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  • Novel Materials Based on Poly(2-Oxazoline): Synthesis, Molecular Characterization, and Application in Drug Delivery

    Alkattan, Nedah S. (2023-06-01) [Dissertation]
    Advisor: Hadjichristidis, Nikos
    Committee members: Nunes, Suzana Pereira; Khashab, Niveen M.; Avgeropoulos, Apostolos
    Poly(2-oxazolines) (POxs) are a class of polymers that have gained significant interest in biomedical applications. POxs are mainly synthesized using living cationic ring-opening polymerization (CROP) under microwave irradiation. POxs are considered pseudo-polypeptides because they are similar to polypeptides. Nevertheless, they are more chemically stable than polypeptides due to the presence of tertiary amides. POxs The major goal of this research is to synthesize and characterize a novel well-defined amphiphilic block copolymer based on POxs. These amphiphilic block copolymers can comprise core cross-linked star polymers (CCS) or linear block copolymers. This research demonstrates and describes the synthesis of poly(2-methyl-2-oxazoline-b-poly(2,2'-(1,4-phenylene)bis-2-oxazoline)-co-(2-n-2-butyl-2-oxazoline)(PMeOx-b-P(PhenBisOx-co-ButOx) amphiphilic core cross-linked star polymers (CCS) based on POxs. The CCS polymers are synthesized via sequential CROP in two steps by synthesizing Poly(2-methyl-2-oxazoline) (PMeOx) as the living arms followed by cross-linking of the core 2, 2’-(1,4-phenylene)bis-2-oxazoline (PhenBisOx) as the cross-linker and 2-n-butyl-2-oxazoline (ButOx) as a hydrophobic monomer to form the core of the CCS polymers. In addition, this research will clarify the other kinds of amphiphilic copolymers based on aggregation-induced emission (AIE) fluorophores, tetraphenylethylene (TPE) as an initiator that have been synthesized by a combination of cationic and anionic ROP. First, the difunctional initiator TPE-(OH)2 was synthesized via McMurry coupling reaction. Then, two kinds of triblock copolymers, TPE-poly(2-methyl-2-oxazoline)-b-poly(ε-caprolactone) (TPE-(PMeOx-b-PCL)2) and TPE-poly(ε-caprolactone)-b-poly(2-methyl-2-oxazoline) (TPE-(PCL-b-PMeOx)2), were synthesized by altering the sequence of polymerization. The resulting polymers, CCS polymers and the triblock copolymers were loaded with the anticancer drug doxorubicin (DOX) and their in vitro properties, cytotoxicity, and drug release at different pH were studied. Furthermore, the resulting polymers were characterized by size exclusion chromatography (SEC), nuclear magnetic resonance (NMR), dynamic light scattering (DLS), and transmission electron microscopy (TEM). All results in this research showed that the amphiphilic block copolymers, the CCS polymers and the triblock copolymers could be suitable carriers for drug delivery systems.
  • Implementing structural equation modelling and multiple mediator models for management information systems

    Osman, Esam; Hardaker, Glenn; Glenn, Liyana Eliza (The International Journal of Information and Learning Technology, Emerald, 2022-12-05) [Article]
    Purpose Overall quantitative research aims to observe certain fundamental principles of logic and scientific frame of reasoning. There continues to be challenges on how quantitative research is conducted in the field of information systems. Design/methodology/approach Structured equation modelling (SEM) research identifies concerns about the standard of scientific enquiry method, the issue of the misconception of sustaining the consequent and the issue of collective validity. Therefore, rigor and robustness in instrument validity, constructs validity and path analysis validity maybe better achieved by attending to these three concerns. Measuring a multiple mediator construct in a hypothetical model continues to be a challenge for researchers in information systems research and related fields. Findings This paper aims to provide a thoughtful assessment of the contemporary issues of structural equation modelling methodology (SEMM), by providing rigid and robust SEMM that has several stages in specifying valid multiple mediators construct and the process to measuring in a path analysis model. This paper attempts to develop each stage of the methodology using relevant research to construct a methodology specified to test effects in multiple mediators in SEM using AMOS software. The methodology developed contains the two main phases; first is prior to data collection phase and the second phase is after the data collection, the use of this methodology design, for implementation, intended to support high methodological standards and subsequent quality in MIS research findings. Originality/value The research paper provides SEMM that has several stages in specifying valid multiple mediators construct and the process to measuring in a path analysis model.
  • Complex systems engineering theory is a scientific theory

