We demonstrate a spin-based, all-dielectric electrometer based on an ensemble of nitrogen-vacancy (NV − ) defects in diamond. An applied electric field causes energy-level shifts symmetrically away from the NV − 's degenerate triplet states via the Stark effect; this symmetry provides immunity to temperature fluctuations allowing for shot-noise-limited detection. Using an ensemble of NV − s, we demonstrate shot-noise-limited sensitivities approaching 1 (V/cm)/ √ Hz under ambient conditions, at low frequencies (<10 Hz), and over a large dynamic range (20 dB). A theoretical model for the ensemble of NV − s fits well with measurements of the ground-state electric susceptibility parameter k ⊥ . Implications of spin-based, dielectric sensors for micron-scale electric-field sensing are discussed.

We demonstrate a robust, scale-factor-free vector magnetometer, which uses a closed-loop frequency-locking scheme to simultaneously track Zeeman-split resonance pairs of nitrogen-vacancy (NV) centers in diamond. Compared with open-loop methodologies, this technique is robust against fluctuations in temperature, resonance linewidth, and contrast; offers a three-order-of-magnitude increase in dynamic range; and allows for simultaneous interrogation of multiple transition frequencies.By directly detecting the resonance frequencies of NV centers aligned along each of the diamond's four tetrahedral crystallographic axes, we perform full vector reconstruction of an applied magnetic field. * These authors contributed equally to this work. †

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Computed tomography scan and positron emission tomography scan are both diagnostic tests useful in the evaluation of metastatic colorectal cancer. However, positron emission tomography scanning is more sensitive than computed tomography scanning and more likely to give the correct result when actual metastatic disease is present.

Image processing tools combining thresholding, expansion, and convolution were the most useful for stool subtraction. Laxative-free colon examinations using barium for stool labeling can be performed at CT colonography with or without stool subtraction with high accuracy. Further study is warranted.