Correction: Weingart et al. Expanded Polycarbonate (EPC)-A New Generation of High-Temperature Engineering Bead Foams. Polymers 2020, 12, 2314.

In the original publication [...].

Insights into the Bead Fusion Mechanism of Expanded Polybutylene Terephthalate (E-PBT).

Expandable polystyrene (EPS) and expanded polypropylene (EPP) dominate the bead foam market. As the low thermal performance of EPS and EPP limits application at elevated temperatures novel solutions such as expanded polybutylene terephthalate (E-PBT) are gaining importance. To produce parts, individual beads are typically molded by hot steam. While molding of EPP is well-understood and related to two distinct melting temperatures, the mechanisms of E-PBT are different. E-PBT shows only one melting peak and can surprisingly only be molded when adding chain extender (CE). This publication therefore aims to understand the impact of thermal properties of E-PBT on its molding behavior. Detailed differential scanning calorimetry was performed on neat and chain extended E-PBT. The crystallinity of the outer layer and center of the bead was similar. Thus, a former hypothesis that a completely amorphous bead layer enables molding, was discarded. However, the incorporation of CE remarkably reduces the crystallization and re-crystallization rate. As a consequence, the time available for interdiffusion of chains across neighboring beads increases and facilitates crystallization across the bead interface. For E-PBT bead foams, it is concluded that sufficient time for polymer interdiffusion during molding is crucial and requires adjusted crystallization kinetics.

Expanded Polycarbonate (EPC)-A New Generation of High-Temperature Engineering Bead Foams.

Bead foams serve in a wide variety of applications, from insulation and packaging to midsoles in shoes. However, the currently used materials are limited to somewhat low temperature or exhibit significant changes in modulus in the temperature range of many applications due to their glass transition. By comparison, polycarbonate (PC) exhibits almost constant mechanics for temperatures up to 130 °C. Therefore, it appears as an advantageous base material for bead foams. The aim of the publication is to provide comprehensive data on the properties of expanded PC (EPC) in comparison to already commercially available expanded polypropylene, EPP, and expanded polyethylene-terephthalate, EPET. A special focus is set on the thermo-mechanical properties as these are the most lacking features in current materials. In this frame, dynamic mechanical analysis, and tensile, bending, compression and impact tests at room temperature (RT), 80 °C, and 110 °C are conducted for the three materials of the same density. Already at RT, EPC exhibits superior mechanics compared to its peers, which becomes more pronounced toward higher temperature. This comes from the low sensitivity of properties to temperature as EPC is used below its glass transition. In summary, EPC proves to be an outstanding foam material over a broad range of temperatures for structural applications.

Odorant Receptor Inhibition Is Fundamental to Odor Encoding.

Most natural odors are complex mixtures of volatile components, competing to bind odorant receptors (ORs) expressed in olfactory sensory neurons (OSNs) of the nose. To date, surprisingly little is known about how OR antagonism shapes neuronal representations in the detection layer of the olfactory system. Here, we investigated its prevalence, the degree to which it disrupts OR ensemble activity, and its conservation across phylogenetically related ORs. Calcium imaging microscopy of dissociated OSNs revealed significant inhibition, often complete attenuation, of responses to indole-a commonly occurring volatile associated with both floral and fecal odors-by a set of 36 tested odorants. To confirm an OR mechanism for the observed inhibition, we performed single-cell transcriptomics on OSNs exhibiting specific response profiles to a diagnostic panel of odorants and identified three paralogous receptors-Olfr740, Olfr741, and Olfr743-which, when tested in vitro, recapitulated OSN responses. We screened ten ORs from the Olfr740 gene family with ∼800 perfumery-related odorants spanning a range of chemical scaffolds and functional groups. Over half of these compounds (430) antagonized at least one of the ten ORs. OR activity fitted a mathematical model of competitive receptor binding and suggests normalization of OSN ensemble responses to odorant mixtures is the rule rather than the exception. In summary, we observed OR antagonism occurred frequently and in a combinatorial manner. Thus, extensive receptor-mediated computation of mixture information appears to occur in the olfactory epithelium prior to transmission of odor information to the olfactory bulb.

Comparison of the Foamability of Linear and Long-Chain Branched Polypropylene-The Legend of Strain-Hardening as a Requirement for Good Foamability.

Polypropylene (PP) is an outstanding material for polymeric foams due to its favorable mechanical and chemical properties. However, its low melt strength and fast crystallization result in unfavorable foaming properties. Long-chain branching of PP is regarded as a game changer in foaming due to the introduction of strain hardening, which stabilizes the foam morphology. In this work, a thorough characterization with respect to rheology and crystallization characteristics of a linear PP, a PP/PE-block co-polymer, and a long-chain branched PP are conducted. Using these results, the processing window in foam-extrusion trials with CO2 and finally the foam properties are explained. Although only LCB-PP exhibits strain hardening, it neither provide the broadest foaming window nor the best foam quality. Therefore, multiwave experiments were conducted to study the gelation due to crystallization and its influence on foaming. Here, linear PP exhibited a gel-like behavior over a broad time frame, whereas the other two froze quickly. Thus, apart from strain hardening, the crystallization behavior/crystallization kinetics is of utmost importance for foaming in terms of a broad processing window, low-density, and good morphology. Therefore, the question arises, whether strain hardening is really essential for low density foams with a good cellular morphology.

