NPK NMR Sensor: Online Monitoring of Nitrogen, Phosphorus, and Potassium in Animal Slurry.

Knowledge of the actual content of nitrogen, phosphorus, and potassium (NPK) in animal slurry is highly important to optimize crop production and avoid environmental pollution when slurry is spread on agricultural fields. Here, we present a mobile, low-field nuclear magnetic resonance (NMR) sensor suitable for online monitoring of the NPK content in animal slurry as an alternative to crude estimates or tedious nonspecific, off-site laboratory analysis. The sensor is based on (14)N, (17)O, (31)P, and (39)K NMR in a digital NMR instrument equipped with a 1.

Natural abundant (17) O NMR in a 1.5-T Halbach magnet.

We present mobile, low-field (17) O NMR as a means for monitoring oxygen in liquids. Whereas oxygen is one of the most important elements, oxygen NMR is limited by a poor sensitivity related to low natural abundance and gyro-magnetic ratio of the NMR active (17) O isotope. Here, we demonstrate (17) O NMR detection at a Larmor frequency of 8.

NMR sensor for onboard ship detection of catalytic fines in marine fuel oils.

A mobile, low-field nuclear magnetic resonance (NMR) sensor for onboard, inline detection of catalytic fines in fuel oil in the shipping industry is presented as an alternative to onshore laboratory measurements. Catalytic fines (called cat fines) are aluminosilicate zeolite catalysts utilized in the oil cracking process at refineries. When present in fuel oil, cat fines cause abrasive wear of engine parts and may ultimately lead to engine breakdown with large economical consequences, thereby motivating methods for inline measurements.

Superconductivity in a molecular metal cluster compound.

Compelling evidence for band-type conductivity and even bulk superconductivity below Tc approximately 8 K has been found in (69,71)Ga NMR experiments in crystalline ordered, giant Ga84 cluster compounds. This material appears to represent the first realization of a theoretical model proposed by Friedel in 1992 for superconductivity in ordered arrays of weakly coupled, identical metal nanoparticles.

Nuclear spin dynamics in the quantum regime of a single-molecule magnet.

We show that the nuclear spin dynamics in the single-molecule magnet Mn12-ac below 1 K is governed by quantum tunneling fluctuations of the cluster spins, combined with intercluster nuclear spin diffusion. We also obtain the first experimental proof that-surprisingly-even deep in the quantum regime the nuclear spins remain in good thermal contact with the lattice phonons. We propose a simple model for how T-independent tunneling fluctuations can relax the nuclear polarization to the lattice that may serve as a framework for more sophisticated theories.

NMR evidence for a two-step phase separation in Nd1.85Ce0.15CuO4-delta.

By Cu NMR we studied the spin and charge structure in Nd(2-x)Ce(x)CuO(4-delta). For x=0.15, starting from a superconducting sample, the low temperature magnetic order in the sample reoxygenated under 1 bar oxygen at 900 degrees C reveals a peculiar modulation of the internal field, indicative of a phase characterized by large charge droplets ("blob" phase).

63Cu NMR evidence for enhanced antiferromagnetic correlations around Zn impurities in YBa2Cu3O6.7.

Doping the high- T(c) superconductor YBa2Cu3O6.7 with 1.5% of nonmagnetic Zn impurities in CuO2 planes is shown to produce a considerable broadening of 63Cu NMR spectra, as well as an increase of low-energy magnetic fluctuations detected in 63Cu spin-lattice relaxation measurements.