Optimization of wood flour acetylation by factorial design and partial least squares regression

Acetylation was performed to reduce the polarity of wood and increase its compatibility with polymer matrices for the production of composites. These reactions were performed first as a function of acetic acid and anhydride concentration in a mixture catalyzed by sulfuric acid. A concentration of 50%/50% (v/v) of acetic acid and anhydride was found to produced the highest conversion rate between the functional groups. After these reactions, the kinetics were investigated by varying times and temperatures using a 3² factorial design, and showed time was the most relevant parameter in determining the conversion of hydroxyl into carbonyl groups.

Least squares regression with errors in both variables: case studies

Analytical curves are normally obtained from discrete data by least squares regression. The least squares regression of data involving significant error in both x and y values should not be implemented by ordinary least squares (OLS). In this work, the use of orthogonal distance regression (ODR) is discussed as an alternative approach in order to take into account the error in the x variable. Four examples are presented to illustrate deviation between the results from both regression methods. The examples studied show that, in some situations, ODR coefficients must substitute for those of OLS, and, in other situations, the difference is not significant.

Regime Switching Models for Electricity Time Series that Capture Fat Tailed Distributions

In the power market, electricity prices play an important role at the economic level. The behavior of a price trend usually known as a structural break may change over time in terms of its mean value, its volatility, or it may change for a period of time before reverting back to its original behavior or switching to another style of behavior, and the latter is typically termed a regime shift or regime switch. Our task in this thesis is to develop an electricity price time series model that captures fat tailed distributions which can explain this behavior and analyze it for better understanding. For NordPool data used, the obtained Markov Regime-Switching model operates on two regimes: regular and non-regular. Three criteria have been considered price difference criterion, capacity/flow difference criterion and spikes in Finland criterion. The suitability of GARCH modeling to simulate multi-regime modeling is also studied.

Switching components for medium voltage drives

Nowadays power drives are the essential part almost of all technological processes. Improvement of efficiency and reduction of losses require development of semiconductor switches. It has a particular meaning for the constantly growing market of renewable sources, especially for wind turbines, which demand more powerful semiconductor devices for control with growth of power. Also at present semiconductor switches are the key component in energy transmission, optimization of generation and network connection. The aim of this thesis is to make a survey of contemporary semiconductor components, showing difference in structures, advantages, disadvantages and most suitable applications. There is topical information about voltage, frequency and current limits of different switches. Study tries to compare dimensions and price of different components. Main manufacturers of semiconductor components are presented with the review of devices produced by them, and a conclusion about their availability was made. IGBT is selected as a main component in this study, because nowadays it is the most attractive component for usage in power drives, especially at the low levels of medium voltage. History of development of IGBT structure, static and dynamic characteristics are considered. Thesis tells about assemblies and connection of components and problems which can appear. One of key questions about semiconductor materials and their future development was considered. For the purpose of comparison strong and weak sides of different switches, calculation of losses of IGBT and its basic competitor – IGCT is presented. This master’s thesis makes an effort to answer the question if there are at present possibilities of accurate selection of switches for electrical drives of different rates of power and looks at future possible ways of development of semiconductor market.

Logistic regression to estimate the welfare of broiler breeders in relation to environmental and behavioral variables

The increasing demand of consumer markets for the welfare of birds in poultry house has motivated many scientific researches to monitor and classify the welfare according to the production environment. Given the complexity between the birds and the environment of the aviary, the correct interpretation of the conduct becomes an important way to estimate the welfare of these birds. This study obtained multiple logistic regression models with capacity of estimating the welfare of broiler breeders in relation to the environment of the aviaries and behaviors expressed by the birds. In the experiment, were observed several behaviors expressed by breeders housed in a climatic chamber under controlled temperatures and three different ammonia concentrations from the air monitored daily. From the analysis of the data it was obtained two logistic regression models, of which the first model uses a value of ammonia concentration measured by unit and the second model uses a binary value to classify the ammonia concentration that is assigned by a person through his olfactory perception. The analysis showed that both models classified the broiler breeder's welfare successfully.

