Pure strategy equilibria of multidimensional and non-monotonic auctions

We give necessary and sufficient conditions for the existence of symmetric equilibrium without ties in interdependent values auctions, with multidimensional independent types and no monotonic assumptions. In this case, non-monotonic equilibria might happen. When the necessary and sufficient conditions are not satisfied, there are ties with positive probability. In such case, we are still able to prove the existence of pure strategy equilibrium with an all-pay auction tie-breaking rule. As a direct implication of these results, we obtain a generalization of the Revenue Equivalence Theorem. From the robustness of equilibrium existence for all-pay auctions in multidimensional setting, an interpretation of our results can give a new justification to the use of tournaments in practice.

Mercado brasileiro: aplicação de análise de componentes principais no cálculo de VAR para carteiras de renda fixa

A abordagem do Value at Risk (VAR) neste trabalho será feita a partir da análise da curva de juros por componentes principais (Principal Component Analysis – PCA). Com essa técnica, os movimentos da curva de juros são decompostos em um pequeno número de fatores básicos independentes um do outro. Entre eles, um fator de deslocamento (shift), que faz com que as taxas da curva se movam na mesma direção, todas para cima ou para baixo; de inclinação (twist) que rotaciona a curva fazendo com que as taxas curtas se movam em uma direção e as longas em outra; e finalmente movimento de torção, que afeta vencimentos curtos e longos no mesmo sentido e vencimentos intermediários em sentido oposto. A combinação destes fatores produz cenários hipotéticos de curva de juros que podem ser utilizados para estimar lucros e perdas de portfolios. A maior perda entre os cenários gerados é uma maneira intuitiva e rápida de estimar o VAR. Este, tende a ser, conforme verificaremos, uma estimativa conservadora do respectivo percentual de perda utilizado. Existem artigos sobre aplicações de PCA para a curva de juros brasileira, mas desconhecemos algum que utilize PCA para construção de cenários e cálculo de VAR, como é feito no presente trabalho.Nesse trabalho, verificaremos que a primeira componente principal produz na curva um movimento de inclinação conjugado com uma ligeira inclinação, ao contrário dos resultados obtidos em curvas de juros de outros países, que apresentam deslocamentos praticamente paralelos.

A systematic component of the jump-risk premium in an AJD model

We develop an affine jump diffusion (AJD) model with the jump-risk premium being determined by both idiosyncratic and systematic sources of risk. While we maintain the classical affine setting of the model, we add a finite set of new state variables that affect the paths of the primitive, under both the actual and the risk-neutral measure, by being related to the primitive's jump process. Those new variables are assumed to be commom to all the primitives. We present simulations to ensure that the model generates the volatility smile and compute the "discounted conditional characteristic function'' transform that permits the pricing of a wide range of derivatives.

Optimisation of solid-phase microextraction combined with gas chromatography–mass spectrometry based methodology to establish the global volatile signature in pulp and skin of Vitis vinifera L. grape varieties

The volatiles (VOCs) and semi-volatile organic compounds (SVOCs) responsible for aroma are mainly present in skin of grape varieties. Thus, the present investigation is directed towards the optimisation of a solvent free methodology based on headspace-solid-phase microextraction (HS-SPME) combined with gas chromatography–quadrupole mass spectrometry (GC–qMS) in order to establish the global volatile composition in pulp and skin of Bual and Bastardo Vitis vinifera L. varieties. A deep study on the extraction-influencing parameters was performed, and the best results, expressed as GC peak area, number of identified compounds and reproducibility, were obtained using 4 g of sample homogenised in 5 mL of ultra-pure Milli-Q water in a 20 mL glass vial with addition of 2 g of sodium chloride (NaCl). A divinylbenzene/carboxen/polydimethylsiloxane fibre was selected for extraction at 60 °C for 45 min under continuous stirring at 800 rpm. More than 100 VOCs and SVOCs, including 27 monoterpenoids, 27 sesquiterpenoids, 21 carbonyl compounds, 17 alcohols (from which 2 aromatics), 10 C13 norisoprenoids and 5 acids were identified. The results showed that, for both grape varieties, the levels and number of volatiles in skin were considerably higher than those observed in pulp. According to the data obtained by principal component analysis (PCA), the establishment of the global volatile signature of grape and the relationship between different part of grapes—pulp and skin, may be an useful tool to winemaker decision to define the vinification procedures that improves the organoleptic characteristics of the corresponding wines and consequently contributed to an economic valorization and consumer acceptance.

