Observation of calcium aluminate inclusions at interfaces between Ca-treated,Al-killed steels and slags

The evolution of Al₂O₃-CaO inclusions on molten steel surfaces and at molten steel/slag interfaces was observed in-situ through a confocal scanning laser microscope (CSLM) equipped with a gold-image furnace. Depending on the slag chemistry, some of the initially liquid inclusions evolved into irregular Al₂O₃ or SiO₂-enriched inclusions during the separation across the interface. Inclusions were found to cluster at specific locations at the steel/slag interface. Unlike capillary-depression-driven clustering, which is observed on molten steel surfaces, a weak repulsive force opposes fluid-flow-driven clustering at the steel/slag interface. After clustering, the irregular solid inclusions were observed to agglomerate to form large aggregates. This article is based on a presentation given in the Mills Symposium entitled “Metals, Slags, Glasses: High Temperature Properties & Phenomena,” which took place at The Institute of Materials in London, England, on August 22–23, 2002.     

Generalized Bayesian inference in a fuzzy context: From theory to a virtual reality application

A generalized Bayesian inference framework in order to embed fuzzy sets and partial probabilistic information is provided. The general framework of reference is that of coherent conditional probabilities, which allows giving a rigorous interpretation of membership function as a conditional probability, regarded as a function of the conditioning event. The inferential problem needs to be studied in situations where the prior can be partial; moreover, membership and prior can be given on different classes of events. This inferential model is applied for the virtual representation of a female avatar.     

Thermo‐hydraulic analysis of refinery heat exchangers undergoing fouling

A complete, systematic approach is presented for the analysis and characterization of fouling and cleaning in refinery heat exchangers. Bringing together advanced thermo‐hydraulic dynamic models, some new formulations, and a method for dynamic analysis of plant data, it allows: extracting significant information from the data; evaluating the fouling state of the units based on thermal measurements and pressure drops, if available; identifying the range of deposit conductivity leading to realistic pressure drops, if pressure measurements are unavailable; estimating key fouling and ageing parameters; estimating the effectiveness of cleaning and surface conditions after a clean; and predicting thermal and hydraulic performance with good accuracy for other periods/exchangers operating in similar conditions. An industrial case study demonstrates the performance prediction in seamless simulations that include partial and total cleanings for over 1000 days operation. The risks of using thermal effects alone and the significant advantages of including pressure drop measurements are highlighted. © 2016 American Institute of Chemical Engineers AIChE J, 63: 984–1001, 2017     

Independence and Possibilistic Conditioning

There is not a unique definition of a conditional possibility distribution since the concept of conditioning is complex and many papers have been conducted to define conditioning in a possibilistic framework. In most cases, independence has been also defined and studied by means of a kind of analogy with the probabilistic case. In [2,4], we introduce conditional possibility as a primitive concept by means of a function whose domain is a set of conditional events. In this paper, we define a concept of independence associated with this form of conditional possibility and we show that classical properties required for independence concepts are satisfied.     

Impact of deposit aging and surface roughness on thermal fouling: Distributed model

A kinetic model was recently proposed to describe the effect of aging on deposit thermal conductivity and the thermal performance of a shell‐and‐tube heat exchanger undergoing crude oil fouling. The model is adapted for implementation within a dynamic, distributed system with spatial and temporal distributions, relaxing several of the previous assumptions. The evolution of surface roughness is also considered, using conjectural linear and asymptotic functions. Simulations are performed for a single tube representative of a refinery exchanger. The results demonstrate the substantial effects over time of aging and roughness on heat transfer and pressure drop. Roughness effects yield apparently negative initial fouling resistances, as reported in some experimental tests. The importance of accounting for roughness dynamics in short time scale pilot plant scale tests and aging over longer time scales in industrial applications is highlighted. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Medium term aging characterization of enamelled for high frequency applications

This work is related to a medium term research program which aims at studying the behaviour of twisted pair specimens of enamelled copper wires subjected to high frequency sinusoidal voltage waveforms which are used in some advanced types of electrical machines. High frequency voltages due to, for instance, converter operation are not considered in this paper. The following test conditions were adopted: different voltage amplitudes up to 2 kV, selected voltage frequencies up to 5 kHz and test temperatures up to 200 /spl deg/C. The experimental work aims at defining reference-testing procedures and at studying the aging process of enamelled wires which are usually employed in random windings of electrical machines. As final result, a phenomenological model of the aging process, acting in the considered insulation system, is obtained and it is accurately defined on the grounds of the output data. The type of test method adopted and the type of data processing appear worthy to be used in order to characterize enamelled wires in terms of thermoelectrical degradation processes in presence of partial discharges.     

Tracking Hidden Binding Pockets Along the Molecular Recognition Path of l-Trp to Indoleamine 2,3-Dioxygenase 1

Indoleamine 2,3-dioxygenase 1 (IDO1) catalyzes the oxidative cleavage of l -Tryptophan (l -Trp) to yield N-formyl-kynurenine in the first and rate limiting step of the kynurenine pathway. Bioactive metabolites, involved in the regulation of important immunological responses and neurological processes, are then produced by downstream enzymes along the pathway. Inhibitors of IDO1 are being designed and developed as therapeutic agents for immuno-oncology. In this work, we investigated the molecular recognition path of l -Trp to IDO1, integrating biophysical methods with supervised molecular dynamics (suMD) and mutagenesis experiments. Results allowed disclosing for the first time high and low dissociation constants of l -Trp to IDO1, and the presence of a metastable interaction site located at the upper part of a channel whose borders are defined by the EF-loop and the C-terminal part of the JK-loop. Collectively, our results provide new clues for the design of next-generation IDO1 ligands.     

