Repository of the University of Namur
Not a member yet
94692 research outputs found
Sort by
Efficient Photocatalytic Semihydrogenation of 2-Butyne-1,4-diol over TiO<sub>2</sub> Supported Cu Single Atoms with Near-Unity Conversion and Selectivity
No full textSelective thermocatalytic hydrogenation of 2-butyne-1,4-diol (BYD) to 2-butene-1,4-diol (BED) is vital for producing downstream fine chemicals like pharmaceuticals. However, the current thermocatalytic semihydrogenation typically requires elevated temperatures, excessive high-pressure H2, and costly Pd-based catalysts or flammable Raney Ni. Here, we highlight a sustainable photocatalytic semihydrogenation of BYD to BED using Cu single atoms anchored on TiO2 nanoparticles (Cu-SAs-TiO2) with water as the hydrogen source under ambient conditions. Under the irradiation of simulated solar light, Cu-SAs-TiO2 unprecedentedly achieves a BYD conversion of ∼100% with an exceptionally high BED selectivity of 99.4%, which substantially outperforms the previously reported thermocatalysts. Even in a large-scale photocatalytic system (6 L) and under outdoor sunlight irradiation of 22 h, Cu-SAs-TiO2 still delivered a BYD conversion of ∼100%, a BED selectivity of 97.5%, and a BED production rate of 0.22 mmolBED·gcat-1·h-1. Isotope-labeling analyses, experiments on the kinetic isotope effect of hydrogen, in situ photochemical infrared spectra, and theoretical simulations together reveal that the Cu single atoms promote water dissociation and BED desorption, eventually contributing to a complete BYD conversion and a high BED selectivity.</p
On the location and the strength of controllers to desynchronize coupled Kuramoto oscillators
Get PDFSynchronization is an ubiquitous phenomenon in systems composed of coupled oscillators. While it is often beneficial to the system under consideration, there are nevertheless relevant examples where one would like to reduce it, e.g., in brain dynamics. Indeed although synchronization is essential to the good functioning of brain dynamics, hyper-synchronization can induce problems such as epilepsy seizures. Motivated by this problem, we study a pinning control scheme able to decrease synchronization in a system of coupled Kuramoto oscillators, by focusing on the determination of the best selection strategy for the controllers, i.e., capable to guarantee a lower synchronization level. We show that hubs are generally the most advantageous nodes to control, especially when the degree distribution is heterogeneous. Nevertheless in cases of homogeneous degree distribution having a large distance between pinned nodes, in term of network shortest path length, appears to be also a key factor. We challenge the analytical findings on both synthetic and empirical networks, e.g., brain connectome. Our results are in line with previous works that studied pinning control with the opposite goal, i.e. increasing synchronization. These observations shed light on an interesting universality of good practice of node selection disregarding the actual goal of the control scheme
Can ΔSCF and ROKS DFT-Based Methods Predict the Inversion of the Singlet-Triplet Gap in Organic Molecules?
