A phenomenological representation of iridescent colors in butterfly wings

The representation of the color of butterflies has always been a challenge to artis ts, whatever the medium involved. These colors are highly complex to reproduce, even with the use of computer generated images. This article introduces a new algorithm developed to simulate and generate the iridescent colors that are found on the wings of particular butterflies. The model presented here is based on the scientific description of the butterfly Morpho menelaus . Wing color is determined by interference, diffraction, absorption and reflection of light on microscopic wing's structures. The color varies dependi ng on a combination of the following parameters: view angle, incidence and characteristics of the light source, and surrounding medium. This algorithm which tends to real-time imaging required by computer graphics artis ts still renders images with a fairly high degree of accuracy

A multidisciplinary study unveils the nature of a Roman ink of the I century AD

A multi-instrumental approach combining highly sensitive Synchrotron Radiation-based techniques was used to provide information on the real composition of a dry black ink powder found in a bronze inkwell of the first century AD. The presence of Pb, Cu and Fe in the powder, revealed by XRF and ICP-OES data, leads to raise several hypotheses on their origin. The inkpot and its lid were also investigated by Hand-Held XRF, revealing a bronze alloy (Cu-Sn) with a certain amount of Fe and Pb. The lid was found to be particularly enriched in lead. XRPD, XAS and FTIR measurements showed a substantial presence of silicates and common clay minerals in the ink along with cerussite and malachite, Pb and Cu bearing-carbonates, respectively. These evidences support the hypothesis of an important contamination of the ink sample by the burial environment (soil) and the presence of degradation products of the bronze inkpot. The combined use of IR, Raman, and GC-MS evidenced that the black ink is mainly composed of amorphous carbon deriving from the combustion of organic material mixed with a natural binding agent, Arabic gum

One-pot RAFT and fast polymersomes assembly: a ‘beeline’ from monomers to drug-loaded nanovectors

Rapid and simple routes to functional polymersomes are increasingly needed to expand their clinical or industrial applications. Here we describe a novel strategy where polymersomes are prepared through an in-line process in just a few hours, starting from simple acrylate or acrylamide monomers. Using Perrier's protocol, well-defined amphiphilic diblock copolymers formed from PEG acrylate (mPEGA480), 2-(acryloyloxy)ethyl-3-chloro-4-hydroxybenzoate (ACH) or 2-(3-chloro-4-hydroxybenzamido)ethyl acrylate (CHB), have been synthesised by RAFT polymerisation in one-pot, pushing the monomer conversion for each block close to completion (≥94%). The reaction mixture, consisting of green biocompatible solvents (ethanol/water) have then been directly utilised to generate well-defined polymersomes, by simple cannulation into water or in a more automated process, by using a bespoke microfluidic device. Terbinafine and cyanocobalamine were used to demonstrate the suitability of the process to incorporate model hydrophobic and hydrophilic drugs, respectively. Vesicles size and morphology were characterised by DLS, TEM, and AFM. In this work we show that materials and experimental conditions can be chosen to allow facile and rapid generation drug-loaded polymersomes, through a suitable in-line process, directly from acrylate or acrylamide monomer building blocks

Self-exciting jumps in the oil market: Bayesian estimation and dynamic hedging

In this paper we propose a novel self-exciting jump-diffusion model for oil price dynamics based on a Hawkes-type process. In particular, the jump intensity is stochastic and path dependent, implying that the occurrence of a jump will increase the probability of observing a new jump and this feature of the model aims at explaining the jumps clustering effect. Moreover, volatility is described by a stochastic process, which can jump simultaneously with prices. The model specification is completed by a stochastic convenience yield. In order to estimate the model we apply the two-stage Sequential Monte Carlo (SMC) sampler (Fulop and Li, 2019) to both spot and futures quotations. From the estimation results we find evidence of self-excitation in the oil market, which leads to an improved fit and a better out of sample futures forecasting performance with respect to jump-diffusion models with constant intensity. Furthermore, we compute and discuss two optimal hedging strategies based on futures trading. The optimality of the first hedging strategy proposed is based on the variance minimization, while the second strategy takes into account also the third-order moment contribution in considering the investors attitudes. A comparison between the two strategies in terms of hedging effectiveness is provided

