Bioremediation of hydrocarbons contaminated waters and soils: monitoring by luminescent bacteria test

Bioremediation has proven successful in numerous applications to petroleum hydrocarbons or chlorinated aromatic hydrocarbons contaminated soils. There is increasing interest in application of biotoxicity tests for ecological assessment and for supporting management decisions for remediation. Luminescent assays, light-emitting bacteria in particular, can be a suitable tool for environmental analysis, and in vivo luminescence is a rapid and precise indicator of the toxic effects of xenobiotic on micro-organisms. In this study, three different strains of marine bioluminescent bacteria have been employed to follow the changes in biotoxicity occurring during the laboratory scale bioremediation of water and soil samples contaminated by hydrocarbons and collected at an industrial area. The degradation was made by hydrocarbons degrading bacteria, both of commercial sources and isolated from polluted water and soils. The samples were treated for 45 days. The toxicity of the samples, before and after the bioremediation, was determined directly on water samples or on the extracts of soil samples. The yield of extraction by different solvents (acetone, dioxane, ethanol and dichloromethane) was evaluated by the bioluminescent test. The measurements were carried out using a microplate format both for short time of contact (60?minutes, acute toxicity) and for longer time intervals (24 hours, chronic toxicity). The results have been expressed as percentage of inhibition with respect to the blank emission (100% emission). Original and treated samples have been analysed by gas chromatography to assess the hydrocarbons (C?>?12 and Poly Chlorinated Biphenyls, PCB) content. The autochthonous bacteria isolated from polluted samples proved less effective, due to the short time for selection in remediation activity with respect to the commercial ones, but their capacity to degrade long chain hydrocarbons was satisfactory. The presented laboratory study can be applied also in case of on-field conditions.     

A multiscale approach to the analysis of magnetic grid shields and its validation

This paper illustrates the application of the multiple scale expansion theory to the analysis of heterogeneous thin structures employed for the magnetic field shielding and, in particular, the attention is focused on grid shields. These structures are conveniently employed in the mitigation of magnetic fields when the thermal dissipation is a severe restriction. The problem modelling is faced by applying the thin-shell approximation to the Maxwell equations, introducing appropriate interface conditions between the shield surfaces. Starting from this formulation, a homogenisation technique, based on the multiple scale expansion theory, is developed in order to replace the heterogeneous structure with an equivalent homogenous one. The proposed method enables an efficient analysis of magnetic and pure conductive heterogeneous shields with a significant decrease of the computational burden. The results are validated by comparison with a standard modelling approach, when possible, and with experiments developed on specific laboratory set-ups for frequencies up to 2 kHz.     

Chromium(III) determination with 1,5-diphenylcarbazide based on the oxidative effect of chlorine radicals generated from CCl4 sonolysis in aqueous solution.

Oxidation of Cr(III) during sonication in carbonated aqueous solutions saturated with CCl4 leads to the quantitative formation of Cr(VI) and provides a simple and rapid method for spectrophotometric chromium determination with 1,5-diphenylcarbazide. The key to this method is the production of chlorine radicals when aqueous solution saturated with CCl4 is exposed to ultrasonic waves of 40 kHz. The effects of sonication period, CCl4 solution volume, acidity, and interferences were discussed. The time required for a single determination is lower than 2 min. The relative standard deviation obtained for aqueous solutions with 1 microg of Cr was < 2% (N = 10) and the calculated detection limit (3sigma) was 5 ng of Cr.     

On Iterations of the Green Integrals and their Applications to Elliptic Differential Complexes

Convergence of iterations of special Green integrals for overdetermined elliptic linear partial differential operators P of order p ≥ 1 is proved. Using this result we obtain necessary and sufficient conditions for the solvability of the equation Pu = f in the Sobolev space W^p,²(D) and, as a corollary, necessary and sufficient conditions for the vanishing of the first cohomology group of elliptic differential complexes. Also a criterion for the solvability of a P-Neumann problem for elliptic differential operators is proved.     

Projective planes with non-abelian simple collineation group fixing an oval

Dedicated to Professor Luigi A. Rosati on his 70th birthday     

Six-fermion calculation of intermediate-mass Higgs boson production at future {e^+ e^-} colliders

The production of an intermediate-mass Higgs boson in processes of the kind fermions at the energies of future linear colliders is studied. The recently developed and fully automatic algorithm/code ALPHA is used to compute the tree-level scattering amplitudes for the reactions . The code has been interfaced with the Monte Carlo program HIGGSPV/WWGENPV, properly adapted to 6-fermion production, in order to provide realistic results, both in the form of cross sections and event samples at the partonic level. Phenomenological results, that incorporate the effects of initial-state radiation and beamstrahlung, are shown and commented, emphasizing the potentials of full six-fermion calculations for precise background evaluation as well as for detailed studies of the fundamental properties of the Higgs particle. Received: 22 May 1997 / Published online: 20 February 1998     

Gap Functions and Lyapunov Functions

Equilibrium problems play a central role in the study of complex and competitive systems. Many variational formulations of these problems have been presented in these years. So, variational inequalities are very useful tools for the study of equilibrium solutions and their stability. More recently a dynamical model of equilibrium problems based on projection operators was proposed. It is designated as globally projected dynamical system (GPDS). The equilibrium points of this system are the solutions to the associated variational inequality (VI) problem. A very popular approach for finding solution of these VI and for studying its stability consists in introducing the so-called "gap-functions", while stability analysis of an equilibrium point of dynamical systems can be made by means of Lyapunov functions. In this paper we show strict relationships between gap functions and Lyapunov functions.