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Evolution of the relation between the mass accretion rate and the stellar and disk mass from brown dwarfs to stars
No full textFunding: V.A.-A. acknowledges funding by the Science and Technology Foundation of Portugal (FCT), grants No. IF/00194/2015, PTDC/FIS-AST/28731/2017, UIDB/00099/2020 and SFRH/BD/143433/2019. V.A.-A. acknowledges ESO for their support during the initial six months of this work. Funded by the European Union (ERC, WANDA, 101039452). This work was partly supported by the Italian Ministero dell’Istruzione, Università e Ricerca through the grant Progetti Premiali 2012-iALMA (CUP C52I13000140001), by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Ref. no. 325594231 FOR 2634/2 TE 1024/2-1, by the DFG Cluster of Excellence Origins (https://www.origins-cluster.de). This project has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska Curie grant agreement No. 823823 (DUSTBUSTERS), and from the European Research Council (ERC) via the ERC Synergy Grant ECOGAL (grant 855130). K.M. acknowledges support from the Fundação para a Ciência e a Tecnologia (FCT) through the CEEC-individual contract 2022.03809.CEECIND and research grants UIDB/04434/2020 and UIDP/04434/2020. J.M.A. acknowledges financial support from the project PRIN-INAF 2019 “Spectroscopically Tracing the Disk Dispersal Evolution (STRADE) and the Large Grant INAF 2022 YSOs Outflows, Disks and Accretion” (YODA).The time evolution of the dependence of the mass accretion rate with the stellar mass and the disk mass represents a fundamental way to understand the evolution of protoplanetary disks and the formation of planets. In this work, we present observations with X-shooter of 26 Class II very low-mass stars (< 0.2 M⊙) and brown dwarfs in the Ophiuchus, Chamaeleon-I, and Upper Scorpius star-forming regions. These new observations extend the measurement of the mass accretion rate down to spectral type (SpT) M9 (∼0.02 M⊙) in Ophiuchus and Chamaeleon-I and add 11 very-low-mass stars to the sample of objects previously studied with broadband spectroscopy in Upper Scorpius. We obtained the spectral type and extinction, as well as the physical parameters of the sources. We used the intensity of various emission lines in the spectra of these sources to derive the accretion luminosity and mass accretion rates for the entire sample. Combining these new observations with data from the literature, we compare relations between accretion and stellar and disk properties of four different star-forming regions with different ages: Ophiuchus (∼1 Myr), Lupus (∼2 Myr), Chamaeleon-I (∼3 Myr), and Upper Scorpius (5−12 Myr). We find the slopes of the accretion relationships (L∗ − Lacc, M∗ − Ṁacc) to steepen in the 1−3 Myr age range (i.e., between Ophiuchus, Lupus, and Chamaeleon-I) and that both relationships may be better described with a single power law. We find that previous claims for a double power-law behavior of the M∗ − Ṁacc relationship may have been triggered by the use of a different SpT–Teff scale. We also find the relationship between the protoplanetary disk mass and the mass accretion rate of the stellar population to steepen with time down to the age of Upper Scorpius. Overall, we observe hints of a faster evolution into low accretion rates of low-mass stars and brown dwarfs. At the same time, we also find that brown dwarfs present higher Mdisk/Ṁacc ratios (i.e., longer accretion depletion timescales) than stars in Ophiuchus, Lupus, and Cha-I. This apparently contradictory result may imply that the evolution of protoplanetary disks around brown dwarfs may be different than what is seen in the stellar regime.Peer reviewe
Highly efficient hydrogenative depolymerisation of polycaprolactone to 1,6-hexanediol
No full textFunding: This research was funded by a UKRI Future Leaders Fellowship (MR/W007460/1) and an EPSRC grant (EP/Y005449/1).We report here our study on the development of an efficient process to make 1,6-hexanediol from the hydrogenation of polycaprolactone assisted by ethanolysis. Using a ruthenium SNS pincer catalyst, a record high turnover number of 19 600 with 98% yield of 1,6-hexanediol is obtained at 80 °C and 60 bar H2 pressure. The reported method has environmental advantages over the conventional process for the production of 1,6-hexanediol, which emits a significant amount of nitrous oxide greenhouse gas.Peer reviewe
Protocol for a scoping review on learning analytics in language education
No full textLearning Analytics (LA) holds growing promise to inform language education, yet information on its application, pedagogical impact, and implementation challenges remains fragmented. This scoping review aims to systematically map existing primary research on the use of LA in language education. Following the SMART framework, this review will collect data by searching five major databases, EBSCO, ACM Digital Library, Scopus, Web of Science, and CNKI, with a predefined search strategy. It will include primary research focusing on LA in any language learning context across all educational levels and settings. Extracted data will be synthesised descriptively and thematically to report the purposes for which LA has been applied in language education, its pedagogical outcomes, the challenges impacting its implementation and the methodological approaches used in LA research. The findings are likely to inform future practice, research, and tool development on LA in language education contexts.Peer reviewe
