The Lise Meitner-Minerva Center for Computational Quantum Chemistry: 18 Years of Israeli-German Collaboration

We tell the story of the Lise Meitner-Minerva Center, its establishment and activities, its members and their scientific activity, and its instrumental role in weaving intense relationships with the theoretical community in Germany, and in amalgamating the Israeli community of computational quantum chemistry into a national center that enjoys a high international reputation.     

Peptide nanotube-modified electrodes for enzyme-biosensor applications

The fabrication and notably improved performance of composite electrodes based on modified self-assembled diphenylalanine peptide nanotubes is described. Peptide nanotubes were attached to gold electrodes, and we studied the resulting electrochemical behavior using cyclic voltammetry and chronoamperometry. The peptide nanotube-based electrodes demonstrated a direct and unmediated response to hydrogen peroxide and NADH at a potential of +0.4 V (vs SCE). This biosensor enables a sensitive determination of glucose by monitoring the hydrogen peroxide produced by an enzymatic reaction between the glucose oxidase attached to the peptide nanotubes and glucose. In addition, the marked electrocatalytic activity toward NADH enabled a sensitive detection of ethanol using ethanol dehydrogenase and NAD+. The peptide nanotube-based amperometric biosensor provides a potential new tool for sensitive biosensors and biomolecular diagnostics.     

Effect of carrier fluid viscosity on retention time and resolution in gravitational field-flow fractionation

Gravitational field-flow fractionation (GrFFF) is a useful technique for fast separation of micrometer-sized particles. Different sized particles are carried at different velocities by a flow of fluid along an unobstructed thin channel, resulting in a size-based separation. They are confined to thin focused layers in the channel thickness where force due to gravity is exactly opposed by hydrodynamic lift forces (HLF). It has been reported that the HLF are a function of various parameters including the flow rate (or shear rate), the size of the particles, and the density and viscosity of the liquid. The dependence of HLF on these parameters offers a means of altering the equilibrium transverse positions of the particles in GrFFF, and hence their elution times. In this study, the effect of the viscosity of the carrier fluid on the elution behavior (retention, zone broadening, and resolution) of micrometer-sized particles in GrFFF was investigated using polystyrene (PS) latex beads as model particles. In order to change the carrier liquid viscosity without affecting its density, various amounts of (hydroxypropyl) methyl cellulose (HPMC) were added to the aqueous carrier liquid. It was found that particles migrate at faster rates as the carrier viscosity is increased, which confirms the dependence of HLF on viscosity. At the same time, particle size selectivity decreased but peak shape and symmetry for the more strongly retained particles improved. As a result, separation was improved in terms of both the separation time and resolution with increase of carrier viscosity. A theoretical model for plate height in GrFFF is also presented, and its predictions are compared to experimentally measured values.     

Relation between the quantity, type and duration of alcohol drinking and the development of alcoholic liver cirrhosis

Patients with alcoholic liver cirrhosis in Dalmatian region are presented in this paper and their social and medical characteristics are reviewed. The alcohol drinking habits of 211 patients with established clinical-laboratory criteria of alcoholic liver cirrhosis were investigated. The obtained results have been compared with the results of the control group. The average age of the patients was 51.6 years. Males were more numerous (2/3 of all examinees), while the average duration of alcohol consumption was 25.4 years. Wine was the most frequently consumed beverage (about 90% of cases) and the average daily intake was 151 g of pure alcohol. The authors prove by mathematical model that the occurrence of liver cirrhosis increases exponentially with the increase of the amount of alcohol consumed. Relative risk of the development of alcoholic liver cirrhosis increases many fold with the increase of the amount of alcohol consumed.     

Efficient identity-based security schemes for ad hoc network routing protocols

Wireless ad hoc networks consist of nodes with no central administration and rely on the participating nodes to share network responsibilities. Such networks are more vulnerable to security attacks than conventional wireless networks. We propose two efficient security schemes for these networks that use pairwise symmetric keys computed non-interactively by the nodes which reduces communication overhead. We allow nodes to generate their broadcast keys for different groups and propose a collision-free method for computing such keys. We use identity-based keys that do not require certificates which simplifies key management. Our key escrow free scheme also uses identity-based keys but eliminates inherent key escrow in identity-based keys. Our system requires a minimum number of keys to be generated by the third party as compared to conventional pairwise schemes. We also propose an authenticated broadcast scheme based on symmetric keys and a corresponding signature scheme.     

