Self Assembly–Assisted Additive Manufacturing: Direct Ink Write 3D Printing of Epoxy–Amine Thermosets

The use of self‐assembling, pre‐polymer materials in 3D printing is rare, due to difficulties of facilitating printing with low molecular weight species and preserving their reactivity and/or functions on the macroscale. Akin to 3D printing of small molecules, examples of extrusion‐based printing of pre‐polymer thermosets are uncommon, arising from their limited rheological tuneability and slow reactions kinetics. The direct ink write (DIW) 3D printing of a two‐part resin, Epon 828 and Jeffamine D230, using a self‐assembly approach is reported. Through the addition of self‐assembling, ureidopyrimidinone‐modified Jeffamine D230 and nanoclay filler, suitable viscoelastic properties are obtained, enabling 3D printing of the epoxy–amine pre‐polymer resin. A significant increase in viscosity is observed, with an infinite shear rate viscosity of approximately two orders of magnitude higher than control resins, in addition to, an increase in yield strength and thixotropic behavior. Printing of simple geometries is demonstrated with parts showing excellent interlayer adhesion, unachievable using control resins.     

Cellular Disulfide Bond Formation in Bioactive Peptides and Proteins

Bioactive peptides play important roles in metabolic regulation and modulation and many are used as therapeutics. These peptides often possess disulfide bonds, which are important for their structure, function and stability. A systematic network of enzymes—a disulfide bond generating enzyme, a disulfide bond donor enzyme and a redox cofactor—that function inside the cell dictates the formation and maintenance of disulfide bonds. The main pathways that catalyze disulfide bond formation in peptides and proteins in prokaryotes and eukaryotes are remarkably similar and share several mechanistic features. This review summarizes the formation of disulfide bonds in peptides and proteins by cellular and recombinant machinery.     

Rationally Designed Polypharmacology: α-Helix Mimetics as Dual Inhibitors of the Oncoproteins Mcl-1 and HDM2

Protein–protein interactions (PPIs), many of which are dominated by α-helical recognition domains, play key roles in many essential cellular processes, and the dysregulation of these interactions can cause detrimental effects. For instance, aberrant PPIs involving the Bcl-2 protein family can lead to several diseases including cancer, neurodegenerative diseases, and diabetes. Interactions between Bcl-2 pro-life proteins, such as Mcl-1, and pro-death proteins, such as Bim, regulate the intrinsic pathway of apoptosis. p53, a tumor-suppressor protein, also has a pivotal role in apoptosis and is negatively regulated by its E3 ubiquitin ligase HDM2. Both Mcl-1 and HDM2 are upregulated in numerous cancers, and, interestingly, there is crosstalk between both protein pathways. Recently, synergy has been observed between Mcl-1 and HDM2 inhibitors. Towards the development of new anticancer drugs, we herein describe a polypharmacology approach for the dual inhibition of Mcl-1 and HDM2 by employing three densely functionalized isoxazoles, pyrazoles, and thiazoles as mimetics of key α-helical domains of their partner proteins.     

Identification of Sulfur‐Containing Impurities in Biodiesel Produced From Brown Grease

Fatty acid methyl esters (FAME) from waste grease usually contain higher concentrations of sulfur (S) than allowed to meet the specified quality standard for biodiesel (<15 ppm). Brown grease lipid‐derived FAME was produced and fractionated by two passes through a wiped‐film evaporator (WFE) to produce three fractions: (1) a 120 °C pass distillate, (2) a 170 °C pass distillate, and (3) a heavy residue. Solid phase extraction (SPE) was used to concentrate the S species from the distillate fractions so that they could be detected by a gas chromatography–pulsed flame photometric detector (GC–PFPD) and GC–mass spectrometry (MS). The ethyl acetate and methanol (MeOH) fractions obtained by SPE of the 120 °C WFE distillate and methyl tert‐butyl ether and acetone fractions obtained by SPE of the 170 °C WFE distillate had the highest concentration of S and were, therefore, the best candidates for GC–PFPD analysis. GC–PFPD methods were developed to separate the S species adequately enough for those peaks to be analyzed by GC–MS which matched fragmentation patterns identified by the MS chemical library as tetrahydrothiophenes, dithiolanes, and thiophenes. MS fragmentation patterns were used to identify other, larger, S‐bearing species as sulfides and disulfides cross‐linking between two FAME molecules. The results obtained from this study provide a foundation for developing effective purification methods to remove S‐containing impurities from waste grease‐derived biodiesel.     

