Sähkön markkinahintaa selittävät tekijät. Case: Nord Pool 2000-2005

Sähkön markkinahinta on saanut osakseen suurta huomiota viimeaikoina. Sähkömarkkinoiden vapautuminen ja päästökaupan avaaminen Euroopassa onentisestään nostanut sähkömarkkinoita näkyville lehdissä. Tämä tutkielma tutkii erilaisten tekijöiden vaikutusta sähkön markkinahintaan regressioanalyysin avulla. Edellä mainitun päästösopimusten markkinahinnan lisäksi tutkittiin kivihiilen sekä maakaasun markkinahintojen, lämpötilojen, jokien virtaamien, vesivarantojen täyttöasteiden sekä Saksan sähkömarkkinoiden hinnan vaikutusta sähkön markkinahintaan Nord Pool -sähköpörssissä. Työssä luotiin myös sähkön markkinahintaa ennustava malli. Kaikkien selittävien tekijöiden korrelaatiot olivat oletusten mukaiset ja regressioanalyysi onnistui selittämään yli 80 % sähkön markkinahinnan vaih-teluista. Merkittävimpiä selittäviä tekijöitä olivat vesivarannot sekä jokien virtaamat. Ennustavan mallin keskimääräinen suhteellinen virhe oli noin 10 %, joten ennustetarkkuus oli melko hyvä.

Les instabilités magnétohydrodynamiques dans EULAG-MHD.

Les mécanismes qui entretiennent le cycle magnétique solaire sont encore aujourd’hui relativement mal compris. Entre autres, certains travaux suggèrent la présence d’insta- bilités magnétohydrodynamiques qui pourraient avoir une influence significative sur la période du cycle par leur capacité à accélérer la destruction des structures magnétiques à grandes échelles. Nous analysons la présence des instabilités au sein des simulations effectuées à l’aide du modèle EULAG-MHD en utilisant premièrement une méthodologie basée sur un proxy spécifique associé à l’instabilité et en le comparant à un proxy similaire, mais pour le cycle magnétique solaire observé dans notre modèle. Cette méthodologie fait ressortir une évolution temporellement cyclique du proxy de l’instabilité avec des amplitudes similaires au proxy du cycle magnétique, mais présentant un léger déphasage. Nous poursuivons cette analyse en appliquant une méthode se basant sur le découpage de “zones instables” via le critère de Tayler dans la zone stable de notre modèle. L’application expose une migration équatoriale d’une zone instable qui débute à très hautes latitudes aux pôles, passe par le champ toroïdal classique, accélère et atteint l’équateur. Cette zone instable semble accélérer la destruction du champ magnétique présent, laissant place au nouveau champ pour la prochaine demie-période du cycle. La combinaison de ces deux analyses permet d’énoncer un scénario plausible qui inclut les effets d’une telle instabilité sur le cycle magnétique ainsi que sur la stabilité globale de notre simulation. Dans ce scénario, il est important de noter que les inversions de polarités semblent indépendantes de cette instabilité, qui ne ferait qu’accélérer le processus de destruction du champ déjà en place.

A atitude frente a impunidade do menor infrator: um estudo comparativo

Este trabalho teve por objetivo um estudo comparativo da atitude frente à impunidade penal do menor infrator face a crescente criminal idade juvenil e à perspectiva de redução da idade referente a esta prerrogativa penal, com a justificativa de aumentar a responsabilidade social dos jovens. O trabalho abrange duas partes: Na primeira, é analisado o fenômeno da criminalidade, com relação na ilicitude dos jovens, procurando situar seus condicionantes sócio-econômico-culturais e reportando-se, ainda, a estudos empíricos sobre o tema. Paralelamente, e levado a efeito um estudo de atitudes, embasado no referencial teórico da Sociologia do conhecimento do Peter Berger e Thomas Luckmann. Serviram como respondentes da escala 120 sujeitos, divididos segundo os atributos de sexo, idade, nível de escolaridade e profissão. As seis categorias profissionais compunham dois amplos grupos: humanistas e não humanistas. O instrumento, escala de atitude tipo Likeri, foi construído e aplicado pela pesquisadora, obedecendo a etapas definidas e tratamentos estatísticos, tendo a forma experimental definitiva contado com 18 proposições. A análise de itens e fidedignidade da escala comprovaram a eficácia do instrumento. As hipóteses estatísticas levantadas foram testadas através da análise da variância (no grupo como um todo) e o teste do qui-quadrado (com os sujeitos já agrupados em humanistas e não humanistas), ambos com nível de significância fixado em 0,05. Os resultados da análise da variância demonstraram não haver diferenças significativas na atitude, quanto a sexo, idade e nível de escolaridade. Relação significativa foi encontra da entre profissão e a atitude pesquisada. Pelo teste do qui-quadrado evidenciaram-se diferenças significativas entre humanistas e não humanistas somente em relação ao atributo nível de escolaridade

Autoerotismo em sala de aula: o que pensam, como reagem e dizem fazer os professores?

