244 research outputs found
Control of drop positioning using chemical patterning
We explore how chemical patterning on surfaces can be used to control drop
wetting. Both numerical and experimental results are presented to show how the
dynamic pathway and equilibrium shape of the drops are altered by a hydrophobic
grid. The grid proves a successful way of confining drops and we show that it
can be used to alleviate {\it mottle}, a degradation in image quality which
results from uneven drop coalescence due to randomness in the positions of the
drops within the jetted array.Comment: 3 pages, 4 figure
What does a primary care annual review for RA include? A national GP survey
Letter to the edito
Modelling the costs and benefits of hybrid buses from a whole-life perspective
Hybrid electric-diesel engine technologies offer the potential to reduce fuel consumption in buses by around 40%. These savings
can largely be attributed to regenerative braking – the ability to store in a battery energy that would otherwise have been lost
under braking. Lower fuel consumption makes sense economically for bus operators through reduced running costs; hybrid
engines have other wider benefits, though, such as reducing emissions and noise, and providing smoother acceleration and
braking. The costs associated with hybrid technologies are significant, however, with hybrid vehicles currently costing around
50% more to buy than conventional buses.
With Alexander Dennis and BAE Systems, UCL is conducting a three-year systems engineering research and development
project to adapt and optimise hybrid buses for the UK and European market. This paper investigates one aspect of this project –
the costs and benefits of introducing hybrid bus technologies from a whole-life perspective. We find that fuel and emissions
savings alone do not provide a compelling case for hybrid buses based on current prices. However, as the cost of fuel rises, and
when the social and environmental impacts of motor vehicle use are better accounted for, hybrid technology outperforms
conventional diesel technology
Dynamic ductile to brittle transition in a one-dimensional model of viscoplasticity
We study two closely related, nonlinear models of a viscoplastic solid. These
models capture essential features of plasticity over a wide range of strain
rates and applied stresses. They exhibit inelastic strain relaxation and steady
flow above a well defined yield stress. In this paper, we describe a first step
in exploring the implications of these models for theories of fracture and
related phenomena. We consider a one dimensional problem of decohesion from a
substrate of a membrane that obeys the viscoplastic constitutive equations that
we have constructed. We find that, quite generally, when the yield stress
becomes smaller than some threshold value, the energy required for steady
decohesion becomes a non-monotonic function of the decohesion speed. As a
consequence, steady state decohesion at certain speeds becomes unstable. We
believe that these results are relevant to understanding the ductile to brittle
transition as well as fracture stability.Comment: 10 pages, REVTeX, 12 postscript figure
OCT Assisted Quantification of Vitreous Inflammation in Uveitis
Purpose: Vitreous haze (VH) is a key marker of inflammation in uveitis but limited by its subjectivity. Optical coherence tomography (OCT) has potential as an objective, noninvasive method for quantifying VH. We test the hypotheses that OCT can reliably quantify VH and the measurement is associated with slit-lamp based grading of VH. Methods: In this prospective study, participants underwent three repeated OCT macular scans to evaluate the within-eye reliability of the OCT vitreous intensity (VI). Association between OCT VI and clinical findings (including VH grade, phakic status, visual acuity [VA], anterior chamber cells, and macular thickness) were assessed. Results: One hundred nineteen participants were included (41 healthy participants, 32 patients with uveitis without VH, and 46 patients with uveitis with VH). Within-eye test reliability of OCT VI was high in healthy eyes and in all grades of VH (intraclass correlation coefficient [ICC] > 0.79). Average OCT VI was significantly different between healthy eyes and uveitic eyes without and uveitic eyes with VH, and was associated with increasing clinical VH grade (P < 0.05). OCT VI was significantly associated with VA, whereas clinical VH grading was not. Cataract was also associated with higher OCT VI (P = 0.03). Conclusions: OCT VI is a fast, noninvasive, objective, and automated method for measuring vitreous inflammation. It is associated with clinician grading of vitreous inflammation and VA, however, it can be affected by media opacities. Translational Relevance: OCT imaging for quantifying vitreous inflammation shows high within-eye repeatability and is associated with clinical grading of vitreous haze. OCT measurements are also associated with visual acuity but may be affected by structures anterior to the acquisition window, such as lens opacity and other anterior segment changes
The effect of interfacial adhesion on the mechanism for craze formation in polystyrene-glass bead composites
What young people report about the personal characteristics needed for social science research after carrying out their own investigations in an after-school club
Several arguments have been put forward about the benefits of young people carrying out their own social science research in terms of empowering their voices and their participation. Much less attention has been paid to investigating the understandings young people develop about the research process itself. Seven twelve-year-olds carried out self-directed social science research into a topic of their choice. Towards the end of their six months experience we used a questionnaire and follow-up semi-structured interviews to investigate, from a socio-cultural perspective, what the young people thought about being a researcher. Thematic analysis of the interviews identified three themes and eight subthemes suggesting that they were aware of: the need to demonstrate researcher/research integrity (be thorough, truthful, orderly, and have a good understanding of research process); the need for good interpersonal skills and standards; and good self-management skills (be resilient, agentic, committed, and good at time management). We discuss how first-hand social science research experience might: be relevant to several areas of schooling; give young people experience of the personal characteristics important for success; help young people to realise that they can be social science researchers, and offer advanced and novel learning experiences outside the constraints of the school curriculum
Diblock copolymers at a homopolymer-homopolymer-interface: a Monte Carlo simulation
The properties of diluted symmetric A-B diblock copolymers at the interface
between A and B homopolymer phases are studied by means of Monte Carlo (MC)
simulations of the bond fluctuation model. We calculate segment density
profiles as well as orientational properties of segments, of A and B blocks,
and of the whole chain. Our data support the picture of oriented ``dumbbells'',
which consist of mildly perturbed A and B Gaussian coils. The results are
compared to a self consistent field theory (SCFT) for single copolymer chains
at a homopolymer interface. We also discuss the number of interaction contacts
between monomers, which provide a measure for the ``active surface'' of
copolymers or homopolymers close to the interface
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