Facile synthesis of poly(3-hexylthiophene)-block-poly(ethylene oxide) copolymers via Steglich esterification

Poly(ethylene oxide) has been coupled to poly(3-hexylthiophene) using esterification to produce pure diblock copolymers, highly relevant for use in organic electronic devices. The new synthetic route described herein uses a metal-free coupling step, for the first time, to afford well-defined polymers in high yields following facile purification.

Studies on the thermal decomposition behaviour, kinetics and electrical conductivity of the non-isothermal decomposition of pyridine mono carboxylic acids and some of their transition metal complexes

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.

Fatigue crack growth behaviour in molten-metal processed SiC particle-reinforced aluminium alloys

Fatigue crack initiation and subsequent short crack growth behaviour of 2014-5wt%SiC aluminium alloy composites has been examined in 4-point bend loading using smooth bar specimens. The growth rates of long fatigue cracks have also been measured at different stress ratios using pre-cracked specimens. The distributions of SiC particles and of coarse constituent particles in the matrix (which arise as a result of the molten-metal processing and relatively slow cooling rate) have been investigated. Preferential crack initiation sites were found to be SiC-matrix interfaces, SiC particles associated with constituent particles and the coarse constituent particles themselves. For microstructurally short cracks the dispersed SiC particles also act as temporary crack arresters. In the long crack growth tests, higher fatigue crack growth rates were obtained than for monolithic alloys. This effect is attributed to the contribution of void formation, due to the decohesion of SiC particles, to the fatigue crack growth process in the composite. Above crack depths of about 200 μm 'short' crack growth rates were in good agreement with the long crack data, showing a Pris exponent, m = 4 in both cases. For the long crack and short crack growth tests little effect of specimen orientation and grain size was observed on fatigue crack growth rates, but, specimen orientation affected the toughness. No effect of stress ratio in the range R = 0.2-0.5 was seen for long crack data in the Paris region.

In situ growth strategy for highly efficient Ag2CO3/g-C3N4 hetero/nanojunctions with enhanced photocatalytic activity under sunlight irradiation

Developing novel heterojunction photocatalysts is a powerful strategy for improving the separation efficiency of photogenerated charge carriers, which is attracting the intense research interest in photocatalysis. Herein we report a highly efficient hetero/nanojunction consisting of Ag2CO3 nanoparticles grown on layered g-C3N4 nanosheets synthesized via a facile and template free in situ precipitation method. The UV–vis diffuse reflectance studies revealed that the synthesized Ag2CO3/g-C3N4 hetero/nanojunctions exhibit a broader and stronger light absorption in the visible light region, which is highly beneficial for absorbing the visible light in the solar spectrum. The optimum photocatalytic activity of Ag2CO3/g-C3N4 at a weight content of 10% Ag2CO3 for the degradation of Rhodamine B was almost 5.5 and 4 times as high as that of the pure Ag2CO3 and g-C3N4, respectively. The enhanced photocatalytic activity of the Ag2CO3/g-C3N4 hetero/nanojunctions is due to synergistic effects including the strong visible light absorption, large specific surface area, and high charge transfer and separation efficiency. More importantly, the high photostability and low use of the noble metal silver which reduces the cost of the material. Therefore, the synthesized Ag2CO3/g-C3N4 hetero/nanojunction photocatalyst is a promising candidate for energy storage and environment protection applications.

