Coumarin-Tagged Dinuclear Trithiolato-Bridged Ruthenium(II)⋅Arene Complexes: Photophysical Properties and Antiparasitic Activity

The synthesis, characterization, photophysical and biological properties of 13 new conjugate coumarin-diruthenium(II)⋅arene complexes against Toxoplasma gondii are presented. For all conjugate organometallic unit/coumarins, an almost complete loss of fluorescence efficacy was observed. However, the nature of the fluorophore, the type of bonding, the presence and length of a linker between the coumarin dye and the ruthenium(II) moiety, and the number of dye units influenced their biological properties. The in vitro activity against a transgenic T. gondii strain grown in human foreskin fibroblasts (HFF) leads to IC₅₀ values for T. gondii β-gal from 105 to 735 nM. Of note is that nine compounds displayed lower IC₅₀ than the standard drug pyrimethamine. One compound applied at its IC₅₀ did not affect B-cell proliferation but had an impact on T-cell proliferation in murine splenocyte cultures. Transmission electron microscopy of T. gondii β-gal-infected HFF showed that treatment predominantly affected the parasites’ mitochondrion.     

Synthesis and characterization of polyvinyl alcohol/cellulose cryogels and their testing as carriers for a bioactive component

Novel physically cross-linked cryogels containing polyvinyl alcohol (PVA) and various amounts of microcrystalline cellulose were obtained by freezing/thawing technique. The main goal of this study was to improve the properties and the performances of the pure PVA cryogels. The morphological aspects of the cryogels were studied by scanning electron microscopy (SEM). The Fourier transform infrared spectroscopy (FT-IR) was used to reveal the presence of the interactions between the two polymers. Changes in crystallinity of the samples were confirmed by X-ray diffraction (XRD) and by FT-IR spectroscopy. The modification of the thermal behavior induced by cellulose was studied by thermogravimetry. Rheological analysis revealed higher values of storage modulus (G′) for the cryogels containing higher amounts of cellulose. The degree and rate of swelling were controlled by the presence of the natural polymer in the network. The potential application as bioactive compound carriers was tested, using vanillin as an active agent.     

Screening and identification of organophosphorus compounds related to the chemical weapons convention with 1D and 2D NMR spectroscopy

Two-dimensional 1H-31P Fast-HMQC was tested for determination of the presence in low concentrations of organophosphorus compounds related to the Chemical Weapons Convention. This method, based on inverse detection, demonstrated high sensitivity and selectivity. Background signals, such as solvent peaks, are suppressed with good efficiency, and organophosphorus compounds present at a concentration level 1-10 microg/mL can be detected within a few hours. In addition, phosphorus-selective one-dimensional 1H-31P HSQC-TOCSY was applied to produce a complete proton spectrum of selected organophosphorus compound from a sample containing intense background resonances. Application of the methods presented in this paper resulted in considerably improved performance of NMR spectroscopy as a complementary technique for screening as well as identification of chemical warfare agents in environmental samples.     

DC performance, AC loss and transient field stability of five medium size NbTi cable-in-conduit conductors with parametric variations

Five medium size NbTi cable-in-conduit conductors with parametric variations in the cable layout were fabricated of three different strands to investigate their DC performance, AC loss behaviour and transient stability by means of the SULTAN facility. A comparison of measured strand data and the cable performances at the same background field indicates that the current carrying capacity of the conductors is limited by the total magnetic field on the high field side. Due to the self-field contribution the total magnetic field on the high field side is considerably larger than the background field at high currents. The take-off electric fields were found to decrease with increasing quench currents, resulting in sudden take-offs for large overall current densities. Effective self-field factors are used to describe the DC performance in the current range, where the critical current and the current sharing temperature are accessible. The quench behaviour of the conductors is discussed in the framework of a model based on peak-field-induced quenches. Differences in the DC performance of the conductors are related to the variation in the transverse resistance determining the ability of the conductors to redistribute the current in the case of a current imbalance originated at the joints. This aspect was studied in more detail by modifying one of the joints allowing a defined number of subcables to be disconnected. The voltage-current characteristics of strands and cable-in-conduit conductors are compared. The reasons for cable n values deviating from the strand n values are discussed. Moreover, the effect of different transverse resistances on the AC loss behaviour and the transient field stability was investigated. Ni coating of the strands was found to be sufficient to eliminate the interstrand coupling current loss. Thus, additional subcable wraps provided no significant further loss reduction.     

