585 research outputs found
Langevin dynamics in constant pressure extended systems
No full textThe advantages of performing Langevin dynamics in extended systems are discussed. A simple Langevin dynamics scheme for producing the canonical ensemble is reviewed, and is then extended to the Hoover ensemble. We show that the resulting equations of motion generate the isobaric–isothermal ensemble. The Parrinello–Rahman ensemble is then discussed and we show that despite the presence of intrinsic probability gradients in this system, a Langevin dynamics approach samples the extended phase space in the correct fashion. The implementation of these methods in the ab initio plane wave density functional theory code CASTEP [M. D. Segall, P. L. D. Lindan, M. J. Probert, C. J. Pickard, P. J. Hasnip, S. J. Clarke, and M. C. Payne, J. Phys.: Condens. Matter 14, 2717 (2003)] is demonstrated
Microsatellite cross-amplification in coccolithophores: application in population diversity studies
No full textThe development and isolation of microsatellites entails a significant input of time and money. Therefore there is an interest in using existing microsatellites on species from which markers have not yet been developed. Conservation of six previously identified microsatellite loci in the marine coccolithophorid species Emiliana huxleyi was found in a survey of two bloom forming coccolithophorid species –Gephyrocapsa oceanica and Coccolithus pelagicus. The number of alleles per locus varied from 1 to 8, and half of the microsatellite loci tested showed 4 or more alleles. The microsatellite markers used in this study may be applied to other coccolithophorid species for population analysis, eliminating the time-consuming, costly development of microsatellite markers for other coccolithophorid species
Optimal heat transfer design for district-heating and cooling pipelines in air-filled cavities
No full textDistrict-heating and/or cooling systems are gradually becoming
popular all over the world for heating and/or cooling of
large premises.
Current conventional practice for the DHC underground
distribution networks is to place the supply and the return pipelines
side-by-side in air-filled trencRe's. However, t present
investigation has shown that by optimising the location of the
pipelines, the thermal insulation provided by the air around the
pipes can be maximised. This is achieved by placing the hot pipeline
above the cold one, the exact position depending upon the
temperatures involved. For most purposes, it is recommended that
the displacement ratio for the hot pipe is to be at -0.7 or -0.08
and that of the cold pipe at 0.05 or 0.67 for district heating or
cooling respectively [i. e. the hot and cold pipes being placed in
the upper and lower halves of the trench respectively].
Each chapter is presented in such a way that it can be read
independently of the others as far as possible
The appraisal of three gas-fired small-scale CHP systems.
No full textThe research in this thesis has undertaken a technical. economic and environmeiital
appraisal of three gas-fired, small-scale Combined Heat-and-Power (CHP) systenlýý
together with a study of the UK's electricity supply industry (ESi) and CHP market.
The purpose of each system is to attempt to utilise more of the heat and/or electricitY
output from the CHP unit. Within the non-technical research area, t hree
scenarios for the evolution of the ES1 have been developed to help establish llow
changes to forces acting within the industry, might affect the development of the
UK CHP market. New applications of several strategic management, alialysis tools
were used to develop and select the following scenarios: (i) 'N-ewa nd reduced ('02
limits set by the Climate Control Conference + stricter environmental legislatioil,
(ii) Changes to the Pool mechanism for pricing electricity. (iii) Business as usual.
It was concluded that in isolation scenarios I and 3 would aid the expansion of the,
CHP market, whereas scenario 2 is likely to hinder it. The selection of the scenarios
and the implications for the ESi and CHP market are supported by the opinions of
'industry specialists', which were solicited in a survey specifically undertaken for
this study.