Adjust of regression models to estimate the rectal temperature of broilers for the first 14 days of life

The broiler rectal temperature (t rectal) is one of the most important physiological responses to classify the animal thermal comfort. Therefore, the aim of this study was to adjust regression models in order to predict the rectal temperature (t rectal) of broiler chickens under different thermal conditions based on age (A) and a meteorological variable (air temperature - t air) or a thermal comfort index (temperature and humidity index -THI or black globe humidity index - BGHI) or a physical quantity enthalpy (H). In addition, through the inversion of these models and the expected t rectal intervals for each age, the comfort limits of t air, THI, BGHI and H for the chicks in the heating phase were determined, aiding in the validation of the equations and the preliminary limits for H. The experimental data used to adjust the mathematical models were collected in two commercial poultry farms, with Cobb chicks, from 1 to 14 days of age. It was possible to predict the t rectal of conditions from the expected t rectal and determine the lower and superior comfort thresholds of broilers satisfactorily by applying the four models adjusted; as well as to invert the models for prediction of the environmental H for the chicks first 14 days of life.

Novel Regression Methods For Spectral Data

Singular Value Decomposition (SVD), Principal Component Analysis (PCA) and Multiple Linear Regression (MLR) are some of the mathematical pre- liminaries that are discussed prior to explaining PLS and PCR models. Both PLS and PCR are applied to real spectral data and their di erences and similarities are discussed in this thesis. The challenge lies in establishing the optimum number of components to be included in either of the models but this has been overcome by using various diagnostic tools suggested in this thesis. Correspondence analysis (CA) and PLS were applied to ecological data. The idea of CA was to correlate the macrophytes species and lakes. The di erences between PLS model for ecological data and PLS for spectral data are noted and explained in this thesis. i

Ecosystem architecture design: endogenous and exogenous structural properties

The aim of this dissertation is to bridge and synthesize the different streams of literature addressing ecosystem architecture through a multiple‐lens perspective. In addition, the structural properties of and processes to design and manage the architecture will be examined. With this approach, the oft‐neglected actor‐structure duality is addressed and both the position and structure, and action and process are under scrutiny. Further, the developed framework and empirical evidence offer valuable insights on how firms collectively create value and individually appropriate value. The dissertation is divided into two parts. The first part comprises a literature review, as well as the conclusions of the whole study, and the second part includes six research publications. The dissertation is based on three different reasoning logics: abduction, induction and deduction; related qualitative and quantitative methodologies are utilized in the empirical examination of the phenomenon in the information and communication technology industry. The results suggest firstly that there are endogenous and exogenous structural properties of the ecosystem architecture. Out of these, the former ones can be more easily influenced by a particular actor whereas the latter ones are taken more or less for granted. Secondly, the exogenous ecosystem design properties influence the value creation potential of the ecosystem whereas the endogenous ecosystem design properties influence the value appropriation potential of a particular actor in the ecosystem. Thirdly, the study suggests that there is a relationship between endogenous and exogenous structural properties in that the endogenous properties can be leveraged to create and reconfigure the exogenous properties whereas the exogenous properties prose opportunities and restrictions on the use of endogenous properties. In addition, the study suggests that there are different emergent and engineered processes to design and manage ecosystem architecture and to influence both the endogenous and exogenous structural properties of ecosystem architecture. This study makes three main contributions. First, on the conceptual level, it brings coherence and direction to the fast growing body of literature on novel inter‐organizational arrangements, such as ecosystems. It does this by bridging and synthetizing three different streams of literature, namely the boundary, design and orchestration conception. Secondly, it sets out a framework that enhances our understanding of the structural properties of ecosystem architecture; of the processes to design and manage ecosystem architecture; and of their influence on the value creation potential of the ecosystem and the value capture potential of a particular firm. Thirdly, it offers empirical evidence of the structural properties and processes.

