Impact of FBGs reflectivity shape on spectra of radiation in 10 km Raman fibre laser

We study the impact of the shape of fibre Bragg gratings spectral reflectivity on spectral broadening in a 10 km Raman fibre laser. We show that, at high powers, spectral characteristics are determined by intra-cavity processes rather than by the gratings profile.

Measurement of key compositional parameters in two species of energy grass by Fourier transform infrared spectroscopy

Two energy grass species, switch grass, a North American tuft grass, and reed canary grass, a European native, are likely to be important sources of biomass in Western Europe for the production of biorenewable energy. Matching chemical composition to conversion efficiency is a primary goal for improvement programmes and for determining the quality of biomass feed-stocks prior to use and there is a need for methods which allow cost effective characterisation of chemical composition at high rates of sample through-put. In this paper we demonstrate that nitrogen content and alkali index, parameters greatly influencing thermal conversion efficiency, can be accurately predicted in dried samples of these species grown under a range of agronomic conditions by partial least square regression of Fourier transform infrared spectra (R2 values for plots of predicted vs. measured values of 0.938 and 0.937, respectively). We also discuss the prediction of carbon and ash content in these samples and the application of infrared based predictive methods for the breeding improvement of energy grasses.

Turbulent broadening of optical spectra in ultralong Raman fiber lasers

We study the properties of radiation generated in ultralong fiber lasers and find an interesting link between these optical systems and the theory of weak wave turbulence. Experimental observations strongly suggest that turbulentlike weak interactions between the multitude of laser cavity modes are responsible for practical characteristics of ultralong fiber lasers such as spectra of the output radiation.

Polymer-phospholipid complexes for the solubilisation and delivery of drugs to the eye

Aim: Topical application of ophthalmic drugs is very inefficient; contact lenses used as drug delivery devices could minimize the drug loss and side effects. Styrene-maleic acid copolymers (PSMA) can form polymer-phospholipid complexes with dipalmitoyl phosphatidylcholine (DMPC) in the form of nanometric vesicles, which can easily solubilise hydrophobic drugs. They can be dispersed on very thin contact lens coatings to immobilize the drug on their surface. Methods: Two types of complexes stable at different pH values (5 and 7 respectively) where synthesized and loaded with drugs of different hydrophilicities during their formation process. The drug release was studied in vitro and compared to the free drug. Results: The mean sizes of the complexes obtained by light scattering were 50 nm and 450 nm respectively with low polydispersities. However, they were affected by the drugs load and release. An increase was observed in the duration of the release in the case of hydrophobic drugs, from days to weeks, avoiding initial “burst” and with a lesser amount of total drug released due to the interaction of the drug with the phospholipid core. The size and charge of the different drugs and the complexes nature also affected the release profile. Conclusions: Polymer-phospholipid complexes in the form of nanoparticles can be used to solubilise and release hydrophobic drugs in a controlled way. The drug load and release can be optimised to reach therapeutic values in the eye.

Advanced fibre gratings fabricated in standard and infrared glass fibres by ultraviolet and near-infrared-femtosecond lasers

In this thesis, I describe studies on fabrication, spectral characteristics and applications of tilted fibre gratings (TFGs) with small, large and 45° tilted structures and novel developments in fabrication of fibre Bragg gratings (FBGs) and long period gratings (LPGs) in normal silica and mid-infrared (mid-IR) glass fibres using near-IR femtosecond laser. One of the major contributions presented in this thesis is the systematic investigation of structures, inscription methods and spectral, polarisation dependent loss (PDL) and thermal characteristics of TFGs with small (<45°), large (>45°) and 45° tilted structures. I have experimentally characterised TFGs, obtaining relationships between the radiation angle, central wavelength of the radiation profile, Bragg resonance and the tilt angle, which are consistent with theoretical simulation based on the mode-coupling theory. Furthermore, thermal responses have been measured for these three types of TFGs, showing the transmission spectra of large and 45° TFGs are insensitive to the temperature change, unlike the normal and small angle tilted FBGs. Based on the distinctive optical properties, TFGs have been developed into interrogation system and sensors, which form the other significant contributions of the work presented in this thesis. The 10°-TFG based 800nm WDM interrogation system can function not just as an in-fibre spectrum analyser but also possess refractive index sensing capability. By utilising the unique polarisation properties, the 81 °-TFG based sensors are capable of sensing the transverse loading and twisting with sensitivities of 2.04pW/(kg/m) and 145.90pW/rad, repectively. The final but the most important contribution from the research work presented in this thesis is the development of novel grating inscription techniques using near-IR femtosecond laser. A number of LPGs and FBGs were successfully fabricated in normal silica and mid-IR glass fibres using point-by-point and phase-mask techniques. LPGs and 1st and 2nd order FBGs have been fabricated in these mid-IR glass fibres showing resonances covering the wavelength range from 1200 to 1700nm with the strengths up to 13dB. In addition, the thermal and strain sensitivities of these gratings have been systematically investigated. All the results from these initial but systematic works will provide useful function characteristics information for future fibre grating based devices and applications in mid-IR range.

