Search

In this PhD, I have advanced the study of ground-based photometric observations in the near-infrared. Specifically, I have worked in the context of robotic exoplanet transit surveys in collaboration with the SPECULOOS Southern Observatory (SSO). Here, I targeted optimising the photometric precision of observing late M, L type stars by developing correction methods and a new instrument called SPIRIT. My first original contribution was the development of a correction method for the induced effects from varying precipitable water vapour (PWV) in our atmosphere, specifically on differentially resolved light curves from SSO. This work succeeded in reducing false variability of time-series data from late M, L type stars on both long and short timescales, to the extent of removing false transit features. In parallel, I performed a feasibility study of introducing new near-infrared instrumentation to SSO. One which would permit better photometric precision than the existing CCD Si based instrumentation, and likewise minimise the induced effects of PWV variability. An InGaAs based instrument, sensitive up to 1.62 µm was identified, and a custom wide-pass filter called zYJ was designed and manufactured to form SPeculoos' Infra-Red photometric Imager for Transits (SPIRIT). It proved to be a significantly lower-cost alternative to the traditionally used HgCdTe based instrumentation, as well as being better suited to robotic observatories. On sky results of SPIRIT at SSO successfully demonstrated better photometric precision for stars below 2550 K than the existing instrumentation. It similarly demonstrated the benefit of seeing further into the infrared for minimising the observed variability of M, L type stars. Finally, the custom designed wide-pass filter, zYJ, successfully demonstrated a significantly lower sensitivity to PWV variability. These results pave a new avenue for ground-based near-infrared robotic exoplanet transit surveys, as well as similar time-series focused astronomy. I conclude my work by suggesting viable routes to further improve the photometric precision of such new instrumentation.

This thesis reports an X-ray single crystallographic study of the solid-state halogen bonded adducts formed between a series of mono- and di-iodo- and bromofluorobenzenes with a variety of primary, secondary and tertiary nitrogen bases. As an extension of previous published work, 1,4-diazobicyclo[2.2.2]octane (DABCO) forms adducts with 4-bromo-tetrafluorobenzotrifluoride, 1,2-dibromotetrafluorobenzene and 1,3-dibromotetrafluoro-benzene to form trimers held by N…Br halogen bonds, while with 4,4'-dibromooctafluorobiphenyl a onedimensional polymer is formed. The shortest N…Br distance was observed in the DABCO.1,3-dibromotetrafluorobenzene adduct of 2.667(15) Å, more than 20% shorter than the sum of the van der Waals radii. Both hexamethylenetetramine and 1,3,5-triazina-7-phosphadamantane form adducts with iodopentafluorobenzene,1,2-diiodotetrafluorobenzene,1,3- diiodotetrafluorobenzene and 1,4-diiodofluorobenzene, although no halogen-bond formation was observed involving the phosphorus atom. The adducts containing iodopentafluorobenzene, 1,2-diiodotetrafluoro-benzene and 1,4- diiodofluorobenzene feature N…Br halogen bonds, while for 1,3-diiodotetrafluorobenzene an additional type II I…I interaction is detected. It is observed that the adduct with the shortest halogen bond displays the largest shift in C-F vibrational frequencies. Combinations of pyrimidine, 4,6-dimethylpyrimidine, 1,3,5-triazine and pyrimidine-5-amine with 1,2-diiodotetrafluorobenzene, 1,3- diiodotetrafluorobenzene 1,4-diiodotetrafluoroenzene, and 1,3,5- triodotrifluorobenzene have been investigated from which it is found consistently that pyrimidine forms the shortest N…I halogen bonds of ca. 2.85 Å, which are nearly 20% shorter than the sum of van der Waals radii of nitrogen and iodine. The final experimental chapter describes the structures of halogen bonded adducts formed between piperazine and a series of iodo- and bromo-fluorobenzenes from which it is concluded that intermolecular N…I and N…Br halogen bonds are formed preferentially over N…H hydrogen bonds. In each chapter a comparison between the X-ray diffraction data and parameters obtained from QTAIM computational studies is made. These studies support the interpretation of the X-ray data, but also identify some additional weak interactions.

With the global population constantly increasing, including the population of elderly people, there is an increasing need for facilitating independent and comfortable living. The degree of at-home monitoring that is necessary to deliver sufficient independence can be provided using automated sensor technology built within smart environments. Sensors can be used to monitor a home by analysing the activities of the environment's inhabitant. It is important, however, to consider the preservation of privacy and so the unobtrusiveness of such a system should be considered as vital a characteristic as its accuracy. This thesis proposes an unobtrusive approach for detecting and recognising Activities of Daily Living (ADLs) performed within a smart environment. The research that is presented involved the use of low-resolution thermal sensors as the only means of data capture. The sensors have been used to develop original datasets for training and testing the various components of the proposed approach. The four primary components of the proposed approach are presented as four complementary chapters in this thesis. Firstly, an unobtrusive approach to recognising full body poses with thermal imagery is presented. Several machine learning algorithms were tested and their performances are compared. The second study introduces the concept of subactivities and how they can be inferred from the thermal data using only the predicted pose and the object estimated to be closest to the inhabitant. Additional sensors are considered in the third study where the effect of deep learning is investigated in order to improve upon the pose recognition performance. Lastly, the various components are combined to present the approach to detecting and recognising ADLs in a manner which exhibits both accuracy and privacy.

This thesis explores the deeply embedded early stages of high-mass star formation through two key observational projects. The first project characterises a sample of 731 high-mass star forming clumps hosting class II methanol masers. Masers detected with the Methanol Multibeam Survey are associated with counterparts in the Herschel Infrared Galactic Plane Survey (Hi-GAL), and the properties of these clumps are determined by fitting to the infrared spectral energy distribution. Compared to the entire population of protostellar YSOs visible with Hi-GAL, the maser sources are found to be generally more massive and more luminous in the infrared, but occupying a restricted luminosity-to-mass range within the bounds covered by the total Galactic population. Principal component analysis is used to explore the intra- and inter-sample trends and identifies a sample of 896 protostellar objects with properties consistent with the maser host sample. An average 70 micron flux density deficiency in the maserless protostellar objects suggests that the matched protostellar sources may recently have evolved beyond the point at which they can sustain a luminous 6.7GHz methanol maser. An apparent minimum 70 micron luminosity required to sustain a methanol maser of a given luminosity is seen. The addition of other observed masers to the analysis provides further evolutionary segregation within the sample and a proposed timeline of maser species is presented, including statistical lifetime estimates. The second project is a study of a single infrared dark cloud in an early stage of evolution with weak signatures of star formation activity, combining data from the Sub-millimeter Array, the Atacama Large Millimeter/sub-millimeter Array and the Atacama Compact Array. From the continuum emission, the clump has a low degree of internal fragmentation with only two cores detected, of masses 32 and 9 solar masses respectively. At least two developed outflows are clearly identified despite the early evolutionary stage, and have entrained comparable mass to more evolved objects of size, despite the dark nature of the object at 70 microns. The momentum and energy contained within the outflows is also calculated from the observations. The inferred accretion derived from outflows give an accretion rate onto the brightest embedded core is equal to 32% of the global infall rate observed towards the clump from single dish data. The momentum flux in the outflows against luminosity suggests that these cores are in the early stages of forming two high-mass stars of 50 and an 8 solar masses, and therefore this clump is likely an OB association precursor. The use of different molecular species as probes of temperature towards cold core regions in the presence of established outflows is also discussed.

