Top–down glycolipidomics: fragmentation analysis of ganglioside oligosaccharide core and ceramide moiety by chip‐nanoelectrospray collision‐induced dissociation MS2–MS6

We developed a straightforward approach for high‐throughput top–down glycolipidomics based on fully automated chip‐nanoelectrospray (nanoESI) high‐capacity ion trap (HCT) multistage mass spectrometry (MSⁿ) by collision‐induced dissociation (CID) in the negative ion mode. The method was optimized and tested on a polysialylated ganglioside fraction (GT1b), which was profiled by MS¹ and sequenced in tandem MS up to MS⁶ in the same experiment. Screening of the fraction in the MS¹ mode indicated the occurrence of six [M ? 2H]^2? ions which, according to calculation, support 13 GT1 variants differing in their relative molecular mass due to dissimilar ceramide (Cer) constitutions. By stepwise CID MS²–MS⁵ on the doubly charged ion at m/z 1077.20 corresponding to a ubiquitous GT1b structure, the complete characterization of its oligosaccharide core including the identification of sialylation sites was achieved. Structure of the lipid moiety was further elucidated by CID MS⁶ analysis carried out using the Y₀ fragment ion, detected in MS⁵, as a precursor. MS⁶ fragmentation resulted in a pattern supporting a single ceramide form having the less common (d20 : 1/18 : 0) configuration. The entire top–down experiment was performed in a high‐throughput regime in less than 3 min of measurement, with an analysis sensitivity situated in the subpicomolar range. Copyright © 2009 John Wiley & Sons, Ltd.     

Novel design of multicapillary arrays for high-throughput DNA sequencing

A novel approach to design and optimize linear multicapillary arrays (LMCAs) for high-throughput DNA sequencing is proposed. A significant increase in the number of capillary lanes is obtained due to the use of composite insertions alternately placed between working capillaries of the array and a specific combination of refractive indices of the DNA separation matrix, capillary glass, the insertions and a medium which surrounds the capillary array. Theoretical and experimental studies showed that in conjunction with a dual-side laser illumination scheme, the proposed LMCA design allows a simultaneous uniform irradiation of as many as 550 working capillaries.     

Free-solution electrophoresis of DNA modified with drag-tags at both ends

In end-labeled free-solution electrophoresis (ELFSE), DNA molecules are labeled with a frictional modifier or "drag-tag", allowing their size-based electrophoretic separation in free solution. Among the interesting observations from early work with dsDNA using streptavidin as a drag-tag was that the drag induced by including a streptavidin label at both ends was significantly more than double that from a single streptavidin (Heller, C. et al.., J. Chromatogr. A 1998, 806, 113-121). This finding was assumed to be in error, and subsequent work focused on experiments in which only a single drag-tag is appended to one end of the DNA molecule. Recent theoretical work (McCormick, L. C., Slater, G. W., Electrophoresis 2005, 26, 1659-1667) has examined the contribution of end-effects to the free-solution electrophoretic mobility of charged-uncharged polymer conjugates, reopening the question of enhanced drag from placing a drag-tag at both ends. In this study, this effect is investigated experimentally, using custom-synthesized ssDNA oligonucleotides allowing the attachment of drag-tags to one or both ends, as well as dsDNA PCR products generated with primers appropriate for the attachment of drag-tags at one or both ends. A range of sizes of drag-tags are used, including synthetic polypeptoid drag-tags as well as genetically engineered protein polymer drag-tags. The enhanced drag arising from labeling both ends has been confirmed, with 6-9% additional drag for the ssDNA and 10-23% additional drag for the dsDNA arising from labeling both ends than would be expected from simply doubling the size of the drag-tag at one end. The experimental results for ssDNA labeled at both ends are compared to the predictions of the recent theory of end-effects, with reasonably good quantitative agreement. These experimental findings demonstrate the feasibility of enhancing ELFSE separations by labeling both ends of the DNA molecule, leading to greater resolving power and a wider range of applications for this technique.     

A faster algorithm for a due date assignment problem with tardy jobs

The single-machine due date assignment problem with the weighted number of tardy jobs objective, (the TWNTD problem), and its generalization with resource allocation decisions and controllable job processing times have been solved in O(n⁴) time by formulating and solving a series of assignment problems. In this note, a faster O(n²) dynamic programming algorithm is proposed for the TWNTD problem and for its controllable processing times generalization in the case of a convex resource consumption function.     

基于优先级的进离港航班排序优化问题研究

研究机场终端区进离港航班排序优化问题,对于提高跑道利用率以及降低航班延误损失具有重要意义。本文首先考虑航班运行方式(降落和起飞)、飞机类型以及航班的重要程度(航程是否连续)的不同所造成延误损失的不同,设计三维优先级表反映调度优先等级,并将其转化为延误成本系数。其次,为实现调度的公平性和减轻管制人员的工作负荷,设置允许延误的航班架次约束、邻边约束以及最大限制位置约束。再次,以最小化航班总延误成本为目标建立模型,提出相应的改进蚁群算法(GJAC)进行求解。最后通过数值实验验证所提算法在考虑调度优先等级及上述约束条件的同时能有效减少进离港航班队列的总延误成本。     

Sequencing mixed-model assembly lines: Survey,classification and model critique

Manufacturers in a wide range of industries nowadays face the challenge of providing a rich product variety at a very low cost. This typically requires the implementation of cost efficient, flexible production systems. Often, so called mixed-model assembly lines are employed, where setup operations are reduced to such an extent that various models of a common base product can be manufactured in intermixed sequences. However, the observed diversity of mixed-model lines makes a thorough sequence planning essential for exploiting the benefits of assembly line production. This paper reviews and discusses the three major planning approaches presented in the literature, mixed-model sequencing, car sequencing and level scheduling, and provides a hierarchical classification scheme to systematically record the academic efforts in each field and to deduce future research issues.     

Solving the car sequencing problem via Branch & Bound

In a mixed-model assembly line, varying models of the same basic product are to be produced in a facultative sequence. This results to a short-term planning problem where a sequence of models is sought which minimizes station overloads. In practice – e.g. the final assembly of cars – special sequencing rules are enforced which restrict the number of models possessing a certain optional feature k to r_k within a subsequence of s_k successive models. This problem is known as car sequencing. So far, employed solution techniques stem mainly from the field of Logic and Constraint Logic Programming. In this work, a special Branch & Bound algorithm is developed, which exploits the problem structure in order to reduce combinatorial complexity.