Closed-Cell Rigid Polyimide Foams for High-Temperature Applications: The Effect of Structure on Combined Properties

Closed-cell rigid polyimide foams with excellent thermal stability and combined properties were prepared by thermal foaming of a reactive end-capped polyimide precursor powder in a closed mold. The precursor powder was obtained by thermal treatment of a polyester-amine salt (PEAS) solution derived from the reaction of the diethyl ester of 2,3,3′,4′-biphenyl tetracarboxylic dianhydride (α-BPDE) with an aromatic diamine mixture of p-phenylenediamine (PDA) and 2-(4-aminophenyl)-5-aminobenzimidazole (BIA) in the presence of an end-capping agent (mono-ethyl ester of nadic acid anhydride, NE) in an aliphatic alcohol. The effect of polymer mainchain structures on the foaming processability and combined properties of the closed-cell rigid polyimide foams were systematically investigated. The polyimide foams (100–300 kg/m3) with closed-cell rates of 91–95% show an outstanding thermal stability with an initial thermal decomposition temperature of ≥490 °C and a glass transition temperature of 395 °C. Polyimide foams with density of 250 kg/m3 exhibited compression creep deformation as low as 1.6% after thermal aging at 320 °C/0.4 MPa for 2 h.

CPExtract, a Software for the Automated Tracer-Based Pathway Specific Screening of Secondary Metabolites in LC-HRMS Data

The use of stable isotopically labeled tracers is a long-proven way of specifically detecting and tracking derived metabolites through a metabolic network of interest. While recently developed stable isotope assisted methods and associated, supporting data analysis tools have greatly improved untargeted metabolomics approaches, no software tool is currently available that allows to automatically search LC-HRMS chromatograms for completely free user-definable isotopolog patterns expected for the metabolism of labeled tracer substances. Here we present Custom Pattern Extract (CPExtract), a versatile software tool that allows for the first time the high-throughput search for user-defined isotopolog patterns in LC-HRMS data. The patterns can be specified via a set of rules including the presence or absence of certain isotopologs, their relative intensity ratios as well as chromatographic co-elution. Each isotopolog pattern satisfying the respective rules is verified on a MS-scan level and also in the chromatographic domain. The CPExtract algorithm allows the use of both labeled tracer compounds in non-labeled biological samples as well as a reversed tracer approach, employing non-labeled tracer compounds along with globally labeled biological samples. In a proof of concept study we searched for metabolites specifically arising from the malonate pathway of the filamentous fungi Fusarium graminearum and Trichoderma reesei. 1,2,3- 13 C 3 -malonic acid diethyl ester and native malonic acid monomethyl ester were used as tracers. We were able to reliably detect expected fatty acids and known polyketides. In addition, up to 189 and 270 further, unknown metabolites presumably including novel polyketides were detected in the F. graminearum and T. reesei culture samples respectively, all of which exhibited the user-predicted isotopolog patterns originating from the malonate tracer incorporation. The software can be used for every conceivable tracer approach. Furthermore, the rule sets can be easily adapted or extended if necessary. CPExtract is available free of charge for non-commercial use at https://metabolomics-ifa.boku.ac.at/CPExtract.

In Silico and In Vitro Screening of Antipathogenic Properties of Melianthus comosus (Vahl) against Pseudomonas aeruginosa

Bacterial quorum sensing (QS) system regulates pathogenesis, virulence, and biofilm formation, and together they contribute to nosocomial infections. Opportunistic pathogens, such as Pseudomonas aeruginosa, rely on QS for regulating virulence factors. Therefore, blocking the QS system may aid management of various infectious diseases caused by human pathogens. Plant secondary metabolites can thwart bacterial colonization and virulence. As such, this study was undertaken to evaluate three extracts from the medicinal plant, Melianthus comosus, from which phytochemical compounds were identified with potential to inhibit QS-dependent virulence factors in P. aeruginosa. Chemical profiling of the three extracts identified 1,2-benzene dicarboxylic acid, diethyl ester, neophytadiene and hexadecanoic acid as the common compounds. Validation of antibacterial activity confirmed the same MIC values of 0.78 mg/mL for aqueous, methanol and dichloromethane extracts while selected guanosine showed MIC 0.031 mg/mL. Molecular docking analysis showed anti-quorum sensing (AQS) potential of guanosine binding to CviR’ and 2UV0 proteins with varying docking scores of −5.969 and −8.376 kcal/mol, respectively. Guanosine inhibited biofilm cell attachment and biofilm development at 78.88% and 34.85%, respectively. Significant swimming and swarming motility restriction of P. aeruginosa were observed at the highest concentration of plant extracts and guanosine. Overall, guanosine revealed the best swarming motility restrictions. M. comosus extracts and guanosine have shown clear antibacterial effects and subsequent reduction of QS-dependent virulence activities against P.aeruginosa. Therefore, they could be ideal candidates in the search for antipathogenic drugs to combat P.aeruginosa infections.

