Submitted by (edna.saturno@ufrpe.br) on 2017-02-09T14:50:18Z No. of bitstreams: 1 Diogo Bessa Neves Spanghero.pdf: 353251 bytes, checksum: 242874c51488bd360e78b53019a7ba2d (MD5) / Made available in DSpace on 2017-02-09T14:50:18Z (GMT). No. of bitstreams: 1 Diogo Bessa Neves Spanghero.pdf: 353251 bytes, checksum: 242874c51488bd360e78b53019a7ba2d (MD5) Previous issue date: 2008-02-21 / The marine shrimp Litopenaeus vannamei can be cultured in waters of different salinities,therefore they tolerate an ample band of salinities (0,5-60). Of this form, the objective of this present work was to compare the production data, of this crustacean, when cultured in freshwater or salty water, using mathematical models. The models, to relate the variables of management and of production, had been formulated on the basis of a data base with 278 cultures. To estimate the models parameters, it was used technique of the squared minimums.The variable selection was carried through the process of "Stepwise" associated to the Box and Cox’s transformation. The adequacy of the equations and the normality estimated, for the errors, had been analyzed on the basis of the variance analysis, in the Durbin-Watson statistics, on the residue analysis and normality test. In all the formulated equations the management variables, culture in salty water (CAS) was selected, evidencing significant difference (p<0,05) between these culture systems. / O camarão marinho Litopenaeus vannamei pode ser cultivado em águas de diferentes salinidades, pois toleram uma ampla faixa de salinidades (0,5-60). Desta forma, objetivou-se com o presente trabalho comparar os dados de produção, desse crustáceo, quando cultivados em água doce ou em água salgada, utilizando-se modelos matemáticos. Os modelos, para relacionar as variáveis de manejo e as de produção, foram formulados com base em um banco de dados com 278 cultivos. Para estimar os parâmetros dos modelos, utilizou-se a técnica dos mínimos quadrados. A seleção das variáveis foi realizada com o processo de “Stepwise” associado à transformação de Box e Cox. A adequação das equações e os pressupostos de normalidade, para os erros, foram analisados com base na análise de variância, na estatística de Durbin-Watson, na análise de resíduo e teste de normalidade. Em todas as equações formuladas a variável de manejo, cultivo em água salgada (CAS) foi selecionada, evidenciando diferença significativa (p<0,05) entre esses sistemas de cultivo.

