Exploring Consumer Evaluations of e-Services: A Portal Site

in International Journal of Service Industry Management (2001), 12(4), 359-377

Exploring Local Item Dependency for Items Clustered around Common Reading Passage in PIRLS Data

Conference (2010)

Exploring new achievements in olefin metathesis catalysts. Part 2 - Compelling innovations in ruthenium complexes

in Chimica Oggi = Chemistry Today (2009), 27(3), 13-16

This part of the survey introduces recent developments on de novo designed types of ruthenium complexes used as promoters in olefin metathesis reactions. Encompassing diversity-oriented initiators not ... [more ▼]

This part of the survey introduces recent developments on de novo designed types of ruthenium complexes used as promoters in olefin metathesis reactions. Encompassing diversity-oriented initiators not illustrated in Part 1, in this second part of the review emphasis is placed on the leading role played by distinct ligands in an exquisite control of metathesis reactions. [less ▲]

Exploring Structure and Reformulations in Different Integer Programming Algorithms

Doctoral thesis (2004)

In this thesis we consider four topics all related to using problem reformulations in order to solve integer programs, i.e. optimization problems in which the decision variables must be integer. We first ... [more ▼]

In this thesis we consider four topics all related to using problem reformulations in order to solve integer programs, i.e. optimization problems in which the decision variables must be integer. We first consider the polyhedral approach. We start by addressing the ques- tion of lifting valid inequalities, i.e. finding a valid inequality for a set Y from the knowledge of a valid inequality for a lower-dimensional restriction X of Y . We simplify and clarify the presentation of the procedure. This allows us to derive conditions under which the computation of the lifting is tractable. The second topic is the study of valid inequalities for the single node flow set. The single node flow set is the problem obtained by considering one node of a fixed charge network flow problem. We derive valid inequalities for this set and various generalizations. Our approach is a systematic procedure using only basic tools of integer programming: fixing and complementing variables, mixed- integer rounding and lifting. The method allows us to explain and generate a large range of inequalities describing the convex hull of such sets. The last two topics are based on non-standard approaches for integer pro- gramming. We first show how the group relaxation approach can be used to provide reformulations for the integral basis method. This is based on a study of extended formulations for the group problem. We present four extended for- mulations and show that the projections of three of these formulations provide the convex hull of the original group problem. Initial computational tests of the approach are also reported. Finally we consider a problem that is difficult for the standard branch-and- bound approach even for small instances. A reformulation based on lattice basis reduction is known to be more effective. However the step to compute the re- duced basis is O(n4) and becomes a bottleneck for small to medium instances. By using the structure of the problem, we show that we can decompose the problem and obtain the basis by taking the kronecker product of two smaller bases easier to compute. Furthermore, if the two small bases are reduced, the kronecker product is also reduced up to a reordering of the vectors. Computa- tional results show the gain from such an approach. [less ▲]

Exploring the Antarctic soil metagenome as a source of novel cold-adapted enzymes and genetic mobile elements

in Revista Argentina de Microbiologia (2011)

Metagenomic library PP1 was obtained from Antarctic soil samples. Both functional and genotypic metagenomic screening were used for the isolation of novel cold-adapted enzymes with potential applications ... [more ▼]

Metagenomic library PP1 was obtained from Antarctic soil samples. Both functional and genotypic metagenomic screening were used for the isolation of novel cold-adapted enzymes with potential applications, and for the detection of genetic elements associated with gene mobilization, respectively. Fourteen lipase/esterase-, 14 amylase-, 3 protease-, and 11 cellulase-producing clones were detected by activity-driven screening, with apparent maximum activities around 35 °C for both amylolytic and lipolytic enzymes, and 35-55 °C for cellulases, as observed for other cold-adapted enzymes. However, the behavior of at least one of the studied cellulases is more compatible to that observed for mesophilic enzymes. These enzymes are usually still active at temperatures above 60 °C, probably resulting in a psychrotolerant behavior in Antarctic soils. Metagenomics allows to access novel genes encoding for enzymatic and biophysic properties from almost every environment with potential benefits for biotechnological and industrial applications. Only intI- and tnp-like genes were detected by PC R, encoding for proteins with 58-86%, and 58-73% amino acid identity with known entries, respectively. Two clones, BAC 27A-9 and BAC 14A-5, seem to present unique syntenic organizations, suggesting the occurrence of gene rearrangements that were probably due to evolutionary divergences within the genus or facilitated by the association with transposable elements. The evidence for genetic elements related to recruitment and mobilization of genes (transposons/integrons) in an extreme environment like Antarctica reinforces the hypothesis [less ▲]

