On a novel optimisation model and solution method for tactical railway maintenance planning

Within the ACEM-Rail project of the European Seventh Framework Programme new measurement and inspection techniques for monitoring the track condition are developed. By means of these new techniques the prediction of future track condition will be highly improved. To our knowledge mid-term maintenance planning is done for projects and preventive tasks, but predictions of the track condition are not incorporated into the planning process up to now. To efficiently utilise this new kind of information one task within the ACEM-Rail project is the development of methods for planning predictive maintenance tasks along with preventive and corrective ones in a mid-term planning horizon. The scope of the mid-term or tactical maintenance planning is the selection and combination of tasks and the allocation of tasks to time intervals where they will be executed. Thereby a coarse maintenance plan is determined that defines which tasks are combined together to form greater tasks as well as the time intervals for executing the selected tasks. This tactical plan serves as the base for booking future track possessions and for scheduling the maintenance tasks in detail. In this paper an algorithmic approach is presented which is able to react on dynamic and uncertain changes due to any track prediction updating. To this end optimisation algorithms are implemented within a rolling planning process, so it is possible to respond to updated information on track condition by adapting the tactical plan. A novel optimisation method is developed to generate cost effective and robust solutions by looking ahead into the future and evaluating different solutions in several scenario

Job order assignment at optimal costs in railway maintenance

Tamping is an important part of railway maintenance. Well tamped ballast reduces track irregularities and increases travel safety and comfort. But if the ballast is in a bad condition, the train speed must be restricted, which leads to delays and penalty costs for the operator. In this paper a novel model for the tamping scheduling problem in a short-term planning horizon is presented. In contrast to other railway maintenance scheduling problems the penalty costs caused by deferring tamping activities are considered in the scheduling process beside the travel costs. Three greedy heuristics are presented and compared in different benchmarks. An outlook discusses issues of interest for further research

The two-echelon capacitated vehicle routing problem: models and math-based heuristics

Multiechelon distribution systems are quite common in supply-chain and logistics. They are used by public administrations in their transportation and traffic planning strategies, as well as by companies, to model own distribution systems. In the literature, most of the studies address issues relating to the movement of flows throughout the system from their origins to their final destinations. Another recent trend is to focus on the management of the vehicle fleets required to provide transportation among different echelons. The aim of this paper is twofold. First, it introduces the family of two-echelon vehicle routing problems (VRPs), a term that broadly covers such settings, where the delivery from one or more depots to customers is managed by routing and consolidating freight through intermediate depots. Second, it considers in detail the basic version of two-echelon VRPs, the two-echelon capacitated VRP, which is an extension of the classical VRP in which the delivery is compulsorily delivered through intermediate depots, named satellites. A mathematical model for two-echelon capacitated VRP, some valid inequalities, and two math-heuristics based on the model are presented. Computational results of up to 50 customers and four satellites show the effectiveness of the methods developed

Job order assignment at optimal costs in railway maintenance

Tamping is an important part of railway maintenance. Well tamped ballast reduces track irregularities and increases travel safety and comfort. But if the ballast is in a bad condition, the train speed must be restricted, which leads to delays and penalty costs for the operator. In this paper a novel model for the tamping scheduling problem in a short-term planning horizon is presented. In contrast to other railway maintenance scheduling problems the penalty costs caused by deferring tamping activities are considered in the scheduling process beside the travel costs. Three greedy heuristics are presented and compared in different benchmarks. An outlook discusses issues of interest for further research

Extreme-Point-based Heuristics for the Three-Dimensional Bin Packing problem

One of the main issues in addressing three-dimensional packing problems is finding an efficient and accurate definition of the points at which to place the items inside the bins, because the performance of exact and heuristic solution methods is actually strongly influenced by the choice of a placement rule. We introduce the extreme point concept and present a new extreme point-based rule for packing items inside a three-dimensional container. The extreme point rule is independent from the particular packing problem addressed and can handle additional constraints, such as fixing the position of the items. The new extreme point rule is also used to derive new constructive heuristics for the three-dimensional bin-packing problem. Extensive computational results show the effectiveness of the new heuristics compared to state-of-the-art results. Moreover, the same heuristics, when applied to the two-dimensional bin-packing problem, outperform those specifically designed for the proble

Identification of a fibrinogen-related protein (FBN9) gene in neotropical anopheline mosquitoes

