Extending the functionality of the power law-based STDP synaptic model by implementing the support for delay value dominated by axonal propagation

Learning is conceptualized to be possible due to the reconfiguration of neural networks in the brain. This ability is referred to as neuroplasticity. One of the ways by which plasticity is observed can be explained by plasticity exhibited by the synaptic connections between two neurons. Spike-timing-dependent plasticity (STDP) is a biological process, which has been experimentally observed to produce the effect of synaptic plasticity. The STDP process is based on the precise arrival times of presynaptic and postsynaptic spikes at the synapse. This arrival time can be calculated using the timing of the spike offset by propagation delay to the synapse from the neuron. The STDP process is known to affect the connection strength between the neurons, affecting the amplitude of the spike generated in the postsynaptic neuron. In this thesis, we worked on the simulation model of synapses exhibiting STDP properties. We used the NEST simulator framework for the implementation. The current state-of-the-art model of the STDP synapse supports only delay values as purely dendritic. We implemented support for axonal propagation delay in the synaptic model, along with support for axonal delay value greater than dendritic delay. We verified the implementation with an independent program for testing. The implementation was then analyzed for its impact in a network with different values for the axonal delay. This was done by taking the histogram of the weights of the STDP synapse model in a many-to-one network configuration which was simulated for hundred biological seconds. The results of the analysis matched theoretical predictions with the weights shifting to a higher value as the axonal delay value was increased. The analysis was also computed after optimizing the alpha parameter of the model, to make sure the network average firing rate is at a biologically comparable level at 10 spikes/s or below. In this result, we can not see any significant shifts in weight as predicted by theory. We also benchmarked the newer algorithm to check if it has any additional computation cost, which showed our implementation did not affect the performance.M-D

Strain Hardening Behavior of Engineered Geopolymer Composites: Effects of the Activator Combination

Fly ash-based engineered geopolymer composites (EGCs) exhibiting strain hardening behavior under uni-axial tension were developed employing two different sodium-based (Na-based) and potassium-based (K-based) activator combinations. The relatively brittle low calcium (Class F) fly ash-based geopolymer matrix was reinforced with randomly oriented short poly vinyl alcohol (PVA) fibers (2% v/v). Na-based activator combination was composed of 8.0 M NaOH solution (28.6% w/w) and Na2SiO3 solution (71.4% w/w) with a SiO2/Na2O ratio of 2.0; whereas, Kbased activator combination was composed of 8.0 M KOH solution (28.6% w/w) and K2SiO3 solution (71.4% w/w) with a SiO2/K2O ratio of 2.23. The matrix and composite properties of the developed fly ash-based EGCs including workability of the fresh matrix, density, compressive strength and uni-axial tensile behavior were evaluated. The experimental results revealed that the sodium-based EGC (EGC-Na) exhibited superior tensile strain capacity, compressive and uni-axial tensile strengths with significantly enhanced ductility

Host preferences of some acridids (Insecta: Orthoptera) in relation to some biochemical parameters

Biochemical analysis of host plants of 6 species of acridids for their total protein, carbohydrates, phenols, free aminoacids, water and nitrogen content revealed significant correlation in regard to their host preferences, wherein the leaf water-nitrogen index as well as the total phenol composition appeared to play an important role

Transparent and conducting boron doped ZnO thin films grown by aerosol assisted chemical vapor deposition

Boron doped zinc oxide thin films via aerosol assisted chemical vapor deposition with resisitivities as low as 5.1 × 10−3 Ω cm

Compressive strength of tungsten mine waste- and metakaolinbased geopolymers

Neuro-fuzzy approach has been successfully applied to a wide range of civil engineering problems so far. However, this is limited for geopolymeric specimens. In the present study, compressive strength of different types of geopolymers has been modeled by adaptive neuro-fuzzy interfacial systems (ANFIS). The model was constructed by 395 experimental data collected from the literature and divided into 80% and 20% for training and testing phases, respectively. Curing time, Ca(OH)2 content, NaOH concentration, mold type, aluminosilicate source and H2O/Na2O molar ratio were independent input parameters in the proposed model. Absolute fraction of variance, absolute percentage error and root mean square error of 0.94, 11.52 and 14.48, respectively in training phase and 0.92, 15.89 and 23.69, respectively in testing phase of the model were achieved showing the relatively high accuracy of the proposed ANFIS model. By the obtained results, a comparative study was performed to show the interaction of some selected factors on the compressive strength of the considered geopolymers. The discussions findings were in accordance to the experimental studies and those results presented in the literature