<p>Kvicksilverutsläppen har på senare år minskat i omfattning men utsläpp sker fortfarande och det finns ett stort lager i naturen. Oorganiskt kvicksilver är relativt ofarligt för levande organismer, men i akvatiska miljöer kan sulfatreducerande bakterier under syrefria förhållanden omvandla oorganiskt kvicksilver till den betydligt mer skadliga formen metylkvicksilver, meHg, som även är mer biotillgängligt än oorganiskt kvicksilver. Kvicksilver biomagnifieras uppåt i trofinivåerna, från att vara lägst halter i plankton och bottenfauna till att vara högst halter i rovfiskar. Kvicksilver ackumuleras även i fiskars muskelvävnad vilket innebär att yngre fiskar har lägre Hg-halter än gamla och stora individer. På grund av detta finns kostråd framtagna av Livsmedelsverket. Saluförd abborre, liksom ett flertal andra fiskarter, får inneha maximalt 0,5 mg Hg/kg fiskmuskel (färskvikt) och för gädda är gränsen satt till 1 mg Hg/kg fiskmuskel (färskvikt). Organiskt kvicksilver kan påverka foster negativt, och därför bör kvinnor i fertil ålder i största möjliga mån undvika kvicksilverrik fisk.</p><p> </p><p>Examensarbetet syftar till att belysa kvicksilversituationen i Stockholms skärgård för stationär kustfisk. Information har samlats in dels genom en litteraturstudie och dels genom fältundersökningar utförda av IVL Svenska Miljöinstitutet. Genom statistisk analys och stegvis multipel regression visades att kvicksilverhalten i sediment, vattnets klorofyllhalt och områdets vattenvolym bidrog med förklaringsgrad till halten Hg i fisk. Utifrån de mest signifikanta förklarande variablerna togs en statistisk modell fram i syfte att kunna prediktera teoretiska kvicksilverhalter i fisk. Olika modellkombinationer testades och utgående från en modellvalidering valdes den bästa modellen ut. Dess förklaringsgrad är 81 % där kvicksilverhalten i sediment är modellens enda variabel.</p><p> </p><p>Kvicksilversituationen i Stockholms skärgårds kustområden visades grafiskt med hjälp av interpolerade GIS-kartor. Samma områdesavgränsningar användes som i SMHI:s havsområderegister. Det visades att situationen över lag är relativt god, med undantag för de centrala delarna av Stockholm och på så vis kan Stockholm ses som en förorenande punktkälla.</p> / <p>Mercury emissions have been reduced in recent years but the discharges still exist and there exist a great mercury stock out in the nature. Inorganic mercury is relatively harmless for living organisms but during shortage of oxygen, sulphur reducing bacteria can transform inorganic mercury into the considerable more toxic substance methyl mercury, meHg, that are more bio available than inorganic mercury. Mercury biomagnify upwards the trophic levels, where the lowest content exists in algae and sediment living fauna and the highest content exist in predator fishes. Mercury also accumulates in fishes muscle tissue, meaning that young fishes have lower mercury content than old and big individuals. Food advices from the Swedish food agency exist because of this. Perch offered for sale are allowed to have a content of maximum 0.5 mg Hg/kg fish muscle (wet weight) and for pike the upper boundary content is 1 mg Hg/kg fish muscle (wet weight). Inorganic mercury can affect foetus negatively, and therefore women in fertile age should avoid fish with high mercury content for as long as possible.</p><p> </p><p>The aim of this exam work is to illustrate the mercury situation in the archipelago of Stockholm regarding stationary coast fish. Information was collected through a literature study and by field examines done by IVL Swedish Environmental Research Institute Ltd. Through statistical analyses and stepwise multiple regression it was shown that the mercury content in sediment, chlorophyll and the water volume of the area contributed by statistical explanation to the mercury concentration in fish. On the basis of the most significant variables a statistical model was created, with the purpose of predicting theoretical mercury contents in fish. Different model combinations were tested and by a model validation the best model were chosen. Its statistical explanation is 81 % were the mercury content in the sediment is the only input variable to the model.</p><p> </p><p>The mercury situation in the Stockholm archipelago was presented graphically by interpolated maps created with GIS. The same area boundary as SMHI’s maritime registry was used. It was shown that the situation in general is relatively good, with the exception of the central parts of Stockholm. Because of this Stockholm can be seen as a polluting point source.</p>

Tree rings have been used as a proxy in reconstructing streamflow in the western U.S. for many years, but few reconstructions have been attempted in the eastern United States. Clear limitations exist for streamflow reconstructions in the eastern U.S. compared to the western U.S., but value can be established as demonstrated in this research. The primary goal of this research was to reconstruct streamflow using data from five headwater gages in the Appalachian Mountains of North Carolina. These gages are located on the Valley River, the Oconaluftee River, the Nantahala River, the Little Tennessee River, and the Watauga River. Tree-ring chronologies were used to reconstruct streamflow. Tree-ring chronology predictors were selected using a seasonal correlation analysis. Seasonal correlation analysis revealed May-June-July (MJJ) streamflow variability being highly correlated with tree-ring chronologies in the study region and vicinity. Stepwise linear regression methods were used to reconstruct MJJ streamflow. The reconstructions for the Valley, Oconaluftee, and Nantahala Rivers were considered acceptable reconstructions because the models explained approximately 50% of the total variance in historic period MJJ streamflow records. These three streamflow reconstruction models have predictive skill indicated by a positive reduction of error (RE) values. The root mean square error (RMSE) statistic was 11.5 million cubic meters (MCM) for the Valley River (26% of the mean reconstructed MJJ flow), 15.9 MCM for the Oconaluftee River (16% of the mean reconstructed MJJ flow), and 8.2 MCM for the Nantahala River (20% of the mean reconstructed MJJ flow). Analysis of the reconstructed streamflow data for these three rivers revealed low flow periods from 1710 to 1712 at all three sites. The research presented here shows the potential benefit of using tree-ring chronologies to reconstruct streamflow in the Tennessee Valley region by demonstrating the ability of proxy-based reconstructions to provide useful data beyond the instrumental record. These useful data include identification of extreme wet or dry periods and oscillations in the historical reconstructions that are not visible in the instrumental data.

