Radiation Induced Superabsorbent Hydrogels. Acrylamide/Itaconic Acid Copolymers

Acrylamide/itaconic acid hydrogels in the form of rods are prepared by γ‐irradiation of ternary mixtures of acrylamide/itaconic acid/water with 2.00–5.71 kGy γ‐rays. Spectroscopic and thermal characterization of the copolymers were examined. Dynamic and equilibrium swelling behavior of superabsorbent acrylamide/itaconic acid hydrogels was investigated in water. The equilibrium swelling degree, the swelling rate coefficient, the diffusion constant, the diffusion exponent, the diffusion coefficient, and the intrinsic diffusion coefficient of acrylamide/itaconic acid hydrogels were calculated. The superabsorbent hydrogels have shown mass swelling capabilities in the range 650–700% (for polyacrylamide hydrogels) and 900–2100% (for acrylamide‐itaconic acid hydrogels). Diffusion type of the hydrogels is non‐Fickian diffusion. The equilibrium swelling studies were used to determine important parameters of the crosslinked structure of the hydrogels, including the average molar mass between crosslinks and crosslink density.     

The Next Frontier: Translational Development of Ubiquitination,SUMOylation, and NEDDylation in Cancer

Post-translational modifications of proteins ensure optimized cellular processes, including proteostasis, regulated signaling, cell survival, and stress adaptation to maintain a balanced homeostatic state. Abnormal post-translational modifications are associated with cellular dysfunction and the occurrence of life-threatening diseases, such as cancer and neurodegenerative diseases. Therefore, some of the frequently seen protein modifications have been used as disease markers, while others are targeted for developing specific therapies. The ubiquitin and ubiquitin-like post-translational modifiers, namely, small ubiquitin-like modifier (SUMO) and neuronal precursor cell-expressed developmentally down-regulated protein 8 (NEDD8), share several features, such as protein structures, enzymatic cascades mediating the conjugation process, and targeted amino acid residues. Alterations in the regulatory mechanisms lead to aberrations in biological processes during tumorigenesis, including the regulation of tumor metabolism, immunological modulation of the tumor microenvironment, and cancer stem cell stemness, besides many more. Novel insights into ubiquitin and ubiquitin-like pathways involved in cancer biology reveal a potential interplay between ubiquitination, SUMOylation, and NEDDylation. This review outlines the current understandings of the regulatory mechanisms and assay capabilities of ubiquitination, SUMOylation, and NEDDylation. It will further highlight the role of ubiquitination, SUMOylation, and NEDDylation in tumorigenesis.     

Spectroscopic,thermal, and mechanical characterization of carboxyl-terminated polybutadiene-based carbon black-filled networks

Carbon black-filled and unfilled carboxyl-terminated polybutadiene (CTPB) networks were prepared by using two types of reactive systems at different reactive group ratios to be applied to the solid propellant motor case as a liner. For the preparation of CTPB networks, tris(2-methyl-1 aziridinyl)phosphine oxide (MAPO) and a mixture of liquid bisphenol A-epichlorohydrin (Epikote-828) and MAPO were used as two different reactive systems. The chemistry and thermal stability of the CTPB networks were followed by Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG) techniques, whereas mechanical and adhesive properties were tested by tensile measurements. The mixed reactive system caused a modification in the ultimate tensile stress and elongation-at-break properties, adhesive properties, and thermal stability of the CTPB networks. It was understood that this modification was due to the inter- and intramolecular bridge formation via the end-linking reaction of Epikote-828 with amine groups of the former network chains. The combination of MAPO with Epikote-828 also imparted better peel and lap-shear strength properties to the CTPB elastomers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 355–366, 1997     

A comparative study of using allyl alcohol based copolymers in the preservation of wood: Oak vs. cedar

Wood is an important raw material that is cheap and easily worked. However, wooden objects are subject to environmental attack and mechanical shocks. In this study, our aim is to preserve wooden objects against envrironmental deterioration and mechanical shocks on to consolidate objects already degraded. Allyl alcohol (AA), acrylonitrile (AN), methyl methacrylate (MMA) and AA/AN, AA/MMA monomer mixtures were impregnated into oak and cedar. Polymerization was accomplished by gamma irradiation. The mechanical properties and the dimensional stability of the wood‐copolymer composites were determined. The presence of polymer and copolymer in the wood increased the mechanical durability of the wood. The results of the hardness tests and the compressive strengths determined in parallel and perpendicular directions to the fibers revealed that P(AA/MMA), P(AA/AN) copolymers are effective in increasing the mechanical durability of pristine‐oak and cedar woods. Similar results were also obtained from hardness tests. The decrease in the mechanical durability of pristine‐oak and cedar woods after aging for 28 days is slight. The water uptake capacity of wood + copolymer composites was observed to decrease by more than 50% compared with the original samples. In the cedar wood, where the density is low and the quantity of copolymer is high, this decrease ranged from 100% to 50%.     

