Photochemical synthesis of heterocyclic compounds

The aim of our research was to investigate the photocyclisation of N-substituted imide systems, in order to prepare polycyclic heterocyclic photoproducts of potential pharmaceutical interest. The major group of substrates were N-(dialkylaminoalkyl)succinimides. Irradiation of succinimide Mannich bases (A) leads to two diastereoisomers of 1,3-diazabicyclo[3.3,0]octanes in reasonable yields. The relative stereochemistry was assigned on the basis of spectral data. With substrates (e.g. B) derived from unsymmetrical amines, there is strong orientational preference. Substrates (e.g. G) derived from an unsymmetrical succinimide gave a mixture of products; the preferred orientation of cyclisation is to the more hindered C-1 carbonyl group. Using hydantoin substrates (D) which correspond to succinimides in which a methylene group is replaced by a heteroatom, we found that cyclisation occurs only at the C--4 (imide-like) carbonyl group to give diastereoisomers of 1,3,7 - triazabicyclo[3.3,0]octanes. Glutarimide Mannich bases show many parallels with the succinimide analogues. However, pyrrolidin-2-one Mannich bases did not afford photocyclised products. A minor product (E) is formed by cleavage in the amine fragment. N-(Dialkylaminoethyl) derivatives of saturated imides (F) give rise to ring-expanded photoproducts. This is in contrast to phthalimide substrates (G; n = 2), where photoproducts with a new piperazine ring are obtained. Our hypothesis is that an electron-transfer mechanism operates in the aromatic systems, leading to the possibility of medium/large ring formation, but this is not effective in the succinimides which are poorer electron acceptors. To test this, we irradiated a series o f N-(dialkylaminoalkyl) derivatives of imides with a double bond conjugated with the carbonyl groups, and found that these substrates (H) do give photoproducts with new six- or seven-membered rings. Our results with N-(dialkylaminopropyl)phthallmides (G; n = 3) are not entirely in agreement with earlier reports that medium-ring formation is the major photocyclisation process for phthalimide substrates. Further work is required to extend this comparison of the photocyclisation process for saturated, unsaturated and aromatic N-(dialkylaminoalkyl)imides

Assessing the Impact of the Conservation Reserve Program on Honey Bee Health

Insect pollinators are critically important for maintaining U.S. food production and ecosystem health. The upper Midwest is home to more than 40 percent of all U.S. honey bee colonies and is considered by many beekeepers to be America’s last beekeeping refuge. Beekeepers come to this region because their honey bees require high-quality grassland and bee-friendly agricultural crops to make honey and to improve bee health. Agricultural grassland, such as those enrolled in the Conservation Reserve Program (CRP), support flowers that provide bees with the pollen and nectar they need. In 2014, the U.S. Department of Agriculture (USDA) and the U.S. Geological Survey (USGS) formed a partnership to assess the impact of the CRP on honey bee health and determine how the costeffectiveness of the CRP could be improved to promote pollinator habitat. This USGS assessment has generated important findings that could improve USDA’s program delivery and demonstrates the importance of the CRP to honey bees, beekeepers, agricultural producers, and the public (Otto and others, 2017, 2018)

Asymptotically cylindrical 7-manifolds of holonomy G_2 with applications to compact irreducible G_2-manifolds

We construct examples of exponentially asymptotically cylindrical Riemannian 7-manifolds with holonomy group equal to G_2. To our knowledge, these are the first such examples. We also obtain exponentially asymptotically cylindrical coassociative calibrated submanifolds. Finally, we apply our results to show that one of the compact G_2-manifolds constructed by Joyce by desingularisation of a flat orbifold T^7/\Gamma can be deformed to one of the compact G_2-manifolds obtainable as a generalized connected sum of two exponentially asymptotically cylindrical SU(3)-manifolds via the method given by the first author (math.DG/0012189).Comment: 36 pages; v2: corrected trivial typos; v3: some arguments corrected and improved; v4: a number of improvements on presentation, paritularly in sections 4 and 6, including an added picture

The anticipatory and task-driven nature of visual perception

Action Contro

Predicting university performance in psychology: the role of previous performance and discipline-specific knowledge

Recent initiatives to enhance retention and widen participation ensure it is crucial to understand the factors that predict students' performance during their undergraduate degree. The present research used Structural Equation Modeling (SEM) to test three separate models that examined the extent to which British Psychology students' A-level entry qualifications predicted: (1) their performance in years 1-3 of their Psychology degree, and (2) their overall degree performance. Students' overall A-level entry qualifications positively predicted performance during their first year and overall degree performance, but negatively predicted their performance during their third year. Additionally, and more specifically, students' A-level entry qualifications in Psychology positively predicted performance in the first year only. Such findings have implications for admissions tutors, as well as for students who have not studied Psychology before but who are considering applying to do so at university

The latitudes, attitudes, and platitudes of watershed phosphorus management in North America

Phosphorus (P) plays a crucial role in agriculture as a primary fertilizer nutrient—and as a cause of the eutrophication of surface waters. Despite decades of efforts to keep P on agricultural fields and reduce losses to waterways, frequent algal blooms persist, triggering not only ecological disruption but also economic, social, and political consequences. We investigate historical and persistent factors affecting agricultural P mitigation in a transect of major watersheds across North America: Lake Winnipeg, Lake Erie, the Chesapeake Bay, and Lake Okeechobee/Everglades. These water bodies span 26 degrees of latitude, from the cold climate of central Canada to the subtropics of the southeastern United States. These water bodies and their associated watersheds have tracked trajectories of P mitigation that manifest remarkable similarities, and all have faced challenges in the application of science to agricultural management that continue to this day. An evolution of knowledge and experience in watershed P mitigation calls into question uniform solutions as well as efforts to transfer strategies from other arenas. As a result, there is a need to admit to shortcomings of past approaches, plotting a future for watershed P mitigation that accepts the sometimes two-sided nature of Hennig Brandt’s “Devil’s Element.

