Application and use of isothermal calorimetry in pharmaceutical development

There are many steps involved in developing a drug candidate into a formulated medicine and many involve analysis of chemical interaction or physical change. Calorimetry is particularly suited to such analyses as it offers the capacity to observe and quantify both chemical and physical changes in virtually any sample. Differential scanning calorimetry (DSC) is ubiquitous in pharmaceutical development, but the related technique of isothermal calorimetry (IC) is complementary and can be used to investigate a range of processes not amenable to analysis by DSC. Typically, IC is used for longer-term stability indicating or excipient compatibility assays because both the temperature and relative humidity (RH) in the sample ampoule can be controlled. However, instrument design and configuration, such as titration, gas perfusion or ampoule-breaking (solution) calorimetry, allow quantification of more specific values, such as binding enthalpies, heats of solution and quantification of amorphous content. As ever, instrument selection, experiment design and sample preparation are critical to ensuring the relevance of any data recorded. This article reviews the use of isothermal, titration, gas-perfusion and solution calorimetry in the context of pharmaceutical development, with a focus on instrument and experimental design factors, highlighted with examples from the recent literature. © 2011 Elsevier B.V.

Evaluation of the activity and stability of alkali-doped metal oxide catalysts for application to an intensified method of biodiesel production

A series of alkali-doped metal oxide catalysts were prepared and evaluated for activity in the transesterification of rapeseed oil to biodiesel. Of those evaluated, LiNO3/CaO, NaNO3/CaO, KNO3/CaO and LiNO3/MgO exhibited >90% conversion in a standard 3 h test. There was a clear correlation between base strength and activity. These catalysts appeared to be promising candidates to replace conventional homogeneous catalysts for biodiesel production as the reaction times are low enough to be practical in continuous processes and the preparations are neither prohibitively difficult nor costly. However, metal leaching from the catalyst was detected, and this resulted in some homogeneous activity. This would have to be resolved before these catalysts would be viable for large-scale biodiesel production facilities.

Modelling of induction motors for system faults and transient stability studies

The research carried out in this thesis was mainly concerned with the effects of large induction motors and their transient performance in power systems. Computer packages using the three phase co-ordinate frame of reference were developed to simulate the induction motor transient performance. A technique using matrix algebra was developed to allow extension of the three phase co-ordinate method to analyse asymmetrical and symmetrical faults on both sides of the three phase delta-star transformer which is usually required when connecting large induction motors to the supply system. System simulation, applying these two techniques, was used to study the transient stability of a power system. The response of a typical system, loaded with a group of large induction motors, two three-phase delta-star transformers, a synchronous generator and an infinite system was analysed. The computer software developed to study this system has the advantage that different types of fault at different locations can be studied by simple changes in input data. The research also involved investigating the possibility of using different integrating routines such as Runge-Kutta-Gill, RungeKutta-Fehlberg and the Predictor-Corrector methods. The investigation enables the reduction of computation time, which is necessary when solving the induction motor equations expressed in terms of the three phase variables. The outcome of this investigation was utilised in analysing an introductory model (containing only minimal control action) of an isolated system having a significant induction motor load compared to the size of the generator energising the system.

Mathematical methods in power system stability studies

In this thesis various mathematical methods of studying the transient and dynamic stabiIity of practical power systems are presented. Certain long established methods are reviewed and refinements of some proposed. New methods are presented which remove some of the difficulties encountered in applying the powerful stability theories based on the concepts of Liapunov. Chapter 1 is concerned with numerical solution of the transient stability problem. Following a review and comparison of synchronous machine models the superiority of a particular model from the point of view of combined computing time and accuracy is demonstrated. A digital computer program incorporating all the synchronous machine models discussed, and an induction machine model, is described and results of a practical multi-machine transient stability study are presented. Chapter 2 reviews certain concepts and theorems due to Liapunov. In Chapter 3 transient stability regions of single, two and multi~machine systems are investigated through the use of energy type Liapunov functions. The treatment removes several mathematical difficulties encountered in earlier applications of the method. In Chapter 4 a simple criterion for the steady state stability of a multi-machine system is developed and compared with established criteria and a state space approach. In Chapters 5, 6 and 7 dynamic stability and small signal dynamic response are studied through a state space representation of the system. In Chapter 5 the state space equations are derived for single machine systems. An example is provided in which the dynamic stability limit curves are plotted for various synchronous machine representations. In Chapter 6 the state space approach is extended to multi~machine systems. To draw conclusions concerning dynamic stability or dynamic response the system eigenvalues must be properly interpreted, and a discussion concerning correct interpretation is included. Chapter 7 presents a discussion of the optimisation of power system small sjgnal performance through the use of Liapunov functions.

