7440 research outputs found
Sort by
Developing 3D brain models for cell surface sugar targeting with bio-conjugated nanodiamonds
No full textEmpirical thesis.Bibliography: pages xi-xix.Chapter 1. Introduction -- Chapter 2. Materials and methods -- Chapter 3. Results -- Chapter 4. Discussion -- Chapter 5. Summary and conclusion -- References -- Appendix.Glycosylation is a post-translational modification that attaches sugar receptor chains to cell surface proteins and lipids. Abnormal glycosylation is evident during multiple chronic brain pathophysiologies such as Alzheimer's, Parkinson's and Huntington's diseases and brain cancer, making sugars excellent biomarkers for selective targeting of affected cells by sugar receptors such as lectins that bind to different cell surface glycan residues. We utilised 120nm fluorescent nanodiamonds with nitrogen vacancy centres that were bio-conjugated with lectins to target sugar structures on the surface of three types of cultured central nervous system cells: astrocytes, neurons and microglia. Functionalised nanodiamonds were thus used to investigate the in vitro expression of sialic acid and N-acetylglucosamine (using wheat germ agglutinin), fucose (Aleuria aurantia lectin), and high mannose and N-acetylglucosamine (using tomato lectin) on these brain cell types. The binding of nanodiamonds to these sugars to each cell type grown in standard 2D cultures and in newly developed natural 3D brain scaffold cell growth constructs was evaluated. As glycans are a major component of the cell surface as well as of the extracellular matrix and are highly important in cell-cell interactions, our new 3D models were developed to more closely represent in vivo central nervous system conditions for assessing sugar expression and nanodiamond binding and uptake in neurons, astrocytes and microglia.Mode of access: World wide web1 online resource (xi, 49, xii-xx pages) illustrations (some colour
Haemodynamic simulation and optimisation for the flow-diversion treatment of intracranial aneurysms
No full textEmpirical thesis.Thesis carried out as part of a co-tutelle arrangement with Tohoku University.Bibliography: pages 125-136.Chapter 1. Introduction -- Chapter 2. Materials and methods -- Chapter 3. Structural optimisation of flow-diverting stent -- Chapter 4. Haemodynamic simulation of flow-diversion treatments with stent compaction applied -- Chapter 5. Haemodynamic simulation of flow-diversion treatment with multiple flow-diverting stents -- Chapter 6. Investigation of incomplete stent expansion effects on aneurysmal haemodynamics -- Chapter 7. Applying computational simulation to the design of flow-diversion Tteatment : a showcase -- Chapter 8. Conclusion and outlook.Despite various complications reported, flow-diverting (FD) stent implantation has become a major mode of treatment for intracranial aneurysms. Review of literature suggests that the treatment outcomes are closely associated with the aneurysmal haemodynamics changed by the implanted stent. In this thesis, I sought to examine the haemodynamic changes following different strategies of FD treatment and provide practical solutions to improve the stent's flow-diversion efficacy.As the first accomplishment, I developed in Chapter 3 an automated optimisation method to be used to accommodate stent configuration to a specific aneurysm geometry. Adopting this method, wire structure of a stent can be modified to alter the local haemodynamics towards maximal reduction of the aneurysmal inflow. Furthermore, employing a virtual stent deployment technique and computational fluid dynamics analysis, I systematically investigated in Chapter 4 and 5 the aneurysmal haemodynamics following the flow-diversion treatment with a stent compaction technique applied or with dual-FD stents deployed - two of the most commonly adopted treatment strategies in the current interventional practice. These studies provided quantitative results illustrating stent wire characteristics and the subsequent aneurysmal haemodynamic changes in various flow-diversion scenarios. Finally, I examined in Chapter 6 the aneurysmal haemodynamics affected by incomplete stent expansion (IncSE) - a condition suspected to cause delayed aneurysm occlusion, for which various severities of IncSE occurring at different segments of the parent artery were modelled and examined. Results suggest that the effects of IncSE vary greatly with respect to the location where it occurs.Based upon this series of studies, a workflow was put forward to individualise the treatment plan corresponding to the haemodynamic characteristics of a specific patient, from the patient aneurysm model reconstruction, to computer-aided stent deployment rehearsal, and then to the haemodynamic outcome analysis to determine the most effective treatment plan prior to the real treatment. An example of implementing this workflow to predict the post-treatment haemodynamics thereby determining the most favourable treatment strategy was illustrated in detail in Chapter 7.Apart from this useful application, methodologies developed in the thesis, including the FD stent modelling technique, the stent structural optimisation method, the classification of stent compaction, and the in-house software for stent deployment simulation, would certainly contribute to future research and development of FD stents and interventional planning.Mode of access: World wide web1 online resource (xviii, 136 pages) colour illustration
