Kinetic Monte Carlo simulation of the classical nucleation process.

We implemented a kinetic Monte Carlo computer simulation of the nucleation process in the framework of the coarse grained scenario of the Classical Nucleation Theory (CNT). The computational approach is efficient for a wide range of temperatures and sample sizes and provides a reliable simulation of the stochastic process. The results for the nucleation rate are in agreement with the CNT predictions based on the stationary solution of the set of differential equations for the continuous variables representing the average population distribution of nuclei size. Time dependent nucleation behavior can also be simulated with results in agreement with previous approaches. The method, here established for the case in which the excess free-energy of a crystalline nucleus is a smooth-function of the size, can be particularly useful when more complex descriptions are required.

Determination of the ion temperature in a stainless steel slab exposed to intense ultrashort laser pulses.

We present an effective approach to determine the amount of energy absorbed by solid samples exposed to ultrashort laser pulses, thus, retrieving the maximum temperature attained by the ion lattice in the picosecond time scale. The method is based on the pyrometric detection of a slow temperature fluctuation on the rear side of a sample slab associated with absorption of the laser pulse on the front side. This approach, successfully corroborated by theoretical calculations, can provide a robust and practical diagnostic tool for characterization of laser-generated warm dense matter.

Simulation-based design study for the passive shielding of the COSINUS dark matter experiment.

The COSINUS (Cryogenic Observatory for SIgnatures seen in Next-generation Underground Searches) experiment aims at the detection of dark matter-induced recoils in sodium iodide (NaI) crystals operated as scintillating cryogenic calorimeters. The detection of both scintillation light and phonons allows performing an event-by-event signal to background discrimination, thus enhancing the sensitivity of the experiment. The choice of using NaI crystals is motivated by the goal of probing the long-standing DAMA/LIBRA results using the same target material. The construction of the experimental facility is foreseen to start by 2021 at the INFN Gran Sasso National Laboratory (LNGS) in Italy. It consists of a cryostat housing the target crystals shielded from the external radioactivity by a water tank acting, at the same time, as an active veto against cosmic ray-induced events. Taking into account both environmental radioactivity and intrinsic contamination of materials used for cryostat, shielding and infrastructure, we performed a careful background budget estimation. The goal is to evaluate the number of events that could mimic or interfere with signal detection while optimising the geometry of the experimental setup. In this paper we present the results of the detailed Monte Carlo simulations we performed, together with the final design of the setup that minimises the residual amount of background particles reaching the detector volume.

[Rubber industry and exposure to carcinogenic chemical agents: an Italian Multicentric Study in Lombardy]. / Stampaggio della gomma ed agenti chimici cancerogeni: l'esperienza dello Studio PPTP-Gomma.

Evaluating the chemical risks at the workplaces, the potential carcinogenic risk is a primary interest. Particularly, in the rubber forming industry the main attention was directed to the hot processing as a possible source of exposure to chemical agents, several of which were classified as carcinogens by the International Agency for Research on Cancer (IARC) and/or the European Union (EU). A study on occupational exposure to chemical carcinogens in the rubber forming industry was planned during last two years, involving a representative sample of firms. In the first step the occupational exposure and the use of preventive measures were evaluated by an investigation at workplace supported with standardized questionnaires. The presence of above 100 chemical agents was registered; 15 agents were classified to carcinogenic or probably carcinogenic to human. The evaluation of exposure by air sampling and monitoring of most substances of interest (acrylonitrile, 1,3-butadiene, styrene, Polycyclic Aromatic Hydrocarbons), demonstrated a low level of occupational exposure, the common hygienic prevention measure being applied.

Free electron laser-driven ultrafast rearrangement of the electronic structure in Ti.

High-energy density extreme ultraviolet radiation delivered by the FERMI seeded free-electron laser has been used to create an exotic nonequilibrium state of matter in a titanium sample characterized by a highly excited electron subsystem at temperatures in excess of 10 eV and a cold solid-density ion lattice. The obtained transient state has been investigated through ultrafast absorption spectroscopy across the Ti M2,3-edge revealing a drastic rearrangement of the sample electronic structure around the Fermi level occurring on a time scale of about 100 fs.

[Lombardy regional project: prevention of occupational tumors]. / Progetto regione lombardia: prevenzione dei tumori professionali.

In Lombardy, the regional project "Prevention of occupational cancers" is ongoing. The main objectives of this project are to identify work environments in which there might be a possible exposure to carcinogenic substances and to elaborate preventive measures. A casual sample of 250 working settings representing the different economic activities has been selected and evaluated. The 10% of the examined workplaces showed a possible exposure to chemical carcinogens. The most common carcinogens were trichloroethylene, preparation of plastics materials containing acrylonitrile-butadiene-stirene, formaldehyde, wood dust, hexavalent chromium, silica and polycyclic aromatic hydrocarbons. Galvanic industries, Bitumen production and placing companies and Plastics processing plants will be studied for environmental and biological monitoring and for the development of preventive measures.

Reflectivity enhancement in titanium by ultrafast XUV irradiation.

The study of highly photo-excited matter at solid state density is an emerging field of research, which is benefitting the development of free-electron-laser (FEL) technology. We report an extreme ultraviolet (XUV) reflectivity experiment from a titanium (Ti) sample irradiated with ultrafast seeded FEL pulses at variable incident photon fluence and frequency. Using a Drude formalism we relate the observed increase in reflectivity as a function of the excitation fluence to an increase in the plasma frequency, which allows us to estimate the free electron density in the excited sample. The extreme simplicity of the experimental setup makes the present approach potentially a valuable complementary tool to determine the average ionization state of the excited sample, information of primary relevance for understanding the physics of matter under extreme conditions.

Crystalline nucleation in undercooled liquids: a Bayesian data-analysis approach for a nonhomogeneous Poisson process.

A Bayesian data-analysis approach to data sets of maximum undercooling temperatures recorded in repeated melting-cooling cycles of high-purity samples is proposed. The crystallization phenomenon is described in terms of a nonhomogeneous Poisson process driven by a temperature-dependent sample nucleation rate J(T). The method was extensively tested by computer simulations and applied to real data for undercooled liquid Ge. It proved to be particularly useful in the case of scarce data sets where the usage of binned data would degrade the available experimental information.