<p>Abstract</p> <p>Background</p> <p>Malaria has a devastating impact on worldwide public health in many tropical areas. Studies on vector immunity are important for the overall understanding of the parasite-vector interaction and for the design of novel strategies to control malaria. A member of the fibrinogen-related protein family, <it>fbn9</it>, has been well studied in <it>Anopheles gambiae </it>and has been shown to be an important component of the mosquito immune system. However, little is known about this gene in neotropical anopheline species.</p> <p>Methods</p> <p>This article describes the identification and characterization of the <it>fbn9 </it>gene partial sequences from four species of neotropical anopheline primary and secondary vectors: <it>Anopheles darlingi, Anopheles nuneztovari, Anopheles aquasalis</it>, and <it>Anopheles albitarsis </it>(namely <it>Anopheles marajoara</it>). Degenerate primers were designed based on comparative analysis of publicly available <it>Aedes aegypti </it>and <it>An. gambiae </it>gene sequences and used to clone putative homologs in the neotropical species. Sequence comparisons and Bayesian phylogenetic analyses were then performed to better understand the molecular diversity of this gene in evolutionary distant anopheline species, belonging to different subgenera.</p> <p>Results</p> <p>Comparisons of the <it>fbn9 </it>gene sequences of the neotropical anophelines and their homologs in the <it>An. gambiae </it>complex (Gambiae complex) showed high conservation at the nucleotide and amino acid levels, although some sites show significant differentiation (non-synonymous substitutions). Furthermore, phylogenetic analysis of <it>fbn9 </it>nucleotide sequences showed that neotropical anophelines and African mosquitoes form two well-supported clades, mirroring their separation into two different subgenera.</p> <p>Conclusions</p> <p>The present work adds new insights into the conserved role of <it>fbn9 </it>in insect immunity in a broader range of anopheline species and reinforces the possibility of manipulating mosquito immunity to design novel pathogen control strategies.</p

Stability and Antioxidant Activity of Semi-synthetic Derivatives of 4-Nerolidylcatechol.

4-nerolidylcatechol (4-NC) is an unstable natural product that exhibits important antioxidant, anti-inflammatory and other properties. It is readily obtainable on a multi-gram scale through straightforward solvent extraction of the roots of cultivated Piper peltatum or P. umbellatum, followed by column chromatography on the resulting extract. Semi-synthetic derivatives of 4-NC with one or two substituent groups (methyl, acetyl, benzyl, benzoyl) on the O atoms have been introduced that have increased stability compared to 4-NC and significant in vitro inhibitory activity against the human malaria parasite Plasmodium falciparum. Antioxidant and anti-inflammatory properties may be important for the antiplasmodial mode of action of 4-NC derivatives. Thus, we decided to investigate the antioxidant properties, cytotoxicity and stability of 4-NC derivatives as a means to explore the potential utility of these compounds. 4-NC showed high antioxidant activity in the DPPH and ABTS assays and in 3T3-L1 cells (mouse embryonic fibroblast), however 4-NC was more cytotoxic (IC50 = 31.4 µM) and more unstable than its derivatives and lost more than 80% of its antioxidant activity upon storage in solution at &#8722;20 °C for 30 days. DMSO solutions of mono-O-substituted derivatives of 4-NC exhibited antioxidant activity and radical scavenging activity in the DPPH and ABTS assays that was comparable to that of BHA and BHT. In the cell-based antioxidant model, most DMSO solutions of derivatives of 4-NC were less active on day 1 than 4-NC, quercetin and BHA and more active antioxidants than BHT. After storage for 30 days at &#8722;20 °C, DMSO solutions of most of the derivatives of 4-NC were more stable and exhibited more antioxidant activity than 4-NC, quercetin and BHA and exhibited comparable antioxidant activity to BHT. These findings point to the potential of derivatives of 4-NC as antioxidant compounds

Physical Mapping of the \u3ci\u3eAnopheles\u3c/i\u3e (\u3ci\u3eNyssorhynchus\u3c/i\u3e) \u3ci\u3edarlingi\u3c/i\u3e Genomic Scaffolds

The genome assembly of Anopheles darlingi consists of 2221 scaffolds (N50 = 115,072 bp) and has a size spanning 136.94 Mbp. This assembly represents one of the smallest genomes among Anopheles species. Anopheles darlingi genomic DNA fragments of ~37 Kb were cloned, end-sequenced, and used as probes for fluorescence in situ hybridization (FISH) with salivary gland polytene chromosomes. In total, we mapped nine DNA probes to scaffolds and autosomal arms. Comparative analysis of the An. darlingi scaffolds with homologous sequences of the Anopheles albimanus and Anopheles gambiae genomes identified chromosomal rearrangements among these species. Our results confirmed that physical mapping is a useful tool for anchoring genome assemblies to mosquito chromosomes

Bioatividade do óleo essencial de Piper capitarianum (Piperaceae) sobre bactérias patogênicas em laboratório.

A utilização de óleos essenciais vem sendo destaque no ambiente amazônico por diversas atividades biológicas. A espécie vegetal Piper capitarianum apresenta compostos químicos com grande potencial antimicrobiano. O objetivo deste estudo foi avaliar a composição volátil dos óleos Piper capitarianum e seu potencial antimicrobiano sobre bactérias patogênicas em condições de laboratório