Exploring the Diversity of Fair Trade Social Enterprises

E-print/Working paper (2010)

Fair trade (FT) organisations have been quite early taken as examples of social enterprises (SE) and have contributed to the shaping of the SE concept. The goal of this article is to examine more deeply ... [more ▼]

Fair trade (FT) organisations have been quite early taken as examples of social enterprises (SE) and have contributed to the shaping of the SE concept. The goal of this article is to examine more deeply, both at a conceptual and at an empirical level, to what extent FT organisations can be considered as social enterprises. First, we introduce different theoretical frameworks of SE and examine FT in the context of each of these frameworks. In a second step, we use an empirical study on fair trade social enterprises (FTSEs) across four European countries to illustrate and deepen the links between FT and SE, focusing on the goals and the governance structures of FTSEs. It appears that all FTSEs combine in some way economic, social and sometimes also political goals. FTSEs are thus in line with the "hybrid-goal" nature of SEs. FTSEs' governance is also quite specific and often innovative in terms of organisational architecture and stakeholders' involvement. Some FTSEs are closer to the European – participatory – approach of social enterprise, while others are closer to US – individual – approaches. Finally, the governance structures of FTSEs seem to reflect quite well their goal mix. This article provides a more solid basis for the often implicit link between FT and SE. Future researches could use our work to explore specific topics of the SE literature (e.g. stakeholders' involvement) in the context of FT. The FT example could also be used to examine further the shifting boundaries of the SE reality. The originality of this article is to apply the SE concept to a specific field and to show how, within this field, there is at the same time (1) a diversity of organisations, reflecting the diversity of SE approaches and (2) a range of specific features (especially in terms of goal mix and governance) distinguishing SEs from other types of organisations operating in the same field. [less ▲]

Exploring the Formation Pathways of DNA G-Quadruplex Architectures

Conference (2007, September 07)

Guanine-rich DNA strands can form the so-called G-quadruplex architectures due to the formation of quartets of guanines linked by 8 hydrogen bonds. G-quadruplexes are further stabilized by the inclusion ... [more ▼]

Guanine-rich DNA strands can form the so-called G-quadruplex architectures due to the formation of quartets of guanines linked by 8 hydrogen bonds. G-quadruplexes are further stabilized by the inclusion of cations between the G-quartets. The abundance of G-rich regions throughout the genome and their very presence in telomeric regions made G-quadruplexes interesting targets. NMR and crystallographic studies of G-quadruplex structures revealed amazing variety in the G-quadruplex topologies. The next challenge will be to understand the rules governing the formation of the various topologies, in order to predict relevant G-quadruplexes in the genome, and in order to act rationally on their formation or disruption. To date, only few experimental [1] or theoretical [2] studies have been devoted to investigating the mechanisms of G-quadruplex formation. We report here a detailed investigation of DNA G-quadruplex formation pathways using electrospray mass spectrometry (ESI-MS). The sequences TGnT (n = 3-6) were purchased from Eurogentec (Seraing, Beliugm). ESI-MS experiments were performed in the negative ion mode on a Q-TOF Ultima Global (Waters, Manchester, UK). The cation used was ammonium (up to 150 mM). Experiments were performed in the presence and absence of methanol (up to 20%) as co-solvent. ESI-MS allows counting both the number of strands and the number of cations in each intermediate. We could confirm the presence of transient dimer and trimer intermediates in low abundance. More unexpectedly, ESI-MS also reveals unambiguously the formation of pentamers which contain ammonium cations. The pentamers slowly convert into tetramers. Counting the number of included cations also revealed that, in the case of (TG6T)4, inclusion of four ammonium cations is fast, while the inclusion of the last ammonium ion is very slow. We also found that the addition of methanol (initially added to obtain higher ion intensities) significantly increases the rate of G-quadruplex formation. Finally, we also investigated the role of G-quadruplex ligands in the rate of formation of G-quadruplexes. We could classify the ligands according to their increase of G-quadruplex formation kinetics, and distinguish the intermediates. Interestingly, one ligand showed formation of a higher-order structure by bridging two G-quadruplexes. Acknowledgement: The authors thank the FRS-FNRS for their support. References: [1] J. Gros et al., Nucleic Acids Res., 2007, doi:10.1093/nar/gkm111. [2] R. Stefl et al., Biophys. J., 2003, 85(3), 1787-1804. [less ▲]

Exploring the Holocene through fossil cyanobacterial sequences from Antarctic lake sediments.

Poster (2009, July 27)

Exploring the L1-L2 Relationship in the L2 Acquisition of Prosody

E-print/Working paper (2009)

Exploring the needs and applicability of a 3D urban land register information system

Report (2009)