Prediction of market switching and delisting events from OMX First North Nordic multilateral stock exchange

This thesis studies the predictability of market switching and delisting events from OMX First North Nordic multilateral stock exchange by using financial statement information and market information from 2007 to 2012. This study was conducted by using a three stage process. In first stage relevant theoretical framework and initial variable pool were constructed. Then, explanatory analysis of the initial variable pool was done in order to further limit and identify relevant variables. The explanatory analysis was conducted by using self-organizing map methodology. In the third stage, the predictive modeling was carried out with random forests and support vector machine methodologies. It was found that the explanatory analysis was able to identify relevant variables. The results indicate that the market switching and delisting events can be predicted in some extent. The empirical results also support the usability of financial statement and market information in the prediction of market switching and delisting events.

Endogenous vasopressin and the central control of heart rate during dynamic exercise

The present article contains a brief review on the role of vasopressinergic projections to the nucleus tractus solitarii in the genesis of reflex bradycardia and in the modulation of heart rate control during exercise. The effects of vasopressin on exercise tachycardia are discussed on the basis of both the endogenous peptide content changes and the heart rate response changes observed during running in sedentary and trained rats. Dynamic exercise caused a specific vasopressin content increase in dorsal and ventral brainstem areas. In accordance, rats pretreated with the peptide or the V1 blocker into the nucleus tractus solitarii showed a significant potentiation or a marked blunting of the exercise tachycardia, respectively, without any change in the pressure response to exercise. It is proposed that the long-descending vasopressinergic pathway to the nucleus tractus solitarii serves as one link between the two main neural controllers of circulation, i.e., the central command and feedback control mechanisms driven by the peripheral receptors. Therefore, vasopressinergic input could contribute to the adjustment of heart rate response (and cardiac output) to the circulatory demand during exercise.

Carbon monoxide: from toxin to endogenous modulator of cardiovascular functions

Carbon monoxide (CO) is a pollutant commonly recognized for its toxicological attributes, including CNS and cardiovascular effects. But CO is also formed endogenously in mammalian tissues. Endogenously formed CO normally arises from heme degradation in a reaction catalyzed by heme oxygenase. While inhibitors of endogenous CO production can raise arterial pressure, heme loading can enhance CO production and lead to vasodepression. Both central and peripheral tissues possess heme oxygenases and generate CO from heme, but the inability of heme substrate to cross the blood brain barrier suggests the CNS heme-heme oxygenase-CO system may be independent of the periphery. In the CNS, CO apparently acts in the nucleus tractus solitarii (NTS) promoting changes in glutamatergic neurotransmission and lowering blood pressure. At the periphery, the heme-heme oxygenase-CO system can affect cardiovascular functions in a two-fold manner; specifically: 1) heme-derived CO generated within vascular smooth muscle (VSM) can promote vasodilation, but 2) its actions on the endothelium apparently can promote vasoconstriction. Thus, it seems reasonable that the CNS-, VSM- and endothelial-dependent actions of the heme-heme oxygenase-CO system may all affect cardiac output and vascular resistance, and subsequently blood pressure.

The cardiopulmonary reflexes of spontaneously hypertensive rats are normalized after regression of left ventricular hypertrophy and hypertension

Cardiopulmonary reflexes are activated via changes in cardiac filling pressure (volume-sensitive reflex) and chemical stimulation (chemosensitive reflex). The sensitivity of the cardiopulmonary reflexes to these stimuli is impaired in the spontaneously hypertensive rat (SHR) and other models of hypertension and is thought to be associated with cardiac hypertrophy. The present study investigated whether the sensitivity of the cardiopulmonary reflexes in SHR is restored when cardiac hypertrophy and hypertension are reduced by enalapril treatment. Untreated SHR and WKY rats were fed a normal diet. Another groups of rats were treated with enalapril (10 mg kg-1 day-1, mixed in the diet; SHRE or WKYE) for one month. After treatment, the volume-sensitive reflex was evaluated in each group by determining the decrease in magnitude of the efferent renal sympathetic nerve activity (RSNA) produced by acute isotonic saline volume expansion. Chemoreflex sensitivity was evaluated by examining the bradycardia response elicited by phenyldiguanide administration. Cardiac hypertrophy was determined from the left ventricular/body weight (LV/BW) ratio. Volume expansion produced an attenuated renal sympathoinhibitory response in SHR as compared to WKY rats. As compared to the levels observed in normotensive WKY rats, however, enalapril treatment restored the volume expansion-induced decrease in RSNA in SHRE. SHR with established hypertension had a higher LV/BW ratio (45%) as compared to normotensive WKY rats. With enalapril treatment, the LV/BW ratio was reduced to 19% in SHRE. Finally, the reflex-induced bradycardia response produced by phenyldiguanide was significantly attenuated in SHR compared to WKY rats. Unlike the effects on the volume reflex, the sensitivity of the cardiac chemosensitive reflex to phenyldiguanide was not restored by enalapril treatment in SHRE. Taken together, these results indicate that the impairment of the volume-sensitive, but not the chemosensitive, reflex can be restored by treatment of SHR with enalapril. It is possible that by augmenting the gain of the volume-sensitive reflex control of RSNA, enalapril contributed to the reversal of cardiac hypertrophy and normalization of arterial blood pressure in SHR.