The Diels-Alder reaction is one of the most powerful synthetic tools in organic chemistry, and asymmetric Diels-Alder catalysis allows for rapid construction of chiral carbon scaffolds. For this reason, considerable effort has been invested in developing efficient and stereoselective organo- and biocatalysts. However, Diels-Alder is a virtually unknown reaction in Nature, and to engineer an enzyme into a Diels-Alderase is therefore a challenging task. Despite several successful designs of catalytic antibodies since the 1980’s, their catalytic activities have remained low, and no true artificial ’Diels-Alderase’ enzyme was reported before 2010. In this thesis, we employ state-of-the-art computational tools to study the mechanism of organocatalyzed Diels-Alder in detail, and to redesign existing enzymes into intermolecular Diels-Alder catalysts. Papers I–IV explore the mechanistic variations when employing increasingly activated reactants and the effect of catalysis. In particular, the relation between the traditionally presumed concerted mechanism and a stepwise pathway, forming one bond at a time, is probed. Papers V–X deal with enzyme design and the computational aspects of predicting catalytic activity. Four novel, computationally designed Diels-Alderase candidates are presented in Papers VI–IX. In Paper X, a new parameterization of the Linear Interaction Energy model for predicting protein-ligand affinities is presented. A general finding in this thesis is that it is difficult to attain large transition state stabilization effects solely by hydrogen bond catalysis. In addition, water (the preferred solvent of enzymes) is well-known for catalyzing Diels- Alder by itself. Therefore, an efficient Diels-Alderase must rely on large binding affinities for the two substrates and preferential binding conformations close to the transition state geometry. In Papers VI–VIII, we co-designed the enzyme active site and substrates in order to achieve the best possible complementarity and maximize binding affinity and pre-organization. Even so, catalysis is limited by the maximum possible stabilization offered by hydrogen bonds, and by the inherently large energy barrier associated with the [4+2] cycloaddition. The stepwise Diels-Alder pathway, proceeding via a zwitterionic intermediate, may offer a productive alternative for enzyme catalysis, since an enzyme active site may be more differentiated towards stabilizing the high-energy states than for the standard mechanism. In Papers I and III, it is demonstrated that a hydrogen bond donor catalyst provides more stabilization of transition states having pronounced charge-transfer character, which shifts the preference towards a stepwise mechanism. Another alternative, explored in Paper IX, is to use an α,β -unsaturated ketone as a ’pro-diene’, and let the enzyme generate the diene in situ by general acid/base catalysis. The results show that the potential reduction in the reaction barrier with such a mechanism is much larger than for conventional Diels-Alder. Moreover, an acid/base-mediated pathway is a better mimic of how natural enzymes function, since remarkably few catalyze their reactions solely by non-covalent interactions. / <p>QC 20120903</p>

Ensembles methods such as AdaBoost, Bagging and Random Forest have attracted much attention in the statistical learning community in the last 15 years. Zhu and Chipman (2006) proposed the idea of using ensembles for variable selection. Their implementation used a parallel genetic algorithm (PGA). In this thesis, I propose a stochastic stepwise ensemble for variable selection, which improves upon PGA. Traditional stepwise regression (Efroymson 1960) combines forward and backward selection. One step of forward selection is followed by one step of backward selection. In the forward step, each variable other than those already included is added to the current model, one at a time, and the one that can best improve the objective function is retained. In the backward step, each variable already included is deleted from the current model, one at a time, and the one that can best improve the objective function is discarded. The algorithm continues until no improvement can be made by either the forward or the backward step. Instead of adding or deleting one variable at a time, Stochastic Stepwise Algorithm (STST) adds or deletes a group of variables at a time, where the group size is randomly decided. In traditional stepwise, the group size is one and each candidate variable is assessed. When the group size is larger than one, as is often the case for STST, the total number of variable groups can be quite large. Instead of evaluating all possible groups, only a few randomly selected groups are assessed and the best one is chosen. From a methodological point of view, the improvement of STST ensemble over PGA is due to the use of a more structured way to construct the ensemble; this allows us to better control over the strength-diversity tradeoff established by Breiman (2001). In fact, there is no mechanism to control this fundamental tradeoff in PGA. Empirically, the improvement is most prominent when a true variable in the model has a relatively small coefficient (relative to other true variables). I show empirically that PGA has a much higher probability of missing that variable.

