Experimental analysis of charge redistribution due to chemical bonding by high-resolution transmission electron microscopy

The electronic charge density distribution or the electrostatic atomic potential of a solid or molecule contains information not only on the atomic structure, but also on the electronic properties, such as the nature of the chemical bonds or the degree of ionization of atoms. However, the redistribution of charge due to chemical bonding is small compared with the total charge density, and therefore difficult to measure. Here, we demonstrate an experimental analysis of charge redistribution due to chemical bonding by means of high-resolution transmission electron microscopy (HRTEM). We analyse charge transfer on the single-atom level for nitrogen-substitution point defects in graphene, and confirm the ionicity of single-layer hexagonal boron nitride. Our combination of HRTEM experiments and first-principles electronic structure calculations opens a new way to investigate electronic configurations of point defects, other non-periodic arrangements or nanoscale objects that cannot be studied by an electron or X-ray diffraction analysis.     

Elimination of polycyclic aromatic hydrocarbons by bleaching of olive pomace oil

A detailed study of the efficacy of the bleaching process for elimination of polycyclic aromatic hydrocarbons in Spanish olive pomace oils has been carried out. For this purpose active carbon with bleaching earth was used as absorbent. The amount of benzo‐(α)‐pyrene was determined by reversed‐phase high‐performance liquid chromatography with a Fluorimetric detector. The use of exhausted filter‐cakes in countercurrent processes with a cake formed of active carbon and bleaching earth is very efficient for reducing the initial content of benzo‐(α)‐pyrene before the addition of fresh adsorbent, thus reducing the amounts of carbon and earth required.     

Integrated bacterial process for the treatment of a spent nickel catalyst

Integrated biological processes involving the dissolution and subsequent precipitation have been used for the treatment of the spent material from the hydrogenation of vegetable oil containing a high-level of nickel. Our results show that nickel was successfully leached using Acidithiobacillus thiooxidans. The percentages of nickel leached using A. thiooxidans were higher than those obtained with dilute sulphuric acid solutions. Due to the physical characteristics of the residue, the best results were obtained when the leaching process was carried out using sulphuric acid biogenerated by an A. thiooxidans biofilm. The recovery of nickel from the leachates was performed at room temperature by precipitating with sulphide generated by Desulfovibrio cells. Indirect precipitation using sulphide generated in Desulfovibrio sp. cultures allowed the recovery of nickel as the very insoluble nickel sulphide.     

Potentiation of anticancer drugs: effects of pentoxifylline on neoplastic cells

The drug efflux activity of P-glycoprotein (P-gp, a product of the mdr1 gene, ABCB1 member of ABC transporter family) represents a mechanism by which tumor cells escape death induced by chemotherapeutics. In this study, we investigated the mechanisms involved in the effects of pentoxifylline (PTX) on P-gp-mediated multidrug resistance (MDR) in mouse leukemia L1210/VCR cells. Parental sensitive mouse leukemia cells L1210, and multidrug-resistant cells, L1210/VCR, which are characterized by the overexpression of P-gp, were used as experimental models. The cells were exposed to 100 μmol/L PTX in the presence or absence of 1.2 μmol/L vincristine (VCR). Western blot analysis indicated a downregulation of P-gp protein expression when multidrug-resistant L1210/VCR cells were exposed to PTX. The effects of PTX on the sensitization of L1210/VCR cells to VCR correlate with the stimulation of apoptosis detected by Annexin V/propidium iodide apoptosis necrosis kit and proteolytic activation of both caspase-3 and caspase-9 monitored by Western blot analysis. Higher release of matrix metalloproteinases (MMPs), especially MMP-2, which could be attenuated by PTX, was found in L1210/VCR than in L1210 cells by gelatin zymography in electrophoretic gel. Exposure of resistant cells to PTX increased the content of phosphorylated Akt kinase. In contrast, the presence of VCR eliminated the effects of PTX on Akt kinase phosphorylation. Taken together, we conclude that PTX induces the sensitization of multidrug-resistant cells to VCR via downregulation of P-gp, stimulation of apoptosis and reduction of MMPs released from drug-resistant L1210/VCR cells. These facts bring new insights into the mechanisms of PTX action on cancer cells.     