    Feron, Eric (2022-12-05) [Technical Report]
    The proper design of complex engineering systems is what allows corporations and nations to distinguish themselves in a global competition for technical excellence and economic well-being. After quickly reviewing the central elements of systems engineering, we map all of them onto concepts of mathematics such as theorems and proofs, and onto scientific theories. This mapping allows the protagonists of complex systems engineering and design to map existing techniques from one field to the others; it provides a surprising number of suggestions for improving system design, especially system architecture, by leveraging advanced mathematical and / or scientific concepts in a productive way. In return, mathematicians and computer scientists can benefit from this bridge by bringing to bear many of their automated theorem provers to help with the design of complex systems. Clear classifications of what is "hard" and what is "easy" in mathematical proofs can instantaneously map onto similar appreciations for system design and its reliance on engineers’ creativity. Last, understanding system design from the mathematical-scientific viewpoint can help the system engineer think more maturely about organizing the multitude of tasks required by systems engineering.
  • Impact of layer thickness on the operating characteristics of In2O3/ZnO heterojunction thin-film transistors featured

    Alghamdi, Wejdan S.; Fakieh, Aiman; Faber, Hendrik; Lin, Yen-Hung; Lin, Wei-Zhi; Lu, Po-Yu; Liu, Chien-Hao; Salama, Khaled N.; Anthopoulos, Thomas D. (Applied Physics Letters, AIP Publishing, 2022-12-05) [Article]
    Combining low-dimensional layers of dissimilar metal oxide materials to form a heterojunction structure offers a potent strategy to improve the performance and stability of thin-film transistors (TFTs). Here, we study the impact of channel layer thicknesses on the operating characteristics of In2O3/ZnO heterojunction TFTs prepared via sputtering. The conduction band offset present at the In2O3/ZnO heterointerface affects the device's operating characteristics, as is the thickness of the individual oxide layers. The latter is investigated using a variety of experimental and computational modeling techniques. An average field-effect mobility (μFE) of >50 cm2 V−1 s−1, accompanied by a low threshold voltage and a high on/off ratio (∼108), is achieved using an optimal channel configuration. The high μFE in these TFTs is found to correlate with the presence of a quasi-two-dimensional electron gas at the In2O3/ZnO interface. This work provides important insight into the operating principles of heterojunction metal oxide TFTs, which can aid further developments.
  • Correct estimation of permeability using experiment and simulation

    Khirevich, Siarhei; Yutkin, Maxim; Patzek, Tadeusz (Physics of Fluids, AIP Publishing, 2022-12-05) [Article]
    Estimation of permeability of porous media dates back to Henry Darcy [H. Darcy, Les Fontaines Publiques de la Ville de Dijon (Victor Dalmont, 1856)], and its knowledge is essential in many scientific and engineering endeavors. Despite apparent simplicity of permeability measurements, the literature data are scattered, and this scatter not always can be attributed to the precision of experiment or simulation or to sample variability. Here, we demonstrate an excellent agreement (<1%) between experiments and simulations, where experimental results are extensive and stable, while flow is simulated from first principles, directly on three-dimensional images of the sample, and without fitting parameters. Analyzing when experiments and simulations agree reveals a major flaw affecting many experimental measurements with the out-of-sample placement of pressure ports, including industry standards. The flaw originates from (1) incorrect calculation of the applied pressure gradient, (2) omitting virtual part of the measured system, and (3) pressure loss at the sample–tube contact. Contrary to common wisdom, the relative magnitude of (3) is defined by the sample–tube diameter ratio and is independent of the size of sample pores. Our findings are applicable to a wide range of permeability measurements, including geological-sample-type (Hassler cell) and membrane-type. The reported pressure loss (3) also affects two-phase flow measurements, such as capillary pressure estimation. Removing or taking the flaw into account advances the understanding and control of flow-related processes in complex geometries.

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