19 resultados para solution studies
em Aston University Research Archive
Resumo:
With rapid increases in student fees reflecting moves towards a QUASI Market model of Higher Education in the UK and across much of the Western World[1], many universities find themselves having to meet progressively higher levels of student expectations[2]. This is particularly the case at undergraduate level, where increases in fees over the past decade have far exceeded inflation. Yet with so much attention on ‘consumer savvy’ undergraduates, the question of whether Master’s level students’ expectations are matched by their experiences is one which remains largely unanswered. Grounded in an empirically grounded approach to learning and teaching developed by the paper authors[3], this paper sets out to being to answer this question. In doing so it makes a distinctive contribution to debates about graduate level engineering education and concludes with a number of recommendations. Discussion: The ‘MSc: Managing Expectations’ Project analyses the expectations and experiences of Graduate level Engineering Management Students over a two year period. Focusingon the ‘student experience’, three main concepts are identified as being particular relevant to enhancing learning [3]: Relationships: Variety: Synergy. Relationships: Based on empirical research, the significance of Relationships within the academic environment is discussed with particular attention being paid to the value of students’ social and academic support networks, including academic tutoring. Variety: Grounded in a statistical analysis of ‘engagement data’ together with survey and interview findings, the concept of variety critically examines students’ perspectives and experiencesof different approaches to learning and teaching. Synergy: Possibly the most important concept discussed within this paper, the need for constructively aligned curriculum is extended to reflect the students’ apriori knowledge and experienceas well as employer and societal demands and expectations. The conclusion brings the different concepts within the discussion together, providing a set of practical recommendations for colleagues working both at graduate and undergraduate level. References 1.Gibbs, P. (2001) "Higher education as a market: a problem or solution?." Studies in Higher Education 26. 1. pp. 85-94. 2.Tricker, T., (2005) Student Expectations-How do we measure up. University of Sheffield. Available from: http://www.persons.org.uk/tricker%20paper.pdf Accessed 9/10/14 3.Clark, R. & Andrews, J. (2014). Relationships, Variety & Synergy [RVS]: The Vital Ingredients for Scholarship in Engineering Education? A Case-Study. European Journal of Engineering Education. 39.6. pp. 585-600.
Resumo:
The effects of adding bromoform (CHBr3) as a potential chain transfer agent in the photopolymerisation of acrylamide (AM) in aqueous solution have been studied both in terms of influencing the rate of polymerisation and the molecular weight of the polyacrylamide (PAM) formed. Using 4,4′-azo-bis(4-cyanopentanoic acid) (ACPA) as photoinitiator, two different CHBr3 concentrations as chain transfer agent were compared: 0.5 and 2.0 mol % (relative to AM), the higher of which was determined by the limit of CHBr3 water solubility. The results showed that CHBr3 was an effective chain transfer agent that could regulate the molecular weight of the PAM formed without seriously affecting the polymerisation rate. It is concluded that chain transfer to CHBr3occurs by both Br and H atom transfer although Br transfer is the more favoured due to the weaker C-Br bond. Furthermore, Br transfer leads to Br-terminated chains in which the terminal C-Br bond can re-dissociate leading to re-initiation and re-propagation of the same chain, thereby maintaining the polymerisation rate. Continuing studies into how this mechanism can be exploited in order to synthesize water-soluble block copolymers of potential biomedical importance are currently in progress.
Resumo:
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.
Resumo:
Healthcare associated infections may arise from many sources, including patient?s own skin flora and the clinical environment, and inflict a significant burden within the health service. Adequate and effective skin antisepsis and surface disinfection are therefore essential factors in infection control. Current EPIC guidelines recommend 2 % chlorhexidine (CHG) in 70 % isopropyl alcohol (IPA) for skin antisepsis however poor penetration has been reported. Eucalyptus oil (EO) is a known permeation enhancer, producing synergistic antimicrobial activity when combined with CHG. In this current study, the antimicrobial efficacy of EO and its main constituent 1,8-cineole were assessed against a panel of clinically relevant microorganisms, alone and in combination with CHG. The superior antimicrobial efficacy of EO compared with 1,8-cineole, and synergistic effects with CHG against planktonic and biofilm cultures, confirmed its suitability for use in subsequent studies within this thesis. Impregnation of EO, CHG and IPA onto prototype hard surface disinfectant wipes demonstrated significantly improved efficacy compared with CHG/IPA wipes, with clear reductions in the time required to eliminate biofilms. Optimisation of the EO/CHG/IPA formulation resulted in the development of Euclean® wipes, with simulated-use and time kill studies confirming their ability to remove microbial surface contamination, prevent cross contamination and eliminate biofilms within 10 minutes. The employment of isothermal calorimetry provided additional information on the type and rate of antimicrobial activity possessed by Euclean® wipes. A clinical audit of the Euclean® wipes at Birmingham Children?s Hospital, Birmingham, U.K. revealed divided staff opinion, with the highest cited advantage and disadvantage concerning the odour. Finally, skin penetration and cell toxicity studies of EO/CHG biopatches and Euclean® solution developed during this study, revealed no permeation into human skin following biopatch application, and no significant toxicity. These current studies enhance the knowledge regarding EO and its potential applications.
