Iterative limit analysis of structures within a scaled boundary finite element framework

This paper presents an iterative elastic analysis approach to determine the collapse load limit of structures. The proposed scheme is based on the use of a modified elastic compensation method, where the structure is modeled within a scaled boundary finite element framework. The formulation takes the general form of polygon scaled boundary finite elements, which overcomes the challenges associated with stress singularities and complex geometries. The approach provides coarse mesh accuracy and numerical stability under incompressibility conditions, and is suitable for large scale problems that often require a large number of iterations to converge to the collapse load solution. A number of successfully solved examples, one of which has been given herein, illustrate the robustness and efficiency of the proposed method to compute the collapse load of structures

Investigating the Relationship between hs-CRP Serum Level and Insulin Resistance (HOMA IR) Six Weeks after Childbirth in Patients with Gestational Diabetes Mellitus

Background: Some patients with GDM (Gestational Diabetes Mellitus) still experience impaired glucose tolerance after childbirth and will be affected by diabetes mellitus type 2. Objectives: The aim of this study is to investigate the relationship between hs-CRP serum levels with insulin resistance six weeks after childbirth in patients with gestational diabetes mellitus type 2. Methods: In this descriptive cross-sectional study, 110 patients with GDM were evaluated in terms of the insulin resistance index (HOMA), hs-CRP serum, and the oral glucose tolerance test (OGTT) six weeks after childbirth. Their anthropometric indices were measured in the early pregnancy. Spearman’s rank correlation coefficient and linear regression analysis were used to analyze data in SPSS 16. Results: The mean of hs-CRP was 8.72 µg/ml among the patients in this study. It is higher than the normal range. Moreover, 24.5% of the patients were suffering from impaired glucose tolerance, and hs-CRP levels were higher than the normal range in 92.6% of these patients. Furthermore, 41.8% of patients showed insulin resistance, and hs-CRP levels were high among 73.9% of them. After age adjustment, the increase in hs-CRP serum level was significantly correlated with insulin resistance (HOMA) and the one-hour and two-hour OGTTs (p=0.007 and p<0.001, respectively). Conclusion: It appears that age adjustment can help us figure out the relationship between the increase in hs-CRP serum and insulin resistance in pregnant mothers with diabetes six weeks after childbirth

Conceptualising a Dynamic Technology Practice in Education Using Argyris and Schön's Theory of Action

Despite substantial national effort to integrate technology in education, it seems that practitioners in the education system are not working in line with the given policy. Evidence from large-scale studies of students’ technology practices at school over the last decade show disparities in student practices. The observed gap between the micro and the macro level call for a closer exploration. Research that explores the influence of social and organizational factors may be useful for understanding the processes behind such gaps. Argyris and Schön’s ‘Theory of Action’ (1978) is proposed as an example of an organizational theory that can be adopted in educational technology research to move towards understanding the complexities of technology practice. To encourage discourse and application of Argyris and Schön’s theory in the field of educational technology research, this paper introduces the theory, a review of its empirical application in research of teacher educations’ technology practice and relevant conceptual work. The paper presents a conceptual framework based on Argyris and Schön’s theory that has been developed through two recent studies, and invites its application in future research and development

A thermally responsive cationic nanogel-based platform for three-dimensional cell culture and recovery

Thermo-sensitive nanogels have attracted great interest due to their versatile biological applications, but little research has been carried out to study their abilities in three-dimensional (3D) cell culture and recovery. A new insight is reported into exploring a low-charged thermosensitive cationic nanogel, poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate-co-2-dimethylaminoethyl methacrylate) (P(NIPAM-HEMA-DMAEMA) or PNHD), for 3D cell culture. The positively charged DMAEMA moieties of the PNHD nanogels facilitate cellular attachment, and the low charge density renders those nanogels minimally cytotoxic. The volume phase transition temperatures (VPTTs) of the synthesized PNHD nanogels can be tailored by adjusting monomer feeds during the course of polymerization. Dynamic rheological measurements confirm the fully reversible sol–gel transition for 50 mg mL−1 PNHD nanogels. At room temperature, PNHD nanogels are in their dispersion states, allowing them to be thoroughly mixed with inoculated cells. Above their gelation temperatures, hydrogels containing a mixture of cells and nanogels are formed in situ. The increase in viable cells with culture time suggests that the in situ formed hydrogels support cell proliferation. Recovery of these cultured cells can be simply achieved by cooling the mixed hydrogels below their gelation temperature. The spherical shape of the released cells indicates their 3D growth in the absence of a physical scaffold. The released cells are not only alive, but also retain the capability of migration.Zheyu Shen, Amir Mellati, Jingxiu Bi, Hu Zhang, and Sheng Da

Iterative limit analysis of structures within a scaled boundary finite element framework

This paper presents an iterative elastic analysis approach to determine the collapse load limit of structures. The proposed scheme is based on the use of a modified elastic compensation method, where the structure is modeled within a scaled boundary finite element framework. The formulation takes the general form of polygon scaled boundary finite elements, which overcomes the challenges associated with stress singularities and complex geometries. The approach provides coarse mesh accuracy and numerical stability under incompressibility conditions, and is suitable for large scale problems that often require a large number of iterations to converge to the collapse load solution. A number of successfully solved examples, one of which has been given herein, illustrate the robustness and efficiency of the proposed method to compute the collapse load of structures

A biodegradable thermosensitive hydrogel with tuneable properties for mimicking three-dimensional microenvironments of stem cells

Employing stem cells in therapeutic applications strongly depends on the extracellular three-dimensional, D, microenvironment and cell carrier properties. In this work, chitosan-g-poly, N-isopropylacrylamide, CS-g-PNIPAAm, was synthesized as a stem cell mimicking microenvironment. The influence of various polymerization conditions, such as acid concentration, reaction temperature and monomer feed, on the grafting parameters of this thermo-responsive hydrogel, was systematically investigated. We found that the resulting copolymers with a small amount of long poly, N-isopropylacrylamide, PNIPAAm, side chains are low-soluble at low temperatures, but can form stronger hydrogels, almost, folds, at high temperatures, whereas copolymers with a high amount of short PNIPAAm side chains are more soluble at low temperatures, however, they cannot form strong hydrogels at high temperatures. In a physiological pH, an optimized balance between the solubility, as the pre-requirement for cell dispersion and injectability, of copolymers at ambient temperature and enhanced gel mechanical strength, as the essential parameter of stem cell microenvironments, at body temperature can be achieved through controlled reaction conditions. Mesenchymal stem cells, MSCs, were cultured in the CS-g-PNIPAAm hydrogels. Further analysis of confocal images confirms MSCs can maintain their viability and increase the cellular biomass inside hydrogels. Sectional analysis demonstrates that cells are uniformly distributed within the hydrogels. Our results confirm that the CS- g-PNIPAAm with manipulated properties could provide a potential, D microenvironment for stem cell culture, differentiation and in vivo injection.Amir Mellati, Sheng Dai, Jingxiu Bi, Bo Jin and Hu Zhan

Influence of polymer molecular weight on the in vitro cytotoxicity of poly (N-isopropylacrylamide)

Short CommunicationAbstract not availableAmir Mellati, Meisam Valizadeh Kiamahalleh, Sheng Dai, Jingxiu Bi, Bo Jin, Hu Zhan