32151 research outputs found
Sort by
Ethyl (2RS,3SR,4RS)-1-ethyl-2-(furan-2-yl)-4-hydroxy-5-oxopyrrolidine-3- carboxylate
Get PDFFunding: The authors acknowledge Universiti Teknologi MARA for financial support.The title racemic oxopyrrolidine compound, C13H17NO5, contains three stereogenic centres and crystallized with two independent molecules in the asymmetric unit. The five-membered pyrrolidine ring in both molecules exhibit an envelope conformation. In the crystal, independent molecules form dimers through O–H···O hydrogen bonds which then are linked together by weak C–H···O hydrogen bonds.Peer reviewe
Wet chemical method ZnF2 interlayer for high critical current density lithium metal batteries utilizing Ba and Ta-doped Li7LA3Zr2O12 garnet solid electrolyte
Get PDFFunding: V.T. thanks the Natural Sciences and Engineering Research Council of Canada through a Discovery Grant (award number: RGPIN-2021-02493) for the support of this work. S.S. thanks the University of Calgary for the Alberta Innovates Graduate scholarship, and Elizabeth Cannon scholarship in Entrepreneurial Thinking.Li metal batteries with garnet-type solid electrolytes have the potential to increase specific energy and power densities of current Li-ion batteries. Li metal batteries have been hampered by the poor wettability of solid electrolyte with elemental lithium. Here, to resolve the solid garnet electrolyte/Li interface issue, a scalable, cost-effective, and efficient surfactant-assisted wet-chemical strategy is developed. A ZnF2 interlayer coating is applied on Ba and Ta -co-doped Li7La2.75Ba0.25Zr1.75Ta0.25O12 that formed LiF and Li-Zn alloy upon contact with molten Li. Conformal contact applying a homogenous surfactant-assisted ZnF2 coating reduced the interfacial resistance from 87 to 15.5 Ω cm2 which enhanced critical current density to a record high value of 5 mA cm−2 at room temperature. Dense and Li2CO3 free garnet solid electrolyte assisted in achieving long-term stability for 1000 cycles at 1 mA cm−2. Interface stabilized Li/ZnF2- solid electrolyte/liquid electrolyte/LiFePO4 cell displayed a 90% capacity retention over 800 cycles at 0.2 C, with Coulombic efficiency of 99% as well as excellent cycle stability at 1 C, with ≈91% of capacity retention for 500 cycles. Using a new design principle for Li anode interfaces, next-generation power-intensive and stable solid-state Li metal batteries can be developed.Peer reviewe
Green governance : how ESG performance drives financial performance in UK firms
Get PDFIn this research endeavor, we investigate the potential influence exerted by ESG performance on the market capitalization of non-financial corporations included within the UK FTSE All-Share Index during the eleven-year period spanning 2010 to 2021. Integrating insights from Resource-Based View and Stakeholder Theory, this research extends the literature by considering the moderating effect of governance on the ESG–market capitalization association. This study analyzes a comprehensive dataset of UK firms, employing robust econometric techniques to substantiate its conclusions. The results demonstrate a robust positive association between the overall ESG pillars and market capitalization. Environmental, social, and governance performances independently contribute to an increased market value. The analysis reveals that firms with superior internal governance structures, characterized by the presence of independent board members, board size, an independent audit committee, and the implementation of a split CEO–chair structure, experience a magnified positive impact from ESG disclosures on market capitalization. Effective governance mechanisms enhance the credibility and effectiveness of ESG initiatives, aligning them with stakeholder expectations and regulatory standards. This alignment fosters trust and cooperation, driving better financial performance and increasing market value. This research adds its voice to the increasingly compelling body of evidence that underscores the financial advantages associated with ESG integration and highlights the critical role of internal governance in amplifying these benefits. The findings have significant implications for policymakers, investors, and corporate managers. They advocate for the strategic incorporation of ESG criteria into corporate governance frameworks to achieve sustainable financial success.Peer reviewe
Helically chiral multiresonant thermally activated delayed fluorescent emitters and their use in hyperfluorescent organic light-emitting diodes
Get PDFFunding: J. W. thanks the China Scholarship Council (202006250026). D. Chen thanks the support from China Postdoctoral Science Foundation (Grant No. 2022TQ0227) and Natural Science Foundation of Jiangsu Province, China (Grant No. BK20230508). We acknowledge support from the European Commission Research Executive Agency (Grant Agreement Number: 859752 HEL4CHIR-OLED H2020-MSCA-ITN-2019). This work was also funded by the EPSRC through grant numbers EP/R00188X/1, EP/W007517/1, and EP/W015137/1. X. Zhang thanks the support from National Natural Science Foundation of China (Grant No. 52130304, 51821002), and Collaborative Innovation Center of Suzhou Nano Science & Technology, Joint International Research Laboratory of Carbon-Based Functional Materials and Devices.Chiral multiresonant thermally activated delayed fluorescence (MR-TADF) materials show great potential as emitters in