Shortest path problem with forbidden paths: The elementary version

This paper addresses the elementary shortest path problem with forbidden paths. The main aim is to find the shortest paths from a single origin node to every other node of a directed graph, such that the solution does not contain any path belonging to a given set (i.e., the forbidden set). It is imposed that no cycle can be included in the solution. The problem at hand is formulated as a particular instance of the shortest path problem with resource constraints and two different solution approaches are defined and implemented. One is a Branch & Bound based algorithm, the other is a dynamic programming approach. Different versions of the proposed solution strategies are developed and tested on a large set of test problems.     

Tools for the eigenvalue distribution in a non-Hermitian setting

Under mild trace norm assumptions on the perturbing sequence, we extend a recent perturbation result based on a theorem by Mirsky. The analysis concerns the eigenvalue distribution and localization of a generic (non-Hermitian) complex perturbation of a bounded Hermitian sequence of matrices. Some examples of application are considered, ranging from the product of Toeplitz sequences to the approximation of PDEs with given boundary conditions. A final discussion on open questions and further lines of research ends the note.     

Diesel particulate abatement via wall-flow traps based on perovskite catalysts

It is probably redundant to stress how extensive are nowadays the attempts to reduce the diesel particulate emissions from automotive and stationary sources. The present paper looks into a technology relied on a catalytic trap based on a SiC wall-flow monolith lined with suitable catalysts for the sake of promoting a more complete and faster regeneration after particulate capture. All the major steps of the catalytic filter preparation are dealt with, including: the synthesis and choice of the proper catalyst and trap materials, the development of an in situ catalyst deposition technique, the bench testing of the derived catalytic wall-flow. The best catalyst selected was the perovskite La0.9K0.1Cr0.9O3-delta. The filtration efficiency and the pressure drop of the catalytic and non-catalytic monoliths were evaluated on a diesel engine bench under various operating conditions.     

Analysis of 21-deoxycortisol, a marker of congenital adrenal hyperplasia, in blood by atmospheric pressure chemical ionization and electrospray ionization using multiple reaction monitoring

Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder mainly caused by 21-hydroxylase deficit (21-OHD). Deletions or mutations of the CYP21 gene induce the impairment of glucocorticoid and mineralcorticoid synthesis. 17-Hydroxyprogesterone (17-OHP) is the hormonal marker in patients, but not in the heterozygous subjects. Excess 17-OHP is hydroxylated into 21-deoxycortisol (21-DF), and therefore 21-DF can be used as a specific marker for diagnosis of heterozygous individuals. We report an analytical method for analysis of 21-DF in blood samples using electrospray (ESI) and atmospheric pressure chemical ionization (APCI), showing that ESI is very sensitive for the analysis of this marker molecule. The multiple reaction monitoring (MRM) approach was used to increase the specificity and the sensitivity of the method.     

Sample handling strategies for the determination of biophenols in food and plants

The analysis of phenols in samples of plant and food origin attracts considerable attention. However, sample handling is often an ignored feature of the analysis. This review highlights the importance of sample extraction in an analysis and the problems that can arise during this step. Many questions remain unanswered and there is a need to more carefully validate extraction efficiencies. Although many new procedures have been developed the use of traditional techniques still dominates.     

Approximating classes of sequences: The Hermitian case

Given a sequence {A_n} of matrices A_n of increasing dimension d_n with d_k>d_q for k>q, k,q∈N, we recently introduced the concept of approximating class of sequences (a.c.s.) in order to define a basic approximation theory for matrix sequences. We have shown that such a notion is stable under inversion, linear combinations, and product, whenever natural and mild conditions are satisfied. In this note we focus our attention on the Hermitian case and we show that is an a.c.s. for {f(A_n)}, if is an a.c.s. for {A_n}, {A_n} is sparsely unbounded, and f is a suitable continuous function defined on R. We also discuss the potential impact and future developments of such a result.     

Optimization of <Emphasis Type="Italic">α</Emphasis>-Terpineol Production by the Biotransformation of <Emphasis Type="Italic">R</Emphasis>-(+)-Limonene and (−)-β-Pinene

The main objective of this work is to present the optimization of the biotransformation of R-(+)-limonene and (−)-β-pinene aiming at the production of α-terpineol by strains of fungal and yeasts previously isolated by our research group using the methodology of experimental design. New optimized experimental data on α-terpineol production by the biotransformation of R-(+)-limonene and (−)-β-pinene using newly isolated microorganisms are reported in this work. Conversion of about 1,700 mg/L was achieved when R-(+)-limonene was used as substrate and the newly isolated strain 05.01.35 as microorganism at the central point of the experimental design, corresponding to a substrate concentration of 1.75%, mass of inoculum of 2 g, and substrate to ethanol volume ratio of 1:1. The same experimental condition led to higher conversions when (−)-β-pinene was used as substrates and the strains coded as 04.05.08 and 01.04.03 as microorganism. Here, conversions of about 770 mg/L were achieved.     

Fractional volume integration in two-dimensional NMR spectra: CAKE, a Monte Carlo approach

Quantitative information from multi-dimensional NMR experiments can be obtained by peak volume integration. The standard procedure (selection of a region around the chosen peak and addition of all values) is often biased by poor peak definition because of peak overlap. Here we describe a simple method, called CAKE, for volume integration of (partially) overlapping peaks. Assuming the axial symmetry of two-dimensional NMR peaks, as it occurs in NOESY and TOCSY when Lorentz-Gauss transformation of the signals is carried out, CAKE estimates the peak volume by multiplying a volume fraction by a factor R. It represents a proportionality ratio between the total and the fractional volume, which is identified as a slice in an exposed region of the overlapping peaks. The volume fraction is obtained via Monte Carlo Hit-or-Miss technique, which proved to be the most efficient because of the small region and the limited number of points within the selected area. Tests on simulated and experimental peaks, with different degrees of overlap and signal-to-noise ratios, show that CAKE results in improved volume estimates. A main advantage of CAKE is that the volume fraction can be flexibly chosen so as to minimize the effect of overlap, frequently observed in two-dimensional spectra.     

The optimal sequential information acquisition structure: A rational utility-maximizing perspective

We consider a rational utility maximizer decision maker (DM) who must gather two pieces of information from a set of multidimensional products before making a choice. We analyze the resulting sequential information acquisition process where the DM tries to find the best possible product subject to his information acquisition constraint. In addition, we introduce publicly observable signals that allow the DM to update his expected utility functions following a standard Bayesian learning rule. Even though it seems intuitively plausible to assume that the transmission of positive and credible information may lead DMs to accept any product signaled more eagerly, this paper illustrates how transmitting credible positive information is not sufficient to decrease the rejection probability faced by the information sender on its set of products. A significant difference in product rejection probabilities arises depending on the characteristic on which signals are issued, as will be illustrated numerically for both risk-neutral and risk-averse DMs.