Synergistic antimicrobial effect of lactocin AL705 and nisin combined with organic acid salts against Listeria innocua 7 in broth and a hard cheese

The effectiveness of antimicrobial mixtures against Listeria innocua 7, used as a L. monocytogenes surrogate, was investigated in broth and a food system. Synergistic effects were found for nisin (Nis), potassium sorbate (PS), calcium propionate (CP) and sodium lactate (SL), Nis + PS being the most effective binary mixture that exhibited listericidal activity in broth. To assess the effect of adding lactocin AL705 (AL705) to Nis + organic acid salt combinations, tridimensional isobolograms were generated. Sub-MIC combinations of the antimicrobials exerted bactericidal activity against L. innocua 7 after AL705 addition to the binary mixtures. However, when applied on Sardo cheese contaminated with L. innocua 7 (initial inoculum 4.45 ± 0.06 CFU g⁻¹), only Nis + PS + AL705 produced count reductions respect to the control, reaching 3.04 ± 0.35 CFU g⁻¹ counts after 15 days at 15 °C. Ternary combinations containing AL705 showed potential to reduce antimicrobial usages for L. innocua 7 inhibition.     

Democratic dilemmas,planning and Ebenezer Howard's garden city

It is widely acknowledged that Ebenezer Howard's Garden City inspired many important urban planning achievements throughout the world. Using democratic dilemmas as a means of characterizing Garden City allows attention to be drawn to the political ‘work’ that this form of planning undertook. Examination of Garden City's realization at Letchworth and its core democratic values reveals Howard's prescient struggle with the central contradictions of democratic planning, illustrating the difficulties of achieving social goals in planning framed by liberal democracy. While significant gains were made in living conditions through the development of the Garden City, its realization through largely liberal‐based market mechanisms emphasized its physical virtues at the expense of its social goals.     

Laser surface alloying of Gr22 ferritic steel with Ni(Al): Effect of processing parameters on the microstructure and high temperature performance

The aim of this work is modify the surface composition of a Gr22 ferritic steel component with Ni(Al) using a high-power diode laser (HPDL). Two different combinations of parameters were used to obtain a superficial alloy modification macroscopically homogenous, with low porosity and low presence of cracks. From a microscopically point of view the surface presents a band structure due to the rapid cooling process. Isothermal oxidation tests at 640 °C were performed to evaluate the performance of the solution at high temperature. The introduction of Ni(Al) with this technique has allowed to reduce the degradation of the components, without modifying the ferritic structure of the steel.     

Convergence of the approximate free boundary for the multidimensional one-phase Stefan problem

The variational inequality arising from the one-phase multidimensional Stefan problem is discretized by piecewise-linear finite elements in space and by backward-differences in time. Error estimates for the discrete free boundary at each time-step are proved.     

On the numerical approach to a two-phase stefan problem with non-linear flux

This paper is devoted to the numerical analysis of a multidimensional two-phase Stefan problem, with a non-linear flux condition on the fixed boundary; the enthalpy formulation is used. A numerical approach suggested by the theory of non-linear semigroup of contractions in L¹ (Ω) is introduced; some converging algorithms based on the Crandall-Liggett formula and on the non-linear Chernoff formula are studied. The algebraic non-linear equations are solved by a modified Gauss-Seidel method. The results of several numerical tests are exhibited and discussed. This work was supported by Ministero Pubblica Istruzione (fondi per la ricerca scientifica) and by Istituto di Analisi Numerica del C.N.R., Pavia.     

Validation of a geographic information system for the evaluation of the soil radon exhalation potential in South-Tyrol and Veneto, Italy

The PERS (soil radon exhalation potential) project was promoted by ANPA (Italian Environmental Protection Agency) together with the Università Cattolica del Sacro Cuore of Rome: the aim was to produce a geographic information system allowing the discovery of regions with different radon exhalation potential starting from some territorial knowledge. Some environmental measurements were carried out within this project in selected areas in South-Tyrol and Veneto. The measurement of radon in springwater and groundwater as well as in soil gas plays a decisive role for the validation of the algorithm for computing the PERS. Along with technical aspects, a possible use of the PERS method by the Regional Environmental Protection Agencies and by other agencies is discussed with the scope of identifying radon prone areas, as stated in the Italian 'Decreto Legislativo' 26 May 2000, n. 241. Moreover the forecasting power of PERS regarding indoor radon concentration is analysed.