Kinetics and mass transfer in hydroformylation—bulk or film reaction?

The kinetics of a gas–liquid reaction, alkene hydroformylation was studied in the presence of a homogeneous catalyst in a pressurised laboratory‐scale semibatch reactor. Hydroformylation of propene to isobutyraldehyde and n‐butyraldehyde was carried out at 70–115°C and 1–15 bar pressure in 2,2,4‐trimethyl‐1,3‐pentanediol monoisobutyrate solvent with rhodium catalyst using the ligands cyclohexyl diphenylphosphine. In order to evaluate the influence of mass transfer, experiments were made using varied stirring rate from 100 to 1000 rpm at 100°C and 10 MPa syngas pressure. Only at higher stirrings rates, the reaction took place in the kinetic regime. A reactor model was developed comprising both complex kinetics and liquid‐phase mass transfer. The model was based on the theory of reactive films. The model is able to predict under which circumstances the hydroformylation process is affected by liquid‐phase diffusion of the reactants. Experimental data and model simulations are presented for the hydroformylation of propene in the presence of a homogeneous rhodium catalyst.     

Drag reduction by DNA-grafting for single microspheres in a dilute λ-DNA solution

The fluid resistance of single micrometre-sized blank and DNA-grafted polystyrene microspheres under shear flow is compared in purified water and dilute λ-DNA solutions by means of optical tweezers experiments with a high spatial (±4 nm) and temporal (±0.2 ms) resolution. The measurement results show that the drag experienced by a colloid in a dilute λ-DNA solution (molecular weight of 48,502 bp per molecule, radius of gyration of 0.5 μm) is significantly decreased if the microsphere bears a grafted DNA brush. This newly discovered drag reduction effect is studied for different parameters, comprising the molecular weight of the grafted DNA molecules (250 bp, 1000 bp and 4000 bp), the concentration of the λ-DNA solution (11, 17 and 23 μg ml^?1, all being significantly smaller than the critical entanglement concentration c¹), the microsphere core diameter (2 μm, 3 μm and 6 μm) as well as the flow speed of the medium (10–50 μm s^?1). The maximum extent of the drag reduction is found to amount to (60 ± 20)% compared to the λ-DNA-induced contribution on the drag acting on blank colloids. We propose a theoretical explanation of this effect based on the combination of the dynamic density functional theory of Rauscher and co-workers [Rauscher M. J. Phys.: Condens. Matter 2010;22:364109] and the stagnation length theory of polymer brushes, as it was established by Kim, Lobaskin et al. [Kim et al. Macromolecules 2008;42(10):3650–3655]. In particular, the solution of the Stokes equation (i.e., the Navier–Stokes equation for creeping flow) for the studied system yields a numerical prediction that is found to be in full accord with our experimental results within measurement uncertainty.     

Solvent‐induced crystallization in polyetheretherketone exposed to methylene chloride—during solvent sorption or during solvent desorption?

The phenomenon of solvent‐induced crystallization observed in some polymer–solvent pair was well documented. It is generally believed that solvent‐induced crystallization occurs during sorption of the solvent. However, this is actually a hypothesis and needs to be proven. To clarify the true situation, the present article investigates crystalline structural variation of polyetheretherketone before and after treatment of methylene chloride. The results indicate that crystallization of the polymer was induced by the solvent mainly when the solvent was desorbed. The possible mechanism is discussed in the light of molecular motion. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3376–3379, 1999     

A semi-empirical model for the drag force and fluid–particle interaction in polydisperse suspensions

Fluid flow through stationary or moving particle beds is a common process in industrial units. The two-phase hydrodynamics strongly influences the performances and characteristics of reactors and contactors in general, but the possibility to model comprehensively the details of the two-phase field of motion still lacks. Computational methods and multi-scale modeling are capable of providing essential information at the microscopic scale. In the present paper, recently published data on the fluid–particle interaction obtained at the sub-particle scale are used to propose a semi-empirical model for the calculation of the fluid–particle interaction, named the basis of computer simulations of fluid–solid flows. The proposed approach starts from flow through monodisperse particle beds and leads to a general expression valid over a very wide range of Reynolds’ number and porosity and, most notably, accounts for polydispersion in a consistent and general way. Available actual drag force data from lattice-Boltzmann simulations for mono- and bi-disperse systems are fitted by a physically consistent and computationally efficient model, obtaining a very good agreement over a broad range of conditions. The resulting model is validated both against lattice-Boltzmann simulations involving ten different species and against experimental measurements in real two-component beds fluidized by a liquid exhibiting the layer inversion phenomenon. The model is shown to predict well the correct values under a significant variability of operating conditions. Finally a discussion of the application of the model in the context of numerical simulations is presented.     