Autophagy is a highly conserved biological process in eukaryotic cells with an essential role in cellular homeostasis, where dysfunction in this process is a key factor in a multitude of diseases. To this end, accuracy and reliability in the detection and monitoring of autophagy is critical for medicine and research. Current methods for autophagy detection can be costly, time consuming and labour intensive, which hampers their use outside of research laboratories. Raman spectroscopy is a spectrographic technique which allows visualisation of the chemical environment within a sample in a non-destructive and non-invasive manner. The use of Raman spectroscopy has never been fully realised for the detection of autophagy and can offer key benefits to the process. By using Raman spectroscopy to assess the chemical changes in cells undergoing autophagy key changes can be mapped out and used to create a predictive model via the use of machine learning. Raman collection was optimised via the use of drying cells onto a gold coated mirror, to facilitate high Raman scattering intensities with relatively short collection times. The processing of the spectra was optimised with a focus on creating a more generalisable process. Testing different baseline correction algorithms it was found that the asymmetric least squares algorithm performed the best across multiple distinct Raman spectra from different cell lines and different experiments. Raman spectra of cells after 4 hours complete amino acid deprivation show little difference in their Raman spectra, whereas the spectra of cells after 1, 2 and 5 days without l-glutamine show significant changes. These changes are often cell line specific but a commonly seen change is a drop in the 1675 cm-1 shoulder region associated with the protein secondary structure β-pleated sheets. Many of these changes however are also seen in ATG5(-/-) cells suggesting the changes are not autophagy specific. Using an artificial neural network, trained on the first 20 principal components of the Raman spectrum and the cell type, could distinguish between control cells, autophagy induced ATG5(+/+) cells and autophagy induced ATG5(-/-) cells with a 98.2% accuracy. This research lays the groundwork for the use of Raman spectroscopy as a method of detection for autophagy. Larger and more comprehensive data sets would need to be collected to further the applicability of this method.

It has been known for some time that there exists a substantial amount of 'hidden' magnetic energy in the quiet solar photosphere, and unlocking an understanding of this phenomenon requires the study of magnetic activity on the smallest scales accessible to observations. With the advent of next generation high resolution telescopes, our understanding of how the magnetic field is organized in the internetwork (IN) photosphere is likely to advance significantly. Presented are high spatio-temporal resolution observations that reveal the dynamics of two disk-centre IN regions taken by the GREGOR Infrared Spectrograph Integral Field Unit (GRIS-IFU) with the highly magnetically sensitive photospheric Fe I line at 15648.52 ˚A. Inversions are applied with the Stokes inversion based on response functions (SIR) code to retrieve the parameters characterizing the atmosphere, tracking the dynamics of small-scale magnetism. Linear polarization features (LPFs) are found with magnetic flux density 130 − 150 G, appearing preferentially at granule-intergranular lane boundaries. The weak magnetic field appears to be organized in terms of complex 'loop-like' structures, with transverse fields often flanked by opposite polarity longitudinal fields. A snapshot produced from a high resolution three-dimensional radiative magnetohydrodynamic (MHD) simulation is used with SIR to produce synthetic observables in the same spectral window as observed by the GRIS-IFU. A parallelized wrapper to SIR is then used to perform nearly 14 million inversions of the synthetic spectra to test how well the 'true' MHD atmospheric parameters can be constrained statistically. Finally, the synthetic Stokes vector is degraded spectrally and spatially to GREGOR resolutions and the impact of unpolarized stray light contamination, spatial resolution and signal-to-noise is considered. A LPF exhibiting very similar magnetic flux density at its centre as those observed by the GRIS-IFU is studied. Thus, it is demonstrated that MHD simulations are capable of resembling real observations.

In the era of deep and wide-field surveys (e.g. SDSS, LSST, LOFAR, SKA), we have access to an ever-increasing volume of multi-wavelength data for millions of galaxies both locally and at high redshifts. However, inferring the intrinsic properties of the whole population of galaxies requires robust statistical techniques and an understanding of observational bias. In this thesis, I present a study of the Far-Infrared Radio Correlation (FIRC) – a relation which is widely used to infer star-formation rates from otherwise featureless radio sources. Using LOFAR 150MHz, FIRST 1:4GHz, and Herschel infrared luminosities derived from the new LOFAR/H-ATLAS catalogue, we investigate possible variation in the monochromatic (250mm) FIRC at low and high radio frequencies. Although the average FIRC at high radio frequency is consistent with expectations based on a standard power-law radio spectrum, the average correlation at 150MHz is not. We see evidence for redshift evolution of the FIRC at 150MHz, and find that the FIRC varies with stellar mass, dust temperature and specific star formation rate, whether the latter is probed using MAGPHYS fitting, or using mid-infrared colour as a proxy. We can explain the variation, to within σ using a Bayesian partial correlation technique. This work was published as Read et al. (2018) in the Monthly Notices of the Royal Astronomical Society. Identifying an opportunity to increase in the efficiency of black-hole mass estimations, we perform photometric reverberation mapping using the Javelin photometric damped random walk model for the QSO SDSS J144645.44 +625304.0 at ɀ = 0:351 and estimate the Hβ lag of 72 +5-1 days and black hole mass of 108:28 +0.12-0.07 Mʘ. An analysis of the reliability of photometric reverberation mapping conducted using many thousands of simulated light curves shows that we can recover any input lag less than a third of the duration of our observing campaign to within 4per cent on average given our target’s observed signal-to-noise of > 20 and cadence of 14 days. We use our suite of simulated light curves to deconvolve artefacts from the QSO’s posterior lag distribution, increasing the signal-to-noise by a factor of ~3. We exceed the signal-to-noise of the Sloan Digital Sky Survey Reverberation Mapping Project (SDSS-RM) campaign with a quarter of the observing time resulting in a ~310 per cent per cent increase in SNR efficiency over SDSS-RM. Finally, I present a study of the radio luminosity star-formation rate relation directly with the LOFAR Two Metre Sky Survey (LoTSS) DR1, in an effort to understand the mass dependency of the L150MHz - SFR slope reported by Gürkan et al. (2018). Building on our previous study of the FIRC, we develop a fast, generalised algorithm to recover Complete And Noiseless Distributions from Incomplete Data (CANDID). We find that the mass dependency is real and in agreement with previous estimations in the literature when we include the effects of selection biases present in the LoTSS DR1 sample. We also propose that type-Ia supernovae may contribute to a L150MHz excess and construct a joint distribution of our LoTSS observations and the Horizon AGN simulation to test this.