Yeast diversity investigation of wine-related samples from two different Slovakian wine-producing areas through a multistep procedure

A multistep procedure was applied in order to investigate the yeasts diversity during the must fermentation of two wine varieties Frankovka Modra (Blaufränkisch) and Veltlinske Zelene (Grüner Veltliner) from two different Slovakian wine-producing areas. The procedure combined a cultivation step with a PCR-based selection step (f-ITS PCR; fluorescence internal transcribed spacer 2 polymerase chain reaction), and a final identification step oriented to the sequencing of ITS1-5.8S rDNA-ITS2 region of the selected yeasts. The strategy demonstrated to be suitable for the rapid analysis of a large panel of isolates. The f-ITS PCR was able to discriminate the isolated yeasts by one PCR run and capillary electrophoresis separation. The investigation showed the presence of non-Saccharomyces strains on grapes and during the initial and middle stages of must fermentation. Members of the genus Saccharomyces appeared only during the middle fermentation stage and they were the predominant species until the final phase of the process. The presented simple and reliable multistep procedure can be useful for the investigation of the yeast microflora from any wine-producing area and also for studying other kinds of food environments.     

Studies on the Effect of Reactive Polypropylene on the Properties of Filled Polyolefin Composites. Part 3. Effect of Maleic Anhydride Grafted Polypropylene on the Nature of Polyolefin Matrix

The effect of incorporation of maleic anhydride grafted polypropylene on the properties of composites based on separately filled polypropylene and ethylene–propylene copolymer was studied. The tensile strength and impact resistance of talc-filled polypropylene composite can be improved by optimizing the additive concentrations. On the other hand, the impact resistance of talc-filled ethylene–propylene copolymer composite hardly shows any positive effect due to the addition of maleic anhydride grafted polypropylene. The determination of melt flow index for both composite systems studied, however, indicates that addition of maleic anhydride grafted polypropylene lowers the melt viscosity of highly loaded composites.     

Reversed anisotropy of grain boundary properties and its effect on grain boundary engineering

Data on anisotropy of grain boundary properties are frequently published. In some cases, when they show the reverse course of structural dependence than is expected, they can seem confusing. Examples of this “reversed anisotropy” found for grain boundary segregation, diffusion and migration are presented. We demonstrate that the reversed anisotropy of grain boundary properties is caused by the compensation effect. This can have serious consequences for grain boundary engineering. It is also suggested that grain boundaries can be classified specifically and generally solely on the basis of well-defined thermodynamic parameters.     

Variation of a classical fingerprint of ideal memristor

Gradual disappearance of hysteresis with increasing frequency of the exciting signal is considered a classical fingerprint of general memristive systems. The paper analyzes a special version of this fingerprint, when the value of the charge delivered within the half‐period remains constant while the frequency of the sinusoidal current is increasing. Under these conditions, the area of the pinched hysteresis loop of the ideal memristor increases with the square of the frequency. Breaking the rules of this fingerprint indicates reliably that the element analyzed is not an ideal memristor. Copyright © 2015 The Authors International Journal of Circuit Theory and Applications Published by John Wiley & Sons, Ltd.     

Celiac Disease Defined by Over-Sensitivity to Gliadin Activation and Superior Antigen Presentation of Dendritic Cells

The autoimmune condition, Celiac Disease (CeD), displays broad clinical symptoms due to gluten exposure. Its genetic association with DQ variants in the human leukocyte antigen (HLA) system has been recognised. Monocyte-derived mature dendritic cells (MoDCs) present gluten peptides through HLA-DQ and co-stimulatory molecules to T lymphocytes, eliciting a cytokine-rich microenvironment. Having access to CeD associated families prevalent in the Czech Republic, this study utilised an in vitro model to investigate their differential monocyte profile. The higher monocyte yields isolated from PBMCs of CeD patients versus control individuals also reflected the greater proportion of dendritic cells derived from these sources following lipopolysaccharide (LPS)/ peptic-tryptic-gliadin (PTG) fragment stimulation. Cell surface markers of CeD monocytes and MoDCs were subsequently profiled. This foremost study identified a novel bio-profile characterised by elevated CD64 and reduced CD33 levels, unique to CD14++ monocytes of CeD patients. Normalisation to LPS stimulation revealed the increased sensitivity of CeD-MoDCs to PTG, as shown by CD86 and HLA-DQ flow cytometric readouts. Enhanced CD86 and HLA-DQ expression in CeD-MoDCs were revealed by confocal microscopy. Analysis highlighted their dominance at the CeD-MoDC membrane in comparison to controls, reflective of superior antigen presentation ability. In conclusion, this investigative study deciphered the monocytes and MoDCs of CeD patients with the identification of a novel bio-profile marker of potential diagnostic value for clinical interpretation. Herein, the characterisation of CD86 and HLA-DQ as activators to stimulants, along with robust membrane assembly reflective of efficient antigen presentation, offers CeD targeted therapeutic avenues worth further exploration.