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  • Molecular Diversity Preservation International  (10)
  • American Institute of Physics (AIP)
  • Blackwell Science Inc
  • 2020-2022  (10)
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  • 1
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    Fractionation of Lignin for Selective Shape Memory Effects at Elevated Temperatures (2020)
    Molecular Diversity Preservation International
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    Publication Date: 2020-04-20
    Description: We report a facile approach to control the shape memory effects and thermomechanical characteristics of a lignin-based multiphase polymer. Solvent fractionation of a syringylpropane-rich technical organosolv lignin resulted in selective lignin structures having excellent thermal stability coupled with high stiffness and melt-flow resistance. The fractionated lignins were reacted with rubber in melt-phase to form partially networked elastomer enabling selective programmability of the material shape either at 70 °C, a temperature that is high enough for rubbery matrix materials, or at an extremely high temperature, 150 °C. Utilizing appropriate functionalities in fractionated lignins, tunable shape fixity with high strain and stress recovery, particularly high-stress tolerance were maintained. Detailed studies of lignin structures and chemistries were correlated to molecular rigidity, morphology, and stress relaxation, as well as shape memory effects of the materials. The fractionation of lignin enabled enrichment of specific lignin properties for efficient shape memory effects that broaden the materials’ application window. Electron microscopy, melt-rheology, dynamic mechanical analysis and ultra-small angle neutron scattering were conducted to establish morphology of acrylonitrile butadiene rubber (NBR)-lignin elastomers from solvent fractionated lignins.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Molecular Diversity Preservation International
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  • 2
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    Impact of Surface Chemistry and Doping Concentrations on Biofunctionalization of GaN/Ga‒In‒N Quantum Wells (2020)
    Molecular Diversity Preservation International
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    Publication Date: 2020-07-28
    Description: The development of sensitive biosensors, such as gallium nitride (GaN)-based quantum wells, transistors, etc., often makes it necessary to functionalize GaN surfaces with small molecules or even biomolecules, such as proteins. As a first step in surface functionalization, we have investigated silane adsorption, as well as the formation of very thin silane layers. In the next step, the immobilization of the tetrameric protein streptavidin (as well as the attachment of chemically modified iron transport protein ferritin (ferritin-biotin-rhodamine complex)) was realized on these films. The degree of functionalization of the GaN surfaces was determined by fluorescence measurements with fluorescent-labeled proteins; silane film thickness and surface roughness were estimated, and also other surface sensitive techniques were applied. The formation of a monolayer consisting of adsorbed organosilanes was accomplished on Mg-doped GaN surfaces, and also functionalization with proteins was achieved. We found that very high Mg doping reduced the amount of surface functionalized proteins. Most likely, this finding was a consequence of the lower concentration of ionizable Mg atoms in highly Mg-doped layers as a consequence of self-compensation effects. In summary, we could demonstrate the necessity of Mg doping for achieving reasonable bio-functionalization of GaN surfaces.
    Electronic ISSN: 1424-8220
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Published by Molecular Diversity Preservation International
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  • 3
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    Recent Advances in Nanomaterial-Based Wound-Healing Therapeutics (2020)
    Molecular Diversity Preservation International
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    Publication Date: 2020-05-30
    Description: Nanomaterial-based wound healing has tremendous potential for treating and preventing wound infections with its multiple benefits compared with traditional treatment approaches. In this regard, the physiochemical properties of nanomaterials enable researchers to conduct extensive studies on wound-healing applications. Nonetheless, issues concerning the use of nanomaterials in accelerating the efficacy of existing medical treatments remain unresolved. The present review highlights novel approaches focusing on the recent innovative strategies for wound healing and infection controls based on nanomaterials, including nanoparticles, nanocomposites, and scaffolds, which are elucidated in detail. In addition, the efficacy of nanomaterials as carriers for therapeutic agents associated with wound-healing applications has been addressed. Finally, nanomaterial-based scaffolds and their premise for future studies have been described. We believe that the in-depth analytical review, future insights, and potential challenges described herein will provide researchers an up-to-date reference on the use of nanomedicine and its innovative approaches that can enhance wound-healing applications.
