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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Circularly polarized microwaves for magnetic resonance study in the GHz range: Application to nitrogen-vacancy in diamonds

The ability to create time-dependent magnetic fields of controlled polarization is essential for many experiments with magnetic resonance. We describe a microstrip circuit that allows us to generate strong magnetic field at microwave frequencies with arbitrary adjusted polarization. The circuit performance is demonstrated by applying it to an optically detected magnetic resonance and Rabi nutation experiments in nitrogen-vacancy color centers in diamond. Thanks to high efficiency of the proposed microstrip circuit and degree of circular polarization of 85%; it is possible to address the specific spin states of a diamond sample using a low power microwave generator. The circuit may be applied to a wide range of magnetic resonance experiments with a well-controlled polarization of microwaves.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Neural Network Analysis of Nuclear Magnetic Resonance and Infrared Spectra

Nuclear magnetic resonance (NMR) spectroscopy and infrared (IR) spectroscopy are powerful chemical characterization techniques with broad general usage. However, the manual evaluation of the resulting spectra is time-consuming and requires significant expertise, preventing insights from being used in real-time applications. With recent advances in computation and artificial intelligence (AI), new tools are available for automating spectral interpretation. In this work, machine learning (ML) algorithms using 1-dimensional convolutional neural networks (CNNs) were applied to identify common functional groups from spectral information. Raw spectra were collected virtually from the Human Metabolome Database (HMDB) and National Institute of Standards and Technology (NIST) Chemistry WebBook and processed into a suitable standard. Algorithm design was tailored to best fit the nature of the problem, with built-in flexibility to accommodate relevant parameters beyond the raw spectral input, specifically solvent identity and magnetic frequency for NMR. The predictive capability of the algorithm in identifying functional groups is displayed in several examples. This methodology has been compiled into a code repository and could easily be modified to adapt alternative data sources, including other spectrum types. To mitigate overfitting, a common problem in mathematical modeling where overfamiliarity with training data produces trends that are not representative of the general data, a novel metric was developed, referred to as Accufit. Accufit includes a parameter that penalizes substantial differences in the training accuracy and the accuracy of an independent validation set. Examples are presented showing the effectiveness of Accufit in maintaining the model’s predictive capability while controlling the overfitting when used as a custom metric for hyperparameter tuning.

Sturgill, James↗
DOE OSTI2015

Magnetic resonance imaging without field cycling at less than earth's magnetic field

A strong pre-polarization field, usually tenths of a milli-tesla in magnitude, is used to increase the signal-to-noise ratio in ordinary superconducting quantum interference device-based nuclear magnetic resonance/magnetic resonance imaging experiments. Here, we introduce an experimental approach using two techniques to remove the need for the pre-polarization field. A dynamic nuclear polarization (DNP) technique enables us to measure an enhanced resonance signal. In combination with a π/2 pulse to avoid the Bloch-Siegert effect in a micro-tesla field, we obtained an enhanced magnetic resonance image by using DNP technique with a 34.5 μT static external magnetic field without field cycling. In this approach, the problems of eddy current and flux trapping in the superconducting pickup coil, both due to the strong pre-polarization field, become negligible.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Design and evaluation of an open-source, conformable skin-cooling system for body magnetic resonance guided focused ultrasound treatments