No full textInverted singlet-triplet gap systems (INVEST) have emerged as an intriguing class of materials with potential applications as emitters in Organic Light Emitting Diodes (OLEDs). Indeed, this type of material exhibits a negative singlet-triplet energy gap (ΔEST), i.e., an inversion of the lowest singlet (S1) and triplet (T1) excited states, that goes against Hund’s rule. In this study, the ΔEST of a set of 15 INVEST molecules has been computed within the framework of Restricted Open-Shell Kohn-Sham (ROKS) and Delta Self-Consistent Field (ΔSCF) methods and the results were benchmarked against wavefunction-based calculations performed at the EOM-CCSD, NEVPT2, and SCS-CC2 levels. We find that ROKS always (and wrongly) predicts a positive ΔEST with global hybrid, meta-GGA, and long-range corrected functionals and that this is almost functional-independent. We also show that the only way to obtain an inverted gap was to resort to double hybrid functionals. In contrast, using the above-mentioned functionals, ΔSCF usually gives a negative ΔEST, although the results are largely functional-dependent. Overall, applying a ΔSCF method based on the PBE0 functional provides the lowest MSD and MAD with respect to the EOM-CCSD results. We further show that the singlet-triplet inversion is driven by different degrees of orbital relaxation in the singlet versus triplet state and that this is well captured by ΔSCF calculations. As a matter of fact, this orbital relaxation in ΔSCF somehow mimics the involvement of double and higher-order excitations in EOM-CCSD, which leads to a difference in spatial localization of the α and β spins, and thus introduces (local) spin polarization effects sourcing the negative ΔEST. However, care should be taken when using the ΔSCF method to screen materials with potential INVEST behavior in view of their limited quantitative correlation with reference EOM-CCSD results on the molecular data basis used here.</p
From Constituency to Continent? Measuring the Shift of Territorial Representational Focus in MEPs' Parliamentary Activity (1994-2024)
Get PDFAs a supranational legislative institution, the European Parliament (EP) is known to put a particular pressure on its members (MEPs) when fulling their mandates. MEPs are famously known for being “the servants of two masters”, i.e. they must serve the interests of their domestic (s)electorate from the territorial districts they were elected in, while being loyal to their European party groups in the EP. This situation is particularly challenging when MEPs face conflicting interests from competing principals. Yet, this situation is not specific to the EP but rather reflects the inevitable “compounded representation” at the heart of federal political systems. In these systems, there is a trade-off balancing “self-rule” with “shared rule” as federal systems present parliamentarians with a classic representational dilemma: standing up for their specific constituency versus addressing the broader interests of the wider polity. This research note analyses how MEPs balance this compounded representation in their parliamentary activity. Because of the continuous extension of EU policy-making powers over the last decades (Maastricht 1993, Amsterdam 1999, Lisbon 2009), along with the institutionalization and empowerment of the EP in the decision-making processes, this analysis is of particular interest for both scholars of European and legislative studies. Have MEPs been shifting their territorial focus as the influence of the EP was increasing? On the opposite, do they remain foremost representatives of national interests? To answer these questions, we introduce a novel conceptualization of territorial representational focus, operationalizing it as a spectrum ranging from localized (constituency-focused) to polity-wide (supranational European) representation. Drawing on a comprehensive dataset spanning three decades (1994–2024) and encompassing the careers of 3,654 Members of the European Parliament (MEPs) who tabled 187,612 parliamentary questions, we present the first systematic measurement of territorial representational focus in parliamentary activity. For that task, we leverage several natural language processing (NLP) techniques, transformer-based models and Retrieval-Augmented Generation (RAG) capabilities. Our findings reveal how territorial focus in MEPs’ questions evolved over time while varying across policy domains, EPGs, countries and MEPs’ seniority. Overall, our approach lays the groundwork for future research by offering a new empirical tool to study territorial representational tensions in MEPs’ parliamentary behaviour.<br/
Astrocyte alterations during Osmotic Demyelination Syndrome:intermediate filaments, aggresomes, proteasomes, and glycogen storages