The Treatment of Dyslipidemia—What's Left in the Pipeline?

Dyslipidemia is a pathological alteration of serum lipid levels. The most common forms are either elevations of triglycerides or low density lipoprotein cholesterol associated with a reduction of high density lipoprotein cholesterol. Most frequently both forms of lipid disorders are combined. Elevations of free fatty acid blood levels are commonly not subsumed under the term dyslipidemia. However, free fatty acids should also be considered, as they are frequently associated with dyslipidemia and represent a risk factor for cardiovascular diseases. Dyslipidemias are among the major etiologic factors for arterial occlusive diseases. Resulting in fatal implications such as stroke and coronary heart disease, dyslipidemias contribute to the most prevalent causes of death. Lowering of low density lipoprotein and raising of high density lipoprotein cholesterol levels have been shown in both epidemiologic and intervention studies to decrease mortality. Established treatments of dyslipidemias are statins and fibrates. However, recent research has established some new potential therapeutic targets which are currently investigated in clinical trials. New therapeutic approaches include subtype selective, dual, and pan-agonists of the peroxisome proliferator activated receptor, inhibitors of the cholesterol ester transfer protein, Acyl-CoA-cholesterol-acyltransferase, squalene synthase, microsomal triglycerid-transfer-protein, and cholesterol absorption. Clinical implications of new drugs under investigation are discussed in this review.     

KLK3 in the Regulation of Angiogenesis—Tumorigenic or Not?

In this focused review, we address the role of the kallikrein-related peptidase 3 (KLK3), also known as prostate-specific antigen (PSA), in the regulation of angiogenesis. Early studies suggest that KLK3 is able to inhibit angiogenic processes, which is most likely dependent on its proteolytic activity. However, more recent evidence suggests that KLK3 may also have an opposite role, mediated by the ability of KLK3 to activate the (lymph)angiogenic vascular endothelial growth factors VEGF-C and VEGF-D, further discussed in the review.     

Is there value in chemical modification of fish scale surfaces?

Fish scales are an abundant biowaste apparently unused, except for isolating major components as feedstocks, sacrificing the useful properties inherent to scales. We modified scale surfaces using hydrophilic and hydrophobic (meth)acrylates and tetraethylorthosilicate with in situ polymerization, and partial degradation of the biomineral or collagen layer. Chemical changes were assessed qualitatively by Fourier‐transform infrared spectroscopy and quantitatively by nanomechanical analysis. No modification was selective but they were “preferential”. Hydrophobic modifications were inefficient and reduced scale modulus. Inorganic and hydrophilic modifications were efficient and increased modulus. On adding sodium‐citrate‐modified scales to a weak alginate hydrogel, rheology showed an order of magnitude increase in storage modulus compared to alginate with no or unmodified scale reinforcement. Fish scales can be a useful new reinforcement. This work highlights simple pathways to manipulate surface composition and modulus of waste fish scale to enhance composite properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42868.     

Textile research and development in the UK – success or failure?

Although initially lagging behind the USA, the amount and quality of research and development carried out in the UK can be compared favourably with that from other major world countries. The industrial research association, although a well‐conceived concept to increase research and development efforts that gave significant results, was disappointing for several reasons. A major problem has been the dissemination, exploitation and commercialisation of research results. The activities of research organisations need to be reviewed regularly, as they may have a relatively short lifespan. The intermediate research and technology sector, given adequate support, may be the vehicle for better utilisation of research and development results.     

Microglia–Neuron Crosstalk in Obesity: Melodious Interaction or Kiss of Death?

Diet-induced obesity can originate from the dysregulated activity of hypothalamic neuronal circuits, which are critical for the regulation of body weight and food intake. The exact mechanisms underlying such neuronal defects are not yet fully understood, but a maladaptive cross-talk between neurons and surrounding microglial is likely to be a contributing factor. Functional and anatomical connections between microglia and hypothalamic neuronal cells are at the core of how the brain orchestrates changes in the body’s metabolic needs. However, such a melodious interaction may become maladaptive in response to prolonged diet-induced metabolic stress, thereby causing overfeeding, body weight gain, and systemic metabolic perturbations. From this perspective, we critically discuss emerging molecular and cellular underpinnings of microglia–neuron communication in the hypothalamic neuronal circuits implicated in energy balance regulation. We explore whether changes in this intercellular dialogue induced by metabolic stress may serve as a protective neuronal mechanism or contribute to disease establishment and progression. Our analysis provides a framework for future mechanistic studies that will facilitate progress into both the etiology and treatments of metabolic disorders.     

