Pure Strategy Equilibria of Multidimensional and Non-Monotonic Auctions

We give necessary and sufficient conditions for the existence of symmetric equilibrium without ties in common values auctions, with multidimensional independent types and no monotonic assumptions. When the conditions are not satisfied, we are still able to prove the existence of pure strategy equilibrium with an exogenous and explicit tie breaking mechanism. As a basis for these results, we obtain a characterization lemma that is valid under a general setting, that includes non-independent types, asymmetrical utilities and any attitude towards risk. Such characterization gives a basis for an intuitive interpretation for the behavior of the bidder: to bid in order to equalize the marginal benefit and the marginal cost of biddingauctions, pure strategy equilibria, non-monotonic bidding functions, tie-breaking

Supersymmetric variational energies of 3d confined potentials

Within the approach of Supersymmetric Quantum Mechanics associated with the variational method a recipe to construct the superpotential of three dimensional confined potentials in general is proposed. To illustrate the construction, the energies of the Harmonic Oscillator and the Hulth\'en potential, both confined in three dimensions are evaluated. Comparison with the corresponding results of other approximative and exact numerical results is presented.Comment: 9 pages, Late

Numerical modeling of the response of Ceará continental shelf waters to wind stress forcing

A resposta das águas da plataforma continental do Ceará, de Ponta Cajuais (04°42'S, 37° 19,5'W), à forçante do vento estacionária e transiente foi estudada através de um modelo numérico hidrodinâmico. O modelo, na forma de diferenças finitas, utiliza as equações do movimento e da continuidade de massa para um oceano barotr6pico no caso mais geral: estão incluídos os termos advectivos, bem como o atrito com o fundo e a tensão de cisalhamento do vento, ambos parametrizados na forma quadrática. Variações sazonais na resposta estacionária das águas da plataforma continental, da área estudada, foram caracterizadas pela simulação das condições de verão e inverno da região. Os experimentos foram realizados no plano f e no plano p equatorial sem diferenças significativas nos resultados. A resposta transiente das águas da plataforma continental, da região escolhida, foi investigada usando uma série temporal de vento de superfície do Aeroporto de Fortaleza do período de 14 à 25 de março. O período escolhido para a simulação coincide com o período em que há dados observados de corrente na região. A corrente modelada descreveu o padrão da corrente observada mas não sua intensidade.Ceará shelf waters response to steady and transicnt wind forcing, from Ponta Cajuais (04°42'S, 37°19.5'W) to Ponta de Itapagé (02°50.5'S, 40000'W), was studied using a hydrodynamic numerical model. The finitc difference model was based upon the equations for a barotropic ocean in general form: advective and quadratic surface and bottom stress terms were included. Seasonal differences in the shelf waters response were characterized by simulation of summer and winter forcing. Such experiments wcre conducted for both f and equatorial beta plane domains, without significative differences in the results. Transient shelf waters response were investigated using surface winds from the Fortaleza airport , during the period extending from 14/03 to 25/03n9. Model results were compared to current data collected during the same period; modeled currents were able to roughly describe observed current pattem, but not current intensity

Tougher educational exam leading to worse selection

This paper shows a somehow counterintuitive result: an increase in the exam difficulty may reduce the average quality (productivity) of selected individuals. Since the exam does not verify all skills, when its standard rises, candidates with relatively low skills emphasized in the test and high skills demanded in the job may no longer qualify. Hence, an increase in the testing standard may be counterproductive. One implication is that policies should emphasize alignment between the skills tested and those required in the actual jobs

On the salt transport in the Cananéia sea during a spring tide experiment

Observations of the velocity, salinity, water depths and tides in the southem region of the Cananéia Sea were sampled at an anchored station during two complete tidal cycles. The measurements were made during spring tides on 5-6 December, 1991. The observed non-tidal current profile for this weakly stratified tidal channel is found to be in close agreement with the results of a simple steady state unidimensional analytical model of a well-nuxed estuary. This comparison indicates that the primary driving mechanisms are the longitudinal salinity gradient and the fresh water discharge. The contribution to the advective salt transport is dominateô by the freshwater discharge through the down-stream non-tidal flow and the up-stream dispersive term due to Stokes wave transporto This dispersive term is almost one order of magnitude smaller than the down-stream non-tidãl transport inôuced bythe fresh water discharge. TidaI correlation, acting as a counter-dispersion term, and the steady shear dispersion term are two orders of magnitude smaller than the ôown-stream salt transporto The remaining dispersive terms, which are dependent on the deviations from the mean deptb, are smaller than eitlier of these terms by one order of magnitude. The computed total salt transport per unit width of a section perpendicular to the mean flow was in close agreement (within 12 %) with the sum of the individual advective and dispersive terms. On the assumption that the tidal channel sampled is laterally homogeneous, an imoalance of the salt budget across the section was observed.Observações de velocidade, de salinidade, de profundidade e de maré na região sul do Mar de Cananéia foram realizadas numa estação fixa durante dois ciclos completos de maré. Essas medidas foram feitas durante maré de sizígia, no período de 5 a 6 de dezem6ro de 1991. A exame comparativo do perfil estacionário de velocidade desse sistema fracamente estratificado, indicou boa concordância com os resultados de um modelo analítico unidimensional de um estuário ideal verticalmente homogêneo. Dessa comparação, foi possível concluir que as principais forças geradoras desse movimento são o gradiente longitudinal de densidade e a descarga de água doce. A contribuição para o transporte advectivo de sal é dominado pela descarga total de água doce e pelo termo dispersivo, gerado pela propagação da onda de maré no canal estuarino (transporte de Stokes). Esse termo dispersivo é quase uma ordem de grandeza menor do que o termo associado à descarga estacionária de água doce. O termo de correlação da maré, que atua no sentido contrário aos termos dispersivos e o termo dispersivo gerado pelo cisalhamento da circulação gravitacional, são cerca de duas ordens de grandeza menores do que a parcela advectiva estacionária que atua estuário abaixo. Os termos dispersivos remanescentes e que dependem da amplitude da maré, são uma ordem de grandeza menores do que o valor estimado para o termo gerado pela circulação gravitacional. O transporte total de sal, por unidade de largura da seção transversal, integrado diretamente é concordante com o valor obtido pela somatória de todos os termos advectivos e dispersivos, com um desvio inferior a 12 %. Na hipótese de que o canal estuarino amostrado é lateralmente homogêneo, observou-se que o transporte de sal não estava em balanço