The investigation into the first of the three technical systems involves the substitution
of two separate CHP units in place of a single larger unit. The intention
is to operate the larger of the two CHP units at maximum output to satisfy the
base heat-load and to use the second unit for meeting peak loads. The results for
five test-cases were produced via a newlY-developed predictive model, and indicated
that it is possible, for one of the case studies considered, to achieve shorter
pay-back periods when using the double-unit - with a higher availability of 9.5% -
rather than the single-unit system. In the other two cases (where CHP is a viable
economic option), longer pay-back periods ensue by the installation of the twounit
rather than the single-unit system. The operation of the two-unit system call
potentially increase energy-utilisation from the CHP units at one of the other sites'.
Furthermore, the proposed system can offer, in some cases, significant secondarý'
benefits, which could encourage a potential investor in the technology. These benefits
include the increased heat- an d-elect ri city output, increased availability from
the system, back-up from the secondary unit if one unit fails.
The second system determines the viability of an integrated small-scale CHP and
TES system. Another predictive model was developed and tested on five test -case",.
It was found that there is insufficient potential for the system and that the pot(, iitial
is limited by the following factors (i) CHP-sizing methodology, (ii) the relat IvCIN,
high capital cost for TEs hardware and installation, (iii) the relatively low econwilic
value attributed to heat and (iv) the availability of IoN%-pricedo ff-peak electricitv.
An industrial case study provided a rare and useful operational exainple of tlic
proposed system and the findings indicated that the heat-store could reduce i he
energy and monetary expenditures by up to 2.8/7c of the site's annual gas usage.
displacing approximately 30 tones Of C02 emissions each year. Howe\-er, becauýw
of the high financial cost of the TES components and installation. the pay-back
period produced would rarely be acceptable to a prospecti\-e investor. except in
exceptional circumstances.
Finally, the viability of an integrated CHP/absorption chiller systeni was in\-(, stigated.
The effectiveness of these types of systems are dependent on several factors,
namely: the source-water temperature from the hot-engine CHP unit - for a high
cop - and the cooling load at the site, the cooling demand at the site and the
temperature of the cooling water. A first-stage predictive model was developed to
determine the initial appropriateness of the installation of the integrated system
at a local hospital for the first time. The indications were that the cooling demand
was too low and the surplus waste-heat from the CHP unit insufficient to make the
system viable at the site. A second working-system was studied with a full ('02
investigation undertaken. The intention was to compare the total C02 emissions
for the integrated CHP and absorption chiller system with those for a similarl. y
sized vapour-compression system. The results indicate that the installed systc1l)
will produce 0.30kgCO2/kWhcoolth compared with 0.27 kg and 0.32kg for two different
types of vapour compression systems at design conditions. If the CHP heat
output is increased - to supply all of the heat required by the absorption chiller -
then the proposed system can displace up to 0.06 kgC02 per kWhcoolth at design
conditions and 0.10 kgC02 per kWh of cooling delivered for lower cooling water
temperatures. This represents a reduction of 22% and 40% respectively, when
compared with the vap our- compressions system
Abundance of small individuals influences the effectiveness of processing techniques for deep-sea nematodes
