Conservative independence-based causal structure learning in absence of adjacency faithfulness

This paper presents an extension to the Conservative PC algorithm which is able to detect violations of adjacency faithfulness under causal sufficiency and triangle faithfulness. Violations can be characterized by pseudo-independent relations and equivalent edges, both generating a pattern of conditional independencies that cannot be modeled faithfully. Both cases lead to uncertainty about specific parts of the skeleton of the causal graph. These ambiguities are modeled by an f-pattern. We prove that our Adjacency Conservative PC algorithm is able to correctly learn the f-pattern. We argue that the solution also applies for the finite sample case if we accept that only strong edges can be identified. Experiments based on simulations and the ALARM benchmark model show that the rate of false edge removals is significantly reduced, at the expense of uncertainty on the skeleton and a higher sensitivity for accidental correlations.     

Direct electroplating of copper on tantalum from ionic liquids in high vacuum: origin of the tantalum oxide layer

In this paper, it is shown that high vacuum conditions are not sufficient to completely remove water and oxygen from the ionic liquid 1-ethyl-3-methylimidazolium chloride. Complete removal of water demands heating above 150 °C under reduced pressure, as proven by Nuclear Reaction Analysis (NRA). Dissolved oxygen gas can only be removed by the use of an oxygen scavenger such as hydroquinone, despite the fact that calculations show that oxygen should be removed completely by the applied vacuum conditions. After applying a strict drying procedure and scavenging of molecular oxygen, it was possible to deposit copper directly on tantalum without the presence of an intervening oxide layer.     

Every Banach Space is Reflexive

The title above is wrong, because the strong dual of a Banach space is too strong to assert that the natural correspondence between a space and its bidual is an isomorphism. However, for many applications it suffices to replace the norm on the first dual by the weak*-structure in order to solve the non-reflexiveness problem [1]. But in this way, only the original vector space is recovered by taking the second dual. In this work we introduce a suitable numerical structure on vector spaces such that Banach balls, or more precisely totally convex modules, arise naturally in duality, namely as a category of Eilenberg–Moore algebras. This numerical structure naturally overlies the weak*-topology on the algebraic dual, so the entire Banach space can be reconstructed as a second dual. Moreover, the isomorphism between the original space and its bidual is the unit of an adjunction between the two-dualisation functors. Notice that the weak*-topology is normable only if it lives on a finite dimensional space; in that case the original space is trivial as well, hence reflexive. So the overlying numerical structure should be something more general than a norm or a seminorm and thus approach theory [2, 3] enters the picture.     

Strategies for detecting fraudulent claims in the automobile insurance industry

Some property and casualty insurers use automated detection systems to help to decide whether or not to investigate claims suspected of fraud. Claim screening systems benefit from the coded experience of previously investigated claims. The embedded detection models typically consist of scoring devices relating fraud indicators to some measure of suspicion of fraud. In practice these scoring models often focus on minimizing the error rate rather than on the cost of (mis)classification. We show that focusing on cost is a profitable approach. We analyse the effects of taking into account information on damages and audit costs early on in the screening process. We discuss several scenarios using real-life data. The findings suggest that with claim amount information available at screening time detection rules can be accommodated to increase expected profits. Our results show the value of cost-sensitive claim fraud screening and provide guidance on how to render this strategy operational.     

Efficient hydrolytic hydrogenation of cellulose in the presence of Ru-loaded zeolites and trace amounts of mineral acid

The hydrolytic hydrogenation of cellulose in the presence of Ru-loaded zeolites and trace amounts of mineral acid shows excellent yields (>90%) for hexitols.     

Extracting organic contaminants from water using the metal-organic framework CrIII(OH)·{O2C-C6H4-CO2}

The water-stable metal-organic framework MIL-53(Cr) is able to adsorb phenol and p-cresol from contaminated water as well as the monomeric sugar D-(-)-fructose. Based on the isotherm for phenol uptake from the liquid phase, it is proposed that the framework breathes to maximize the uptake.     

Oscillating electrochemical reaction in copper-containing imidazolium ionic liquids

An example of an electrochemical oscillator in ionic liquids is presented. Solutions of the ionic liquid 1-ethyl-3-methylimidazolium chloride, [C(2)mim]Cl, which contain both Cu(+) and Cu(2+) ions, show current oscillations during potentiostatic polarization. The oscillations were analyzed by the Quartz Crystal Microbalance (QCM) technique and by Electrochemical Impedance Spectroscopy (EIS). The electrochemical oscillations are of the N-NDR-type, because the low frequency end of the impedance spectrum has negative real impedances. The oscillating current leads to an oscillating growth speed of a metallic copper layer. Besides the presence of both Cu(+) and Cu(2+), the presence of chloride is a necessary, yet not a sufficient, condition for the occurrence of current oscillations. Oscillating currents were also observed for the ionic liquids 1-butyl-3-methylimidazolium chloride and 1-butyl-2,3-dimethylimidazolium chloride, but not for tributyltetradecylphosphonium chloride and N-butylpyridinium chloride.     

A generic stress-strain model for metallic materials with two-stage strain hardening behaviour

Constitutive equations are often used to describe the stress-strain behaviour of metallic materials. This allows the execution of parametric studies for various purposes. Despite the large number of developed stress-strain equations, all frequently applied ones fail to accurately describe a strain hardening behaviour in two distinct stages, which many metallic materials tend to show. For this purpose, the authors developed a new stress-strain model, based on the well-known Ramberg-Osgood equation, which focuses on this two-stage strain hardening behaviour. This article describes the model and its analytical background, along with a graphical method to derive suited model parameters. To validate the proposed methodology, it is applied on stress-strain curves of two high-strength steels, an aluminium alloy and a duplex stainless-steel alloy. Whereas a good correspondence for the stainless-steel alloy is confined to limited plastic strains, excellent agreements are observed for the steels and the aluminium alloy. Following the proposed method, it was possible to obtain model parameter values that give a good correspondence within a detectable strain range.     

How Does Aromaticity Rule the Thermodynamic Stability of Hydroporphyrins?

Several measures of aromaticity including energetic, magnetic, and electron density criteria are employed to show how aromatic stabilization can explain the stability sequence of hydroporphyrins, ranging from porphin to octahydroporphin, and their preferred hydrogenation paths. The methods employed involve topological resonance energies and their circuit energy effects, bond resonance energies, multicenter delocalization indices, ring current maps, magnetic susceptibilities, and nuclear-independent chemical shifts. To compare the information obtained by the different methods, the results have been put in the same scale by using recently proposed approaches. It is found that all of them provide essentially the same information and lead to similar conclusions. Also, hydrogenation energies along different hydrogenation paths connecting porphin with octahydroporphin have been calculated with density functional theory. It is shown by using the methods mentioned above that the relative stability of different hydroporphyrin isomers and the observed inaccessibility of octahydroporphin both synthetically and in nature can be perfectly rationalized in terms of aromaticity.     

Chemistry of Crosslinking Processes for Self‐Healing Polymers

Recent developments in material design have seen an exponential increase of polymers and polymer composites that can repair themselves in response to damage. In this review, a distinction is made between extrinsic materials, where the self‐healing property is obtained by adding healing agents to the material to be repaired, and intrinsic materials, where self‐healing is achieved by the material itself through its chemical nature. An overview of the crosslinking chemistries used in self‐healing materials will be given, discussing the advantages and drawbacks of each system. The review is not only aiming to enable researchers to compare their ongoing research with the state‐of‐the‐art but also to serve as a guide for the newcomers, which allows for a selection of the most promising self‐healing chemistries.