Electronic structure of monolayer CrTe2 : an antiferromagnetic two-dimensional van der Waals material
No full textFunding: The authors gratefully acknowledge support from EPSRC through Grants No. EP/T031441/1 (O.A., P.W., P.D.C.K.), No. EP/X015556/1 (B.K.S., P.W., and P.D.C.K.), and No. EP/M023958/1 and from the Leverhulme Trust through Grant No. RPG-2022-315 (P.W. and L.C.R.).Magnetic van der Waals materials are an important building block to realize spintronic functionalities in heterostructures of two-dimensional (2D) materials. However, establishing their magnetic and electronic properties and the interrelationship between the magnetic ground state and electronic structure is often challenging because only a limited number of techniques can probe magnetism and electronic structure on length scales of tens to hundreds of nanometers. Chromium chalcogenides are a class of 2D magnetic materials for which a rich interplay between structure and magnetism has been predicted. Here, we combine angle-resolved photoemission and quasiparticle interference imaging to establish the electronic structure of a monolayer of CrTe2 on graphite. From a comparison of model calculations with spectroscopic mapping using angle-resolved photoemission spectroscopy and scanning tunneling microscopy we establish the magnetic ground state and the low-energy electronic structure. We demonstrate that the band structure of monolayer CrTe2 is captured well by density functional theory (DFT) in a DFT+ U framework when a Coulomb repulsion of U = 2.5eV is accounted for.Peer reviewe
A sociocultural analysis of teacher language assessment literacy (LAL) development : stories from a novice Vietnamese EFL teacher
No full textFunding: Duolingo English Test, University of Queensland.Guided by sociocultural theory, this single-case narrative inquiry views language assessment literacy development as a process of language assessment concept formation and examines how a teacher’s language assessment concepts were formed, what sociocultural elements mediated those concept formations, and how the focal teacher emotionally experienced those concept formations. To fulfill these aims, approximately 15 hours of audio and video data were collected from a novice Vietnamese teacher of English as a foreign language via interviews, classroom observations, and verbal reports. The data were transformed into narrative vignettes which were then subject to directed content analysis guided by sociocultural theory’s notions of concept and perezhivanie. The study found that teacher assessment concept formation was a long, complex, and ongoing process involving various sociocultural mediators. Notably, the mediation of sociocultural factors was not direct but refracted through the participant’s evolving perezhivanie. Furthermore, empirical concepts derived from the focal teacher’s practical assessment experiences played a more significant role than scientific concepts originating from formal instruction and academic literature. Finally, the study has demonstrated the role of emotions in mediating assessment concept formations. Drawing on these findings, the study argues that language teacher education programs need to integrate best language assessment practices, leverage student teachers’ empirical experiences, and utilize teacher educators’ responsive mediation to support teacher language assessment literacy development.Peer reviewe
The structural and functional characterisation of human metabolic enzymes
No full textAbstract redacte
Mechanistic insights into human 4-oxo-L-proline reductase (BDH2) from pre-steady-state kinetics and isotope effects
Get PDFThe human enzyme BDH2 catalyses the reversible NADH-dependent reduction of 4-oxo-L-proline (4oLP) to cis-4-hydroxy-L-proline (c4hLP). c4hLP was not known to occur in mammals until this discovery; furthermore, this compound has anticancer properties. BDH2 itself is also involved in multiple cancers, playing a role in regulating apoptosis and the cell cycle. Oncological research on BDH2 precedes its functional characterisation, however, and so the mechanism by which BDH2 acts in cancers remains elusive, but could be explored by using an inhibitor as a chemical probe in cancer cells. Rational development of such an inhibitor can be informed with knowledge of the catalytic mechanism of BDH2, to which end we have explored the action of this enzyme via steady- and pre-steady-state kinetics, isotope effect studies, and biophysical assays. We have discovered that BDH2 has a tight binding affinity for NADH, and that c4hLP formation is highly thermodynamically favoured. Interaction between the enzyme and NAD(H) confers significant thermostability to BDH2, which has a very low melting