Song cycle as life cycle: Mario Castelnuovo-Tedesco's The Divan of Moses Ibn Ezra and the persistence of memory
No full textTheoretical thesis.Bibliography: pages 264-274.Chapter 1. Rationale, research questions, analytical approaches, and research methodologies -- Chapter 2. Literature review -- Chapter 3. Theoretical framework: diaspora, identity, and memory -- Chapter 4. The 'Golden Age' of Spanish Jewry -- Chapter 5. Moses Ibn Ezra: a product of his age --Chapter 6. Towards conflict: the racial laws and their consequences -- Chapter 7. Biographical notes on the life and works of Mario Castelnuovo-Tedesco -- Chapter 8. The Divan of Moses Ibn Ezra and its musical, historical, and social contexts -- Chapter 9. Reading the Divan across the centuriesMario Castelnuovo-Tedesco was a prolific composer who gained reputation from the 1920s as a young writer of modern Italian music. Following implementation of Italy's antisemitic racial laws in 1939, Castelnuovo-Tedesco emigrat d to America. There, he became recognised within the Hollywood film-music industry and known as a major composer for the guitar, an instrument he did not play. Throughout his career Castelnuovo-Tedesco placed special emphasis on composing themes inspired by his Florentine background, by his Jewish roots, and by composing art song using great literary works. Connecting the visual to the aural, he was sometimes referred to as an ' impressionistic ' composer due to the highly visual atmospheres he depicted in his music, he utilised elements of ordered and clear Italian neoclassicism , emotional and melodic French neoromanticism, geometric German chromaticism, colourful chordal extensions, and dissonance in his music. This thesis takes as its focal point the last of his compositions that used culturally Jewish texts for its lyric and was written for guitar and voice. One of the great Jewish singer-poets of the Islamic period in Spain was Moses Ibn Ezra (c. 1055 - c.113 8), who was exiled from Granada. Castelnuovo-Tedesco used an English rendition of Ibn Ezra's secular poetry and in 1966 selected nineteen songs which became Opus 207, The Divan of Moses Ibn Ezra: A Cycle of Songs for Voice and Guitar. Themes that emerge in this sometimes dark song cycle are the pain of exile, love and friendship, morality, and mortality.Two lines of inquiry will be formed in this thesis. One line of inquiry focusses on the composition itself, to understand its musical and poetic significance. In doing so, it will arrive at some conclusions as to why Castelnuovo-Tedesco chose this poetic material, and in what respects it is a unique composition. The second major line of inquiry is contextualising the Divan as representative of a cultural continuum connecting medieval poet to the modern composer. Underpinning historical and musicological elements, use will be made of writings by philosophers, psychologists, cultural scientists, and historians to construct a theoretical framework highlighting the association that exiled Jewish diaspora populations maintained between their Jewishness and aesthetics, and highlighting the differentiation between commonality and connectivity in the Jewish historical experience. The goal of this research is to ascertain the socio-historical and cultural conditions that led Castelnuovo-Tedesco to the Divan and suggest some implications it has on the study of identity. The the oretical approach is cross-disciplinary and amplifies the conceptual frames of cultural identity, concepts of diaspora, and the transference of memory.1 online resource (x, 278 pages
Bivalve shells as paleo-proxy archives: assessment of the usefulness as environmental and climatic recorders in the Southern Hemisphere
No full textTheoretical thesis.Thesis by publication.Includes bibliographical references.Introduction -- 1. The freshwater bivalve Echyridella menziesii: a new environmental archive from Lake Rotorua, New Zealand -- 2. Temperature reconstructions by δ¹⁸O and Sr/Ca using freshwater bivalve Echyridella menziesii from New Zealand -- 3. The potential of three east Australian freshwater bivalve species as environmental proxy archives -- 4. Climate signals in the shells of Diplodon chilensis patagonicus (Haas, 1931) bivalves in northern Patagonia, Argentina -- 5. Medieval climatic anomaly signals in fossil Diplodon chilensis patagonicus (Haas, 1931) shells from northern Patagonia -- Conclusions.In contrast to other skeletal bio-carbonates, the potential of freshwater bivalves as environmental and climate archives has been less explored, despite the fact that freshwater bivalves are well-known to record environmental