Capillary electrophoresis for the characterization of the complex dendrimeric contrast agent Gadomer

A CE method for the characterization of the complex dendrimeric contrast agent Gadomer has been developed and validated. The method was capable of separating the target substance Gadomer 24 from related dendrimers containing amino or carboxyl functions and from impurities of lower molecular weight. The compounds were separated in a fused-silica capillary. The optimized BGE consisted of 15 mM sodium phosphate, pH 6.3, containing 0.5 mM hexadecyltrimethylammonium bromide. The assay was validated with regard to linearity, specificity, accuracy, LOD and LOQ as well as robustness according to the guidelines of the International Conference on Harmonization. The method allows the determination of the purity and stability of the drug substance Gadomer as well as its injectable formulation. On the basis of the present study, a strategy for the quality assurance and quality control of the complex dendrimeric drug candidate Gadomer may be devised. The method may therefore serve as a key component in a set of analytical methodologies designed to assure and control the reproducible quality and safety of this innovative product. To the best of our knowledge, this is the first work reporting a validated method for the characterization, impurity profiling, and stability testing of a dendrimeric agent designed for clinical use.     

Half-magnetization plateau stabilized by structural distortion in the antiferromagnetic heisenberg model on a pyrochlore lattice

Magnetization plateaus, visible as anomalies in magnetic susceptibility at low temperatures, are one of the hallmarks of frustrated magnetism. We show how an extremely robust half-magnetization plateau can arise from coupling between spin and lattice degrees of freedom in a pyrochlore antiferromagnet and develop a detailed symmetry of analysis of the simplest possible scenario for such a plateau state. The application of this theory to the spinel oxides CdCr2O4 and HgCr2O4, where a robust half-magnetization plateau has been observed, is discussed.     

Ising phases of Heisenberg ladders in a magnetic field

We show that Dzyaloshinskii-Moriya (DM) interactions can substantially modify the phase diagram of spin-1/2 Heisenberg ladders in a magnetic field provided they compete with exchange. For nonfrustrated ladders, they induce a local magnetization along the DM vector that turns the gapless intermediate phase into an Ising phase with broken translational symmetry, while for frustrated ladders, they extend the Ising order of the half-integer plateau to the surrounding gapless phases of the purely Heisenberg case. Implications for experimental ladder and dimer systems are discussed.     

Frustrated magnetic structure of TmAgGe

Physical properties of the compound TmAgGe have been investigated by means of magnetometric, transport, calorimetric as well as neutron diffraction measurements. The compound crystallizes in the hexagonal ZrNiAl-type crystal structure. The reported results indicate that the sample exhibits an antiferromagnetic ordering below . The low temperature behavior of the magnetic susceptibility and the specific heat is in good agreement with the spin-wave theory with linear dispersion relation. In addition, the magnetic structure of TmAgGe was determined by means of neutron diffraction measurements. The Tm moments are equal to 6.44(10) μ_B at 1.5 K and form a non-collinear magnetic structure within the basal plane. To describe this structure three different propagation vectors: , and are required. Such a spin arrangement is analyzed on the basis of group theory.     

Magnetic properties of NdAu2Ge2

Physical properties of NdAu₂Ge₂, crystallising with the tetragonal ThCr₂Si₂-type crystal structure, were investigated by means of magnetic, calorimetric and electrical transport measurements as well as by neutron diffraction. The compound exhibits antiferromagnetic ordering below T_N=4.5 K with a collinear magnetic structure of the AFI-type. The neodymium magnetic moments are parallel to the c-axis and amount to 1.04(4) μ_B at 1.5 K. The observed magnetic behaviour is strongly influenced by crystalline electric field effect.     

Three-sublattice ordering of the SU(3) Heisenberg model of three-flavor fermions on the square and cubic lattices

Combining a semiclassical analysis with exact diagonalizations, we show that the ground state of the SU(3) Heisenberg model on the square lattice develops three-sublattice long-range order. This surprising pattern for a bipartite lattice with only nearest-neighbor interactions is shown to be the consequence of a subtle quantum order-by-disorder mechanism. By contrast, thermal fluctuations favor two-sublattice configurations via entropic selection. These results are shown to extend to the cubic lattice, and experimental implications for the Mott-insulating states of three-flavor fermionic atoms in optical lattices are discussed.     

Spectral function and self-energy of the one-dimensional Hubbard model in the U →∞ limit

The interpretation of the k dependent spectral functions of the one-dimensional, infinite U Hubbard model obtained by using the factorized wave-function of Ogata and Shiba is revisited. The well defined feature which appears in addition to low energy features typical of Luttinger liquids, and which, close to the Fermi energy, can be interpreted as the shadow band resulting from 2k _F spin fluctuations, is further investigated. A calculation of the self-energy shows that, not too close to the Fermi energy, this feature corresponds to a band, i.e. to a solution of the Dyson equation ω-ε(k)-ReΣ(k,ω) = 0.