Rotating curved spacetime signatures from a giant quantum vortex.

Gravity simulators are laboratory systems in which small excitations such as sound or surface waves behave as fields propagating on a curved spacetime geometry. The analogy between gravity and fluids requires vanishing viscosity, a feature naturally realized in superfluids such as liquid helium or cold atomic clouds. Such systems have been successful in verifying key predictions of quantum field theory in curved spacetime.

Radical-induced hetero-nuclear mixing and low-field C relaxation in solid pyruvic acid.

Radicals serve as a source of polarization in dynamic nuclear polarization, but may also act as polarization sink, in particular at low field. Additionally, if the couplings between the electron spins and different nuclear reservoirs are stronger than any of the reservoirs' couplings to the lattice, radicals can mediate hetero-nuclear polarization transfer. Here, we report radical-enhanced C relaxation in pyruvic acid doped with trityl.

Radical-Induced Low-Field H Relaxation in Solid Pyruvic Acid Doped with Trityl-OX063.

In dynamic nuclear polarization (DNP), radicals such as trityl provide a source for high nuclear spin polarization. Conversely, during the low-field transfer of hyperpolarized solids, the radicals' dipolar or Non-Zeeman reservoir may act as a powerful nuclear polarization sink. Here, we report the low-temperature proton spin relaxation in pyruvic acid doped with trityl, for fields from 5 mT to 2 T.

The Crystal Structure of BaNbO Revisited: A Neutron Diffraction and Solid-State NMR Study.

The structure of BaNbO has been investigated using high resolution neutron powder diffraction. Our results show that, while the structure has some features in common with the 9R perovskite and palmierite structures, it is a new and distinct structure. It is shown to follow a (chh)(hhc)(chh) sequence with BaO packing layers and is a cation- and anion-deficient 9H perovskite polytype.

The role of the chemical composition of monetite on the synthesis and properties of α-tricalcium phosphate.

There has been a resurgence of interest in alpha-tricalcium phosphate (α-TCP), with use in cements, polymer composites and in bi- and tri-phasic calcium phosphate bone grafts. The simplest and most established method for preparing α-TCP is the solid state reaction of monetite (CaHPO4) and calcium carbonate at high temperatures, followed by quenching. In this study, the effect of the chemical composition of reagents used in the synthesis of α-TCP on the local structure of the final product is reported and findings previously reported pertaining to the phase composition and stability are also corroborated.

A spectrometer designed for 6.7 and 14.1 T DNP-enhanced solid-state MAS NMR using quasi-optical microwave transmission.

A Dynamic Nuclear Polarisation (DNP) enhanced solid-state Magic Angle Spinning (MAS) NMR spectrometer operating at 6.7 T is described and demonstrated. The 187 GHz TE(13) fundamental mode of the FU CW VII gyrotron is used as the microwave source for this magnetic field strength and 284 MHz (1)H DNP-NMR.