Fourier transform infrared spectroscopy (FTIR) and microscopy (FT-IRMS) are well-established as tools for the study of biological cells. Studies of chemically-fixed cells using infrared (IR) have been able to yield significant information regarding cell morphology, disease development and drug-cell interactions. However, such studies are limited by fixation effects which introduce a range of spectral variations, limiting the interpretation of IR spectra of fixed cells. It is therefore desirable to study living cells in real time, particularly as cells are undergoing response to an external stimulus. This does, however, present a number of challenges. Maintaining live cells requires an aqueous sample environment. Water is, however, a very strong absorber of IR light, producing a spectrum which dwarfs the biochemical signals in the sample and makes the extraction of good-quality spectra with high signal-to-noise (S/N) extremely challenging. The brilliance of synchrotron radiation (SR), combined with development of an in-house water correction procedure performing a least-squares fit with a (Matrigel) reference spectrum, has been able to generate high-quality spectra while retaining a sufficient level of spectral detail to analyse relative subtle biochemical changes. Wildtype and drug-resistant strains of renal cell carcinoma (RCC) have been treated with different chemotherapy agents and formalin-fixed. Analysis of fixed, dried samples using both single-point SR IR microscopy and bench-top focal plane array (FPA) imaging has identified spectral features linked to efflux or similar drug-resistance mechanisms, opening the possibility of being able to identify drug resistance in the early stages of treatment. These results were able to be replicated using fixed cells suspended in phosphate-buffered saline (PBS), providing validation of the water correction algorithm. Two live cell studies were performed in a static aqueous sample holder. K562 acute myeloid leukaemia (AML) cells were treated with two novel chemotherapy agents, and differences were identified in the resulting spectra that could be directly linked to the mode of action of the two compounds. This analysis made use of DNA bands that are only accessible when measuring hydrated cells. The second study used a wildtype and drug-resistant strain of PEO1 ovarian cancer cells, and analysed their response to a novel agent, showing differences in the measured spectra between wildtype and resistance samples. Static-mode live cell studies have been able to provide significant information, but are limited by the survival time of the samples. A customised commercial liquid sample holder has undergone simple and cost-effective modifications to produce a dynamic flow system for live cell measurements, potentially up to and beyond 24 hours. This includes the novel implementation of a hydrophobic barrier to direct and control flow. Trypan Blue staining has confirmed cell viability up to at least 24 hours, and two biological studies have been performed to demonstrate different properties of the system. Measuring samples at different temperatures has proved that the system is capable of inducing and simultaneously measuring cellular changes, while a study of deuterated palmitic acid uptake has shown that a sample can be maintained for long enough to acquire spectra of a large number of cells.

Flowering plants produce floral displays that both attract pollinators and allow them to learn flower identity. How well these displays do this can be critically important to pollinator and plant success, and thus is also important to the evolution of both mutualists. Floral displays are multimodal, they produce many complex floral signals through different sensory modes (such as visual, olfactory and tactile) simultaneously. Why floral displays are multimodal is not fully understood. This is due to the majority of research focusing upon pollinator responses to single signalling modalities, but also due to the majority of research focusing upon scent and visual signals. This has a consequence that we do not yet know the extent of floral multimodality. While scent and visual modalities are obviously of great importance, in order to fully understand the reasons behind the evolution of floral multimodality we must gain a better understanding of other signalling modalities. In this thesis I investigate two floral signalling modalities further, floral temperature and floral humidity. Through investigation of the traits floral displays produce I show that the temperature across floral displays differs, flowers show temperature patterns. Additionally, I show that elevated floral humidity about the flower is not limited to the single specialist species on which it has been recorded previously. Using captive bumblebees and established behavioural techniques I show that bumblebees can respond to and learn floral temperature pattern and floral humidity differences. This shows floral displays to be more multimodal than previously thought, with floral temperature showing a greater level of complexity and floral humidity having potential to be more widely used. In addition to this I investigate further how floral temperature may function within a multimodal display by testing its capacity to perform roles other than floral recognition which have previously been observed in visual patterns.

I study mid-infrared and star formation properties of AGN samples using infrared observations, and star-forming galaxies using radio observations in order to investigate the link between star formation, AGN activity and radio luminosity. I present the results of these investigations in this thesis. I carried out an analysis of four complete samples of radio-loud AGN (3CRR, 2Jy, 6CE and 7CE) using near- and mid-IR data taken by the Wide-Field Infrared Survey Explorer (WISE). The combined sample consists of quasars and radio galaxies, and covers a redshift range 0:003 < z < 3:395. The dichotomy in the mid-IR properties of low- and high-excitation radio galaxies (LERGs - HERGs) is analysed using large complete samples. The results show that a division in the accretion modes of powerful LERGs and HERGs clearly stands out in the mid-IR radio plane. Evaluation of the positions of the sample objects in WISE colour-colour diagrams shows that widely used WISE colour cuts are not completely reliable in selecting AGN. I examined the link between AGN activity and star formation by constructing matched samples of local (0 < z < 0:6) radio-loud and radio-quiet AGN in the Herschel-ATLAS fields. AGN accretion and jet powers in these active galaxies are traced by [OIII] emission-line and radio luminosity, respectively. Star formation properties were derived using Herschel 250-_m and stellar mass measurements are taken from the SDSS-MPA-JHU catalogue. The stacking analyses show that star formation rates (SFRs) and specific star formation rate (SSFRs) of both radio-loud and radio-quiet AGN increase with increasing AGN power but that radio-loud AGN tend to have lower SFR. Additionally, radio-quiet AGN are found to have approximately an order of magnitude higher SSFRs than radio-loud AGN for a given level of AGN power. The difference between the star formation properties of radio-loud and -quiet AGN is also seen in samples matched in stellar mass. I also investigated the relationship between SFR and low-frequency radio luminosity observed in star-forming galaxies. I used a sample of star-forming galaxies in the 19 local Universe selected from the SDSS-MPA-JHU catalogue. LOFAR observations of the Herschel-ATLAS North Galactic Pole field (NGP) were carried out as part of the LOFAR surveys Key Science Project at an effective frequency of 150 MHz, which provided low-frequency radio luminosity of sample galaxies. SFRs of galaxies in the sample were derived using MAGPHYS spectral energy distribution (SED) fitting. The results of this study show that the slope of L150/SFR is less than unity and not universal for all star-forming galaxies (SFGs) in the local Universe (0 < z < 0:3). The slope of the L150/SFR relation is also found to be steeper than the L1:4/SFR relation, probably due to the contribution from thermal radio emission at 1.4 GHz. If the L150=SFR relation for strongly star-forming objects is explained naively by electron calorimetry, I conclude that low luminosity sources are not ideal calorimeters and differ from the main locus of SFGs at low redshifts. The different gradients we obtain for the far- IR/radio correlation using samples selected at different frequencies reveal the selection effects on relations derived in this thesis.

The work described in this thesis focuses on the effects that adsorption processes on catalytic surfaces pose in controlling key steps that can affect and control reaction pathways. To that, the development of Nuclear Magnetic Resonance (NMR) relaxometry methods and the comparison with traditional catalytic was performed with a series of C5 and C6 unsaturated hydrocarbons on two different alumina supports, γ- and θ-Al2O3. The developed techniques were applied in the study of liquid phase selective hydrogenation of citral on 5% Pt/SiO2. Infrared (IR) spectroscopy, volumetric adsorption isotherms, dynamic isotherms via a Tapered Element Oscillating Microbalance (TEOM), temperature programmed desorption (TPD) as well as 13C T1 NMR and 1H 2D T1-T2 relaxometry methods were employed. Energies of adsorption as a function of coverage were obtained via adsorption isotherms and the particular surface adsorbate interactions were described with IR spectroscopy. For example, 1-pentyne showed the strongest interaction with the alumina (94 kJ mol-1) while 1-pentene presented a weaker interaction (46 kJ mol-1) on θ-Al2O3. Desorption energies obtained from TPD ranged 85 – 130 kJ mol-1, irrespective of the adsorbate. Reactivity of the aluminas was captured with TPD, TEOM and NMR relaxometry. Interaction of adsorbates with hydrocarbon occurred predominantly on weak adsorption sites. 13C NMR T1 relaxometry provided in addition atom-specific adsorbate-adsorbent interaction strengths, showing the molecular geometry of adsorption, and applied in co adsorption measurements. The selective hydrogenation of citral as a model α,β-unsaturated aldehyde and the effect of different solvents on the activity and product distribution was studied at 298 and 373 K. A series of polar protic, polar aprotic and non polar solvents was investigated. Results showed higher initial reaction rates in non polar solvents but higher selectivities towards desired products on polar protic solvents. Solvent used also affected by product formation. The strong variations in reaction rates and selectivities reported were related with adsorbate catalyst interactions, as well as solvent reactant interactions. For example, adsorption isotherms showed that ethanol notably reduced the adsorption capacity of citral as compared with hexane, related with the rate differences observed. ATR-IR measurements indicated solvent citral interactions were solely present in polar protic solvents in line with higher yields of geraniol and nerol. Finally, 13C T1 NMR and 1H 2D T1-T2 correlation experiments determined that the geometry of adsorption of citral, influenced by solvent, affected product selectivity, and that product adsorption affected selectivity and deactivation.