Development and growth of the lichen Rhizocarpon geographicum

The development of new areolae on the marginal hypothallus of the lichen Rhizocarpon geographicum (L.) DC was studied after complete or partial removal of the central areolae. New areolae developed slowly on the isolated hypothalli over two years. Development was similar when the areolae were completely removed and when the central areolae were separated from the marginal hypothallus by ‘moats’ 2 to 5 mm in width. However, in intact thalli, the marginal areolae developed rapidly during Jan. – June 1986 but showed periods of retreat from the margin during Oct. - Dec. 1985 and July – Sept. 1986. These results suggested that primary areolae may develop from free-living algal cells trapped by the hypothallus while secondary areolae may develop from zoospores produced by the thallus. Complete removal of the areolae resulted in no measurable radial growth of the marginal hypothallus over 18 months. Removal of the central areolae to within 1 and 2 mm of the hypothallus significantly reduced growth. These results suggest that the areolae may supply the hypothallus with carbon for growth. When the marginal hypothallus was experimentally removed a new hypothallus developed within one year. Regeneration occurred initially by retreat of the marginal areolae and later by new hyphal growth. The concentration of ribitol, arabitol and mannitol was measured in the areolae and marginal hypothallus on four occasions in 1985/6 in a population growing on a steep south facing rock surface. The three carbohydrates were present in significantly higher concentration in the areolae than in the hypothallus. Hence, the slow growth of this species may result from inhibited transport of carbohydrate from areolae to hypothallus.

The role of oxidation in the protection of sliding metal surfaces

This study is concerned with the mechanisms of growth and wear of protective oxide films formed under various tribological conditions. In the study three different tribological systems are examined in each of which oxidational wear is the dominant equilibrium mode. These are an unlubricated steel on steel system sliding at low and elevated temperatures, a boundary lubricated aluminium bronze on steel system and an unlubricated reciprocating sliding 9% Cr steel system operated at elevated temperature, in an atmosphere of carbon dioxide. The results of mechanical measurements of wear and friction are presented for a range of conditions of load, speed and temper.ature for the systems, together with the results of extensive examinations of the surfaces and sub­ surfaces by various physical methods of analysis. The major part of the thesis, however, is devoted to the development and application of surface models and theoretical quantative expressions in order to explain the observed oxidational wear phenomena. In this work, the mechanisms of formation of load bearing ox ide plateaux are described and are found to be dependent on system geometry and environment. The relative importance of ''in contact" and "out of contact" oxidation is identified together with growth rate constants appropriate to the two situations. Hypotheses are presented to explain the mechanisms of removal of plateaux to form wear debris. The latter hypotheses include the effects of cyclic stressing and dislocation accumulation, together with effects associated with the kinetics of growth and physical properties of the various oxides. The proposed surf ace mode1s have led to the develop­ ment of quantitative expressions for contact temperature, unlubricated wear rates, boundary lubricated wear rates and the wear of rna ter ial during the transition from severe to mild wear. In general theoretical predictions from these expressions are in very good agreement with experimental values.

Organotellurium compounds for metal organic vapour phase epitaxy

The infra-red detector material cadmium mercury telluride can be grown by the technique of Metal Organic Vapour Phase Epitaxy using simple alkyl telluride compounds as the source of tellurium. New tellurium precursors are required in order to overcome handling and toxicity problems and to reduce the growth temperature in preparing the material. A range of diaryltellurium(IV) dicarboxylates and some 2-(2'-pyridyl)phenyl-tellurium(II) and tellurium(IV) monocarboxylates have been synthesised and characterised by infra-red, 13C N.M.R. and mass spectroscopy. Infra-red spectroscopy has been used to determine the mode of bonding of the carboxylate ligand to tellurium. Synthetic methods have been devised for the preparation of diorganotritellurides (R2Te3) and mixed diorganotetrachalcogenides (RTeSeSeTeR). A mechanism for the formation of the tritellurides based on aerobic conditions is proposed. The reaction of ArTe- with (ClCH2CH2)3N leads to tripod-like multidentate ligands (ArTeCH2CH2)3N which form complexes with the ions Hg(II), Cd(II), Cu(I), Pt(II) and Pd(II). Synthetic routes to aryltelluroalkylamines and arylselenoalkylamines are also reported. The crystal structure of 2-(2'-pyridyl)phenyltellurium(II) bromide has been solved in which there are six molecules present within the unit cell. There are no close intermolecular Te---Te interactions and the molecules are stabilised by short Te---N intramolecular contacts. The crystal structure of 2-(2'-pyridyl)phenylselenium(II)-tribromomercurate(II) is also presented. A study of the Raman vibrational spectra of some tellurated azobenzenes and 2-phenylpyridines shows spectra of remarkably far superior quality to those obtained using infra-red spectroscopy.

