Purpose To compare measurement of the liver iron concentration in patients with transfusional iron overload by magnetic resonance imaging (MRI), using R2*, and by magnetic susceptometry, using a new high-transitiontemperature (high-Tc; operating at 77 K, cooled by liquid nitrogen) superconducting magnetic susceptometer. Methods In 28 patients with transfusional iron overload, 43 measurements of the liver iron concentration were made by both R2* and high-Tc magnetic susceptometry. Results Measurements of the liver iron concentration by R2* and high-Tc magnetic susceptometry were significantly correlated when comparing all patients (Pearson's r = 0.91, p < 0.0001) and those with results by susceptometry >7 mg Fe/g liver, dry weight (r = 0.93, p = 0.006). In lower ranges of liver iron, no significant correlations between the two methods were found (0 to <3.2 mg Fe/g liver, dry weight: r = 0.2, p = 0.37; 3.2 to 7 mg Fe/g liver, dry weight: r = 0.41; p = 0.14). Conclusion The lack of linear correlation between R2* and magnetic susceptibility measurements of the liver iron concentration with minimal or modest iron overload may be due to the effects of fibrosis and other cellular pathology that interfere with R2* but do not appreciably alter magnetic susceptibility.

AbstractThe FeCl3‐catalyzed reaction of alkynes with NBS or NIS in methanol provides α,α‐dihalodimethyl ketals in excellent yields.

Aromatic and aliphatic alkynes can be halo-functionalized to α,α-dihalodimethyl ketals catalyzed by FeCl3 in excellent yields. MeOH is used as a nucleophilic solvent and N-halosuccinimide as the halogen source for this efficient transformation. The resulting α,α-dibromodimethyl ketals can be converted to the corresponding α,α-dibromoketones by treatment with 8% FeCl3 in silica gel.

Using the combination of DFT-based computational approaches and experimental measurements, we have studied the crystal structure, phase stability, and decomposition products of mixed Mg(NH2)(2)/Mg(BH4)(2) materials. We find the following: (i) DFT crystal structure prediction calculations (0 K) show the existence of a mixed Mg(NH2)(2)/Mg(BH4)(2) phase, which is thermodynamically stable relative to its separated phases [Mg(NH2)(2) and Mg(BH4)(2)]. (ii) The DFT calculated phonon density of states of Mg(NH2)(BH4) is in good agreement with the peak positions from experimental PAS IR measurements (at the room temperature) of a ball-milled Mg(NH2)(2)/Mg(BH4)(2) mixture, suggesting the mixture is not merely a physical mixture of the individual compounds. (iii) The experimentally measured dehydrogenation temperature of the mixed Mg(NH2)(2)/Mg(BH4)(2) phase is lower than that of Mg(NH2)(2) or Mg(BH4)(2), which further confirms that it is not a simply physical mixture of Mg(NH2)(2) and Mg(BH4)(2). The observed amount of H-2 release is 3.4 wt % at 250 degrees and 8.3 wt % above 280 degrees. (iv) From a combination of DFT, the grand-canonical linear programming (GCLP) method calculations, and PAS IR measurements of dehydrogenated samples, we identify the existence of the B H bonds and linear N-B-N units in the decomposition of Mg(NH2)(2)/Mg(BH4)(2). (v) Experimental desorption measurements reveal that the Mg(NH2)(2)/Mg(BH4)(2) mixed phase is irreversible, consistent with DFT calculated enthalpies in the range of -18 to +16 kJ(mol H-2), too low for near-ambient reversible storage.

We have employed density functional theory calculations to determine the formation energy for a number of neutral and charged point defects in the mixed anion hydrogen storage compound Li4BN3H10, under a variety of chemical potentials, to investigate the possible role of point defects in hydrogen desorption. We discuss the determination of chemical potentials based on four-phase equilibria that arise from the temperature-dependent decomposition reactions. Our results indicate the following: (1) Neutral NH vacancies are nearly always the lowest-energy defect and have a small positive formation energy up to the experimental hydrogen desorption temperature. (2) The cases where NH vacancies are not the lowest energy correspond to unstable four-phase equilibria. (3) Separated pairs of oppositely charged defects are always higher energy than the analogous combined neutral defect.

We have used density functional theory based ab initio molecular dynamics (AIMD) to study NaAlH${}_{4}$, LiBH${}_{4}$, LiNH${}_{2}$, and Li${}_{2}$BNH${}_{6}$ across a range of temperatures, above and below the experimental melting temperature. We have elucidated the structure, vibrational, and diffusion characteristics of these four materials. We find: (i) In all cases, the liquid state remains a mixture of the ions found in the solid state. (ii) The anions remain intact on average but undergo large deformations across the range of temperatures. (iii) In the case of LiNH${}_{2}$, there is evidence that the Li${}^{+}$ sublattice melts before the anionic sublattice. (iv) We find a connection between increased anion-anion ordering and reduced anion mobility even above the experimental melting point, due to long range Coulombic interactions between anions. (v) Finally, we find the liquid has the same major vibrational modes as the solid, though the lower frequency vibration and rotation modes become more prominent with increasing temperature.

Magnetization and Mössbauer spectroscopy results on aerosol processed YBa2 (Cu1-xFex)307–δ samples are presented. Systematics of Tc(x), x(x) and Fe dopant site occupancies In/I(x) as a function of dopant concentration ‘x’ are deduced and compared to those established on analogous solid-state- reacted samples. The absence of twinning in the aerosol processed grains leads to a random replacement of Cu for Fe in chains and planes of the host structure.