Magnetic resonance guided focused ultrasound (MRgFUS) treatment of tumors uses inter-sonication delays to allow heat to dissipate from the skin and other near-field tissues. Despite inter-sonication delays, treatment of tumors close to the skin risks skin burns. This work has designed and evaluated an open-source, conformable, skin-cooling system for body MRgFUS treatments to reduce skin burns and enable ablation closer to the skin. A MR-compatible skin cooling system is described that features a conformable skin-cooling pad assembly with feedback control allowing continuous flow and pressure maintenance during the procedure. System performance was evaluated with hydrophone, phantom and in vivo porcine studies. Sonications were performed 10 and 5 mm from the skin surface under both control and forced convective skin-cooling conditions. 3D MR temperature imaging was acquired in real time and the accumulated thermal dose volume was measured. Gross analysis of the skin post-sonication was further performed. Device conformability was demonstrated at several body locations. Hydrophone studies demonstrated no beam aberration, but a 5–12% reduction of the peak pressure due to the presence of the skin-cooling pad assembly in the acoustic near field. Phantom evaluation demonstrated there is no MR temperature imaging precision reduction or any other artifacts present due to the coolant flow during MRgFUS sonication. The porcine studies demonstrated skin burns were reduced in size or eliminated when compared to the control condition. An open-source design of an MRgFUS active skin cooling system demonstrates device conformability with a reduction of skin burns while ablating superficial tissues.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1972

Magnetic phases in lunar material and their electron magnetic resonance spectra - Apollo 14.

Electron magnetic resonance spectra of soil samples 14163,68, 14148,31, 14149,47, 14156,31, and 14003,60, and of fragmental rocks 14301,66, 14303,42, 14310,68, 14311,36, 14318,36, and 14321,166 have been recorded at 9 and 35 GHz at 300 K and at 9 GHz at 130 K. One spectral component, the characteristic ferromagnetic resonance, of all the soil samples is 50 to 1000 times more intense than any other component in the soils or in the spectra of the rocks. The intensity of this component in Apollo 11, Apollo 12, and Apollo 14 soils varies only within one order of magnitude. It varies with depth below lunar surface but is not correlated with depth. The intensity does not have any correlation with the fraction of glassy particles nor with the fraction of anorthositic particles.

Weeks, R. A.↗
NASA NTRS1992

A comparison of neural network and fuzzy clustering techniques in segmenting magnetic resonance images of the brain

Magnetic resonance (MR) brain section images are segmented and then synthetically colored to give visual representations of the original data with three approaches: the literal and approximate fuzzy c-means unsupervised clustering algorithms and a supervised computational neural network, a dynamic multilayered perception trained with the cascade correlation learning algorithm. Initial clinical results are presented on both normal volunteers and selected patients with brain tumors surrounded by edema. Supervised and unsupervised segmentation techniques provide broadly similar results. Unsupervised fuzzy algorithms were visually observed to show better segmentation when compared with raw image data for volunteer studies. However, for a more complex segmentation problem with tumor/edema or cerebrospinal fluid boundary, where the tissues have similar MR relaxation behavior, inconsistency in rating among experts was observed.

Hall, Lawrence O.↗
DOE OSTI2018

Grassy-ELM regime with edge resonant magnetic perturbations in fully noninductive plasmas in the DIII-D tokamak

Resonant magnetic perturbations (n=3 RMPs) are used to eliminate large amplitude ELMs and reduce the amplitude of weaker "grassy"-ELMs in DIII-D plasmas relevant to the ITER steady-state mission. Fully non-inductive discharges in the ITER shape and pedestal collisionality (n*e ≈ 0.05-0.15) are routinely achieved in DIII-D with RMP suppression of Type-I ELMs. The residual grassy-ELMs deliver a low peak heat flux to the divertor, within 50% of the inter-ELM heat flux, in plasmas with sustained high H-factor (H98y2≈1.2). These grassy-ELM plasmas have a pedestal width that is typically 10% of the poloidal minor radius and ≈50% wider than EPED model predictions. The operating window for RMP grassy-ELMs in edge magnetic safety factor and external torque is in the range required for a steady-state tokamak reactor, such as q95 between 5.3 and 7.1, and co-Ip neutral beam torque down to 0.7 Nm. Small amplitude RMPs (dBvac/B≈1.5x10-4) are sufficient to access this regime, consistent with the large amplification of the vacuum field by the plasma, typically 3-4x the amplification produced by ITER baseline plasmas due to the high pedestal pressure. Cyclic pulsations are observed in the pedestal and plasma magnetic response, consistent with theoretically predicted limit cycle behavior of magnetic island penetration and screening. The grassy ELMs are strongly modulated and sometimes fully suppressed during these pedestal pulsations, consistent with the stabilizing effect of resonant field penetration on peeling-ballooning mode stability. The use of low amplitude edge-resonant magnetic perturbations to access enhanced grassy-ELM operation in a naturally wide pedestal plasma with weak confinement degradation opens the possibility for further optimization of the steady-state tokamak by improved coupling between external fields and weakly stable modes of the plasma.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Can magnetic resonance imaging differentiate among transurethral bulking agent, urethral diverticulum, and periurethral cyst?