This thesis investigates the cooling behaviour of polymers during the microinjection moulding process. The work included bespoke experimental mould design and manufacturing, material characterisation, infra-red temperature measurements, cooling analysis and cooling prediction using commercial simulation software. To measure surface temperature of the polymers, compounding of polypropylene and polystyrene with carbon black masterbatch was performed to make materials opaque for the IR camera. The effects of addition of carbon black masterbatch were analysed using differential scanning calorimetry and Fourier transform infrared spectroscopy. Sapphire windows formed part of the mould wall and allowed thermal measurements using an IR camera. They were laser machined on their inside surfaces to generate a range of finishes and structures. Their topographies were analysed using laser confocal microscope. The surface energy of sapphire windows was measured and compared to typical mould steel, employing a contact angle measurement technique and calculated using Owens-Wendt theory. A heating chamber was designed and manufactured to study spreading of polymer melts on sapphire and steel substrates. A design of experiments approach was taken to investigate the influence of surface finish and the main processing parameters on polymer cooling during microinjection moulding. Cooling curves were obtained over an area of 1.92 by 1.92 mm of the sapphire window. These experiments were conducted on the Battenfeld Microsystem 50 microinjection moulding machine. A simulation study of polymer cooling during the microinjection moulding process was performed using Moldflow software. Particular interest was paid to the effect of the values of the interfacial heat transfer coefficient (HTC) on the simulated cooling predictions. Predicted temperature curves were compared to experimentally obtained temperature distributions, to obtain HTC values valid for the material and processing parameters.

The notion that low- to intermediate-mass young stellar objects (YSOs) gain mass at a constant rate during the early stages of their evolution appears to be challenged by observations of YSOs suffering sudden increases of the rate at which they gain mass from their circumstellar discs. Also, this idea that stars spend most of their lifetime with a low accretion rate and gain most of their final mass during short-lived episodes of high accretion bursts, helps to solve some long-standing problems in stellar evolution. The original classification of eruptive variables divides them in two separate subclasses known as FU Orionis stars (FUors) and EX Lupi stars (EXors). In this classical view FUors are at an early evolutionary stage and are still gaining mass from their parent envelopes, whilst EXors are thought to be older objects only surrounded by an accretion disc. The problem with this classical view is that it excludes younger protostars which have higher accretion rates but are too deeply embedded in circumstellar matter to be observed at optical wavelengths. Optically invisible protostars have been observed to display large variability in the near-infrared. These and some recent discoveries of new eruptive variables, show characteristics that can be attributed to both of the optically-defined subclasses of eruptive variables. The new objects have been proposed to be part of a new class of eruptive variables. However, a more accepted scenario is that in fact the original classes only represent two extremes of the same phenomena. In this sense eruptive variability could be explained as arising from one physical mechanism, i.e. unsteady accretion, where a variation in the parameters of such mechanism can cause the different characteristics observed in the members of this class. With the aim of studying the incidence of episodic accretion among young stellar objects, and to characterize the nature of these eruptive variables we searched for high amplitude variability in two multi-epoch infrared surveys: the UKIDSS Galactic Plane Survey (GPS) and the Vista Variables in the Via Lactea (VVV). In order to further investigate the nature of the selected variable stars, we use photometric information arising from public surveys at near- to farinfrared wavelengths. In addition we have performed spectroscopic and photometric follow-up for a large subset of the samples arising from GPS and VVV. We analyse the widely separated two-epoch K-band photometry in the 5th, 7th and 8th data releases of the UKIDSS Galactic Plane Survey. We find 71 stars with _K > 1 mag, including 2 previously known OH/IR stars and a Nova. Even though the mid-plane is mostly excluded from the dataset, we find the majority (66%) of our sample to be within known star forming regions (SFRs), with two large concentrations in the Serpens OB2 association (11 stars) and the Cygnus-X complex (27 stars). The analysis of the multi-epoch K-band photometry of 2010-2012 data from VVV covering the Galactic disc at |b| < 1◦ yields 816 high amplitude variables, which include known variables of different classes such as high mass X-ray binaries, Novae and eclipsing binaries among others. Remarkably, 65% of the sample are found concentrated towards areas of star formation, similar to the results from GPS. In both surveys, sources in SFRs show spectral energy distributions (SEDs) that support classification as YSOs. This indicates that YSOs dominate the Galactic population of high amplitude infrared variable stars at low luminosities and therefore likely dominate the total high amplitude population. Spectroscopic follow-up allows us to confirm the pre-main sequence nature of several GPS and VVV Objects. Most objects in both samples show spectroscopic signatures that can be attributed to YSOs undergoing high states of accretion, such as veiling of photospheric features and CO emission, or show FUor-like spectra. We also find a large fraction of objects with 2.12 μm H2 emission that can be explained as arising from shock-excited emission caused by molecular outflows. Whether these molecular outflows are related to outbursts events cannot be confirmed from our data. Adding the GPS and VVV spectroscopic results, we find that between 6 and 14 objects are new additions to the FUor class from their close resemblance to the near-infrared spectra of FUors, and at least 23 more objects are new additions to the eruptive variable class. For most of these we are unable to classify them into any of the original definitions for this variable class. In any case, we are adding up to 37 new stars to the eruptive variable class which would double the current number of known objects. We note that most objects are found to be deeply embedded optically invisible stars, thus increasing the number of objects belonging to this subclass by a much larger factor. In general, objects in our samples which are found to be likely eruptive variable stars show a mixture of characteristics that can be attributed to both of the optically-defined classes. This agrees well with the recent discoveries in the literature. Finally, we are able to derive a first rough estimate on the incidence of episodic accretion among class I YSOs in the star-forming complex G305. We find that _ 9% of such objects are in a state of high accretion. This number is in agreement with previous theoretical and observational estimates among class I YSOs.