Resumo:
The thesis is divided into four chapters. They are: introduction, experimental, results and discussion about the free ligands and results and discussion about the complexes. The First Chapter, the introductory chapter, is a general introduction to the study of solid state reactions. The Second Chapter is devoted to the materials and experimental methods that have been used for carrying out tile experiments. TIle Third Chapter is concerned with the characterisations of free ligands (Picolinic acid, nicotinic acid, and isonicotinic acid) by using elemental analysis, IR spectra, X-ray diffraction, and mass spectra. Additionally, the thermal behaviour of free ligands in air has been studied by means of thermogravimetry (TG), derivative thermogravimetry (DTG), and differential scanning calorimetry (DSC) measurements. The behaviour of thermal decomposition of the three free ligands was not identical Finally, a computer program has been used for kinetic evaluation of non-isothermal differential scanning calorimetry data according to a composite and single heating rate methods in comparison with the methods due to Ozawa and Kissinger methods. The most probable reaction mechanism for the free ligands was the Avrami-Erofeev equation (A) that described the solid-state nucleation-growth mechanism. The activation parameters of the decomposition reaction for free ligands were calculated and the results of different methods of data analysis were compared and discussed. The Fourth Chapter, the final chapter, deals with the preparation of cobalt, nickel, and copper with mono-pyridine carboxylic acids in aqueous solution. The prepared complexes have been characterised by analyses, IR spectra, X-ray diffraction, magnetic moments, and electronic spectra. The stoichiometry of these compounds was ML2x(H20), (where M = metal ion, L = organic ligand and x = water molecule). The environments of cobalt, nickel, and copper nicotinates and the environments of cobalt and nickel picolinates were octahedral, whereas the environment of copper picolinate [Cu(PA)2] was tetragonal. However, the environments of cobalt, nickel, and copper isonicotinates were polymeric octahedral structures. The morphological changes that occurred throughout the decomposition were followed by SEM observation. TG, DTG, and DSC measurements have studied the thermal behaviour of the prepared complexes in air. During the degradation processes of the hydrated complexes, the crystallisation water molecules were lost in one or two steps. This was also followed by loss of organic ligands and the metal oxides remained. Comparison between the DTG temperatures of the first and second steps of the dehydration suggested that the water of crystallisation was more strongly bonded with anion in Ni(II) complexes than in the complexes of Co(II) and Cu(II). The intermediate products of decomposition were not identified. The most probable reaction mechanism for the prepared complexes was also Avrami-Erofeev equation (A) characteristic of solid-state nucleation-growth mechanism. The tempemture dependence of conductivity using direct current was determined for cobalt, nickel, Cl.nd copper isonicotinates. An activation energy (ΔΕ), the activation energy (ΔΕ ) were calculated.The ternperature and frequency dependence of conductivity, the frequency dependence of dielectric constant, and the dielectric loss for nickel isonicotinate were determined by using altemating current. The value of s paralneter and the value of'density of state [N(Ef)] were calculated. Keyword Thermal decomposition, kinetic, electrical conduclion, pyridine rnono~ carboxylic acid, cOlnplex, transition metal compJex.