Note on the occurrence of saline fronts in the Ilha Grande (RJ) region

Registros contínuos da temperatura e da salinidade, em função de distâncias horizontais, foram obtidos para as águas de superfície existentes ao redor da Ilha Grande, em 21 de junho de 1975. Foi detectado um fluxo de água com baixa salinidade (S ~ 33,10º /oo) e temperatura ligeiramente maior do que a das águas adjacentes, na região entre a Ponta de Castelhanos e a Ponta Grossa da Marambáia. A interação entre este fluxo e as águas costeiras mais salinas (S ~ 35,4 a 35,6º /oo) se apresentou de forma visível, como uma frente salina. Os valores de salinidade, registrados à leste da Ilha Grande sugerem, que a origem dessa agua de baixa salinidade ê a descarga fluvial na Baía de Sepetiba.Continuous records of temperature and salinity were obtained on the surface waters as function of the horizontal distances around Ilha Grande region, on June 21, 1975; an outflow of less saline (S~33.10º /oo ) and slightly warmer water was detected throughout the region between Ponta de Castelhanos and Ponta Grossa da Marambaia and a visible manifestation of a saline front was observed in the interaction of this outflow with the coastal and more saline water (S~ 35.4 to 35.6º /oo). The recorded salinity values in the east region of Ilha Grande, suggest that the source of less saline water is the runoff in the Baia de Sepetiba

A Quantitative Structure-Activity Relationships (QSAR) Study of Piperine Based Derivatives with Leishmanicidal Activity

Leishmaniasis is a parasitic disease which represents a serious public health problem in developing countries. It is considered a neglected tropical disease, for which there is little initiative in the search for therapeutic alternatives by pharmaceutical industry. Natural products remain a great source of inspiration for obtaining bioactive molecules. In 2010, Singh and co-workers published the synthesis and in vitro biological activity of piperoyl-aminoacid conjugates, as well as of piperine, against cellular cultures of Leishmania donovani. The piperine is an alkaloid isolated from Piper nigrum that has many activities described in the literature. In this work, we present a Quantitative Structure-Activity Study of piperine derivatives tested by Singh and co-workers, aiming to highlight important molecular features for leishmanicidal activity, obtaining a mathematical model to predict the activity of new analogs. Compounds were submitted to a geometry optimization computational procedure at semiempirical level of quantum theory. Molecular descriptors for the set of compounds were calculated by E-Dragon online plataform, followed by a variable selection procedure using Ordered Predictors Selection algorithm. Validation parameters obtained showed that a good QSAR model, based on multiple linear regression, was obtained (R2 = 0.85; Q2 = 0.69), and the following conclusions regarding the structure-activity relationship were elucidated: Compounds with electronegative atoms on different substituent groups of analogs, absence of unsaturation on lateral chain, presence of ester instead of carboxyl, and large volumes (due the presence of additional aromatic rings) trends to increase the activity against promastigote forms of leishmania. DOI: http://dx.doi.org/10.17807/orbital.v9i1.89

A Quantitative Structure-Activity Relationships (QSAR) Study of Piperine Based Derivatives with Leishmanicidal Activity

Leishmaniasis is a parasitic disease which represents a serious public health problem in developing countries. It is considered a neglected tropical disease, for which there is little initiative in the search for therapeutic alternatives by pharmaceutical industry. Natural products remain a great source of inspiration for obtaining bioactive molecules. In 2010, Singh and co-workers published the synthesis and in vitro biological activity of piperoyl-aminoacid conjugates, as well as of piperine, against cellular cultures of Leishmania donovani. The piperine is an alkaloid isolated from Piper nigrum that has many activities described in the literature. In this work, we present a Quantitative Structure-Activity Study of piperine derivatives tested by Singh and co-workers, aiming to highlight important molecular features for leishmanicidal activity, obtaining a mathematical model to predict the activity of new analogs. Compounds were submitted to a geometry optimization computational procedure at semiempirical level of quantum theory. Molecular descriptors for the set of compounds were calculated by E-Dragon online plataform, followed by a variable selection procedure using Ordered Predictors Selection algorithm. Validation parameters obtained showed that a good QSAR model, based on multiple linear regression, was obtained (R2 = 0.85; Q2 = 0.69), and the following conclusions regarding the structure-activity relationship were elucidated: Compounds with electronegative atoms on different substituent groups of analogs, absence of unsaturation on lateral chain, presence of ester instead of carboxyl, and large volumes (due the presence of additional aromatic rings) trends to increase the activity against promastigote forms of leishmania. DOI: http://dx.doi.org/10.17807/orbital.v9i1.89