Synthesis and characterisation of carboxylic acid and diphenylphosphine derivatives in the 1,3-diyne series: Spectral properties of polydiacetylene carboxylates

Symmetrically substituted 1,3-diynes containing hydroxyalkyl ( 1a-d ), bromoalkyl ( 1e-h ) (diphenylphosphinyl) ( 1i-k ) and carboxyalkyl ( 2a-d ) substituents have been prepared and characterised; the phosphine derivative ( 1k ) has been converted with alkyl iodides ( RI ; R = Me, Et) into bis(phosphonium) salts ( 1l and m ). During preparation of the diynedioic acid. ( 2a ), the non-centrosymmetrical diyne, HO₂CCH₂C?C—C?C(CH₂)₂OH ( 3 ), was also isolated. ⁶⁰Co γ-Irradiation of diacetylene monomers ( 2a – d ) and 10,12-tricosadiyn-1-oic acid gave the corresponding polydiacetylene derivatives ( 4a – d and 5 ), respectively. Rubidium salts of ( 4c ) and ( 4d ), a barium salt of ( 4c ), and a potassium salt of ( 5 ) were prepared and isolated; soluble potassium salts of the carboxylic acid polymers ( 4 ) were generated in aqueous solution. The effects of changes in pH on the UV/visible absorption spectra of aqueous solutions of selected carboxylic acid polydiacetylenes have been recorded, and are discussed.     

Reaction steady states and stationary states in modelling semi-batch enzyme hydrolysis

Dimensionless material balance equations describing an uninhibited enzyme hydrolysis process in a semi-batch reactor (i.e. fed-batch reactor) are formulated; numerical solution of these equations provided concentration profiles of the enzyme-substrate complex by using published kinetic parameters. The unrestricted values obtained are compared with estimates based separately on the reaction steady state and stationary state assumptions. Results are discussed in terms of the enzyme/substrate inventory used and it is found that the reaction steady state is a satisfactory approximation only when this ratio is sufficiently small. The stationary state may be a better approximation at other values, particularly when enzyme is added to substrate or when an empty tank is being filled. Reaction yields from semi-batch and batch operations are compared. Processing takes longer in the semi-batch operations and complete conversions are only practical in this mode when enzyme is added to substrate.     

Ripple evaluation of high-performance synchronous reluctancemachines

In this article, synchronous reluctance motors with multiple-segment rotor structures are considered. The presence of stator slots is taken into account, with respect to torque ripple. An analytical model is presented, based on magnetic interaction between the d and q axes, due to stator toothing. The effect of skewing is also considered, showing its partial effect on torque ripple reduction, due to the rotor anisotropy. A closed expression for the torque is obtained, giving the torque ripple as a function of design parameters. Experimental verification of the proposed model is given, from measurements on prototype motors     

Compatibilizing PPE and PA6 with nitro-phthalimide derivatives

Compatibilization of poly(2,6-dimethyl (PPE) with 1,4 phenylene-ether) PA6 has been achieved in two steps: first, (PPE) was functionalized with N-methyl-4-nitro-phthalimide; then, functionalized PPE was allowed to react, by melt blending, with the amine end group of PA6, giving a trans-imidation product. The reaction path was followed by torque measurements in a Brabender apparatus and the products characterized by infrared (i.r.) and nuclear magnetic resonance (NMR) spectroscopy. The above PPE/PA6 blends, modified with a suitable rubbery component (Kraton G), showed a remarkable Izod impact strength value, compared to the uncompatibilized mixture (170 versus 30 Jm^–1). The maximum impact values were obtained with 1.65% functionalized PPE.     