Realizing the need for a discussion on the topic of sexuality in schools, and especially teachers training, this qualitativ e study investigated the teachers' reports about autoeroticism of their students in the cl assroom: what they thin k, how they react, say and do in their teaching prac tice. Nine teachers participated of bot h sex, who were interviewed for further projective content ana lysis. The results show that teachers, although they consider this an important work with their stud ents they expr ess difficulty talking about it, even de parting from indicating his own views and not based on theories, thus evidencing the deficiency in thei r training to deal with sexual education in school. We conclude that teachers still perceive sexuality from myths and taboos, especially on autoeroticism, and in that sens e, it is important to invest in academic training teachers to develop in a pedagogical way, continuous and systematic sexual education projects in school.

A logistic regression approach to estimating customer profit loss due to lapses in insurance

This article focuses on business risk management in the insurance industry. A methodology for estimating the profit loss caused by each customer in the portfolio due to policy cancellation is proposed. Using data from a European insurance company, customer behaviour over time is analyzed in order to estimate the probability of policy cancelation and the resulting potential profit loss due to cancellation. Customers may have up to two different lines of business contracts: motor insurance and other diverse insurance (such as, home contents, life or accident insurance). Implications for understanding customer cancellation behaviour as the core of business risk management are outlined.

Analysis and estimative of schistosomiasis prevalence for the state of Minas Gerais, Brazil, using multiple regression with social and environmental spatial data

The aim of this work is to establish a relationship between schistosomiasis prevalence and social-environmental variables, in the state of Minas Gerais, Brazil, through multiple linear regression. The final regression model was established, after a variables selection phase, with a set of spatial variables which contains the summer minimum temperature, human development index, and vegetation type variables. Based on this model, a schistosomiasis risk map was built for Minas Gerais.

In vivo targeting of an anti-tumor antibody coupled to antigenic MHC class I complexes induces specific growth inhibition and regression of established syngeneic tumor grafts.

The concept of antibody-mediated targeting of antigenic MHC/peptide complexes on tumor cells in order to sensitize them to T-lymphocyte cytotoxicity represents an attractive new immunotherapy strategy. In vitro experiments have shown that an antibody chemically conjugated or fused to monomeric MHC/peptide can be oligomerized on the surface of tumor cells, rendering them susceptible to efficient lysis by MHC-peptide restricted specific T-cell clones. However, this strategy has not yet been tested entirely in vivo in immunocompetent animals. To this aim, we took advantage of OT-1 mice which have a transgenic T-cell receptor specific for the ovalbumin (ova) immunodominant peptide (257-264) expressed in the context of the MHC class I H-2K(b). We prepared and characterized conjugates between the Fab' fragment from a high-affinity monoclonal antibody to carcinoembryonic antigen (CEA) and the H-2K(b) /ova peptide complex. First, we showed in OT-1 mice that the grafting and growth of a syngeneic colon carcinoma line transfected with CEA could be specifically inhibited by systemic injections of the conjugate. Next, using CEA transgenic C57BL/6 mice adoptively transferred with OT-1 spleen cells and immunized with ovalbumin, we demonstrated that systemic injections of the anti-CEA-H-2K(b) /ova conjugate could induce specific growth inhibition and regression of well-established, palpable subcutaneous grafts from the syngeneic CEA-transfected colon carcinoma line. These results, obtained in a well-characterized syngeneic carcinoma model, demonstrate that the antibody-MHC/peptide strategy can function in vivo. Further preclinical experimental studies, using an anti-viral T-cell response, will be performed before this new form of immunotherapy can be considered for clinical use.

Blocking hypoxia-induced autophagy in tumors restores cytotoxic T-cell activity and promotes regression.

