Application of multi-way models to the time-resolved fluorescence of polycyclic aromatic hydrocarbons mixtures in water

The time-resolved laser-induced fluorescence of a series of polycyclic aromatic compounds (PAHs) and mixtures of these latter in aqueous solution was measured by means of an apparatus equipped with optical fibers, which allows their real time in situ monitoring. The potential of such spectroscopic technique, yielding 4-way fluorescence data arrays, together with the application of multi-way models to the matricized data, was tested for the resolution of complex aqueous mixtures containing low concentrations of PAHs, as typical fluorescent pollutants in aquatic systems. PARAllel FACtors analysis was employed for the qualitative resolution of PAHs mixtures and for calculating the fluorescence lifetimes of single PAHs; n-way partial least squares analysis was applied for evaluating the concentration of the single PAHs in the aqueous mixtures.     

Constraint-Based Verification of Parameterized Cache Coherence Protocols

We propose a new method for the parameterized verification of formal specifications of cache coherence protocols. The goal of parameterized verification is to establish system properties for an arbitrary number of caches. In order to achieve this purpose we define abstractions that allow us to reduce the original parameterized verification problem to a control state reachability problem for a system with integer data variables. Specifically, the methodology we propose consists of the following steps. We first define an abstraction in which we only keep track of the number of caches in a given state during the execution of a protocol. Then, we use linear arithmetic constraints to symbolically represent infinite sets of global states of the resulting abstract protocol. For reasons of efficiency, we relax the constraint operations by interpreting constraints over real numbers. Finally, we check parameterized safety properties of abstract protocols using symbolic backward reachability, a strategy that allows us to obtain sufficient conditions for termination for an interesting class of protocols. The latter problem can be solved by using the infinite-state model checker HyTech: Henzinger, Ho, and Wong-Toi, A model checker for hybrid systems, Proc. of the 9th International Conference on Computer Aided Verification (CAV'97), Lecture Notes in Computer Science, Springer, Haifa, Israel, 1997, Vol. 1254, pp. 460–463. HyTech handles linear arithmetic constraints using the polyhedra library of Halbwachs and Proy, Verification of real-time systems using linear relation analysis, Formal Methods in System Design, Vol. 11, No. 2, pp. 157–185, 1997. By using this methodology, we have automatically validated parameterized versions of widely implemented write-invalidate and write-update cache coherence protocols like Synapse, MESI, MOESI, Berkeley, Illinois, Firefly and Dragon (Handy, The Cache Memory Book, Academic Press, 1993). With this application, we have shown that symbolic model checking tools like HyTech, originally designed for the verification of hybrid systems, can be applied successfully to new classes of infinite-state systems of practical interest.     

A Technique for Extracting Sub-source Similarities from Information Sources Having Different Formats

In this paper we propose a semi-automatic technique for deriving the similarity degree between two portions of heterogeneous information sources (hereafter, sub-sources). The proposed technique consists in two phases: the first one selects the most promising pairs of sub-sources, whereas the second one computes the similarity degree relative to each promising pair. We show that the detection of sub-source similarities is a special case (and a very interesting one, for semi-structured information sources) of the more general problem of Scheme Match. In addition, we present a real example case to clarify the proposed technique, a set of experiments we have conducted to verify the quality of its results, a discussion about its computational complexity and its classification in the context of related literature. Finally, we discuss some possible applications which can benefit by derived similarities.     

Optimisation of a vehicle energy absorbing steel component with experimental validation

The paper deals with the optimisation of a tapered tubular steel component to be used as an energy-absorbing device in the front structure of a vehicle body. Aim of the optimisation problem is the minimisation of a load uniformity parameter evaluated as the ratio between the maximum and the average crushing loads. The optimisation problem takes into account two design variables describing a tapered geometrical configuration, the diameter of the component at one of its bounds and the tapering length. Two improved geometrical configurations have been found and have been experimentally tested to verify the numerical results with impact velocities up to 10 m/s.     

