Typical tracking results of tissue displacement waveform of an elderly female human subject.

<p>(a) obtained under 0% MVC level (at rest), (b) 50% MVC level, and (c) 100% MVC level. The corresponding shear moduli for (a) to (c) were 9 kPa, 213 kPa, and 574 kPa. The solid line represents the tissue displacement waveforms detected at the proximal location, and the dashed line at the distal location, with reference to the vibration source.</p

Correlation between the shear modulus values assessed by indentation method and the corresponding values measured by the vibro-ultrasound method.

<p>Correlation between the shear modulus values assessed by indentation method and the corresponding values measured by the vibro-ultrasound method.</p

Diagram of the vibro-ultrasound system for shear wave velocity measurement using two ultrasound scan lines (left) and the position of the ultrasound probe and the vibrator during the experiment on one human subject (right).

<p>The three positions of the vibrator used for the different vibro-beam distance test were also indicated.</p

Comparison of the shear moduli between (a) 15 mm and 20 mm; and (b) 25 mm and 20 mm, revealed that the vibrator-beam distance appeared to affect very little on the measurement result of shear modulus.

<p>Comparison of the shear moduli between (a) 15 mm and 20 mm; and (b) 25 mm and 20 mm, revealed that the vibrator-beam distance appeared to affect very little on the measurement result of shear modulus.</p

The averaged VI shear modulus of ten elderly healthy female subjects and that of ten young healthy female subjects, plotted with the different relative isometric contraction levels (% MVC torque).

<p>The error bar represents the standard deviation among the 10 subjects.</p

Quantum Chemistry Study of Uranium(VI), Neptunium(V), and Plutonium(IV,VI) Complexes with Preorganized Tetradentate Phenanthrolineamide Ligands

The preorganized tetradentate 2,9-diamido-1,10-phenanthroline ligand with hard–soft donors combined in the same molecule has been found to possess high selectivity toward actinides in an acidic aqueous solution. In this work, density functional theory (DFT) coupled with the quasi-relativistic small-core pseudopotential method was used to investigate the structures, bonding nature, and thermodynamic behavior of uranium­(VI), neptunium­(V), and plutonium­(IV,VI) with phenanthrolineamides. Theoretical optimization shows that Et-Tol-DAPhen and Et-Et-DAPhen ligands are both coordinated with actinides in a tetradentate chelating mode through two N donors of the phenanthroline moiety and two O donors of the amide moieties. It is found that [AnO₂L­(NO₃)]^<i>n</i>+ (An = U^VI, Np^V, Pu^VI; <i>n</i> = 0, 1) and PuL­(NO₃)₄ are the main 1:1 complexes. With respect to 1:2 complexes, the reaction [Pu­(H₂O)₉]⁴⁺(aq) + 2L­(org) + 2NO₃^–(aq) → [PuL₂(NO₃)₂]²⁺(org) + 9H₂O­(aq) might be another probable extraction mechanism for Pu^IV. From the viewpoint of energy, the phenanthrolineamides extract actinides in the order of Pu^IV > U^VI > Pu^VI > Np^V, which agrees well with the experimental results. Additionally, all of the thermodynamic reactions are more energetically favorable for the Et-Tol-DAPhen ligand than the Et-Et-DAPhen ligand, indicating that substitution of one ethyl group with one tolyl group can enhance the complexation abilities toward actinide cations (anomalous aryl strengthening)

Density Functional Theory Studies of UO₂²⁺ and NpO₂⁺ Complexes with Carbamoylmethylphosphine Oxide Ligands

The UO₂²⁺ and NpO₂⁺ extraction complexes with <i>n</i>-octyl­(phenyl)-<i>N</i>,<i>N</i>-diisobutylmethylcarbamoyl phosphine oxide (CMPO) and diphenyl-<i>N</i>,<i>N</i>-diisobutylcarbamoyl phosphine oxide (Ph₂CMPO) have been investigated by density functional theory (DFT) in conjunction with relativistic small-core pseudopotentials. For these extraction complexes, especially the complexes of 2:1 (ligand/metal) stoichiometry, UO₂²⁺ and NpO₂⁺ predominantly coordinate with the phosphoric oxygen atoms. The CMPO and Ph₂CMPO ligands have higher selectivity for UO₂²⁺ over NpO₂⁺, and for all of the extraction complexes, the metal–ligand interactions are mainly ionic. In most cases, the complexes with CMPO and Ph₂CMPO ligands have comparable metal–ligand binding energies, that is, the substitution of a phenyl ring for the <i>n</i>-octyl group at the phosphoryl group of CMPO has no obvious influence on the extraction of UO₂²⁺ and NpO₂⁺. Moreover, hydration energies might play an important role in the extractability of CMPO and Ph₂CMPO for these actinyl ions