Endogenous opiate analgesia induced by tonic immobility in guinea pigs

A function of the endogenous analgesic system is to prevent recuperative behaviors generated by tissue damage, thus preventing the emission of species-specific defensive behaviors. Activation of intrinsic nociception is fundamental for the maintenance of the behavioral strategy adopted. Tonic immobility (TI) is an inborn defensive behavior characterized by a temporary state of profound and reversible motor inhibition elicited by some forms of physical restraint. We studied the effect of TI behavior on nociception produced by the formalin and hot-plate tests in guinea pigs. The induction of TI produced a significant decrease in the number of flinches (18 ± 6 and 2 ± 1 in phases 1 and 2) and lickings (6 ± 2 and 1 ± 1 in phases 1 and 2) in the formalin test when compared with control (75 ± 13 and 22 ± 6 flinches in phases 1 and 2; 28 ± 7 and 17 ± 7 lickings in phases 1 and 2). In the hot-plate test our results also showed antinociceptive effects of TI, with an increase in the index of analgesia 30 and 45 min after the induction of TI (0.67 ± 0.1 and 0.53 ± 0.13, respectively) when compared with control (-0.10 ± 0.08 at 30 min and -0.09 ± 0.09 at 45 min). These effects were reversed by pretreatment with naloxone (1 mg/kg, ip), suggesting that the hypoalgesia observed after induction of TI behavior, as evaluated by the algesimetric formalin and hot-plate tests, is due to activation of endogenous analgesic mechanisms involving opioid synapses.

Parathyroid hormone secretion in chronic human endogenous hypercortisolism

Osteoporosis is a common manifestation of Cushing's syndrome, but the mechanisms responsible for this abnormality have not been defined. With the objective of analyzing parathyroid hormone (PTH) secretion in chronic hypercortisolism (CH), we evaluated 11 healthy subjects and 8 patients with CH, 6 with Cushing's disease and 2 with adrenal adenoma. These volunteers were submitted to tests of PTH stimulation through hypocalcemia (EDTA), PTH suppression through hypercalcemia (iv and oral calcium), and evaluation of bone mineral density (BMD) by DEXA. During the test of PTH stimulation, the calcium and magnesium concentrations of the normal and CH groups were similar. Patients with CH showed an increased PTH response to the hypocalcemic stimulus compared to controls. PTH values were significantly higher in the CH group at 70 (17.5 ± 3.5 vs 10.2 ± 1.3 pmol/l, P = 0.04), and 120 min (26.1 ± 5.9 vs 11.3 ± 1.9 pmol/l, P = 0.008) of EDTA infusion. The area under the curve for PTH during EDTA infusion was also significantly higher in patients with CH than in normal subjects (1867 ± 453 and 805 ± 148 pmol l-1 2 h-1, P = 0.02). During the test of PTH suppression, calcium, magnesium and PTH levels of the patients with hypercortisolism and controls were similar. BMD was decreased in patients with hypercortisolism in the spine (0.977 ± 0.052 vs 1.205 ± 0.038 g/cm² in controls, P<0.01). In conclusion, our results show that subjects with CH present decreased bone mass mainly in trabecular bone. The use of dynamic tests permitted the detection of increased PTH secretion in response to a hypocalcemic stimulus in CH patients that may probably be involved in the occurrence of osteoporosis in this state.