My Ph.D. has been composed of work involving the use of far–IR and submm observations of AGN. During this time it has focused on the in- terplay between AGN and their host galaxies and cluster environments. Understanding the role of AGN, and how they affect the evolution of both their host galaxies and surrounding environments, is a pressing concern in cosmological models of the universe, affecting as they do the chemical makeup, star formation rate, and morphology of their host galaxies. In Chapter 2, we focus on attempting to determine whether there is an inherent physical difference between Broad Absorption Line Quasars and non–BAL QSOs using Herschel observations taken at 250, 350 and 500 μm as part of the H–ATLAS (Eales et al. 2010) survey. BAL QSOs have been considered the most visible form of AGN feedback, and therefore are a prime starting point for understanding how galaxy evolution may be affected by the presence of an AGN. By using matched samples of 50 BAL and 329 non–BAL QSOs, we create weighted stacks at each wavelength, finding similar far–IR flux–densities for each sample within the errors. By SED modelling using a simple modified black body (Hildebrand 1983) fit to Mrk 231 and IZw1, we derive likely upper and lower limits for the BAL and non–BAL QSOs in each wavelength, again finding they are consistent within the errors. A bevy of statistical tests run on either population similarly finds no evidence to reject the null hypothesis they are drawn from the same parent population. These results would imply that HiBAL QSOs can be unified with ordinary QSOs within a simple orientation dependent scheme. We cannot make the same distinction for LoBALs or FeLoBALs, which the literature suggests may well be a separate evolutionary phase. In Chapter 3, we determine whether the presence of an AGN correlates to an overdensity of star–forming galaxies in the FIR, as has been found at shorter wavelengths (Falder et al. 2010). For the SHAGs study, 171 AGN were observed and selected at z∼1. By using observations at 250 μm, we are able to trace close to the peak of the grey–body SED created by reprocessing by dust of radiation from young O and B stars. Following data reduction, we determine number counts and correct for completeness within a 1Mpc radius of the central AGN. We find an overdensity on the order of around 0.4 sources per AGN, implying a degree of activity already significantly lower than at higher redshifts. This overdensity appears to be somewhat different between RL AGN and RQQ within 1Mpc. A cor- relation is found between radio luminosity and star formation overdensity, consistent with a stronger dependence found by Falder et al. (2010) at 3.6 μm, and there also appears to be a correlation between stellar mass and star formation overdensity for radio–loud QSOs. The galaxies in the environs of the AGN have LIRG–level luminosities, and are likely the pro- genitors of modern day S0 galaxies, whose population increases steadily from z∼1 to the present day (Postman et al. 2005; Smith et al. 2005). Our work with SCUBA–2, presented in Chapter 4, follows on from a prior sample of X–ray–absorbed QSOs (Stevens et al. 2005). This new sample is composed of more highly–absorbed X–ray QSOs and covers a larger area than the initial sample, so is ideal for an analysis of source counts around AGN at high–redshift. Data from the JCMT have been reduced, and completeness corrections and flux corrections applied to catalogues to determine the number counts around AGN. A comparison background, created using data from the Cosmology Legacy Survey has been used to derive comparison counts. The AGN have been investigated, yet none are detected above 3 at 850 μm, in contrast to the original sample. This may suggest that star formation in their host galaxies has been suppressed. Upon stacking in redshift and BAL classification, no difference in flux– density is apparent and the sources studied here have a similar stacked submm output to an unabsorbed QSO sample created for the original X– ray absorbed QSOs. However, over half of the sources here are BAL QSOs in contrast to the original absorbed QSO sample which contained only 1 BAL QSO. From the work in Chapter 2, one might expect BAL and non–BAL QSOs to have similar flux–densities. We argue that the sources studied in this thesis have likely undergone rapid evolution owing to a strong outflow, and as such star formation has been suppressed sufficiently that the submm emission is below the confusion noise. BAL winds may still be present, but essentially, the show is already over. A similar mechanism may already have occurred in unabsorbed QSOs if all QSOs pass through an X–ray–absorbed phase. With regard to source counts, we find that there is tentative evidence for an overdensity of sources around these AGN. The SFRs of the companion sources have been calculated using several greybody analogues, all of which imply a high degree of activity, suggesting these fields will evolve to become some of the most massive regions at the present epoch, in keeping with current theories of SMGs and high–redshift clusters.

Observations of galaxy environments have revealed numerous correlations associated with their intrinsic properties. It is therefore clear that if we are to understand the processes by which galaxies form and evolve, we have to consider the role of their immediate environment and how these trends change across cosmic time. In this thesis, I investigate the relationship between the environmental densities of galaxies and their associated properties by developing and implementing a novel approach to measuring galaxy environments on individual galaxy scales with Voronoi tessellations. Using optical spectroscopy and photometry from GAMA and SDSS, with 250μm far-infrared observations from the Herschel-ATLAS SDP and Phase-One fields, the environmental and star formation properties of far-infrared detected and non–far-infrared detected galaxies are compared out to z ∼ 0.5. Applying statistical analyses to colour, magnitude and redshift-matched samples, I show there to be significant differences between the normalised density distributions of the optical and far-infrared selected samples, at the 3.5σ level for the SDP increasing to > 5σ when combined with the Phase-One data. This is such that infrared emission (a tracer of star formation activity) favours underdense regions, in agreement with previous studies that have proposed such a correlation. I then apply my method to synthetic light cones generated from semianalytic models (SAMs), finding that over the whole redshift distribution the same correlations between star-formation rate and environmental density are found. However, as the SAMs restrict the role of ram-pressure stripping, the fact that we find the same qualitative results may preclude ram-pressure as a key mechanism in truncating star formation. I also find significant correlations between isothermal dust temperature and environment, such that the coldest sources reside in the densest regions at the 3.9σ level, indicating that the observed far-infrared emission in these densest regions is the product of ISM heating by the older stellar populations. I then extend my analysis to a deeper sample of galaxies out to z ∼ 2.2, combining near-infrared and optical photometry from the VIDEO and CFHTLS-D1 observations, cross-matched in colour, magnitude and redshift against 1.4 GHz VLA radio observations. Across the entire radio sample, galaxies with radio detected emission are found to reside in more overdense environments at a 4.0σ significance level. I then divide my radio sample to investigate environmental dependence on both radio detected star-forming galaxies and radio detected AGN individually, based upon a luminosity selection defined as L = 1023 W Hz−1. The same trends with environment are shown by my Radio-AGN sample (L > 1023 W Hz−1) which favour overdense regions at the 4.5σ level, suggestive of the interaction processes (i.e. major mergers) that are believed to trigger accretion, in agreement with earlier work that has suggested such a relationship. At lower radio luminosities, my Radio-SF sample (L < 1023 W Hz−1) also display a significant trend towards overdense regions in comparison to my nonradio detected sample, at the less significant level of 2.7σ. This is suggestive of the low overall bolometric luminosity of radio emission in star forming galaxies, leading to only the brightest radio emitting star forming galaxies being observed and a bias towards overdense regions. This is in addition to the fact that the luminosity selection used to separate AGN from star forming galaxies is not a perfect selection and open to AGN contamination in the low-luminosity sample. I conclude that the next generation of deep radio surveys, which are expected to reach many orders of magnitude deeper than current observations, will remove radio-loud AGN contamination and allow for the detection of low-luminosity star forming galaxies via radio emission out to high redshifts. This work has allowed for the environments of galaxies to be probed on smallerscales and across both wider and deeper samples than previous studies. With significant environmental correlations being returned, this indicates that the established processes responsible for such trends must have influence on the most local of scales.

