Experimental methods in chemical engineering: X-ray absorption spectroscopy—XAS,XANES, EXAFS

Although X-ray absorption spectroscopy (XAS) was conceived in the early 20th century, it took 60 years after the advent of synchrotrons for researchers to exploit its tremendous potential. Counterintuitively, researchers are now developing bench type polychromatic X-ray sources that are less brilliant to measure catalyst stability and work with toxic substances. XAS measures the absorption spectra of electrons that X-rays eject from the tightly bound core electrons to the continuum. The spectrum from 10 to 150 eV (kinetic energy of the photoelectrons) above the chemical potential—binding energy of core electrons—identifies oxidation state and band occupancy (X-ray absorption near edge structure, XANES), while higher energies in the spectrum relate to local atomic structure like coordination number and distance, Debye-Waller factor, and inner potential correction (extended X-ray absorption fine structure, EXAFS). Combining XAS with complementary spectroscopic techniques like Raman, Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) elucidates the nature of the chemical bonds at the catalyst surface to better understand reaction mechanisms and intermediates. Because synchrotrons continue to be the light source of choice for most researchers, the number of articles Web of Science indexes per year has grown from 1000 in 1991 to 1700 in 2020. Material scientists and physical chemists publish an order of magnitude articles more than chemical engineers. Based on a bibliometric analysis, the research comprises five clusters centred around: electronic and optical properties, oxidation and hydrogenation catalysis, complementary analytical techniques like FTIR, nanoparticles and electrocatalysis, and iron, metals, and complexes.     

From miRNA Target Gene Network to miRNA Function: miR-375 Might Regulate Apoptosis and Actin Dynamics in the Heart Muscle via Rho-GTPases-Dependent Pathways

MicroRNAs (miRNAs) are short, single-stranded, non-coding ribonucleic acid (RNA) molecules, which are involved in the regulation of main biological processes, such as apoptosis or cell proliferation and differentiation, through sequence-specific interaction with target mRNAs. In this study, we propose a workflow for predicting miRNAs function by analyzing the structure of the network of their target genes. This workflow was applied to study the functional role of miR-375 in the heart muscle (myocardium), since this miRNA was previously shown to be associated with heart diseases, and data on its function in the myocardium are mostly unclear. We identified PIK3CA, RHOA, MAPK3, PAFAH1B1, CTNNB1, MYC, PRKCA, ERBB2, and CDC42 as key genes in the miR-375 regulated network and predicted the possible function of miR-375 in the heart muscle, consisting mainly in the regulation of the Rho-GTPases-dependent signaling pathways. We implemented our algorithm for miRNA function prediction into a Python module, which is available at GitHub.     

Complex modification effect of linseed cake as an agricultural waste filler used in high density polyethylene composites

Linseed cake (LC) is a by-product of agricultural industry which does not have any large-scale industrial applications. The possibilities of its utilization as filler with plasticizing ability for high density polyethylene (HDPE)-based composites have been investigated. Composites containing 5, 10, 20 and 30 wt% of the waste filler have been prepared using a melt mixing method. The influence of the LC on the mechanical and thermomechanical properties of the composites, as well as their water absorption and morphology, have been evaluated by the following methods: static tensile test, impact strength assessment using Dynstat method, hardness measurements, differential scanning calorimetry, dynamic mechanical thermal analysis, scanning electron microscopy observations, measurements of Vicat’s softening temperature and water uptake test. Application of different measuring techniques allows for describing complex modification effects of the composites’ properties changes induced by the presence of lignocellulosic filler with high oil content. The results of the study proved a pronounced influence of LC on high density polyethylene-based composites, especially a plasticizing effect of crude linseed oil contained by the waste filler particles. LC also has been assumed to affect the polymeric matrix crystallization process. It was found that complex modification of polyethylene results from simultaneously occurring different phenomena including: plasticization of the HDPE by linseed oil, improved crystallinity of the semicrystalline matrix, presence of the rigid lignocellulosic particles dispersed in polymer and accumulation of the oil in the interfacial regions.     

Experimental investigation of the dynamic behavior of railway track with sleeper voids

Railway Engineering Science - The deterioration of the sleeper support on the ballasted track begins with the accumulation of sleeper voids. The increased dynamic loading in the voided zone and the...     

