Application of Counter-wound Multi-arm Spirals in HTS Resonator Design.

Significant sensitivity improvements have been achieved by utilizing high temperature superconducting (HTS) resonators in nuclear magnetic resonance (NMR) probes. Many nuclei such as 13C benefit from strong excitation fields which cannot be produced by traditional HTS resonator designs. We investigate the use of double-sided, counter-wound multi-arm spiral HTS resonators with the aim of increasing the excitation field at the required nuclear Larmor frequency for 13C. When compared to double-sided, counter-wound spiral resonators with similar geometry, simulations indicate that the multi-arm spiral version develops a more uniform current distribution. Preliminary tests of a two-arm resonator indicate that it may produce a stronger excitation field.

Guillain-Barré Syndrome after Novel Coronavirus Disease 2019.

BACKGROUND: Novel coronavirus disease 2019 (COVID-19) has affected more than 89 million people worldwide. As the pandemic rages on, more complications of the disease are being recognized, including stroke, cardiovascular disease, thromboembolic events, encephalopathy, seizures, and more. Peripheral nervous system involvement, particularly Guillain-Barré syndrome (GBS), is of special interest, given the increasing reports of cases related to COVID-19. Because of the potentially delayed onset of symptoms of polyradiculoneuropathy and weakness after the traditional COVID-19 symptoms, it is vitally important for emergency physicians to be vigilant and to consider GBS as part of their differential diagnosis. GBS usually occurs after an infectious insult, and a variety of culprit pathogens have been identified in the literature. CASE REPORT: We describe the case of a 35-year-old man who developed GBS after being diagnosed with COVID-19 infection. The patient displayed classic symptoms of neuropathy, areflexia, and lower extremity weakness. Cerebrospinal fluid evaluation demonstrated albuminocytologic dissociation seen in GBS, although anti-ganglioside autoantibodies were negative. These antibodies are often negative and do not exclude the diagnosis. The patient responded clinically to intravenous immunoglobulin therapy and was discharged home. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case report contributes further evidence that COVID-19 joins other organisms as causes of GBS. Emergency physicians are the first point of contact for many patients. Increased awareness of this complication of COVID-19 will lead to higher detection. Prompt recognition could lead to speedier and more complete neurologic recovery of affected patients.

Progress Towards a Higher Sensitivity 13C-Optimized 1.5 mm HTS NMR Probe.

Nuclear magnetic resonance (NMR) probes using thin-film high temperature superconducting (HTS) resonators offer high sensitivity and are particularly suitable for small-sample applications. We are developing an improved 1.5 mm HTS NMR probe designed for operation at 14.1 T and optimized for 13C detection. The total sample volume is about 35 µL and the active sample volume is 20 µL. The probe employs HTS resonators for 13C and 1H transmission and detection and the 2H lock. We examine the interactions of multiple superconducting resonators and normal metal tuning loops on coil resonance frequency and probe sensitivity. We test a recently introduced 13C resonator design, engineered to significantly increase 13C detection sensitivity over previous all-HTS probes. At zero field, we observe a 13C quality factor of 6000 which is several times higher than previous resonators. In this work the coil design considerations and probe build-out procedure are discussed.

Accommodation of Pulsed Field Gradients with Cascade Field Regulation in Powered Magnets.

High magnetic fields significantly improve the resolution and sensitivity of nuclear magnetic resonance (NMR) spectroscopy measurements, which presents exciting research opportunities in areas of chemistry, biology, and material science. Powered magnets can provide much higher magnetic fields than persistent mode superconducting magnets but suffer from temporal magnetic field fluctuations due to power supply ripple and variations in cooling water temperature and flow rate which make powered magnets non-viable for high resolution NMR experiments. Previous work has demonstrated that a multi-rate sampled data cascade control system may be used to improve the resolution of NMR experiments in powered magnets. Despite these advances in reducing temporal magnetic field fluctuations, the field regulation design does not accommodate the use of pulsed field gradients, which are necessary in many NMR experiments. This work presents a control topology which accommodates the use of pulsed field gradient signals with the field regulation system. This control approach is verified using NMR measurements.

