A stretchy, rubber-like biomaterial based on alginate derived from seaweed could overcome the shortcomings of conventional polyurethanes, which are used in the repair of damaged or diseased cardiac and vascular tissue [Daemi et al., Biomaterials 84 (2016) 54]. Polyurethanes represent an important biomaterial but are not biodegradable, are derived from petroleum-based raw materials, and do not promote the adherence and growth of cells. So a team of researchers from Iran Polymer & Petrochemical Institute, Royan Institute, University of Science and Culture in Iran, University of the Basque Country, and Harvard Medical School has come up with a novel approach. “We used alginate as a green, easily available and low-cost polysaccharide and combined it chemically with polyurethane to obtain a novel bio-based supramolecular ionic polymeric network,” explains Mehdi Barikani of the Iran Polymer & Petrochemical Institute. The novel biomaterial, known as alginate-based supramolecular ionic polyurethane (or ASPU), has tunable mechanical properties that depend upon the amount of alginate. Unlike previously reported bio-elastomers, ASPU contains physical crosslinks instead of chemical ones between its constituent parts that make it much more biodegradable in physiological conditions. Even though ASPU is biodegradable, it is exceptionally strong and tough – showing up to ten times the tensile strength of most synthetic biodegradable polymers. In fact, its toughness (190 kJ/m3) and tensile strength (50 MPa) is comparable to that of human tendons, ligaments, and cartilage. The novel biomaterial is also self-healing, the researchers have found, and can rapidly recover almost completely after rupture. Barikani, Hossein Baharvand and their colleagues believe that the outstanding mechanical properties of ASPU are down to the alterations that alginate makes to the microstructure of the elastomer. The amorphous nature of alginate reduces the overall crystallinity of polyurethane, which is demonstrated by the increased transparency of the material. “All of the interesting features of this biodegradable elastomer, including tunable biodegradation and strange mechanical properties combined with fast self-healing, make it ideal for future tissue engineering applications,” says Baharvand of the Royan Institute. “In addition, this material is biocompatible and… shows a minimal immune response in physiological conditions.” The researchers believe that there are no major obstacles to the adoption of ASPU for tissue engineering since alginate is already approved by the FDA for some applications, all the raw materials are commercially available and cost effective, and synthesis is performed under mild conditions. “[We] expect that our biodegradable elastomers will result in new applications for tissue engineering of load-bearing tissues,” Baharvand told Materials Today. The biomaterial has been tested in animal models and the researchers hope to move onto human clinical trials in the near future.
Esmaeili-Choobar N.,Islamic Azad University at Tabriz |
Esmaeili-Falak M.,Islamic Azad University at Tabriz |
Roohi-Hir M.,Islamic Azad University at Tabriz |
Keshtzad S.,University of Science and Culture
Electronic Journal of Geotechnical Engineering | Year: 2013
mechanisms, identified as soils of great importance. In contrast to the previous imaginations, presence of collapsible soils is not limited to dry climates, but they are likely present all over the earth. Because of increase in water content and due to engineering constructions under a constant stress, these soils can experience considerable settlements. In this research collapsibility potential of soils in Talesh (a county in northern Iran) has been evaluated. Assessment of collapsibility potential of under consideration soils has been done using experimental criteria and the standard based on double consolidation test (ASTM D 5333- 03). Results from these investigations show that soils in some areas have average to high collapsibility potentials. Also the importance of various parameters on collapsible potential has been investigated. © 2013, EJGE.