Synthesis of superhydrophobic polymer/tungsten (VI) oxide nanocomposite thin films

A method is presented to enable the preparation of superhydrophobic polymer/tungsten (VI) oxide (WO3) nanocomposite coatings on glass substrates. WO3 nanoparticles were incorporated via the swell-encapsulation-shrink method into superhydrophobic silicone polymer films deposited on glass via aerosol-assisted chemical vapour deposition (AACVD) to produce the novel nanocomposite films. The technique overcomes the limitations of previous methods for nanoparticle incorporation to provide a synthetic route to previously unattainable materials. The nanocomposite films retain the properties of the superhydrophobic polymer while the presence of the nanoparticles is clearly evident. As such, the films have a range of potential applications including high surface area photocatalysis and self-cleaning photochromic or electrochromic coatings. The two-stage synthesis is shown to be flexible and suggests great scope for producing any number of future novel materials. The thin films were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) analysis, X-ray photoelectron spectroscopy (XPS), infra-red (FTIR) spectroscopy, X-ray diffractometry (XRD) and water droplet contact angle measurements

Rheological Characterization of Ultra-High Performance Concrete for 3d Printing

The authors recently developed a 3D-printable ultra-high performance fiber-reinforced concrete (3DP-UHPFRC) for additive construction of structural members with significantly reduced reliance on steel bars. This study investigates the rheological behavior of the developed 3DP-UHPFRC. The effects of two major factors affecting the performance of 3DP-UHPFRC, namely steel fiber volume (0, 1%, and 2%) and nano-clay (NC) content (0, 0.1%, and 0.2% by binder mass) on workability, static yield stress, dynamic yield stress, and apparent viscosity were determined. Test results showed that the inclusion of steel fibers and NC reduced the workability and led to a significant increase in the static yield stress, dynamic yield stress, and apparent viscosity. However, the effect of NC content on the rheological properties became negligible in the mixtures made with 2% fiber content. Similarly, the effect of steel fiber volume became negligible in the mixtures made with 0.2% NC. In addition, the influence of changes in rheology due to the addition of steel fiber and NC on the extrudability and buildability of the mixtures were investigated by 3D-printing of 500 mm high hollow columns with three different print speeds. The results showed all mixtures exhibited satisfactory extrudability (i.e., no blockage of extruder or tearing of filaments was observed). In addition, the buildability of the mixtures increased as the steel fiber and NC contents increased

Previsão da resistência de geopolímeros monofásicos

The discovery of one-part geopolymers is considered a key event on the evolution of geopolymer technology because emulates one of the most important properties of Portland cement, the just add water concept. This materials are not associated with the known problems of two part geopolymers, namely the use of caustic solutions that have poor workability and make the handling and application of geopolymers difficult and the fact that alkaline or soluble silicates are not consumed during geopolymerization leading to severe efflorescence phenomena. However, so far very few investigations were published on this field and some report low mechanical strength. This paper discloses results regarding the numerical modelling of one part-geopolymers compressive strength.A descoberta dos geopolímeros monofásicos é considerado um importante acontecimento no âmbito da tecnologia dos geopolímeros porque mimetizam uma das mais importantes propriedades do cimento Portland, o conceito relativo à simples adição de água. Estes materiais não estão associados aos conhecidos problemas dos geopolímeros correntes nomeadamente a utilização de soluções cáusticas, baixa trabalhabilidade que dificultam a sua colocação e o facto das espécies alcalinas e silicatos solúveis não reagirem na sua totalidade durante a reacção de geopolímerização originando o aparecimento de elevada quantidade de eflorescências. Contudo muito poucas investigações foram publicadas neste domínio e algumas apresentam baixa resistência mecânica. Este artigo apresenta resultados relativos à modelação numérica da resistência à compressão de geopolímeros monofásicos.info:eu-repo/semantics/publishedVersio

1,8-Bis(4-meth­oxy-3-nitro­phen­yl)naphthalene

Mol­ecules of the title compound, C24H18N2O6, are located on a twofold rotation axis passing through through the central C—C bond of the naphthalene ring system. The mol­ecular conformation is characterized by a roughly coplanar arrangement of the two substituted phenyl rings [dihedral angle 18.53 (5)°]. These two aryl rings are each twisted by 65.40 (5)° from the plane of the naphthyl unit