Kvicksilverutsläppen har på senare år minskat i omfattning men utsläpp sker fortfarande och det finns ett stort lager i naturen. Oorganiskt kvicksilver är relativt ofarligt för levande organismer, men i akvatiska miljöer kan sulfatreducerande bakterier under syrefria förhållanden omvandla oorganiskt kvicksilver till den betydligt mer skadliga formen metylkvicksilver, meHg, som även är mer biotillgängligt än oorganiskt kvicksilver. Kvicksilver biomagnifieras uppåt i trofinivåerna, från att vara lägst halter i plankton och bottenfauna till att vara högst halter i rovfiskar. Kvicksilver ackumuleras även i fiskars muskelvävnad vilket innebär att yngre fiskar har lägre Hg-halter än gamla och stora individer. På grund av detta finns kostråd framtagna av Livsmedelsverket. Saluförd abborre, liksom ett flertal andra fiskarter, får inneha maximalt 0,5 mg Hg/kg fiskmuskel (färskvikt) och för gädda är gränsen satt till 1 mg Hg/kg fiskmuskel (färskvikt). Organiskt kvicksilver kan påverka foster negativt, och därför bör kvinnor i fertil ålder i största möjliga mån undvika kvicksilverrik fisk.   Examensarbetet syftar till att belysa kvicksilversituationen i Stockholms skärgård för stationär kustfisk. Information har samlats in dels genom en litteraturstudie och dels genom fältundersökningar utförda av IVL Svenska Miljöinstitutet. Genom statistisk analys och stegvis multipel regression visades att kvicksilverhalten i sediment, vattnets klorofyllhalt och områdets vattenvolym bidrog med förklaringsgrad till halten Hg i fisk. Utifrån de mest signifikanta förklarande variablerna togs en statistisk modell fram i syfte att kunna prediktera teoretiska kvicksilverhalter i fisk. Olika modellkombinationer testades och utgående från en modellvalidering valdes den bästa modellen ut. Dess förklaringsgrad är 81 % där kvicksilverhalten i sediment är modellens enda variabel.   Kvicksilversituationen i Stockholms skärgårds kustområden visades grafiskt med hjälp av interpolerade GIS-kartor. Samma områdesavgränsningar användes som i SMHI:s havsområderegister. Det visades att situationen över lag är relativt god, med undantag för de centrala delarna av Stockholm och på så vis kan Stockholm ses som en förorenande punktkälla. / Mercury emissions have been reduced in recent years but the discharges still exist and there exist a great mercury stock out in the nature. Inorganic mercury is relatively harmless for living organisms but during shortage of oxygen, sulphur reducing bacteria can transform inorganic mercury into the considerable more toxic substance methyl mercury, meHg, that are more bio available than inorganic mercury. Mercury biomagnify upwards the trophic levels, where the lowest content exists in algae and sediment living fauna and the highest content exist in predator fishes. Mercury also accumulates in fishes muscle tissue, meaning that young fishes have lower mercury content than old and big individuals. Food advices from the Swedish food agency exist because of this. Perch offered for sale are allowed to have a content of maximum 0.5 mg Hg/kg fish muscle (wet weight) and for pike the upper boundary content is 1 mg Hg/kg fish muscle (wet weight). Inorganic mercury can affect foetus negatively, and therefore women in fertile age should avoid fish with high mercury content for as long as possible.   The aim of this exam work is to illustrate the mercury situation in the archipelago of Stockholm regarding stationary coast fish. Information was collected through a literature study and by field examines done by IVL Swedish Environmental Research Institute Ltd. Through statistical analyses and stepwise multiple regression it was shown that the mercury content in sediment, chlorophyll and the water volume of the area contributed by statistical explanation to the mercury concentration in fish. On the basis of the most significant variables a statistical model was created, with the purpose of predicting theoretical mercury contents in fish. Different model combinations were tested and by a model validation the best model were chosen. Its statistical explanation is 81 % were the mercury content in the sediment is the only input variable to the model.   The mercury situation in the Stockholm archipelago was presented graphically by interpolated maps created with GIS. The same area boundary as SMHI’s maritime registry was used. It was shown that the situation in general is relatively good, with the exception of the central parts of Stockholm. Because of this Stockholm can be seen as a polluting point source.