Growth of crustose lichens: a review

Crustose species are the slowest growing of all lichens. Their slow growth and longevity, especially of the yellow-green Rhizocarpon group, has made them important for surface-exposure dating (‘lichenometry’). This review considers various aspects of the growth of crustose lichens revealed by direct measurement including: 1) early growth and development, 2) radial growth rates (RGR, mm yr-1), 3) the growth rate-size curve, and 4) the influence of environmental factors. Many crustose species comprise discrete areolae that contain the algal partner growing on the surface of a non-lichenised fungal hypothallus. Recent data suggest that ‘primary’ areolae may develop from free-living algal cells on the substratum while ‘secondary’ areolae develop from zoospores produced within the thallus. In more extreme environments, the RGR of crustose species may be exceptionally slow but considerably faster rates of growth have been recorded under more favourable conditions. The growth curves of crustose lichens with a marginal hypothallus may differ from the ‘asymptotic’ type of curve recorded in foliose and placodioid species and the latter are characterized by a phase of increasing RGR to a maximum and may be followed by a phase of decreasing growth. The decline in RGR in larger thalli may be attributable to a reduction in the efficiency of translocation of carbohydrate to the thallus margin or to an increased allocation of carbon to support mature ‘reproductive’ areolae. Crustose species have a low RGR accompanied by a low demand for nutrients and an increased allocation of carbon for stress resistance; therefore enabling colonization of more extreme environments.

Factors affecting the growth of Cladophora in relation to river pollution

Nuisance growths of Cladophora have been associated with eutrophication. A review of the literature, however, reveals a scarcity of relevant experimental growth studies. Sampling experimental streams reveals that the addition of sewage effluent to good quality water alters the flora from that dominated by Potamogetan crispus to one dominated by CLadophora. Spatial and temporal differences in biomass of taxa present are discussed in the context of accompanying physicochemical data. In laboratory batch culture, growth of unialgal C. glomerata was accompanied by elevation of medium pH - considered largely responsible for the poor growth in such culture. However, appropriate experimental conditions and indices of growth were selected and the effects of various herbicides assessed. Diquat and terbutryne were shown to possess algicidal activity towards Cladophora. A closed continuous culture apparatus was developed: growth proceeded through lag, logarithmic and linear phases. Inoculum size and medium flow rate had significant effects on growth, and were standardized. In continuous culture, specific growth rate increased linearly with increased duration of light per day, up to 24 hours, and increased light intensity, up to 6000 lux - the highest intensity tested. Comparison of field and laboratory results suggests that ammonia toxicity is attributable to the undissociated form. In the laboratory, 185 µg/1 undissociated ammoniacal nitrogen reduced specific growth rate to 50% of that at 10 µg/1 undissociated ammcniacal nitrogen. 0.077-1.057 mg/1 NO2-N had no significant effect on growth. 7.2-15.2 mg/1 NO3-N had no significant effect on specific growth rate. Neither was any nitrate/phosphate interaction significant. At 4.9 mg/1 PO4-1, specific growth rate was only 48% of that at 1.9 g/1 P04-P. The critical medium PO4-P concentration was <0.1 mg/i. Specific growth rate was reduced to 50% of that in natural water by 0.036 mgCu/l, 0.070 mgzn/1 and 1.03 mgPb/l. Metal uptake was evaluated.

