Removal of toxic metals from aqueous mixtures. Part 1: Biosorption

The biosorption of toxic metals from an aqueous mixture containing zinc, copper and nickel, in the presence of calcium and sodium ions (usual co‐existing cations in related systems) has been investigated. Industrial biomass samples of different origin have been examined batchwise as effective sorbents, including bacteria (Streptomyces rimosus), fungi (Penicillium chrysogenum) and yeasts (Saccharomyces carlsbergensis and Saccharomyces cerevisiae). The effect of solution pH was evaluated in the range of 3–11.5. Selectivity was observed, particularly for the removal of copper. The observed removal of metals by the application of biosorption was also compared in laboratory experiments with other more conventional separation techniques (filtration, centrifugation and flotation). © 1999 Society of Chemical Industry     

Petascale large eddy simulation of jet engine noise based on the truncated SPIKE algorithm

With the emergence of petascale computing platforms, high-fidelity computational aeroacoustics (CAA) simulation has become a feasible, robust and accurate tool that complements theoretical and empirical approaches in the prediction of sound levels generated by aircraft airframes and engines. Differentiating itself from the broader discipline of computational fluid dynamics, CAA is particularly challenging as it demands high accuracy, good spectral resolution, and low dispersion and diffusion errors from the underlying numerical methods. Large eddy simulation based on space-implicit high-order compact finite difference schemes has been shown to meet such stringent requirements. In this paper, we discuss a new, scalable parallelization scheme with a three-dimensional computational space partitioning. Unlike many traditional multiblock computational fluid dynamics (CFD) methods, our partitioning is non-overlapping. We use the truncated SPIKE algorithm to solve the governing equations accurately and limit one-sided biased differentiation to just the physical boundaries. We present experimental performance data collected on Kraken and Ranger, two near-petascale computing platforms.     

βArrestins in Cardiac G Protein-Coupled Receptor Signaling and Function: Partners in Crime or “Good Cop,Bad Cop”?

βarrestin (βarr)-1 and -2 (βarrs) (or Arrestin-2 and -3, respectively) are universal G protein-coupled receptor (GPCR) adapter proteins expressed abundantly in extra-retinal tissues, including the myocardium. Both were discovered in the lab of the 2012 Nobel Prize in Chemistry co-laureate Robert Lefkowitz, initially as terminators of signaling from the β-adrenergic receptor (βAR), a process known as functional desensitization. They are now known to switch GPCR signaling from G protein-dependent to G protein-independent, which, in the case of βARs and angiotensin II type 1 receptor (AT₁R), might be beneficial, e.g., anti-apoptotic, for the heart. However, the specific role(s) of each βarr isoform in cardiac GPCR signaling and function (or dysfunction in disease), remain unknown. The current consensus is that, whereas both βarr isoforms can desensitize and internalize cardiac GPCRs, they play quite different (even opposing in certain instances) roles in the G protein-independent signaling pathways they initiate in the cardiovascular system, including in the myocardium. The present review will discuss the current knowledge in the field of βarrs and their roles in GPCR signaling and function in the heart, focusing on the three most important, for cardiac physiology, GPCR types (β₁AR, β₂AR & AT₁R), and will also highlight important questions that currently remain unanswered.     

Mathematical modeling of diffusion‐controlled free‐radical terpolymerization reactions

A comprehensive mathematical model is developed to describe the kinetics and molecular and compositional developments in a free‐radical terpolymerization batch reactor. This model is based on a fairly general kinetic mechanism, including chain‐transfer and terminal double‐bond reactions. We take into account the effects of diffusion‐controlled phenomena (i.e., gel, glass, and cage effects) on polymerization kinetics by extending our previous model on diffusion‐controlled reactions to terpolymerization systems. Triple moments for the live and dead trivariate chain‐length terpolymer composition distributions are introduced to describe the molecular and compositional developments in the terpolymerization system. The predictive capabilities of this model are demonstrated by simulation of the free‐radical, bulk terpolymerization of butyl acrylate/methyl methacrylate/vinyl acetate under different experimental conditions. It is shown that the model predictions are in good agreement with experimental data on monomer conversion, average molecular weights, and terpolymer composition, as reported by Dube and Penlidis. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 161–176, 2003     

