Structure−Activity Relationships of Cinnamate Ester Analogues as Potent Antiprotozoal Agents

Protozoal infections are still a global health problem, threatening the lives of millions of people around the world, mainly in impoverished tropical and sub-tropical regions. Thus, in view of the lack of efficient therapies and increasing resistances against existing drugs, this study describes the antiprotozoal potential of synthetic cinnamate ester analogues and their structure-activity relationships. In general, Leishmania donovani and Trypanosoma brucei were quite susceptible to the compounds in a structure-dependent manner. Detailed analysis revealed a key role of the substitution pattern on the aromatic ring and a marked effect of the side chain on the activity against these two parasites. The high antileishmanial potency and remarkable selectivity of the nitro-aromatic derivatives suggested them as promising candidates for further studies. On the other hand, the high in vitro potency of catechol-type compounds against T. brucei could not be extrapolated to an in vivo mouse model.     

Cure reaction for modified diallylbisphenol A/diaminodiphenylsulfone/bismaleimide

The glass‐transition temperature as a function of curing conversion for a modified diallylbisphenol A/diaminodiphenylsulfone/bismaleimide (BMI) resin was investigated at different temperature regimes and modeled using a modified Di Benedetto equation. Although the relationship between the glass‐transition temperature and conversion of the BMI system conforms to the Di Benedetto equation for α < 0.6 and at lower cure temperatures, at higher cure temperatures the results deviated significantly from the equation; thus, it was an inadequate model for the system. Fourier transform IR analysis showed that the major crosslinking reactions did not occur during cure for the modified BMI at and below 150°C. However, as the cure temperature was increased, the crosslinking reactions responsible for 3‐dimensional network structures became more dominant. At 190°C the C? N? C_stretch vibration of the uncured maleimide ring converted into succinimide rings in the curing process. Simultaneously, a decrease was observed for the absorbance bands of ? C? H_bending (maleimide). The higher cure temperatures induced a significantly faster initial crosslinking rate and also resulted in a shorter period of time after which further crosslinking was retarded, because the increase in the crosslinks also physically slowed further crosslinking activity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 227–235, 2002     

AI-Li/SiCp composites and Ti-AI alloy powders and coatings prepared by a plasma spray atomization (PSA) technique

There has been increasing use of Al-Li alloys in the aerospace industry, due mainly to the low density and high elastic modulus of this material. However, the problem of low ductility and fracture toughness of this material has limited its present application to only weight- and stiffness-critical components. Development of Al-Li/ceramic composites is currently being investigated to enhance the service capabilities of this material. The Ti-Al alloy is also of interest to aerospace-type applications, engine components in particular, due to its attractive high-temperature properties. Preparation of fine powders by plasma melting of composite feedstock and coatings formed by plasma spraying was carried out to examine the effect of spray parameters on the microstructure and properties of these materials. Characterization of the powders and coatings was performed using the scanning electron microscope and image analyzer. Examination of the plasma-sprayed powders and coatings has shown that in the Al-Li/SiC composite there is melting of both materials to form a single composite particle. The SiC reinforcement was in the submicron range and contributed to additional strengthening of the composite body, which was formed by a cold isostatic press and consolidated by hot extrusion or hot forging processes. The plasma-sprayed Ti-Al powder showed four categories of microstructures: featureless, dendritic, cellular, and martensite-like.     

Fractionation studies of palm oil by density gradient

The paper describes a method of fractionating vegetable, animal and fish oils, and in particular palm oil. The method involves addition of a medium comprising two common solvents to the semisolid oils. On centrifugation, the olein and stearin are separated by the medium in the middle. Thirteen media made up from binary combinations of nine solvents, viz. water, propylene glycol, glycerine, methanol, ethanol,n-propanol, isopropanol (IPA), acetone and butanone, are found to be effective in olein-stearin separation. However, only the water/IPA and water/methanol systems have been studied in detail. The aqueous IPA provides a higher yield of olein than water/ methanol but intersolubility between oil and medium is also greater. The fractionation process can be carried out at any suitable temperature. Fractionation of the special prime bleached (SPB) palm oil at 16 C yields an olein with a cloud point of 4.8 C. Some hybrid palm oils produce a large quantity of low cloud point olein which can be bleached readily. The process can be extended to include degumming and neutralization by using an alkaline medium for centrifugation. The olein fractions obtained have been found to be free of phosphatides and the free fatty acids reduced to as low as 0.02%. Metal-scavenging agents have also been added to the medium in an attempt to remove copper and iron. The development of this process into a continuous one has been demonstrated on the AlfaLaval LAPX 202 Separator. Fractionation of crude palm oil using a density gradient provides seven fractions of different characteristics. The iodine values vary from 37.5 to 57.4 and the unsaturated fatty acids range from 32.7% to 51.2%. Triglyceride analysis by carbon numbers shows great differences in the C₄₈ and C₅₂ constituents of the fractions. aThe volume ratio of oil to medium in each case was 1:1. The separation involved the oil and wax.     