A phenomenological representation of iridescent colors in butterfly wings

The representation of the color of butterflies has always been a challenge to artis ts, whatever the medium involved. These colors are highly complex to reproduce, even with the use of computer generated images. This article introduces a new algorithm developed to simulate and generate the iridescent colors that are found on the wings of particular butterflies. The model presented here is based on the scientific description of the butterfly Morpho menelaus . Wing color is determined by interference, diffraction, absorption and reflection of light on microscopic wing's structures. The color varies dependi ng on a combination of the following parameters: view angle, incidence and characteristics of the light source, and surrounding medium. This algorithm which tends to real-time imaging required by computer graphics artis ts still renders images with a fairly high degree of accuracy

Hawkes Processes in Energy Markets: Modelling, Estimation and Derivatives Pricing

The purpose of the present contribution is to illustrate the extensive use of Hawkes processes in modeling price dynamics in energy markets and to show how they can be applied for derivatives pricing. After a review of the literature devoted to the subject and on the exact simulation of Hawkes processes, we introduce a simple, yet useful, Hawkes-based model for energy spot prices. We present the model under the historical measure and illustrate a structure preserving change of measure, allowing to specify a risk-neutral dynamics. Then, we propose an effective estimation methodology based on particle filtering. Finally, we show how to perform exotic derivatives pricing both through exact simulation and characteristic function inversion techniques

Commodity Asian option pricing and simulation in a 4-factor model with jump clusters

Mean reversion, stochastic volatility, convenience yield and presence of jump clustering are well documented salient features of commodity markets, where Asian options are very popular.We propose amodelwhich takes into account all these stylized features.We first state our model under the historical measure, then, after introducing a structure preserving change of measure, we provide a risk-neutral version of the same model and we show how to price geometric and arithmetic Asian options. To this end, we derive semi-closed formulas for the geometric Asian options price and develop a computationally efficient simulation scheme for the price process, allowing to price the arithmetic counterparts using control variate technique. Finally, we propose a simple econometric experiment to document presence of jump clusters in commodity prices and evaluate the performances of the proposed simulation scheme on some parameter sets calibrated on real data

A phenomenological representation of iridescent colors in butterfly wings

The representation of the color of butterflies has always been a challenge to artists, whatever the medium involved. These colors are highly complex to reproduce, even with the use of computer generated images. This article introduces a new algorithm developed to simulate and generate the iridescent colors that are found on the wings of particular butterflies. The model presented here is based on the scientific description of the butterfly Morpho menelaus. Wing color is determined by interference, diffraction, absorption and reflection of light on microscopic wing's structures. The color varies depending on a combination of the following parameters: view angle, incidence and characteristics of the light source, and surrounding medium. This algorithm which tends to real-time imaging required by computer graphics artists still renders images with a fairly high degree of accuracy

Commodity Asian option pricing and simulation in a 4-factor model with jump clusters

Mean reversion, stochastic volatility, convenience yield and presence of jump clustering are well documented salient features of commodity markets, where Asian options are very popular. We propose a model which takes into account all these stylized features. We first state our model under the historical measure, then, after introducing a structure preserving change of measure, we provide a risk-neutral version of the same model and we show how to price geometric and arithmetic Asian options. To this end, we derive semi-closed formulas for the geometric Asian options price and develop a computationally efficient simulation scheme for the price process, allowing to price the arithmetic counterparts using control variate technique. Finally, we propose a simple econometric experiment to document presence of jump clusters in commodity prices and evaluate the performances of the proposed simulation scheme on some parameter sets calibrated on real data