variables such as temperature, precipitation, primary productivity, and river discharge in multiple ways which facilitates the combination of numerous proxies that strengthens the proxy records. Although there are a large number of marine proxy studies in the southern hemisphere, the number of similar studies in freshwater environments are comparatively limited, creating a considerable lack of understanding on the past continental climate in the region. In this thesis, freshwater bivalves are studied from three different localities at similar latitudes in the southern hemisphere, namely New Zealand, Australia and South America, in order to identify the potential of five different species as new environmental proxy archives. The results show that physical and chemical characteristics in three studied species; Echyridella menziesii , Alathyria profuga and Diplodon chilensis patagonicus have the possibility to be used as proxies of numerous environmental and climatic variables. Echyridella menziesii and Alathyria profuga exhibit the suitability of using shell oxygen isotope ratio as a temperature proxy since temperature reconstructions using these proxies agree well (± 2.5 and ± 3.5 °C respectively) with instrumental temperature data. Similarly, Sr/Ca in Echyridella menziesii and Diplodon chilensis patagonicus can function as a proxy of ambient temperature as both exhibit significant correlations (r > 0.6, p < 0.05) with instrumental temperature. More importantly, this study introduces the use of two different empirical equations for summer and winter which improves the reliability in summer temperature reconstructions. Further, all three species exhibit distinct growth variations in responding to regional climatic phenomena such as the Southern Annular Mode and the El Niño southern oscillation. Both Echyridella menziesii and Diplodon chilensis patagonicus show a distinctive reduction in growth during El Niño years contrary to tree ring data from these regions. Finally, fossil Diplodon chilensis patagonicus shells are used to evaluate the environmental conditions during medieval times (1200 - 1350 cal. yr. BP) and identified the medieval climatic anomalies as variations in Sr/Ca ratios in the shells supporting similar findings in other paleoclimate proxy archives in Argentinean Patagonia. Additionally, this provides new estimates for lifespans and growth rates for all studied species. This thesis delivers three new proxy archives which are widespread in the southern hemisphere and have the potential to improve available proxy networks, thus enhancing the precision of spatially resolved continental-scale temperature reconstructions.1 online resource (ix, 205 pages : illustrations, maps
Investigation of molecular adaptations in Pseudomonas aeruginosa cystic fibrosis isolates
No full textThesis by publication..Includes bibliographical references.1. Introduction -- 2. Genetically and phenotypically distinct Pseudomonas aeruginosa cystic fibrosis isolates share a core proteomic signature -- 3. A cystic fibrosis Pseudomonas aeruginosa isolate specialised to catabolise nucleic acids -- 4. Pseudomonas aeruginosa inhibits the growth of Scedosporium aurantiacum, an opportunistic fungal pathogen isolated from the lungs of cystic fibrosis patients -- 5. Dual transcriptomics of host-pathogen interaction of cystic fibrosis isolate Pseudomonas aeruginosa PASSI with Danio rerio -- 6. Proteomics of hosts and pathogens in cystic fibrosis -- 7. Discussion -- Appendices.Pseudomonas aeruginosa is the major pathogen contributing to morbidity and mortality among patients with cystic fibrosis (CF) lung infections. The opportunistic pathogen, P. aeruginosa is metabolically versatile and broadly found in the environment and on various hosts. The metabolic versatility can be attributed to its relatively large genome. In the CF lung P. aeruginosa is exposed to a variety of selective pressures including the host immune response, different microorganisms, environmental heterogeneity and antibiotics. This work explores the genetic and phenotypic differences among P. aeruginosa strains isolated from the sputum of CF patients with the model P. aeruginosa strain PAO1. Comparison of P. aeruginosa CF isolates PASS1-4 reveal differences in genetic and phenotypic adaption to the CF lung environment, including phenotypic variation in virulence related traits such as swimming motility, biofilm formation and mucin binding. Proteomic analyses revealed patterns in protein expression common to the CF isolates, but distinct from PAO1. Investigation of the catabolic capabilities of the CF isolates revealed that PASS4 showed a dramatically decreased capacity for utilisation of carbon sources, growing well only on adenosine and inosine out of the substrates tested. This strain was also shown to grow well on DNA suggesting it may be adapted to growth on DNA in the CF lung. Transcriptomic and proteomic analyses of PASS4 and PAO1 grown on DNA revealed increased expression of many virulence genes. Mutants of PASS4 were obtained that had an