Improvement of bio-oil stability in wood pyrolysis process

Pyrolysis is one of several thermochemical technologies that convert solid biomass into more useful and valuable bio-fuels. Pyrolysis is thermal degradation in the complete or partial absence of oxygen. Under carefully controlled conditions, solid biomass can be converted to a liquid known as bie-oil in 75% yield on dry feed. Bio-oil can be used as a fuel but has the drawback of having a high level of oxygen due to the presence of a complex mixture of molecular fragments of cellulose, hemicellulose and lignin polymers. Also, bio-oil has a number of problems in use including high initial viscosity, instability resulting in increased viscosity or phase separation and high solids content. Much effort has been spent on upgrading bio-oil into a more usable liquid fuel, either by modifying the liquid or by major chemical and catalytic conversion to hydrocarbons. The overall primary objective was to improve oil stability by exploring different ways. The first was to detennine the effect of feed moisture content on bio-oil stability. The second method was to try to improve bio-oil stability by partially oxygenated pyrolysis. The third one was to improve stability by co-pyrolysis with methanol. The project was carried out on an existing laboratory pyrolysis reactor system, which works well with this project without redesign or modification too much. During the finishing stages of this project, it was found that the temperature of the condenser in the product collection system had a marked impact on pyrolysis liquid stability. This was discussed in this work and further recommendation given. The quantity of water coming from the feedstock and the pyrolysis reaction is important to liquid stability. In the present work the feedstock moisture content was varied and pyrolysis experiments were carried out over a range of temperatures. The quality of the bio-oil produced was measured as water content, initial viscosity and stability. The result showed that moderate (7.3-12.8 % moisture) feedstock moisture led to more stable bio-oil. One of drawbacks of bio-oil was its instability due to containing unstable oxygenated chemicals. Catalytic hydrotreatment of the oil and zeolite cracking of pyrolysis vapour were discllssed by many researchers, the processes were intended to eliminate oxygen in the bio-oil. In this work an alternative way oxygenated pyrolysis was introduced in order to reduce oil instability, which was intended to oxidise unstable oxygenated chemicals in the bio-oil. The results showed that liquid stability was improved by oxygen addition during the pyrolysis of beech wood at an optimum air factor of about 0.09-0.15. Methanol as a postproduction additive to bio-oil has been studied by many researchers and the most effective result came from adding methanol to oil just after production. Co-pyrolysis of spruce wood with methanol was undertaken in the present work and it was found that methanol improved liquid stability as a co-pyrolysis solvent but was no more effective than when used as a postproduction additive.

The effect of certain hydrophilic polymers on suspension stability

The adsorption of nonionic surface active agents of polyoxyethylene glycol monoethers of n hexadecanols on polystyrene latex and nonionic cellulose polymers of hydroxyethyl cellulose, hydroxypropyl cellulose and hydroxypropyl methylcellulose on polystyrene latex and ibuprofen drug particles have been studied. The adsorbed layer thicknesses were determined by means of microelectrophoretic and viscometric methods. The conformation of the adsorbed molecules at the solid-liquid interface was deduced from the molecular areas and the adsorbed layer thicknesses. Comparison of the adsorption results obtained from polystyrene latex and ibuprofen particles was made to explain the conformation difference between these two adsorbates. Sedimentation volumes and redispersibility values were the main criteria used to evaluate suspension stability. At low concentrations of surface active agents, hard caked suspensions were found, probably due to the attraction between the uncoated areas or, the mutual adsorption of the adsorbed molecules on the bare surface of the particles in the sediment. At high concentrations of hydroxypropyl cellulose and hydroxypropyl methylcellulose, heavily caked sediments were attributed to network structure formation by the adsorbed molecules. An attempt was made to relate the characteristics of the suspensions to the potential energy of interaction curves. Generally, the agreement between theory and experiment was good, but for hydroxyethyl cellulose-ibuprofen systems discrepancies were found. Experimental studies showed that hydroxyethyl cellulose flocculated polystyrene latex over a rather wide range of concentrations; similarly, hydroxyethyl cellulose-ibuprofen suspensions were also flocculated. Therefore, it ls suggested that a term to account for flocculation energy of the polymer should be added to the total energy of interaction. A rheometric method was employed to study the flocculation energy of the polymer.