Achieving 1 ppm field homogeneity above 24 T: Application of differential mapping for shimming Keck and the Series Connected Hybrid magnets at the NHMFL.

Powered resistive and resistive-superconductive hybrid magnets can reach fields higher than superconducting NMR magnets but lack the field homogeneity and temporal stability needed for high resolution NMR. Due to field fluctuations in powered magnets, commercially available mapping systems fail to produce maps of these magnets with sufficient reproducibility, thus hampering attempts to improve homogeneity of the field they generate. Starting with a commercial mapper, we built a mapping system which uses a two-channel (measurement + reference) mapper probe. We used this system to map and then to shim two magnets of Florida Bitter type at the National High Magnetic Field Laboratory in Tallahassee, FL. With a combination of passive (ferromagnetic) and active shims we achieved 2.3 ppm homogeneity in 1 cm diameter spherical volume (dsv) at 25.0 T in the Keck resistive magnet, and 0.9 ppm homogeneity in 1 cm dsv at 23.5, 28.2, and 35.2 T in the series-connected resistive-superconductive hybrid (SCH) magnet.

The quick sequential organ failure assessment (qSOFA) identifies septic patients in the out-of-hospital setting.

BACKGROUND: Recently a multispecialty, multinational task force convened to redefine the criteria for organ dysfunction, sepsis, severe sepsis, and septic shock. The study recommended the quick sequential organ failure assessment (qSOFA) score to identify sepsis patients. The qSOFA is felt to be the initial screen to prompt a more in-depth sepsis workup. This may be particularly true in resource-limited environments such as the prehospital arena. OBJECTIVES: The goal of this study was to identify whether emergency medical services (EMS) patients who met all three qSOFA criteria correlated with an emergency department (ED) identification of sepsis. METHODS: This was a retrospective chart review of adult patients≥18years of age, meeting qSOFA criteria and presenting to the emergency department between 1/01/2014 and 6/30/2016. Subjects were identified through an electronic query of the EMS record repository. RESULTS: 72 subjects were included in the final analysis. Subjects in the septic group tended to be older with a mean age of 72years vs 64years. There was no observed discrepancy relating to gender. 48 of the subjects (67%) were identified as septic and 24 (33%) were identified as non-septic after review of the ED chart. This yielded a positive predictive value of the prehospital qSOFA as 66.67% (95% CI 55.8-77.6). CONCLUSIONS: EMS patients with positive qSOFA screens were more likely to be septic upon disposition to the ED.

NMR spectroscopy up to 35.2T using a series-connected hybrid magnet.

The National High Magnetic Field Laboratory has brought to field a Series-Connected Hybrid magnet for NMR spectroscopy. As a DC powered magnet it can be operated at fields up to 36.1T. The series connection between a superconducting outsert and a resistive insert dramatically minimizes the high frequency fluctuations of the magnetic field typically observed in purely resistive magnets. Current-density-grading among various resistive coils was used for improved field homogeneity. The 48mm magnet bore and 42mm outer diameter of the probes leaves limited space for conventional shims and consequently a combination of resistive and ferromagnetic shims are used. Field maps corrected for field instabilities were obtained and shimming achieved better than 1ppm homogeneity over a cylindrical volume of 1cm diameter and height. The magnetic field is regulated within 0.2ppm using an external 7Li lock sample doped with paramagnetic MnCl2. The improved field homogeneity and field regulation using a modified AVANCE NEO console enables NMR spectroscopy at 1H frequencies of 1.0, 1.2 and 1.5GHz. NMR at 1.5GHz reflects a 50% increase in field strength above the highest superconducting magnets currently available. Three NMR probes have been constructed each equipped with an external lock rf coil for field regulation. Initial NMR results obtained from the SCH magnet using these probes illustrate the very exciting potential of ultra-high magnetic fields.

