Milos Petrovic

Facilitation of Long-Term Potentiation by Muscarinic M1 Receptors is mediated by inhibition of SK channels

Summary Muscarinic receptor activation facilitates the induction of synaptic plasticity and enhances cognitive function. However, the specific muscarinic receptor subtype involved and the critical intracellular signaling pathways engaged have remained controversial. Here, we show that the recently discovered highly selective allosteric M1 receptor agonist 77-LH-28-1 facilitates long-term potentiation (LTP) induced by theta burst stimulation at Schaffer collateral synapses in the hippocampus. Similarly, release of acetylcholine by stimulation of cholinergic fibers facilitates LTP via activation of M1 receptors. N-methyl-D-aspartate receptor (NMDAR) opening during theta burst stimulation was enhanced by M1 receptor activation, indicating this is the mechanism for LTP facilitation. M1 receptors were found to enhance NMDAR activation by inhibiting SK channels that otherwise act to hyperpolarize postsynaptic spines and inhibit NMDAR opening. Thus, we describe a mechanism where M1 receptor activation inhibits SK channels, allowing enhanced NMDAR activity and leading to a facilitation of LTP induction in the hippocampus.

Intensity Fiber-Optic Sensor for Structural Health Monitoring Calibrated by Impact Tester

In this paper, the use of intrinsic intensity fiber-optic sensors for structural health monitoring was investigated. Polyethylene-based composite samples with glass mat reinforcement and embedded telecommunication fibers were subjected to impact using high-speed puncture impact tester as a calibration device. Transfer function of the sensor was generated by linking the light intensity modulation depth with the impact force and the impact point to fiber distance. Conditions for transfer function validity were presented. To detect any possible dangerous impact, a net of crossed fibers was proposed and the net spacing for the given material was calculated. Appropriate non-damaging calibration procedure was proposed, as well as the algorithm for locating the impact point. The method for calculating the impact force, the projectile momentum change, and the place of impact was verified by consecutive strikes on the previously calibrated sample. The sensor can also provide information on the time of the impact and an alarm signal if the force exceeds the damaging threshold force..

Bending behaviour of glulam beams reinforced with carbon FRP plates

The idea of reinforcing glued laminated timber (glulam) beams came in response to the need to improve the mechanical properties, as well as to ensure higher reliability of this type of structural elements. This paper describes an experimental program which examines the reinforcement in flexure of glulam beams with carbon fibre reinforced plastic (CFRP) plates. Fifteen beams reinforced with CFRP at the tension side and five unreinforced control beams were instrumented and tested to failure in a four-point bending configuration. The mechanical properties of reinforced beams are compared to those of unreinforced beams with regard to the load-deflection behaviour, failure mode, ultimate load capacity, stiffness and strain distribution. The experimental results demonstrated the beneficial effect of the proposed reinforcing solution in terms of strength, stiffness and ductility.

Healing efficiency of polystyrene electrospun nanofibers with Grubbs’ catalyst in thermosetting composite

The study presents a novel method for the protection of Grubbs’ catalyst, by incorporation in polystyrene fibres via electrospinning technique. Epoxy-glass fibre composite with embedded self-healing agents (polystyrene fibres with Grubbs’ and microcapsules with dicyclopentadiene) was processed. Fibres retained pale purple colour during processing, revealing that fibres provided good protection of the catalyst from the amine hardener. The influence of self-healing agents’ content and thermal treatment on self-healing efficiency was investigated. Fourier transform infrared spectroscopy revealed that a polydicyclopentadiene formed at the healed interface. Thermal analysis revealed that ‘bleed’ at the healing sites from different samples had similar concentration of polydicyclopentadiene, indicating that the same amount of the catalyst has been provided to dicyclopentadiene for polymerization. This finding lead to assumption that electrospun polymer fibres enabled good dispersion of the catalyst in the composites. The low energy impact tests of the samples showed a recovery of 90% after 24 h at room temperature and up to 111% after repeated heating cycles.

Electrospun Poly(styrene) Fibers as a Protection for the First- and the Second-Generation Grubbs’ Catalyst

ABSTRACT The study presents a novel method for protection of the first- and the second-generation Grubbs’ catalyst, by incorporation in poly(styrene) fibers through electrospinning technique. Both catalysts are sensitive to the presence of the amine hardeners in the epoxy-based self-healing composites and require protection from deactivation to retain their ability to promote polymerization reaction of the healing agent. Comparison of healing efficiencies of both catalysts suggested that poly(styrene) fibers offer better protection and dispersion for the first-generation Grubbs’ catalyst, although all the samples exhibited high-healing efficiency. Difference in stereoselectivity between two catalysts was also indicated. GRAPHICAL ABSTRACT

The impact of wood fiber surface modification on physical properties of wood-polymer composites

In this paper, the impact of wood fiber surface modification on mechanical properties of poly-(methyl methacrylate)(PMMA)-wood composite was examined. FTIR analysis has shown that the wood fiber surface modification was accomplished and that the matrix-fiber bond was established. The SEM image of the breakage surface has affirmed the improved adhesion between the fibers and the polymer in the specimen with modified wood fibers. The bond improvement between the wood fibers and the matrix results in increased hardness and a better distribution of strain within the composite. High speed impact testing results have shown that the specimen with the bonding agent can increase the absorbed energy six times when compared to the pure PMMA specimen.