The stability of pharmaceutical powders: effect of additives and coating

The decomposition of drugs in the solid state has been studied using aspirin and salsalate as models. The feasibility of using suspension systems for predicting the stability of these drugs in the solid state has been investigated.. It has been found that such systems are inappropriate in defining the effect of excipients on 'the decomposition of the active drug due to chqnges in the degradation pathway. Using a high performance liquid chromatographic method, magnesium stearate was shown to induce the formation of potentlally immunogenic products in aspirin powders. These products which included salicylsalicylic acid .and acetylsalicyclsalicylic acid were not detected in aspirin suspensions which had undergone the same extent of decomposition. By studying the effect of pH and of added excipients on the rate of decomposition of aspirin in suspension systems, it has been shown that excipients such as magnesium stearate containing magnesium oxide, most probably enhance the decomposition of both aspirin and salsalate by alkalinising the aqueous phase. In the solid state, pH effects produced by excipients appear to be relatively unimportant. Evidence is presented to suggest that the critical parameter is a depression in melting point induced by: the added excipient. Microscopical examination in fact showed the formation of clear liquid layers in aspirin samples containing added magnesium stearate but not in control samples. Kinetic equations which take into account both the diffusive barrier presented by the liquid films and the. geometry of the aspirin crystals were developed. Fitting of the .experimental data to these equations showed good agreement. with the postulated theory. Monitorjng of weight issues during the decomposition of aspirin revealed that in the solid systems studied where the bulk of the decomposition product sublimes, it is possible to estimate the extent of degradation from the residual weight, provided the initial weight is known. The corollary is that in such open systems, monitoring of decomposition products is inadequate for assessing the extent of decomposition. In addition to the magnesium stearate-aspirin system, mapyramine maleate-aspirin mixtures were used to model interactive systems. Work carried out in an attempt to stabilise such systems included microencapsulation and film coating. The protection obtained was dependent on the interactive species used. Gelatin for example appeared to stabilise aspirin against the adverse effects of magnesium stearate but increased its decomposition in the presence of mapyramine maleate.

The stability and formulation of topical analgesics

High-performance liquid chromatographic methods are developed for the simultaneous determination of various salicylates, their p-hydroxy isomers and nicotinic acid esters. The method is sensitive enough to detect trace amounts (~µM/L)of the product generated from cross reactivity between the drugs and the vehicle. The developed method also allows analysis of various topical products containing salicylate and nicotinate esters in their formulations. Applying this method, the degradation profiles of salicylates, nicotinates, p-hydroxy benzoate, o-methoxy benzoate and aspirin prodrugs in alkaline media are determined. The profile for alkyl salicylate degradation is found to be first order (A---? B) When the alcoholic radical is similar to that of the ester. In alcohol having a radical different from that of the ester function, the degradation is found to proceed through competitive transesterification and hydrolysis. The intermediates are identified following synthesis and isolation. The rate and extent of transesterification depends on the proportion of alcohol present in the system. Equations are presented to model the time profiles of reactant and product concentration. The reactions are base catalysed and the predominant pathway involves a concerted solvent attack upon the salicylate anion. Competitive hydrolysis of both ester components also follows this mechanism at moderate pH values but rates increase under strongly alkaline conditions as direct hydroxide attack becomes significant. In contrast, transesterification is independent of base concentration once full ionization is accomplished. The competitive hydrolysis is modelled using equations involving the dielectric constant of the medium. A range of other esters are also shown to undergo base-catalysed transesterification. In non-alcoholic solution phenyl salicylate undergoes a concentration-dependent oligomerisation which yields salsalate among the products. Competitive transesterification and hydrolysis also occur in products for topical use which have vehicles based upon alcohol, glycol or glycol polymers. Such reactions may compromise stability assessments, pharmaceutical integrity and delivery profiles.