circularly polarized (CP) organic light-emitting diodes (CP-OLEDs) owing to their bright and narrowband CP emission. Here, two new chiral MR-TADF emitters tBuPh-BN and DPA-tBuPh-BN possessing intrinsically helical chirality have been synthesized and studied. The large steric interactions between the tert-butylphenyl groups not only induce the helical chirality but also provide a notable configurational stability to the enantiomers. Racemic mixtures of tBuPh-BN and DPA-tBuPh-BN show narrowband emission at 490 and 477 nm with full-width at half maximum (FWHM) of 25 and 28 nm and photoluminescence quantum yields, FPL, of 85 and 54% in toluene. The separated enantiomers of tBuPh-BN and DPA-tBuPh-BN show symmetric circularly polarized luminescence (CPL) with respective dissymmetry factors |gPL| values of 1.5 × 10-3 and 0.9 × 10-3 38 . The hyperfluorescence organic light-emitting diodes (HF-OLEDs) with tBuPh-BN and DPA-tBuPh-BN acting as terminal emitters and 2,3,4,5,6-penta-(9H-carbazol-9- yl)benzonitrile (5CzBN) as their assistant dopant exhibited, respectively, maximum external quantum efficiencies (EQEmax) of 20.9 and 15.9% at 492 and 480 nm with FWHM of 34 and 38 nm. This work demonstrates a strategy for developing intrinsically helically chiral MR-TADF emitters possessing significant configurationally stability, which can be used in HF-OLEDs.Peer reviewe
A detailed investigation of particle energisation mechanisms in models of collapsing magnetic traps
Get PDFFunding: KM acknowledges financial support by the Science and Technology Facilities Council (STFC) through a PhD studentship (DTP ST/V507076/1) and TN acknowledges funding by STFC Consolidated Grants ST/S000402/1 and ST/W001195/1.In this paper, we provide a detailed investigation of the energization processes in two-dimensional, two and a half-dimensional, and three-dimensional collapsing magnetic trap models. Using kinematic magnetohydrodynamic models of collapsing magnetic traps, we examine the importance of Fermi acceleration in comparison with betatron acceleration in these models. We extend previous work by investigating particle orbits in two-dimensional models without and with a guide field component and from full three-dimensional models. We compare the outcomes for the different models and how they depend on the chosen initial conditions. While in the literature betatron acceleration has been emphasized as the major mechanism for particle energization in collapsing magnetic traps, we find that Fermi acceleration can play a significant role as well for particle orbits with suitable initial conditions.Peer reviewe
Ethyl 4H-Pyran-4-one-2-carboxylate
Get PDFFunding: This research received no external funding.The title compound has been characterised for the first time by 13C NMR, including determination of CH coupling constants, and its X-ray structure has been determined showing double ribbons of molecules in the crystal held together by weak CH to O=C hydrogen bonds.Peer reviewe
High resolution ALMA observations of richly structured protoplanetary disks in σ Orionis
Get PDFFunding: T.B. acknowledges funding from the European Union under the European Unions Horizon Europe Research and Innovation Programme 101124282 (EARLYBIRD) and funding by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under grant 325594231, and Germany’s Excellence Strategy - EXC-2094 - 390783311. Support for F.L. was provided by NASA through the NASA Hubble Fellowship grant #HST-HF2-51512.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555S.Z. acknowledges support through the NASA FINESST grant 80NSSC20K1376. Support for S.Z. was provided by NASA through the NASA Hubble Fellowship grant #HST-HF2-51568 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555.The Atacama Large Millimeter/submillimeter Array (ALMA) has detected substructures in numerous protoplanetary disks at radii from a few to over 100 au. These substructures are commonly thought to be associated with planet formation, either by serving as sites fostering planetesimal formation or by arising as a consequence of planet–disk interactions. Our current understanding of substructures, though, is primarily based on observations of nearby star-forming regions with mild UV environments, whereas stars are typically born in much harsher UV environments, which may inhibit planet formation in the outer disk through external photoevaporation. We present high-resolution (∼8 au) ALMA 1.3 mm continuum images of eight disks in σ Orionis, a cluster irradiated by an O9.5 star. Gaps and rings are resolved in the images of five disks. The most striking of these is SO 1274, which features five gaps that appear to be arranged nearly in a resonant chain. In addition, we infer the presence of gap or shoulder-like structures in the other three disks through visibility modeling. These observations indicate that substructures robustly form and survive at semimajor axes of several tens of au or less in disks exposed to intermediate levels of external UV radiation as well as in compact disks. However, our observations also suggest that disks in σ Orionis are mostly small, and thus millimeter continuum gaps beyond a disk radius of 50 au are rare in this region, possibly due to either external photoevaporation or age effects.Peer reviewe
Optimized methods for the targeted surveillance of extended-spectrum beta-lactamase-producing Escherichia coli in human stool