    Electronic ISSN: 1999-4923
    Topics: Chemistry and Pharmacology
    Published by Molecular Diversity Preservation International
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  • 4
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    A New Nano-Platform of Erythromycin Combined with Ag Nano-Particle ZnO Nano-Structure against Methicillin-Resistant Staphylococcus aureus (2020)
    Molecular Diversity Preservation International
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    Publication Date: 2020-09-02
    Description: Nano-particles have been combined with antibiotics in recent studies to overcome multidrug-resistant bacteria. Here, we synthesized a nano-material in which Ag nano-particles were assembled with a ZnO nano-structure to form an Ag-ZnO (AZO) nano-composite at low temperature. This material was combined with erythromycin (Ery), an antibiotic effective towards gram-positive bacteria, using three different approaches (AZO + Ery (AZE) [centrifuged (AZE1), used separately after 1-h gap (AZE2), without centrifugation (AZE3)]) to prepare a nano-antibiotic against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA). X-ray diffraction analysis and transmission electron microscopy confirmed the presence of Ag nano-particles and ZnO nano-structure. The elemental and chemical state of the elements present in the AZO nano-composite were assessed by X-ray photoelectron spectroscopy. The antibacterial activity of AZE samples against both Escherichia coli and S. aureus strains including MRSA was evaluated in antibacterial and morphological analyses. The AZE3 sample showed greater antibacterial activity than the other samples and was comparable to erythromycin. AZE3 was ~20-fold less prone to developing bacterial resistance following multiple exposures to bacteria compared to erythromycin alone. The AZE3 nano-composite showed good biocompatibility with 293 human embryonic kidney cells. Our newly synthesized nano-platform antibiotics may be useful against multidrug-resistant gram-positive bacteria.
    Electronic ISSN: 1999-4923
    Topics: Chemistry and Pharmacology
    Published by Molecular Diversity Preservation International
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  • 5
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    Effect of Prestrain on the Actuation Characteristics of Dielectric Elastomers (2020)
    Molecular Diversity Preservation International
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    Publication Date: 2020-11-16
    Description: Dielectric elastomers (DEs) represent a class of electroactive polymers that deform due to electrostatic attraction between oppositely charged electrodes under a varying electric field. Over the last couple of decades, DEs have garnered considerable attention due to their much-coveted actuation properties. As far as the precise measurement systems are concerned, however, there is no standard instrument or interface to quantify various related parameters, e.g., actuation stress, strain, voltage and creeping etc. In this communication, we present an in-depth study of dielectric actuation behavior of dielectric rubbers by the state-of-the-art “Dresden Smart Rubber Analyzer” (DSRA), designed and developed in-house. The instrument allowed us to elucidate various factors that could influence the output efficiency of the DEs. Herein, several non-conventional DEs such as hydrogenated nitrile rubber, nitrile rubber with different acrylonitrile contents, were employed as an electro-active matrix. The effect of viscoelastic creeping on the prestrain, molecular architecture of the matrices, e.g., nitrile content of nitrile-butadiene rubber (NBR) etc., are also discussed in detail.
    Electronic ISSN: 2073-4360
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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  • 6
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    A New Surface Charge Neutralizing Nano-Adjuvant to Potentiate Polymyxins in Killing Mcr-1 Mediated Drug-Resistant Escherichia coli (2021)
    Molecular Diversity Preservation International
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    Publication Date: 2021-02-11
    Description: Resistance to polymyxins when treating multidrug-resistant (MDR) Gram-negative bacterial infections limit therapeutic options. Here, we report the synthesis of a nickel (Ni) doped Zinc oxide (NZO) combined with black phosphorus (BP) (NZB) nanocomposite and its synergistic action with polymyxin B (PolB) against polymyxin-resistant Escherichia coli harboring mobilized colistin resistance (mcr-1) gene. NZB and PolB combination therapy expressed a specific and strong synergy against Mcr-1 expressing E. coli cells. The underlying mechanism of the synergy is the charge neutralization of the E. coli cell surface by NZB, resulting in a more feasible incorporation of PolB to E. coli. The synergistic concentration of NZB with PolB was proved biocompatible. Thus, the NZB is the first biocompatible nano-adjuvant to polymyxins against polymyxin-resistant E. coli cells, recognizing the physical status of bacteria instead of known adjuvants targeting cellular gene products. Therefore, NZB has the potential to revive polymyxins as leading last-resort antibiotics to combat polymyxin-resistant Gram-negative bacterial infections.
    Electronic ISSN: 1999-4923
    Topics: Chemistry and Pharmacology
    Published by Molecular Diversity Preservation International
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  • 7
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    Role of Chemistry and Crystal Structure on the Electronic Defect States in Cs-Based Halide Perovskites (2021)
    Molecular Diversity Preservation International
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    Publication Date: 2021-02-22
    Description: The electronic structure of a series perovskites ABX3 (A = Cs; B = Ca, Sr, and Ba; X = F, Cl, Br, and I) in the presence and absence of antisite defect XB were systematically investigated based on density-functional-theory calculations. Both cubic and orthorhombic perovskites were considered. It was observed that for certain perovskite compositions and crystal structure, presence of antisite point defect leads to the formation of electronic defect state(s) within the band gap. We showed that both the type of electronic defect states and their individual energy level location within the bandgap can be predicted based on easily available intrinsic properties of the constituent elements, such as the bond-dissociation energy of the B–X and X–X bond, the X–X covalent bond length, and the atomic size of halide (X) as well as structural characteristic such as B–X–B bond angle. Overall, this work provides a science-based generic principle to design the electronic states within the band structure in Cs-based perovskites in presence of point defects such as antisite defect.
