Validation of a method for extraction of polycyclic aromatic hydrocarbons from sewage sludge and analysis by GC-MS

In the present study, the solid–liquid extraction with low temperature purification was validated for the determination of 16 polycyclic aromatic hydrocarbons from sewage sludge by gas chromatography-mass spectrometry. Recoveries ranged 70–114% for naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene and chrysene, while the compounds benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, dibenzo[a,h]anthracene and benzo[g,h,i]perylene showed recoveries of between 40 and 70%. The relative standard deviation was less than 13% for all of the compounds. Negative matrix effect was observed on the 10 compounds with less retention time in the chromatographic analysis and positive matrix effect noticed on the others. The limits of quantification were from 2 to 20 μg kg^?1, about 30 times less than the maximum residue limit allowed in sludge by the European Union. The validated method produced quantification of 11 PAHs in one sludge sample at concentrations ranging 20–2000 μg kg^?1.     

Cine-MR Detection of Geometrical Size Anomalies in the Descending Chest Aorthic Artery for Some Heart Pathologies.

In this MRI work the Fast Gradient-Echo technique has been applied to the detection of the geometrical and elastic properties of the chest aorthic descending artery to check probable troubles in the blood flux which subtend several heart pathologies. The average diameter and the time variations of the aorthic vessel have been measured in the axial scanning plane to minimize the experimental errors. From the analysis of the vessel average diameter and the related root mean square deviation, a parameter named Contractility has been defined, in close relation with the elastic properties of the aorthic vessel. This parameter measured in patients affected from heavy cardiac pathologies such as aorthic arc aneurysm and right atrial mixoma shows remarkable variations when compared to the values obtained in healthy subjects. The use of the Contractility is suggested for a quick MRI determination of these cardiocircolatory pathologies.     

Chaos in the beam equation

We show the existence of chaotic solutions for certain weakly damped linear beam equations with slowly periodic perturbations resting on weakly non-linear elastic bearings.     

Asymptotic expansions obtained by a center manifold theorem

Sunto Viene presentato un nuovo metodo per la determinazione degli sviluppi asintotici della soluzione esterna di sistemi di equazioni differenziali ordinarie singolarmente perturbati. Il metodo proposto, basato sulla teoria geometrica delle perturbazioni singolari e in particolare su un teorema di esistenza di varietà centrale, permette di ottenere le equazioni differenziali che definiscono le variabili « lente » senza la preventiva conoscenza dei corrispondenti sviluppi per le variabili « veloci ». Inoltre, se i sistemi vengono dati con condizioni iniziali, alcune formule che esprimono le corrette condizioni iniziali da assegnare alle equazioni differenziali trovate — formule già note nel « caso stabile » — vengono estese al « caso condizionalmente stabile »; il procedimento qui usato risulta anche più sintetico rispetto a quelli precedentemente proposti. Infine viene studiata un'applicazione ad una classe assai generale di equazioni derivanti dalla cinetica delle reazioni enzimatiche.

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Lavoro eseguito nell'ambito dei programmi del gruppo di ricerca « Equazioni di Evoluzione e Applicazioni », M.P.I., e del Gruppo Nazionale Fisica-Matematica del C.N.R.     

Structural characterization and NMR study of NaNbWO(6) and its proton-exchanged derivatives

The structural characterization of NaNbWO(6), prepared by the ceramic route, has been performed. Electron diffraction has shown the presence of two related phases in a 1:1 ratio, whose lattice parameters correspond to those of the well-known tetragonal tungsten bronzes (TTB) and those of a monoclinically distorted phase. In addition to basic unit cells, the morphology of the two phases has been found to be similar, but they present a slight difference in the W/Nb ratio. (1)H and (23)Na magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectra of NaNbWO(6) and its proton-exchanged derivatives have been interpreted on the basis of the ideal TTB structure. The average structure and the morphology remain unchanged in Na(1-x)H(x)NbWO(6) derivatives. (1)H and (23)Na MAS-NMR spectroscopies have been used to monitor changes produced during exchange processes. It has been shown that the exchange of Na ions is mainly produced, but not exclusively, at tetragonal channels. However, a large amount of Na ions at the pentagonal channels do not exchange with protons, suggesting that these ions are needed to stabilize the TTB-like structure. A tentative distribution of sodium ions in the most-exchanged oxide, deduced from NMR results, approximately (Na(0.46))(p)(Na(0.08))(s)H(0.46)NbWO(6), has been proposed. NMR spectra of Na(1-x)H(x)NbWO(6) indicate that two different OH groups are formed upon exchanging. The study of samples hydrated with D(2)O allowed us to conclude that deuterons of adsorbed water exchange with protons of the two OH groups. The proton-deuteron exchange is slow at room temperature but is strongly enhanced at 90 degrees C. This observation relates to the proton conductivity displayed by exchanged products under a humid atmosphere.     

Adsorption of 2-methylbenzoic acid onto MCM-41 mesoporous material: kinetics and equilibrium studies

Ordered mesoporous molecular sieves are widely studied as alternative materials in areas where sorptive and catalytic applications are required. MCM-41 type mesoporous material was tested as sorbent of 2-methylbenzoic acid (MBA), an aromatic carboxylic acid selected as model molecule for adsorption studies on mesoporous silicas. Adsorption kinetic studies of MBA on MCM-41 type materials were carried out using ethanol solutions at different MBA concentrations. Experimental results followed Langmuir isotherm model showing large adsorption capacity (3.5?g/g). Two kinetic models, the pseudo first- and second-order, were selected to describe the adsorption process and to determine the best model fitting with the experimental data. Kinetic parameters for each kinetic equation were calculated and discussed. It was shown that the MBA adsorption process onto MCM-41 material could be described by the pseudo-second-order equation and that the MCM-41 performs as a suitable adsorbent material.     

Synthesis and antimicrobial activity of 2‐(acyl or carboxyalkyl)‐3‐(H or alkyl or aryl)‐5 (or ‐6 or ‐8)‐monochloro, 7‐fluoro‐substituted‐4H‐1,4‐benzothiazines

A series of 2‐(acyl or carboxyalkyl)‐3‐(H or alkyl or aryl)‐5 (or ‐6 or ‐8)‐monochloro, 7‐fluoro‐substituted‐4H‐1,4‐benzothiazines 3a‐x were prepared to investigate their potential biological activity. In this work the 3a‐w structures are supported with physical and analytical data and the results of their in vitro antimicrobial activity against some strains Gram positive, Gram negative, and Fungi are reported. It was found that compounds 3a, 3d displayed interesting antibacterial activity, whereas compound 3f displayed interesting antifungal activity.