Effect of Resin and Blocked/Unblocked Hardener Mixture on the Production of Epoxy Foams with CO2 Blocked Hardener in Batch Foaming Process.

The present study focuses on the processing and properties of epoxy foams by the use of CO2 blocked hardener N-aminoethylpiperazine (B-AEP) and different resins. Although some studies described the foaming with carbamates, little attention has been given to the interaction of resin properties (such as viscosity) on the foaming performance. Therefore, two resins, diglycidyl ether of bisphenol-A (DGEBA) and epoxy novolac (EN), as well as their 50:50 blend, were foamed with B-AEP and unblocked/blocked AEP hardener mixtures in a batch foaming process. Furthermore, the commercially available chemical blowing agent para-toluenesulfonyl hydrazide (TSH) was used as a benchmark for commonly used chemical blowing agents. The lowest density in this study was reached by the DGEBA+B-AEP system in the range of 215 kg/m3 with the drawback of an inhomogeneous cell structure and high cell size distribution. The best cell morphology and lowest cell size distribution was reached with the EN+15:85% unblocked:blocked hardener mixture, resulting in a density in the range of 394 kg/m3. A syntactic foam was achieved by a DGEBA+50:50% unblocked:blocked hardener mixture with a density of around 496 kg/m3. It was found that a higher viscosity of the resin lead to an increase in the density and a decrease in the cell size distribution range as a result of a closer expansion time window.

FLP-1 neuropeptides modulate sensory and motor circuits in the nematode Caenorhabditis elegans.

Parasitic nematodes infect over one quarter of the population worldwide, causing morbidity in over one billion people. Current anthelmintic drugs are beginning to lose effectiveness due to the presence of resistant strains. We are interested in the role of neuropeptides, which regulate behaviors in all organisms, as another possible target for anthelmintic drugs. FMRFamide-related peptides (FaRPs) are a family of neuropeptides that are conserved throughout the animal kingdom. In particular, nematodes contain the largest family of FaRPs identified thus far and many of these FaRPs are identical among different nematode species; FaRPs in nematodes are collectively referred to as FLPs (FMRFamide-like peptides). However, little is known about the function of these FLPs. We are using the non-parasitic nematode Caenorhabditis elegans as a model for examining FLPs in nematodes. C. elegans contains at least 31 flp genes that encode 72 potential FLPs. Among the flp genes, flp-1 is one of the few that is universally found in nematodes. FLP-1 neuropeptides were previously reported to be involved in sensory and motor functions. However, previous alleles of flp-1 also disrupted a neighboring gene, daf-10. To understand the phenotypes of flp-1, new alleles that specifically disrupt flp-1 were characterized. The previously reported locomotory and egg-laying defects were found to be due to loss of flp-1, while the osmolarity defect is due to loss of daf-10. In addition, loss of flp-1 and daf-10 both cause several phenotypes that increase in severity in the double mutants by disrupting different neurons in the neural circuits.

APL-1, the Alzheimer's Amyloid precursor protein in Caenorhabditis elegans, modulates multiple metabolic pathways throughout development.

Mutations in the amyloid precursor protein (APP) gene or in genes that process APP are correlated with familial Alzheimer's disease (AD). The biological function of APP remains unclear. APP is a transmembrane protein that can be sequentially cleaved by different secretases to yield multiple fragments, which can potentially act as signaling molecules. Caenorhabditis elegans encodes one APP-related protein, APL-1, which is essential for viability. Here, we show that APL-1 signaling is dependent on the activity of the FOXO transcription factor DAF-16 and the nuclear hormone receptor DAF-12 and influences metabolic pathways such as developmental progression, body size, and egg-laying rate. Furthermore, apl-1(yn5) mutants, which produce high levels of the extracellular APL-1 fragment, show an incompletely penetrant temperature-sensitive embryonic lethality. In a genetic screen to isolate mutants in which the apl-1(yn5) lethality rate is modified, we identified a suppressor mutation in MOA-1/R155.2, a receptor-protein tyrosine phosphatase, and an enhancer mutation in MOA-2/B0495.6, a protein involved in receptor-mediated endocytosis. Knockdown of apl-1 in an apl-1(yn5) background caused lethality and molting defects at all larval stages, suggesting that apl-1 is required for each transitional molt. We suggest that signaling of the released APL-1 fragment modulates multiple metabolic states and that APL-1 is required throughout development.