19,768 Works

Data from: Modeling effects of environmental change on wolf population dynamics, trait evolution, and life history

Tim Coulson, Daniel R. MacNulty, Daniel R. Stahler, Bridgett VonHoldt, Robert K. Wayne & Douglas W. Smith
Environmental change has been observed to generate simultaneous responses in population dynamics, life history, gene frequencies, and morphology in a number of species. But how common are such eco-evolutionary responses to environmental change likely to be? Are they inevitable, or do they require a specific type of change? Can we accurately predict eco-evolutionary responses? We address these questions using theory and data from the study of Yellowstone wolves. We show that environmental change is expected...

Data from: Mitochondrial capture by a transmissible cancer

Clare A. Rebbeck, Armand M. Leroi & Austin Burt
Canine transmissible venereal tumor (CTVT) is an infectious cell line circulating in many feral dog populations. It originated once, about 10,000 years ago. Phylogenetic analyses of mitochondrial sequences from dogs, wolves, and a geographically diverse collection of CTVT samples indicate that the cancer has periodically acquired mitochondria from its host. We suggest that this may be because the cancer’s own mitochondria have a tendency to degenerate, due to high mutation rates and relaxed selection, resulting...

Data from: Blocking the evolution of insecticide-resistant malaria vectors with a microsporidian

Jacob C. Koella, Adam Saddler & Thomas P. S. Karacs
Finding a way to block the evolution insecticide-resistance would be a major breakthrough for the control of malaria. We suggest that this may be possible by introducing a stress into mosquito populations that restores the sensitivity of genetically resistant mosquitoes and that decreases their longevity when they are not exposed to insecticide. We use a mathematical model to show that, despite the intense selection pressure imposed by insecticides, moderate levels of stress might tip the...

Data from: Molecular detection of trophic links in a complex insect host-parasitoid food web

Jan Hrcek, Scott E Miller, Donald L J Quicke & M. Alex Smith
Previously, host-parasitoid links have been unveiled almost exclusively by time-intensive rearing, while molecular methods were used only in simple agricultural host-parasitoid systems in the form of species specific primers. Here we present a general method for molecular detection of these links applied to a complex caterpillar-parasitoid food web from tropical rainforest of Papua New Guinea. We DNA barcoded hosts, parasitoids and their tissue remnants and matched the sequences to our extensive library of local species....

Data from: The microsporidian parasite Vavraia culicis as a potential late life-acting control agent of malaria

Lena M. Lorenz & Jacob C. Koella
Microsporidian parasites are being considered as alternatives to conventional insecticides for malaria control. They should reduce malaria transmission by shortening the lifespan of female mosquitoes and thus killing them before they transmit malaria. As the parasite replicates throughout the mosquito’s life, it should have little detrimental effects on young mosquitoes, thus putting less selection pressure on the hosts to evolve resistance. Here we examined these expectations for the microsporidian Vavraia culicis on Anopheles gambiae Giles...

Microstructure control in Ti-6246

Abigail Ackerman
Titanium alloys are widely used in gas turbine engines due to their high specific fatigue strength and ability to retain that strength up to temperatures in the range of 600°C. The alloy Ti-6Al-2Sn-4Zr-6Mo is used in the intermediate pressure compressor of the gas turbine engine, with a yield strength of around 1.1GPa. It has a microstructure of primary α laths within a β matrix. Between the primary α are much finer secondary α laths, creating...

On tilts of certain infinite level shimura varieties

Raffael Singer
Scholze's Siegel modular varieties $\cX_{\Gamma(p^\infty)}$ over a mixed characteristic perfectoid field are known to be perfectoid, yet their tilt remains somewhat elusive. We give two different methods to describe the tilt of spaces related to $\cX_{\Gamma(p^\infty)}$. The first, following an idea of Lurie, uses Drinfeld level structures to construct integral perfectoid models of infinite level Shimura curves. For the second method we show how to recover the Tate module of the universal family of abelian...

