5,723 research outputs found
Manipulating and assembling metallic beads with Optoelectronic Tweezers
Optoelectronic tweezers (OET) or light-patterned dielectrophoresis (DEP) has been developed as a
micromanipulation technology for controlling micro- and nano-particles with applications such as
cell sorting and studying cell communications. Additionally, the capability of moving small objects
accurately and assembling them into arbitrary 2D patterns also makes OET an attractive technology for
microfabrication applications. In this work, we demonstrated the use of OET to manipulate conductive
silver-coated Poly(methyl methacrylate) (PMMA) microspheres (50ÎŒm diameter) into tailored patterns.
It was found that the microspheres could be moved at a max velocity of 3200ÎŒm/s, corresponding
to 4.2 nano-newton (10â9N) DEP force, and also could be positioned with high accuracy via this DEP
force. The underlying mechanism for this strong DEP force is shown by our simulations to be caused
by a significant increase of the electric field close to the particles, due to the interaction between the
field and the silver shells coating the microspheres. The associated increase in electrical gradient causes
DEP forces that are much stronger than any previously reported for an OET device, which facilitates
manipulation of the metallic microspheres efficiently without compromise in positioning accuracy and is
important for applications on electronic component assembling and circuit construction
Channel integrated optoelectronic tweezer chip for microfluidic particle manipulation
Light patterned electrical fields have been widely used for the manipulation of microparticles,
from cells to microscopic electronic components. In this work, we explore a novel
electromechanical phenomenon for particle focusing and sorting where the electrical field
patterns are shaped by a combination of the light patterned photoconductor and the channel
geometry. This effect results from the combination of particle polarisation described by
the ClausiusâMossotti relation and the engineering of large electric gradients produced by
choosing the channels height to suit the size of the particles being manipulated. The matched
geometry increases the distortion of the field created by a combination of the illuminated
photoconductor and the particles themselves and hence the non-uniformity of the field they
experience. We demonstrate a new channel integration strategy which allows the creation of
precisely defined channel structures in the OET device. By defining channels in photoresist
sandwiched between upper and lower ITO coated glass substrates we produce robust channels
of well controlled height tailored to the particle. Uniquely, the top substrate is attached before
photolithographically defining the channels. We demonstrate versatile control using this effect
with dynamically reconfigurable light patterns allowing the retention against flow, focusing
and sorting of micro particles within the channels. Contrary to traditional designs, this channel
integrated device allows patterned micro channels to be used in conjunction with conductive
top and bottom electrodes producing optimal conditions for the dielectrophoretic manipulation
as demonstrated by the rapid flow (up to 5mm sâ1
) in which the particles can be focuse
Blood markers for cancer
Cancer Research UKNational Institute for Health Research (NIHR)Policy Research Unit in Cancer Awareness, Screening and Early DiagnosisDepartment of Healt
An international comparative study of blood pressure in populations of European vs. African descent
Background: The consistent finding of higher prevalence of hypertension in US blacks compared
to whites has led to speculation that African-origin populations are particularly susceptible to this
condition. Large surveys now provide new information on this issue.
Methods: Using a standardized analysis strategy we examined prevalence estimates for 8 white
and 3 black populations (N = 85,000 participants).
Results: The range in hypertension prevalence was from 27 to 55% for whites and 14 to 44% for
blacks.
