GPU-accelerated parallel image reconstruction strategies for magnetic particle imaging.

. Image reconstruction is a fundamental step in magnetic particle imaging (MPI). One of the main challenges is the fact that the reconstructions are computationally intensive and time-consuming, so choosing an algorithm presents a compromise between accuracy and execution time, which depends on the application.

Harmonic dependence of thermal magnetic particle imaging.

Advances in instrumentation and tracer materials are still required to enable sensitive, accurate, and localized in situ 3D temperature monitoring by magnetic particle imaging (MPI). We have developed a high-resolution magnetic particle imaging instrument and implemented a low-noise multi-harmonic lock-in detection method to observe and quantify temperature variations in iron oxide nanoparticle tracers using the harmonic ratio method for determining temperature. Using isolated harmonics for MPI and temperature imaging revealed an apparent dependence of imaging resolution on harmonic number.

Advanced characterization of magnetization dynamics in iron oxide magnetic nanoparticle tracers.

Characterization of the magnetization dynamics of single-domain magnetic nanoparticles (MNPs) is important for magnetic particle imaging (MPI), magnetic resonance imaging (MRI), and emerging medical diagnostic/therapeutic technologies. Depending on particle size and temperature, nanoparticle magnetization relaxation time constants span from nanoseconds to seconds. In solution, relaxation occurs via coupled Brownian and Néel relaxation mechanisms.

AC magnetometry with active stabilization and harmonic suppression for magnetic nanoparticle spectroscopy and thermometry.

Magnetic nanoparticle (MNP) thermometry based on magnetic particle spectroscopy (MPS) is explored as a potential approach for realizing in-situ temperature measurement of 3D objects. MNP thermometry relies on the nonlinear magnetization response to an AC drive field. This nonlinear response has functional dependence on frequency and temperature, governed by the complex magnetization dynamics of MNPs suspended in solution.

Realizations of the Triple Point of Sulfur Hexafluoride in Transportable and Refillable Cells.

The Minamata Convention on Mercury has created a near-term need to develop alternative fixed points to replace the mercury triple point (Hg TP) for calibration of standard platinum resistance thermometers (SPRTs) on the International Temperature Scale of 1990 (ITS-90). The sulfur hexafluoride (SF) TP is a good candidate to provide adequate "drop-in compatible" replacements for the lowest costs. We report our first results of SF TP realizations performed at the National Institute of Standards and Technology (NIST) using a new series of transportable and refillable triple-point cells.

The NIST Johnson Noise Thermometry System for the Determination of the Boltzmann Constant.

In preparation for the redefinition of the International System of Units (SI), five different electronic measurements of the Boltzmann constant have been performed using different Johnson noise thermometry (JNT) systems over the past seven years. In this paper, we describe in detail the JNT system and uncertainty components associated with the most recent National Institute of Standards and Technology (NIST) determination of the Boltzmann constant: = 1.380642 9(69) × 10 J/K, with a relative standard uncertainty of 5.

An improved electronic determination of the Boltzmann constant by Johnson noise thermometry.

Recent measurements using acoustic gas thermometry have determined the value of the Boltzmann constant, , with a relative uncertainty less than 1 × 10. These results have been supported by a measurement with a relative uncertainty of 1.9 × 10 made with dielectric-constant gas thermometry.

Advances in thermometry.

The last 25 years have seen tremendous progress in thermometry in the moderate temperature range (1 K to 1235 K). Various primary thermometers - based on different physics -have uncovered errors in the International Temperature Scale of 1990 and set the stage for the planned redefinition of the kelvin.