expanded carbon catabolic phenotype, and sequencing of these mutants showed they all contained a mutation in the purK gene involved in purine biosynthesis, suggesting that the inability of PASS4 to grow on a range of carbon sources because it is a purine auxotroph. The exploration of bacterial-fungal interaction revealed the highly virulent CF isolate PASS1 inhibited the growth of the fungal pathogen Scedosporium aurantiacum. PASS1 also has a significant effect on eukaryotic model organism zebrafish. Dual host-pathogen transcriptomics revealed an arsenal of virulence factors contributing to PASS1 infection, while the zebrafish host expressed an array of innate immunity mechanisms involved in inflammation, infection and tissue injury. Overall, this thesis provides insights into the various adaptations and mechanisms of P. aeruginosa involved in surviving in the CF host environment.1 online resource (xxv, 257 pages
Dry surface biofilm a persistent source of pathogens in hospital: decontamination and infection control
No full textEmpirical thesis.Bibliography: pages 286-315.Introduction -- Chapter One. Review of literature -- Chapter Two. Material and methods -- Chapter Three. Biofilm : transmission and inactivation by heat -- Chapter Four. Developing novel chemistries for removing environmental surface biofilms to reduce hospital acquired infections -- Chapter Five. Development of multispecies dry surface biofilm model -- Chapter Six. Comparative proteomic profile : new insight of Staphylococcus aureus dry surface biofilm -- Chapter Seven. General discussion and conclusion -- References -- Appendix.Environmental surface cleaning and disinfection is crucial for preventing HAI and maintaining patient safety. However, biofilms incorporating multiple bacterial species form on dry hospital surfaces. These biofilms are tolerant to biocides making their eradication difficult. Persistence of pathogens on surfaces increases the risk of transmission and development of HAI.Aims:1) To determine if bacteria can be transmitted from dry surface biofilm (DSB) to healthcare workers' hands and through cotton sheets. 2) To develop and test new removal chemistries against dry surface biofilm utilising laboratory models. 3) To develop a mixed species biofilm model analogous to the hospital surface DSB to determine its composition, the effect of multiple species on biofilm's susceptibility to detergents and disinfectants and analyse proteomics and transcriptomics technique. 4) To investigate protein regulatory changes in DSB compared with traditional hydrated biofilm and confirmation with RT PCR.This study revealed that: 1) DSB is highly transmissible. The total bacterial number transferred are sufficient to cause disease. 2) Soil inactivates the commonly used disinfectants. Peracetic acid reduces 64% of the biofilm mass and >6 Log10 viability in single species DSB, 48% of the biofilm mass in mixed DSB in the presence of soil. 3) This study developed a mixed species DSB model with reproducible cell number within and between repeated experiments. This mixed biofilm model was employed to assess the effectiveness of disinfectants. 4) These findings clearly imply that S. aureus biofilms represent a unique growth condition in terms of overall numbers of differentially expressed distinct proteins and genes.This study establishes the transmissibility of bacteria from DSB affirming it to be a potential source of HAI and determined that currently surface disinfectants and methods are insufficient to completely eradicate DSB. This study also established different changes in protein and genetic expression in biofilm, this might act as target group to invent new effective disinfectant for complete eradication of DSB.Mode of access: World wide web1 online resource (xviii, 318 pages) illustrations (some colour
Gain characteristics in single-mode pumped diamond Raman lasers
No full textEmpirical thesis.Bibliography: pages 165-180.1. Introduction -- 2. Conceptual framework and cavity design -- 3. Continuous wave external cavity KYW Raman laser -- 4. Single longitudinal mode diamond Raman lasers-- 5. Second Stokes SLM laser -- 6. Active cavity length stabilisation -- 7. Conclusion -- Appendices -- References.Single longitudinal mode (SLM) lasers are significant for applications in spectroscopy, precision measurements, and high-resolution interferometry. The techniques for achieving SLM in inversion lasers are well-developed, as are also frequency extension by frequency conversion using harmonic crystals and optical parametric oscillators. In contrast, Raman lasers, which are well-known for having advantages for diversifying wavelength range and producing high-quality output beams, are much more immature in terms of SLM operation.This thesis presents an experimental approach to demonstrate SLM operation in a standing wave crystalline Raman laser. Theoretical concepts are developed to elucidate the gain saturation mechanisms and mode competition in Raman lasers. It is shown that gain saturation is homogeneous for narrow