temperature without addition of NAD(H). It is therefore posited that BDH2 effectively exists as NAD(H)-bound in the cell, resulting in a pseudo-ordered reaction mechanism in which substrate binding may not be strictly ordered, but is ordered in practice due to high affinity. Stereospecific deuteration of NADH establishes that the pro-S hydrogen is transferred in the reaction. Kinetic isotope effect studies demonstrate that the chemical step of the reaction is very fast and largely unperturbed by unfavourable reaction conditions such as pH, temperature or use of NADPH for which affinity is low. An ionisable group with a pKₐ of 7.3 must be deprotonated for optimal 4oLP binding and/or catalysis. Steady- and pre-steady-state kinetics show that at least one step post-chemistry is partially rate-limiting; we hypothesise that this is likely departure of NAD⁺ from the active site after catalysis
Jesus with his disciples : the evocation of OG Isaiah in Matthew's presence theme
No full textIsaiah 7–8 features heavily within treatments of Matthew 1:22–23, with many scholars considering how this Isaianic quotation relates to the rest of Matthew’s presence theme. Whilst the ubiquity of Isaiah within Matthew’s Gospel is well observed, this prophetic text barely appears within discussions of other passages beyond 1:22–23 that are constitutive of Matthew’s presence theme. MT Isaiah contains, however, several other passages beyond chapters 7–8 in which God is with his people (41:10; 43:2, 5). Not only that, but these statements are connected to one another (in MT and OG): this is particularly the case with OG Isaiah, which also contains an additional “God-with” statement not found in MT (58:11). I suggest that Matthew evokes several of these OG Isaianic passages in connection with his presence theme. As such, OG Isaiah is determinative for Matthew’s depiction of Jesus as “God with us.”
Employing Stefan Alkier’s semiotic-critical approach to biblical interpretation, I show how Matthew’s contextually-aware “Immanuel” quotation in 1:22–23 (Isa 7:14; 8:8, 10) creates that which Susanne Holthuis terms an “intertextual disposition,” from which one is disposed to search for further Isaianic intertexts within Matthew’s presence theme. Accordingly, Matthew’s accounts of both Jesus walking on the water (14:22–33) and final judgement (25:31–46) evoke OG Isaianic passages (chs. 43 and 58 respectively) in which God promises to be with his people. Such evocation not only signals Isaiah’s relevance for interpreting Matthew’s presence theme beyond the oft-discussed Immanuel quotation, but also bears upon interpretive issues concerning Jesus’ identity vis-à-vis Israel’s God and the disciples vis-à-vis God’s people."This work was supported by the St Mary’s Anniversary Scholarship"--Fundin
Childbearing behaviour among women with migrant family backgrounds in the United Kingdom
No full textThis thesis examines the childbearing behaviour of women with migrant family backgrounds in the United Kingdom. It aims to demonstrate how and why their fertility patterns differ from those of women from non-migrant family backgrounds, and how these trends have changed over time. The United Kingdom has experienced simultaneous population shifts in recent times, with declining fertility rates and increased immigration flows. Yet, there remains a lack of understanding of the fertility behaviours of child migrants and the descendants of immigrants, as well as the reasons underlying the fertility differences among them. This thesis fills this gap by examining fertility by parity among women with migrant family backgrounds, particularly those who spent at least part of their formative years in the United Kingdom before transitioning to adulthood – including child migrants and those born in the United Kingdom to at least one foreign-born parent.
An event-history approach is applied, incorporating both single- and multi-process models, using longitudinal survey data and register-based data. The results show evident fertility variations among women of different origins and a partial convergence of fertility at first birth across some migrant generations toward that of British natives. The thesis further finds that socio-cultural backgrounds shape childbearing behaviour differently based on parity, migrant-origin background, and generation. These findings advance our understanding of fertility behaviours within minority populations by underlying variations across migrant generations and origins, thereby reducing the tendency to base knowledge of fertility behaviour solely on the majority population. These insights contribute to a deeper appreciation of the intersectional nature of childbearing and provide evidence to support the development of more inclusive family policies."This work was supported by the Scottish Graduate School of Social Science. Pathway: Health, Families, Relationships and Demographic Change / Steer: AQM This research is also part of the MigrantLife Project that has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 834103)."--Fundin
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