    Electronic ISSN: 1996-1944
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 8
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    Influence of Ultraviolet Radiation on Mechanical Properties of a Photoinitiator Compounded High Vinyl Styrene–Butadiene–Styrene Block Copolymer (2021)
    Molecular Diversity Preservation International
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    Publication Date: 2021-04-15
    Description: Ultraviolet curing of elastomers is a special curing technique that has gained importance over the conventional chemical crosslinking method, because the former process is faster, and thus, time-saving. Usually, a suitable photoinitiator is required to initiate the process. Ultraviolet radiation of required frequency and intensity excites the photoinitiator which abstracts labile hydrogen atoms from the polymer with the generation of free radicals. These radicals result in crosslinking of elastomers via radical–radical coupling. In the process, some photodegradation may also take place. In the present work, a high vinyl (~50%) styrene–butadiene–styrene (SBS) block copolymer which is a thermoplastic elastomer was used as the base polymer. An attempt was made to see the effect of ultraviolet radiation on the mechanical properties of the block copolymer. The process variables were time of exposure and photoinitiator concentration. Mechanical properties like tensile strength, elongation at break, modulus at different elongations and hardness of the irradiated samples were studied and compared with those of unirradiated ones. In this S-B-S block copolymer, a relatively low exposure time and low photoinitiator concentration were effective in obtaining optimized mechanical properties. Infrared spectroscopy, contact angle and scanning electron microscopy were used to characterize the results obtained from mechanical measurements.
    Electronic ISSN: 2073-4360
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
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  • 9
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    Analytical Solution for Static and Dynamic Analysis of Graphene-Based Hybrid Flexoelectric Nanostructures (2021)
    Molecular Diversity Preservation International
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    Publication Date: 2021-03-06
    Description: Owing to their applications in devices such as in electromechanical sensors, actuators and nanogenerators, the consideration of size-dependent properties in the electromechanical response of composites is of great importance. In this study, a closed-form solution based on the linear piezoelectricity, Kirchhoff’s plate theory and Navier’s solution was developed, to envisage the electromechanical behaviors of hybrid graphene-reinforced piezoelectric composite (GRPC) plates, considering the flexoelectric effect. The governing equations and respective boundary conditions were obtained, using Hamilton’s variational principle for achieving static deflection and resonant frequency. Moreover, the different parameters considering aspect ratio, thickness of plate, different loadings (inline, point, uniformly distributed load (UDL), uniformly varying load (UVL)), the combination of different volume fraction of graphene and piezoelectric lead zirconate titanate are considered to attain the desired bending deflection and frequency response of GRPC. Different mode shapes and flexoelectric coefficients are also considered and the results reveal that the proper addition of graphene percentage and flexoelectric effect on the static and dynamic responses of GRPC plate is substantial. The obtained results expose that the flexoelectric effect on the piezoelastic response of the bending of nanocomposite plates are worth paying attention to, in order to develop a nanoelectromechanical system (NEMS). Our fundamental study sheds the possibility of evolving lightweight and high-performance NEMS applications over the existing piezoelectric materials.
    Electronic ISSN: 2504-477X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 10
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    A Reusable Efficient Green Catalyst of 2D Cu-MOF for the Click and Knoevenagel Reaction (2021)
    Molecular Diversity Preservation International
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    Publication Date: 2021-08-31
    Description: [Cu(CPA)(BDC)]n (CPA = 4-(Chloro-phenyl)-pyridin-4-ylmethylene-amine; BDC = 1,4-benzenedicarboxylate) has been synthesized and structurally characterized by single crystal X-Ray diffraction measurement. The structural studies establish the copper (II) containing 2D sheet with (4,4) square grid structure. The square grid lengths are 10.775 and 10.769 Å. Thermal stability is assessed by TGA, and subsequent PXRD data establish the crystallinity. The surface morphology is evaluated by FE-SEM. The N2 adsorption−desorption analysis demonstrates the mesoporous feature (∼6.95 nm) of the Cu-MOF. This porous grid serves as heterogeneous green catalyst with superficial recyclability and thermal stability and facilitates organic transformations efficiently such as, Click and Knoevenagel reactions in the aqueous methanolic medium.
    Electronic ISSN: 1420-3049
    Topics: Chemistry and Pharmacology
    Published by Molecular Diversity Preservation International
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