Heat transfer studies of strontium recombination lasers

Thermal loading models have been developed in order to predict the optimum input powers of free-convection cooled strontium recombination lasers (SRLs) and forced-convection cooled SRLs. Gas temperature models have also been developed for circular bore and rectangular bore SRLs, to complement the thermal loading models, so that the performances of circular and rectangular bore SRLs can be compared. It has been shown, in theory, that rectangular bore tubes offer operation at lower gas temperatures than do circular bore tubes of the same cross-sectional area, with the same input power per unit length. Laser performance is, therefore, expected to be improved through the use of rectangular bores in the construction of SRLs. The results of the thermal loading models are validated by experiments. The need to oven process alumina tubes in forming gas, prior to their use in the SRL, is demonstrated by an increase in output power from tubes processed using this technique. Enhanced radiative heat extraction, accompanied by an increase in average laser output power, is obtained from a free-convection cooled SRL by increasing the emissivity of the outer surface of the ceramic discharge tube. Three rectangular bore water-cooled SRLs, optimising at different input powers, have been constructed, operated and compared in performance to a free-convection cooled SRL, constructed using the same ceramic discharge tube. An average output power of 2.3 W has been obtained from a 40 cm long rectangular bore beryllia discharge tube through the use of active water cooling. This represents an improvement of over 200% when compared to the performance of a free-convection cooled SRL utilizing the same ceramic discharge tube

The role of aerodynamic forces in a mathematical model for suspension bridges

In a fish-bone model for suspension bridges studied by us in a previous paper we introduce linear aerodynamic forces. We numerically analyze the role of these forces and we theoretically show that they do not influence the onset of torsional oscillations. This suggests a new explanation for the origin of instability in suspension bridges: it is a combined interaction between structural nonlinearity and aerodynamics and it follows a precise pattern. This gives an answer to a long-standing question about the origin of torsional instability in suspension bridges

Learning outcomes, learning support, and cohort cohesion on a virtual field trip: an analysis of student and staff perceptions

The rise seen in the use of the virtual field trip in 2020 and 2021 due to the global COVID-19 pandemic was unprecedented. Virtual field trips aim to replicate the learning outcomes and experiences of actual field trips by providing a digital alternative to in-field courses. They provide valuable opportunities for those unable to visit the field and alternative learning experiences for those that can. However, understanding their efficacy in terms of learning outcomes, the effectiveness of the learning support offered, and cohort cohesion generally remains untested. Here, we show how negative aspects of a virtual field trip both pre- and post-course are countered by positive outcomes in terms of the breadth of learning outcomes and experience. As part of our analysis, we tested methods to mitigate barriers to inclusion and learning on a virtual field trip, including internet connectivity and hardware access; the use of printed workbooks; and limitations to interaction, support, and cohort cohesion. Our results show that, although negative perceptions (as evidenced by questionnaire responses) are dominant, with 71 % of the 27 pre-course respondents and 88 % of the 21 post-course respondents commenting on these aspects across both student and staff cohorts, positive aspects of virtual field trips (43 %–57 %) also feature highly. Students show a positive shift in their perception of online teaching and learning over the course, with positive comments moving from 19 % pre-course to 71 % post-course, whereas positive comments by staff are low both pre- and post-course (at 14 %). Printed workbooks, staff-to-student ratios, and interaction are received positively. Overall, we find that negative perceptions of virtual field trips pre- and post-course exist but that both students and staff also identify positive elements, including the breadth of learning outcomes, particularly regarding data synthesis and analysis. We suggest ways to learn from these findings in order to design virtual field trips that deliver effectively in blended learning environments for the benefit of all.</p

Uso da espectroscopia no infravermelho próximo (NIR) para predição rápida de concentração de etanol em fermentados.

bitstream/item/110379/1/CT.-335.pd

Palaeogeographical evolution of the Rattray Volcanic Province, Central North Sea

Funded by Carnegie Trust for the Universities of Scotland PHD060365Peer reviewedPostprin

Protection of Double-Stranded RNA via Complexation with Double Hydrophilic Block Copolymers: Influence of Neutral Block Length in Biologically Relevant Environments

Interaction between the anionic phosphodiester backbone of DNA/RNA and polycations can be exploited as a means of delivering genetic material for therapeutic and agrochemical applications. In this work, quaternized poly(2-(dimethylamino)ethyl methacrylate)-block-poly(N,N-dimethylacrylamide) (PQDMAEMA-b-PDMAm) double hydrophilic block copolymers (DHBCs) were synthesized via reversible addition–fragmentation chain-transfer (RAFT) polymerization as nonviral delivery vehicles for double-stranded RNA. The assembly of DHBCs and dsRNA forms distinct polyplexes that were thoroughly characterized to establish a relationship between the length of the uncharged poly(N,N-dimethylacrylamide) (PDMA) block and the polyplex size, complexation efficiency, and colloidal stability. Dynamic light scattering reveals the formation of smaller polyplexes with increasing PDMA lengths, while gel electrophoresis confirms that these polyplexes require higher N/P ratio for full complexation. DHBC polyplexes exhibit enhanced stability in low ionic strength environments in comparison to homopolymer-based polyplexes. In vitro enzymatic degradation assays demonstrate that both homopolymer and DHBC polymers efficiently protect dsRNA from degradation by RNase A enzyme

The Borrelia afzelii outer membrane protein BAPKO_0422 binds human Factor-H and is predicted to form a membrane-spanning beta-barrel

The deep evolutionary history of the Spirochetes places their branch point early in the evolution of the diderms, before the divergence of the present day Proteobacteria. As a Spirochete, the morphology of the Borrelia cell envelope shares characteristics of both Gram-positive and Gram-negative bacteria. A thin layer of peptidoglycan, tightly associated with the cytoplasmic membrane is surrounded by a more labile outer membrane (OM). This OM is rich in lipoproteins but with few known integral membrane proteins. The OmpA domain is an eight-stranded membrane-spanning β-barrel, highly conserved among the Proteobacteria but so far unknown in the Spirochetes. In the present work we describe the identification of four novel OmpA-like β-barrels from Borrelia afzelii, the most common cause of erythema migrans rash in Europe. Structural characterisation of one these proteins (BAPKO_0422) by small angle X-ray scattering (SAXS) and circular dichroism indicate a compact globular structure rich in β-strand consistent with a monomeric β-barrel. Ab initio molecular envelopes calculated from the scattering profile are consistent with homology models and demonstrate that BAPKO_0422 adopts a peanut shape with dimensions 25 x 45 Å. Deviations from the standard C-terminal signature sequence are apparent; in particular the C-terminal Phe residue commonly found in Proteobacterial OM proteins is replaced by Ile/Leu or Asn. BAPKO_0422 is demonstrated to bind human factor-H and therefore may contribute to immune evasion by inhibition of the complement response. Encoded by chromosomal genes, these proteins are highly conserved between Borrelia subspecies and may be of diagnostic or therapeutic value