Poly(ADP-ribose)-polymerase-catalyzed hydrolysis of NAD+: QM/MM simulation of the enzyme reaction

Poly(ADP-ribose) polymerase (PARP) is a nuclear enzyme which uses NAD+ as substrate and catalyzes the transfer of multiple units of ADP-ribose to target proteins. PARP is an attractive target for the discovery of novel therapeutic agents and PARP inhibitors are currently evaluated for the treatment of a variety of pathological conditions such as brain ischemia, inflammation, and cancer. Herein, we use the PARP-catalyzed reaction of NAD+ hydrolysis as a model for gaining insight into the molecular details of the catalytic mechanism of PARP. The reaction has been studied in both the gas-phase and in the enzyme environment through a QM/MM approach. Our results indicate that the cleavage reaction of the nicotinamide-ribosyl bond proceeds through an SN2 dissociative mechanism via an oxacarbenium transition structure. These results confirm the importance of the structural water molecule in the active site and may constitute the basis for the design of transition-state-based PARP inhibitors.     

Metal complexes containing allenylidene and higher cumulenylidene ligands: a theoretical perspective

Transition metal complexes containing unsaturated carbenes have enjoyed a recent surge in research interest. In addition to showing potential as molecular wires and as components of opto-electronic materials, they provide multifaceted reactive sites for organic synthesis. In this Account, we describe results of recent theoretical studies that delineate the main features of electronic structure and bonding in allenylidenes and higher cumulenylidene complexes, [L(m)M]═C(═C)(n)═CR(1)R(2) (where L represents the ligand, M the metal, and n ≥ 1). Although free cumulenylidene ligands, :C(═C)(n)═CR(1)R(2), are extremely unstable and reactive species, they can be stabilized by coordination to a transition metal. The σ-donation of the electron lone pair on the terminal carbon atom to an empty metal d-orbital, together with the simultaneous π back-donation from filled metal d(π)-orbitals to empty cumulene π* system orbitals, leads to the formation of a strong M═C bond with multiple character. Density functional theory studies on the model systems [(CO)(5)Cr(═C)(n)CH(2)] and [trans-Cl(PH(3))(4)Ru(═C)(n)CH(2)](+) (where n = 1-9) have been useful in interpreting the structural and spectroscopic properties and the reactivity of this class of complexes. Geometry optimizations significantly contributed to the generalization of the sparse structural data available for allenylidene, butatrienylidene, and pentatetraenylidene complexes to higher cumulenylidene complexes (with up to eight carbon atoms in the chain), which show a clear structural trend. In particular, the geometries of all even-chain cumulenes are consistent with an almost purely cumulenic structure, whereas the geometries of odd-chain cumulenes present a significant polyyne-like carbon-carbon bond length alternation. The calculated bond dissociation energies (BDEs) of the cumulenylidene ligand remain almost constant on lengthening the cumulene chain. These BDEs indicate that there is no thermodynamic upper limit to the cumulene chain length and suggest that the synthetic difficulties in preparing higher cumulenylidenes are due to an increase in reactivity. The calculated charges on the carbon atoms show no significant polarization along the cumulene chain, indicating that charge distribution is not important in determining the regioselectivity of either electrophilic or nucleophilic attack, which is instead determined by frontier orbital factors. The breakdown of the contributions from the metal and the carbon atoms along the chain to the HOMO and LUMO shows that the HOMO has contributions mainly from the metal and the carbon atoms in even positions along the chain (C(2), C(4), C(6), and higher). In contrast, the LUMO has contributions mainly from the carbon atoms in odd positions along the chain (C(1), C(3), C(5), and higher), thus explaining the experimentally observed regioselectivity of electrophilic and nucleophilic attacks, which are directed, respectively, to even and odd positions of the cumulenylidene chain. The study of the electronic structure of cumulenylidenes has allowed us not only to give a consistent rationale for the main structural and spectroscopic properties and for the reactivity of this emerging class of compounds but also to predict the effect of ancillary ligands on the metal center or substituents on the carbon end. The result is a useful guide to new developments in the still-underexplored fields of this fascinating class of compounds.     

Non-Covalent Synthesis of Metal Oxide Nanoparticle–Heparin Hybrid Systems: A New Approach to Bioactive Nanoparticles

Heparin has been conjugated to Fe₃O₄, Co₃O₄, and NiO nanoparticles (NPs) through electrostatic interactions, producing colloidal suspensions of hybrid metal oxide heparin NPs that are stable in water. Negative zeta potentials and retention of heparin’s ability to capture toluidine blue indicate that heparin’s negative charges are exposed on the surface of the coated NPs. IR results confirmed the formation of nanohybrids as did NMR experiments, which were also interpreted on the basis of toluidine blue tests. Transmission electron microscopy results revealed that the heparin coating does not modify the shape or dimension of the NPs. Dynamic light scattering and negative zeta potential measurements confirmed that heparin surface functionalisation is an effective strategy to prevent NP aggregation.