Stars on the asymptotic giant branch (AGB) lose a significant fraction of their mass to their surroundings through stellar winds. As a result, they are surrounded by circumstellar shells of gas and dust. This stellar mass loss replenishes and enriches the interstellar medium (ISM) with the products of stellar nucleosynthesis, progressively increasing its metallicity and thereby driving galactic chemical evolution. In this thesis I present a comprehensive study of oxygen-rich (O-rich) AGB stars and red supergiants (RSG) observed with the Spitzer Infrared Spectrograph and Infrared Space Observatory Short Wavelength Spectrometer in the Milky Way, the Large and Small Magellanic Clouds, and Galactic globular clusters; focusing on the composition of the dust in the circumstellar envelopes surrounding these stars. Combining spectroscopic and photometric observations with the GRAMS grid of radiative transfer models to derive (dust) mass-loss rates, I detect crystalline silicates in stars with dust mass-loss rates which span over a factor of 1000, down to rates of ~10^{-9} Msun/yr. Detections of crystalline silicates are more prevalent in higher mass-loss rate objects, and our results indicate that the dust mass-loss rate has a greater influence on the crystalline fraction than the gas mass-loss rate, suggesting that thermal annealing of amorphous silicate grains is the primary formation mechanism of crystalline silicates in such environments rather than the direct condensation of crystalline silicates from the gas phase. I also find that metallicity influences the composition of crystalline silicates, with enstatite seen increasingly at low metallicity, while forsterite becomes depleted at these metallicities due to the different chemical composition of the gas. To trace the evolution of alumina and silicate dust along the AGB, I present an alternative grid of MODUST radiative transfer-models for a range of dust compositions, mass-loss rates, dust shell inner radii and stellar parameters. Our analysis shows that the AKARI [11]-[15] versus [3.2]-[7] colour is a robust indicator of the fractional abundance of alumina in O-rich AGB stars. From the modelling, I show that a grain mixture consisting primarily of amorphous silicates, with contributions from amorphous alumina and metallic iron provides a good fit to the observed spectra of O-rich AGB stars in the LMC. In agreement with previous studies, we find a correlation between the dust composition and mass-loss rate; the lower the mass-loss rate the higher the percentage of alumina in the shell. Finally, I present mid-infrared observations of the Local Group dwarf elliptical galaxy M32; where I find a large population of dust-enshrouded stars. These observations will act as a pathfinder for future observations with the JWST and SPICA.

Within this thesis, we present an extended multiwavelength analysis of the rich massive Galactic star-forming complex G305. We have focused our attention on studying the both the embedded massive star-forming population within G305, while also identifying the intermediate-, to lowmass content of the region also. Though massive stars play an important role in the shaping and evolution of their host galaxies, the physics of their formation still remains unclear. We have therefore set out to studying the nature of star formation within this complex, and also identify the impact that such a population has on the evolution of G305. We firstly present a Herschel far-infrared study towards G305, utilising PACS 70, 160 μm and SPIRE 250, 350, and 500 μm observations from the Hi-GAL survey of the Galactic plane. The focus of this study is to identify the embedded massive star-forming population within G305, by combining far-infrared data with radio continuum, H2O maser, methanolmaser,MIPS, and Red MSX Source survey data available from previous studies. From this sample we identify some 16 candidate associations are identified as embedded massive star-forming regions, and derive a two-selection colour criterion from this sample of log(F70/F500)! 1 and log(F160/F350)! 1.6 to identify an additional 31 embedded massive star candidates with no associated starformation tracers. Using this result, we are able to derive a star formation rate (SFR) of 0.01 - 0.02 M! yr−1. Comparing this resolved star formation rate, to extragalactic star formation rate tracers (based on the Kennicutt-Schmidt relation), we find the star formation activity is underestimated by a factor of !2 in comparison to the SFR derived from the YSO population. By next combining data available from 2MASS and VVV, Spitzer GLIMPSE and MIPSGAL, MSX, and Herschel Hi-GAL, we are able to identify the low-, to intermediate-mass YSOs present within the complex. Employing a series of stringent colour selection criteria and fitting reddened stellar atmosphere models, we are able remove a significant amount of contaminating sources from our sample, leaving us with a highly reliable sample of some 599 candidate YSOs. From this sample, we derive a present-day SFR of 0.005±0.001M! yr−1, and find the YSOmass function (YMF) of G305 to be significantly steeper than the standard Salpeter-Kroupa IMF. We find evidence of mass segregation towards G305, with a significant variation of the YMF both with the active star-forming region, and the outer region. The spatial distribution, and age gradient, of our 601 candidate YSOs also seem to rule out the scenario of propagating star formation within G305, with a more likely scenario of punctuated star formation over the lifetime of the complex.

This Thesis contains two parts. Part I details my work on KMOS, a new instrument for the VLT and Part II details my research on scaling relations for the massive galaxy cluster MS0451.6-0305. Part I: The K-Band Multi-Object Spectrograph (KMOS) is a new near infra-red (NIR) instru- ment to be installed at the Very Large Telescope (VLT). KMOS is capable of spatially resolved kinematics via 24 deployable integral field units (IFUs), each with a 2.8′′ field of view. I describe my contribution to the construction and optical characterisation of the spectrograph modules and instrument as a whole. Part II: GMOS-N spectroscopy has been used to obtain velocity dispersions (σ) and archival HST photometry has been used to determine the effective radii (Re) & average surface brightnesses within Re (⟨I⟩e) of 26 confirmed cluster members of MS0451.6-0305 at z = 0.55. The Kormendy Relation, Faber-Jackson Relation and Fundamental Plane have been produced for the cluster and have been compared to the results for a local reference sample in Coma. GMOS-N g′ and r′ band photometry has also been used to produce a Colour-Magnitude Relation for MS0451.6-0305. It is found that the KR and FJR disagree at the 2.1σ level with respect to luminosity evolution since z = 0.55. When correcting for size-evolution (SE), the magnitude offsets agree and are consistent with passive evolution of the galaxy stellar populations from a single burst of star formation 9.8+4.5-1.7 Gyrs ago or z = 1.7+∞-0.6. The median offset in the FP relation for the SE corrected data is also consistent with this formation epoch. Evidence is found for the evolution of the FP tilt in MS0451.6-0305, where it is shown to be steeper than that of the Coma FP, when expressed as a relation between galaxy mass and M/L.

The coupling efficiency of carbon nanotubes with near infrared laser radiation at 940nm wavelength was investigated. Nanotubes treated with different post processing methods were irradiated at different laser power intensities as dry samples and suspensions in water or ethanol. The interaction with the laser beam was measured and quantified based on the temperature increase in the samples as well as the amount of energy transmitted through them. Parallel experiments using carbon black revealed better performance of carbon nanotubes in terms of coupling efficiency and heat dissipation to their surroundings. It was found that most of the incident radiation on an individual carbon nanotube is absorbed, resulting in extreme local temperature increases proportional to the laser intensity, which can lead to instant tube oxidation in air. Such high heats are efficiently transferred to the material in immediate contact with the nanotubes, increasing its temperature very rapidly. The most intriguing results were obtained in the presence of water where the observations suggested, disintegration of carbon nanotubes with each laser pulse. It is shown that extremely high local temperatures vaporise the water in the immediate vicinity of a carbon nanotube and result in a water-gas reaction. It is further postulated that such effects can be achieved with laser beams at power intensities near the skin tissue's safe exposure thresholds, and therefore can potentially be used as a method of removing nanotubes from living tissue. This has advantages in providing an exit route for nanotubes whether introduced on purpose for reasons of medicine or therapy, or possibly, as a result of inadvertent exposure. Further studies on laser heating and transmission through different dry samples, highlighted that more crystalline structures such as that of a heat-treated nanotube, are more effective in causing extinction of the laser beam and a reduction in the transmitted beam intensity, however the tubes with more defects or with a length comparable to the radiation wavelength are very effective in converting the absorbed laser energy to heat. This effect is exacerbated when the laser beam is polarised parallel to the long axis of the carbon nanotubes. These heating effects were exploited to create welds in high density polyethylene using through transmission laser welding. The resultant welds showed better than or equal mechanical performance to welds made using industrial absorbers such as carbon black or Clearweld®.

