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Silvana Alfei,Sara Castellaro 한국고분자학회 2017 Macromolecular Research Vol.25 No.12
Macromolecular systems with well-defined sizes, shapes and high controlled architecture like dendrimers are of eminent interest in nanomedical applications such as drug delivery, gene transfection, and imaging. In this paper versatile protocols for the synthesis of polyester-based, hydrolysable, polycationic dendrimers have been setup. Fourth and fifth generation dendrimers equipped with several peripheral hydroxyl groups were prepared from 2, 2-bis(hydroxymethyl)propanoic acid. They were successfully esterified with arginine alone or mixed with lysine or O-methyltyrosine and with dipeptide arginine-glycine and seven polycationic dendrimers were finally obtained as hydrochlorides. Their structures and composition were confirmed by NMR analysis and by experimental molecular weight computed by volumetric titration and their buffer capacity was higher than fourth generation polyamidoamine (G4- PAMAM) derivatives taken as reference. The synthesized dendrimers harmonize a polycationic character and a buffer capacity which presuppose a good transfection efficiency with a degradable scaffold thus appearing as a promising team of new non-toxic vectors for biomedical applications.
Shear transfer mechanism in connections involving concrete filled steel columns under shear forces
Silvana De Nardin 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.28 No.4
This paper reports the experimental results of three through bolt beam-column connections under pure shear forces using modified push-out tests. The investigated specimens include extended end-plates and six through-bolts connecting square concrete-filled steel tubular column (S-CFST) to steel beams. The main goal of this study is to investigate if and how the mechanical shear connectors, such as steel angles and stud bolts, contribute to the shear transfer mechanisms in the steel-concrete interface of the composite column. The contribution of shear studs and steel angles to improve the shear resistance of steel-concrete interface in through-bolt connections was investigated using tests. The results showed that their contribution is not significant when the beam-column connection is included in the push-out tests. The specimens failed by pure shear of the long bolts, and the ultimate load can be predicted using the shear resistance of the bolts under shear forces. The predicted values of load allowed obtaining a good agreement with the tests results.
An experimental study of connections between I-beams and concrete filled steel tubular columns
Silvana De Nardin,Ana Lucia H. C. El Debs 국제구조공학회 2004 Steel and Composite Structures, An International J Vol.4 No.4
Frame composed of concrete-filled steel tubular columns and I-shaped steel beam has been researched in order to development reasonable connection details. The present paper describes the results of an experimental program in four different connection details. The connection details considered include through-bolt between I-shaped steel beams and concrete-filled steel tubular columns and two details of welded connections. One of the welded connection details is stiffened by angles welded in the interior of the profile wall at the beam flange level. The specimens were tested in a cruciform loading arrangement with variable monotonic loading on the beams and constant compressive load on the column. For through-bolt details, the contribution of friction and bearing were investigated by embedding some of the bolts in the concrete. The results of the tests show that through-bolt connection details are very ductility and the bearing is not important to the behavior of these moment connections. The angles welded in the interior of the profile wall increase the strength and stiffness of the welded connection detail. In addition, the behavior curves of these connections are compared and some interesting conclusions are drawn. The results are summarized for the strength and stiffness of each connection.
Russia and China in the 21st century. Moving towards cooperative behaviour
Silvana Malle 한양대학교 아태지역연구센터 2017 Journal of Eurasian Studies Vol.8 No.2
Political and economic rapprochement is taking place between Russia and China in a number of fields: energy, arms production, trade in national currencies and strategic projects in transport and supporting infrastructure. This development, fostered by Western policies and actions, including sanctions related to Ukraine, appears to be strengthening despite reservations related to uneasy precedents, contrasting visions and uncertain economic projections. Chinese policies aiming at European markets via the revival of the Silk Road assist this development. The One Belt-One Road is projected as an alternative, or supplement, to the maritime routes made unsafe by contiguous countries' unrest, criminality and the assertive control of the seas by the United States. While Russia, promoting friendly investment structures, moves eastwards to develop the Russian Far East bordering China, the latter expands westwards engaging in laborious negotiations with Central Asian countries and costly investments in infrastructure and logistics. In each area, the article maintains that both countries, despite economic and political competition and fear of losing control, have interest in cooperation and discusses the areas where this is taking place, albeit slowly and with difficulty. Whether economic cooperation can develop into a strategic alliance including defence is discussed in the light of joint military exercises, arms trade and plans to broaden the scope of the Collective Security Treaty Organisation, the Shanghai Cooperation Organisation (of which India and Pakistan have recently become members), and the Common ASEAN Community. This path is difficult and marred by members' conflicting interests. But some positive outcomes should not be ruled out.
Shear transfer mechanisms in composite columns: an experimental study
Silvana De Nardin,Ana Lucia H. C. El Debs 국제구조공학회 2007 Steel and Composite Structures, An International J Vol.7 No.5
In the design of concrete filled composite columns, it is assumed that the load transfer between the steel tube and concrete core has to be achieved by the natural bond. However, it is important to investigate the mechanisms of shear transfer due to the possibility of steel-concrete interface separation. This paper deals with the contribution of headed stud bolt shear connectors and angles to improve the shear resistance of the steel-concrete interface using push-out tests. In order to determine the influence of the shear connectors, altogether three specimens of concrete filled composite column were tested: one without mechanical shear connectors, one with four stud bolt shear connectors and one with four angles. The experimental results showed the mechanisms of shear transfer and also the contribution of the angles and stud bolts to the shear resistance and the force transfer capacity.
( Silveira Silvana T. ),( Sabrine Gemelli ),( Jeferson Segalin ),( Adriano Brandelli ) 한국미생물 · 생명공학회 2012 Journal of microbiology and biotechnology Vol.22 No.6
Keratinases are exciting keratin-degrading enzymes; however, there have been relatively few studies on their immobilization. A keratinolytic protease from Chryseobacterium sp. kr6 was purified and its partial sequence determined using mass spectrometry. No significant homology to other microbial peptides in the NCBI database was observed. Certain parameters for immobilization of the purified keratinase on chitosan beads were investigated. The production of the chitosan beads was optimized using factorial design and surface response techniques. The optimum chitosan bead production for protease immobilization was a 20 g/l chitosan solution in acetic acid [1.5% (v/v)], glutaraldehyde ranging from 34 g to 56 g/l, and an activation time between 6 and 10 h. Under these conditions, above 80% of the enzyme was immobilized on the support. The behavior of the keratinase loading on the chitosan beads surface was well described using the Langmuir model. The maximum capacity of the support (qm) and dissociation constant (Kd) were estimated as 58.8 U/g and 0.245 U/ml, respectively. The thermal stability of the immobilized enzyme was also improved around 2-fold, when compared with that of the free enzyme, after 30 min at 65oC. In addition, the activity of the immobilized enzyme remained at 63.4% after it was reused five times. Thus, the immobilized enzyme exhibited an improved thermal stability and remained active after several uses.