Characterisation and oxidative stability of speciality plant seed oils

The past decade has seen an influx of speciality plant seed oils arriving into the market place. The need to characterise these oils has become an important aspect of the oil industry. The characterisation of the oils allows for the physical and chemical properties of the oil to be determined. Speciality oils were characterised based on their lipid and fatty acid profiles and categorised as monounsaturated rich (oleic acid as the major acyl components e.g. Moringa and Marula oil), linoleic acid rich (Grape seed and Evening Primrose oil) or linolenic acid rich (Flaxseed and Kiwi oil). The quality of the oils was evaluated by determining the free fatty acid content, the peroxide value (that measures initial oxidation) and p-anisidine values (that determines secondary oxidation products containing the carbonyl function). A reference database was constructed for the oils in order to compare batches of oils for their overall quality including oxidative stability. For some of the speciality oils, the stereochemistry of the triacylglycerols was determined. Calophyllum, Coffee, Poppy and Sea Buckthorn oils stereochemistry was determined. The oils were enriched with saturated and/or a monounsaturated fatty acids at position sn-1 and sn-3. The sn-2 position of the four oils was esterified with a polyunsaturated and/or a monounsaturated fatty acid indicating that they follow a typical acylation pathway and no novel acylation activity was evident from these studies (e.g enrichment of saturates at the sn-2 position). The oxidative stability of the oils was evaluated at 18oC and 60oC and the effect of adding a-tocopherol at commercially used level i.e 750ppm was assessed. The addition of 750ppm of a-tocopherol at 18oC increased the oxidative stability of Brown flax, Moringa, Wheat germ and Yangu oils. At 60oC Brown Flax, Manketti and Pomegranate oil polymerised after 48 hours. The addition of 750ppm a-tocopherol delayed the onset of polymerisation by up to 48 hours in Brown Flax seed oil. Pomegranate oil showed a high resistance to oxidation, and was blended into other speciality oils at 1%. Pomegranate oil increased the oxidative stability of Yangu oil at 18oC. The addition of Pomegranate oil to Wheat germ oil at 60oC, decreased the peroxide content by 10%. In Manketti and Brown Flaxseed oil at elevated temperatures, Pomegranate oil delayed the onset of polymerisation. Preliminary studies of Pomegranate oil blending to Moringa and Borage oil showed it to be more effective than a-tocopherol for certain oils. The antioxidant effects observed following the addition of Pomegranate oil may be due to its conjugated linolenic acid fatty acid, punicic acid.

Techniques for determining bias and stability in satellite altimeters

The case for monitoring large-scale sea level variability is established in the context of the estimation of the extent of anthropogenic climate change. Satellite altimeters are identified as having the potential to monitor this change with high resolution and accuracy. Possible sources of systematic errors and instabilities in these instruments which would be hurdles to the most accurate monitoring of such ocean signals are examined. Techniques for employing tide gauges to combat such inaccuracies are proposed and developed. The tide gauge at Newhaven in Sussex is used in conjunction with the nearby satellite laser ranger and high-resolution ocean models to estimate the absolute bias of the TOPEX, Poseidon, ERS 1 and ERS 2 altimeters. The theory which underlies the augmentation of altimeter measurements with tide gauge data is developed. In order to apply this, the tide gauges of the World Ocean Circulation Experiment are assessed and their suitability for altimeter calibration is determined. A reliable subset of these gauges is derived. A method of intra-altimeter calibration is developed using these tide gauges to remove the effect of variability over long time scales. In this way the long-term instability in the TOPEX range measurement is inferred and the drift arising from the on-board ultra stable oscillator is thus detected. An extension to this work develops a method for inter-altimeter calibration, allowing the systematic differences between unconnected altimeters to be measured. This is applied to the TOPEX and ERS 1 altimeters.

