Vortex rings in axially rotating fluids

Rotating turbulent flows are found in many geophysical, astrophysical and industrial applications. These turbulent flows can be considered to be comprised of a collection of coherent structures. An understanding of these smaller coherent structures can allow insight into the behaviour of the larger turbulent motion as a whole. This thesis focuses on the effect of rotation on one particular type of coherent structure - the vortex ring - and is motivated by the belief that greater knowledge of how individual vortex rings behave in rotating fluids will lead to a better understanding of rotating turbulent flows. The first part of this thesis presents exact solutions of spherical vortices propagating steadily along the axis of a rotating ideal fluid. It is shown that Hill’s spherical vortex and Moffatt’s family of swirling vortices are able to persist in a rotating fluid with the boundary of the spherical vortex swirling in such a way as to exactly cancel out the background rotation of the system. The flow external to the spherical vortex exhibits fully nonlinear inertial wave motion and above a critical rotation rate, closed streamlines may form in this outer fluid region and hence carry fluid along with the spherical vortex. As the rotation rate is further increased, further concentric ‘sibling’ vortex rings are formed. The latter part of this thesis is a numerical investigation into the effect of rotation on vortices in viscous fluids. The presence of azimuthal swirl is critical to vortex ring behaviour and similarities are drawn between the behaviour of swirling vortices in non-rotating flows and initially swirl-free vortex rings in rotating flows which subsequently induce swirl of their own. The findings corroborate past work that suggests vortex motion in rotating fluids can be highly unstable. However, the newly-discovered exact solutions of spherical vortices in rotating ideal fluids are then used to demonstrate that vortex motion in rotating viscous fluids need not be as unstable as previously thought. Finally, as an extremal member of the Fraenkel-Norbury family of vortices this work contrasts the behaviour of Hill’s spherical vortex to vortex rings in this family with narrower vortex cores

Coupled Enzyme Activity and Thermal Shift Screening of the Maybridge Rule of 3 Fragment Library Against Trypanosoma brucei Choline Kinase; A Genetically Validated Drug Target

In this study we interrogate 630 compounds of the Maybridge Rule of 3 Fragment Library for compounds that interact with, and inhibit TbCK. The Maybridge Rule of 3 Fragment Library is a small collection of quantifiable diverse, pharmacophoric rich, chemical entities that comply with the following criteria; MW ≤ 300, cLogP ≤ 3, H-Bond Acceptors ≤ 3, H-Bond Donors ≤ 3, Rotatable bonds (Flexibility Index) ≤ 3, Polar Surface Area ≤ 60 Å2 and aqueous solubility ≥ 1 mM using LogS and high purity (≥ 95%). Comparisons between two different screening methods, a coupled enzyme activity assay and differential scanning fluorimetry, has allowed identification of compounds that interact and inhibit the T. brucei choline kinase, several of which possess selective trypanocidal activity. Screening of a comparatively small fragment library by two different screening methods has allowed identification of several compounds that interact with and inhibit TbCK, a genetically validated drug target against African sleeping sickness. Some of the inhibitory fragments were also selectively trypanocidal, considering these are relatively simple molecules with no optimization, finding low μΜ inhibitors is very encouraging. Moreover some of the morphological phenotypes of these trypanocidal compounds include cell-cycle arrests similar to those observed for the TbCK conditional knockout grown under permissive conditions

Complete eigenstates of identical qubits arranged in regular polygons

We calculate the energy eigenvalues and eigenstates corresponding to coherent single and multiple excitations of an array of N identical qubits or two-level atoms (TLA's) arranged on the vertices of a regular polygon. We assume only that the coupling occurs via an exchange interaction which depends on the separation between the qubits. We include the interactions between all pairs of qubits, and our results are valid for arbitrary distances relative to the radiation wavelength. To illustrate the usefulness of these states, we plot the distance dependence of the decay rates of the n=2 (biexciton) eigenstates of an array of 4 qubits, and tabulate the biexciton eigenvalues and eigenstates, and absorption frequencies, line widths, and relative intensities for polygons consisting of N=2,...,9 qubits in the long-wavelength limit.Comment: Added a figure showing how these results can be used to compute deviations from "equal collective decoherence" approximation

Classroom-based interventions to improve students' learning capital

Published version of the paper reproduced here with permission from the publisherVictoria, Australi

Understanding Young People's Experiences of Cybersecurity

Young people are increasingly becoming responsible for the security of their devices, yet do not appear to have the knowledge to protect themselves online. In this paper, we explore young people’s knowledge of cybersecurity through a series of workshops with school children, and co-develop cybersecurity lessons aimed at engaging this demographic. We find that technical demonstrations are an effective way of engaging young people’s curiosity in the subject, and that group activities aimed at exploring the subject are preferred methods. We also find that while knowledgeable about cybersecurity theory (e.g. passwords), their actual behaviours did not reflect best practice. We discuss the role of schools in cybersecurity education and how to best embed this content in the curriculum to maximize the engagement of students, including a focus on teaching about cybersecurity protective tools

Possible Reasons for Limited Effectiveness of a Skills and Drills Intervention to Improve Emergency Obstetric and Newborn Care.