linewidth pumping and that the absence of spatial hole burning in a Raman gain medium leads to the possibility of intrinsically stable SLM operation.This concept is implemented in narrow-line width pumped external cavity Raman lasers in the continuous wave regime. Two Raman crystals –diamond and potassium yttrium tungstate (KYW) are investigated to understand the effects of material properties on longitudinal mode structure.In the case of KYW, it is seen that the laser output spectrum and efficiency were greatly influenced by a lesser-known low-frequency phonon mode (87 cm–1), which is shown to havehigh gain coefficient higher than the mode currently accepted as the primary mode. Owing to the complexity of the laser output spectrum due to the participation of this low-frequency mode in the Raman frequency conversion process, investigation of the mode spectrum was challenging. However, the low-frequency mode at 87 cm–1 is advantageous for applications requiring multi-wavelength laser sources. As the quantum defect is much lower than for the conventional phonon modes in Raman crystals, it could be used for beam enhancement and/or beam combination.Diamond is seen as a much better option for investigating SLM as it has a "pure" single phonon mode, in addition to its high Raman gain and superior thermal conductivity. Despite having 35 longitudinal modes in the diamond gain bandwidth (45 GHz), SLM operation is demonstrated at 1240 nm up to 4 W of Stokes output power for the free-running diamond Raman laser. Moreover, this SLM demonstration is significant as the gain medium wa spositioned at the midpoint of the standing-wave cavity, which would normally be unsuited to SLM operation in the case of an inversion laser. The pumping level and output power of this SLM operation are higher than the reported SLM inversion lasers. The coupling between the intracavity Stokes power and the optical cavity length via the thermo-optic effect and thermal expansion of diamond was found to be responsible for the multimode operation at higher powers.Extension to longer wavelengths through second Stokes generation was also investigated. The aggravated thermal effects in diamond and cascading effect on pump depletion led to the multimode operation at low output powers. As a result, a volume Bragg grating in a coupled cavity design was used to increase the SLM power. Up to 0.5W SLM power at 1485 nm wasdemonstrated with a frequency stability of the order of the pump frequency fluctuations. The feasibility of the DRL as a LIDAR transmitter was investigated through a demonstration of environmental water vapour detection.Finally, active stabilization of the cavity length was investigated to extend the range of power and to increase frequency stability. A novel variant of Hänsch-Couillaud (HC) technique for cavity locking was developed that is proposed to be based on polarisation dependent pump depletion. This successfully increased the maximum output power to 7.2 W, which is believed to be one of, if not the highest SLM power reported for a solid-state SLM oscillator. Stimulated Brillouin scattering is observed as parasitic effect but provides a novel platform for the future development of diamond Brillouin lasers.Mode of access: World wide web1 online resource (xxii, 180 pages) diagrams, graph
Dysprosium mid-infrared fibre lasers
No full textEmpirical thesis.Bibliography: pages 93-103.1. Introduction -- 2. Dysprosium and the rare earth dopants -- 3. Theory : optical fibre and lasers -- 4. In-band pumping at 2:8µm -- 5. Pumping at 1.7µm - source development -- 6. Near infrared pumping of dysprosium -- 7. Conclusion -- References.Optical sources in the mid-infrared have enabled an increasing number of applications in fields such as sensing, materials processing, and defence. While traditional mid-IR sources have often been based on nonlinear conversion in parametric oscillator devices, these systems are bulky, costly, and inefficient. In contrast, the past few decades have seen uoride glass based mid-IR fibre lasers advance from small scale laboratory demonstration, to advanced developmental systems, and even recently commercial products. The majority of this class of lasers have been based on erbium, or to a lesser extent, holmium-doped gain media. Both systems have achieved multi-watt output power, and have been demonstrated as ultra-fast pulsed systems down to pico- and even femto-second pulse duration. However, these systems share two fundamental limitations. One, the conversion efficiency is limited to less than 50%, which has led to a distinct slowdown in output power scalability. Two, both systems are limited in bandwidth, translating to holes in the optical spectrum which can be covered by fibre lasers.There is a third dopant element which exhibits emission in the same spectral region, but has been largely ignored: dysprosium. While the few demonstrations of dysprosium-doped mid-IR fibre lasers did not exceed performance of competing systems, there is much untapped potential remaining which is what this thesis aims to address. Specifically, two novel optical pumping schemes based on near- and mid-infrared are investigated which address the limitations of the previous dysprosium efforts, and the competing erbium and holmium basedsystems. Further, the viability of progressing these systems to operation in the pulsed regime is considered. As a whole, these investigations aim to both solidify dysprosium as a viable candidate for mid-IR fibre laser emission, and deepen the collective understanding of dysprosium as an active rare earth dopant.Mode of access: World wide web1 online resource (xiv, 103 pages) colour illustration