Integrated methodology for forensic oil spill identification

A new integrated methodology for forensic oil spill identification is presented. It consists of GC-MS analysis, chromatographic data processing, variable-outlier detection, multivariate data analysis, estimation of uncertainties, and statistical evaluation. The methodology was tested on four groups of diagnostic ratios composed of petroleum biomarkers and ratios within homologous PAH categories. Principal component analysis (PCA) was employed and enabled the simultaneous analysis of many diagnostic ratios. Weathering was taken into account by considering the sampling uncertainties estimated from replicate spill samples. Statistical evaluation ensured an objective matching of oil spill samples with suspected source oils as well as classification into positive match, probable match, and nonmatch. The data analysis is further refined if two or more source oils are classified as probable match by using weighted least squares fitting of the principal components, local PCA models, and additional information relevant to the spill case. The methodology correctly identified the source of two spill samples (i.e., crude oils from Oseberg East and Oseberg Field Centre) and distinguished them from closely related source oils.     

Mechanical properties of virgin and recycled polyolefin‐based composite laminates reinforced with jute fabric

Polyolefin‐based composite laminates reinforced with jute fabric were prepared by compression molding and investigated in terms of flexural properties and impact behavior. The use of a virgin polypropylene as the matrix was compared with two polyolefin matrices coming from discarded car bumpers and selected packaging wastes, respectively, and mainly constituted by mixtures of polyethylene and polypropylene resins. The influence of a coupling agent (maleated polypropylene) was always considered in order to improve the interfacial adhesion and, consequently, the composite strength. The effect of this coupling agent, clearly dependent on the amount of polypropylene phase in the overall mixture, was found to be satisfactory only in the case of virgin polypropylene‐based systems. These latter, in presence of maleated polypropylene, have shown higher flexural parameters, lower propagation energy and higher breaking impact load with respect to uncompatibilized ones. Results were supported by morphological observations of impact surfaces, always highlighting a poor adhesion at the reinforcement–matrix interface except in compatibilized virgin polypropylene‐based laminates. POLYM. COMPOS., 36:2022–2029, 2015. © 2014 Society of Plastics Engineer     

On the relationships among latent variables and residuals in PLS path modeling: The formative-reflective scheme

A new approach for the estimation and the validation of a structural equation model with a formative-reflective scheme is presented. The basis of the paper is a proposal for overcoming a potential deficiency of PLS path modeling. In the PLS approach the reflective scheme assumed for the endogenous latent variables (LVs) is inverted; moreover, the model errors are not explicitly taken into account for the estimation of the endogenous LVs. The proposed approach utilizes all the relevant information in the formative manifest variables (MVs) providing solutions which respect the causal structure of the model. The estimation procedure is based on the optimization of the redundancy criterion. The new approach, entitled redundancy analysis approach to path modeling (RA-PM) is compared with both traditional PLS Path Modeling and LISREL methodology, on the basis of real and simulated data.     

Phage-resistant mutants of Lactobacillus delbrueckii may have functional properties that differ from those of parent strains

Three commercial phage sensitive Lactobacillus delbrueckii strains (identified as Ab(1), YSD V and Ib(3)), and four spontaneous phage-resistant mutants isolated from them were tested for their capacity to activate the gut mucosal immune response in mice, as indicated by the numbers of IgA-producing cells. Random Amplified Polymorphic DNA (RAPD) analysis revealed a strong genetic homology between the sensitive strains and their respective derivatives. The phage-resistant mutants exhibited high levels of phage resistance, elevated stability of this phenotype and technological properties comparable to those of their respective parent strains. The tolerance to acidic conditions, bile salts and lysozyme was strain dependent and total cell viability losses as a result of exposure to all three stresses ranged from 2.0 to 3.7 log units. All the strains were highly resistant to a simulated gastric solution of pH 3, while significant additional losses in cell viability were observed when acid treated cells were exposed to bile salts and lysozyme. BALB/c mice received pure cultures of Lb. delbrueckii sensitive and phage-resistant strains for 2, 5 or 7 consecutive days. The ability of the parent strains to activate the small intestine immune response was preserved or enhanced in phage-resistant mutants. The maximal proliferation of IgA(+) cells was observed at day 5 or 7, depending on the strain. Mutants isolated in this study using natural selection strategies had improved phage resistance, adequate technological properties and satisfactory gut mucosal immunostimulation ability, and so would be good candidates for industrial applications in functional foods.