The Wishart short rate model

We consider a short rate model, driven by a stochastic process on the cone of positive semidefinite matrices. We derive sufficient conditions ensuring that the model replicates normal, inverse or humped yield curves

General closed-form basket option pricing bounds

This article presents lower and upper bounds on the prices of basket options for a general class of continuous-time financial models. The techniques we propose are applicable whenever the joint characteristic function of the vector of log-returns is known. Moreover, the basket value is not required to be positive. We test our new price approximations on different multivariate models, allowing for jumps and stochastic volatility. Numerical examples are discussed and benchmarked against Monte Carlo simulations. All bounds are general and do not require any additional assumption on the characteristic function, so our methods may be employed also to non-affine models. All bounds involve the computation of one-dimensional Fourier transforms; hence, they do not suffer from the curse of dimensionality and can be applied also to high-dimensional problems where most existing methods fail. In particular, we study two kinds of price approximations: an accurate lower bound based on an approximating set and a fast bounded approximation based on the arithmetic-geometric mean inequality. We also show how to improve Monte Carlo accuracy by using one of our bounds as a control variate

Calibration to FX triangles of the 4/2 model under the benchmark approach

We calibrate a novel multifactor stochastic volatility model that includes as special cases the Heston-based model of De Col et al. (J Bank Finance 37(10):3799–3818, 2013) and the 3/2-based model of Baldeaux et al. (J Bank Finance 53:34–48, 2015). Using a dataset on vanilla option quotes in a triangle of currencies, we find that the risk neutral approach typically fails for the calibrated model, in line with the results of Baldeaux et al. (2015)

Calibration to FX triangles of the 4/2 model under the benchmark approach

We calibrate a novel multifactor stochastic volatility model that includes as special cases the Heston-based model of De Col et al. (J Bank Finance 37(10):3799–3818, 2013) and the 3/2-based model of Baldeaux et al. (J Bank Finance 53:34–48, 2015). Using a dataset on vanilla option quotes in a triangle of currencies, we find that the risk neutral approach typically fails for the calibrated model, in line with the results of Baldeaux et al. (2015)

A highly active triterpene derivative capable of biofilm damage to control cryptococcus spp.

Cryptococcus neoformans is an encapsulated yeast responsible for more than 180,000 deaths per year. The standard therapeutic approach against cryptococcosis is a combination of amphotericin B with flucytosine. In countries where cryptococcosis is most prevalent, 5-fluorocytosine is rarely available, and amphotericin B requires intravenous administration. C. neoformans biofilm formation is related to increased drug resistance, which is an important outcome for hospitalized patients. Here, we describe new molecules with anti-cryptococcal activity. A collection of 66 semisynthetic derivatives of ursolic acid and betulinic acid was tested against mature biofilms of C. neoformans at 25 mu M. Out of these, eight derivatives including terpenes, benzazoles, flavonoids, and quinolines were able to cause damage and eradicate mature biofilms. Four terpene compounds demonstrated significative growth inhibition of C. neoformans. Our study identified a pentacyclic triterpenoid derived from betulinic acid (LAFIS13) as a potential drug for anti-cryptococcal treatment. This compound appears to be highly active with low toxicity at minimal inhibitory concentration and capable of biofilm eradication912CAPES - Coordenação de Aperfeiçoamento de Pessoal e Nível SuperiorFAPESP – Fundação de Amparo à Pesquisa Do Estado De São PauloSem informação420276/2016-5; 302637/2017-6; 307191/2016-

Yield from photovoltaic modules under real working situations in west Paraná - Brazil

This study analyzed the external factors that influence the yield obtained from photovoltaic modules (Solarex® - MSX 56), as solar irradiance, temperature, placement angle and dust deposition on the photovoltaic modules  installed at the facilities of the Medianeira campus of the UTFPR, working under real conditions. To obtain the data it was used a datalogger from Campbell Scientific, Inc, model CR23X. It was observed that under solar irradiance below 550 W m-2 the panel did not convert maximum power, and above this value the panel reached saturation levels. Temperature increase led to reduced voltage, and consequently lower module output power, decreasing the efficiency value by nearly 6% at temperatures 15oC above the Standard Test Conditions (STC) temperature. These panels are usually placed at different angles according to local latitude, remaining fixed in that position. In comparison with a horizontally-placed panel, it was obtained a 4-hour increase in yield when the panel reached saturation value. Dust levels reduced electricity production levels by approximately 16%. These factors must be taken into account for placement and maintenance of photovoltaic systems, so they can function efficiently.

Exercise increases insulin signaling in the hippocampus: Physiological effects and pharmacological impact of intracerebroventricular insulin administration in mice

Increasing evidence indicates that physical exercise induces adaptations at the cellular, molecular, and systemic levels that positively affect the brain. Insulin plays important functional roles within the brain that are mediated by insulin-receptor (IR) signaling. In the hippocampus, insulin improves synaptic plasticity, memory formation, and learning via direct modulation of GABAergic and glutamatergic receptors. Separately, physical exercise and central insulin administration exert relevant roles in cognitive function. We here use CF1 mice to investigate (i) the effects of voluntary exercise on hippocampal insulin signaling and memory performance and (ii) whether central insulin administration alters the effects of exercise on hippocampal insulin signaling and memory performance. Adult mice performed 30 days of voluntary exercise on running wheel and afterward both, sedentary and exercised groups, received intracerebroventricular (icv) injection of saline or insulin (0.5-5 mU). Memory performance was assessed using the inhibitory avoidance and water maze tasks. Hippocampal tissue was measured for [U-14C] glucose oxidation and the immunocontent of insulin receptor/signaling (IR, pTyr, pAktser473). Additionally, the phosphorylation of the glutamate NMDA receptor NR2B subunit and the capacity of glutamate uptake were measured, and immunohistochemistry was used to determine glial reactivity. Exercise significantly increased insulin peripheral sensitivity, spatial learning, and hippocampal IR/pTyrIR/pAktser473 immunocontent. Glucose oxidation, glutamate uptake, and astrocyte number also increased relative to the sedentary group. In both memory tasks, 5 mU icv insulin produced amnesia but only in exercised animals. This amnesia was associated a rapid (15 min) and persistent (24 h) increase in hippocampal pNR2B immunocontent that paralleled the increase in glial reactivity. In conclusion, physical exercise thus increased hippocampal insulin signaling and improved water maze performance. Overstimulation of insulin signaling in exercised animals, however, via icv administration impaired behavioral performance. This effect was likely the result of aberrant phosphorylation of the NR2B subunit. © 2010 Wiley-Liss, Inc.Peer Reviewe