No full textNematodes are the most abundant metazoans of deep-sea benthic communities, but knowledge of their distribution is limited relative to larger organisms. Whilst some aspects of nematode processing techniques, such as extraction, have been extensively studied, other key elements have attracted little attention. We compared the effect of (1) mesh size (63, 45, and 32 μm) on estimates of nematode abundance, biomass, and body size, and (2) microscope magnification (50 and 100×) on estimates of nematode abundance at bathyal sites (250-3100 m water depth) on the Challenger Plateau and Chatham Rise, south-west Pacific Ocean. Variation in the effectiveness of these techniques was assessed in relation to nematode body size and environmental parameters (water depth, sediment organic matter content, %silt/clay, and chloroplastic pigments). The 63-μm mesh retained a relatively low proportion of total nematode abundance (mean ±SD = 55 ±9%), but most of nematode biomass (90 ± 4%). The proportion of nematode abundance retained on the 45-μm mesh in surface (0-1 cm) and subsurface (1-5 cm) sediment was significantly correlated (P < 0.01) with %silt/clay (R² = 0.39) and chloroplastic pigments (R² = 0.29), respectively. Variation in median nematode body weight showed similar trends, but relationships between mean nematode body weight and environmental parameters were either relatively weak (subsurface sediment) or not significant (surface sediment). Using a low magnification led to significantly lower (on average by 43%) nematode abundance estimates relative to high magnification (P < 0.001), and the magnitude of this difference was significantly correlated (P < 0.05) with total nematode abundance (R²p = 0.53) and the number of small (≤ 250 μm length) individuals (R²p = 0.05). Our results suggest that organic matter input and sediment characteristics influence the abundance of small nematodes in bathyal communities. The abundance of small individuals can, in turn, influence abundance estimates obtained using different mesh sizes and microscope magnifications
A toolkit to explore lived experience of motivation: When words are not enough
No full textDesigning to support motivation is an increasingly important issue, especially as pervasive technologies are used to facilitate various healthy behaviour changes. There are many motivation theories but these do not map specifically to inform design. In ‘Motivating Mobility’ we explore the lived experiences of motivation of people with stroke, in order to design rehabilitation technologies. Motivation varies between people, between contexts and over time and can be ‘difficult to express’, particularly for those with communication problems. We describe development of a theoretically based toolkit, principled in both content and form, and using multiple modes of communication, aimed at gathering motivational requirements in order to inspire design. We show use of the toolkit, discuss the rich data collected and reflect on how well the approach works and ties requirements, via their elicitation tool, back to theory. This toolkit has potential to inform design for motivational effect in similar pervasive health applications
Stratigraphic visualisation for archaeological investigation
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The principal objective of archaeology is to reconstruct in all possible ways the life of a community at a specific physical location throughout a specific time period. Distinctly separate layers of soil provide evidence for a specific time period. Discovered artefacts are most frequently used to date the layer. An artefact taken out of context is virtually worthless; hence the correct registration of the layer in which they were uncovered is of great importance. The most popular way to record temporal relationships between stratigraphic layers is through the use of the 2D Harris Matrix method. Without accurate 3D spatial recording of the layers, it is difficult if not impossible, to form new stratigraphic correspondences or correlations.
New techniques for archaeological recording, reconstruction, visualisation and interpretation in 3D space are described in these works and as a result software has been developed. Within the developed software system, legacy stratigraphy data, reconstructed from archaeological notebooks can be integrated with contemporary photogrammetric models and theodolite point data representations to provide as comprehensive a reconstruction as possible.
The new methods developed from this research have the capability to illustrate the progression of the excavation over time. This is made possible after the entry of only two or more strata. Sophisticated, yet easy-to-use tools allow the navigation of the entire site in 3D. Through the use of an animation-bar it is possible to replay through time both the excavation period and the occupation period, that is to say the various time periods in antiquity when human beings occupied these locations.