Resumo:
Following a brief description of the atmosphere and ionosphere in Chapter I we describe how the equations of continuity and momentum for 0+, H+, He+, 0++ are derived from the formulations of St-Maurice and Schunk(1977) and Quegan et al.(1981) in Chapter II. In Chapter III we investigate the nature of the downward flow of protons in a collapsing post-sunset ionosphere. We derive an analytical form for the limiting temperature, we also note the importance of the polarization field term and concluded that the flow will remain subsonic for realistic conditions. The time-dependent behaviour of He+ under sunspot minimum conditions is investigated in Chapter IV. This is achieved by numerical solution of the 0+, H+ and,He+ continuity and momentum equations, treating He+ as a minor ion with 0+ , H+ as major ions. We found that He+ flows upwards during the day-time and downwards during the nighttime. He+ flux tube content reached a maximum on the 8th day of the integration period and started to decreasing. This is due to the large amount of H+ present at the late stages of the integration period which makes He+ unable to diffuse through the H+ layer away from the loss region. In Chapter V we investigate the behaviour of 0++ using sunspot maximum parameters. Although our results support the findings of Geis and Young (1981) that the large amounts of 0++ at the equator are caused mainly by thermal diffusion, the model used by Geis and Young overemphesizes the effect of thermal diffusion. The importance of 0++ - 0+ collision frequency is also noted. In Chapter VI we extend the work of Chapter IV, presenting a comparative study of H and He at sunspot minimum and sunspot maximum.In this last Chapter all three ions, O+ ,H+ and He+ , are treated theoretically as major ions and we concentrate mainly on light ion contents and fluxes. The results of this Chapter indicate that by assuming He+ as a minor ion we under-estimate He+ and over-estimate. H+. Some interesting features concerning the day to day behaviour of the light ion fluxes arise. In particular the day-time H+ fluxes decrease from day to day in contrast to the work of Murphy et al.(1976). In appendix.A we derive some analytical forms for the optical depth so that the models can include a realistic description of photoionization.
Resumo:
The investigations described in this thesis concern the molecular interactions between polar solute molecules and various aromatic compounds in solution. Three different physical methods were employed. Nuclear magnetic resonance (n.m.r.) spectroscopy was used to determine the nature and strength of the interactions and the geometry of the transient complexes formed. Cryoscopic studies were used to provide information on the stoichiometry of the complexes. Dielectric constant studies were conducted in an attempt to confirm and supplement the spectroscopic investigations. The systems studied were those between nitromethane, chloroform, acetonitrile (solutes) and various methyl substituted benzenes. In the n.m.r. work the dependence of the solute chemical shift upon the compositions of the solutions was determined. From this the equilibrium quotients (K) for the formation of each complex and the shift induced in the solute proton by the aromatic in the complex were evaluated. The thermodynamic parameters for the interactions were obtained from the determination of K at several temperatures. The stoichiometries of the complexes obtained from cryoscopic studies were found to agree with those deduced from spectroscopic investigations. For most systems it is suggested that only one type of complex, of 1:1 stiochiometry, predominates except that for the acetonitrile-benzene system a 1:2 complex is formed. Two sets of dielectric studies were conducted, the first to show that the nature of the interaction is dipole-induced dipole and the second to calculate K. The equilibrium quotients obtained from spectroscopic and dielectric studies are compared. Time-averaged geometries of the complexes are proposed. The orientation of solute, with respect to the aromatic for the 1:1 complexes, appears to be the one in which the solute lies symmetrically about the aromatic six-fold axis whereas for the 1:2 complex, a sandwich structure is proposed. It is suggested that the complexes are formed through a dipole-induced dipole interaction and steric factors play some part in the complex formation.
Resumo:
Current analytical assay methods for ampicillin sodium and cloxacillin sodium are discussed and compared, High Performance Liquid Chromatography (H.P.L.C.) being chosen as the most accurate, specific and precise. New H.P.L.C. methods for the analysis of benzathine cloxacillin; benzathine penicillin V; procaine penicillin injection B.P.; benethamine penicillin injection; fortified B.P.C.; benzathine penicillin injection; benzathine penicillin injection, fortified B.P.C.; benzathine penicillin suspnsion; ampicillin syrups and penicillin syrups are described. Mechanical or chemical damage to column packings is often associated with H.P.L.C. analysis. One type, that of channel formation, is investigated. The high linear velocity of solvent and solvent pulsing during the pumping cycle were found to be the cause of this damage. The applicability of nonisotherrnal kinetic experiments to penicillin V preparations, including formulated paediatric syrups, is evaluated. A new type of nonisotherrnal analysis, based on slope estimation and using a 64K Random Access Memory (R.A.M.) microcomputer is described. The name of the program written for this analysis is NONISO. The distribution of active penicillin in granules for reconstitution into ampicillin and penicillin V syrups, and its effect on the stability of the reconstituted products, are investigated. Changing the diluent used to reconstitue the syrups was found to affect the stability of the product. Dissolution and stability of benzathine cloxacillin at pH2, pH6 and pH9 is described, with proposed dissolution mechanisms and kinetic analysis to support these mechanisms. Benzathine and cloxacillin were found to react in solution at pH9, producing an insoluble amide.