Conclusions: These data demonstrate that not only is there a wide variation in hypertension
prevalence among both racial groups, the rates among blacks are not unusually high when viewed
internationally. These data suggest that the impact of environmental factors among both
populations may have been under-appreciated
Evaluating hospital infection control measures for antimicrobial-resistant pathogens using stochastic transmission models: Application to vancomycin-resistant enterococci in intensive care units
Nosocomial pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE) are the cause of significant morbidity and mortality among hospital patients. It is important to be able to assess the efficacy of control measures using data on patient outcomes. In this paper, we describe methods for analysing such data using patient-level stochastic models which seek to describe the underlying unobserved process of transmission. The methods are applied to detailed longitudinal patient-level data on vancomycin-resistant Enterococci from a study in a US hospital with eight intensive care units (ICUs). The data comprise admission and discharge dates, dates and results of screening tests, and dates during which precautionary measures were in place for each patient during the study period. Results include estimates of the efficacy of the control measures, the proportion of unobserved patients colonized with vancomycin-resistant Enterococci, and the proportion of patients colonized on admission. </jats:p
Emerging pathogenic links between microbiota and the gut-lung axis
© 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved. The microbiota is vital for the development of the immune system and homeostasis. Changes in microbial composition and function, termed dysbiosis, in the respiratory tract and the gut have recently been linked to alterations in immune responses and to disease development in the lungs. In this Opinion article, we review the microbial species that are usually found in healthy gastrointestinal and respiratory tracts, their dysbiosis in disease and interactions with the gut-lung axis. Although the gut-lung axis is only beginning to be understood, emerging evidence indicates that there is potential for manipulation of the gut microbiota in the treatment of lung diseases
Reversible DNA micro-patterning using the fluorous effect
We describe a new method for the immobilisation of DNA into defined patterns with sub-micron resolution, using the fluorous effect. The method is fully reversible via a simple solvent wash, allowing the patterning, regeneration and re-patterning of surfaces with no degradation in binding efficiency following multiple removal/attachment cycles of different DNA sequences
Hydrodynamics, erosion and accretion of intertidal mudflats in extremely shallow waters
© 2019 Elsevier B.V. Intertidal flats are shallow-water environments that undergo cyclical variations in water depth, leading to a frequent occurrence of extremely shallow water stages (ESWS; water depths 0.2 m), and the rate of change was an order of magnitude faster than during RDWS. This larger and faster bed-level change occurred even though the ESWS duration only accounted for 10% of the entire tidal cycle. This result occurred because the bed shear stress due to combined currentâwave action during ESWS, was, on average, two times higher than during RDWS at the flood stage causing more extensive erosion. Whereas during the ebb stage, this shear stress during ESWS was only half of that during RDWS resulting in greater accretion. The main implications of these results are that, because ESWS occur frequently (twice every tide) and are associated with large bed shear stress and bed-level changes, these conditions are likely to play an important role in morphological changes of intertidal flats. Our study shows that ESWS have a key influence on intertidal flat hydrodynamics and sediment dynamics. Thus our results are the basis for an improved understanding of the coastal morphodynamic processes on intertidal flats
Erosion and Accretion on a Mudflat: The Importance of Very Shallow-Water Effects
Understanding erosion and accretion dynamics during an entire tidal cycle is important for assessing their impacts on the habitats of biological communities and the longâterm morphological evolution of intertidal mudflats. However, previous studies often omitted erosion and accretion during very shallowâwater stages (VSWS, water depthsâ0.2 m (i.e., probe submerged) are considered. These findings suggest that the magnitude of bedâlevel changes during VSWS should not be neglected when modeling morphodynamic processes. Our results are useful in understanding the mechanisms of microâtopography formation and destruction that often occur at VSWS, and also improve our understanding and modeling ability of coastal morphological changes
Improving health and well-being through community health champions: a thematic evaluation of a programme in Yorkshire and Humber.
AIMS: The contribution that lay people can make to the public health agenda is being increasingly recognised in research and policy literature. This paper examines the role of lay workers (referred to as 'community health champions') involved in community projects delivered by Altogether Better across Yorkshire and Humber. The aim of the paper is to describe key features of the community health champion approach and to examine the evidence that this type of intervention can have an impact on health. METHODS: A qualitative approach was taken to the evaluation, with two strands to gathering evidence: interviews conducted with different stakeholder groups including project leads, key partners from community and statutory sectors and community workers, plus two participatory workshops to gather the views of community health champions. Seven projects (from a possible 12) were identified to be involved in the evaluation. Those projects that allowed the evaluation team to explore fully the champion role (training, infrastructure, etc.) and how that works in practice as a mechanism for empowerment were selected. In total, 29 semi-structured interviews were conducted with project staff and partners, and 30 champions, varying in terms of age, gender, ethnicity and disability, took part in the workshops. RESULTS: Becoming a community health champion has health benefits such as increased self-esteem and confidence and improved well-being. For some champions, this was the start of a journey to other opportunities such as education or paid employment. There were many examples of the influence of champions extending to the wider community of family, friends and neighbours, including helping to support people to take part in community life. Champions recognised the value of connecting people through social networks, group activities, and linking people into services and the impact that that had on health and well-being. Project staff and partners also recognised that champions were promoting social cohesiveness and helping to integrate people into their community. CONCLUSIONS: The recent public health White Paper suggested that the Altogether Better programme is improving individual and community health as well as increasing social capital, voluntary activity and wider civic participation. This evaluation supports this statement and suggests that the community health champion role can be a catalyst for change for both individuals and communities
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