Discussion on magnetic-induced polarization Ampere’s force by in situ observing the special particle growth of alumina during microwave sintering

Internal microstructure evolution during alumina microwave sintering was in situ investigated with synchrotron radiation computed tomography (SR-CT). Two special microstructure evolution phenomena were continuously observed from the experimental images of the sample at different sintering times throughout the entire process of the sintering, which we called “suppressed particle growth” and “particle homogenization”. These two special phenomena were further confirmed by the two curves of “average particle radius” and “particle radius standard deviation” versus sintering time which were directly extracted from the full-field SR-CT results. A polarization Ampere’s force model was proposed to provide a possible explanation for these special phenomena, which introduced the effect of magnetic field on insulating ceramic materials, a topic rarely discussed in previous studies. The polarization Ampere’s force model may explain these two special sintering phenomena observed in the in situ experiment. On one hand, ceramic particles may sustain “Ampere’s force” that pointed toward the particle center according to this model, thereby possibly leading to the special suppressed-particle-growth phenomenon; on the other hand, large particles may sustain a strong force in our model, which may explain the other special phenomenon of particle homogenization. In return, these two special phenomena can also serve as probable experimental evidence of our polarization Ampere’s force model. This study may offer some help for revealing the complex mechanisms during microwave sintering and for preparing materials with expected microstructure and excellent properties.     

Toluenediamine in polyurethane foams Hazard or artefact?

Abstract

The aim of this study was to investigate the formation of the suspected carcinogen toluenediamine (TDA) as a degradation product of polyurethane. For this purpose, a series of model systems was prepared, including linear polyurethanes and foams. The starting materials were fully characterised using melting point and refractive index determination, end group analysis, infrared spectroscopy, nuclear magnetic resonance spectroscopy and coupled gas chromatography–mass spectrometry (GC–MS). A model commercial polyurethane foam was also prepared. Three different solvent extraction protocols were applied and the extracts analysed by coupled GC–MS and high performance liquid chromatography–mass spectrometry. No detectable amounts of TDA could be found in extracts of both linear polyurethane and foam incubated using either toluene or 1% acetic acid solution. By contrast, TDA was found in extracts from both linear polyurethane and foam that had been exposed to alkaline conditions during the extraction procedure. These findings confirm that the formation of TDA in extraction and GC–MS analysis of polyurethane samples results from hydrolytic degradation processes of polyurethane and that alkaline conditions should be avoided during extraction and analysis.     

Designing Irreversible Inhibitors—Worth the Effort?

Despite the unquestionable success of numerous irreversible drugs that are currently in clinical use, such as acetylsalicylic acid (Aspirin) and penicillin, the number of such approved drugs is much lower than that of noncovalent drugs. Over the years, the potential off‐target effects of these types of compounds have been the primary concern that has hampered their development. However, their remarkable advantages over noncovalent drugs and a better analysis of the risks have decreased the widespread skepticism surrounding them. The design of irreversible inhibitors is a challenge, particularly considering that in some cases their efficacy is due to complex and unexpected mechanisms of action. In this review the main advantages of irreversible inhibition are summarized, and the complexity of certain covalent modification mechanisms is highlighted with selected examples.     

Miniplants — Ein Beitrag zur inhärenten Sicherheit?

The scale minimisation of a chemical plant can increase its safety almost to the inherent safety level because the amounts of hazardous substances are greatly reduced. Because of the small amounts of hazardous substances usually present, miniplants, which have proved themselves in research and development, do not pose a serious danger to the environment. With regard to inherent safety, two concepts are presented which could help to avoid problems encountered in storage and transportation of hazardous substances and to lessen the hazardous potential of a chemical plant.     

Zinc in the Brain: Friend or Foe?

Zinc is a trace metal ion in the central nervous system that plays important biological roles, such as in catalysis, structure, and regulation. It contributes to antioxidant function and the proper functioning of the immune system. In view of these characteristics of zinc, it plays an important role in neurophysiology, which leads to cell growth and cell proliferation. However, after brain disease, excessively released and accumulated zinc ions cause neurotoxic damage to postsynaptic neurons. On the other hand, zinc deficiency induces degeneration and cognitive decline disorders, such as increased neuronal death and decreased learning and memory. Given the importance of balance in this context, zinc is a biological component that plays an important physiological role in the central nervous system, but a pathophysiological role in major neurological disorders. In this review, we focus on the multiple roles of zinc in the brain.