Youth centers, peer education, and one-off public meetings have generally been ineffective in facilitating young people’s access to sexual and reproductive health (SRH) services, changing their behaviors, or influencing social norms around adolescent SRH. Approaches that have been found to be effective when well implemented, such as comprehensive sexuality education and youth-friendly services, have tended to flounder as they have considerable implementation requirements that are seldom met. For adolescent SRH programs to be effective, we need substantial effort through coordinated and complementary approaches. Unproductive approaches should be abandoned, proven approaches should be implemented with adequate fidelity to those factors that ensure effectiveness, and new approaches should be explored, to include greater attention to prevention science, engagement of the private sector, and expanding access to a wider range of contraceptive methods that respond to adolescents’ needs

The development of recombinant Adenoviral vaccines to target pneumovirus infection

Respiratory Syncytial Virus (RSV) is a member of the pneumovirus genus (family Paramyxoviridae, subfamily Pneumovirinae). RSV is an important respiratory virus of both infants and the elderly, representing an underappreciated burden on health care systems. In addition, re-infections can occur despite the presence of pre-existing immunity, suggesting that immunological memory to RSV is incomplete. To date, treatment of RSV infection is limited to the provision of supportive care and no effective vaccine is available. Although several are currently under investigation, these candidates focus upon the delivery of the F and G antigens of RSV to stimulate the immune system, rather than the internal antigens, which may provide cross protection between different subtypes of RSV. Vaccine development has been greatly hindered by the lack of an appropriate animal model in which to study vaccine efficacy and pneumovirus pathogenesis. Pneumonia virus of mice (PVM) is also a member of the Pneumovirus genus and, like RSV infection of humans, causes a bronchiolitis and fatal pneumonia in its natural host, the mouse. PVM has been proposed as an appropriate model system in which to both study pneumovirus pathogenesis and vaccine efficacy. The PVM model system was adapted to investigate a potential vaccination strategy to address the lack of an available RSV vaccine. Replication deficient recombinant adenovirus serotype 5 (rAd5) vectors were constructed which expressed the F, M and N genes of PVM J3666, in addition to a control construct, which expressed the LacZ gene of E. coli. The constructs were administered via the intranasal route to BALB/c mice and were able to elicit complete protection against a lethal dose of pathogenic PVM J3666, in both short-term experiments and in a long-term experiment, up to 20 weeks post immunisation. The protection effect elicited by the constructs was observed when administered in a single dose, and in alternative mouse strains, C3H/He-mg and C57BL/6, which had differing immunity haplotypes. The rAd5 vectors generated a PVM specific IgG humoral response to PVM and Ad5 antigen which did not correlate as the primary mediator of protection. The rAd5 candidate expressing the N gene of PVM was shown to induce IFNγ secreting T-cells. The use of a peptide library of PVM N protein determined that a specific response could be identified towards the amino acids N41-90, N81-130, N161-210 and N281-330. Thus, the PVM infection model of BALB/c mice provides an immunological platform to facilitate the study of RSV and PVM pathogenesis, immunology and vaccine development.EThOS - Electronic Theses Online ServiceMedical Research Council (Great Britain) (MRC)GBUnited Kingdo

Knife edge skimming for improved separation of molecular species by the deflector

A knife edge for shaping a molecular beam is described to improve the spatial separation of the species in a molecular beam by the electrostatic deflector. The spatial separation of different molecular species from each other as well as from atomic seed gas is improved. The column density of the selected molecular-beam part in the interaction zone, which corresponds to higher signal rates, was enhanced by a factor of 1.5, limited by the virtual source size of the molecular beam.Comment: 3 pages, 2 figure

Management of Imperata cylindrica in smallholder farming systems. Comprehensive notes of visits to Indonesia, January - February 1993

This is a comprehensive record of the visit to the Rubber Research Institute (RRI) Sembawa which has been summarized in previously submitted back to office file notes by the staff concerned. lt places on record an account of the places and individuals visited and describes the work programme for the Indonesian and UK based staff of the Project