Amirkabir University of Technology

About: Amirkabir University of Technology is a education organization based out in Tehran, Iran. It is known for research contribution in the topics: Nonlinear system & Finite element method. The organization has 15254 authors who have published 31165 publications receiving 487551 citations. The organization is also known as: Tehran Polytechnic & Tehran Polytechnic University.

Biochemical and molecular characterization of hepatocyte-like cells derived from human bone marrow mesenchymal stem cells on a novel three-dimensional biocompatible nanofibrous scaffold.

Abstract: Background: There is significant interest in using nanofibers in tissue engineering from stem cells. The transdifferentiation of mesenchymal stem cells into the hepatic lineage in a nanofibrous structure has not been reported. In this study, a three dimensional nanofibrous scaffold is introduced for differentiation of human bone marrow derived mesenchymal stem cells (hBMSCs) into hepatocytes. Methods: A scaffold composed of Poly (e-caprolactone), collagen and polyethersulfone was fabricated by the electrospinning technique. After characterization of isolated hBMSCs, the performance of the cells on the scaffold was evaluated by Scanning Electron Microscopy (SEM) and MTT assay. Cytological, molecular and biochemical markers were measured to confirm differentiation potential of hBMSCs into hepatocytes. Results: The isolated cells possessed the basic properties of mesenchymal stem cells (MSCs). Based on scanning electron microscope (SEM) analysis and MTT assay, it was shown that the cells adhere, penetrate and proliferate on the nanofibers. Cultured cells on the nanofibers differentiated into hepatocyte-like cells and expressed hepatocyte specific markers such as albumin, α-fetoprotein, cytokeratin-18, cytokeratin-19 and cytochrome P450 3A4 at mRNA levels. Appearance of a considerable number of albumin-positive cells cultivated on the scaffold (47 ± 4%) as compared to the two-dimensional culture system (28 ± 6%) indicates the supporting role of the scaffold. The efficiency of the cells to produce albumin, urea, transferrin, serum glutamic pyruvic transaminase and serum oxaloacetate aminotransferase in hepatocytes on the scaffold further attest to the functionality of the cells. Conclusion: The data presented in this study show that the engineered nanofibrous scaffold is a conductive matrix which supports and enhances MSC development into functional hepatocyte-like cells.

Reconstruction of three-dimensional porous media using a single thin section.

Abstract: The purpose of any reconstruction method is to generate realizations of two- or multiphase disordered media that honor limited data for them, with the hope that the realizations provide accurate predictions for those properties of the media for which there are no data available, or their measurement is difficult. An important example of such stochastic systems is porous media for which the reconstruction technique must accurately represent their morphology---the connectivity and geometry---as well as their flow and transport properties. Many of the current reconstruction methods are based on low-order statistical descriptors that fail to provide accurate information on the properties of heterogeneous porous media. On the other hand, due to the availability of high resolution two-dimensional (2D) images of thin sections of a porous medium, and at the same time, the high cost, computational difficulties, and even unavailability of complete 3D images, the problem of reconstructing porous media from 2D thin sections remains an outstanding unsolved problem. We present a method based on multiple-point statistics in which a single 2D thin section of a porous medium, represented by a digitized image, is used to reconstruct the 3D porous medium to which the thin section belongs. The method utilizes a 1D raster path for inspecting the digitized image, and combines it with a cross-correlation function, a grid splitting technique for deciding the resolution of the computational grid used in the reconstruction, and the Shannon entropy as a measure of the heterogeneity of the porous sample, in order to reconstruct the 3D medium. It also utilizes an adaptive technique for identifying the locations and optimal number of hard (quantitative) data points that one can use in the reconstruction process. The method is tested on high resolution images for Berea sandstone and a carbonate rock sample, and the results are compared with the data. To make the comparison quantitative, two sets of statistical tests consisting of the autocorrelation function, histogram matching of the local coordination numbers, the pore and throat size distributions, multiple-points connectivity, and single- and two-phase flow permeabilities are used. The comparison indicates that the proposed method reproduces the long-range connectivity of the porous media, with the computed properties being in good agreement with the data for both porous samples. The computational efficiency of the method is also demonstrated.

Fractional-order hopfield neural networks

Abstract: This paper proposes Fractional-order Hopfield Neural Networks (FHNN). This network is mainly based on the classic well-known Hopfield net in which fractance components with fractional order derivatives, replace capacitors. Stability of FHNN is fully investigated through energy-like function analysis. To show how effective the FHNN network is, an illustrative example for parameter estimation problem of the second-order system is finally considered in the paper. The results of simulation are very promising.

Long-term open pit mine production planning: a review of models and algorithms

Abstract: Long-term production planning (LTPP) is a large-scale optimization problem that aims to find the block extraction sequence that produces the maximum possible net present value (NPV) whilst satisfying a variety of physical and economical constraints. The economic feasibility of a mine is highly dependent upon careful LTPP. As the mining industries extract deeper and lower grade ores, LTPP is becoming a key item that can result in ceasing operations or continuing the project. Mathematical programming models are well suited to optimizing LTPP of open pit mines. These mathematical models have been studied extensively in the literature since the 1960s. The result of this study shows that there are two approaches for dealing with LTPP problems: (1) deterministic and (2) uncertainty-based approaches. This paper first discusses the deterministic algorithms and then, after an introduction to uncertainty associated with mining projects, reviews uncertainty-based algorithms. The advantages and disadvantages of these...