Mechanical properties of sheet metal under forming conditions

In the bulge test, a sheet metal specimen is clamped over a circular hole in a die and formed into a bulge by the hydraulic pressure on one side of the specirnen. As the unsupported part of the specimen is deformed in this way, its area is increased, in other words, the material is generally stretched and its thickness generally decreased. The stresses causing this stretching action are the membrane stresses in the shell generated by the hydraulic pressure, in the same way as the rubber in a toy balloon is stretched by the membrane stresses caused by the air inside it. The bulge test is a widely used sheet metal test, to determine the "formability" of sheet materials. Research on this forming process (2)-(15)* has hitherto been almost exclusively confined to predicting the behaviour of the bulged specimen through the constitutive equations (stresses and strains in relation to displacements and shapes) and empirical work hardening characteristics of the material as determined in the tension test. In the present study the approach is reversed; the stresses and strains in the specimen are measured and determined from the geometry of the deformed shell. Thus, the bulge test can be used for determining the stress-strain relationship in the material under actual conditions in sheet metal forming processes. When sheet materials are formed by fluid pressure, the work-piece assumes an approximately spherical shape, The exact nature and magnitude of the deviation from the perfect sphere can be defined and measured by an index called prolateness. The distribution of prolateness throughout the workpiece at any particular stage of the forming process is of fundamental significance, because it determines the variation of the stress ratio on which the mode of deformation depends. It is found. that, before the process becomes unstable in sheet metal, the workpiece is exactly spherical only at the pole and at an annular ring. Between the pole and this annular ring the workpiece is more pointed than a sphere, and outside this ring, it is flatter than a sphere. In the forming of sheet materials, the stresses and hence the incremental strains, are closely related to the curvatures of the workpiece. This relationship between geometry and state of stress can be formulated quantitatively through prolateness. The determination of the magnitudes of prolateness, however, requires special techniques. The success of the experimental work is due to the technique of measuring the profile inclination of the meridional section very accurately. A travelling microscope, workshop protractor and surface plate are used for measurements of circumferential and meridional tangential strains. The curvatures can be calculated from geometry. If, however, the shape of the workpiece is expressed in terms of the current radial (r) and axial ( L) coordinates, it is very difficult to calculate the curvatures within an adequate degree of accuracy, owing to the double differentiation involved. In this project, a first differentiation is, in effect, by-passed by measuring the profile inclination directly and the second differentiation is performed in a round-about way, as explained in later chapters. The variations of the stresses in the workpiece thus observed have not, to the knowledge of the author, been reported experimentally. The static strength of shells to withstand fluid pressure and their buckling strength under concentrated loads, both depend on the distribution of the thickness. Thickness distribution can be controlled to a limited extent by changing the work hardening characteristics of the work material and by imposing constraints. A technique is provided in this thesis for determining accurately the stress distribution, on which the strains associated with thinning depend. Whether a problem of controlled thickness distribution is tackled by theory, or by experiments, or by both combined, the analysis in this thesis supplies the theoretical framework and some useful experimental techniques for the research applied to particular problems. The improvement of formability by allowing draw-in can also be analysed with the same theoretical and experimental techniques. Results on stress-strain relationships are usually represented by single stress-strain curves plotted either between one stress and one strain (as in the tension or compression tests) or between the effective stress and effective strain, as in tests on tubular specimens under combined tension, torsion and internal pressure. In this study, the triaxial stresses and strains are plotted simultaneously in triangular coordinates. Thus, both stress and strain are represented by vectors and the relationship between them by the relationship between two vector functions. From the results so obtained, conclusions are drawn on both the behaviour and the properties of the material in the bulge test. The stress ratios are generally equal to the strain-rate ratios (stress vectors collinear with incremental strain vectors) and the work-hardening characteristics, which apply only to the particular strain paths are deduced. Plastic instability of the material is generally considered to have been reached when the oil pressure has attained its maximum value so that further deformation occurs under a constant or lower pressure. It is found that the instability regime of deformation has already occurred long before the maximum pressure is attained. Thus, a new concept of instability is proposed, and for this criterion, instability can occur for any type of pressure growth curves.

