Bayesian optimization using sequential Monte Carlo

We consider the problem of optimizing a real-valued continuous function $f$ using a Bayesian approach, where the evaluations of $f$ are chosen sequentially by combining prior information about $f$, which is described by a random process model, and past evaluation results. The main difficulty with this approach is to be able to compute the posterior distributions of quantities of interest which are used to choose evaluation points. In this article, we decide to use a Sequential Monte Carlo (SMC) approach

ORIGIN OF LIGHT SCATTERING FROM DISORDERED SYSTEMS

Anelastic light scattering is computed numerically for model disordered systems (linear chains and 2-dimensional site and bond percolators), with and without electrical disorder. A detailed analysis of the vibrational modes and of their Raman activity evidences that two extreme mechanisms for scattering may be singled out. One of these resembles scattering from finite size systems, while the other mechanisms originates from spatial fluctuations of the polarizability and is such that modes in even small frequency intervals may have very different Raman activities. As a consequence, the average coupling coefficient $C(\omega)$ is the variance of a zero-average quantity. Our analysis shows that for both linear chains and 2-dimensional percolators the second mechanism dominates over the first, and therefore Raman scattering from disordered systems is essentially due to spatial fluctuations.Comment: 12 pages, Latex, 7 figures available on request

Pumice and lapillus scraps: New national environmental-friendly chance for the production of ceramic tiles

Italian pumice and volcanic lapillus scraps have been used in different percentages as alternative raw materials to foreign feldspars in porcelain stoneware mixtures. The aim of this work was to create naturally colored support to limit the use of artificial dyes while maintaining the technical properties of the reference product. For this purpose, the significant presence of chromophores (Fe and Ti in particular) in by-products from extraction of Italian volcanic pumice and lapillus was exploited. The work was carried out in collaboration with a company: the products were made on a laboratory scale and then they were glazed and fired within the industrial production cycle (48 min, 1210 ◦C). The resulting slip and the fired samples were characterized by measuring the efflux time, density, linear shrinkage, water absorption and tensile strength to evaluate the technological performance. In addition, thermogravimetric analysis (TG), differential thermal analysis (DTA), and optical and mechanical dilatometry were performed to study the thermal behavior of the formulations. The obtained products could be classified as porcelain stoneware and belong to the BIa group (WA 0.5%, B. S.>35 MPa) in accordance with UNI EN 14411 ISO 13006

On the asymmetric zero-range in the rarefaction fan

We consider the one-dimensional asymmetric zero-range process starting from a step decreasing profile. In the hydrodynamic limit this initial condition leads to the rarefaction fan of the associated hydrodynamic equation. Under this initial condition and for totally asymmetric jumps, we show that the weighted sum of joint probabilities for second class particles sharing the same site is convergent and we compute its limit. For partially asymmetric jumps we derive the Law of Large Numbers for the position of a second class particle under the initial configuration in which all the positive sites are empty, all the negative sites are occupied with infinitely many first class particles and with a single second class particle at the origin. Moreover, we prove that among the infinite characteristics emanating from the position of the second class particle, this particle chooses randomly one of them. The randomness is given in terms of the weak solution of the hydrodynamic equation through some sort of renormalization function. By coupling the zero-range with the exclusion process we derive some limiting laws for more general initial conditions.Comment: 22 pages, to appear in Journal of Statistical Physic

Histopatología del osteosarcoma

El diagnóstico del osteosarcoma plantea una serie de problemas específicos. De hecho, se debe tener en cuenta la existencia de diversas variantes, con pronósticos diferentes y que requieren enfoques terapéuticos igualmente distintos. En este mismo sentido, la introducción de nuevos protocolos terapéuticos, incluyendo la quimioterapia preoperatoria, requiere una evaluación histopatológica cuidadosa del especimen a fin de cuantificar la necrosis inducida por la quimioterapia y los márgenes quirúrgicos. El presente estudio analiza las diferentes variantes histopatológicas y los problemas que se relacionan con la evaluación de los efectos de la quimioterapia preoperatoria sobre el especimen resecado.Diagnosis of osteosarcoma presents specific problems. In fact, several and different varieties, presenting different prognosis and requiring different treatments, have to be recognized. Moreover, the adoption of new therapeutic protocols including preoperative chemotherapy, requires a careful histopathological evaluation of the specimen to quantify the chemotherapy-induced necrosis and the surgical margins. This paper analyzes the different histopathological varieties and problems related to the evaluation of the effects on the resected specimen of preoperative chemotherapy