Neuronal Assembly Detection and Cell Membership Specification by Principal Component Analysis

LOPES-DOS-SANTOS, V. , CONDE-OCAZIONEZ, S. ; NICOLELIS, M. A. L. , RIBEIRO, S. T. , TORT, A. B. L. . Neuronal assembly detection and cell membership specification by principal component analysis. Plos One, v. 6, p. e20996, 2011.

Reduction capability of soil humic substances from the Rio Negro basin, Brazil, towards Hg(II) studied by a multimethod approach and principal component analysis (PCA)

This paper characterizes humic substances (HS) extracted from soil samples collected in the Rio Negro basin in the state of Amazonas, Brazil, particularly investigating their reduction capabilities towards Hg(II) in order to elucidate potential mercury cycling/volatilization in this environment. For this reason, a multimethod approach was used, consisting of both instrumental methods (elemental analysis, EPR, solid-state NMR, FIA combined with cold-vapor AAS of Hg(0)) and statistical methods such as principal component analysis (PCA) and a central composite factorial planning method. The HS under study were divided into groups, complexing and reducing ones, owing to different distribution of their functionalities. The main functionalities (cor)related with reduction of Hg(II) were phenolic, carboxylic and amide groups, while the groups related with complexation of Hg(II) were ethers, hydroxyls, aldehydes and ketones. The HS extracted from floodable regions of the Rio Negro basin presented a greater capacity to retain (to complex, to adsorb physically and/or chemically) Hg(II), while nonfloodable regions showed a greater capacity to reduce Hg(II), indicating that HS extracted from different types of regions contribute in different ways to the biogeochemical mercury cycle in the basin of the mid-Rio Negro, AM, Brazil. (c) 2007 Published by Elsevier B.V.

Fatores litogênicos em pacientes com litíase urinária de Fortaleza, Ceará

Lithiasis is considered a public health issue due to its high prevalence and rates of recurrence. Objective: To identify risk factors for lithiasis in kidney stone patients from Fortaleza, Brazil. In the first stage of the study, the medical records of 197 patients with urinary lithiasis covering the period 1996 2006 were analyzed with regard to clinical and metabolic data. In the second stage, 340 kidney stones were submitted to morphological examination under 10x magnification. According to the external morphology and the cut surface, the stones were classified as pure or mixed, and major and minor components were identified. In addition, the stone fragments of 25 patients treated with lithotripsy were submitted to morphological analysis. In the third stage, a subsample of 50 stones was used in a double-blind comparison of morphological and chemical findings. Results were expressed as concordant, partly concordant (discordant for minor components) or discordant (discordant for major components). The average age of first symptoms was 35.8±13.3 years, with no significant difference between the genders. The male/female ratio was 1:1.7. Recurrence was reported in 53.3% of cases. The main metabolic changes observed were hypernatriuria (80.7%), hypercalciuria (48.7%), low urine volume (43.7%), hyperoxaluria (30.5%) and hyperuricosuria (17.3%). Pure stones represented 34.7% of the total sample of 340 stones. The most common route of elimination was spontaneous for pure stones (49.1%) and surgical for mixed stones (50.5%). Pure stones consisted most frequently of calcium oxalate (OxCa) (59.3%) and uric acid (UA) (23.7%), the former prevalent in women, the latter prevalent in men. The most frequently observed component in mixed stones was OxCa (67.1%), followed by carbapatite (11.2%) and struvite (7.9%). The main components were OxCa and UA for men, and carbapatite and struvite for women. Nearly half (48%) the 25 analyzed fragments were pure, consisting of calcium oxalate dihydrate (COD) (56%), calcium oxalate monohydrate (COM) (48%), phosphate (32%) and UA (20%). Four patients (16%) had infectious stones. In the chemical analysis of the subsample of 50 stones, the most 64 frequently observed major components were calcium (70%), oxalate (66%), ammonium (56%), urate (28%) and carbonate (24%). In the morphological analysis, the main components were calcium and magnesium phosphate (32%), COM (24%), UA (20%), COD (18%) and cystine (6%). Morphological and chemical findings were totally concordant for 38% of the stones, partly concordant in 52% and discordant in 10%. Conclusion: The risk factors for lithiasis in kidney stone patients from Fortaleza (Brazil) were hyperoxaluria, hypercalciuria with or without hypernatriuria, hyperuricosuria and low urine volume