Short-Chain Fatty Acid Receptors and Cardiovascular Function

Increasing experimental and clinical evidence points toward a very important role for the gut microbiome and its associated metabolism in human health and disease, including in cardiovascular disorders. Free fatty acids (FFAs) are metabolically produced and utilized as energy substrates during almost every biological process in the human body. Contrary to long- and medium-chain FFAs, which are mainly synthesized from dietary triglycerides, short-chain FFAs (SCFAs) derive from the gut microbiota-mediated fermentation of indigestible dietary fiber. Originally thought to serve only as energy sources, FFAs are now known to act as ligands for a specific group of cell surface receptors called FFA receptors (FFARs), thereby inducing intracellular signaling to exert a variety of cellular and tissue effects. All FFARs are G protein-coupled receptors (GPCRs) that play integral roles in the regulation of metabolism, immunity, inflammation, hormone/neurotransmitter secretion, etc. Four different FFAR types are known to date, with FFAR1 (formerly known as GPR40) and FFAR4 (formerly known as GPR120) mediating long- and medium-chain FFA actions, while FFAR3 (formerly GPR41) and FFAR2 (formerly GPR43) are essentially the SCFA receptors (SCFARs), responding to all SCFAs, including acetic acid, propionic acid, and butyric acid. As with various other organ systems/tissues, the important roles the SCFARs (FFAR2 and FFAR3) play in physiology and in various disorders of the cardiovascular system have been revealed over the last fifteen years. In this review, we discuss the cardiovascular implications of some key (patho)physiological functions of SCFAR signaling pathways, particularly those regulating the neurohormonal control of circulation and adipose tissue homeostasis. Wherever appropriate, we also highlight the potential of these receptors as therapeutic targets for cardiovascular disorders.     

Study on polymer solutions in solvent mixtures in the vicinity of the critical point of the solvents: 4. Saturation phenomena

Turbidimetric results have been obtained with the ternary system N,N-dimethylformamide/cyclohexane/polystyrene. The displacement of the heterogeneous region depends on the molecular weight of the polystyrene sample and for each polystyrene sample the displacement changes with the concentration of the polymer. Above a certain molecular weight of the polymer, with a given concentration, the displacement reaches a plateau region. A plateau is also obtained when we change the concentration of the polymer of a given molecular weight. The crossover region, which is determined by the appearance of the plateau region, obeys the scaling laws and is probably the region where the distance between the macromolecular coils is comparable to their diameters.     

Synthesis,physical and thermal characterization of phosphorus-containing homopolymers and copolymers based on 2,4-bis(4-aminophenoxy)-6-diethoxyphosphinyl-s-triazine

Novel phosphorus-containing homopolyimides, homopolyamides, and homopolyureas were prepared by reacting 2,4-bis(4-aminophenoxy)-6-diethoxyphosphinyl-s-triazine (BADT) with pyromellitic or benzophenone tetracarboxylic dianhydride, terephthaloyl chloride, and tolylene diisocyanate, respectively. In addition, the corresponding copolymers that contained approximately 3% phosphorus were prepared by reacting BADT and 4,4′-diaminodiphenyl sulfone with the aforementioned reagents. These polymers were characterized by inherent viscosity measurements, infrared (IR) and proton nuclear magnetic resonance (¹H-NMR) spectroscopy as well as by differential thermal analysis (DTA) and dynamic thermogravimetric analysis (TGA). Their thermal properties were compared with those of the corresponding nonphosphorylated polymers. The copolymers were stable up to 233–272°C in nitrogen or air atmosphere. The homopolymers showed a relatively lower thermal stability. Furthermore, a model diimide, diamide, and diurea were synthesized from the reactions of BADT with phthalic anhydride, benzoyl chloride, and phenyl isocyanate, respectively. The physical and thermal characteristics of these model compounds were correlated with those of the corresponding homopolymers.     

Structure-borne noise generation and transmission

The structure-borne noise generation and transmission of stiffened and interconnected structures under random loads is presented. The method is based on the transfer matrix for the structural response and on the modal decomposition for the interior acoustic field. The acoustic enclosure is taken to be rectangular in shape of which portion of the boundaries are elastic while the remaining surface is acoustically rigid. Numerical results are presented for a variety of acousto-structural problems.     

A scale for monitoring students’ attitudes to learning mathematics with technology

The Mathematics and Technology Attitudes Scale (MTAS) is a simple scale for middle secondary years students that monitors five affective variables relevant to learning mathematics with technology. The subscales measure mathematics confidence, confidence with technology, attitude to learning mathematics with technology and two aspects of engagement in learning mathematics. The paper presents a model of how technology use can enhance mathematics achievement, a review of other instruments and a psychometric analysis of the MTAS. It also reports the responses of 350 students from 6 schools to demonstrate the power of the MTAS to provide useful insights for teachers and researchers. ‘Attitude to learning mathematics with technology’ had a wider range of scores than other variables studied. For boys, this attitude is correlated only with confidence in using technology, but for girls the only relationship found was a negative correlation with mathematics confidence. These differences need to be taken into account when planning instruction.