d-Cystine di(m)ethyl ester reverses the deleterious effects of morphine on ventilation and arterial blood gas chemistry while promoting antinociception

We have identified thiolesters that reverse the negative effects of opioids on breathing without compromising antinociception. Here we report the effects of d-cystine diethyl ester (d-cystine diEE) or d-cystine dimethyl ester (d-cystine diME) on morphine-induced changes in ventilation, arterial-blood gas chemistry, A-a gradient (index of gas-exchange in the lungs) and antinociception in freely moving rats. Injection of morphine (10 mg/kg, IV) elicited negative effects on breathing (e.g., depression of tidal volume, minute ventilation, peak inspiratory flow, and inspiratory drive). Subsequent injection of d-cystine diEE (500 μmol/kg, IV) elicited an immediate and sustained reversal of these effects of morphine. Injection of morphine (10 mg/kg, IV) also elicited pronounced decreases in arterial blood pH, pO2 and sO2 accompanied by pronounced increases in pCO2 (all indicative of a decrease in ventilatory drive) and A-a gradient (mismatch in ventilation-perfusion in the lungs). These effects of morphine were reversed in an immediate and sustained fashion by d-cystine diME (500 μmol/kg, IV). Finally, the duration of morphine (5 and 10 mg/kg, IV) antinociception was augmented by d-cystine diEE. d-cystine diEE and d-cystine diME may be clinically useful agents that can effectively reverse the negative effects of morphine on breathing and gas-exchange in the lungs while promoting antinociception. Our study suggests that the d-cystine thiolesters are able to differentially modulate the intracellular signaling cascades that mediate morphine-induced ventilatory depression as opposed to those that mediate morphine-induced antinociception and sedation.

D-Cystine di(m)ethyl Ester Reverses the Deleterious Effects of Morphine on Ventilation and Arterial Blood Gas Chemistry While Promoting Analgesia

We have identified thiolesters that reverse the negative effects of opioids on breathing without compromising analgesia. Here we report the effects of D-cystine diethyl ester (D-cystine diEE) or D-cystine dimethyl ester (D-cystine diME) on morphine-induced changes in ventilation, arterial-blood gas chemistry, A-a gradient (index of gas-exchange in the lungs) and analgesia in freely moving rats. Injection of morphine (10 mg/kg, IV) elicited negative effects on breathing (e.g., depression of tidal volume, minute ventilation, peak inspiratory flow, and inspiratory drive). Subsequent injection of D-cystine diEE (500 mmol/kg, IV) elicited an immediate and sustained reversal of these effects of morphine. Injection of morphine (10 mg/kg, IV) also elicited pronounced decreases in arterial blood pH, pO2 and sO2 accompanied by pronounced increases in pCO2 (all indicative of a decrease in ventilatory drive) and A-a gradient (mismatch in ventilation-perfusion in the lungs). These effects of morphine were reversed in an immediate and sustained fashion by D-cystine diME (500 mmol/kg, IV). Finally, the duration of morphine (5 and 10 mg/kg, IV) analgesia was augmented by D-cystine diEE. D-cystine diEE and D-cystine diME may be clinically useful agents that can effectively reverse the negative effects of morphine on breathing and gas-exchange in the lungs while promoting analgesia.

Performance and Emission of B100 Biodiesel with Various Additives in Direct Injection Diesel Engine

Alternative fuels for diesel engines have become highly important in the automotive industry due to the depleting fossil fuel sources and increased environmental concerns. Biodiesel fuel has a good combustion characteristic because of their long-chain hydrocarbon structure but the higher density and viscosity of the fuel can contribute to several engine problems such as low atomization, carbon deposit formation and injector clogging. The production of biodiesel with additives can help with the performance and emissions of diesel engines. There are many types of additives on the market but the extent of the additives on engine performance is unknown and lack of research has been done in studying the performance, emissions and fuel consumption together with B100 biodiesel. In this research, there are five types of B100 palm oil methyl ester biodiesel with various additive compositions need to be identified. The density, viscosity and calorific value of biodiesel samples were measured to study the thermo-physical properties as a simulation input. Simulation of the combustion engine is conducted using CONVERGE CFD software; based on single-cylinder, direct injection, YANMAR TF90 diesel engine parameters to study on the combustion characteristics and exhaust emissions. The simulation results were compared with the experiment results. From the simulations, biodiesel with diethyl ester and n-butanol additives give better results compared to other additives because the present of n-butanol PME is believed to reduce CO, CO2 and NOx emissions while diethyl ether can improve the spray characteristics when it blends with B100 biodiesel due to its low density and viscosity.