Efficient numerical modelling of the ultrasonic scattering from complex surface-breaking defects

Richard Phillips
Ultrasonic testing is routinely used in the nuclear power generation industry to assess the structural integrity of plant components. The regulatory nature of the industry means that ultrasonic inspection procedures require substantiation through experimental trials and semi-analytical simulation, which can be costly and time-consuming. Furthermore, due to the complex defect and component geometries that are commonly encountered in the industry, the generation of evidence that accurately represents real inspections can be challenging. Numerical modelling techniques...

The impact of human immunodeficiency virus-1 viral replicative capacity on infection of human cervical and rectal tissue explants ex vivo

Robert Kipyegon Langat
Characterization of the targets and kinetics of HIV infection within rectal and genital tissues is central to the assessment of novel prevention agents. The ex vivo models available are helpful for studying the initial stages of HIV‐1 infection, such as defining the primary HIV target cells and the factors that influence viral replication kinetics. Five HIV-1 clade C, 1 clade A and 1 clade A/D HIV-1 TF variants were isolated from IAVI Protocol C; a...

Elastic wave propagation in polycrystals

Ming Huang
Scattering occurs as elastic waves propagate through a random polycrystalline medium, exhibiting scattering-induced attenuation and velocity dispersion. These behaviours carry bulk information about microstructure and can therefore be used for microstructure characterisation. The purpose of this thesis is to gain knowledge about the behaviour of elastic waves in polycrystals in order to facilitate the characterisation of microstructure. This thesis contributes mainly in six aspects. First, a theoretical second-order approximation (SOA) model is developed to calculate...

Laser-based measurements of liquid-liquid mixing in horizontal pipes by transverse jets

Stuart Fraser Wright
Low pipeline velocities lead to stratification of liquid-liquid flows, resulting in phase slip where the in situ phase fractions differ from the input fractions. This prevents samples being obtained that are representative of these flow’s phase fractions, and thus, mixing is used to overcome stratification. This work investigates pipeline jet mixers, obtaining measurements for comparison with theory. A review of jets for mixing is presented which establishes that few studies have been published on liquid-liquid...

Effects of strain-rate and temperature on ductile damage and Fracture of metallic materials

Alexander Sancho Garcia
Ductile damage appears in metallic materials when they undergo sufficiently high plastic strain. It is caused by voids and produces degradation on the mechanical properties that eventually leads to the ductile fracture of the material. Like other properties, this behaviour is affected by the temperature and velocity of material deformation. This thesis investigates the effects that temperature and strain-rate have on ductile damage from an experimental and a modelling point of view, and explores innovative...

Multiple poles of the motivic zeta functions and the monodromy property

Luigi Lunardon
This thesis summarizes the results of my research during the years of my Ph. D. at Imperial College London. I was mostly concerned with questions involving the motivic zeta function for degenerating Calabi-Yau varieties and the monodromy properties for these degenerations; in parallel to this research, I had a small side project on simplicial contractions. The first question we investigated is related to the monodromy property for K3 surfaces which admits triple-points-free models. These Calabi-Yau...

Optimising synthetic biosynthesis of natural products by yeast genome engineering

Glen Oliver Gowers
The sustainable manufacturing of products is a cornerstone of society’s move towards a sustainable circular economy. Many industrial specialty and bulk chemicals that are normally derived from fossil fuel can also be made by engineering microbes with biosynthetic pathways. However, augmenting these microbes to reach industrial scale remains a bottleneck in adoption of biological manufacturing practices. Many new synthetic biology tools are being developed to address this bottleneck, leveraging the application of engineering principles to...

Advances in network visualisation with an application to serious games

Jonathan Xiang-Sheng Zheng
This thesis concerns the visualisation of networks, through an in-depth study into the node-link diagram representation. Three subtopics are explored within this space. The first is the problem of node layout, where the optimisation of a popular energy function, known as stress, is improved through an algorithm known as stochastic gradient descent. The second is the method of edge bundling, where the idea of hierarchical edge bundling is explored in the absence of a known...

Cryo-EM studies of CMG translocation and cohesin loading

Carl Patrik Eickhoff
Before mitosis, the genome must be replicated in the parental cell and sister chromatids must be tethered to ensure accurate division of genes between daughter cells. Within the replisome, DNA unwinding is facilitated by the CMG helicase which contains a hexameric ATPase motor encircling the leading strand template. Intriguingly, the helicase polarity, the mechanism of translocation and how CMG- bound replisome factors such as Mcm10, the MCT complex and Polε affect the helicase has remained...

