Synthesis and characterization of hybrid organic/inorganic nanotubes of the imogolite type and their behaviour towards methane adsorption

Imogolite-like nanotubes have been synthesised in which SiCH(3) groups have been introduced in place of the SiOH groups that naturally occur at the inner surface of imogolite, an alumino-silicate with formula (OH)(3)Al(2)O(3)SiOH, forming nanotubes with inner and outer diameter of 1.0 and 2.0 nm, respectively. The new nanotubular material, composition (OH)(3)Al(2)O(3)SiCH(3), has both larger pores and higher specific surface area than unmodified imogolite: it forms as hollow cylinders 3.0 nm wide and several microns long, with a specific surface area of ca. 800 m(2) g(-1) and intriguing surface properties, due to hydrophobic groups inside the nanotubes and hydrophilic Al(OH)Al groups at their outer surface. Adsorption of methane at 30 °C has been studied in the pressure range between 5 and 35 bar on both the new material and unmodified imogolite: it resulted that the new material adsorption capacity is about 2.5 times larger than that of imogolite, in agreement with both its larger pore volume and the presence of a methylated surface. On account of these properties and of its novelty, the studied material has several potential technical applications, e.g. in the fields of gas chromatography and gas separation.     

The use of cation exchange matrix separation coupled with ICP-MS to directly determine platinum group element (PGE) and other trace element emissions from passenger cars equipped with diesel particulate filters (DPF)

Inductively coupled plasma-mass spectrometry coupled with cation exchange matrix separation has been optimised for the direct determination of platinum group element (PGE) and trace element emissions from a diesel engine car. After matrix separation method detection limits of 1.6 ng g(-1) for Pd, 0.4 ng g(-1) for Rh and 4.3 ng g(-1) for Pt were achieved, the method was validated against the certified reference material BCR 723, urban road dust. The test vehicle was fitted with new and aged catalytic converters with and without diesel particulate filters (DPF). Samples were collected after three consecutive New European Driving Cycle (NEDC) of the particulate and "soluble" phases using a home-made sampler optimised for trace element analysis. Emission factors for the PGEs ranged from 0.021 ng km(-1) for Rh to 70.5 ng km(-1) for Pt; when a DPF was fitted, the emission factors for the PGEs actually used in the catalysts dropped by up to 97% (for Pt). Trace element emission factors were found to drop by a maximum of 92% for Ni to a minimum of 18% for Y when a DPF was fitted; a new DPF was also found to cause a reduction of up to 86% in the emission of particulate matter.     

HS-SPME-GC-MS approach for the analysis of volatile salivary metabolites and application in a case study for the indirect assessment of gut microbiota

In this work, a straightforward analytical approach based on headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry was developed for the analysis of salivary volatile organic compounds without any prior derivatization step. With a sample volume of 500 μL, optimal conditions were achieved by allowing the sample to equilibrate for 10 min at 50 °C and then extracting the samples for 10 min at the same temperature, using a carboxen/polydimethylsiloxane fibre. The method allowed the simultaneous identification and quantification of 20 compounds in sample headspace, including short-chain fatty acids and their derivatives which are commonly analysed after analyte derivatization. The proof of applicability of the methodology was performed with a case study regarding the analysis of the dynamics of volatile metabolites in saliva of a single subject undergoing 5-day treatment with rifaximin antibiotic. Non-stimulated saliva samples were collected over 3 weeks from a nominally healthy volunteer before, during, and after antibiotic treatment. The variations of some metabolites, known to be produced by the microbiota and by bacteria that are susceptible to antibiotics, suggest that the study of the dynamics of salivary metabolites can be an excellent indirect method for analysing the gut microbiota. This approach is novel from an analytical standpoint, and it encourages further studies combining saliva metabolite profiles and gut microbiota dynamics.

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New insights into urea action on proteins: a SANS study of the lysozyme case

We present a study on lysozyme dissolved in mixtures of water and urea, which is ubiquitously used as a protein denaturant. Despite the wide use of urea, the basic molecular mechanisms inducing protein unfolding are not still clarified. Small-angle neutron scattering (SANS) experiments have been performed using little amounts of denaturant in solutions in order to investigate the urea effect on lysozyme preceding the unfolding process. A global fit strategy, applied to analyze SANS experiments, provides an estimation of the average composition of the solvent in the close vicinity of the protein surface and the change of the protein-protein interactions due to the presence of urea. In particular, the thermodynamic equilibrium constant responsible for cosolvent balancing between the bulk and solvation layer has been determined. It turns out that urea is preferentially driven to the protein surface, confirming literature results at infinite dilute conditions. SANS data also reveal a possible variation of the protein net charge as a function of urea concentration, opening new perspectives and questions about the protein surface architecture at the first stages of unfolding processes.     

Heavy metals and nutrients in coastal, surface seawaters (Gulf of Trieste, Northern Adriatic Sea): an environmental study by factor analysis

Trace metals and nutrients were monitored voltammetrically and spectrophotometrically during a one-year period (1992/93) in the filtered fraction of coastal surface seawaters sampled with a monthly frequency at 6 different sites in the Gulf of Trieste (Northern Adriatic Sea), to evaluate the degree of pollution in an area receiving industrial, agricultural and urban wastes. The sites devoted to hatcheries of edible mussels are of particular interest. A multivariate statistical analysis of the collected concentration data by the principal component method allows to identify the sources and typology of pollution, and to discriminate between the quality of waters at the different sampling sites. The coastal waters in the Gulf of Trieste seem to be comparable to, or better than, waters of analogous areas in the Mediterranean Sea.     