Effect of preparation methods on thermal properties of poly(acrylic acid)/silica composites

Poly(acrylic acid)-silica composites have been prepared by two different methods and thermally characterized. The glass transition temperature (T_g) of the PAA-SiO₂ system prepared by mixture method was found to be 120°C irrespective of the type and amounts of silica involved in this work. However, the T_g varied between 132°C and 113°C in the systems prepared by polymerization reaction depending upon the type of silica and percentage conversion. The composites prepared by mixture and polymerization method have been investigated by using thermogravimetry (TGA) to follow the kinetics of anhydride formation and thermal degradation reactions. The activation energy of thermal anhydride formation and thermal degradation reaction was not found to change very much with ratio of PAA-SiO₂ when the composites were prepared by simple mixing. For the composites prepared by polymerization method the activation energy of anhydride formation and thermal degradation reaction were observed to change with percentage conversion. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 891–895, 1998     

Drying and conservation conditions of pollen

In this study, drying and conservation conditions of pollens (for Anzer Honey) were experimentally investigated, and the general drying curve equation was derived by applying the Least Squares Method. Drying experiments were conducted in solar‐ and electric‐assisted dryers. Pollens were placed on the shelves as 50 each g in a single layer having a depth of 2.5 mm. During the drying experiments, the shelf temperatures of the drying cupboard were regulated between 40 °C and 45 °C. Weight losses, moisture contents and mass shrinkage of pollens and average temperatures in the shelves were determined and calculated based on drying time. Additionally, the experimental uncertainty values were calculated as approximately 18%, depending on the experimental results. It was concluded that pollens should be dried at temperatures between 40 °C and 45 °C for between 2.5 and 3 h so as not to change the colour, flavour, smell and structure, and conserved in brown bottles under vacuum in a shady medium. © 2000 Society of Chemical Industry     

Studies on the applicability of alginate-entrapped Chryseomonas luteola TEM 05 for heavy metal biosorption

Chryseomonas luteola TEM 05 cells were entrapped both in alginate and chitosan coated alginate beads. Biosorption of metal ions on alginate beads was investigated by using a batch stirred system at pH 6.0, 25 degrees C, in initial metal concentration of 1.92 mM of Cr6+, 0.89 mM Cd2+ and 1.69 mM Co2+. Then, a process of competitive biosorption of these metal ions was described and compared to single metal ion adsorption in solution. The apparent equilibrium biosorption was reached within the 180 min of contact for all metals. Although the competitive biosorption capacities of the beads for all metal ions were lower than those of single conditions, Cd2+ biosorption on alginate and alginate-chitosan beads did not change significantly.     

Thermoelastic stress field in a piecewise homogeneous domain under non‐uniform temperature using a coupled boundary and finite element method

This study concerns the development of a coupled finite element–boundary element analysis method for the solution of thermoelastic stresses in a domain composed of dissimilar materials with geometric discontinuities. The continuity of displacement and traction components is enforced directly along the interfaces between different material regions of the domain. The presence of material and geometric discontinuities are included in the formulation explicitly. The unknown interface traction components are expressed in terms of unknown interface displacement components by using the boundary element method for each material region of the domain. Enforcing the continuity conditions leads to a final system of equations containing unknown interface displacement components only. With the solution of interface displacement components, each region has a complete set of boundary conditions, thus leading to the solution of the remaining unknown boundary quantities. The concepts developed for the BEM formulation of a domain with dissimilar regions is employed in the finite element–boundary element coupling procedure. Along the common boundaries of FEM–BEM regions, stresses from specific BEM regions are first expressed in terms of interface displacements, then integrated and lumped at the nodal points of the common FEM–BEM boundary so that they are treated as boundary conditions in the analysis of FEM regions along the common FEM–BEM boundary. Copyright © 2002 John Wiley & Sons, Ltd.     

The preparation of ultra narrow molecular weight distribution poly(ethylene glycol)s by fractional crystallization from solution

The preparation of very narrow molecular weight distribution poly(ethylene glycol) (PEG) was investigated by fractional crystallization from solution. Fractionation experiments were conducted from the solutions of 1500, 2000, and 3000 molecular weight PEG in n‐butanol/n‐heptane mixtures. Size Exclusion Chromatography and Differential Scanning Calorimetric studies were performed for the characterization of fractions prepared at different crystallization temperatures and times. By suitable choice of these experimental parameters it was possible to obtain PEG fractions with M_w/M_n ≤ 1.05. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1999–2005, 2001     

Improvement of the mechanical stability of oak by radiation-induced in-situ copolymerization of allyl glycidyl ether with acrylonitrile and methyl methacrylate

This study deals with the improvement of the mechanical stability of oak, which belongs to the hardwoods, by radiation-induced in-situ copolymerization of certain monomers. Acrylonitrile (AN), methyl methacrylate (MMA), allyl glycidyl ether/acrylonitrile (AGE/AN), and allyl glycidyl ether/methyl methacrylate (AGE/MMA) monomers and monomer mixtures were employed to conserve and consolidate the wood. After impregnating oak with these monomer mixtures, polymerization was accomplished by γ-irradiation. The relationships between the mechanical properties of the wood/(co)polymer composites and the anatomic structure of the wood, the types and the quantity of the polymer and copolymer, the irradiation dose and the aging process were explored. The fine structure of the wood/(co)polymer composites and the compatibility of wood with polymer and copolymer were investigated by scanning electron microscopy. The existence of polymer and copolymer in the wood enhanced the mechanical durability of the wood. The results of the hardness and the compressive strength tests applied in the parallel and perpendicular directions to the fibers of the wood/(co)polymer composites show that P(AGE/MMA), P(AGE/AN) copolymers are effective in raising the mechanical durability. In the case of P(AGE/MMA), the increase in the compressive strength perpendicular to the fibers in the oak wood is 179% at highest conversion. Similar results were also acquired from hardness tests. The decrease in the mechanical durability after aging for 28 d was very little.