Studies of MOCVD for high Tc thin films

In this article we report on results obtained from studies of the effect of total pressure and carrier gas flow rate on the rate of precursor evaporation for typical precursors used in the MOCVD of high temperature superconductors (HTS). We find that this process is under significant mass transfer control and we consider the implications of this for growth of HTS. In particular, we discuss the problems associated with the use of solid precursors and possible strategies for solving the difficulties.     

XPS Analysis of Submicrometer Barium Titanate Powder

A commercial submicrometer BaTiO₃ powder was analyzed using X-ray photoelectron spectroscopy. The analysis revealed the powder surfaces to be covered with a layer of physisorbed H₂O and chemisorbed –OH ions. A BaCO₃ residual not detected with XPS was shown to be present in the powder using X-ray diffraction, suggesting that the carbonate takes the form of discrete particles rather than of a continuous surface layer. A relaxed surface phase detected in previous XPS analyses of bulk BaTiO₃ was also shown to be present. Depth profiling revealed the powder surfaces to be Ti-rich, confirming the presence of a phase, or phases, to stoichiometrically balance the barium carbonate.     

Small-angle neutron scattering from polymer solutions: 2. The semi-concentrated region near the upper critical solution temperature

Small-angle neutron scattering experiments have been made on solutions of polystyrene in cyclohexane. From these experiments the radius of gyration has been determined as a function of polymer concentration at a fixed temperature (60°C). Additionally, the screening length has been determined as a function of temperature for a fixed polymer concentration of 36% (w/v). The results support the notion of an additional region of solution behaviour, the semi-concentrated region, predicted by mean field-type theory.     

Simple parameter extraction method for illuminated solar cells

This paper presents a simple and successful method for evaluating the series resistance, the ideality factor, the saturation current and the shunt conductance in illuminated solar cells. The approach involves the use of an auxiliary function and a computer-fitting routine. The validity of this method has been confirmed by the way of current–voltage measurements of a commercial silicon solar cell, a module and a plastic solar cell.     

Artificial cell containing superoxide dismutase--selection of folding aids for stabilisation of SOD

Superoxide dismutase (abbreviated as SOD) has been vigorously studied in the fields of radical chemistry and related life science. One of practical problems is how to keep its activity in certain adverse conditions causing denaturation. Artificial cell containing SOD can be prepared by polymer encapsulation or nanocapsulation which has been found to be effective to improve the stability of SOD. For construction of an ideal artificial cell system, some folding aids or aggregation inhibitors were utilised to enhance SOD stability. In this study, three groups of biopolymers are selected as folding aids or aggregation inhibitors for stabilisation of SOD, i.e. albumin, carbohydrates and glycoproteins. Results indicate that the thermostability of SOD is affected by different sort of albumin while some carbohydrates such as cyclodextrins are found to be able to enhance SOD stability. In addition, it is firstly found that selected glycoproteins such as alpha-macroglobulin and ovalbumin are several types of effective folding aids for stabilisation of SOD. They can protect SOD against denaturation even at very high temperature(over 100 degrees C). The stability was tested by the measurement of SOD activity loss using autooxidation method in different adverse conditions such as high temperature, extreme pH medium, proteolytic hydrolysis and long shelf life storage. The possible stabilisation mechanism of using cyclodextrins and glycoproteins as folding aids were discussed.     

Hardness,indentation fracture toughness and compositional formula of X-phase sialon

The hardness and indentation fracture toughness,K _IC of sintered X-phase sialon, produced by simultaneous carbothermal reduction and nitriding of kaolinitic clays, are determined. By comparing the values obtained for the sialon with those for a commercially pure mullite, it is suggested that X-phase sialon is a material with potential for similar applications to those in which mullite is currently used. On the basis of the oxygen/nitrogen ratios of the sialon determined by the inert gas fusion method, the analysis of the energy of the dispersed X-rays (EDAX) from thinned samples in the transmission electron microscope (TEM) and the aluminium/silicon ratios, also determined by the TEM EDAX method, a modified compositional formula is proposed for X-phase.     

Evaluating inheritance depth on the maintainability of object-oriented software

This empirical research was undertaken as part of a multi-method programme of research to investigate unsupported claims made of object-oriented technology. A series of subject-based laboratory experiments, including an internal replication, tested the effect of inheritance depth on the maintainability of object-oriented software. Subjects were timed performing identical maintenance tasks on object-oriented software with a hierarchy of three levels of inheritance depth and equivalent object-based software with no inheritance. This was then replicated with more experienced subjects. In a second experiment of similar design, subjects were timed performing identical maintenance tasks on object-oriented software with a hierarchy of five levels of inheritance depth and the equivalent object-based software.The collected data showed that subjects maintaining object-oriented software with three levels of inheritance depth performed the maintenance tasks significantly quicker than those maintaining equivalent object-based software with no inheritance. In contrast, subjects maintaining the object-oriented software with five levels of inheritance depth took longer, on average, than the subjects maintaining the equivalent object-based software (although statistical significance was not obtained). Subjects' source code solutions and debriefing questionnaires provided some evidence suggesting subjects began to experience difficulties with the deeper inheritance hierarchy.It is not at all obvious that object-oriented software is going to be more maintainable in the long run. These findings are sufficiently important that attempts to verify the results should be made by independent researchers.