One-pot synthesis and characterization of size-controlled bimagnetic FePt-iron oxide heterodimer nanocrystals

A one-pot, two-step colloidal strategy to prepare bimagnetic hybrid nanocrystals (HNCs), comprising size-tuned fcc FePt and inverse spinel cubic iron oxide domains epitaxially arranged in a heterodimer configuration, is described. The HNCs have been synthesized in a unique surfactant environment by temperature-driven sequential reactions, involving the homogeneous nucleation of FePt seeds and the subsequent heterogeneous growth of iron oxide. This self-regulated mechanism offers high versatility in the control of the geometric features of the resulting heterostructures, circumventing the use of more elaborate seeded growth techniques. It has been found that, as a consequence of the exchange coupling between the two materials, the HNCs exhibit tunable single-phase-like magnetic behavior, distinct from that of their individual components. In addition, the potential of the heterodimers as effective contrast agents for magnetic resonance imaging techniques has been examined.     

Elucidating 2D Charge-Density-Wave Atomic Structure in an MX–Chain by the 3D-ΔPair Distribution Function Method**

Many solids, particularly low-dimensional systems, exhibit charge density waves (CDWs). In one dimension, charge density waves are well understood, but in two dimensions, their structure and their origin are difficult to reveal. Herein, the 2D charge-density-wave atomic structure and stabilization mechanism in the bromide-bridged Pd compound [Pd(cptn)₂Br]Br₂ (cptn=1R,2R-diaminocyclopentane) is investigated by means of single-crystal X-ray diffraction employing the 3D-Δpair distribution function (3D-ΔPDF) method. Analysis of the diffuse scattering using 3D-ΔPDF shows that a 2D-CDW is stabilized by a hydrogen-bonding network between Br⁻ counteranion and the amine (NH₂) group of the cptn in-plane ligand, and that 3D ordering is prevented due to a weak plane to plane correlation. We extract the effective displacements of the atoms describing the atomic structure quantitatively and discuss the stabilization mechanism of the 2D-CDW. Our study provides a method to identify and measure the key interaction responsible for the dimensionality and stability of the CDW that can help further progress of rational design.     

Complexation of the carbonate, nitrate, and acetate anions with the uranyl dication: density functional studies with relativistic effective core potentials

The structures and vibrational frequencies of uranyl carbonates, [UO2(CO3)n](2-2n) and [(UO2)3(CO3)6]6-, uranyl nitrates, [UO2(NO3)n](2-n), and uranyl acetates, [UO2(CH3COO)n](2-n) (n = 1,2,3) have been calculated by using local density functional theory (LDFT). Only bidentate ligand coordination modes to the uranyl dication have been modeled. The calculated structures and frequencies are compared to available experimental data, including IR, Raman, X-ray diffraction, and EXAFS solution and crystal structure data. The energetics of ligand binding have been calculated using the B3LYP hybrid functional. In general, the structural and vibrational results at the LDFT level are in good agreement with experimental results and provide realistic pictures of solution phase and solid-state behavior. For the [UO2(CO3)3]6- anion, calculations suggest that complexity in the CO3(2-) stretching signature upon complexation is due to the formation of C=O and C-O domains, the latter of which can split by as much as 300 cm(-1). Assessment of the binding energies indicate that the [UO2(CO3)2]2- anion is more stable than the [UO2(CO3)3]4- anion due to the accumulation of excess charge, whereas the tri-ligand species are the most stable in the nitrate and acetate anions.     

Hydroxytyrosol and Oleuropein-Enriched Extracts Obtained from Olive Oil Wastes and By-Products as Active Antioxidant Ingredients for Poly (Vinyl Alcohol)-Based Films

Oxidative stability of food is one of the most important parameters affecting integrity and consequently nutritional properties of dietary constituents. Antioxidants are widely used to avoid deterioration during transformation, packaging, and storage of food. In this paper, novel poly (vinyl alcohol) (PVA)-based films were prepared by solvent casting method adding an hydroxytyrosol-enriched extract (HTyrE) or an oleuropein-enriched extract (OleE) in different percentages (5, 10 and 20% w/w) and a combination of both at 5% w/w. Both extracts were obtained from olive oil wastes and by-products using a sustainable process based on membrane technologies. Qualitative and quantitative analysis of each sample carried out by high performance liquid chromatography (HPLC) and nuclear resonance magnetic spectroscopy (NMR) proved that the main components were hydroxytyrosol (HTyr) and oleuropein (Ole), respectively, two well-known antioxidant bioactive compounds found in Olea europaea L. All novel formulations were characterized investigating their morphological, optical and antioxidant properties. The promising performances suggest a potential use in active food packaging to preserve oxidative-sensitive food products. Moreover, this research represents a valuable example of reuse and valorization of agro-industrial wastes and by-products according to the circular economy model.     

Gonality for stable curves and their maps with a smooth curve as their target

Here we study the deformation theory of some maps f: X → ℙ ^r , r = 1, 2, where X is a nodal curve and f|T is not constant for every irreducible component T of X. For r = 1 we show that the “stratification by gonality” for any subset of with fixed topological type behaves like the stratification by gonality of M _g.