1,120 research outputs found
The static and dynamic response of SU-8 electrothermal microgrippers of varying thickness
This work presents an investigation into the effect on dynamic response of SU-8 microgrippers due to varying thickness, and subsequent validation via COMSOL Multiphysics simulations and thermal camera profiling during actuation. The tweezer-like microgrippers can easily manipulate, with a high degree of control, cells and particles with diameters as small as 10 μm, without using an impractical operating voltage or generating excessive heat. However, in order to fully exploit the versatility of the devices, their response characteristics must be fully understood as material and/or dimension parameters change. Therefore an investigation took place to determine the effects of device thickness on functionality of the device, including the drive current required to actuate the gripper and the speed of actuation. Furthermore, an infrared camera was used to characterise the thermal response of the device. Finally, a simulation of the temperature profile and deflection dimension has been developed in order to verify the findings and further investigate and predict the effects of design variations
Interannual variability of tropical cyclone activity along the Pacific coast of North America
AbstractThe interannual variability of near-coastal eastern North Pacific tropical cyclones is described using a data set of cyclone tracks constructed from U.S. and Mexican oceanic and atmospheric reports for the period 1951-2006. Near-coastal cyclone counts are enumerated monthly, allowing us to distinguish interannual variability during different phases of the May-November tropical cyclone season. In these data more tropical cyclones affect the Pacific coast in May-July, the early months of the tropical cyclone season, during La Niña years, when equatorial Pacific sea surface temperatures are anomalously cool, than during El Niño years. The difference in early season cyclone counts between La Niña and El Niño years was particularly pronounced during the mid-twentieth century epoch when cool equatorial temperatures were enhanced as described by an index of the Pacific Decadal Oscillation. Composite maps from years with high and low near-coastal cyclone counts show that the atmospheric circulation anomalies associated with cool sea surface temperatures in the eastern equatorial Pacific are consistent with preferential steering of tropical cyclones northeastward toward the west coast of Mexico
Pond biodiversity and habitat loss in the UK
Ponds are common landscape features but have been poorly studied compared to other
freshwater habitats in the UK, despite their high frequency of occurrence. In the last
century, many ponds have been lost and those that remain face increasing pressure due to
agricultural land drainage, pollution and urban development. However, ponds provide
important habitats for diverse floral and faunal communities including a number of rare
taxa of conservation interest. This paper examines the biodiversity and wider
environmental value of ponds with particular reference to the aquatic invertebrate and
amphibian communities they support, and the adverse impact of anthropogenic activity on
their aquatic habitats
Inequalities in the dental health needs and access to dental services among looked after children in Scotland: a population data linkage study
Background: There is limited evidence on the health needs and service access among children and young people who are looked after by the state. The aim of this study was to compare dental treatment needs and access to dental services (as an exemplar of wider health and well-being concerns) among children and young people who are looked after with the general child population.
Methods: Population data linkage study utilising national datasets of social work referrals for ‘looked after’ placements, the Scottish census of children in local authority schools, and national health service’s dental health and service datasets.
Results: 633 204 children in publicly funded schools in Scotland during the academic year 2011/2012, of whom 10 927 (1.7%) were known to be looked after during that or a previous year (from 2007–2008). The children in the looked after children (LAC) group were more likely to have urgent dental treatment need at 5 years of age: 23%vs10% (n=209/16533), adjusted (for age, sex and area socioeconomic deprivation) OR 2.65 (95% CI 2.30 to 3.05); were less likely to attend a dentist regularly: 51%vs63% (n=5519/388934), 0.55 (0.53 to 0.58) and more likely to have teeth extracted under general anaesthesia: 9%vs5% (n=967/30253), 1.91 (1.78 to 2.04).
Conclusions: LAC are more likely to have dental treatment needs and less likely to access dental services even when accounting for sociodemographic factors. Greater efforts are required to integrate child social and healthcare for LAC and to develop preventive care pathways on entering and throughout their time in the care system
Carbon nanotubes : from molecular to macroscopic sensors
The components that contribute to Raman spectral shifts of single-wall carbon nanotubes (SWNT’s) embedded in polymer systems have been identified. The temperature dependence of the Raman shift can be separated into the temperature dependence of the nanotubes, the cohesive energy density of the polymer, and the buildup of thermal strain. Discounting all components apart from the thermal strain from the Raman shift-temperature data, it is shown that the mechanical response of single-wall carbon nanotubes in tension and compression are identical. The stress-strain response of SWNT’s can explain recent experimental data for carbon nanotube-composite systems
Solar Flares and Coronal Mass Ejections: A Statistically Determined Flare Flux-CME Mass Correlation
In an effort to examine the relationship between flare flux and corresponding
CME mass, we temporally and spatially correlate all X-ray flares and CMEs in
the LASCO and GOES archives from 1996 to 2006. We cross-reference 6,733 CMEs
having well-measured masses against 12,050 X-ray flares having position
information as determined from their optical counterparts. For a given flare,
we search in time for CMEs which occur 10-80 minutes afterward, and we further
require the flare and CME to occur within +/-45 degrees in position angle on
the solar disk. There are 826 CME/flare pairs which fit these criteria.
Comparing the flare fluxes with CME masses of these paired events, we find CME
mass increases with flare flux, following an approximately log-linear, broken
relationship: in the limit of lower flare fluxes, log(CME mass)~0.68*log(flare
flux), and in the limit of higher flare fluxes, log(CME mass)~0.33*log(flare
flux). We show that this broken power-law, and in particular the flatter slope
at higher flare fluxes, may be due to an observational bias against CMEs
associated with the most energetic flares: halo CMEs. Correcting for this bias
yields a single power-law relationship of the form log(CME mass)~0.70*log(flare
flux). This function describes the relationship between CME mass and flare flux
over at least 3 dex in flare flux, from ~10^-7 to 10^-4 W m^-2.Comment: 28 pages, 16 figures, accepted to Solar Physic
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