Harati M.,University of Science and Culture |
Sabet A.H.,Islamic Azad University at Bandar Anzali |
Modaraei A.H.,Islamic Azad University at Bandar Anzali
Journal of Engineering and Applied Sciences | Year: 2016
Past severe earthquakes such as Bam earthquake of 2003 and Tabas earthquake of 1978 have demonstrated that many cities in Iran are prone to be struck by near-fault earthquakes. Such earthquakes are impulsive in nature and therefore, they are more destructive than the ordinary ground shaking. In the 4th edition of Iranian Seismic Code (Standard No. 2800), some changes including a modification factor for the Elastic Acceleration Response Spectrum (EARS) have been recently recommended to reflect the effects of such probable near-fault earthquakes for the designing procedure. In this study, a numbers of 2D RC Moment Resisting Frames (MRFs) from 4-12 story buildings are designed linearly based on Iranian National Building Code (USTBC) and Standard No. 2800 as well. Subsequently their nonlinear models are reproduced for conducting Non-linear Dynamic Time History (NDTH) analysis. For this purpose, twenty impulsive ground motions are selected and scaled to be compatible with the Designed Based Earthquake (DBE) spectrum of the above mentioned code. It is concluded that the seismic performance of the analyzed structures are not satisfactory at all; no buildings are successful to satisfy the Life Safety (LS) performance level posed by guidelines such as ASCE41-06 or ASCE41-13. Moreover, it is worth mentioning that even Collapse Prevention (CP) limit states are not also met in some cases. Therefore, the recently added modifications in the Standard No. 2800 may be inadequate to incorporatethe near-fault earthquakes' effects. At the end some recommendations are addressed for the design of structures built in the regions vulnerable to be attacked by near-fault earthquakes. © Medwell Journals, 2016.
Algergawy A.,Friedrich - Schiller University of Jena |
Algergawy A.,Tanta University |
Babalou S.,University of Science and Culture |
Konig-Ries B.,Friedrich - Schiller University of Jena
CEUR Workshop Proceedings | Year: 2016
As ontologies are the backbone of the Semantic Web, they attract much attention from researchers and engineers in many domains. This results in an increasing number of ontologies and semantic web applications. The number and complexity of such ontologies makes it hard for developers of ontologies and tools to decide which ontologies to use and reuse. To simplify the problem, a modularization algorithm can be used to partition ontologies into sets of modules. In order to evaluate the quality of modularization, we propose a new evaluation metric that quantifies the goodness of ontology modularization. In particular, we investigate the ontology module homogeneity, which assesses module cohesion, and the ontology module heterogeneity, which appraises module coupling. The experimental results demonstrate that the proposed metric is effective.
Kamali S.,Ferdowsi University of Mashhad |
Kamali S.,University of Science and Culture |
Karimi J.,Ferdowsi University of Mashhad |
Hosseini M.,Ferdowsi University of Mashhad |
And 3 more authors.
Biocontrol Science and Technology | Year: 2013
Entomopathogenic nematodes (EPNs) from the families Steinernematidae and Hererorhabditidae are considered excellent biological control agents against many insects that damage the roots of crops. In a regional survey, native EPNs were isolated, and laboratory and greenhouse experiments were conducted to determine the infectivity of EPNs against the cucurbit fly, Dacus ciliatus Loew (Diptera: Tephritidae). Preliminary experiments showed high virulence by a native strain of Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae) and a commercial strain of Steinernema carpocapsae Weiser (Rhabditida: Steinernematidae). These two strains were employed for further analysis while another native species, Steinernema feltiae, was excluded due to low virulence. In laboratory experiments, larvae and adult flies were susceptible to nematode infection, but both nematode species induced low mortality on pupae. S. carpocapsae had a significantly lower LC50 value against larvae than H. bacteriophora in filter paper assays. Both species of EPNs were effective against adult flies but S. carpocapsae caused higher adult mortality. When EPN species were applied to naturally infested fruit (150 and 300 IJs/cm2), the mortality rates of D. ciliatus larvae were 28% for S. carpocapsae and 12% for H. bacteriophora. Both EPN strains successfully reproduced and emerged from larvae of D. ciliates. In a greenhouse experiment, H. bacteriophora and S. carpocapsae had similar effects on fly larvae. Higher rates of larval mortality were observed in sandy loam and sand soils than in clay loam. The efficacy of S. carpocapsae and H. bacteriophora was higher at 25 and 30°C than at 19°C. The results indicated that S. carpocapsae had the best potential as a biocontrol agent of D. ciliatus, based on its higher virulence and better ability to locate the fly larvae within infected fruits. © 2013 Taylor & Francis.