Electron-Hole Correlations and Optical Excitonic Gaps in Quantum-Dot Quantum Wells: Tight-Binding Approach

Electron-hole correlation in quantum-dot quantum wells (QDQW's) is investigated by incorporating Coulomb and exchange interactions into an empirical tight-binding model. Sufficient electron and hole single-particle states close to the band edge are included in the configuration to achieve convergence of the first spin-singlet and triplet excitonic energies within a few meV. Coulomb shifts of about 100 meV and exchange splittings of about 1 meV are found for CdS/HgS/CdS QDQW's (4.7 nm CdS core diameter, 0.3 nm HgS well width and 0.3 nm to 1.5 nm CdS clad thickness) which have been characterized experimentally by Weller and co-workers [ D. Schooss, A. Mews, A. Eychmuller, H. Weller, Phys. Rev. B, 49, 17072 (1994)]. The optical excitonic gaps calculated for those QDQW's are in good agreement with the experiment.Comment: 3 figures, to appear in Phys.Rev.

Composite Fermion Description of Correlated Electrons in Quantum Dots: Low Zeeman Energy Limit

We study the applicability of composite fermion theory to electrons in two-dimensional parabolically-confined quantum dots in a strong perpendicular magnetic field in the limit of low Zeeman energy. The non-interacting composite fermion spectrum correctly specifies the primary features of this system. Additional features are relatively small, indicating that the residual interaction between the composite fermions is weak. \footnote{Published in Phys. Rev. B {\bf 52}, 2798 (1995).}Comment: 15 pages, 7 postscript figure

Tight-binding study of the influence of the strain on the electronic properties of InAs/GaAs quantum dots

We present an atomistic investigation of the influence of strain on the electronic properties of quantum dots (QD's) within the empirical $s p^{3} s^{*}$ tight-binding (ETB) model with interactions up to 2nd nearest neighbors and spin-orbit coupling. Results for the model system of capped pyramid-shaped InAs QD's in GaAs, with supercells containing $10^{5}$ atoms are presented and compared with previous empirical pseudopotential results. The good agreement shows that ETB is a reliable alternative for an atomistic treatment. The strain is incorporated through the atomistic valence force field model. The ETB treatment allows for the effects of bond length and bond angle deviations from the ideal InAs and GaAs zincblende structure to be selectively removed from the electronic-structure calculation, giving quantitative information on the importance of strain effects on the bound state energies and on the physical origin of the spatial elongation of the wave functions. Effects of dot-dot coupling have also been examined to determine the relative weight of both strain field and wave function overlap.Comment: 22 pages, 7 figures, submitted to Phys. Rev. B (in press) In the latest version, added Figs. 3 and 4, modified Fig. 5, Tables I and II,.and added new reference

Review article: the future of microbiome-based therapeutics

Published online 24 May 2022Background: From consumption of fermented foods and probiotics to emerging applications of faecal microbiota transplantation, the health benefit of manipulating the human microbiota has been exploited for millennia. Despite this history, recent technological advances are unlocking the capacity for targeted microbial manipulation as a novel therapeutic.Aim: This review summarises the current developments in microbiome- based medicines and provides insight into the next steps required for therapeutic development.Methods: Here we review current and emerging approaches and assess the capabilities and weaknesses of these technologies to provide safe and effective clinical inter-ventions. Key literature was identified through Pubmed searches with the following key words, ‘microbiome’, ‘microbiome biomarkers’, ‘probiotics’, ‘prebiotics’, ‘synbiotics’, ‘faecal microbiota transplant’, ‘live biotherapeutics’, ‘microbiome mimetics’ and ‘postbiotics’.Results: Improved understanding of the human microbiome and recent technological advances provide an opportunity to develop a new generation of therapies. These therapies will range from dietary interventions, prebiotic supplementations, single probiotic bacterial strains, human donor-derived faecal microbiota transplants, ra-tionally selected combinations of bacterial strains as live biotherapeutics, and the beneficial products or effects produced by bacterial strains, termed microbiome mimetics.Conclusions: Although methods to identify and refine these therapeutics are continually advancing, the rapid emergence of these new approaches necessitates accepted technological and ethical frameworks for measurement, testing, laboratory practices and clinical translation.Emily L. Gulliver, Remy B. Young, Michelle Chonwerawong, Gemma L. D'Adamo, Tamblyn Thomason, James T. Widdop, Emily L. Rutten, Vanessa Rossetto Marcelino, Robert V. Bryant, Samuel P. Costello, Claire L. O'Brien, Georgina L. Hold, Edward M. Giles, Samuel C. Forste