O sensível no trabalho docente: representação social entre docentes do Instituto Federal de Educação, Ciência e Tecnologia do Rio Grande do Norte

The aim of this study was to analyze the social representation of the sensible among teachers of the Federal Institute of Education, Science and Technology of Rio Grande do Norte, attempting to identify its constituents and understand the dynamics that gives functionality to your organization. The study is significant considering that the professional conduct can not be delineated in its complexity without unraveling the social representations that teachers themselves have of their being and doing professional. The theoretical and methodological framework of the research is the theory of social representation. 107 teachers from various backgrounds participated. To collect the data were used as instruments : a questionnaire listing, which subsidizes the characterization of the subjects , the TALP - technique of free association of words ( ABRIC , 1994) , the PCM - Procedure for Multiple Ratings ( ROAZZI , 1995) ; questionnaire redemption of sensitive memories of the subjects in their school experiences of childhood , adolescence, youth and teaching practice . The PCM data, in which the slogan was directed at rating Give class, were submitted to multidimensional statistical analysis. Already TALP was analyzed by EVOC 2000 software, the profile questionnaire received descriptive statistical analysis and the memories received the questionnaire analysis of thematic content, Bardin (2004). Taken together, the results point to a social representation of sensitive teaching (the game, the fun, the touch, the smile, the relaxation) are not in the classroom. The sensitive pure still fits in school, but only in the courtyard, on the playground, in the intervals, therefore, outside of space-time class, playful perch that lives in each of us is totally strange to this world of the classroom . After doing the Approximation of ideas , we realized three discourses evident in the reports of teachers : the discourse of Numbness in which we perceive the distance of the teacher in relation to sensitive component as a facilitator in the learning process , the discourse of Feeling , in which we can discern small approximation to the sensitive dialogues and proposed in this study , the speech of reflection in which teachers analyze, evaluate and establish a discourse on the importance of education in sensitive , but not actualize in their teaching practice

Kinetics of cellular component in inflammatory response induced by different stimuli in the swim bladder of pacu, Piaractus mesopotamicus Holmberg 1887 (Characidae)

The present study assessed the kinetics of cell accumulation at the site of inflammation induced by thioglycolate, Escherichia coli lipopolysaccharide (LPS) and heat-inactivated Aeromonas hydrophila, in the pacu, Piaractus mesopotamicus (Characidae), swim bladder. A quantitative, as well as qualitative, assessment was done of all the cells present in the exudate at 6, 24, and 48 h (n = 8) after inoculation of inflammatory agents. The results show that the thioglycolate was the irritant to induce higher total inflammatory cell accumulation when compared to the control group, 6 h after insult (P < 0.05). Inoculation of heat-inactivated Aeromonas hydrophila induced progressive accumulation of total inflammatory cells, with cell number peaking after 24 h and being significantly higher than observed in the other groups (P < 0.05). Injection of LPS also induced greater cell accumulation when compared to the control group (P < 0.05), although in lower numbers than those induced by the other two irritants. All irritants injected induced significantly greater accumulation of lymphocytes and thrombocytes when compared to the control group (P < 0.05).