Optical properties and laser performance of neodymium doped fluoroapatites SrxCa5−x(PO4)3F (x = 0, 1, 2, 3, 4, and 5)

Nd doped fluoroapatites Sr_xCa_5−x(PO₄)₃F(S_xC_5−xPF, X = 0, 1, 2, 3, 4, and 5) single crystals have been grown by the Czochralski technique. Their polarized absorption and emission spectra have been recorded at room temperature and used to calculate the absorption and stimulated emission cross sections. Broadening of the absorption and emission bands is observed for Nd³⁺ in the solid solutions SPF-CPF compared to Nd³⁺ in CPF or SPF. 1% Nd:S_xC_5−xPF, X = 0, 2, 3, 4, and 5, laser rods have been tested in a cavity longitudinally pumped by a 1 W AlGaAs laser diode and compared to Nd:YAG and Nd:YVO₄ rods. All fluoroapatites exhibit very good laser performance with low thresholds and high slope efficiencies, higher than in the case of YAG and equal to the YVO₄ samples. The dependance of the laser output power versus the diode temperature has also been measured for all materials. The laser output was found to be as sensitive to the diode temperature fluctuations for fluoroapatites as for YAG.     

Development of Anticandidal Delivery Systems: (I) Anticandidal Activities of Antifungal Agents and Synergistic Combination with Other Drugs

Susceptibility testing with antifungal agents, e. g., minimum inhibitory concentration (MIC) determination, is performed to obtain reliable data that permit selection of the most suitable agents for treatment of an infective condition. To determine the drugs that provide maximum effectiveness against oral candidiasis, the MICs of various antifungal agents were determined. Also, synergism between two chosen antifungal agents was evaluated, and the effect of benzocaine, an anesthetic, and hydrocortisone, an antiinflammatory agent, on their MICs was examined. It was observed that among all the drugs tested, clotrimazole was the most promising candidate for use as an oral local antifungal. The combination of clotrimazole and chlorhexidine resulted in a decrease in the MIC. While the addition of hydrocortisone to this combination resulted in a slight increase in the MIC, the inclusion of benzocaine resulted in a substantial decrease in the MIC of the antifungal agent combination.     

Characterization of titanium alloy implant surfaces with improved dissolution resistance

The present work sets out to investigate the structure and chemistry of surface treated oxides (either aged in boiling water or air-heated) with improved dissolution resistance compared to conventionally passivated surfaces. X-ray photoelectron spectroscopy (XPS) has demonstrated a significant reduction in oxidized aluminium associated with an ageing-based surface treatment. Angle-dependent XPS has revealed an increase in amphoteric-OH surface sites for the thermal treatments. Atomic force microscopy (AFM) investigation suggests that these sites play a role in the improved proteinadsorption properties of these surfaces. These observations form the basis of a model which describes the influence of surface oxide on the kinetics of metal ion dissolution.     

D-KAT: a deep knowledge acquisition tool

Abstract: This paper describes a system of shallow and deep knowledge acquisition and representation for diagnostic expert systems. The acquisition system is integrated into a diagnostic expert system shell. Shallow knowledge is represented in a failure model as a set of cause-effect relations among the possible faults, while deep knowledge is represented in three deep models: a functional, a deep causal and a taxonomic model. The acquisition and the representation of all the models are fully integrated. The deep knowledge is used by the final expert system in order to provide the user with deep explanations of the cause-effect relations of the failure model.     

INSTRUMENTATION FOR FLOW PROPERTIES OF GAS-SOLID SUSPENSIONS AND RECENT ADVANCES

Measurements of local velocity, density, and mass flow of phases of a gas-solid suspension are needed in determining transport properties, validating theoretical predictions, and formulating design procedures. Most of the available instruments are based on time averages or fluctuations with time. Primary standard for direct measurement of density of a phase such as solid particles is being developed. A laser phase Doppler device, within certain restrictions, may give local instantaneous density, while other optical methods and neutron beam remain secondary standards based on mass flow calibrations. An overall review including recent results has been made on both intrusive and non-intrusive instruments; their limitations and future possibilities are outlined and discussed. The limitations of the traditional approach utilizing the triangular relation between local averages of mass flow, velocity, and density of particles for the determination of flow properties, and higher order correlations are demonstrated.