Strengthening human-robot symbiosis through multimodal sensing

Daniel Freer
As robotic technology has advanced throughout the ages, one of its primary functions has been to assist humans in completing difficult or dangerous tasks. Through the lens of outer space and healthcare, this thesis explores the possibility for a symbiotic relationship between humans and assistive robots by improving training protocols and with enhanced sensor data processing. This relationship is explored through several technologies: 1) a telerobotic simulator for training; 2) a wearable robotic sensing system...

Optimisation of gas field portfolios in the presence of uncertainty

Yaser Obiedallah Khojah
The study proposes an approach that incorporates both surface and subsurface parameters of gas projects in a portfolio model called the integrated stochastic gas economic optimisation model (ISGEM_opt). The model uses Monte Carlo simulation and genetic algorithms (GAs) to optimise the portfolio’s production strategy and satisfy contractual requirements under gas-in-place uncertainty. The production strategy is defined as the production rate and the starting time of each field in the portfolio. The optimised strategy demonstrates how...

Health in the climate crisis: a guide for health leaders

J Roland, N Kurek & D Nabarro
The WISH Health In The Climate Crisis: A Guide For Health Leaders report takes a fresh look at the issues to emerge with propositions that are relevant to practitioners and policymakers, encompassing climate change as a human health emergency and threat to health systems, while proposing health as an innovative lever for action.

The digital mental health revolution: Transforming care through innovation and scale-up

J Roland, E Lawrance, T Insel & H Christensen
The report reviews how to prepare and navigate innovations and their potential to address critical health needs.

Measurements of the CP properties of the Higgs boson couplings to tau leptons and top quarks with the CMS experiment

Albert Kenneth Dow
Measurements of the CP structure of the Higgs boson coupling to tau leptons and top quarks using data collected at the CMS experiment during 2016, 2017 and 2018 are presented. The dataset corresponds to a total integrated luminosity of 137 fb-1 at a centre-of-mass energy of 13 TeV. For these measurements, events with two tau-leptons in the final state are selected. The effective CP mixing angle for the Higgs boson to top quark coupling is...

Physical constraints from holographic duality

Krai Cheamsawat
The material presented in this thesis mainly consists of two parts under the umbrella topic of Holographic Duality or the AdS/CFT correspondence. In Part II we are mainly interested in the properties of energetic quantities, namely, the energy and free energy of Conformal Field Theory (CFT) under de- formations of spacetime geometry in (2+1) dimensions. By using holography together with analytic and numerical techniques, we find many results on monotonic decreasing of the energy/free energy...

Data learning for human pose tracking

Caterina Buizza
One of the most pressing problems in data-driven models is how to include latent data information in the model-building process. This could help to reduce the amount of data required for training in machine learning applications. Pose tracking is a field currently dominated by data-driven models and where the collection of large, labeled datasets is difficult and time intensive. We believe this is an application that could benefit significantly from the inclusion of structure in...

Synthesis of macrocycles via olefin metathesis: process intensification using organic solvent nanofiltration

Anna Cupani
Macrocycles are an important feature of many pharmaceutical compounds. They combine high target selectivity and lower metabolic degradation than acyclic analogues but are difficult to synthesise and mostly extracted from natural sources. With the discovery of olefin metathesis reaction, cycles of different sizes can now be obtained efficiently via Ring Closing Metathesis (RCM). To avoid side-product formation, the cyclization is done in extremely diluted conditions. This approach requires large amounts of solvents, is expensive and...

Observations of microstructure evolution and damage of SAC305 solder alloys during thermal and mechanical loadings

Tianhong Gu
Creep of directionally solidified Sn-3Ag-0.5Cu wt.% dog-bone samples with a controlled <110> or <100> fibre texture is investigated under constant load tensile testing (stress level: 17 - 44 MPa) and at a range of temperatures (298 – 473 K). The tensile creep strain rate and the localised strain gradient are studied by two-dimensional optical digital image correlation. A transition of creep mechanisms from climb-controlled dislocation creep to lattice-limited diffusion creep is found beyond ~ T/T_M...

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