Anatomy and Growth Characteristics of Conjugated Polyelectrolyte/DNA Aggregates

Conjugated polyelectrolytes (CPEs) have been widely used as light harvesting macromolecules to amplify the signals of fluorescent assays that betray the presence of various biomolecular targets. Electrostatic interactions play an important role in coordinating optical coupling events and lead to the formation of complexes between oppositely charged CPEs and the target species. Here, we combine for the first time optical studies and structural characterization by liquid phase atomic force microscopy (AFM) to provide a picture of aggregate structure and growth dynamics between cationic CPE and DNA as a function of charge ratio. Specifically, poly1 ₂₀ , a copolymer containing a backbone with 50% fluorene, 30% phenylene, and 20% 2,1,3‐benzothiadiazole (BT) units and pendant cationic groups was mixed with single stranded DNA (ssDNA) labeled with the Cy5 acceptor chromophore. Continuous addition of ssDNA‐Cy5 to poly1 ₂₀ leads to a saturation in Cy5 emission due to Cy5–Cy5 self‐quenching. Addition of ssDNA to a preformed poly1 ₂₀ /ssDNA‐Cy5 solution results in increased sensitization by energy transfer and a reduction of Cy5–Cy5 self quenching. Adsorption of aggregates onto negatively charged mica under water allows for direct imaging of the polyelectrolyte complexes as a function of charge ratio. The composite set of observations allows for the development of a model for aggregate growth, which is dynamic and ceases when the surface charge becomes sufficiently negative. This saturation point can be mitigated by addition of unlabeled ssDNA.     

Cytotoxicity Study of UV-Laser-Irradiated PLLA Surfaces Subjected to Bio-Ceramisation: A New Way towards Implant Surface Modification

In this research we subjected samples of poly(L-lactide) (PLLA) extruded film to ultraviolet (193 nm ArF excimer laser) radiation below the ablation threshold. The modified film was immersed in Simulated Body Fluid (SBF) at 37 °C for 1 day or 7 days to obtain a layer of apatite ceramic (CaP) coating on the modified PLLA surface. The samples were characterized by means of optical profilometry, which indicated an increase in average roughness (Ra) from 25 nm for the unmodified PLLA to over 580 nm for irradiated PLLA incubated in SBF for 1 day. At the same time, the water contact angle decreased from 78° for neat PLLA to 35° for irradiated PLLA incubated in SBF, which suggests its higher hydrophilicity. The obtained materials were investigated by means of cell response fibroblasts (3T3) and macrophage-like cells (RAW 264.7). Properties of the obtained composites were compared to the unmodified PLLA film as well as to the UV-laser irradiated PLLA. The activation of the PLLA surface by laser irradiation led to a distinct increase in cytotoxicity, while the treatment with SBF and the deposition of apatite ceramic had only a limited preventive effect on this harmful impact and depended on the cell type. Fibroblasts were found to have good tolerance for the irradiated and ceramic-covered PLLA, but macrophages seem to interact with the substrate leading to the release of cytotoxic products.     

Morphology and compression‐after‐impact strength relationship in interleaved toughened composites

Morphology and compression after impact (CAI) strength relationships in interleaved toughened high performance composites are investigated using a quantitative two‐dimensional image analysis approach. A group of six quasi‐isotropic carbon fiber‐epoxy composites with identical compositions, but having variations in CAI strengths, were analyzed to study how the interleaf particle size, particle size distribution, and location of particles in the interlaminar region affect the CAI strength values and the corresponding damage mechanisms. It is found that the CAI strength of interleaved‐toughened composites is significantly affected by the size and size distribution of toughener particles in the interlaminar regions of the composite. In general, high CAI strength composites exhibit more uniform particle size distribution throughout the interlaminar regions. Whereas, for low CAI strength composites, the interleaf particles tend to cluster together and have varied size distribution.     

Synthesis and Biological Studies of Novel Aminophosphonates and Their Metal Carbonyl Complexes (Fe,Ru)

The quest to find new inhibitors of biologically relevant targets is considered an important strategy to introduce new drug candidates for the treatment of neurodegenerative diseases. A series of (aminomethyl)benzylphosphonates 8a–c and their metallocarbonyl iron 9a–c and ruthenium 10a–c complexes were designed, synthesized, and evaluated for their inhibitory potentials against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) by determination of IC₅₀. Metallocarbonyl derivatives, in general, did not show significant inhibition activity against these enzymes, the most potent inhibitor was the (aminomethyl)benzylphosphonate 8a (IC₅₀ = 1.215 µM against AChE). Molecular docking analysis of AChE and (aminomethyl)benzylphosphonates 8a–c showed the strongest interactions of 8a and AChE compared to isomers 8b and 8c. Cytotoxicity studies of synthesized compounds towards the V79 cell line were also performed and discussed.     

