Halide abstraction competes with oxidative addition in the reactions of aryl halides with [Ni(PMenPh(3-n))4]

Density functional theory (DFT) calculations have been used to study the oxidative addition of aryl halides to complexes of the type [Ni(PMenPh(3-n))4], revealing the crucial role of an open shell singlet transition state for halide abstraction. The formation of NiI versus NiII has been rationalised through the study of three different pathways: (i) halide abstraction by [Ni(PMenPh(3-n))3], via an open shell singlet transition state; (ii) SN2-type oxidative addition to [Ni(PMenPh(3-n))3], followed by phosphine dissociation; and (iii) oxidative addition to [Ni(PMenPh(3-n))2]. For the case of [Ni(PMe3)4], a microkinetic model was used to show that these data are consistent with the experimentally-observed ratios of NiI and NiII. Importantly, [Ni(PMenPh(3-n))2] complexes often have little if any role in the oxidative addition reaction because they are relatively high in energy. The behaviour of [Ni(PR3)4] complexes in catalysis is therefore likely to differ considerably from those based on diphosphine ligands in which two coordinate Ni0 complexes are the key species undergoing oxidative addition

The Two-Echelon Capacitated Vehicle Routing Problem

Multi-echelon distribution systems are quite common in supply-chain and logistic systems. They are used by public administrations in their transportation and traffic planning strategies as well as by companies to model their distribution systems. Unfortunately, the literature on com- binatorial optimization methods for multi-echelon distribution systems is very poor. The aim of this paper is twofold. Firstly, it introduces the family of Multi-Echelon Vehicle Routing Problems. Second, the Two-Echelon Capacitated Vehicle Routing Problem, is presented. The Two-Echelon Capacitated Vehicle Routing Problem (2E-CVRP) is an extension of the classical VRP where the delivery passes through intermediate depots (called satellites). As in the classical VRP, the goal is to deliver goods to customers with known demands, minimizing the total delivery cost while considering vehicle and satellites capacity constraints. A mathematical model for 2E-CVRP is presented and some valid in- equalities given, which are able to significantly improve the results on benchmark tests up to 50 customers and 5 satellites. Computational re- sults under different realistic scenarios are presented

The influence of time windows on the costs of urban freight distribution services in city logistics applications

In freight distribution services a required quality level may have a relevant effect on transportation costs. For this reason an evaluation tool is useful to compare different service settings and support the decision, on the base of quantitative indicators. This paper proposes a method for cost evaluation in this context and presents an application to a case study concerning a freight distribution service, which operates on a wide road network having a city centre, a peripheral urban area and a peri-urban rural zone. A simulation method is proposed to obtain real-life scenarios in order to test the method and its indicators. The performance of each indicator has been evaluated in an experimental context to produce realistic test cases, using a trip planning tool and a demand generator. First, the behaviour of the indicators is analysed with regard to the time windows width planned for the service. Then, their ability in estimating the total transportation cost to satisfy all the requests, under different time period profiles, is shown. The results confirm the ability of the set of indicators to predict with a good approximation the transportation costs and therefore to be used in supporting the service quality planning decision

New insights into the Pt(hkl)-alkaline solution interphases from the laser induced temperature jump method

The interfacial properties of platinum single crystal electrodes in contact with alkaline aqueous solutions (pH = 13) have been investigated using the laser induced temperature jump method. This technique offers insights into the net orientation of water dipoles in contact with the electrode surface by recording the coulostatic potential changes after a sudden increase of the interfacial temperature in the submicrosecond time scale. This information is intimately related with the magnitude and sign of charge separation at the interphase and the resulting electric field. In all cases, water shows a net orientation with the hydrogen towards the metal at the lowest investigated potential value, reflected in negative potential transients. The magnitude of the water orientation decreases as the applied potential increases. Eventually, the sign of the potential transient changes, reflecting a reorientation of the water dipoles. The potential where such inversion takes place follows the order Pt(110) < Pt(100) < Pt(111) in accordance with the observed behavior in acid solution and the trend of the work function. For Pt(111) the change of sign of the laser induced potential transient takes place at the onset of hydroxyl adsorption. For the three surfaces, when the pH is decreased to ca. pH = 11, a slow response is detected at potentials values above the inversion point. This could be due to a fast adsorption process or to a slow reorientation of water. After the introduction of steps on the (111) terrace, the inversion shifts to the double layer region, allowing the unambiguous identification of the inversion with a change on the net orientation of the water molecules. For stepped surfaces, a second inversion of the laser induced potential transient is observed that could be related with an effect of the local charge on steps disrupting the ordering of the water network. Comparison with analogous results in acid solution gives information about the local distribution of charges on the stepped surfaces.This work has been financially supported by the MINECO (Spain) project no. CTQ2016-76221-P

A Business Model Assessment and Evaluation Framework for City Logistics Collaborative Strategic Decision Support

Several City Logistics (CL) initiatives have emerged in the last two decades with the aim to reduce the negative externalities of freight distribution in urban areas. Such initiatives can be public and/or private but need to not break or impeach current operations efficiency so to not hinder their profitability. In order to provide business value to CL initiatives and thus fostering their long-term success, it is necessary to understand the decision-making of private companies operating in the urban freight ecosystem. This paper proposes an ex-ante assessment and evaluation framework built around the concept of an ecosystem business modelling that includes the decision-making by CL stakeholders. A theoretical framework previously developed is extended to evaluate a collaborative business model of an Urban Consolidation Centre (UCC). Cost-Benefit analysis (CBA is used estimate the impact of the business model configuration. Finally, research and practice implications are also addressed