Ensembles methods such as AdaBoost, Bagging and Random Forest have attracted much attention in the statistical learning community in the last 15 years. Zhu and Chipman (2006) proposed the idea of using ensembles for variable selection. Their implementation used a parallel genetic algorithm (PGA). In this thesis, I propose a stochastic stepwise ensemble for variable selection, which improves upon PGA. Traditional stepwise regression (Efroymson 1960) combines forward and backward selection. One step of forward selection is followed by one step of backward selection. In the forward step, each variable other than those already included is added to the current model, one at a time, and the one that can best improve the objective function is retained. In the backward step, each variable already included is deleted from the current model, one at a time, and the one that can best improve the objective function is discarded. The algorithm continues until no improvement can be made by either the forward or the backward step. Instead of adding or deleting one variable at a time, Stochastic Stepwise Algorithm (STST) adds or deletes a group of variables at a time, where the group size is randomly decided. In traditional stepwise, the group size is one and each candidate variable is assessed. When the group size is larger than one, as is often the case for STST, the total number of variable groups can be quite large. Instead of evaluating all possible groups, only a few randomly selected groups are assessed and the best one is chosen. From a methodological point of view, the improvement of STST ensemble over PGA is due to the use of a more structured way to construct the ensemble; this allows us to better control over the strength-diversity tradeoff established by Breiman (2001). In fact, there is no mechanism to control this fundamental tradeoff in PGA. Empirically, the improvement is most prominent when a true variable in the model has a relatively small coefficient (relative to other true variables). I show empirically that PGA has a much higher probability of missing that variable.

In order to reduce default risk, financial institutions have been investigating into credit ratings of companies, which they want to give credit to. This research tries to give a method for financial institutions to differentiate between default and normal company with financial ratios, which is already announced in their seasonal financial reports. The samples are abstracted from security markets, and restricted to building companies. With Discriminant analysis and Logistic regression models, financial institutions can estimate what company may become into default situation and others stay in good condition. According to this research, financial ratios that can be used to discriminate between default and normal companies are: net worth ratio and short-turn borrowing/liquid asset and asset turnover and gross profit margin. It can also be described with asset turnover and gross profit margin if default risk is been estimated.

Under path dependent consideration, we discuss vulnerable option pricing problem. Two pricing models are proposed: Model(1) use stepwise regression and Monte Carlo simulation, and Model(2) is based on multi-level regression method. Since the option price was approximated by quadratic surface at each time point in Model(1), large mean square errors are induced. Therefore, we further propose a stepwise subset regression method to improve Model(1) approach. At present, this proposed method can compute the option price accurately for no credit risk options. For Model(2), we utilize a multi-level regression method to price vulnerable options, and simulation results show that the method can also obtain accurate option prices.

The topic of National Innovation System (NIS) is gradually emphasized. The NIS includes four compositions. They are government, industry, university and public research organization. The knowledge flow is transmitted among the four compositions through innovation policy. Thus, many countries have begun to develop NIS. The NIS will raise the economic growth rate, and promote the competitiveness of industry. Consequently, the study of NIS becomes very popular. OECD (Organization for Economic Cooperation and Development) build particular NIS structures to explain the difference between members, and try to find the key successful way to achieve national innovative goals. In the Asia, the Taiwan, China, Japan and South Korea show high relationship in the politics and economics. Japan and South are high-developing countries, and their innovation activities are very successful in the world, especially in those of technology industry. Additionally, China has abundant natural resources to help them develop technology industries. For above reasons, we elect these countries to be studied, and we try to find the essential factors of successful NIS. This study includes two research issues. We first collect the secondary data to explain different NIS structure among four countries. Then, we use Stepwise Regression Analysis to evaluate the performance of innovation. Finally we use the Pearson Correlation Analysis to analyze relationship between NIS performance and semiconductor industry development. The results of this study include: (1) R&D expenditure is the most important factor to influence the performance of national innovation; (2) Expenditure on basic research is an important factor to influence the output of innovation; (3) national innovation and industry development shows high relationship; and (4) the ranking of national innovation performance is not totally the same as that of industry development. Based on these findings, we will provide some important policy suggestions for innovation activities in Taiwan.