Remote sensing applied to slope stability in mountainous roads in Iran

The Alborz Mountain range separates the northern part of Iran from the southern part. It also isolates a narrow coastal strip to the south of the Caspian Sea from the Central Iran plateau. Communication between the south and north until the 1950's was via two roads and one rail link. In 1963 work was completed on a major access road via the Haraz Valley (the most physically hostile area in the region). From the beginning the road was plagued by accidents resulting from unstable slopes on either side of the valley. Heavy casualties persuaded the government to undertake major engineering works to eliminate ''black spots" and make the road safe. However, despite substantial and prolonged expenditure the problems were not solved and casualties increased steadily due to the increase in traffic using the road. Another road was built to bypass the Haraz road and opened to traffic in 1983. But closure of the Haraz road was still impossible because of the growth of settlements along the route and the need for access to other installations such as the Lar Dam. The aim of this research was to explore the possibility of applying Landsat MSS imagery to locating black spots along the road and the instability problems. Landsat data had not previously been applied to highway engineering problems in the study area. Aerial photographs are better in general than satellite images for detailed mapping, but Landsat images are superior for reconnaissance and adequate for mapping at the 1 :250,000 scale. The broad overview and lack of distortion in the Landsat imagery make the images ideal for structural interpretation. The results of Landsat digital image analysis showed that certain rock types and structural features can be delineated and mapped. The most unstable areas comprising steep slopes, free of vegetation cover can be identified using image processing techniques. Structural lineaments revealed from the image analysis led to improved results (delineation of unstable features). Damavand Quaternary volcanics were found to be the dominant rock type along a 40 km stretch of the road. These rock types are inherently unstable and partly responsible for the difficulties along the road. For more detailed geological and morphological interpretation a sample of small subscenes was selected and analysed. A special developed image analysis package was designed at Aston for use on a non specialized computing system. Using this package a new and unique method for image classification was developed, allowing accurate delineation of the critical features of the study area.

Immuno-potentiating activity of surfactant vesicles in DNA and subunit vaccination

Enhanced immune responses for DNA and subunit vaccines potentiated by surfactant vesicle based delivery systems outlined in the present study, provides proof of principle for the beneficial aspects of vesicle mediated vaccination. The dehydration-rehydration technique was used to entrap plasmid DNA or subunit antigens into lipid-based (liposomes) or non-ionic surfactant-based (niosomes) dehydration-rehydration vesicles (DRV). Using this procedure, it was shown that both these types of antigens can be effectively entrapped in DRV liposomes and DRV niosomes. The vesicle size of DRV niosomes was shown to be twice the diameter (~2µm) of that of their liposome counterparts. Incorporation of cryoprotectants such as sucrose in the DRV procedure resulted in reduced vesicle sizes while retaining high DNA incorporation efficiency (~95%). Transfection studies in COS 7 cells demonstrated that the choice of cationic lipid, the helper lipid, and the method of preparation, all influenced transfection efficiency indicating a strong interdependency of these factors. This phenomenon has been further reinforced when 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE): cholesteryl 3b- [N-(N’ ,N’ -dimethylaminoethane)-carbamoyl] cholesterol (DC-Chol)/DNA complexes were supplemented with non-ionic surfactants. Morphological analysis of these complexes using transmission electron microscopy and environmental scanning electron microscopy (ESEM) revealed the presence of heterogeneous structures which may be essential for an efficient transfection in addition to the fusogenic properties of DOPE. In vivo evaluation of these DNA incorporated vesicle systems in BALB/c mice showed weak antibody and cell-mediated immune (CMI) responses. Subsequent mock challenge with hepatitis B antigen demonstrated that, 1-monopalmitoyl glycerol (MP) based DRV, is a more promising DNA vaccine adjuvant. Studying these DRV systems as adjuvants for the Hepatitis B subunit antigen (HBsAg) revealed a balanced antibody/CMI response profile on the basis of the HBsAg specific antibody and cytokine responses which were higher than unadjuvated antigen. The effect of addition of MP, cholesterol and trehalose 6,6’-dibehenate (TDB) on the stability and immuno-efficacy of dimethyldioctadecylammonium bromide (DDA) vesicles was investigated. Differential scanning calorimetry showed a reduction in transition temperature of DDA vesicles by ~12°C when incorporated with surfactants. ESEM of MP based DRV system indicated an increased vesicle stability upon incorporation of antigen. Adjuvant activity of these systems tested in C57BL/6j mice against three subunit antigens i.e., mycobacterial fusion protein- Ag85B-ESAT-6, and two malarial antigens - merozoite surface protein-1, (MSP1), and glutamate rich protein, (GLURP) revealed that while MP and DDA based systems induced comparable antibody responses, DDA based systems induced powerful CMI responses.

