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.     

<Emphasis Type="Italic">J</Emphasis>-embeddable reducible surfaces

Here we classify J-embeddable surfaces, i.e. surfaces whose secant varieties have dimension at most 4, when the surfaces have two components at most.     

Carboxylic groups in mesoporous silica and ethane-bridged organosilica: effect of the surface on the reactivity

Proton-donor ability of carboxylic groups incorporated by co-condensation into SBA-15 and ethane-bridged periodic mesoporous organosilica (PMO) has been studied through IR spectroscopy by dosing ammonia, which forms reversibly COO(-) groups and NH(4)(+) ions. The related equilibrium constants, determined by elaboration of IR data, reveal a lower reactivity of -COOH groups at the surface of PMO than on SBA-15, when the two samples have been outgassed at the same temperature. This finding is interpreted in terms of different dielectric constants and intermolecular interactions engaged with the surface species. Carboxylic groups on ethane-bridged organosilica react with silanols upon thermal treatment at 473 K to form a mixed anhydride species Si-O-C(O)-, at variance with the same groups on SBA-15.     

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.     

Anodic films containing zirconia nanoparticles for corrosion protection of AA1050 aluminum alloy

In this paper, production of anodic aluminum oxide (AAO) is based on a parameter-optimized literature scheme. Highly ordered tubular structures are achieved as a starting point for subsequent modification steps. These steps include sealing of AAO pores. Sealing is here attempted via the spontaneous adsorption of ZrO₂ nanoparticles on preformed AAO. Nanoparticles are synthetized by several different methods, in particular, the innovative water-free microwave-assisted synthesis. These novel water-free nanoparticles are, here for the first time, used for AAO sealing and corrosion protection. Increase in corrosion resistance is tested by electrochemical methods.     

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.     

Active learning for spectroscopic data regression

In this work, we introduce an active learning approach for the estimation of chemical concentrations from spectroscopic data. Its main objective is to opportunely collect training samples in such a way as to minimize the error of the regression process while minimizing the number of training samples used, and thus to reduce the costs related to training sample collection. In particular, we propose two different active learning strategies developed for regression approaches based on partial least squares regression, ridge regression, kernel ridge regression, and support vector regression. The first strategy uses a pool of regressors in order to select the samples with the greatest disagreements among the different regressors of the pool, while the second one is based on adding samples that are distant from the current training samples in the feature space. For support vector regression, a specific strategy based on the selection of the samples distant from the support vectors is proposed. Experimental results on three different real data sets are reported and discussed. Copyright © 2012 John Wiley & Sons, Ltd.     

FirmNet: the scope of firms and the allocation of task in a knowledge-based economy

The increasing knowledge intensity of jobs, typical of a knowledge economy, highlights the role of firms as integrators of know how and skills. As economic activity becomes mainly intellectual and requires the integration of specific and idiosyncratic skills, firms need to allocate skills to tasks and traditional hierarchical control may result increasingly ineffective. In this work, we explore under what circumstances networks of agents, which bear specific skills, may self-organize in order to complete tasks. We use a computer simulation approach and investigate how local interaction of agents, endowed with skills and individual decision-making rules, may produce aggregate network structure able to perform tasks. To design algorithms that mimic individual decision-making, we borrow from computer science literature and, in particular, from studies addressing protocols that produce cooperation in P2P networks. We found that self-organization depends on imitation of successful peers, competition among agents holding specific skills, and the structural features of, formal or informal, organizational networks embedding both professionals, holding skills, and project managers, holding access to jobs.