Get PDFFunding: This work was supported by iiCON (Infection Innovation Consortium) via UK Research and Innovation (107136) and Unilever (MA-2021-00523N).Understanding transmission pathways of important opportunistic, drug-resistant pathogens, such as extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli , is essential to implementing targeted prevention strategies to interrupt transmission and reduce the number of infections. To link transmission of ESBL-producing E. coli (ESBL-EC) between two sources, single-nucleotide resolution of E. coli strains, as well as E. coli diversity within and between samples, is required. However, the microbiological methods to best track these pathogens are unclear. Here, we compared different steps in the microbiological workflow to determine the impact different pre-enrichment broths, pre-enrichment incubation times, selection in pre-enrichment, selective plating, and DNA extraction methods had on recovering ESBL-EC from human stool samples, with the aim to acquire high-quality DNA for sequencing and genomic epidemiology. We demonstrate that using a 4-h pre-enrichment in Buffered Peptone Water, plating on cefotaxime-supplemented MacConkey agar and extracting DNA using Lucigen MasterPure DNA Purification kit improves the recovery of ESBL-EC from human stool and produced high-quality DNA for whole-genome sequencing. We conclude that our optimized workflow can be applied for single-nucleotide variant analysis of an ESBL-EC from stool. IMPORTANCE Drug-resistant infections are increasingly difficult to treat with antibiotics. Preventing infections is thus highly beneficial. To do this, we need to understand how drug-resistant bacteria spread to take action to stop infection and transmission. This requires us to accurately trace these bacteria between different sources. In this study, we compared different laboratory methods to see which worked best for detecting extended-spectrum beta-lactamase (ESBL)-producing E. coli , a common cause of urinary tract or bloodstream infections, from human stool samples. We found that enriching stool in a nutrient broth for 4 h, then plating the bacterial suspension on antibiotic-selective MacConkey agar, and finally extracting DNA from the bacteria using a specific DNA purification kit resulted in improved recovery of ESBL E. coli and high-quality DNA. Sequencing multiple isolates from stool allowed us to distinguish unambiguously and at high resolution between different variants of ESBL E. coli present in stool.Peer reviewe
Tree-like process tensor contraction for automated compression of environments
Get PDFFunding: M.C. and E.M.G. acknowledge funding from EPSRC grant no. EP/T01377X/1. B.W.L. and J.K. acknowledge funding from EPSRC grant no. EP/T014032/1.The algorithm “automated compression of environments” (ACE) [M. Cygorek et al., Nat. Phys. 18, 662 (2022)] provides a versatile way of simulating an extremely broad class of open quantum systems. This is achieved by encapsulating the influence of the environment, which is determined by the interaction Hamiltonian(s) and initial states, into compact process tensor matrix product operator (PT-MPO) representations. The generality of the ACE method comes at high numerical cost. Here, we demonstrate that orders-of-magnitude improvement of ACE is possible by changing the order of PT-MPO contraction from a sequential to a treelike scheme. The problem of combining two partial PT-MPOs with large inner bonds is solved by a preselection approach. The drawbacks of the preselection approach are that the MPO compression is suboptimal and that it is more prone to error accumulation than sequential combination and compression. We therefore also identify strategies to mitigate these disadvantages by fine-tuning compression parameters. This results in a scheme that is similar in compression efficiency and accuracy to the original ACE algorithm, yet is significantly faster. Our numerical experiments reach similar conclusions for bosonic and fermionic test cases, suggesting that our findings are characteristic of the combination of PT-MPOs more generally.Peer reviewe
Vulnerability, climate laws, and adaptation in the Middle East and North Africa
Get PDFLaws aimed at tackling climate change problems have grown significantly in the last two decades. Following this global trend and under pressure from international institutions and lenders, both rich, oil exporting (i.e., major greenhouse gas [GHG] emitters) and poor, non-oil rich (i.e., mostly vulnerable nations with lower shares of emission) states in the Middle East and North Africa have hastened to adopt new laws and regulations to mitigate and/or adapt to climate change. The question remains, however, does the adoption of these laws have any measurable impact on these nations' climate change performance? That is, to what degree do these laws have an impact on greenhouse gas emissions or adaptation capacity and readiness? Utilizing a panel data of 660 country-year observations (22 countries over 30 years), our cross-national statistical analysis shows that while climate change laws seem to have an impact on GHG emissions, they have so far failed to boost these nations' adaptation capacity. Our case study shows that oil politics and basic development objectives seem to be the key to this failure.Peer reviewe
Access Repository Dashboard
Do you manage St Andrews Research Repository? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!