Durability of fire retardant treated wood products at humid and exterior conditions review of literature

Fire retardants may considerably improve the fire properties of wood products, but the durability, e.g. in exterior applications, has not been addressed fully. This paper reviews the existing knowledge and experience mainly from the USA with the aim of supporting further development in Europe. The review is concentrated on pressure impregnated fire retardant treated wood products which have the best opportunities for increased durability. Copyright © 2001 by John Wiley & Sons, Ltd.     

Alarm Pheromone Composition and Behavioral Activity in Fungus-Growing Ants

Chemical communication is a dominant method of communication throughout the animal kingdom and can be especially important in group-living animals in which communicating threats, either from predation or other dangers, can have large impacts on group survival. Social insects, in particular, have evolved a number of pheromonal compounds specifically to signal alarm. There is predicted to be little selection for interspecific variation in alarm cues because individuals may benefit from recognizing interspecific as well as conspecific cues and, consequently, alarm cues are not normally thought to be used for species or nestmate recognition. Here, we examine the composition of the alarm pheromones of seven species of fungus-growing ants (Attini), including both basal and derived species and examine the behavioral responses to alarm pheromone of Acromyrmex leaf-cutting ants, the sister genus to the highly studied Atta leaf-cutting ants. We find surprisingly high interspecific variation in alarm pheromone composition across the attine phylogeny. Interestingly, the active component of the alarm pheromone was different between the two leaf-cutting ant genera. Furthermore, in contrast to previous studies on Atta, we found no differences among morphological castes in their responses to alarm pheromone in Acromyrmex but we did find differences in responses among putative age classes. The results suggest that the evolution of alarm communication and signaling within social insect clades can be unexpectedly complex and that further work is warranted to understand whether the evolution of different alarm pheromone compounds is adaptive.     

Effect of processing parameters on the morphology development during extrusion of polyethylene tape: An in-line small-angle X-ray scattering (SAXS) study

The in-line development of crystalline morphology and orientation during melt extrusion of low density polyethylene (LDPE) tape at nil and low haul-off speeds has been investigated using Small-Angle X-Ray Scattering (SAXS). The processing parameters, namely haul-off speed and distance down the tape-line have been varied and the resulting crystalline morphology is described from detailed analysis of the SAXS data. Increasing haul-off speed increased orientation in the polymer tape and the resulting morphology could be described in terms of regular lamellar stacking perpendicular to the elongation direction. In contrast, under nil haul-off conditions the tape still showed some orientation down the tape-line, but a shish-kebab structure prevails. The final lamellae thickness ( ∼50 Å) and bulk crystallinity (∼20%), were low at, for all processing conditions investigated, which is attributed to the significant short-chain branching in the polymer acting as point defects limiting lamellae crystal growth.     

Co-operative corrosion phenomena

The corrosion of aluminium alloy 2024-T3 (AA2024-T3) was studied as a function of immersion time from 2.5 to 120 min in 0.1 M aqueous NaCl solution. At immersion times as short as 5 min, rings of corrosion product of 100 to 200 μm diameter, containing smaller domes of corrosion product, were observed using SEM. The domes of corrosion product had greater chloride concentrations than elsewhere on the surface and represented sites of anodic attack. As the immersion time was increased, significant grain boundary attack was observed within the rings of corrosion product. Analyses of Particle Induced X-ray Emission (PIXE) maps of the corroded surfaces showed a significantly higher number of IM particles around the chloride attack sites than the average particle density for the maps, indicating clustering of IM particles. These results suggest a co-operative corrosion effect as a result of clustering of the IM particles. A mechanism for the generation of the corrosion rings is discussed.     

Energy Efficiency of the Outotec<Superscript>®</Superscript> Ausmelt Process for Primary Copper Smelting

The global, non-ferrous smelting industry has witnessed the continual development and evolution of processing technologies in a bid to reduce operating costs and improve the safety and environmental performance of processing plants. This is particularly true in the copper industry, which has seen a number of bath smelting technologies developed and implemented during the past 30 years. The Outotec^® Ausmelt Top Submerged Lance Process is one such example, which has been widely adopted in the modernisation of copper processing facilities in China and Russia. Despite improvements in the energy efficiency of modern copper smelting and converting technologies, additional innovation and development is required to further reduce energy consumption, whilst still complying with stringent environmental regulations. In response to this challenge, the Ausmelt Process has undergone significant change and improvement over the course of its history, in an effort to improve its overall competitiveness, particularly with respect to energy efficiency and operating costs. This paper covers a number of recent advances to the technology and highlights the impacts of these developments in reducing energy consumptions for a range of different copper flowsheets. It also compares the energy efficiency of the Ausmelt Process against the Bottom Blown Smelting process, which has become widely adopted in China over the past 5–10 years.