(39) K and (23) Na relaxation times and MRI of rat head at 21.1 T.

At ultrahigh magnetic field strengths (B0 ≥ 7.0 T), potassium ((39) K) MRI might evolve into an interesting tool for biomedical research. However, (39) K MRI is still challenging because of the low NMR sensitivity and short relaxation times. In this work, we demonstrated the feasibility of (39) K MRI at 21.1 T, determined in vivo relaxation times of the rat head at 21.1 T, and compared (39) K and sodium ((23) Na) relaxation times of model solutions containing different agarose gel concentrations at 7.0 and 21.1 T. (39) K relaxation times were markedly shorter than those of (23) Na. Compared with the lower field strength, (39) K relaxation times were up to 1.9- (T1 ), 1.4- (T2S ) and 1.9-fold (T2L ) longer at 21.1 T. The increase in the (23) Na relaxation times was less pronounced (up to 1.2-fold). Mono-exponential fits of the (39) K longitudinal relaxation time at 21.1 T revealed T1 = 14.2 ± 0.1 ms for the healthy rat head. The (39) K transverse relaxation times were 1.8 ± 0.2 ms and 14.3 ± 0.3 ms for the short (T2S ) and long (T2L ) components, respectively. (23) Na relaxation times were markedly longer (T1 = 41.6 ± 0.4 ms; T2S = 4.9 ± 0.2 ms; T2L = 33.2 ± 0.2 ms). (39) K MRI of the healthy rat head could be performed with a nominal spatial resolution of 1 × 1 × 1 mm(3) within an acquisition time of 75 min. The increase in the relaxation times with magnetic field strength is beneficial for (23) Na and (39) K MRI at ultrahigh magnetic field strength. Our results demonstrate that (39) K MRI at 21.1 T enables acceptable image quality for preclinical research. Copyright © 2016 John Wiley & Sons, Ltd.

Modulation of cross polarization in motionally averaged solids by Variable Angle Spinning NMR.

In systems where the dipolar couplings are partially averaged by molecular motion, cross-polarization is modulated by sample spinning. The cross-polariation efficiency in Variable Angle Spinning (VAS) and Switched Angle Spinning (SAS) experiments on mobile samples is therefore strongly dependent on the spinning angle. We describe simulations and experimental measurements of these effects over a range of spinning angles from 0° to 90°.

Finding the best examples of healthcare quality improvement in Sub-Saharan Africa.

BACKGROUND: The purpose of this study was to summarise the current state of healthcare quality improvement literature focusing on sub-Saharan Africa. METHODS: Conventional methods of searching the literature were quickly found to be inadequate or inappropriate, given the different needs of practitioners in sub-Saharan Africa, and the inaccessibility of the literature. RESULTS: The group derived a core list of what were deemed exemplary quality improvement articles, based on consensus and a search into the "grey" literature of quality improvement. CONCLUSIONS: Quality improvement articles from sub-Saharan Africa are difficult to find, and suffer from a lack of centrality and organisation of literature. Efforts to address this are critical to fostering the growth of quality improvement literature in developing country settings.

Pneumatic switched angle spinning NMR probe with capacitively coupled double saddle coil.

Switched angle spinning (SAS) experiments can be used for generating isotropic-anisotropic correlations in oriented samples in a single experiment. In order for these methods to become widespread, specialized hardware is required. Here we describe the electronic and mechanical design and performance of a double-resonance SAS probe. Unlike many previous SAS probe implementations, the focus here is on systems where the dipolar couplings are partially averaged by molecular motion. This probe has a moving double saddle coil capacitively coupled to the stationary circuit. Angle switching is accomplished by a steam engine-type pneumatic mechanism. The speed and stability of the switching hardware for SAS experiments are demonstrated using spectra of model compounds.