity in a PKA-dependant manner. Furthermore, DCC is required for CB2R induced morphological changes of the GC. CB2R agonists induce GC chemorepulsion. Treatments altering CB2R activity change retinal explants projections length. These effects are specific to CB2R as no changes were observed in cnr2 knockout mouse. A single intraocular injection of AM630 increases retinal projection branch length and aberrant projections were also observed. Moreover, we report defect in eye-specific segregation of retinal projections in the dLGN in cnr2-/- mice. These findings highlight the modulatory role of endocannabinoids and their CB2R during axon guidance.
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匯率轉嫁之時間變動特性-台灣實證研究 / Time-varying nature of exchange rate pass-through for Taiwan沈睿宸, Shen, Juei Chen Unknown Date (has links)
過去實證研究顯示,匯率轉嫁程度並非一成不變,而是具有隨時間變動的特性。因此,有別於過去文獻大多採用滾動相關係數,本文則是使用Engle(2002)提出的動態條件相關係數模型,估計台灣於1982年至2014年間匯率變動與進口價格變動間的動態條件相關係數;並以其做為匯率轉嫁的代理變數,進而探討台灣匯率轉嫁的時間變動趨勢。我們的實證結果顯示,不論是用滾動相關係數還是動態條件相關係數,台灣的匯率轉嫁都明顯具有隨時間變動的特性。雖然5年期與10年期的滾動相關係數均在1997年前後分別呈現上升與下降的趨勢,動態條件相關係數則無類似的現象。然而,由於滾動相關係數容易受到滾動視窗樣本大小或滾動視窗有無包含極端值的影響,使得此方法較無法看出匯率轉嫁變動的準確時間點,而動態條件相關係數模型則可避免此問題。此外,本文實證發現,通膨環境與匯率波動是造成台灣匯率轉嫁隨時間變動的主要因子,對匯率轉嫁皆有顯著的正向影響。在排除1986年匯率轉嫁與進口滲透率呈現短暫負向關係的資料後,進口滲透率與匯率轉嫁的正向關係變為顯著,而進口滲透率也成為影響匯率轉嫁的原因之一。 / According to past empirical studies, it is believed that exchange rate pass -through (ERPT) has the time-varying nature. In this paper, we apply the Dynamic Conditional Correlation (DCC) model of Engle (2002), rather than the rolling correlation coefficient prevalently used by other studies, to analyze the time trend of ERPT for Taiwan. We estimate the dynamic condition correlation between the changes of exchange rate and the changes of import price using monthly data from 1982 to 2014 and use this correlation as a proxy for the degree of ERPT. Our empirical results show that ERPT for Taiwan, whether measured by the DCC or the rolling correlation coefficient, has a significant time- varying nature. In addition, both 5-year and 10-year window rolling correlation coefficient increase before 1997 and decline after 1997, which does not show in the DCC. However, the rolling correlation coefficient does not provide precise timings in the changes in ERPT, because of the dependence on the size of windows and whether or not outliers exist in the window. In contrast, the DCC does not have this kind of problem. Another important empirical result of this paper is that the inflation environment and the exchange rate volatility are main factors which explain the time-varying ERPT, and both of them have positive relation with ERPT. Moreover, the import penetration becomes positively significant after excluding data which shows temporary negative impact of the import penetration on ERPT in 1986.
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Fully Integrated CMOS Transmitter and Power Amplifier for Software-Defined Radios and Cognitive RadiosRaja, Immanuel January 2017 (has links) (PDF)
Software Defined Radios (SDRs) and Cognitive Radios (CRs) pave the way for next-generation radio technology. They promise versatility, flexibility and cognition which can revolutionize communications systems. However they present greater challenges to the design of radio frequency (RF) front-ends. RF front-ends for the radios in use today are narrow-band in their frequency response and are optimized and tuned to the carrier frequency of interest. SDRs and CRs demand front-ends which are versatile, configurable, tunable and be capable of transmitting and receiving signals with different bandwidths and modulation schemes. Integrating power amplifiers (PAs) with transmitters in CMOS has many advantages and challenges. This thesis deals with the design of an RF transmitter front-end for SDRs and CRs in CMOS.
The thesis begins with an introduction to SDRs and the requirements they place on transmitters and the challenges involved in designing them in CMOS. After a brief overview of the existing techniques, the proposed architecture is presented and explained. A digitally intensive transmitter solution is proposed. The transmitter covers a wide frequency range of 750 MHz to 2.5 GHz. The inputs to the proposed transmitter are in-phase and quadrature (I & Q) data bit streams. Multiple stages of up-sampling and filtering are used to remove all spurs in the spectrum such that only the harmonics of the carrier remain.
Differential rail-to-rail quadrature clocks are generated from a continuous wave signal at twice the carrier frequency. The clocks are corrected for their duty cycle and quadrature impairments.
The heart of the transmitter is an integrated reconfigurable CMOS power amplifier (PA). A methodology to design reconfigurable Class E PAs with a series fixed inductor has been presented. A CMOS power amplifier that can span a wide frequency range with sufficient output power and efficiency, supporting varying envelope complex modulation signals, with good linearity has been designed. Digital pre-distortion (DPD) is used to linearize the PA.
The full transmitter and the clock correction blocks have been designed and fabricated in a commercial 130-nm CMOS process and experimentally characterized. The PA delivers a maximum power of 13 dBm with an efficiency of 27% at 1 GHz. While transmitting a 16-QAM signal at 1 GHz, the measured EVM is 4%. It delivers a maximum power of around 11-13 dBm from 750 MHz to 1.5 GHz and up to 6.5 dBm of power till 2.5 GHz.
Comparing the proposed system with recently published literature, it can be seen that the proposed design is one of the very few transmitters which has an integrated matching network, tunable across the frequency range. The proposed PA produces the highest output power and with largest efficiency for systems with on-chip output networks.
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Acute Toxicity and Immunotoxicity Testing of Total Petroleum Hydrocarbons in Aquatic and Terrestrial OrganismsHandy, Andrea Renee 31 July 2007 (has links)
No description available.
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