Sharif Digital Repository

Neuronal synchronization plays an important role in the various functionality of nervous system such as binding, cognition, information processing, and computation. In this paper, we investigated how random and intentional failures in the nodes of a network influence its phase synchronization properties. We considered both artificially constructed networks using models such as preferential attachment, Watts-Strogatz, and Erdo{combining double acute accent} s-Rényi as well as a number of real neuronal networks. The failure strategy was either random or intentional based on properties of the nodes such as degree, clustering coefficient, betweenness centrality, and vulnerability. Hindmarsh-Rose... 

Recyclable CuO nanoparticles provide an efficient, economic, and novel method for the synthesis of quinoxaline, benzoxazine, and benzothiazine. This method provides a wide range of substrate applicability, avoids the use of organic solvents, and gives benzoheterocycles in satisfactory yields  

A simple, green and high-yielding procedure for the synthesis of 4-substituted-2-(alkylsulfanyl)thiazoles from the reaction of dithiocarbamates and α-halocarbonyl containing compounds in water is described. Also, a one-pot, two-step procedure for the synthesis of 2-(alkylsulfanyl)thiazoles from acetophenone and dithiocarbamates was developed. © 2016 Elsevier Ltd. All rights reserved  

A heterogeneous recoverable catalyst was prepared via the complexation of palladium onto the surface of magnetic nanoparticles coated by a poly(1-vinyl imidazole) brush. The stable, active and reusable catalyst was proven to be highly active in aerobic oxidation of primary and secondary alcohols with excellent yields. Only 0.1 mol% of the catalyst was used to oxidize 1 mmol of primary and secondary alcohols. The catalyst was readily recovered and reused up to 10 times under the described reaction conditions without significant loss of activity  

This paper investigates the behaviour of C-shaped and L-shaped angle shear connectors embedded in solid concrete slabs. An effective finite element model is proposed to simulate the push out tests of these shear connectors that encompass nonlinear material behaviour, large displacement and damage plasticity. The finite element models are validated against test results. Parametric studies using this nonlinear model are performed to investigate the variations in concrete strength and connector dimensions. The finite element analyses also confirm the test results that increasing the length of shear connector increases their shear strength proportionately. It is observed that the maximum stress... 

ECG denoising has always been an important issue in medical engineering. The purposes of denoising are reducing noise level and improving signal to noise ratio (SNR) without distorting the signal. This paper proposes a method for removing white Gaussian noise from ECG signals. The concepts of singularity and local maxima of the wavelet transform modulus were used for analyzing singularity and reconstructing the ECG signal. Adaptive thresholding was used to remove white Gaussian noise modulus maximum of wavelet transform and then reconstruct the signal  

This study proposes a new technique for registration of complicated freeform surfaces. The relationship between the initial and transferred location/orientation of a points cloud is formulated and then generalized within the framework of the influence surface modeling approach using least squares method. Results of case studies for estimation of the transformation matrix of articular surface of the knee joint in two scenes of MR images indicated high accuracies of ±1 mm and ±1 degree  

Fractals are remarkable examples of self-similarity where a structure or dynamic pattern is repeated over multiple spatial or time scales. However, little is known about how fractal stimuli such as fractal surfaces interact with their local environment if it exhibits order. Here we show geometry-induced formation of fractal defect states in Koch nematic colloids, exhibiting fractal self-similarity better than 90% over three orders of magnitude in the length scales, from micrometers to nanometres. We produce polymer Koch-shaped hollow colloidal prisms of three successive fractal iterations by direct laser writing, and characterize their coupling with the nematic by polarization microscopy and... 

The dielectric constant e of interfacial water has been predicted to be smaller than that of bulk water (e ≈ 80) because the rotational freedom of water dipoles is expected to decrease near surfaces, yet experimental evidence is lacking. We report local capacitance measurements for water confined between two atomically flat walls separated by various distances down to 1 nanometer. Our experiments reveal the presence of an interfacial layer with vanishingly small polarization such that its out-of-plane e is only ~2. The electrically dead layer is found to be two to three molecules thick. These results provide much-needed feedback for theories describing water-mediated surface interactions and... 

In this work, graphene oxide (GO) aqueous suspensions prepared by a chemical exfoliation method showed a fluorescence peak at ∼615 nm. Photoluminescence spectroscopy determined that functionalization of the GO sheets by 3-(2-Aminoethylamino) propyltrimethoxysilane molecules significantly quench the fluorescence property of the GO sheets. Fourier transform infrared spectroscopy confirmed proper functionalization of the GO sheets. Curcumin was applied as a fluorescent natural material with an emission peak at ∼550 nm wavelength for green fluorescent labeling of the functionalized-GO sheets. The curcumin-labeled functionalized-GO sheets showed an intense emission band fluorescent property with... 