The relationship between hypoxic stress, autophagy, and specific cell-mediated cytotoxicity remains unknown. This study shows that hypoxia-induced resistance of lung tumor to cytolytic T lymphocyte (CTL)-mediated lysis is associated with autophagy induction in target cells. In turn, this correlates with STAT3 phosphorylation on tyrosine 705 residue (pSTAT3) and HIF-1α accumulation. Inhibition of autophagy by siRNA targeting of either beclin1 or Atg5 resulted in impairment of pSTAT3 and restoration of hypoxic tumor cell susceptibility to CTL-mediated lysis. Furthermore, inhibition of pSTAT3 in hypoxic Atg5 or beclin1-targeted tumor cells was found to be associated with the inhibition Src kinase (pSrc). Autophagy-induced pSTAT3 and pSrc regulation seemed to involve the ubiquitin proteasome system and p62/SQSTM1. In vivo experiments using B16-F10 melanoma tumor cells indicated that depletion of beclin1 resulted in an inhibition of B16-F10 tumor growth and increased tumor apoptosis. Moreover, in vivo inhibition of autophagy by hydroxychloroquine in B16-F10 tumor-bearing mice and mice vaccinated with tyrosinase-related protein-2 peptide dramatically increased tumor growth inhibition. Collectively, this study establishes a novel functional link between hypoxia-induced autophagy and the regulation of antigen-specific T-cell lysis and points to a major role of autophagy in the control of in vivo tumor growth.

Robust regression applied to fractal/multifractal analysis.

Fractal and multifractal are concepts that have grown increasingly popular in recent years in the soil analysis, along with the development of fractal models. One of the common steps is to calculate the slope of a linear fit commonly using least squares method. This shouldn?t be a special problem, however, in many situations using experimental data the researcher has to select the range of scales at which is going to work neglecting the rest of points to achieve the best linearity that in this type of analysis is necessary. Robust regression is a form of regression analysis designed to circumvent some limitations of traditional parametric and non-parametric methods. In this method we don?t have to assume that the outlier point is simply an extreme observation drawn from the tail of a normal distribution not compromising the validity of the regression results. In this work we have evaluated the capacity of robust regression to select the points in the experimental data used trying to avoid subjective choices. Based on this analysis we have developed a new work methodology that implies two basic steps: ? Evaluation of the improvement of linear fitting when consecutive points are eliminated based on R pvalue. In this way we consider the implications of reducing the number of points. ? Evaluation of the significance of slope difference between fitting with the two extremes points and fitted with the available points. We compare the results applying this methodology and the common used least squares one. The data selected for these comparisons are coming from experimental soil roughness transect and simulated based on middle point displacement method adding tendencies and noise. The results are discussed indicating the advantages and disadvantages of each methodology.

Economic crises and tourism competitiveness: A Markov swtiching regression approach

Authors discuss the effects that economic crises generate on the global market shares of tourism destinations, through a series of potential transmission mechanisms based on the main economic competitiveness determinants identified in the previous literature using a non-linear approach. Specifically a Markov Switching Regression approach is used to estimate the effect of two basic transmission mechanisms: reductions of internal and external tourism demands and falling investment.

Registration-by-regression of coronary CTA and X-ray angiography

We evaluate the integration of 3D preoperative computed tomography angiography of the coronary arteries with intraoperative 2D X-ray angiographies by a recently proposed novel registration-by-regression method. The method relates image features of 2D projection images to the transformation parameters of the 3D image. We compared different sets of features and studied the influence of preprocessing the training set. For the registration evaluation, a gold standard was developed from eight X-ray angiography sequences from six different patients. The alignment quality was measured using the 3D mean target registration error (mTRE). The registration-by-regression method achieved moderate accuracy (median mTRE of 15 mm) on real images. It does therefore not provide yet a complete solution to the 3D–2D registration problem but it could be used as an initialisation method to eliminate the need for manual initialisation.

Censored Linear Regression Models For Irregularly Observed Longitudinal Data Using The Multivariate-t Distribution.

In acquired immunodeficiency syndrome (AIDS) studies it is quite common to observe viral load measurements collected irregularly over time. Moreover, these measurements can be subjected to some upper and/or lower detection limits depending on the quantification assays. A complication arises when these continuous repeated measures have a heavy-tailed behavior. For such data structures, we propose a robust structure for a censored linear model based on the multivariate Student's t-distribution. To compensate for the autocorrelation existing among irregularly observed measures, a damped exponential correlation structure is employed. An efficient expectation maximization type algorithm is developed for computing the maximum likelihood estimates, obtaining as a by-product the standard errors of the fixed effects and the log-likelihood function. The proposed algorithm uses closed-form expressions at the E-step that rely on formulas for the mean and variance of a truncated multivariate Student's t-distribution. The methodology is illustrated through an application to an Human Immunodeficiency Virus-AIDS (HIV-AIDS) study and several simulation studies.

