A semiparametric Bayesian joint model for multiple mixed-type outcomes: an application to acute myocardial infarction

We propose a Bayesian semiparametric regression model to represent mixed-type multiple outcomes concerning patients affected by Acute Myocardial Infarction. Our approach is motivated by data coming from the ST-Elevation Myocardial Infarction (STEMI) Archive, a multi-center observational prospective clinical study planned as part of the Strategic Program of Lombardy, Italy. We specifically consider a joint model for a variable measuring treatment time and in-hospital and 60-day survival indicators. One of our main motivations is to understand how the various hospitals differ in terms of the variety of information collected as part of the study. To do so we postulate a semiparametric random effects model that incorporates dependence on a location indicator that is used to explicitly differentiate among hospitals in or outside the city of Milano. The model is based on the two parameter Poisson-Dirichlet prior, also known as the Pitman-Yor process prior. We discuss the resulting posterior inference, including sensitivity analysis, and a comparison with the particular sub-model arising when a Dirichlet process prior is assumed.     

Optimal Control of the Fokker–Planck Equation with Space-Dependent Controls

This paper is devoted to the analysis of a bilinear optimal control problem subject to the Fokker–Planck equation. The control function depends on time and space and acts as a coefficient of the advection term. For this reason, suitable integrability properties of the control function are required to ensure well posedness of the state equation. Under these low regularity assumptions and for a general class of objective functionals, we prove the existence of optimal controls. Moreover, for common quadratic cost functionals of tracking and terminal type, we derive the system of first-order necessary optimality conditions.     

Online coupling of high‐performance liquid chromatography with surface‐enhanced Raman spectroscopy for the identification of historical dyes

High‐performance liquid chromatography (HPLC) is still, today, the technique of choice for the analysis of natural dyes in artistic objects and historical textiles, particularly in association with photodiode array (PDA) detection. In the last two decades, surface‐enhanced Raman spectroscopy (SERS) gained also increasing importance for these investigations thanks to its sensitivity and limited requirements in terms of sample quantity. In favor of SERS, its high specificity in molecular recognition typical of vibrational spectroscopy should be mentioned, whereas this non‐separative technique is obviously disadvantaged in the analyses of mixed chromophores, as is often the case of many natural dyes and also of tints obtained by the combined use of different colorants. An optimized experimental setup combining the two techniques, HPLC‐PDA and SERS, is proposed in the present work, allowing online SERS detection of different dyeing compounds eluted from the HPLC column. Examples are presented concerning some of the colorants most widely used in history, such as morin and luteolin for yellow dyes, alizarin, purpurin, laccaic, kermesic, and carminic acids for red ones, and indigotin for blue tints. Copyright © 2016 John Wiley & Sons, Ltd.     

Radicaux libres crées par irradiation gamma en série bicyclo[2,2,1]heptanique

Above the solid-plastic transition point, well-resolved E.S.R. spectra are recorded when globular compounds are irradiated by γ-rays. We have studied the free radicals observed after γ-irradiation of 15 derivatives of bicyclo[2,2,1]heptan and eight deuterated homologues. The E.S.R. spectra are analysed; they are consistent with the appearance of a free valence localized on one carbon of the cyclohexane ring (C2 for the hydrocarbons, alcohols and chlorides, C3 for the ketones). We note a strong inequivalence for the β-proton couplings and we explain this by a non-planarity of the three bonds surrounding the free radical centre; the deviation from planarity is estimated to be 20–30°. We also observe strong hyperfine interactions with γ-protons. Such long range interactions are inconsistent with the saturated model where spin density is transmitted by spin polarization of localized bonds; they are specific to the unsaturated character of bicyclic compounds which have an enhanced delocalization of the unpaired electron.     

NiO-SiO2 Sol-Gel Nanocomposite Films for Optical Gas Sensor

Recently nanocomposites with sensoring function are becoming a new area of interest in the field of optical gas sensor. In fact, the optical transmittance of nano-particles or thin films has been reported to be changed by atmosphere gases. In particular it was found that NiO, Co₃O₄ and Mn₃O₄ thin films showed reversible decrease in the Vis-NIR absorption due to CO.Aim of this work is the synthesis and the characterization of SiO₂ sol-gel glass films doped with NiO nanocrystals.Films of composition (100 – X)SiO₂-XNiO with X = 10, 20, 40, were obtained by mixing a matrix solution of Si(OC₂H₅)₄ (TEOS) and CH₃Si(OC₂H₅)₃ (MTES) as SiO₂ precursors, with a doping solution containing NiCl₂ as precursor for NiO particles.3-Aminopropyltriethoxysilane (3-APTES), bearing either an ammine group capable of coordinating the Ni ions and hydrolysable siloxane groups for anchoring the metal complex moiety to the silicate matrix, was used as bifunctional ligand.Transmission electron microscopy micrographs showed a uniform distribution of round shaped nanoparticles in film heated at 500°C with a mean diameter of 2.5 nm.The film composition evaluated from Rutherford backscattering spectrometry was in good agreement with the nominal one. As expected the density of the films heated at 1000°C is much higher than the density of the film heated at 500°C due to a residual porosity. Fourier transform infrared spectra also confirmed the presence of residual porosity in the films heated at 500°C.     

Electron beam writing of epoxy based sol–gel materials

We report the use of an epoxy based hybrid sol–gel material as negative resist for electron beam lithography (EBL). The matrix has been prepared starting from 3-glycidoxypropyltrimethoxysilane as specific organic–inorganic precursor and the synthesis has been strictly controlled in order to preserve the epoxy ring and to obtain a proper inorganic cross-linking degree. The film has been exposed to an electron beam, inducing the polymerization of the organic part and generating the film hardening. Preliminary results of a resolution test on the synthesized epoxy based sol–gel material, performed with electron beam lithography, are presented. Structures below 300 nm were achieved. The direct nanopatterning of this hybrid sol–gel system simplify the nanofabrication process and can be exploited in the realization of photonic devices. A demonstration has been carried out doping the hybrid films with commercial Rhodamine 6G and reproducing an already tested laser structure.     

Solving neutral delay differential equations with state-dependent delays

In this paper we consider a class of neutral delay differential equations with state dependent delays. For such equations the possible discontinuity in the derivative of the solution at the initial point may propagate along the integration interval giving rise to subsequent points, called “breaking points”, where the solution derivative is still discontinuous. As a consequence, in a right neighbourhood of each such point we have to face a Cauchy problem where the equation has a discontinuous right-hand side. In this case the existence and the uniqueness of the solution is no longer guaranteed to the right of such points and hence the solution of the neutral equation may either cease to exist or bifurcate. After illustrating why uniqueness and existence of the solution is no longer guaranteed for general state-dependent problems and showing a possible way to detect these occurrences automatically, we explain how to generalize/regularize the problem in order to suitably extend the solution beyond the breaking point. This is important, for example, when exploring numerically the presence of possible periodic orbits.     

A “Density-Based” Algorithm for Cluster Analysis Using Species Sampling Gaussian Mixture Models

We propose a new model for cluster analysis in a Bayesian nonparametric framework. Our model combines two ingredients, species sampling mixture models of Gaussian distributions on one hand, and a deterministic clustering procedure (DBSCAN) on the other. Here, two observations from the underlying species sampling mixture model share the same cluster if the distance between the densities corresponding to their latent parameters is smaller than a threshold; this yields a random partition which is coarser than the one induced by the species sampling mixture. Since this procedure depends on the value of the threshold, we suggest a strategy to fix it. In addition, we discuss implementation and applications of the model; comparison with more standard clustering algorithms will be given as well. Supplementary materials for the article are available online.