Design, synthesis and biological evaluation of potential antibacterial oligonucleotides

Purine and pyrimidine triplex-forming oligonucleotides (TFOs), as potential antibacterial agents, were designed to bind by Hoogsteen and reverse Hoogsteen hydrogen bonds in a sequence specific manner in the major groove of genomic DNA at specific polypurine sites within the gyrA gene of E. coli and S. pneumoniae. Sequences were prepared by automated synthesis, with purification and characterisation determined by high performance liquid chromatograpy, capillary electrophoresis and mass spectrometry. Triplex stability was assessed using melting curves where the binding of the third strand to the duplex target, was assessed over a temperature range of 0-80°C, and at pH 6.4 and 7.2. The most successful of the unmodified TFOs (6) showed a Tm value of 26 °C at both pH values with binding via reverse Hoogsteen bonds. Binding to genomic DNA was also demonstrated by spectrofluorimetry, using fluorescein-labelled TFOs, from which dissociation constants were determined. Modifications in the form of 5mC, 5' acridine attachment, phosphorothioation, 2'-0-methylation and phosphoramidation, were made in order to. increase Tm values. Phosphoramidate modification was the most with increased Tm values of 42°C. However, the final purity of these sequences was poor due to their difficult syntheses. FACS (fluorescent activated cell sorting) analysis was used to determine the potential uptake of a fluorescently labelled analogue of 6 via passive, coJd shock mediated, and anionic liposome aided, uptake. This was established at 20°C and 37°C. At both temperatures anionic lipid-mediated uptake produced unrivalled fluorescence, equivalent to 20 and 43% at 20 and 37°C respectively. Antibacterial activity of each oligonucleotide was assessed by viable count anaJysis relying on passive uptake, cold shocking techniques, chlorpromazine-mediated uptake, and, cationic and anionic lipid-aided uptake. All oligonucleotides were assessed for their ability to enhance uptake, which is a major barrier to the effectiveness of these agents. Compound 6 under cold shocking conditions produced the greatest consistent decline in colony forming units per ml. Results for this compound were sometimes variable indicating inconsistent uptake by this particular assay method.

A relaxation method of an alternating iterative algorithm for the Cauchy problem in linear isotropic elasticity

We propose two algorithms involving the relaxation of either the given Dirichlet data (boundary displacements) or the prescribed Neumann data (boundary tractions) on the over-specified boundary in the case of the alternating iterative algorithm of Kozlov et al. [16] applied to Cauchy problems in linear elasticity. A convergence proof of these relaxation methods is given, along with a stopping criterion. The numerical results obtained using these procedures, in conjunction with the boundary element method (BEM), show the numerical stability, convergence, consistency and computational efficiency of the proposed method.

Recovering boundary data in planar heat conduction using boundary integral equation method

We consider a Cauchy problem for the heat equation, where the temperature field is to be reconstructed from the temperature and heat flux given on a part of the boundary of the solution domain. We employ a Landweber type method proposed in [2], where a sequence of mixed well-posed problems are solved at each iteration step to obtain a stable approximation to the original Cauchy problem. We develop an efficient boundary integral equation method for the numerical solution of these mixed problems, based on the method of Rothe. Numerical examples are presented both with exact and noisy data, showing the efficiency and stability of the proposed procedure and approximations.