Magnetic particle imaging (MPI) is a new tomographic method [1] based on the nonlinear response of superparamagnetic iron oxide (SPIO) nanoparticles. It has promise for fast imaging with certain advantages in resolution, sensitivity, contrast, and cost. A static but spatially inhomogeneous field (selection field) and homogeneous oscillating field (drive field) are applied for spatial encoding. The selection field has a very strong gradient in order to saturate the nanoparticle domains outside the field-free-point (FFP). The oscillating drive fields can move the FFP around the whole field of view by using different driving frequencies in different directions. Only the FFP region yields a detectable signal. The average magnetization has been assumed to respond immediately to changes in the applied field [1-8]. However, delays due to magnetization relaxation lead to limitations on the response time and it is the purpose of the present paper to augment previous simulations [2, 3] by taking into account relaxation time effects.

Introduction: Magnetic particle imaging (MPI) is a new tomographic method [1] based on the nonlinear response of super-paramagnetic iron oxide (SPIO) nanoparticles. It has promise for fast imaging in the submillimeter range with some advantages in sensitivity, contrast, and cost in comparison with MRI. A static but spatially inhomogeneous field (selection field) and homogeneous oscillating field (drive field) are applied for spatial encoding. The selection field has a very strong gradient in order to saturate nanoparticle domains outside the field-free-point (FFP). The oscillating drive fields can move the FFP around the whole field of view by using different driving frequencies in different directions. The FFP region yields the detectable signal. The average magnetization has been assumed to respond immediately to changes in the applied field. However, delays due to magnetization relaxation lead to limitations on the response time and it is the purpose of the present paper to augment previous simulations [2, 3] by taking into account relaxation time effects.

We have applied density-functional theory based ab initio molecular dynamics to examine Li4BN3H10 at temperatures both above and below the experimental melting point. We examine the structure of the liquid, diffusivity, vibrational spectra and compare to both experimental data and analogous properties from solid-state calculations. We find the following: (1) the liquid state, like the solid state, is primarily a mixture of Li+, BH4-, and NH2- with ionic interactions between the BH4- and NH2- anions and the Li+ cations. (2) We observe the reaction of two amide anions exchanging hydrogen to form ammonia and an imide anion: 2NH(2)(-)-> NH3+NH2-. (3) The liquid demonstrates wide bond-angle distributions in the BH4- and NH2- units and thus these anionic units are not simply rigid complexes. (4) The Li+ sublattice disorders before the anionic sublattices and the liquid exhibits very fast Li+ diffusion. We calculate the activation energy and pre-exponential factor for Li+ diffusivity in the liquid to be similar to 20 kJ/mol and 15x10(-4) cm(2)/s, respectively. (5) Finally, we find that the liquid contains the same generic types of vibrational modes as the solid, however the lower-frequency anionic vibration and rotation modes become more prominent with increasing temperature.

We present a molecular dynamics study of the influence of temperature on defect generation and evolution in irradiated cubic silicon carbide. We simulated 10keV displacement cascades, with an emphasis on the quantification of the spatial distribution of defects, at six different temperatures from 0K to 2000K under identical primary knock-on atom conditions. By post-processing the simulation results we analyzed the temporal evolution of vacancies, interstitials, and antisite defects, the spatial distribution of vacancies, and the distribution of vacancy cluster sizes. The majority of vacancies were found to be isolated at all temperatures. We found evidence of temperature dependence in C and Si replacements and CSi antisite formation, as well as reduced damage generation behavior due to enhanced defect relaxation at 2000K.

We employ passive flow control using two-dimensional hydrofoils to reduce vortex-induced vibrations (VIV) and drag on a cylinder of circular cross-section. We test the hypothesis that by using foils to bend the streamlines around the cylinder, and hence forcing the flow to approach potential flow-like patterns VIV and drag will be reduced. A systematic parametric search, first using groups of two and then four foils, shows that it is possible to completely eliminate vibrations and reduce the drag coefficient to about Cd=0.50 at sub-critical Reynolds numbers. This parametric search is conducted in conjunction with force measurement and particle image velocimetry on a fixed towed cylinder. The effectiveness of the foils in regards to VIV was further tested with an apparatus allowing free transverse vibrations of a towed cylinder.

All existing superconducting instrumentation for measuring the concentration of iron stored in the human liver requires liquid helium for its operation. We report the mathematical modeling, optimization, and instrumental performance of an instrument that uses high-transition-temperature (high-Tc) superconductors. Requiring only liquid nitrogen to operate, the susceptometer represents the first medical application of the phenomenon of high-temperature superconductivity with the potential for widespread clinical utility.

We describe a new approach to the magnetic measurement of liver iron stores, using an instrument that incorporates a combination of permanent magnets and superconducting flux transformers. Instead of traditional low-transition-temperature superconductor (LTS) transformers, the susceptometer employs their high-transition-temperature (HTS) counterparts. This innovation substantially reduces the size and weight of the instrument, allowing the whole assembly to be scanned in a horizontal plane. We report engineering details of the HTS flux transformers, magnet assembly, field sensing, and scan mechanism, and present experimental data to show that scanning susceptometer can determine not only the susceptibility of cylindrical phantom models but also their diameters. We conjecture that further refinements of scanning susceptometer could lead to a form of susceptibility imaging that would enhance the accuracy of measurements of liver iron stores and also lead to new medical applications of the method.