Finite element modeling of electrospun nanofibre mesh using microstructure architecture analysis

This investigation is aimed at modeling the tensile behavior of electrospun polyurethane (PU) membrane. The PU web is produced with different morphologies and the structural parameters are studied through SEM images. Three-dimensional network is simulated using ABAQUS software. Each fibre is modeled as hyperelastic material and each crosslink is modeled as multi point constrain tie. The stress-strain behavior of PU mat is modeled by finite element method, and the effect of fibre diameter, fibre orientation and thickness of web is investigated. The stress–strain curves of networks at three different morphologies are compared with modeling measurements. The model by using third order reduced polynominal as fibre hyperelastic potential energy function shows good agreement with experimental findings which confirm that the tensile behavior of PU web can be explained entirely by microstructure of the network

Finite element modeling of electrospun nanofibre mesh using microstructure architecture analysis

83-88This investigation is aimed at modeling the tensile behavior of electrospun polyurethane (PU) membrane. The PU web is produced with different morphologies and the structural parameters are studied through SEM images. Three-dimensional network is simulated using ABAQUS software. Each fibre is modeled as hyperelastic material and each crosslink is modeled as multi point constrain tie. The stress-strain behavior of PU mat is modeled by finite element method, and the effect of fibre diameter, fibre orientation and thickness of web is investigated. The stress–strain curves of networks at three different morphologies are compared with modeling measurements. The model by using third order reduced polynominal as fibre hyperelastic potential energy function shows good agreement with experimental findings which confirm that the tensile behavior of PU web can be explained entirely by microstructure of the network

Detection sensitivity of lymph nodes of various sizes using USPIO nanoparticles in magnetic resonance imaging

Ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles-based magnetic resonance imaging (MRI) have offered new promise for early detection of lymph nodes and their metastases. These nanoparticles are taken up by macrophages in normal lymph nodes and produce signal changes based on susceptibility artifact and dipolar relaxation. The effects of MR protocols and their parameters on artifact size and detection sensitivity have been studied before. In this study USPIO nanoparticles were used as MRI contrast agent, and their detection sensitivity in axillary lymph nodes was evaluated using earlier defined pulse sequences. The minimum amount (dose) of USPIO nanoparticles that delineates lymph nodes of various sizes using susceptibility-based gradient echo pulse sequences was also determined. It was found that a dose administration of as low as 0.028 mg iron (Fe)/kg for subcutaneous injection and 0.16 mg Fe/kg for intravenous injection can be used to visualize axillary lymph nodes when a sensitive MR protocol is employed. From the Clinical Editor: Ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles are taken up by macrophages and have been shown to be promising negative contrast agents in the early detection of metastases in lymph nodes. In this study, their detection sensitivity in axillary lymph nodes was evaluated using previously defined MRI pulse sequences. The minimum dose of USPIO to delineate lymph nodes using gradient echo-based optimized pulse sequences was 0.028 mgFe/kg for subcutaneous and 0.16 mgFe/kg for intravenous injection. © 2010 Elsevier Inc. All rights reserved

Chloroplast genome diversity of the Pyrus genus; from Iranian and European wild pear species to the cultivated cultivars.

The genome structure of chloroplast DNA (cpDNA) is highly conserved among the different species belonging to the Pyrus genus. In spite of the relevance of this genetic material for phylogenesis because of its maternal inheritance, molecular data on these species are very scanty. In order to investigate phylogenetic relationship in the genus Pyrus, we recognized three hyper variable regions in intergenic spacers of cpDNA of 73 Iranian and European pear (Pyrus communis L.) local cultivars and wild genotypes, plus 9 Japanese pear genotypes (Pyrus pyrifolia, syn. P. serotina) and one Chinese pear (P. × bretschneideri). CAPS markers were developed by digesting PCR products separately with 3 restriction enzymes and the relative patterns were used for a cluster analysis. Results evidenced that Iranian and European pear cultivars were divided into five groups, whereas Japanese pear cultivars were grouped together with Iranian pear genotypes. This evidence supports the hypothesis of a significant genetic contribution in the Iranian wild genotypes from Japanese pear, brought to this region in ancient times through the main routes of the Silk Road

Contribution of Western and Eastern species to the Iranian pear germplasm revealed by the characterization of S-genotypes.

Iran is recognized as an important source of genetic diversity of pear germplasm including native and introduced species. It is located in the Mid-Asian, center of diversification of the genus Pyrus, where several species have originated; moreover, the Silk Road historically favoured an intense exchange of cultivated crops and agricultural technologies during the course of trade and cultural transmission between ancient China and central/West Asia. Thus, Iran is maybe one of the first places where specimens of Pyrus communis imported from Europe could have come into contact with Pyrus pyrifolia, syn. P. serotina genotypes coming from eastern Asian countries. Moreover, pear species exhibit the S-RNase-based gametophytic self-incompatibility system that prevents self-fertilization thus forcing out-crossing. Since there is no major barrier for hybridization in Pyrus, several different species might have contributed to the makeup of the Iranian traditional germplasm. The characterization of self-incompatibility ribonucleases in Iranian P. communis cultivars and landrace genotypes revealed that, in addition to the pool of alleles previously detected in European cultivars, the Iranian germplasm shows the presence of alleles most likely introduced via hybridization with cultivated or wild Pyrus species