Resumo:
This collection of papers records a series of studies, carried out over a period of some 50 years, on two aspects of river pollution control - the prevention of pollution by sewage biological filtration and the monitoring of river pollution by biological surveillance. The earlier studies were carried out to develop methods of controlling flies which bred in the filters and caused serious nuisance and possible public health hazard, when they dispersed to surrounding villages. Although the application of insecticides proved effective as an alleviate measure, because it resulted in only a temporary disturbance of the ecological balance, it was considered ecologically unsound as a long-term solution. Subsequent investigations showed that the fly populations in filters were largely determined by the amount of food available to the grazing larval stage in the form of filter film. It was also established that the winter deterioration in filter performance was due to the excessive accumulation of film. Subsequent investigations were therefore carried out to determine the factors responsible for the accumulation of film in different types of filter. Methods of filtration which were considered to control film accumulation by increasing the flushing action of the sewage, were found to control fungal film by creating nutrient limiting conditions. In some filters increasing the hydraulic flushing reduced the grazing fauna population in the surface layers and resulted in an increase in film. The results of these investigations were successfully applied in modifying filters and in the design of a Double Filtration process. These studies on biological filters lead to the conclusion that they should be designed and operated as ecological systems and not merely as hydraulic ones. Studies on the effects of sewage effluents on Birmingham streams confirmed the findings of earlier workers justifying their claim for using biological methods for detecting and assessing river pollution. Further ecological studies showed the sensitivity of benthic riffle communities to organic pollution. Using experimental channels and laboratory studies the different environmental conditions associated with organic pollution were investigated. The degree and duration of the oxygen depletion during the dark hours were found to be a critical factor. The relative tolerance of different taxa to other pollutants, such as ammonia, differed. Although colonisation samplers proved of value in sampling difficult sites, the invertebrate data generated were not suitable for processing as any of the commonly used biotic indexes. Several of the papers, which were written by request for presentation at conferences etc., presented the biological viewpoint on river pollution and water quality issues at the time and advocated the use of biological methods. The information and experiences gained in these investigations was used as the "domain expert" in the development of artificial intelligence systems for use in the biological surveillance of river water quality.
Resumo:
A textural and microstructural study of a variety of zinc sulfide-containing ores has been undertaken, and the possible depositional and deformational controls of textural and microstructural development considered. Samples for the study were taken from both deformed and undeformed zinc ores of the Central U.S. Appalachians, and deformed zinc ores of the English Pennines. A variety of mineralogical techniques were employed, including transmitted and reflected light microscopy of etched and unetched material, transmission electron microscopy and electron microprobe analysis. For the Pennine zinc sulfides, spectroscopic, x-ray diffraction and fluid inclusion studies were also undertaken. Optical and electron optical examination of the Appalachian material confirmed the suitability of zinc sulfide for detailed study with such techniques. Growth and deformation-related microstructures could be distinguished from specimen-preparation induced artifacts. A deformationally-mduced lamelliform optical anisotropy is seen to be developed in areas hosting a dense planar microstructure of {111} twin- and slip-planes. The Pennine zinc sulfide texturally records a changing depositional environment. Thus, for example, delicately growth- zoned crystals are truncated and cross-cut by solution disconformities. Fluid inclusion studies indicate a highly saline (20-25 wt. % equiv. NaCl), low temperature (100-150°C.) fluid. Texturally, two varieties of zinc sulfide can be recognised; a widely developed, iron- banded variety, and a paragenetically early variety, banded due to horizons rich in crystal defects and microscopic inclusions. The zinc sulfide takes the form of a disordered 3C-polytype, with much of the disorder being deformational in origin. Twin- and slip-plane fabrics are developed . A deformation-related optical anisotropy is seen to overprint growth-related anisotropy, along with cuprian alteration of certain {111} deformation planes.