Supporting ionic conductivity of Li2CO3/K2CO3 molten carbonate electrolyte by using yttria stabilized zirconia matrix

It is proposed that dual conductive electrolytes have the potential to improve properties of MCFC by using oxygen ion conductors as matrix material, creating what is termed composite electrolyte. In this work we present the results of testing a novel type of electrolyte of molten carbonate fuel cell which consists of Yttria Stabilized Zirconia impregnated by Lithium/Potassium carbonates. Polarization curves were obtained for temperatures between 500 °C and 800 °C. Without very accurate measurements it is not easy to determine the additional electric charge provided by oxygen ions (O⁼). We made an attempt to build a mathematical model which takes into account both conductivities and, based on the model, estimated the ratio of electric charge provided by oxygen ions and carbonate ions.     

Searching for the fundamentals of rehydroxylation dating of archaeological ceramics via NMR and IR microscopy

Determining absolute ages of archaeological ceramics is crucial for understanding past societies and reconstructing their accurate chronologies. The amount of OH hydroxyl chemically combined with ceramic material has been claimed to provide an ‘internal clock’ that can be read via RHX dating to determine the elapsed time since it was fired. The hydroxylation reaction, controlled by the slow diffusion of water molecules within the structure of clay minerals, has been described by a quartic root (time)^1/4 power law dependence. However, previous attempts of RHX dating by gravimetric methods have not been successful, since the mass gain due to OH hydroxylation or H₂O hydration could not be distinguished. We carried out a preliminary study of RHX dating via Infrared (IR) and Nuclear Magnetic Resonance (NMR) spectroscopy of three pure clay minerals, beidellite, illite and muscovite, as analogues for components of archaeological materials. Our study of RHX kinetics via IR microscopy gives important evidence regarding the quartic root time power law dependence. Furthermore, NMR allows us to study the structural as well as dynamic features of clays. Through observing the H/D exchange, we obtain access to the relevant activation energies and diffusion coefficients. We show that IR and NMR methods hold significant potential to refine the RHX dating method by understanding the elementary processes of mass transfer and hydroxylation in pure clays.     

Sound Absorbing Composites from Nonwoven and Cellulose Submicrofibres

This paper describes possibility of utilization of waste natural fibres in production of sound absorbing composites. Waste flax fibres were modified by enzymatic treatment, after which they became more short and fine. This form of fibres can create good sound absorption. Preliminary studies concerned an application of cellulose fibres after enzymatic treatment as the filling of thermoplastic sound absorbing composites. The conditions of composite manufacturing process from multilayer structure （matrix nonwoven/submicrofibres layer） were developed. The influence of submicroflbres content in the composite on the scale of the improvement of its sound absorption property was investigated. Results showed that for the same conditions of the composite manufacturing process and similar composite thickness, gradual increase in content of that filling leads to adequately increase in sound absorption coefficient of the composites. The composites could be applied among others to accommodations and transport facilities.     

Application of the Basalt Powder as a Filler for Polypropylene Composites With Improved Thermo‐Mechanical Stability and Reduced Flammability

The influence of the basalt powder (BP) on mechanical properties as well as on thermal stability and flammability of the isotactic polypropylene (iPP) composites was investigated. Thermo‐mechanical stability of the pure polypropylene and composite materials containing from 5 up to 40 wt% BP was defined in static and dynamic testing conditions with the use of the heat distortion temperature measurement, vicat softening point temperature test, and dynamic mechanical thermal analysis. All measurements showed, unequivocally, a significant improvement of thermo‐mechanical stability of the composite materials which was directly related to an increasing amount of inorganic filler. A research conducted on the mechanical properties revealed that stiffness and hardness of polypropylene‐based composites was affected by the addition of the filler, leading to a strong increase of both mechanical parameters. Moreover, the application of thermogravimetric analysis and cone calorimetry measurements allowed to determine the composites with highest thermal stability, which was dependent on the concentration of the filler. Changes observed in the polypropylene‐based composites properties were related to an increase of thermal diffusivity caused by presence of the BP measured by modified Angstrom method. POLYM. ENG. SCI., 59:E71–E79, 2019. © 2018 Society of Plastics Engineers