185 resultados para G-Graph
Resumo:
Exam timetabling is one of the most important administrative activities that takes place in academic institutions. In this paper we present a critical discussion of the research on exam timetabling in the last decade or so. This last ten years has seen an increased level of attention on this important topic. There has been a range of significant contributions to the scientific literature both in terms of theoretical andpractical aspects. The main aim of this survey is to highlight the new trends and key research achievements that have been carried out in the last decade.We also aim to outline a range of relevant important research issues and challenges that have been generated by this body of work.
We first define the problem and review previous survey papers. Algorithmic approaches are then classified and discussed. These include early techniques (e.g. graph heuristics) and state-of-the-art approaches including meta-heuristics, constraint based methods, multi-criteria techniques, hybridisations, and recent new trends concerning neighbourhood structures, which are motivated by raising the generality of the approaches. Summarising tables are presented to provide an overall view of these techniques. We discuss some issues on decomposition techniques, system tools and languages, models and complexity. We also present and discuss some important issues which have come to light concerning the public benchmark exam timetabling data. Different versions of problem datasetswith the same name have been circulating in the scientific community in the last ten years which has generated a significant amount of confusion. We clarify the situation and present a re-naming of the widely studied datasets to avoid future confusion. We also highlight which research papershave dealt with which dataset. Finally, we draw upon our discussion of the literature to present a (non-exhaustive) range of potential future research directions and open issues in exam timetabling research.
Resumo:
Alzheimer's disease (AD) is the most common cause of dementia in the elderly. Epidemiological and molecular genetic studies have shown the existence of several genes associated with increased risk of AD, the major genetic susceptibility locus coding for apolipoprotein E (apoE). A polymorphism in the myeloperoxidase gene (MPO) has previously been associated with AD susceptibility. However, results in the literature are controversial and seem to be dependent on several factors such as gender, apoE polymorphism or the genetic structure of the population. We investigated MPO G-463A and apoE polymorphism in 265 cases and 246 controls from the ApoEurope Study. In females, we found a significant association between MPO genotype and AD (P=0.034), GG genotype frequency being lower in cases (52.4%) as compared to controls (64.2%). In men, there was no significant effect of MPO polymorphism. No interaction was found between MPO polymorphism and apoE epsilon 4 allele. In conclusion, the G-463A polymorphism of MPO was statistically associated with AD in a gender-specific manner. However, given the low significance of P value we suggest no causal effect of the MPO gene in AD, as also evidenced in a recent meta-analysis. Our results support the hypothesis of a possible linkage disequilibrium between the MPO G-463A gene polymorphism and another functional variant involved in AD.
Resumo:
A total synthesis of phomactin G (3), which is a central intermediate in the biosynthesis of phomactin A (5) in Phoma sp. is described. The synthesis is based on a Cr(II)/Ni(II) macrocyclisation from the aldehyde vinyl iodide 9, leading to 16, followed by sequential conversion of 16 into the -epoxide 21 and the ketone 25 which, on deprotection, led to (±)-phomactin G. Phomactin G (3) shares an interesting structural homology with phomactin D (2), the most potent PAF-antagonist metabolite in Phoma sp. It is most likely converted into phomactin A (5), by initial allylic oxidation to the transient -alcohol phomactin structure 4, known as Sch 49028, followed by spontaneous pyran ring formation.
Resumo:
OBJECTIVE: To investigate the influence of culture with G-CSF GM-CSF and TNFalpha on neutrophil apoptosis, comparing neutrophils from SLE patients with rheumatoid arthritis (RA) patients and healthy control subjects. METHODS: Neutrophils were isolated from SLE (n= 10), RA (n= 10) and healthy control subjects (n= 10), and cultured with two different concentrations of G-CSF, GM-CSF and TNFalpha. Proportion of apoptotic neutrophils at T=0, T=2hrs and T=24hrs was measured using FITC-labelled annexinV and flow cytometry. RESULTS: Significantly more neutrophils were apoptotic at T=0 in the SLE subjects than in the other groups (median, range--Control 3.5% (0.3-7.9) SLE 9.5% (2.9-29.1) RA 3.0% (0.4-23.0) p