Complexation Behavior of Eu(III) and Am(III) with CMPO and Ph₂CMPO Ligands: Insights from Density Functional Theory

A series of extraction complexes of Eu­(III) and Am­(III) with CMPO (<i>n</i>-octyl­(phenyl)-<i>N</i>,<i>N</i>-diisobutyl-methylcarbamoyl phosphine oxide) and its derivative Ph₂CMPO (diphenyl-<i>N</i>,<i>N</i>-diisobutyl carbamoyl phosphine oxide) have been studied using density functional theory (DFT). It has been found that for the neutral complexes of 2:1 and 3:1 (ligand/metal) stoichiometry, CMPO and Ph₂CMPO predominantly coordinate with metal cations through the phosphoric oxygen atoms. Eu­(III) and Am­(III) prefer to form the neutral 2:1 and 3:1 type complexes in nitrate-rich acid solutions, and in the extraction process the reactions of [M­(NO₃)­(H₂O)₇]²⁺ + 2NO₃^– + <i>n</i>L → ML_<i>n</i>(NO₃)₃ + 7H₂O (M = Eu, Am; <i>n</i> = 2, 3) are the dominant complexation reactions. In addition, CMPO and Ph₂CMPO show similar extractability properties. Taking into account the solvation effects, the metal–ligand binding energies are obviously decreased, i.e., the presence of solvent may have an significant effect on the extraction behavior of Eu­(III) and Am­(III) with CMPOs. Moreover, these CMPOs reagents have comparable extractability for Eu­(III) and Am­(III), confirming that these extractants have little lanthanide/actinide selectivity in acidic media

Theoretical Insights into the Substitution Effect of Phenanthroline Derivatives on Am(III)/Eu(III) Separation

Separation of trivalent actinides (An(III)) and lanthanides (Ln(III)) poses a huge challenge in the reprocessing of spent nuclear fuel due to their similar chemical properties. N,N′-Diethyl-N,N′-ditolyl-2,9-diamide-1,10-phenanthroline (Et-Tol-DAPhen) is a potential ligand for the extraction of An(III) from Ln(III), while there are still few reports on the effect of its substituent including electron-withdrawing and electron-donating groups on An(III)/Ln(III) separation. Herein, the interaction of Et-Tol-DAPhen ligands modified by the electron-withdrawing groups (CF3, Br) and electron-donating groups (OH) with Am(III)/Eu(III) ions was investigated using scalar relativistic density functional theory (DFT). The analyses of bond order, quantum theory of atoms in molecules (QTAIM), and molecular orbital (MO) indicate that the substitution groups have a slight effect on the electronic structures of the [M(L-X)(NO3)3] (X = CF3, Br, OH) complexes. However, the thermodynamic results suggest that a ligand with the electron-donating group (L-OH) improves the extraction ability of metal ions, and the ligand modified by the electron-withdrawing group (L-Br) has the best Am(III)/Eu(III) selectivity. This work could render new insights into understanding the effect of electron-withdrawing and electron-donating groups in tuning the selectivity of Et-Tol-DAPhen derivatives and pave the way for designing new ligands modified by substituted groups with better extraction ability and An(III)/Ln(III) selectivity

Theoretical Insights on the Interaction of Uranium with Amidoxime and Carboxyl Groups

Recovery of uranium from seawater is extremely challenging but important for the persistent development of nuclear energy, and thus exploring the coordination structures and bonding nature of uranyl complexes becomes essential for designing highly efficient uranium adsorbents. In this work, the interactions of uranium and a series of adsorbents with various well-known functional groups including amidoximate (AO^–), carboxyl (Ac^–), glutarimidedioximate (HA^–), and bifunctional AO^–/Ac^–, HA^–/Ac^– on different alkyl chains (R′CH₃, R″C₁₃H₂₆) were systematically studied by quantum chemical calculations. For all the uranyl complexes, the monodentate and η² coordination are the main binding modes for the AO^– groups, while Ac^– groups act as monodentate and bidentate ligands. Amidoximes can also form cyclic imide dioximes (H₂A), which coordinate to UO₂²⁺ as tridentate ligands. Kinetic analysis of the model displacement reaction confirms the rate-determining step in the extraction process, that is, the complexing of uranyl by amidoxime group coupled with the dissociation of the carbonate group from the uranyl tricarbonate complex [UO₂(CO₃)₃]^4–. Complexing species with AO^– groups show higher binding energies than the analogues with Ac^– groups. However, the obtained uranyl complexes with Ac^– seem to be more favorable according to reactions with [UO₂(CO₃)₃]^4– as reactant, which may be due to the higher stability of HAO compared to HAc. This is also the reason that species with mixed functional group AO^–/Ac^– are more stable than those with monoligand. Thus, as reported in the literature, the adsorbability of uranium can be improved by the synergistic effects of amidoxime and carboxyl groups