Purpose: To evaluate magnetic resonance imaging findings that differentiate among periurethral bulking agents (primarily collagen), urethral diverticulum, and periurethral cyst. Methods: We searched our radiologic database retrospectively from 2001 to 2017 for periurethral cystic lesions, identifying a total of 50 patients with 68 lesions. Final diagnoses in 68 lesions were bulking agents (27), urethral diverticula (29), and periurethral cysts (12). Two abdominal radiologists, blinded to clinical history, independently evaluated T1, T2, and post-contrast images. The readers assessed number, morphological features, location, connection to urethra and mass effect, signal intensity, and enhancement for each lesion. Fisher exact test and logistic regression analysis were performed for each univariate significant feature. The operative and pathologic reports were the reference standard. Results: Magnetic resonance imaging features found more often in bulking agents versus urethral diverticulum were multiple lesions (P = 0.011), upper or upper-mid-urethral location (P ≤ 0.0001), lack of internal fluid/fluid level (P = 0.002), no urethral connection (P = 0.005), T1 isointensity, and T2 mild hyperintensity compared to muscles but lower T2 signal than urine (P < 0.0001). Most cases of urethral diverticula and periurethral cysts were detected at mid- and lower urethra. Urethral diverticula were larger than bulking agents and periurethral cysts (P = 0.005 and P = 0.023) (mean diameter = 24, 16, 15 mm, respectively). Most bulking agents (93%) and urethral diverticula (90%) showed mass effect on urethra, while periurethral cysts (75%) did not (P < 0.0001). Conclusion: Signal intensity and lesion characterization on magnetic resonance imaging can significantly differentiate bulking agent from urethral diverticulum and periurethral cyst. Radiologists should consider differential diagnosis of a bulking agent, especially when distinguishing characteristics described here are present to prevent incorrect diagnosis and ultimately unnecessary surgical intervention.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
NASA NTRS1972

Wide-range nuclear magnetic resonance detector

Compact and easy to use solid state nuclear magnetic resonance detector is designed for measuring field strength to 20 teslas in cryogenically cooled magnets. Extremely low noise and high sensitivity make detector applicable to nearly all types of analytical nuclear magnetic resonance measurements and can be used in high temperature and radiation environments.

Sturman, J. C.↗
DOE OSTI2019

Characteristics of the Magnetic Resonance WPT System Applying a Frequency Converter

Recently, studies on the commercialization of magnetic resonance wireless power transfer (WPT) systems are underway domestically and internationally. The magnetic resonance WPT technology enables power transmission between transmitter and receiver coils with the same resonance frequency. If the resonance frequencies of the transmitter coil and receiver coil are different, the efficiency of the WPT will rapidly decrease. Various organizations, such as A4WP, have been striving to standardize resonance frequencies, but the countries around the world are sticking to their own distinctive standards based on the frequency bands available in their territories. Therefore, each country uses a slightly different resonance frequency band. In this paper, a frequency converter that enables WPT when the transmitter and receiver coils have different resonance frequencies is proposed. The frequency converter consists of two coils, and its structure is very simple. The two coils transmit power using the magnetic induction method, and frequency variation is possible using variable capacitors. It was confirmed from the experiment that WPT is possible even if the resonance frequencies of the transmitter and receiver coils are different.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Prospective, Multicenter Validation Study of Magnetic Resonance Volumetry for Response Assessment After Preoperative Chemoradiation in Rectal Cancer: Can the Results in the Literature be Reproduced?

