21 research outputs found

    A large neighbourhood based heuristic for two-echelon routing problems

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    In this paper, we address two optimisation problems arising in the context of city logistics and two-level transportation systems. The two-echelon vehicle routing problem and the two-echelon location routing problem seek to produce vehicle itineraries to deliver goods to customers, with transits through intermediate facilities. To efficiently solve these problems, we propose a hybrid metaheuristic which combines enumerative local searches with destroy-and-repair principles, as well as some tailored operators to optimise the selections of intermediate facilities. We conduct extensive computational experiments to investigate the contribution of these operators to the search performance, and measure the performance of the method on both problem classes. The proposed algorithm finds the current best known solutions, or better ones, for 95% of the two-echelon vehicle routing problem benchmark instances. Overall, for both problems, it achieves high-quality solutions within short computing times. Finally, for future reference, we resolve inconsistencies between different versions of benchmark instances, document their differences, and provide them all online in a unified format

    A large neighbourhood search for the 2-Echelon capacitated vehicle routing problem

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    Verschiedene Konzepte der "City Logistic" behandeln die Auslieferung von Waren in dicht besiedelten Ballungsräumen. Einige davon laufen auf eine zweistufige Belieferung der Endkunden hinaus. Die Waren werden dabei in Zwischenlagern, sogenannten Satelliten, von großen Lastwägen auf kleinere Lieferwägen umgeladen. Das grundlegende Prinzip stammt ursprünglich aus Rom, wo große Lastwägen nicht durch die engen Straßen im historischen Stadtkern passen. Die Satelliten liegen meist mit günstiger Verkehrsanbindung am Stadtrand verteilt. Wir zeigen ein mathematisches Modell für dieses "2E-CVRP" (zweistufiges kapazitiertes Vehikel Routing Problem) und optimale Lösungen für kleine Testbeispiele, für die das Problem in annehmbarer Zeit exakt lösbar ist. Weiters zeigen wir die Implementierung einer Metaheuristik mit lokaler Suche, die auch für größere Aufgabenstellungen in relativ kurzer Zeit gute Ergebnisse liefert. Die optimalen Lösungen der kleinen Testbeispiele werden von der Metaheuristik in Bruchteilen der Rechenzeit gefunden, die das exakte Verfahren dafür braucht. Für mehr als die Hälfte der getesteten bekannten Problemstellungen wurden die bisher besten bekannten Lösungen verbessert.City Logistics involves different concepts of delivering goods to customers within densely populated areas. Many of them involve a two-tiered setup, which then is modelled in terms of a Two-Echelon Capacitated Vehicle Routing Problem. Large trucks deliver goods from a depot to intermediate facilities, so called satellites, where freight is transferred to smaller vehicles (city freighters), which then deliver it to customers. The goal is to satisfy all customer demands with the lowest possible costs and driven distance. A local-search metaheuristic based on a Large Neighbourhood Search is developed and implemented to find good solutions within limited computing time. A mixed integer programming model is used to create benchmarks for evaluating the quality of the solutions found by the metaheuristic, at least for small instances, where computing time is sufficient to solve to optimality

    Solid-phase-assisted synthesis of targeting peptide-PEG-oligo(ethane amino)amides for receptor-mediated gene delivery.

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    In the forthcoming era of cancer gene therapy, efforts will be devoted to the development of new efficient and non-toxic gene delivery vectors. In this regard, the use of Fmoc/Boc-protected oligo(ethane amino)acids as building blocks for solid-phase-supported assembly represents a novel promising approach towards fully controlled syntheses of effective gene vectors. Here we report on the synthesis of defined polymers containing the following: (i) a plasmid DNA (pDNA) binding domain of eight succinoyl-tetraethylenpentamine (Stp) units and two terminal cysteine residues; (ii) a central polyethylene glycol (PEG) chain (with twenty-four oxyethylene units) for shielding; and (iii) specific peptides for targeting towards cancer cells. Peptides B6 and c(RGDfK), which bind transferrin receptor and αvβ3 integrin, respectively, were chosen because of the high expression of these receptors in many tumoral cells. This study shows the feasibility of designing these kinds of fully controlled vectors and their success for targeted pDNA-based gene transfer

    Tetraacetonitrilelithium tetraisothiocyanatoborate

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    Establishing a cardiac training group for patients with heart failure: the "HIP-in-WĂĽrzburg" study