A 1-D non-isothermal dynamic model for the thermal decomposition of a gibbsite particle

A 1-D mathematical model describing the thermal decomposition, or calcination, of a single gibbsite particle to alumina has been developed and validated against literature data. A dynamic, spatially distributed, mass and energy balance model enables the prediction of the evolution of chemical composition and temperature as a function of radial position inside a particle. In the thermal decomposition of gibbsite, water vapour is formed and the internal water vapour pressure plays a significant role in determining the rate of gibbsite dehydration. A thermal decomposition rate equation, developed by closely matching experimental data reported previously in the literature, assumes a reaction order of 1 with respect to gibbsite concentration, and an order of −1 with respect to water vapour pressure. Estimated values of the transformation kinetic parameters were k₀ = 2.5 × 10¹³ mol/(m³ s) for the pre-exponential factor, and E_a = 131 kJ/mol for the activation energy. Using these kinetic parameters, the gibbsite particle model is solved numerically to predict the evolution of the internal water vapour pressure, temperature and gibbsite concentration. The model prediction was shown to be very sensitive to the values of heat transfer coefficient, effective diffusivity, particle size and external pressure, but relatively less sensitive to the mass transfer coefficient and particle thermal conductivity. The predicted profile of the water vapour pressure inside the particle helps explain some phenomena observed in practice, including particle breakage and formation of a boehmite phase.     

Cellular and Molecular Targets of Nucleotide-Tagged Trithiolato-Bridged Arene Ruthenium Complexes in the Protozoan Parasites Toxoplasma gondii and Trypanosoma brucei

Toxoplasma gondii is an apicomplexan parasite that infects and proliferates within many different types of host cells and infects virtually all warm-blooded animals and humans. Trypanosoma brucei is an extracellular kinetoplastid that causes human African trypanosomiasis and Nagana disease in cattle, primarily in rural sub-Saharan Africa. Current treatments against both parasites have limitations, e.g., suboptimal efficacy and adverse side effects. Here, we investigate the potential cellular and molecular targets of a trithiolato-bridged arene ruthenium complex conjugated to 9-(2-hydroxyethyl)-adenine (1), which inhibits both parasites with IC₅₀s below 10⁻⁷ M. Proteins that bind to 1 were identified using differential affinity chromatography (DAC) followed by shotgun-mass spectrometry. A trithiolato-bridged ruthenium complex decorated with hypoxanthine (2) and 2-hydroxyethyl-adenine (3) were included as controls. Transmission electron microscopy (TEM) revealed distinct ultrastructural modifications in the mitochondrion induced by (1) but not by (2) and (3) in both species. DAC revealed 128 proteins in T. gondii and 46 proteins in T. brucei specifically binding to 1 but not 2 or 3. In T. gondii, the most abundant was a protein with unknown function annotated as YOU2. This protein is a homolog to the human mitochondrial inner membrane translocase subunit Tim10. In T. brucei, the most abundant proteins binding specifically to 1 were mitochondrial ATP-synthase subunits. Exposure of T. brucei bloodstream forms to 1 resulted in rapid breakdown of the ATP-synthase complex. Moreover, both datasets contained proteins involved in key steps of metabolism and nucleic acid binding proteins.     