Purpose: To review the available literature on tumor size/volume measurements on magnetic resonance imaging for response assessment after chemoradiotherapy, and validate these cut-offs in an independent multicenter patient cohort. Methods and Materials: The study included 2 parts. (1) Review of the literature: articles were included that assessed the accuracy of tumor size/volume measurements on magnetic resonance imaging for tumor response assessment. Size/volume cut-offs were extracted; (2) Multicenter validation: extracted cut-offs from the literature were tested in a multicenter cohort (n=146). Accuracies were calculated and compared with reported results from the literature. Results: The review included 14 articles, in which 3 different measurement methods were assessed: (1) tumor length; (2) 3-dimensonial tumor size; and (3) whole volume. Study outcomes consisted of (1) complete response (ypT0) versus residual tumor; (2) tumor regression grade 1 to 2 versus 3 to 5; and (3) T-downstaging (ypT<cT). In the multicenter cohort, best results were obtained for the validation of the whole-volume measurements, in particular for the outcome ypT0 (accuracy 44%-80%), with the optimal cut-offs being 1.6 cm{sup 3} (after chemoradiation therapy) and a volume reduction of Δ80% to 86.6%. Accuracies for whole-volume measurements to assess tumor regression grade 1 to 2 were 52% to 61%, and for T-downstaging 51% to 57%. Overall accuracies for tumor length ranged between 48% and 53% and for 3D size measurement between 52% and 56%. Conclusions: Magnetic resonance volumetry using whole-tumor volume measurements can be helpful in rectal cancer response assessment with selected cut-off values. Measurements of tumor length or 3-dimensional tumor size are not helpful. Magnetic resonance volumetry is mainly accurate to assess a complete tumor response (ypT0) after chemoradiation therapy (accuracies up to 80%).

62 RADIOLOGY AND NUCLEAR MEDICINE↗
NASA NTRS2001

Biomedical Investigations with Laser-Polarized Noble Gas Magnetic Resonance

We are developing laser-polarized noble gas nuclear magnetic resonance (NMR) as a novel biomedical imaging tool for ground-based and eventually space-based application. This emerging multidisciplinary technology enables high-resolution gas-space magnetic resonance imaging (MRI) (e.g., of lung ventilation) as well as studies of tissue perfusion. In addition, laser-polarized noble gases (He-3 and Xe-129) do not require a large magnetic field for sensitive detection, opening the door to practical MRI at very low magnetic fields with an open, lightweight, and low-power device. We are pursuing two specific aims in this research. The first aim is to develop a low-field (< 0.01 T) instrument for noble gas MRI of humans, and the second aim is to develop functional MRI of the lung using laser-polarized Xe-129 and related techniques.

Walsworth, Ronald L.↗
DOE OSTI2025

The Natural Products Magnetic Resonance Database (NP-MRD) for 2025

The Natural Products Magnetic Resonance Database or NP-MRD (https://np-mrd.org) is a comprehensive, freely accessible, web-based resource for the deposition, distribution, extraction and retrieval of nuclear magnetic resonance (NMR) data on natural products. The NP-MRD was initially established to support compound de-replication and data dissemination for the natural products community. However, that community has now grown to include many users from the metabolomics, microbiomics, foodomics and nutrition science fields. Indeed, since its launch in 2021, the NP-MRD has expanded enormously in size, scope and popularity. The current version of NP-MRD now contains nearly 7X more compounds (281,859 vs. 40,908) and 7X more NMR spectra (5.1 million vs. 817,000) than the first release. More specifically, an additional 4.6 million predicted spectra and another 11,000 spectra simulated from experimental chemical shifts were deposited into the database. Likewise, the number of NMR raw spectral data depositions has grown from a 165 spectra per year to more than 10,000 per year. As a result of this expansion, the number of monthly webpage views has grown from 55 to 20,000 and the number of monthly visitors has increased from 7 to 2500. To address this growth and to better support the expanding needs of its diverse community of users, many additional improvements to the NP-MRD have been made. These include significant enhancements to the data submission process, important improvements to the visualization and display of NMR spectra, notable updates to the database’s spectral search utilities and useful additions to support better NMR spectral analysis/prediction. Significant efforts have also been undertaken to remediate and update many of NP-MRD’s database entries. This manuscript describes these database improvements and expansion efforts, along with how they have been implemented and what future upgrades to the NP-MRD are planned.