Fast pyrolysis and nitrogenolysis of biomass and biogenic residues:production of a sustainable slow release fertiliser

The production of agricultural and horticultural products requires the use of nitrogenous fertiliser that can cause pollution of surface and ground water and has a large carbon footprint as it is mainly produced from fossil fuels. The overall objective of this research project was to investigate fast pyrolysis and in-situ nitrogenolysis of biomass and biogenic residues as an alternative route to produce a sustainable solid slow release fertiliser mitigating the above stated problems. A variety of biomasses and biogenic residues were characterized by proximate analysis, ultimate analysis, thermogravimetric analysis (TGA) and Pyrolysis – Gas chromatography – Mass Spectroscopy (Py–GC–MS) for their potential use as feedstocks using beech wood as a reference material. Beech wood was virtually nitrogen free and therefore suitable as a reference material as added nitrogen can be identified as such while Dried Distillers Grains with Solubles (DDGS) and rape meal had a nitrogen content between 5.5wt.% and 6.1wt.% qualifying them as high nitrogen feedstocks. Fast pyrolysis and in-situ nitrogenolysis experiments were carried out in a continuously fed 1kg/h bubbling fluidized bed reactor at around 500°C quenching the pyrolysis vapours with isoparaffin. In-situ nitrogenolysis experiments were performed by adding ammonia gas to the fast pyrolysis reactor at nominal nitrogen addition rates between 5wt.%C and 20wt.%C based on the dry feedstock’s carbon content basis. Mass balances were established for the processing experiments. The fast pyrolysis and in-situ nitrogenolysis products were characterized by proximate analysis, ultimate analysis and GC– MS. High liquid yields and good mass balance closures of over 92% were obtained. The most suitable nitrogen addition rate for the in-situ nitrogenolysis experiments was determined to be 12wt.%C on dry feedstock carbon content basis. However, only a few nitrogen compounds that were formed during in-situ nitrogenolysis could be identified by GC–MS. A batch reactor process was developed to thermally solidify the fast pyrolysis and in-situ nitrogenolysis liquids of beech wood and Barley DDGS producing a brittle solid product. This was obtained at 150°C with an addition of 2.5wt% char (as catalyst) after a processing time of 1h. The batch reactor was also used for modifying and solidifying fast pyrolysis liquids derived from beech wood by adding urea or ammonium phosphate as post processing nitrogenolysis. The results showed that this type of combined approach was not suitable to produce a slow release fertiliser, because the solid product contained up to 65wt.% of highly water soluble nitrogen compounds that would be released instantly by rain. To complement the processing experiments a comparative study via Py–GC–MS with inert and reactive gas was performed with cellulose, hemicellulose, lignin and beech wood. This revealed that the presence of ammonia gas during analytical pyrolysis did not appear to have any direct impact on the decomposition products of the tested materials. The chromatograms obtained showed almost no differences between inert and ammonia gas experiments indicating that the reaction between ammonia and pyrolysis vapours does not occur instantly. A comparative study via Fourier Transformed Infrared Spectroscopy of solidified fast pyrolysis and in-situ nitrogenolysis products showed that there were some alterations in the spectra obtained. A shift in frequencies indicating C=O stretches typically related to the presence of carboxylic acids to C=O stretches related to amides was observed and no double or triple bonded nitrogen was detected. This indicates that organic acids reacted with ammonia and that no potentially harmful or non-biodegradable triple bonded nitrogen compounds were formed. The impact of solid slow release fertiliser (SRF) derived from pyrolysis and in-situ nitrogenolysis products from beech wood and Barley DDGS on microbial life in soils and plant growth was tested in cooperation with Rothamsted Research. The microbial incubation tests indicated that microbes can thrive on the SRFs produced, although some microbial species seem to have a reduced activity at very high concentrations of beech wood and Barley DDGS derived SRF. The plant tests (pot trials) showed that the application of SRF derived from beech wood and barley DDGS had no negative impact on germination or plant growth of rye grass. The fertilizing effect was proven by the dry matter yields in three harvests after 47 days, 89 days and 131 days. The findings of this research indicate that in general a slow release fertiliser can be produced from biomass and biogenic residues by in-situ nitrogenolysis. Nevertheless the findings also show that additional research is necessary to identify which compounds are formed during this process.