Modelling and simulation of concrete leaching under outdoor exposure conditions

Recently, a demand regarding the assessment of release of dangerous substances from construction products was raised by European Commission which has issued the Mandate M/366 addressed to CEN. This action is in relation with the Essential Requirement No. 3 “Hygiene, Health and Environment” of the Construction Products Directive (89/106/EC). The potential hazard for environment and health may arise in different life cycle stages of a construction product. During the service life stage, the release of substances due to contact with the rain water is the main potential hazard source, as a consequence of the leaching phenomenon. The objective of this paper is to present the development of a coupled chemical-transport model for the case of a concrete based construction product, i.e. concrete paving slabs, exposed to rain water under outdoor exposure conditions. The development of the model is based on an iterative process of comparing the experimental results with the simulated results up to an acceptable fit. The experiments were conducted at laboratory scale (equilibrium and dynamic leaching tests) and field scale. The product was exposed for one year in two types of leaching scenarios under outdoor conditions, “runoff” and “stagnation”, and the element release was monitored. The model was calibrated using the experimental data obtained at laboratory scale and validated against measured field data, by taking into account the specific rain water balance and the atmospheric CO₂ uptake as input parameters. The numerical tool used in order to model and simulate the leaching behaviour was PHREEQC, coupled with the Lawrence Livermore National Laboratory (LLNL) thermodynamic data base. The simulation results are satisfying and the paper demonstrates the feasibility of the modelling approach for the leaching behaviour assessment of concrete type construction materials.     

New cellulose-lignin hydrogels and their application in controlled release of polyphenols

Novel superabsorbant cellulose-lignin hydrogels (CL) were prepared by a new two-step procedure consisting in dissolving cellulose in an alkaline solution with further mixing with lignin, followed by the chemical crosslinking with epichlorohydrin. The crosslinking occurrence was verified by Fourier Transform Infrared spectroscopy (FT-IR). The effect of the structure features of cellulose-lignin hydrogels on their dehydration heat was evaluated by Differential Scanning Calorimetry (DSC). The Scanning Electron Microscopy (SEM) images reveal some morphological aspects of the hydrogels. The degree as well as the rate of swelling in a mixture of water:ethanol = 19:1 were estimated. The possible application of these hydrogels as controlled release systems was tested. Polyphenols known as having a wide range of biological effects were selected to be incorporated in such hydrogels by an optimal procedure. The extract of grapes seeds from the Chambourcin type was used as a source of polyphenols (PF). The amount of the incorporated polyphenols was estimated by UV-VIS measurements. Characterization of the hydrogels containing polyphenols was performed by FTIR spectroscopy. Some parameters were estimated based on the registered spectra, as H-bond energy (E_H), the asymmetric index (a/b) and the enthalpy of H-bond formation (ΔH). The modifications of the thermal behavior and morphology induced by the presence of the polyphenols in hydrogels were highlighted by DSC and SEM, respectively. The release of polyphenols from CL hydrogels depended on the lignin content from matrices, as assessed by spectral studies. Both loading with polyphenols and their release can be controlled by the composition of the hydrogels. The kinetic of polyphenols release was studied.     

Microstructure and dielectric properties of Ag-BaTiO3 composite ceramics

Di-phase composite ceramics based on BaTiO₃ with 5?vol% of Ag filler have been prepared by sintering the mixture of powders at temperatures above the silver melting point (1000?°C–1300?°C/2?h). As predicted by finite element calculations, the addition of metallic particles should produce a field concentration in some regions of the BaTiO₃ matrix and therefore, an enhanced dielectric response with respect to pure BaTiO₃. The role of oxygen vacancies on the dielectric relaxation mechanisms of Ag-BaTiO₃ composites has been investigated. The sintering temperature of 1200?°C provided optimized ceramics with excellent dielectric properties, i.e. with low losses (tanδ?<?3%) and room temperature permittivity measured at 50?kHz exceeding 6500 (and above 13,000 at the Curie temperature), as result of a good densification (94% relative density) and a synergy effect of the metallic particles inclusions and ceramic grain size in the range of ≈1?μm, where BaTiO₃ has a well-known maximum of its permittivity.