An efficient method for the synthesis of functionalized 4H-chromenes via a one-pot three-component condensation reaction of a 2-hydroxybenzaldehyde with an active methylene compound and a carbon-based nucleophile in the presence of a catalytic amount of ZrOCl2·8H2O in water under thermal condition has been described. High yields, simple work-up procedure, performing reactions in water and synthesis of complex molecules with a one-pot procedure are the main advantages of this procedure. In addition, the structure of the product from the condensation of salicylaldehyde, 2-naphthol, and dimedone was confirmed by X-ray crystallography. © 2018 Wiley Periodicals, Inc  

The ability to predict the cellular dynamics of intracellular transport has enormous potential to impact human health. A key transporter is kinesin-1, an ATP-driven molecular motor that shuttles cellular cargos along microtubules (MTs). The dynamics of kinesins depends critically on their unbinding rate from MT, which varies depending on the force direction applied on the motor, i.e. the force-unbinding rate relation is asymmetric. However, it remains unclear how changing the force direction from resisting (applied against the motion direction) to assisting (applied in the motion direction) alters the kinesin's unbinding and stepping. Here, we propose a theoretical model for the influence of... 

An operationally simple, practical, and economical protocol for iron(III) chloride catalyzed Paal-Knorr pyrrole synthesis in water in good to excellent yields has been developed. Several N-substituted pyrroles are readily prepared from the reaction of 2,5-dimethoxytetrahydrofuran and aryl/alkyl, sulfonyl and acyl amines under very mild reaction conditions. © Georg Thieme Verlag Stuttgart  

A simple and green route to synthesis of (4 or 5)-aryl-2-aryloyl-(1H)-imidazoles is described. Two isomers can tautomerize to each other by the heat absorption. The tauto-isomerization process was studied by NMR technique. Acidity and stability of products were studied using B3LYP method. © 2009 Elsevier Ltd. All rights reserved  

An Iron(lV)-oxo heme(+·) complex (Compound I, Cpd I) is the proposed active species of heme enzymes such as the cytochromes P450 and Is elusive; therefore, biomimetic studies on active site mimics give valuable Insight Into the fundamental properties of heme active species. In this work we present density functional theory (DFT) calculations on substrate hydroxylatlon by a Compound I mimic [FeIV=O(Por+̇)Cl] and its one-electron reduced form [FeIV=O(Por)Cl]-. Thus, recent experimental studies showed that [FeIV =O(Por)Cl]- is able to react with substrates via hydride transfer reactions [Jeong, Y. J.; Kang, Y.; Han, A.-R.; Lee, Y.-M.; Kotani, H.; Fukuzumi, S.; Nam, W. Angew. Chem., Int. Ed.... 

Segmentation of the Left ventricle (LV) is a crucial step for quantitative measurements such as area, volume, and ejection fraction. However, the automatic LV segmentation in 2D echocardiographic images is a challenging task due to ill-defined borders, and operator dependence issues (insufficient reproducibility). U-net, which is a well-known architecture in medical image segmentation, addressed this problem through an encoder-decoder path. Despite outstanding overall performance, U-net ignores the contribution of all semantic strengths in the segmentation procedure. In the present study, we have proposed a novel architecture to tackle this drawback. Feature maps in all levels of the decoder... 

The molecular mechanisms of self-organization that orchestrate embryonic cells to create astonishing patterns have been among major questions of developmental biology. It is recently shown that embryonic stem cells (ESCs), when cultured in particular micropatterns, can self-organize and mimic the early steps of pre-implantation embryogenesis. A systems-biology model to address this observation from a dynamical systems perspective is essential and can enhance understanding of the phenomenon. Results: Here, we propose a multicellular mathematical model for pattern formation during in vitro gastrulation of human ESCs. This model enhances the basic principles of Waddington epigenetic landscape... 

We consider a population of individuals living in an uncertain environment. Individuals are able to make noisy observations of the environment and communicate using signals. We show that the model shows an order-disorder transition from an ordered phase in low communication noise in which a consensus about the environmental state is formed to a disordered phase in high communication noise in which no consensus is formed. There are different consensus states: informed consensus in which consensus on the correct belief about the environmental state is formed, and misinformed consensus in which consensus on a wrong belief is formed. Based on the consensus state reached, the ordered phase is... 

Having to survive in a continuously changing environment has driven the human brain to actively predict the future state of its surroundings. Oddball tasks are specific types of experiments in which this nature of the human brain is studied. Detailed mathematical models have been constructed to explain the brain's perception in these tasks. These models consider a subject as an ideal observer who abstracts a hypothesis from the previous stimuli, and estimates its hyper-parameters - in order to make the next prediction. The corresponding prediction error is assumed to manifest the subjective surprise of the brain. While the approach of earlier works to this problem has been to suggest an... 

We study the interdiction of illegal product distribution in a network with multiple sources (origins) and sinks (destinations). This work contributes to the literature of dynamic maximum flow interdiction problems by addressing multiple commodities in a network of relationships. The related distribution network consists of (1) criminals, who are hierarchically connected, and seeking to maximize the total profit flow from origins to destinations, and (2) enforcement officers aiming to minimize criminals’ long-term success by monitoring and arresting them, using the limited resources at their disposal. Considering several real-world operational details, we first propose a mixed-integer...