Biomimetic synthetic lubricants (Biosurfactants)

Poly(styrene-co-maleic anhydride) (PSMA) based copolymers are known to undergo conformational transition in response to environmental stimuli. This smart behaviour makes it possible to mimic the behaviour of native apoproteins. The primary aim of this study was to develop a better understanding of the structure-property relationships of various PSMA-based copolymers sought. The work undertaken in this thesis has revealed that the responsive behaviour of PSMA-based copolymers can be tailored by varying the molecular weight, hydrophobic (styrene) and hydrophilic (maleic acid) balance, and more so in the presence of additional hydrophobic, mono-partial ester moieties. Novel hydrophilic and hydrophobic synthetic surfactant protein analogues have successfully been prepared. These novel lipid solubilising agents possess a broad range of HLB (hydrophilic-lipophilic balance) values that have been estimated. NMR spectroscopy was utilised to confirm the structures for PSMA-based copolymers sought and proved useful in furthering understanding of the structure-property relationships of PSMA-based copolymers. The association of PSMA with the polar phospholipid, 2-dilauryl-sn-glycero-3- phosphocholine (DLPC) produces polymer-lipid complexes analogous to lipoprotein assemblies present in the blood plasma. NMR analysis reveals that the PSMA-based copolymers are not perfectly alternating. Regio-irregular structures, atactic and random monomer sequence distribution have been identified for all materials studied. Novel lipid solubilising agents (polyanionic surfactants) have successfully been synthesised from a broad range of PSMA-based copolymers with desired estimated HLB values that interact with polar phospholipids (DLPC/DPPC) uniquely. Very low static and dynamic surface tensions have been observed via the du Noϋy ring method and Langmuir techniques and correlate well with the estimated HLB values. Synthetic protein-lipid analogues have been successfully synthesised, that mimic the unique surface properties of native biological lubricants without the use of solvents. The novel PSMA-DLPC complexes have successfully been combined with hyaluronan (hyaluronic acid, HA). Today, the employment of HA is economically feasible, because it is readily available from bacterial fermentation processes in a thermally stable form - HyaCare®. The work undertaken in this thesis highlights the usage of HA in biolubrication applications and how this can be optimised and thus justified by carefully selecting the biological source, concentration, molecular weight, purity and most importantly by combining it with compatible boundary lubricating agents (polar phospholipids). Experimental evidence supports the belief that the combined HA and PSMA-DLPC complexes provide a balance of rheological, biotribological and surface properties that are composition dependent, and show competitive advantage as novel synthetic biological lubricants (biosurfactants).

Differing effects of two synthetic phonics programmes on early reading development

Background: Synthetic phonics is the widely accepted approach for teaching reading in English: children are taught to sound out the letters in a word then blend these sounds together. Aims: We compared the impact of two synthetic phonics programmes on early reading.SampleChildren received Letters and Sounds (L&S; 7 schools) which teaches multiple letter-sound mappings or Early Reading Research (ERR; 10 schools) which teaches only the most consistent mappings plus frequent words by sight.MethodWe measured phonological awareness (PA) and reading from school entry to the end of the second (all schools) or third school year (4 ERR, 3 L&S schools). Results: PA was significantly related to all reading measures for the whole sample. However, there was a closer relationship between PA and exception word reading for children receiving the L&S programme. The programmes were equally effective overall, but their impact on reading significantly interacted with school-entry PA: children with poor PA at school entry achieved higher reading attainments under ERR (significant group difference on exception word reading at the end of the first year), whereas children with good PA performed equally well under either programme. Conclusions: The more intensive phonics programme (L&S) heightened the association between PA and exception word reading. Although the programmes were equally effective for most children, results indicate potential benefits of ERR for children with poor PA. We suggest that phonics programmes could be simplified to teach only the most consistent mappings plus frequent words by sight.

Association behavior of the synthetic protein-lipid complex analogues

Hypercoiling poly(styrene-ALT-maleic anhydride) (PSMA) is known to undergo conformational transition in response to environmental stimuli. This behavior allows it to associate with the phospholipid, 2-dilauryl-SN-glycero-3- phosphocholine (DLPC) to produce nanostructures analogous to lipoproteins. The complex represents a new bio-mimetic delivery vehicle with applications in the cosmetic and pharmaceutical industries. This study investigates, for the first time, the association behavior of PSMA and DLPC through the combination of different analytical techniques. The results indicate that the association is primarily driven by hydrophobic interactions and depends on various factors including the polymer/lipid ratio, the polymer molecular weight and the pH of the aqueous environment. The conformational transition of PSMA leads to the formation of discrete micellar complexes involving anisotropic-to-isotropic lipid phase transformation. As the number of hydrophobic moieties in the polymer is increased, the pH-dependent conformational transition of the polymer plays less important part in achieving this phase transition of the lipid. © (2012) Trans Tech Publications.

Pd/C catalysts based on synthetic carbons with bi- and tri-modal pore-size distribution:applications in flow chemistry

Two new types of phenolic resin-derived synthetic carbons with bi-modal and tri-modal pore-size distributions were used as supports for Pd catalysts. The catalysts were tested in chemoselective hydrogenation and hydrodehalogenation reactions in a compact multichannel flow reactor. Bi-modal and tri-modal micro-mesoporous structures of the synthetic carbons were characterised by N2 adsorption. HR-TEM, PXRD and XPS analyses were performed for characterising the synthesised catalysts. N2 adsorption revealed that tri-modal synthetic carbon possesses a well-developed hierarchical mesoporous structure (with 6.5 nm and 42 nm pores), contributing to a larger mesopore volume than the bi-modal carbon (1.57 cm3 g-1versus 1.23 cm3 g-1). It was found that the tri-modal carbon promotes a better size distribution of Pd nanoparticles than the bi-modal carbon due to presence of hierarchical mesopore limitting the growth of Pd nanoparticles. For all the model reactions investigated, the Pd catalyst based on tri-modal synthetic carbon (Pd/triC) show high activity as well as high stability and reproducibility. The trend in reactivities of different functional groups over the Pd/triC catalyst follows a general order alkyne ≫ nitro > bromo ≫ aldehyde.

Anderson localization of light in synthetic photonic lattices

We make an comprehensive experimental and theoretical study of an effect of localization of light in photonic lattices realized in time domain with random optical potential. We show that localization occurs in whole range of disorder strength in full agreement with Anderson localization in 1D model. The disorder influence on modes structure is also discussed.

Surface waves in mesh synthetic photonic lattices

Eigenmodes and dispersion curves in different configurations of synthetic photonic lattices are studied numerically. Eigenmodes localized on borders between areas with different optical potential are found. Stability of these eigenmodes against potential disturbances of different type is studied.

Constructing eigenmode excitation spectrum in synthetic photonic lattices using optical heterodyning

A method based on optical heterodyning is proposed for measuring relative optical phases of pulses circulating in a synthetic photonic lattices. The knowledge of the phases can be further used for qualitative reconstruction of an eigenmode excitation spectrum in the synthetic photonic lattice.