Matrix-assisted diffusion-ordered spectroscopy:application of surfactant solutions to the resolution of isomer spectra

The component spectra of a mixture of isomers with nearly identical diffusion coefficients cannot normally be distinguished in a standard diffusion-ordered spectroscopy (DOSY) experiment but can often be easily resolved using matrix-assisted DOSY, in which diffusion behaviour is manipulated by the addition of a co-solute such as a surfactant. Relatively little is currently known about the conditions required for such a separation, for example, how the choice between normal and reverse micelles affects separation or how the isomer structures themselves affect the resolution. The aim of this study was to explore the application of sodium dodecyl sulfate (SDS) normal micelles in aqueous solution and sodium 1,4-bis(2-ethylhexyl)sulfosuccinate (AOT) aggregates in chloroform, at a range of concentrations, to the diffusion resolution of some simple model sets of isomers such as monomethoxyphenols and short chain alcohols. It is shown that SDS micelles offer better resolution where these isomers differ in the position of a hydroxyl group, whereas AOT aggregates are more effective for isomers differing in the position of a methyl group. For both the normal SDS micelles and the less well-defined AOT aggregates, differences in the resolution of the isomers can in part be rationalised in terms of differing degrees of hydrophobicity, amphiphilicity and steric effects. Copyright © 2012 John Wiley & Sons, Ltd.

Metallocene ethylene-1-octene copolymers:influence of comonomer content on thermo-mechanical, rheological, and thermo-oxidative behaviours before and after melt processing in an internal mixer

The influence of the comonomer content in a series of metallocene-based ethylene-1-octene copolymers (m-LLDPE) on thermo-mechanical, rheological, and thermo-oxidative behaviours during melt processing were examined using a range of characterisation techniques. The amount of branching was calculated from 13C NMR and studies using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) were employed to determine the effect of short chain branching (SCB, comonomer content) on thermal and mechanical characteristics of the polymer. The effect of melt processing at different temperatures on the thermo-oxidative behaviour of the polymers was investigated by examining the changes in rheological properties, using both melt flow and capillary rheometry, and the evolution of oxidation products during processing using infrared spectroscopy. The results show that the comonomer content and catalyst type greatly affect thermal, mechanical and oxidative behaviour of the polymers. For the metallocene polymer series, it was shown from both DSC and DMA that (i) crystallinity and melting temperatures decreased linearly with comonomer content, (ii) the intensity of the ß-transition increased, and (iii) the position of the tan δmax peak corresponding to the a-transition shifted to lower temperatures, with higher comonomer content. In contrast, a corresponding Ziegler polymer containing the same level of SCB as in one of the m-LLDPE polymers, showed different characteristics due to its more heterogeneous nature: higher elongational viscosity, and a double melting peak with broader intensity that occurred at higher temperature (from DSC endotherm) indicating a much broader short chain branch distribution. The thermo-oxidative behaviour of the polymers after melt processing was similarly influenced by the comonomer content. Rheological characteristics and changes in concentrations of carbonyl and the different unsaturated groups, particularly vinyl, vinylidene and trans-vinylene, during processing of m-LLDPE polymers, showed that polymers with lower levels of SCB gave rise to predominantly crosslinking reactions at all processing temperatures. By contrast, chain scission reactions at higher processing temperatures became more favoured in the higher comonomer-containing polymers. Compared to its metallocene analogue, the Ziegler polymer showed a much higher degree of crosslinking at all temperatures because of the high levels of vinyl unsaturation initially present.

Plasminogen activator inhibitor-1 supports IL-8-mediated neutrophil transendothelial migration by inhibition of the constitutive shedding of endothelial IL-8/heparan sulfate/syndecan-1 complexes

The endothelium is the primary barrier to leukocyte recruitment at sites of inflammation. Neutrophil recruitment is directed by transendothelial gradients of IL-8 that, in vivo, are bound to the endothelial cell surface. We have investigated the identity and function of the binding site(s) in an in vitro model of neutrophil transendothelial migration. In endothelial culture supernatants, IL-8 was detected in a trimolecular complex with heparan sulfate and syndecan-1. Constitutive shedding of IL-8 in this form was increased in the presence of a neutralizing Ab to plasminogen activator inhibitor-1 (PAI-1), indicating a role for endothelial plasminogen activator in the shedding of IL-8. Increased shedding of IL-8/heparan sulfate/syndecan-1 complexes was accompanied by inhibition of neutrophil transendothelial migration, and aprotinin, a potent plasmin inhibitor, reversed this inhibition. Platelets, added as an exogenous source of PAI-1, had no effect on shedding of the complexes or neutrophil migration. Our results indicate that IL-8 is immobilized on the endothelial cell surface through binding to syndecan-1 ectodomains, and that plasmin, generated by endothelial plasminogen activator, induces the shedding of this form of IL-8. PAI-1 appears to stabilize the chemoattractant form of IL-8 at the cell surface and may represent a therapeutic target for novel anti-inflammatory strategies.