Factors Associated With The Onset Of Hypertension In Women Of 50 Years Of Age Or More In A City In Southeastern Brazil.

To evaluate factors associated with hypertension in Brazilian women of 50 years of age or more. A cross-sectional population based study using self-reports. A total of 622 women were included. The association between sociodemographic, clinical and behavioral factors and the woman's age at the onset of hypertension was evaluated. Data were analyzed according to cumulative continuation rates without hypertension, using the life-table method and considering annual intervals. Next, a Cox multiple regression analysis model was adjusted to analyze the occurrence rates of hypertension according to various predictor variables. Significance level was pre-established at 5% (95% confidence level) and the sampling plan (primary sampling unit) was taken into consideration. Median age at onset of hypertension was 64.3 years. Cumulative continuation rate without hypertension at 90 years was 20%. Higher body mass index (BMI) at 20-30 years of age was associated with a higher cumulative occurrence rate of hypertension over time (coefficient=0.078; p<0.001). Being white was associated with a lower cumulative occurrence rate of hypertension over time (coefficient= -0.439; p=0.003), while smoking >15 cigarettes/day was associated with a higher rate over time (coefficient=0.485; p=0.004). The results of the present study highlight the importance of weight control in young adulthood and of avoiding smoking in preventing hypertension in women aged ≥50 years.

Dyspareunia In Hiv-positive And Hiv-negative Middle-aged Women: A Cross-sectional Study.

To evaluate whether dyspareunia is associated with HIV status in menopausal women and also to assess which factors are associated with dyspareunia in a group of HIV-positive menopausal women. A cross-sectional study was conducted with 178 HIV-negative and 128 HIV-positive women aged 40-60 years. The Short Personal Experiences Questionnaire (SPEQ) was used to collect data. Sociodemographic, clinical, behavioural and reproductive factors were evaluated, as well as factors related to the HIV infection. Dyspareunia was defined as pain during intercourse. A bivariate analysis and Poisson multiple regression analysis were performed. Overall, 41.4% of the HIV-positive women reported dyspareunia compared with 34.8% of the HIV-negative women (p=0.242). In the HIV-positive women, bivariate analysis revealed an association between dyspareunia and having a steady partner (p=0.047); the woman's partner having undergone HIV testing (p=0.020); vaginal dryness (p<0.001); muscle/joint pain (p=0.021); physical/emotional violence (p=0.049); urinary incontinence (p=0.004); and the use of lamivudine/zidovudine (p=0.048). The Poisson multiple regression analysis found an association between dyspareunia and vaginal dryness (prevalence ratio (PR)=1.96, 95% CI 1.10 to 3.50, p=0.023) and urinary incontinence (PR=1.86, 95% CI 1.06 to 3.27, p=0.031). Dyspareunia was common in this group of HIV-positive women and was associated principally with vaginal dryness and urinary incontinence. The importance of treating dyspareunia within the context of sexual health in this group of women should be emphasised and appropriate management of this issue may reduce the likelihood of lesions on the vaginal wall, which may act as a portal of entry for other infections.

Factors Associated With The Age Of The Onset Of Diabetes In Women Aged 50 years Or More: A Population-based Study.

Investigate factors associated with the onset of diabetes in women aged more than 49 years. Cross-sectional, population-based study using self-reports with 622 women. The dependent variable was the age of occurrence of diabetes using the life table method. Cox multiple regression models were adjusted to analyse the onset of diabetes according to predictor variables. Sociodemographic, clinical and behavioural factors were evaluated. Of the 622 women interviewed, 22.7% had diabetes. The mean age at onset was 56 years. The factors associated with the age of occurrence of diabetes were self-rated health (very good, good) (coefficient=-0.792; SE of the coefficient=0.215; p=0.0001), more than two individuals living in the household (coefficient=0.656, SE of the coefficient=0.223; p=0.003), and body mass index (BMI) (kg/m(2)) at 20-30 years of age (coefficient= 0.056, SE of the coefficient=0.023; p=0.014). Self-rated health considered good or very good was associated with a higher rate of survival without diabetes. Sharing a home with two or more other people and a weight increase at 20-30 years of age was associated with the onset of type 2 diabetes.