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    Background Exercise training in heart failure (HF) is recommended but not routinely offered, because of logistic and safety-related reasons. In 2020, the German Society for Prevention&Rehabilitation and the German Society for Cardiology requested establishing dedicated ""HF training groups."" Here, we aimed to implement and evaluate the feasibility and safety of one of the first HF training groups in Germany. Methods Twelve patients (three women) with symptomatic HF (NYHA class II/III) and an ejection fraction ≤ 45% participated and were offered weekly, physician-supervised exercise training for 1 year. Patients received a wrist-worn pedometer (M430 Polar) and underwent the following assessments at baseline and after 4, 8 and 12 months: cardiopulmonary exercise test, 6-min walk test, echocardiography (blinded reading), and quality of life assessment (Kansas City Cardiomyopathy Questionnaire, KCCQ). Results All patients (median age [quartiles] 64 [49; 64] years) completed the study and participated in 76% of the offered 36 training sessions. The pedometer was worn ≥ 1000 min per day over 86% of the time. No cardiovascular events occurred during training. Across 12 months, NT-proBNP dropped from 986 pg/ml [455; 1937] to 483 pg/ml [247; 2322], and LVEF increased from 36% [29;41] to 41% [32;46]%, (p for trend = 0.01). We observed no changes in exercise capacity except for a subtle increase in peak VO2% predicted, from 66.5 [49; 77] to 67 [52; 78]; p for trend = 0.03. The physical function and social limitation domains of the KCCQ improved from 60 [54; 82] to 71 [58; 95, and from 63 [39; 83] to 78 [64; 92]; p for trend = 0.04 and = 0.01, respectively. Positive trends were further seen for the clinical and overall summary scores. Conclusion This pilot study showed that the implementation of a supervised HF-exercise program is feasible, safe, and has the potential to improve both quality of life and surrogate markers of HF severity. This first exercise experiment should facilitate the design of risk-adopted training programs for patients with HF

    Synthesis and Biological Activity of Organoantimony(III)-Containing Heteropolytungstates

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    Three discrete organoantimony­(III)-containing heteropolytungstates [(PhSb<sup>III</sup>)<sub>4</sub>(<i>A</i>-α-Ge<sup>IV</sup>W<sub>9</sub>O<sub>34</sub>)<sub>2</sub>]<sup>12–</sup> (<b>1</b>), [(PhSb<sup>III</sup>)<sub>4</sub>(<i>A</i>-<i>α</i>-P<sup>V</sup>W<sub>9</sub>O<sub>34</sub>)<sub>2</sub>]<sup>10–</sup> (<b>2</b>), and [{2-(Me<sub>2</sub>NCH<sub>2</sub>C<sub>6</sub>H<sub>4</sub>)­Sb<sup>III</sup>}<sub>3</sub>(<i>B</i>-α-As<sup>III</sup>W<sub>9</sub>O<sub>33</sub>)]<sup>3–</sup> (<b>3</b>) have been synthesized in one-pot reactions in aqueous medium using the appropriate lacunary heteropolyanion precursor and organoantimony­(III) source. Polyanions <b>1</b>–<b>3</b> were isolated as hydrated salts, (NH<sub>4</sub>)<sub>12</sub>[(PhSb<sup>III</sup>)<sub>4</sub>(<i>A</i>-α-Ge<sup>IV</sup>W<sub>9</sub>O<sub>34</sub>)<sub>2</sub>]·20H<sub>2</sub>O (<b>1a</b>), Rb<sub>9</sub>Na­[(PhSb<sup>III</sup>)<sub>4</sub>(<i>A</i>-α-P<sup>V</sup>W<sub>9</sub>O<sub>34</sub>)<sub>2</sub>]·20H<sub>2</sub>O (<b>2a</b>), and Rb<sub>3</sub>[{2-(Me<sub>2</sub>NCH<sub>2</sub>C<sub>6</sub>H<sub>4</sub>)­Sb<sup>III</sup>}<sub>3</sub>(<i>B</i>-α-As<sup>III</sup>W<sub>9</sub>O<sub>33</sub>)]·7H<sub>2</sub>O (<b>3a</b>). The compounds <b>1a</b>–<b>3a</b> were fully characterized in the solid state using infrared (IR) spectroscopy, single-crystal XRD, and thermogravimetric and elemental analyses. The stability of <b>1</b>–<b>3</b> in aqueous solution was confirmed by multinuclear NMR (<sup>1</sup>H, <sup>13</sup>C, <sup>31</sup>P, and <sup>183</sup>W) spectroscopy. Preliminary studies on the biological activity of <b>1</b>–<b>3</b> showed that all three compounds might act as potent antimicrobial agents