Resumo:
Current evidence-based guidelines recommend that 2% (w/v) chlorhexidine digluconate (CHG), preferentially in 70% (v/v) isopropyl alcohol (IIPA), is used for skin antisepsis prior to incision of the skin. In this current study, the antimicrobial efficacy of CHG, six essential oils [tea tree oil (TTO), thymol, eucalyptus oil (EO), juniper oil, lavender oil and citronella] and novel benzylidenecarboxamidrazone and thiosemicarbazone compounds were determined against a panel of microorganisms commonly associated with skin infection (Staphylococcus epidermidis, S. aureus, meticillin-resistant S. aureus, Propionibacterium acnes, Acinetobacter spp., Pseudomonas aeruginosa and Candida albicans) The results demonstrated synergistic activity of CHG in combination with EO against biofilm cultures of S. epidermidis, with significantly reduced concentrations of CHG and EO required to inhibit biofilm growth compared to CHG or EO alone. Skin permeation of CHG was subsequently investigated using an in vitro human skin model (Franz cell) and the penetration profile was determined by serial sectioning of the full thickness human skin. Two percent (w/v) CHG in aqueous solution and in 70% (v/v) IPA demonstrated poor skin permeation; however, the skin permeation was significantly enhanced in combination with 5% - 50% (v/v) EO. Detectable levels of CHG did not permeate through full thickness skin in 24 h. Skin permeation of 2% (w/v) CHG in 70% (v/v) IPA in the presence of 10% (v/v) EO was subsequently studied. The results demonstrated a significantly enhanced skin penetration of CHG after a 2 min application, with CHG detected at significant levels to a depth of 600 m with CHG in combination with EO and IPA compared to 100 m with IPA alone. Combination antisepsis comprising CHG and EO may be beneficial for skin antisepsis prior to invasive procedures to reduce the number of microorganisms on and within the skin due to enhanced skin penetration of CHG and improved efficacy against S. epidermidis in a biofilm mode of growth.
Resumo:
SQUID magnetometry, normally used to characterise the properties of solids, was used to follow a clock reaction in solution, namely the auto-catalytic oxidation of [Co(ii)EDTA] by HO, in real time and it was shown that, in combination with other methods (e.g., magnetic resonance proton relaxation studies and UV-vis absorption analysis), SQUID magnetometry can be a powerful method in elucidating and interpreting the time-profile of chemical reactions so as long as reactants, intermediates and products have suitably large differences in their respective magnetic susceptibilities. © 2009 The Royal Society of Chemistry.
Resumo:
A new bridge technique for the measurement of the dielectric absorption of liquids and solutions at microwave frequencies has been described and its accuracy assessed. 'l'he dielectric data of the systems studied is discussed in terms of the relaxation processes contributing to the dielectric absorption and the apparent dipole moments. Pyridine, thiophen and furan in solution have a distribution of relaxation times which may be attributed to the small size of the solute molecules relative to the solvent. Larger rigid molecules in solution were characterized by a single relaxation time as would be anticipated from theory. The dielectric data of toluene, ethyl-, isopropyl- and t-butylbenzene as pure liquids and in solution were described by two relaxation times, one identified with molecular re-orientation and a shorter relaxation time.· The subsequent work was investigation of the possible explanations of this short relaxation process. Comparable short relaxation times were obtained from the analysis of the dielectric data of solutions of p-chloro- and p-bromotoluene below 40°C, o- and m-xylene at 25°C and 1-methyl- and 2 methylnaphthalene at 50 C. Rigid molecules of similar shapes and sizes were characterized by a single relaxation time identified with molecular re-orientation. Contributions from a long relaxation process attributed to dipolar origins were reported for solutions of nitrobenzene, benzonitrile and p-nitrotoluene. A short relaxation process of possible dipolar origins contributed to the dielectric absorption of 4-methyl- and 4-t-butylpyridine in cyclohexane at 25°C. It was concluded that the most plausible explanation of the short relaxation process of the alkyl-aryl hydrocarbons studied appears to be intramolecular relaxation about the alkyl-aryl bond. Finally the mean relaxation times of some phenylsubstituted compounds were investigated to evaluate any shortening due to contributions from the process of relaxation about the phenyl-central atom bond. The relaxation times of triphenylsilane and phenyltrimethylsilane were significantly short.