Feynman graphs in perturbative quantum field theory are replete with infrared divergences caused by the presence of massless particles, how-ever these divergences are known to cancel order-by-order when all virtual and real contributions to a given cross section are summed and smeared against an experimental resolution. In this thesis we treat the infrared problem formally in the language of distribution theory so that we can remove the divergences with local momentum space subtractions using Hadamard's procedure. This is analogous with the BPHZ mechanism for removing UV divergences. Our aim is to show how it is possible to make both the real and virtual subtractions analytically such that we are left with manifestly finite integrands. For the virtual graphs we present a new decomposition of the integrand in momentum space and remove those terms that are divergent. For the real graphs we show how the Taylor expansion of the momentum conserving delta function allows the explicit removal of the divergent part; furthermore we show that the homogeneous properties of the soft structure greatly simplifies this procedure.

Theories of how galaxies form and evolve depend greatly on constraints provided by observations. However, when those observations come from different datasets, systematic offsets may occur. This causes difficulties measuring variations in parameters between filters. In this thesis I present the variation in total luminosity density with wavelength in the nearby Universe (z<0.1), produced from a consistent reanalysis of NIR and optical observations, taken from the MGC, UKIDSS and SDSS surveys. I derive luminosity distributions, best-fitting Schechter function parameterisations and total luminosity densities in ugrizYJHK, and compare the variation in luminosity density with cosmic star formation history (CSFH) and initial mass function (IMF) models. I examine the r band luminosity distribution produced using different aperture definitions, the joint luminosity- surface brightness (bivariate brightness) distribution in ugrizYJHK, comparing them to previously derived distributions, and how the total luminosity density varies with wavelength when surface brightness incompleteness is accounted for. I find the following results. (1) The total luminosity density calculated using a non-Sersic (e.g. Kron or Petrosian) aperture is underestimated by at least 15%, (2) Changing the detection threshold has a minor effect on the best-fitting Schecter parameters, but the choice of Kron or Petrosian apertures causes an offset between datasets, regardless of the filter used to define the source list, (3) The decision to use circular or elliptical apertures causes an offset in M* of 0.20 mag, and best-fitting Schechter parameters from total magnitude photometric systems have a flatter faint-end slope than Kron or Petrosian photometry, (4) There is no surface brightness distribution evolution with luminosity for luminous galaxies, but at fainter magnitudes the distribution broadens and the peak surface brightness dims. A Choloniewski function that is modified to account for this surface brightness evolution fits the bivariate-brightness distribution better than an unmodified Choloniewski function, (5) The energy density per unit interval, vf(v) derived using MGC and GAMA samples agrees within 90% confidence intervals, but does not agree with predictions using standard CSFH and IMF models. Possible improvements to the data and alterations to the theory are suggested.

The current generation of Glass Ionomer Cements (GICs) have many advantageous properties over other dental restorative materials but lack the compressive strength of these other materials. The aim of this project is to increase the compressive strength of conventional Glass Poly-Vinyl-Phosphonate cement by inclusion of reactive sub-micron filler particles. The setting characteristics, chemical reactivity and cement strength have been found using oscillating rheology, infrared spectrometry, nuclear magnetic spectrometry, transmission electron microscopy, potentiometer analysis, laser diffractometry and mechanical analysis. The addition of sub-micron filler particles in direct weight by weight replacement of aluminosilicate glass of a control material has increased the ultimate compressive strength of the new cement from 206MPa (control) to 250MPa after 365 days of aging. The strength of the new filler enhanced cements were comparable with the control material after 3 hours. The setting chemistry of the filler enhanced cements follows the same order as the control cement but at a decelerated rate. Theoretical modelling found that a large volume of sub-micron filler could fit into interstitial spacing in formed cement however the alteration of the aluminosilicate glass to polyelectrolyte ratio has been found to drastically alter the cement setting time. The use of cubic and polyhedral shaped filler particles as supposed to spherical particles may increase the cement strength further as greater packing densities are achieved. The formulation of a Glass Ionomer Cement with increased compressive strength may find use as a posterior restorative or as a better material for restoration of lesions and cavity liners.

The Diviner Lunar Radiometer is a nine-channel radiometer on board the Lunar Reconnaissance Orbiter, launched in June 2009 and currently orbiting the Moon. Diviner is the first orbiting multi-spectral instrument to observe the lunar surface in the mid- and far- infrared, therefore this thesis details the first steps towards utilising observations in this new spectral region. The author, as part of the Diviner instrument team, contributed to the pre-launch testing and calibration of Diviner. Specifically, the transmission profiles of the B2 and B3 filters, which could not be measured after integration into the instrument due to their long wavelength passbands, were determined. Further investigations of the far-infrared mesh filters were also conducted, as the spectral responses of similar mesh filters were found to have broadened after integration into the Mars Climate Sounder instrument, the pre-cursor instrument to Diviner. To test if this would occur in Diviner also, a new setup was made to approximately re-create the instruments' optical layout. No such spectral broadening was measured in the B1, B2 or B3 filters. The linearities of Diviner's detectors were also confirmed through analysis of the pre-flight calibration data. Laboratory emission spectra taken under ambient conditions differ from those taken in a lunar environment, which induces a temperature gradient in soil and mineral samples. Due to a lack of spectra measured under such conditions, which are directly comparable to Diviner‟s measurements, a new chamber for performing high-resolution emission measurements in a simulated lunar environment was built and calibrated. This setup induces a temperature gradient in each sample by heating it from below while it is surrounded by a cooled radiation shield, all enclosed in a very low pressure vacuum chamber. Lunar analogue minerals have been measured, first in reflectance, and then in simulated lunar conditions, forming the basis of a new lunar spectral library. The uses of the mid- and far-infrared have been described herein, utilising calibrated Diviner observations to: [1] map the temperatures of the lunar poles; [2] investigate regions containing higher than average abundances of rocks; and [3] determine the composition of regions of the lunar surface by combining observations with the new spectral library made during this project.

Lasers find a wide range of applications in many areas including photo-biology, photo-chemistry, materials processing, imaging and telecommunications. However, the practical use of such sources is often limited by the bulky nature of existing systems. By fabricating channel waveguides in solid-state laser-gain materials more compact laser systems can be designed and fabricated, providing user-friendly sources. Other advantages inherent in the use of waveguide gain media include the maintenance of high intensities over extended interaction lengths, reducing laser thresholds. This thesis presents the development of Yb:tungstate lasers operating around 1μm in waveguide geometries. An Yb:KY(WO₄)₂ planar waveguide laser grown by liquid phase epitaxy is demonstrated with output powers up to 190 mW and 76 % slope efficiency. This is similar to the performance from bulk lasers but in a very compact design. Excellent thresholds of only 40 mW absorbed pump power are realised. The propagation loss is found to be less than 0.1 dBcm⁻¹ and Q-switched operation is also demonstrated. Channel waveguides are fabricated in Yb:KGd(WO₄)₂ and Yb:KY(WO₄)₂ using ultrafast laser inscription. Several of these waveguides lase in compact monolithic cavities. A maximum output power of 18.6 mW is observed, with a propagation loss of ~2 dBcm⁻¹. By using a variety of writing conditions the optimum writing pulse energy is identified. Micro-spectroscopy experiments are performed to enable a fuller understanding of the induced crystal modification. Observations include frequency shifts of Raman lines which are attributed to densification of WO₂W bonds in the crystal. Yb:tungstate lasers can generate ultrashort pulses and some preliminary work is done to investigate the use of quantum dot devices as saturable absorbers. These are shown to have reduced saturation fluence compared to quantum well devices, making them particularly suitable for future integration with Yb:tungstate waveguides for the creation of ultrafast, compact and high repetition rate lasers.