The lack of complete and consistent recording of the soil layers was an issue that proved to be an obstacle for complete reconstruction during the development of these methods. A lack of worldwide archaeological consensus on the methods of stratigraphic recording inhibited development of a universal scientific tool. As a result, new recording methods are suggested to allow more scientific stratigraphic reconstruction
Assessing risk to native ecosystems: using exotic ants as a model
No full textInvasive species are widely recognised as drivers of ecological change. As such, understanding the processes that facilitate invasion success, and the potential mechanisms and magnitude of impact, are critical for effective biosecurity management. Predicting risk associated with exotic species, so that management actions can be justified, is a major challenge faced by pest managers. In this thesis, I present a conceptual framework for assessing ecological risk in natural ecosystems developed from natural hazard (earthquake) risk assessment frameworks, and apply this using exotic ants as a model. To assess the vulnerability of different ecosystems to exotic ant invasion, I replicated a sampling study conducted across the Auckland region in 2004, allowing a temporal aspect to be included in the analyses. I found open-canopy ecosystems, consisting of short stature vegetation, to be most vulnerable to exotic ant invasion with several exotic ant species found to be ubiquitous throughout. In comparison, the same species were generally limited to the edges of closed-canopy forest ecosystems, even after a 10-year period. I then focused on dietary impact-related research within open-canopy ecosystems. I assessed competition between native and invasive ants using isotopic niche overlap and co-occurrence patterns, as well as employing DNA metabarcoding, to understand what invertebrate taxa are most at risk via predation. Furthermore, I investigated the potential disruption of floral visitor networks by exotic ants through conducting surveys across the flowering plant community and using focal observations to determine whether ants may be competitively excluding important pollinators. I found trophic position varied between native and invasive ant species; although two invasive species represented the two lowest trophic positions, most other species reflected trophic positions similar to predators. There was evidence of competitive exclusion between a native and invasive ant species, as revealed through high isotope niche overlap and negative co-occurrence patterns. Exotic ants were found to be common floral visitors, although this varied spatially. The presence of exotic ants on flowers was associated with a significant, negative response by important insect pollinators. Overall, my research greatly contributes to the ecological risk assessment posed by exotic species in native ecosystems and contributes to the impact-based research of invasive ants
Emiliania huxleyi and climate change: a genetic and biogeographic investigation of bloom dynamics for a key phytoplankton species in the global carbon cycle
No full textEmiliania huxleyi is a ubiquitous coccolithophore present throughout the global ocean and capable of forming large blooms with significant effects on the global carbon cycle. Developing our understanding of E. huxleyi ecology is necessary in order to better quantify E. huxleyi’s role in the present carbon cycle, and to predict its role in the future carbon cycle under climate change scenarios. Major gaps in the understanding of E. huxleyi ecology were addressed using (1) controlled mesocosm experiments in June 2008 in Raunefjord, Norway, to map population genetics of E. huxleyi blooms in relation to ecological pressures (viruses and rapid growth), (2) biogeographic sampling of nannoplankton (2 - 20 ?m) in the SO, including E. huxleyi, to determine ecological pressures on E. huxleyi blooms in situ (environmental gradients), and (3) controlled iron (Fe) addition bioassay experiments in the SO to establish the role of Fe gradients in the nannoplankton community relative to the phytoplankton community.During the mesocosm experiments, 279 individual E. huxleyi cells were isolated to establish clonal cultures, of which 143 were successfully genotyped using 5 microsatellite molecular markers. Both high gene diversity and two distinct genotypic populations were detected over the bloom time series and are strong evidence for a large reservoir of genetic variability within the E. huxleyi species concept, which may translate into phenotypic plasticity, such as differing levels of viral resistance. In the SO, the spatial and temporal biogeography of the three most numerous mineralizing nannoplankton groups, the coccolithophore E. huxleyi, the smaller (<20 ?m) species of the diatom genus Fragilariopsis, and chrysophytes of the genus Tetraparma were defined using scanning electron microscopy (SEM) analysis in conjunction with an array of biological, physical, and chemical variables during two successive cruises to the Scotia Sea. Multivariate statistical analyses were used to identify the most influential environmental variables controlling mineralizing nannoplankton biogeography. Sea surface temperature (SST) and salinity were identified as primary variables and removed from the analysis, leaving frontal boundaries, macronutrient, and dFe concentrations significantly associated with a northern E. huxleyi-dominated community (group I; higher nutrients) and a southern Tetraparma- and Fragilariopsisdominated community (group II; lower nutrients). Estimates of biomass indicated that the Scotia Sea mineralizing nannoplankton community formed a substantial part (on average 13%) of the total phytoplankton community. The results of bioassay Fe incubations indicated a response in medium and large diatoms and E. huxleyi, and a number of microplankton (20 – 200 ?m) diatom species. Overall, the work contributes substantially to our understanding of the molecular population structure, extent of phenotypic plasticity, and environmental parameters affecting the key phytoplankton E. huxleyi
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