Artifical Intelligence↗
DOE OSTI2011

Probing the Chemical Stability of Mixed Ferrites: Implications for Magnetic Resonance Contrast Agent Design

Nanomaterials with mixed composition, in particular magnetic spinel ferrites, are emerging as efficient contrast agents for magnetic resonance imaging. Many factors, including size, composition, atomic structure, and surface properties, are crucial in the design of such nanoparticle-based probes because of their influence on the magnetic properties. Silica-coated iron oxide (IO-SiO{sub 2}) and cobalt ferrite (CoIO-SiO{sub 2}) nanoparticles were synthesized using standard high-temperature thermal decomposition and base-catalyzed water-in-oil microemulsion techniques. Under neutral aqueous conditions, it was found that 50-75% of the cobalt content in the CoIO-SiO{sub 2} nanoparticles leached out of the core structure. Leaching caused a 7.2-fold increase in the longitudinal relaxivity and an increase in the saturation magnetization from {approx}48 to {approx}65 emu/g of the core. X-ray absorption fine structure studies confirmed that the atomic structure of the ferrite core was altered following leaching, while transmission electron microscopy and dynamic light scattering confirmed that the morphology and size of the nanoparticle remained unchanged. The CoIO-SiO{sub 2} nanoparticles converted from a partially inverted spinel cation arrangement (unleached state) to an inverse spinel arrangement (leached state). The control IO-SiO{sub 2} nanoparticles remained stable with no change in the structure and negligible changes in the magnetic behavior. This detailed analysis highlights how important understanding the properties of nanomaterials is in the development of reliable agents for diagnostic and therapeutic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Magnetic resonance imaging features of pubic symphysis urinary fistula with pubic bone osteomyelitis in the treated prostate cancer patient

Introduction: Pubic bone osteomyelitis with pubic symphysis urinary fistula represents a debilitating complication of radiation and ablative treatments for prostate cancer. The definitive radiographic diagnosis of this clinical entity is not described. In this study, we characterize the plain film and magnetic resonance imaging findings of pubic osteomyelitis. Materials and Methods: We reviewed a database of prostate cancer survivors with diagnosed pubic osteomyelitis from 2011 to 2015. These patients underwent pelvic plain radiographs and magnetic resonance imaging with T1-weighted and fat-suppressed T2-weighted fast spin echo sequences. Intravenous gadolinium was utilized. The diagnosis was verified with extirpative surgery. 16 patients with diagnosed pubic osteomyelitis from 2011 to 2015 underwent imaging at our institution. Results: All patients demonstrated increased signal on T2- weighted sequences and decreased signal on T1-weighted sequences along the pubic symphysis and the marrow of the involved pubic rami. Inflammatory myositis with diastasis of the pubic symphysis and cortical bone erosion were identified in the majority of patients. Fluid collections were identified in 75% of patients. 63% of conventional radiographs demonstrated no radiographic evidence of pubic osteomyelitis. Conclusion: Magnetic resonance imaging of pubic symphysis osteomyelitis in the prostate cancer survivor is characterized by high signal on T2-weighted images and low signal on T1-weighted images of the involved pubic rami, with the majority of patients demonstrating regional myositis. Imaging data combined with clinical assessment should prompt diagnosis and management of pubic osteomyelitis. Conventional radiography is generally insensitive to these findings. We consider magnetic resonance imaging to be the definitive diagnostic modality for this clinical entity.

62 RADIOLOGY AND NUCLEAR MEDICINE↗