N-1-alkylitaconamic acids-co-styrene copolymers. Surface characterization

A serie of six N-1-alkylitaconamic acids-co-styrene copolymers with alkyl groups varying in side chain length from 3 to 12 was used in this study. The surface behaviour of the copolymers has been studied as function of the side chain length. Contact angle data for two of these copolymer surfaces were obtained in water and several liquids. From this information the surface energy was determined. Differences in the wettability of N-1-alkylitaconamic acid-co-styrene are found. The results are discussed in terms of hydrophobic and polar effect of the copolymers. Results on spread monolayers characteristics of these copolymers on water surfaces are also reported. Surface pressure-area (π-A) isotherms on a pure water subphase exhibit a transition region depending on the length of the alkyl side chain of the itaconamic acid moiety. It was also analyzed the phase transition in the monolayer at the air/water interface by brewster angle microscopy (BAM). Molecular mechanics approach was used to obtain predictions about the local interaction energies between segments. It was possible to conclude that the local interaction energies of propyl and decyl derivatives are quite similar while the hexyl derivative has higher interaction energy. The analysis of the coulombic energies together with the dispersion van der Waals energies (VDW) would be indicative, in first approximation, that carbonyl groups are more exposed in the case of propyl than in the other copolymers studied.     

Personal protective clothing and safety of firefighters near a high intensity fire front

The main objective of this work is the establishment of useful guide lines for secure fighting of high intensity fires, namely the determination of the influence of the personal protective clothing properties on safety during wildland firefighting operations. The physiological reaction of men exposed to these extreme conditions is obtained by numerical simulation of the heat and the mass transfer from an individual in the proximity of a fire line, as representative of a typical situation of a firefighter suppressing a high intensity fire. It is obvious that the impinging flux density depends on flame's dimensions and its properties as well as on the distance between the flame and those involved in fire suppression activities. The results obtained were calculated using a computer program based on a modified version of the Stolwijk thermoregulation model. Taking into account the time evolutions of skin, rectal and hypothalamus temperatures, a parametric study is presented about the importance of clothing properties, activity level and other external parameters in order to avoid the risk of significant undesired thermophysiological reactions within the firefighters. The results clearly show that, besides the improvement of personal protective clothing properties, the safety of firefighters is essentially related to good control of the exposure times to these high intensity radiation fluxes.     

Exploring the Interaction of Curaxin CBL0137 with G-Quadruplex DNA Oligomers

Curaxins and especially the second-generation derivative curaxin CBL0137 have important antitumor activities in multiple cancers such as glioblastoma, melanoma and others. Although most of the authors suggest that their mechanism of action comes from the activation of p53 and inactivation of NF-kB by targeting FACT, there is evidence supporting the involvement of DNA binding in their antitumor activity. In this work, the DNA binding properties of curaxin CBL0137 with model quadruplex DNA oligomers were studied by ¹H NMR, CD, fluorescence and molecular modeling. We provided molecular details of the interaction of curaxin with two G-quadruplex structures, the single repeat of human telomere d(TTAGGGT)₄ and the c-myc promoter Pu22 sequence. We also performed ¹H and ³¹P NMR experiments were also performed in order to investigate the interaction with duplex DNA models. Our data support the hypothesis that the interaction of curaxin with G-quadruplex may provide a novel insight into the DNA-binding properties of CBL0137, and it will be helpful for the design of novel selective DNA-targeting curaxin analogues.     

Solubilities,viscosities and unperturbed dimensions of poly (2,6-diisopropylphenyl methacrylate)

The dilute solution properties of poly(2,6-diisopropylphenyl methacrylate) (PDPP) in various solvents were studied by viscosity, exclusion chromatography and osmotic pressure measurements. The Mark-Houwink-Kuhn-Sakurada relationships were established. The unperturbed dimensions, the rigidity factor σ, the characteristic ratio C∞ and the thermodynamic parameters were determined using the Stockmayer-Fixman equation and from data in theta solvent (binary mixture). The rigidity factor of PDPP is abnormally high. The conformational behaviour of this polymer is analysed in terms of the effect of the side chain structure. The results are compared with other polymers of the same series.     

Viscosity studies of some polyamides dissolved in mixed solvents (cosolvents)

The solubility of poly (octamethylene sebacamide) (POS), poly (octamethylene terephthalamide) (POT) and poly (octamethylene tetrachloroterephthalamide) (POTC1), in $\text{m-}\text{cresol}\text{cyclohexane}$ mixtures, a cosolvent system, has been studied by measuring the intrinsic viscosity [η], at 25°C. The intrinsic viscosities of POT, POS and POTC1 in various solvent/non-solvent mixtures are higher than the corresponding intrinsic viscosities in the pure solvent m-cresol. The POT and POTC1 polyamides exhibit a sharp increase in [η] values compared with the corresponding small increase in the POS polyamide. The POTC1 polyamide presents a true cosolvency effect in $\text{m-}\text{cresol}\text{cyclohexane}$ mixtures; m-cresol and cyclohexane are non-solvents for this polyamide. The cosolvent behaviour is discussed in terms of the most energetically favourable interactions. The aromatic ring in POT and POTC1 would expand the chain, would favour a better packing between neighbouring solvent molecules and would favour the selective adsorption in the cosolvent system.     

Freshness retention of minimally processed melon using different packages and multilayered edible coating containing microencapsulated essential oil

This study evaluated the effectiveness of packaging using a microencapsulated β‐cyclodextrin and trans‐cinnamaldehyde complex incorporated into a base chitosan matrix on the shelf life of fresh‐cut melon (Cucumis melo L. var. Reticulatus Naud) group Inodorus that were coated with a multilayered coating system using a polypropylene tray (Ziploc^®) with (i) Ziploc^® lid, (ii) Saran^® wrap and (iii) plain cheesecloth and stored at 4 °C for 15 days. The multilayered antimicrobial coating improved the shelf life of fresh‐cut melon (up to 15 days), compared with the controls (7 days). Coated samples were firmer, maintained colour and total carotenoids content and showed less weight loss than the controls (P < 0.05). Among the packaging treatments, the Ziploc^® lid was the most effective in maintaining shelf life. This study demonstrates the application of a new generation of edible coating using natural antimicrobial agents by means of the layer‐by‐layer assembly.     

Storage stability of a tropical fruit (cashew apple,acerola, papaya,guava and passion fruit) mixed nectar added caffeine

Nectars are formulated beverages with a fruit juice or pulp as its main component. A blend of fruits can also be used, with the advantage of combining sensory and nutritional properties of different fruits. The beverages may be added with some energetic component, as caffeine, known by its stimulating effect on central nervous system. The objective of this study was to develop mixed nectar of cashew apple, papaya, guava, acerola fruit and passion fruit added caffeine. The beverage was prepared with 35% juice blend and 10% sugar, added with 100 mg of caffeine L^?1 and 60 mg of sodium metabisulfite (SO₂) L^?1 and 500 mg of sodium benzoate L^?1 as preservatives, packed in cleaned pasteurised bottles and heat processed at 90 °C for 30 s. Physicochemical, microbiological and sensory analyses of the beverage were performed initially (time zero) and during 6 months of storage at room temperature (about 25 °C). The products were microbiologically stable during storage. The vitamin C content decreased significantly throughout storage time, although it has remained relatively high. The product presented good sensory acceptance, which suggests its potential for market.