Kinetic study of the curing behavior of bismaleimide modified with diallylbisphenol A

The curing kinetics of bismaleimide modified with diallylbisphenol A were investigated for different ratios of 1,1′‐(methylene di‐4,1‐phenylene) bismaleimide and diallylbisphenol A with differential scanning calorimetry. Multiheating‐rate and isothermal methods were used to study the kinetics of the curing process. The results indicated that the activation energy changed with the extent of conversion. The activation energy obtained by the multiheating‐rate method was higher than that obtained by the isothermal method. Two kinetic models (autocatalytic and nth‐order) were successfully used to model the curing process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2229–2240, 2003     

Glass‐transition temperature in the curing process of bismaleimide modified with diallylbisphenol A

The T_g‐conversion relationship, during the thermal curing of different stoichiometric formulations of 1,1′‐(methylene‐di‐4,1‐phenylene) bismaleimide (BMI), modified with o,o′‐diallyl bisphenol A (DABA), was investigated. The DiBenedetto equation was used to model this relationship for the formulation of DABA‐1 (BMI : DABA, 1 : 1). Based on this model, the T_g‐conversion relationship of formulation DABA‐0.5 (BMI : DABA, 1 : 0.5) was modeled. The high consistency between the model curve and experimental data showed that the change of T_g, attributed to copolymerization between BMI and DABA in DABA‐0.5, in the low‐conversion regime, was the same as that in DABA‐1. This also verifies that, for the formulation DABA‐0.5, copolymerization and homopolymerization do not overlap with each other. The reactions progressed sequentially and homopolymerization occurred after completion of copolymerization. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3244–3247, 2004     

Porous AlN ceramic substrates by reaction sintering

A novel approach was undertaken in producing porous AlN microelectronics tapes with high thermal conductivity and low dielectric constant. This method essentially utilised polymer micro-spherical powders that were used as a sacrificial mould to introduce controlled porosity into the green tapes during pyrolysis. The Al₂O₃-rich porous green tapes were then reaction sintered at 1680 °C for 12 h to achieve porous AlN tapes. This work builds upon the previously developed novel reaction sintering process that densified and converted Al₂O₃-rich tapes (Al₂O₃–20 wt.% AlN–5 wt.% Y₂O₃) to AlN tapes at a relatively low sintering temperature of 1680 °C. The sintering behaviour of the porous tapes was investigated, and the effects of the microspheres particle size and volume addition were studied. The microspheres successfully contributed to the significant reduction of tape density by porosity, and this contributed to lowering its dielectric constant. Dielectric constant of the AlN tapes were reduced to about 6.8–7.7 whilst thermal conductivity values were reasonable at about 46–60 W/m K. Coefficient of thermal expansion (CTE) values showed a linear trend according to phase composition, with the porous AlN tapes exhibiting CTE values of (4.4–4.8)×10⁻⁶ °C⁻¹, showing good CTE compatibility with silicon, at 4.0×10⁻⁶ °C⁻¹. The added porosity did not significantly affect the CTE values.     

Incorporation of Very Insoluble Monomers in Waterborne Coatings

The benefits of polymerizing very insoluble monomers in aqueous media, avoiding the use of energy‐intensive procedures, by implementing two novel synthesis techniques based on the emulsifier combination in emulsion polymerization and on miniemulsification by phase inversion temperature are investigated. The performance of standalone polymers consisting of monomers, namely lauryl methacrylate, isobornyl acrylate, and 1H,1H,2H,2H‐perfluorodecyl acrylate, and of formulated binders with these monomers incorporated either through blending or in situ polymerization, is evaluated with special emphasis on their water‐barrier properties (e.g., uptake, whitening, immersion, and vapor resistance) and on their chemical resistance. The performance of the standalone polymers is found to be similar to that of polymers prepared by high‐shear miniemulsion polymerization, while the performance of the formulated binders is generally superior to a commercial coating formulation based on a binder recommended for water resistance.     

The Saccharomyces cerevisiae alcohol acetyl transferase Atf1p is localized in lipid particles

The yeast alcohol acetyl transferase I, Atf1p, is responsible for the major part of volatile acetate ester production in fermenting Saccharomyces cerevisiae cells. Some of these esters, such as ethyl acetate and isoamyl acetate, are important for the fruity flavours of wine, beer and other fermented beverages. In order to reveal the subcellular localization of Atf1p and further unravel the possible physiological role of this protein, ATF1::GFP fusion constructs were overexpressed in brewer's yeast. The transformant strain showed a significant increase in acetate ester formation, similar to that of an ATF1 overexpression strain, indicating that the Atf1p-GFP fusion protein was active. UV fluorescence microscopy revealed that the fusion protein was localized in small, sphere-like organelles. These organelles could be selectively stained by the fluorescent dye Nile red, indicating that they contained high amounts of neutral lipids and/or sterols, a specific characteristic of yeast lipid particles. Purification of lipid particles from wild type and ATF1 deletion cells confirmed that the Atf1p-GFP fusion protein was located in these organelles. Furthermore, a clear alcohol acetyl transferase activity could be measured in the purified lipid particles of both wild type and transformed cells. The localization of Atf1p in lipid particles may indicate that Atf1p has a specific role in the lipid and/or sterol metabolism that takes place in these particles.