Phototunable block copolymer hydrogels

2017 Fall.Includes bibliographical references.Thermoplastic elastomer (TPE) hydrogel networks, based on swelling of nanostructured blends of amphiphilic, sphere-forming AB diblock and ABA triblock copolymers, provide direct access to thermally processable plastics that exhibit exceptional elastic recovery and fatigue resistance even after hydration. In such two-component systems, the ratio of ABA to AB block copolymer (BCP) is used to control the resultant swelling ratio, system modulus, and overall mechanical response. This dissertation focuses on developing material strategies through which adjustment of such AB/ABA ratios, and thus the resultant properties, can be accomplished using light. The chapters within capture the manipulation of a photoreactive AB diblock copolymer micelle-like spheres to controllably generate ABA triblock copolymer and the network nanostructure in situ, both in the melt state and after dispersal in solution. This was accomplished using efficient photoinduced [4 + 4]cycloaddition (λ = 365 nm) between terminal anthracene units on a ω-anthracenylpolystyrene-b-poly(ethylene oxide) diblock copolymer precursor to produce the desired amount of polystyrene-b-poly(ethylene oxide)-b-polystyrene triblock copolymer. This direct, UV-mediated handle on tethering between adjacent micelles in the BCP matrix was found to be capable of controllably manipulating hydrogel material properties using (1) duration of irradiation, (2) hydration level and consequent micelle spacing upon exposure, and (3) photopatterning strategies to spatially direct swelling and mechanics. This level of control yielded an array of hydrogels, ranging from those irradiated in the dry melt to produce high-modulus, elastic materials suited for fibrocartilage repair and replacement, to moldable or injectable precursor solutions irradiated into soft, conformally shaped TPE hydrogels ideal for use in high contact applications such as wound healing. The development and scope of this versatile new photoactive BCP system is enclosed

Distributed antenna systems aspects and deployment

A lot of schemes are proposed to exploit the transmit diversity. Distributed antenna systems (DAS) constitute one of the most attractive schemes to efficiently achieve the stringent quality of service demands of next generation wireless networks. In this paper, we investigated MISO assisted different transmission techniques used in DAS and the performance of downlink multi-cell DAS in terms of capacity improvement using SINR for different transmission scheme. A system level simulation tool is used to analyze the performance

Supply response of potato in Bangladesh: a vector correction approach

An attempt has been made in this study to examine the supply response of potato in Bangladesh by using the vector error correction approach. The short-run price elasticity was 0.45 while the long run elasticity was 0.62. Price policies are effective in obtaining the desired level of output for potato. If intervention in the market is of necessity, then it must be implemented during the harvest season for altering price expectations. Also emphases should be given to increase potato export and establishing export oriented potato processing industries

10-(2-Pyrid­yloxy)phenanthren-9-ol

In the title compound, C19H13NO2, the pyridyl ring makes a dihedral angle of 87.04 (6)° with the plane of the phenanthrene ring system. In the crystal, mol­ecules are linked through weak inter­molecular C—H⋯O hydrogen bonds and C—H⋯π inter­actions

Tuning the magnetic and structural phase transitions of PrFeAsO via Fe/Ru spin dilution

Neutron diffraction and muon spin relaxation measurements are used to obtain a detailed phase diagram of Pr(Fe,Ru)AsO. The isoelectronic substitution of Ru for Fe acts effectively as spin dilution, suppressing both the structural and magnetic phase transitions. The temperature of the tetragonal-orthorhombic structural phase transition decreases gradually as a function of x. Slightly below the transition temperature coherent precessions of the muon spin are observed corresponding to static magnetism, possibly reflecting a significant magneto-elastic coupling in the FeAs layers. Short range order in both the Fe and Pr moments persists for higher levels of x. The static magnetic moments disappear at a concentration coincident with that expected for percolation of the J1-J2 square lattice model

Kac-Moody Symmetries of Ten-dimensional Non-maximal Supergravity Theories

A description of the bosonic sector of ten-dimensional N=1 supergravity as a non-linear realisation is given. We show that if a suitable extension of this theory were invariant under a Kac-Moody algebra, then this algebra would have to contain a rank eleven Kac-Moody algebra, that can be identified to be a particular real form of very-extended D_8. We also describe the extension of N=1 supergravity coupled to an abelian vector gauge field as a non-linear realisation, and find the Kac-Moody algebra governing the symmetries of this theory to be very-extended B_8. Finally, we discuss the related points for the N=1 supergravity coupled to an arbitrary number of abelian vector gauge fields