Imaging food freezing using X-ray microtomography

X‐ray micro‐computed tomography (X‐ray micro‐CT) has been applied to visualise ice crystal structures formed during freezing of a number of foods. Materials were frozen unidirectionally at ?5 °C and then freeze‐dried to remove the ice crystal structure and leave voids that can be measured by the X‐ray. The system reconstructs the 3‐D image based on a set of 2‐D images, and is capable of micrometre‐scale visualisation. This study demonstrates the capability of the technique to characterise the internal ice crystal microstructure of a range of frozen materials; meat, fish, chicken, potato, cheese and carrot. Results show the voids corresponding to the ice crystals formed within these materials at different directions to the heat flux and various axial positions. Electron microscopy of the same materials, both fresh and frozen at ?5 °C, indicates the same shape of voids seen by the tomographic technique. Ice crystal parameters such as size, area and width can be quantified by the technique. Ice crystals in carrot were larger than in the other materials, while cheese and potato had the lowest values. The ice crystal distribution of all the experimental materials varied with axial distance from cooling surface; the closer the measurement was to the cooling surface, the smaller the crystal size. The results demonstrate that X‐ray micro‐CT might be useful in the analysis of frozen foods.     

Flow induced fibre alignment in Mycoprotein paste

The effects of extrusion and squeeze flow processing on the microstructure of Mycoprotein filamentous paste, a novel meat product alternative, are investigated. The flow induced effects are quantified in terms of fibre orientation measured by a technique of fluorescence microscopy and image analysis. Imaging of the original mycelia fibre paste showed that its microstructure is ‘isotropic’. Squeezing of the native paste does not result in any significant fibre rearrangement. This is attributed to the high fibre concentration and, thus, high level of fibre entanglement in the squeezed film, and slip at the wall. A semi-concentrated suspension of mycelia fibres in a golden syrup matrix, however, shows considerable structural rearrangement throughout. Extrusion of the native paste leads to a high degree of fibre alignment in the direction of flow with a high proportion of the fibre population (80–90%) being realigned. An Exponential-Uniform Mix distribution was successfully used to describe fibre orientation in both extrusion and squeeze flow. The results show the strong link between the microstructure of highly structured food products and the mode of processing used. They may also have important implications for the rheological testing of such structurally complex materials, as the rheological response of the material may well dependent on the way it is made to interact with the instrument.     

Electric vehicle energy consumption modelling and estimation—A case study

Electric vehicles (EVs) have a limited driving range compared to conventional vehicles. Accurate estimation of EV's range is therefore a significant need to eliminate “range anxiety” that refers to drivers' fear of running out of energy while driving. However, the range estimators used in the currently available EVs are not sufficiently accurate. To overcome this issue, more accurate range estimation techniques are investigated. Nonetheless, an accurate power‐based EV energy consumption model is crucial to obtain a precise range estimation. This paper describes a study on EV energy consumption modelling. For this purpose, EV modelling is carried out using MATLAB/Simulink software based on a real EV in the market, the BMW i3. The EV model includes vehicle powertrain system and longitudinal vehicle dynamics. The powertrain is modelled using efficiency maps of the electric motor and the power electronics' data available for BMW i3. It also includes a transmission and a battery model (ie, Thevenin equivalent circuit model). A driver model is developed as well to control the vehicle's speed and to represent human driver's behaviour. In addition, a regenerative braking strategy, based on a series brake system, is developed to model the behaviour of a real braking controller. Auxiliary devices are also included in the EV model to improve energy consumption estimation accuracy as they can have a significant impact on that. The vehicle model is validated against published energy consumption values that demonstrates a satisfactory level of accuracy with 2% to 6% error between simulation and experimental results for Environmental Protection Agency and NEDC tests.     

Electrically conductive polycarbonate/ethylene‐propylene copolymer/multi‐walled carbon nanotubes nanocomposites with improved mechanical properties

In this article, the effect of Multi‐walled carbon nanotubes (MWCNTs) on the electrical conductivity and mechanical properties of polycarbonate (PC) toughened with cross‐linked ethylene‐propylene copolymer (EPC) was investigated. The solubility parameters of the PC and EPC were calculated using Hoy methods to clarify the miscibility of the polymer blends. It could be concluded that in the cooled state, the blends form a heterogeneous structure with two separate phases. The tensile, flexural, impact toughness properties of the PC/EPC blend and PC/EPC/MWCNT nanocomposites were carried out to illuminate the optimum concentration of polymer blends and MWCNTs. The 335% increment for the impact strength results appeared with combination of 10% EPC in the PC matrix. The flexural modulus and strength of PC/EPC blend increased by 75.1% and 59.1%, respectively. The Nielsen model was performed to fit the best curve of theoretical simulation to experimental results for elastomeric dispersed in the plastic matrix. Halpin‐Tsai model was applied to estimate the stiffness of nanocomposites blends with different volume fraction and aspect ratio of MWCNTs in the PC/EPC blends. Finally, in the presence of MWCNTs, all nanocomposite samples were semi‐conducting and the percolation threshold of the PC/EPC (10%) blends was between 0.5% and 1.0% MWCNTs. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44661.