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Recently it has become both possible and practical to perform MR at magnetic fields from µT to mT, the so-called ultra-low field (ULF) regime. SQUID sensor technology allows for ultra-sensitive detection while pulsed pre-polarizing fields greatly enhance signal. The instrumentation allows for unprecedented flexibility in signal acquisition sequences and simplified MRI instrumentation. Here we present the results for a new application of ULF MRI and relaxometry for the detection and characterization of liquids. We briefly describe the motivation and advantages of the ULF MR approach. We then present recent results from a 7channel ULF MRI/relaxometer system constructed to non-invasively inspect liquids at a security checkpoint for the presence of hazardous material. The instrument was fielded to the Albuquerque International Airport in December, 2008, and results from that endeavor are also presented.

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A major source of noise complaints in open-plan offices has consistently been co-workers talking nearby or talking on the phone. Various masking sounds such as white noise and pink noise have been explored to reduce the intelligibility level of speech from adjacent co-workers in open-plan offices. Recently, nature soundscapes such as water, rainfall or birdsong have been introduced instead of conventional white or pink noises. Water sounds with limited acoustic variation have shown more effectiveness than nature sounds with high acoustic variation such as birdsong. This study examined four types of background sounds in a controlled lab environment that simulated a typical open-plan office in a large pharmaceutical company in the United Kingdom. The purpose was to understand cognitive performance, satisfaction and preference, and physiological responses among the four types of background sounds: no external acoustic noise, typical daily office noise, white noise and spring water sound. The study employed three methods: an assessment of cognitive performance to measure memory, distractibility and decision-making; a survey to understand subjective satisfaction and preference; and use of wearable devices to monitor physiological responses. Two different types of wearable devices were used: pulse oximeter and electrodermal activity sensor to compare physiological responses to the four types of sounds. This article discusses discrepancies found between participants’ satisfaction/preference and their cognitive performance under the four background sounds and potential future implications of masking sounds in open-plan offices.

Nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) are ubiquitous tools in science and medicine. NMR provides powerful probes of local and macromolecular chemical structure and dynamics. Recently it has become possible and practical to perform MR at very low fields (from 1 μT to 1 mT), the so-called ultra-low field (ULF) regime. Pulsed pre-polarizing fields greatly enhance the signal strength and allow flexibility in signal acquisition sequences. Improvements in SQUID sensor technology allow ultra-sensitive detection in a pulsed field environment. In this regime the proton Larmor frequencies (1 Hz – 100 kHz) of ULF MR overlap (on a time scale of 10 μs to 100 ms) with “slow” molecular dynamic processes such as diffusion, intra-molecular motion, chemical reactions, and biological processes such as protein folding, catalysis and ligand binding. The frequency dependence of relaxation at ultra-low fields may provide a probe for biomolecular dynamics on the millisecond timescale (protein folding and aggregation, conformational motions of enzymes, binding and structural fluctuations of coupled domains in allosteric mechanisms) relevant to host-pathogen interactions, biofuels, and biomediation. Also this resonance-enhanced coupling at ULF can greatly enhance contrast in medical applications of ULF-MRI resulting in better diagnostic techniques. We have developed a number of instruments and techniques to study relaxation vs. frequency at the ULF regime. Details of the techniques and results are presented. Ultra-low field methods are already being applied at LANL in brain imaging, and detection of liquid explosives at airports. However, the potential power of ultra-low field MR remains to be fully exploited.