This thesis reports on the development of glass-based femtosecond laser sources around 2 µm wavelength. In order to be able to produce 2 µm radiation the dopants used were trivalent Thulium (Tm³⁺) and trivalent Holmium (Ho³⁺) that could be optically pumped with Ti:Sapphire radiation at 0.8 µm and semiconductor disk lasers (SDL) at 1.2 µm. The samples were produced at Leeds University and polished in-house in bulk form and deployed in free space laser cavities. Tellurite compounds doped with Tm³⁺ produced stable continuous wave 1.94 µm radiation when pumped at 800 nm with a maximum efficiency of 28.4% with respect to the absorbed power and maximum output power around 120 mW when pumped using a Ti:Sapphire operating around 0.8 µm. The radiation was broadly tunable across 130 nm. Tm³⁺-Ho³⁺ doubly doped tellurite samples lased around 2.02 µm with maximum efficiency of 25.9% and with P[subscript(OUT)]=75 mW and a smooth tunability of 125 nm. The fluorogermanate glass doped with Tm³⁺ gave an absorbed to output power efficiency of 50%. The maximum continuous wave output powers obtained were around 190 mW and limited by the available pump power at 0.8 µm. These results together with a very low threshold of 60 mW of incident power were comparable to the crystalline counterparts to this gain medium. The Tm3+ tellurite and the Tm³⁺-Ho³⁺ tellurite compounds were also pumped by an SDL operating at 1215 nm to obtain an indication of the viability of such a pump scheme. The results were a maximum internal slope efficiency of 22.4% with a highest output power of 60 mW. The comparison demonstrated that 1.2 µm pumping was competitive with using 0.8 µm wavelength. The use of semiconductor saturable absorbing mirror (SESAM) technology was used for the modelocking of these lasers. The SESAM was produced in Canada and implanted with As⁺ ions in order to reduce the relaxation time. Trains of transform-limited laser pulses at 222 MHz as short as 410 fs centred at 1.99 µm were produced for the first time with a bulk Tm³⁺:Fluorogermanate glass. The maximum average output power obtained was of 84 mW. The same SESAM deployed on the Tm³⁺-Ho³⁺ Tellurite compounds gave trains of transform-limited pulses as short as 630 fs at 2.01 µm with a repetition rate of 143 MHz and a maximum averaged output power of 43 mW. The regime of propagation obtained was soliton-like and the modelocking was self-starting. The results obtained with bulk glass were very promising and open interesting research pathways within the realm of amorphous bulk gain media.

Birds are a key environmental asset and this is recognised through comprehensive legislation and policy ensuring their protection and conservation. Many species are active at night and surveys are required to understand the implications of proposed developments such as towers and reduce possible conflicts with these structures. Night vision devices are commonly used in nocturnal surveys, either to scope an area for bird numbers and activity, or in remotely sensing an area to determine potential risk. This thesis explores some practical and theoretical approaches that can improve the accuracy, confidence and efficiency of nocturnal bird surveillance. As image intensifiers and thermal imagers have operational differences, each device has associated strengths and limitations. Empirical work established that image intensifiers are best used for species identification of birds against the ground or vegetation. Thermal imagers perform best in detection tasks and monitoring bird airspace usage. The typically used approach of viewing bird survey video from remote sensing in its entirety is a slow, inaccurate and inefficient approach. Accuracy can be significantly improved by viewing the survey video at half the playback speed. Motion detection efficiency and accuracy can be greatly improved through the use of adaptive background subtraction and cumulative image differencing. An experienced ornithologist uses bird flight style and wing oscillations to identify bird species. Changes in wing oscillations can be represented in a single inter-frame similarity matrix through area-based differencing. Bird species classification can then be automated using singular value decomposition to reduce the matrices to one-dimensional vectors for training a feed-forward neural network.

This DPhil dissertation presents two new and independent samples of faint radio sources. The first sample is the 37 SXDS radio sources with flux densities at 1.4-GHz above 2 mJy, a spectroscopic completeness of 65% and a median redshift z_med ≈ 1.1. The second sample is the 47 TOOT00 radio sources with flux densities at 151 MHz above 100 mJy, a spectroscopic completeness of 85% and z_med ∼ 1.25. Optical, near- and mid-IR photometry, optical spectroscopy, and radio observations are used in the analysis and comparison of the two samples. The quasar fraction in the TOOT00 radio sources is 0.13 < f_q < 0.25 above the FRI/FRII break in radio luminosity, while use of 24 μm data reveals objects with significant but sometimes obscured accretion and gives quasar-mode fraction of 0.5 → 0.9 above the FRI/FRII break. The FRI/FRII divide seen at z < ∼ 0.5 is also observed at z ∼ 1 for FRII objects in the TOOT00 and SXDS samples, but examples of FRI radio sources above the FRI/FRII break do exist. The total number of the TOOT00 objects and their distribution are consistent with simulations based on extrapolations from previous work, while for the SXDS objects the results are only broadly similar. Based on that comparison, the redshift spikes seen at z ∼ 1.3 in TOOT00 and at z ∼ 0.65 & 2.7 in SXDS appear to be significant, and might be due to Large-Scale Structure. A V/Vmax test suggests the cosmic evolution of the TOOT00 and SXDS samples, is different. The TOOT00 radio sources are 2-times more luminous in host-galaxy starlight than the SXDS radio sources. The almost proportionality between radio luminosity at 1.4 GHz and 24 μm luminosity suggests that L_rad traces accretion luminosity and L[OII] ∝ L_rad^0.7 may reflect imperfections in the L[OII]-accretion luminosity scaling. Mid-IR 24 μm observations in the SXDS sample suggest that 30% of the light from the nucleus is absorbed by the torus and re-emitted in the mid-IR, while ∼ 1% of the light is scattered above and below the torus.

Over 300,000 individuals are injured every year by vehicle related accidents in the United Kingdom alone. Government and the vehicle manufacturers are not only bringing new legislation but are also investing in vehicle safety research to bring this figure down. A private self-driven car is an important factor in maintaining the independence and quality of life of the third age individuals. However, since older people brings deterioration of cognitive, physical and visual abilities, resulting in slower reaction times and lapses while driving. The third age individuals are involved in more vehicle related accidents than middle aged individuals. This scenario is corrected by the fact that the number of third age individuals is increasing, especially in developed countries. It is expected that the percentage of third age individuals in the United Kingdom will increase to 20% of the total population by 2010. Several safety systems have been developed by the automotive industry including intelligent airbags, Electronic Stability Control (ESC) and pre-tensioned seat belts, but nothing has been specifically developed for the third age related problems. This thesis proposes a driver posture identification system using low resolution infrared imaging. The use of a low resolution thermal imager provides a reliable non-contact based posture identification system at a relatively low cost and is shown to provide robust performance over a wide range of conditions. The low resolution also protects the privacy of the driver. In order to develop the proposed safety system an Artificial Intelligent Thermal Imaging algorithm (AITl) is created in MatLAB. Experimentation is conducted in real and simulated environment, with human subjects, to evaluate the results of the algorithm. The result shows that the safety system is able to identify eighteen different driving postures. The system also provides other valuable information about the driver such as driver physical built, fatigue, smoking, mobile phone usage, eye-height and trunk stability. It is clear that in incorporating this safety system in the overall automotive central strategy, better safety for third age individual can be achieved. This thesis provides various contributions to knowledge including a novel neural network design, a safety system using low resolution infrared imager and an algorithm that can identify driver posture.