Get PDFINTRODUCTION: A murine model mimicking the human osmotic demyelination syndrome (ODS) revealed with histology demyelinated alterations in the relay posterolateral (VPL) and ventral posteromedial (VPM) thalamic nuclei 12 h and 48 h after chronic hyponatremia due to a fast reinstatement of osmolality. Abnormal expression astrocyte markers ALDHL1 and GFAP with immunohistochemistry in these ODS altered zones, prompted aims to verify in both protoplasmic and fibrillar astrocytes with ultrastructure those changes and other associated subcellular modifications.METHOD: This ODS investigation included four groups of mice: Sham (NN; n = 13), hyponatremic (HN; n = 11), those sacrificed 12 h after a fast restoration of normal natremia (ODS12h; n = 6), and mice sacrificed 48 h afterward, or ODS48 h (n = 9). Out of those four groups of mice, with LM and ultrastructure microscopy, the thalamic zones included NN (n = 2), HN (n = 2), ODS12h (n = 3) and ODS48h (n = 3) samples. There, comparisons between astrocytes included organelles, GFAP, and glycogen content changes.RESULTS: Thalamic ODS epicenter damages comprised both protoplasmic (PA) and fibrillar (FA) astrocyte necroses along with those of neuropil destructions and neuron Wallerian demyelinated injuries surrounded by a centrifugal region gradient revealing worse to mild destructions. Ultrastructure aspects of resilient HN and ODS12h PAs disclosed altered mitochondria and accumulations of beta- to alpha-glycogen granules that became eventually captured into phagophores as glycophagosomes in ODS48h. HN and ODS12h time lapse FAs accumulated ribonucleoproteins, cytoskeletal aggresomes, and proteasomes but distant and resilient ODS48h FAs maintained GFAP fibrils along with typical mitochondria and dispersed β-glycogen, including in their neuropil surroundings. Thus, ODS triggered astrocyte injuries that involved both post-transcriptional and post-translational modifications such that astrocytes were unable to use glycogen and metabolites due to their own mitochondria defects while accumulated stalled ribonucleoproteins, cytoskeletal aggresomes were associated with proteasomes and GFAP ablation. Resilient but distant astrocytes revealed restitution of amphibolism where typical carbohydrate storages were revealed along with GFAP, as tripartite extensions supply for restored nerve axon initial segments, neural Ranvier's junctions, and oligodendrocyte -neuron junctional contacts.CONCLUSION: ODS caused astrocyte damage associated with adjacent neuropil destruction that included a regional demyelination caused by a loss of dispatched energetic and metabolic exchanges within the injured region, bearing proportional and collateral centrifugal injuries, which involved reactive repairs time after rebalanced osmolarity.</p
David Storey’s Contribution to Enterprise Policy:The Challenge of Stimulating the “Right” Type of Entrepreneurship
Get PDFOne field of research to which David Storey made important contributions is the alleged impact of enterprise policy on regional economic development. In this field, his legacy to entrepreneurship research is perhaps his constant questioning of whether assumptions underpinning enterprise policy are correct. Possibly the most striking example in this regard relates to the assumption that new firms create new jobs. When questions as fundamental as the contribution of new businesses and SMEs to the creation of value and employment are still not clearly resolved; when they lead to questions about what would a priori be identifiable as the “right” type of entrepreneurship and how to promote it, then also comes a questioning about the “right” type of enterprise policy to pursue. David Storey has nourished this field of research with a significant and sometimes radical scope in his questioning. In this chapter, we outline this specific field of research, highlight David’s contributions, and sketch enterprise policy options in the context of global sustainability issues
LolA and LolB are conserved in Bacteroidota and are crucial for gliding motility and Type IX secretion
Get PDFLipoproteins are key outer membrane (OM) components in Gram-negative bacteria, essential for functions like membrane biogenesis and virulence. Bacteroidota, a diverse and widespread phylum, produce numerous OM lipoproteins that play vital roles in nutrient acquisition, Type IX secretion system (T9SS), and gliding motility. In Escherichia coli, lipoprotein transport to the OM is mediated by the Lol system, where LolA shuttles lipoproteins to LolB, which anchors them in the OM. However, LolB homologs were previously thought to be limited to γ- and β-proteobacteria. This study uncovers the presence of LolB in Bacteroidota and demonstrates that multiple LolA and LolB proteins co-exist in various species. Specifically, in Flavobacterium johnsoniae, LolA1 and LolB1 transport gliding motility and T9SS lipoproteins to the OM. Notably, these proteins are not interchangeable with their E. coli counterparts, indicating functional specialization. Some lipoproteins still localize to the OM in the absence of LolA and LolB, suggesting the existence of alternative transport pathways in Bacteroidota. This points to a more complex lipoprotein transport system in Bacteroidota compared to other Gram-negative bacteria. These findings reveal previously unrecognized lipoprotein transport mechanisms in Bacteroidota and suggest that this phylum has evolved unique strategies to manage the essential task of lipoprotein localization.</p