Particle air pollution and its implications in the Pacific Islands
No full textThesis by publication.Includes bibliographical references.1. Introduction -- 2. Pollutant concentration -- 3. Source contributions -- 4. Discussion -- Appendices.Emissions arising from diesel combustion and the open burning of wastes are of concern across the Pacific Islands. Using Suva, Fiji as a case study, particulate air quality was investigated from October 2014 to October 2015. Ambient particulate concentrations were determined for total, 10µm, 2.5 µm (PM2.5), 1 µm and ultrafine particle (<300 nm) size fractions at city, residential and background locations. Ion beam analysis, to determine elemental concentrations, focussed on the PM2.5 fraction, due to the strong evidence of adverse health impacts from PM2.5. Additionally, contemporary and fossil carbon percentages were determined. Sources of PM2.5 were quantified by emissions inventory as well as by statistical analysis of air sampling data. Mortality risk was determined using published risk data. Indoor PM2.5 concentrations and sources were also investigated. Ambient PM2.5 concentrations (mean one year) in Suva city were close to Australian standards (8 µg/m3). Residential area and indoor PM2.5 results demonstrated likely exceedance of these ambient standards. Emission inventory calculations showed diesel and waste burning to be large contributors to Suva’s airborne particulate, also reflected in elevated black carbon and ultrafine particle concentrations. Statistical analysis of elemental concentrations identified diesel combustion as a major contributor to Suva’s PM2.5 mass (21%), along with vehicle emissions (all fuel types 17%). Whilst waste burning (largely biomass) contributed only 8% to city PM2.5 mass, contemporary carbon concentrations indicated biomass burning contribution to airborne particulates in residential areas to be more than double compared to the city. Based on risk of black carbon exposure, mortality risk from diesel combustion in Suva (industrial, power generation and shipping) was estimated at 59 deaths per year; vehicle and open burning emissions also represented significant risk. Reduction of emissions from these three sources would improve air quality and reduce health risk. This applies for Suva and more broadly across the Pacific Islands region.1 online resource (252 pages : illustrations, maps
Search patterns of Myrmecia midas on different substrates at twilight and day
No full textEmpirical thesis.Bibliography: pages 17-19.Introduction -- Chapter 1. Setting the scene -- Chapter 2. Spelke's nativist position -- Chapter 3. The language embodied position -- Chapter 4. Enculturation -- Conclusions -- References.Australian night active bull ants, Myrmecia midas (subfamily: Myrmeciinae) were collected during their foraging trip in the twilight and displaced to a distant unfamiliar gridded (8m/8m) place. Their search paths were recorded under 3 different substrates at twilight and day: 1. on natural substrate (grass mixed with small wooden pieces), 2. on a uniform tarp surface, and 3. on a quasi-fractal substrate of two different substrates. On the natural substrate at twilight the smaller loops of the forager ants made bigger turn angles, smaller segment lengths, and a shorter distance from the start compared with searches by day. On the uniform (tarp) and quasi-fractal surfaces at twilight and day, the absolute turn angles and the average segment lengths did not differ significantly. But the average distances from the start were bigger on the fractal substrate than on the uniform tarp and distances from the start were bigger in day-light than in twilight on natural substrate. The data pattern replicated other data where the ants showed the expanding search pattern of travelling further and further from their starting point in the course of the search in all conditions. The exponential function (for the distribution of lengths of straight segments) best fitted the uniform tarp substrate and the stretched exponential best fitted the quasi-fractal substrate at twilight, while a bi-exponential provided the best fit for the natural substrate at twilight and day, as well as uniform tarp and quasi-fractal substrates by day. The bi-exponential may be common in search patterns of forager ants in unfamiliar natural and artificial environments.Mode of access: World wide web1 online resource (iii, 19 pages) colour illustration