Efficient heuristics for Median Cycle Problems

This article proposes a number of efficient heuristics for two versions of the Median Cycle Problem. In both versions, the aim is to construct a simple cycle containing a subset of the vertices of a mixed graph. In the first version, the objective is to minimize the cost of the cycle and the cost of assigning vertices not on the cycle to the nearest vertex on the cycle. In the second version, the objective is to minimize the cost of the cycle subject to an upper bound on the total assignment cost. Two heuristics are developed. The first, called the multistart greedy add heuristic, is composed of two main phases. In the first phase, a cycle composed of a limited number of randomly chosen vertices is constructed and augmented by iteratively adding the vertex yielding the largest cost reduction until either no further reduction is possible (for the first version) or the assignment cost is below the upper bound (for the second version). The second phase applies a number of improvement routines. The second heuristic is a random keys evolutionary algorithm. Computational results on a number of benchmark test instances show that the proposed heuristics are highly efficient for both versions of the problem, and superior to the only other available heuristic for these two versions of the problem.     

Sterubin: Enantioresolution and Configurational Stability,Enantiomeric Purity in Nature,and Neuroprotective Activity in Vitro and in Vivo

Alzheimer′s disease (AD) is a neurological disorder with still no preventive or curative treatment. Flavonoids are phytochemicals with potential therapeutic value. Previous studies described the flavanone sterubin isolated from the Californian plant Eriodictyon californicum as a potent neuroprotectant in several in vitro assays. Herein, the resolution of synthetic racemic sterubin ( 1 ) into its two enantiomers, (R)- 1 and (S)- 1 , is described, which has been performed on a chiral chromatographic phase, and their stereochemical assignment online by HPLC-ECD coupling. (R)- 1 and (S)- 1 showed comparable neuroprotection in vitro with no significant differences. While the pure stereoisomers were configurationally stable in methanol, fast racemization was observed in the presence of culture medium. We also established the occurrence of extracted sterubin as its pure (S)-enantiomer. Moreover, the activity of sterubin ( 1 ) was investigated for the first time in vivo, in an AD mouse model. Sterubin ( 1 ) showed a significant positive impact on short- and long-term memory at low dosages.     

Parasitological and Biochemical Efficacy of the Active Ingredients of Allium sativum and Curcuma longa in Schistosoma mansoni Infected Mice

The active ingredients allicin and curcumin have a wide range of actions against fungi, bacteria, and helminths. Therefore, the study was aimed to evaluate the efficacy of allicin (AL) and curcumin (CU) as antischistosomal drugs and their biochemical effects in normal and Schistosoma mansoni-infected mice. Praziquantel (PZQ) was administrated for two successive days while AL or CU was given for two weeks from the week 7th postinfection (PI). The possible effect of different regimens on Schistosoma worms was evaluated by measuring the percentage of the recovered worms, tissue egg load, and oogram pattern. Serum alanine transaminase activity and levels of triglycerides, cholesterol, and uric acid were measured. Liver tissue malondialdehyde and reduced glutathione levels besides, the activities of glutathione-S-transferase, superoxide dismutase and catalase were assessed for the oxidative/antioxidant condition. DNA electrophoresis of liver tissue was used to indicate the degree of fragmentation. There was a significant reduction in the recovered worms and egg load, with a marked change of oogram pattern in all treated groups with PZQ, AL, and CU in comparison with infected-untreated mice. PZQ, AL, and CU prevented most of the hematological and biochemical disorders, as well as significantly improved the antioxidant capacity and enhanced DNA fragmentation in the liver tissue of schistosomiasis mice compared to the infected-untreated group. These promising results suggest that AL and CU are efficient as antischistosomal drugs, and it would be beneficial to test their combination to understand the mechanism of action and the proper period of treatment leading to the best result.     

Offsetting inventory replenishment cycles to minimize storage space

In a recent paper, [Murthy, N.N., Benton, W.C., Rubin, P.A., 2003. Offsetting inventory cycles of items sharing storage. European Journal of Operational Research 150, 304–319] discussed the problem of offsetting inventory replenishment cycles of several items in order to minimize the maximum required storage space. They analyzed the case where replenishment cycles are given integer multiples of a basic period and proposed a heuristic to solve the problem. While they provided a good analysis of the considered problem, the proposed heuristic produces less interesting results. In the following, a simpler, more efficient and easier to implement heuristic is proposed. Numerical results are provided to prove its superiority.     

A Multiple-rule Heuristic for Assembly Line Balancing

This paper introduces a four-rule heuristic method for production/assembly line balancing which seeks to minimize the number of workstations for a given cycle time. To evaluate its performance, the proposed method was compared with 15 other heuristic methods ranging in complexity from random assignment of work elements to Hoffmann's enumeration procedure. The results, based on both randomly generated problems and problems taken from the literature, indicate that the proposed heuristic outperformed other procedures. Further, the suggested method was able to find the optimal solution for 57 (85%) of the 67 literature problems.     

Thin-layer chromatography of triterpenoid acids

Summary Some solvent systems are reported which produce effective resolutions among the triterpenoid acids on silica gel plates according to their hydroxyl content. The use of other solvents succeeded in complete separation of some monohydroxylic acids on kieselguhr plates. The results were applied to an examination of the triterpenoid acid constituents of Nerium oleander, Salvia triloba and Punica granatum leaves, as well as the pods of Albizzia lebbeck.

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Zusammenfassung Es wird über einige Lösungsmittelsysteme für die dünnschichtchromatographische Trennung von Triterpenoidsäuren auf Silicagelplatten entsprechend ihrem Gehalt an Hydroxylgruppen berichtet. Auf Kieselgurplatten konnten einige Monohydroxysäuren getrennt werden. Als praktische Anwendung wurden Triterpenoidsäuren in Blättern von Nerium oleander, Salvia triloba und Punica granatum sowie in den Schoten von Albizzia lebbeck bestimmt.

     

A generic environment for modelling future launch operations—GEM-FLO: a success story in generic modelling

Several NASA programs have been established to study and improve the current launch capability to meet the need for more aggressive space exploration in the future. Numerous launch systems have been proposed by different government and commercial organizations with the potential goal of replacing the Space Shuttle. NASA must evaluate new designs and technologies with the objective of improving upon today's Shuttle cost, performance, and turnaround time, before the government or commercial organizations pursue the large undertaking of a new launch system. To address this issue, the Generic Simulation Environment for Modelling Future Launch Operations (GEM-FLO) was developed to accurately predict processing turnaround times and other effectiveness criteria and support making key business and program decisions. GEM-FLO utilizes a generic modelling paradigm to provide a single platform for modelling different designs, which helped significantly cut the cost of these studies. This paper documents a success story in generic simulation modelling.