NRNF28 - Nonuniform elastic properties of macromolecules and effect of prestrain on their continuum nature
Physical Review E
We present the results for a mutant of Sesbania mosaic virus capsid, where we calculate the elastic moduli at different scales and observe an apparent problem with the chosen reference configuration in some cases. We present a possible explanation using an elastic network model, where inducing random prestrain results in a similar behavior. This phenomenon provides a novel insight into the continuum nature of macromolecules and defines the limits on details that the elasticity theory can capture. Further investigation into prestrains could elucidate important aspects of conformational dynamics of macromolecules.
NRN150 - Copper-complexed isonicotinic acid functionalized aluminium oxide nanoparticles
Main Group Chemistry
The functionalization of two different alumina morphologies (thin film and nanoparticle) with carboxylic acids is reported. Advancing contact angle measurements show that isonicotinic acid functionalization of a native aluminium oxide surface result in an increase in hydrophilicity. Isonicotinic acid and nicotinic acid functionalised alumina nanoparticles (i NA-NP and NA-NP, respectively) have been characterized by Fourier transform infrared-attenuated total reflectance spectroscopy (FTIR-ATR), thermo gravimetric analysis-infrared spectroscopy (TGA-IR), electron dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). The surface grafting density for i NA-NP and NA-NP is determined to be 5.4 and 15.6 molecules/nm2 , respectively. The reaction of i NA-NP with copper(II) acetate has been studied and the stability of the resulting complex species (CuA-i NA-NP) have been determined as a function of pH. UV-visible-near IR absorption spectroscopy indicates uptake of copper acetate from solution, and X-ray photoelectron spectroscopy (XPS) shows a small shift in the nanoparticle N 1 s binding energy after complex formation with copper(II) acetate.
NRN150 - Enhanced purification of carbon nanotubes by microwaves and chlorine cleaning procedures
A new two-step purification method of carbon nanotubes (CNTs) involving a microwave treatment followed by a gas-phase chlorination process is reported. The significant advantage of this method over conventional cleaning carbon nanotubes procedures is that under microwave treatment in air, the carbon shells that encase the residual metal catalyst particles are removed and the metallic iron is exposed and subsequently oxidized making it accessible for chemical removal. The products from microwave and chlorine treatment have been characterized by TG/DTA, SEM, TEM, EDX, XPS, and Raman spectroscopy. The oxidation state of the iron residue is observed to change from Fe(0) to Fe(II)/Fe(III) after microwave treatment and atmospheric exposure. The effects of the duration and number of microwave exposures has been investigated. This rapid and effective microwave step favours the subsequent chlorination treatment enabling a more effective cleaning procedure to take place, yielding higher purity single- and multi-walled CNTs.
NRN140 - In situ synchrotron study of ordered and disordered LiMn1.5Ni0.5O4 as lithium ion battery positive electrode
In situ powder synchrotron diffraction and X-ray absorption spectroscopy have been used to investigate cation ordered as well as disordered modifications of the LiMn1.5Ni0.5O4 spinel-type compound as a Li-ion battery (LIB) cathode during electrochemical cycling. The structural state depends on the adopted heat treatment conditions and is ascertained by Raman and neutron diffraction data. The degree of Mn-Ni ordering (none, partial, complete) is one parameter that influences the electrochemical behaviour. The in situ data reveal significant differences in behaviour with respect to structural phase transitions during electrochemical cycling. Ordered Li2Mn3NiO8 (P4332) undergoes two consecutive first order structural phase transitions between spinel type phases during charging - discharging. These are most probably connected with steps in oxidation state for the Ni-atoms as supported by XANES data. The disordered phases (Fd-3m) show a mixed “solid solution - two phase” behaviour accompanied by a smooth decrease in the unit cell volume during charging over the two redox steps involved, Ni2+/Ni3+/Ni4+, however, also with volume jumps at first order transitions. This combined behaviour is explained for the first time for spinel type LiMn1.5Ni0.5O4 materials. It is not clear why ordered and disordered phases show different phase behaviors depending on the state of (dis)charge. This could be due to higher valent Mn taking part in the redox activity at higher voltages, however, future verification is required.
NRNF28 - An inverse modeling approach for semilunar heart valve leaflet mechanics: exploitation of tissue structure
Biomechanics and Modeling in Mechanobiology
Determining the biomechanical behavior of heart valve leaflet tissues in a noninvasive manner remains an important clinical goal. While advances in 3D imaging modalities have made in vivo valve geometric data available, optimal methods to exploit such information in order to obtain functional information remain to be established. Herein we present and evaluate a novel leaflet shape-based framework to estimate the biomechanical behavior of heart valves from surface deformations by exploiting tissue structure.
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