Microbiological shelf life and sensory evaluation of fruit juices treated by high-intensity pulsed electric fields and antimicrobials

The effect of combining high-intensity pulsed electric fields (HIPEF) with citric acid or cinnamon bark oil, as antimicrobial substances, on the microbiological shelf life of strawberry, orange, apple, pear and tomato juices was evaluated in addition to the sensory properties of these products. An extension of the microbiological shelf life of fruit juices treated by HIPEF with or without antimicrobial substances was observed in comparison with those juices without processing. Naturally occurring microorganisms in the juices were inactivated by HIPEF treatment. Among the HIPEF treated juices, those from strawberry and orange did not show microbial growth along the 91 days of storage at 5 °C. However, resident microbial populations in apple, pear and tomato juices only were controlled during that time when HIPEF was combined with antimicrobials. Therefore, combinations of those treatments may be a feasible alternative to thermal pasteurization to ensure the microbiological quality and safety in juices, and to avoid the risk of foodborne illness caused by the consumption of these commodities. No significant changes on the sensory attributes in all studied fruit juices processed by HIPEF were found; but, when citric acid or cinnamon bark oil were added, noticeable changes on some sensory attributes such as aroma, taste and sourness of these fruit juices were perceived.     

Solutions of special type describing the three dimensional thermocapillary flows with an interface

The convective fluid flows with an interface are modeled using the classical Oberbeck–Boussinesq model of convection. The three dimensional solutions for the infinite domains with fixed heat-insulated boundaries and with the interface under action of a longitudinal temperature gradient are studied. Construction of the solutions for the flows of two immiscible fluids in a channel with a rectangular cross-section is carried out using a complete problem statement. The kinematic and dynamic conditions are prescribed at the interface. The additional condition of continuity of the tangential velocities, the conditions of continuity of temperature and of the thermal fluxes are assumed to be fulfilled on the interface. In the present paper the fluid flows are studied in the stationary case under conditions of gravity and microgravity. To investigate this problem numerically an iteration algorithm is introduced. This algorithm is based on a finite difference scheme (the alternating direction method) and it allows to find all the components of velocity for both phases and temperature distributions. The examples of flows which can be characterized as a combination of the translational and progressively rotational types of motion are presented.     

Löschen im Internet – rechtlich gefordert und technisch möglich!

Die im Art. 17 der Datenschutz-Grundverordnung (DSGVO) enthaltene Regelungen für das Löschen, insbesondere die Pflicht, Dritte über die Löschanfragen zu informieren, sind mit einem hohen Aufwand für die Verantwortlichen verbunden, sodaßs sie ohne eine technische Unterstützung in der Praxis nicht umgesetzt werden können. Die zurzeit jedoch fehlenden technischen Lösungen führen zu einer Lücke zwischen den Rechtsvorschriften und den derzeitigen technischen Möglichkeiten, während die DSGVO ab Mai 2018 anzuwenden ist. Um diese Lücke zu schließen, wird im Folgenden zunächst analysiert, welche Möglichkeiten im Allgemeinen bestehen, das Löschen im Internet gemäß Art. 17 technisch umzusetzen. Anschließend wird eine Lösung für die Verteilung der Löschanfragen an die Verantwortlichen vorgestellt, das auf der Kombination der Technik mit dem Gesetz beruht und sowohl den Betroffenen als auch den Verantwortlichen ein Werkzeug zur Unterstützung des Art. 17 zur Verfügung stellt.     

Protein-ion Interactions: Simulations of Bovine Serum Albumin in Physiological Solutions of NaCl,KCl and LiCl

Specific interactions that depend on the nature of electrolytes are observed when proteins and other molecules are studied by potentiometric, spectroscopic and theoretical methods at high salt concentrations. More recently, it became clear that such interactions may also be observed in solutions that can be described by the Debye-Hückel theory, i.e., at physiological (0.1 mol dm⁻³) and lower concentrations. We carried out molecular dynamics simulations of bovine serum albumin in physiological solutions at T=300 and 350 K. Analysis of the simulations revealed some differences between LiCl solutions and those of NaCl and KCl. The binding of Li⁺ ions to the protein was associated with a negative free energy of interaction whereas much fewer Na⁺ and K⁺ ions were associated with the protein surface. Interestingly, unlike other proteins BSA does not show a preference to Na⁺ over K⁺. Quantum chemical calculations identified a significant contribution from polarisation to the hydration of Li⁺ and (to a lesser degree) Na⁺, which may indicate that polarisable force-fields will provide more accurate results for such systems.