The growth and awareness of health and safety at work, 1780-1900

This thesis examines the growth and awareness of health and safety at work between 1780 and 1900. In this period the hazards at work were increased by the intensification of production brought about by the Industrial Revolution, and new risks to health arose from the wider range of toxic substances in use by manufacturing industry. There is discussion in the thesis of the extent to which the problems were identified in an age of short life expectancy and limited medical knowledge. The sources studied have been largely medical, governmental, trade and press reports. The emphasis is on the first effects seen and recommendations made, and where possible, the extent of the problem and the effectiveness of any preventative measures adopted and examined. There is discussion of the growing involvement of the Government in industrial health and safety. The subject is viewed in the light of modern thinking on industrial health but uses a classification appropriate to historical resources. Psychological and minor afflictions, neglected in the 19th century, are not considered. The available literature is reviewed in each section. Three detailed case studies conclude the thesis, two on the notoriously dangerous occupations of metal grinding and pottery, and one on occupational eye injuries. Each study is based on a different type of source material. The thesis overall shows that there was extensive concern for health and safety at work, but no systematic approach and only ad hoc implementation of preventative measures; and that the rate at which conditions improved varied between different industries and different categories of workers . However, some modern principles of health and safety at work can be seen emerging, and the period laid the necessary medical, technical and legal foundations for developments in the present century.

Textural and microstructural studies of zinc sulfide and associated phases in certain base metal deposits

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.

Carbon monoxide expedites metabolic exhaustion to inhibit tumor growth

One classical feature of cancer cells is their metabolic acquisition of a highly glycolytic phenotype. Carbon monoxide (CO), one of the products of the cytoprotective molecule heme oxygenase-1 (HO-1) in cancer cells, has been implicated in carcinogenesis and therapeutic resistance. However, the functional contributions of CO and HO-1 to these processes are poorly defined. In human prostate cancers, we found that HO-1 was nuclear localized in malignant cells, with low enzymatic activity in moderately differentiated tumors correlating with relatively worse clinical outcomes. Exposure to CO sensitized prostate cancer cells but not normal cells to chemotherapy, with growth arrest and apoptosis induced in vivo in part throughmitotic catastrophe. CO targeted mitochondria activity in cancer cells as evidenced by higher oxygen consumption, free radical generation, and mitochondrial collapse. Collectively, our findings indicated that CO transiently induces an anti-Warburg effect by rapidly fueling cancer cell bioenergetics, ultimately resulting in metabolic exhaustion. ©2013 AACR.

Effect of thermal residual stresses on fatigue crack opening and propagation behavior in an Al/SiCp metal matrix composite

The effects of a thermal residual stress field on fatigue crack growth in a silicon carbide particle-reinforced aluminum alloy have been measured. Stress fields were introduced into plates of material by means of a quench from a solution heat-treatment temperature. Measurements using neutron diffraction have shown that this introduces an approximately parabolic stress field into the plates, varying from compressive at the surfaces to tensile in the center. Long fatigue cracks were grown in specimens cut from as-quenched plates and in specimens which were given a stress-relieving overaging heat treatment prior to testing. Crack closure levels for these cracks were determined as a function of the position of the crack tip in the residual stress field, and these are shown to differ between as-quenched and stress-relieved samples. By monitoring the compliance of the specimens during fatigue cycling, the degree to which the residual stresses close the crack has been evaluated. © 1995 The Minerals, Metals & Material Society.

Crack closure and residual stress effects in fatigue of a particle-reinforced metal matrix composite

A study of the influence of macroscopic quenching stresses on long fatigue crack growth in an aluminium alloy-SiC composite has been made. Direct comparison between quenched plate, where high residual stresses are present, and quenched and stretched plate, where they have been eliminated, has highlighted their rôle in crack closure. Despite similar strength levels and identical crack growth mechanisms, the stretched composite displays faster crack growth rates over the complete range of ΔK, measured at R = 0.1, with threshold being displaced to a lower nominal ΔK value. Closure levels are dependent upon crack length, but are greater in the unstretched composite, due to the effect of surface compressive stresses acting to close the crack tip. These result in lower values of ΔKeff in the unstretched material, explaining the slower crack growth rates. Effective ΔKth values are measured at 1.7 MPa√m, confirmed by constant Kmax testing. In the absence of residual stress, closure levels of approximately 2.5 MPa√m are measured and this is attributed to a roughness mechanism.