Low Field Research Articles

Exploring charge generation and separation in tandem organic light-emitting diodes based on magneto-electroluminescence

5,6,11,12-tetraphenylnaphthacene (rubrene) exhibits resonant energy properties (E S1,rub ≈ 2E T1,rub), resulting in rubrene-based organic light-emitting diode (OLED) devices that undergo the singlet fission (STT) process at room temperature. This unique process gives rise to a distinct magneto-electroluminescence (MEL) profile, differing significantly from the typical intersystem crossing (ISC) process. Therefore, in this paper, we investigate charge generation and separation in the interconnector, and the mechanism of charge transport in tandem OLEDs at room temperature using MEL tools. We fabricate tandem OLEDs comprising green (Alq3) and yellow (Alq3:rubrene) electroluminescence (EL) units using different interconnectors. The results demonstrate that all devices exhibited significant rubrene emission. However, the MEL did not exhibit an STT process with an increasing magnetic field, but rather a triplet–triplet annihilation (TTA) process. This occurrence is attributed to direct carrier trapping within doped EL units, which hinders the transport of rubrene trapped charges, consequently prolonging the lifetime of triplet excitons (T1,rub). Thus, the increased T1,rub concentration causes TTA to occur at room temperature, causing the rapid decrease of MEL in all devices under high magnetic fields. In devices where only the TTA process occurs, the TTA increases with the increasing current. Consequently, the high magnetic field of devices A–C is only related to TTA. Notably, there exists a high magnetic field TTA of device D in the Alq3/1,4,5,8,9,11-Hexaazatriphenylene-hexacarbonitrile interconnector regardless of the current. This occurs because both EL units in the device emit simultaneously, resulting in the triplet-charge annihilation process of Alq3 in the high magnetic field of the MEL. Moreover, the rapid increase in MEL at low magnetic field across all devices is attributed to the ISC between Alq3 polaron pairs. This entire process involves Förster and Dexter energy transfer. This article not only provides novel insights into charge generation and separation in the interconnector but also enhances our understanding of the microscopic mechanisms in tandem OLED devices.

Analysis of VOCs in Liquids through Vaporization in a Tubular Oven Monitored by Chemical Ionization Mass Spectrometry.

The analysis of chemical compounds present at trace levels in liquids is important not only for environmental measurements but also, for example, in the health sector. The reference technique for the analysis of Volatile Organic Compounds (VOCs) in liquids is GC, which is difficult to use with an aqueous matrix. In this work, we present an alternative technique to GC to analyze VOCs in water. A tubular oven is used to completely vaporize the liquid sample deposited on a gauze. The oven is heated in the presence of a dinitrogen flow, and the gas is analyzed at the exit of the oven by a chemical ionization mass spectrometer developed in our laboratory. It is a low magnetic field Fourier Transform Ion Cyclotron Resonance (FT-ICR) optimized for real-time analysis. The Proton Transfer Reaction (PTR) used during the Chemical Ionization event results in the selective ionization of the VOCs present in the gas phase. The optimization of the desorption conditions is described for the main operating parameters: temperature ramp, liquid quantity, and nitrogen flow. Their influence is studied using a 100 ppmv aqueous toluene solution. The analytical method is then tested on a mixture of seven VOCs.

Ultrahigh Piezoelectric Response Obtained by Artificially Generating a Large Internal Bias Field in BiFeO3–BaTiO3 Lead‐Free Ceramics

AbstractPiezoelectric actuators are vital devices that convert electrical signals into mechanical strain, offering rapid and precise responses. Lead‐based piezoceramics have traditionally been the preferred choice for commercial piezoelectric actuators, while the low Curie temperature and the rising environmental concerns hinder their applications at high temperatures. In this study, a novel strategy is proposed to achieve high piezoelectric responses in lead‐free 0.67Bi1.05FeO3–0.33BaTiO3 (67BF‐33BT) ceramics with high Curie temperature by artificially generating a large internal bias field through repeat poling and aging treatments. A comprehensive exploration of how this internal bias field responds to applied electric fields and temperature variations has been conducted. The results suggest that the internal bias field originates from two aspects, one arises from the free charges that compensate for the depolarization field, while the other is attributed to the highly oriented defect dipoles. As a result of this internal bias field, the ceramics exhibit asymmetric strain–electric field (S–E) behaviors, resulting in a high strain (ε = 0.21%) and an extremely high piezoelectric coefficient (d33* = 1033.70 pm V−1) when subjected to low electric field (20 kV cm−1), along with good temperature stability from room temperature (RT) to 100 °C.

Utilization of electronic health record sex and gender demographic fields: a metadata and mixed methods analysis.

Despite federally mandated collection of sex and gender demographics in the electronic health record (EHR), longitudinal assessments are lacking. We assessed sex and gender demographic field utilization using EHR metadata. Patients ≥18 years of age in the Mass General Brigham health system with a first Legal Sex entry (registration requirement) between January 8, 2018 and January 1, 2022 were included in this retrospective study. Metadata for all sex and gender fields (Legal Sex, Sex Assigned at Birth [SAAB], Gender Identity) were quantified by completion rates, user types, and longitudinal change. A nested qualitative study of providers from specialties with high and low field use identified themes related to utilization. 1576120 patients met inclusion criteria: 100% had a Legal Sex, 20% a Gender Identity, and 19% a SAAB; 321185 patients had field changes other than initial Legal Sex entry. About 2% of patients had a subsequent Legal Sex change, and 25% of those had ≥2 changes; 20% of patients had ≥1 update to Gender Identity and 19% to SAAB. Excluding the first Legal Sex entry, administrators made most changes (67%) across all fields, followed by patients (25%), providers (7.2%), and automated Health Level-7 (HL7) interface messages (0.7%). Provider utilization varied by subspecialty; themes related to systems barriers and personal perceptions were identified. Sex and gender demographic fields are primarily used by administrators and raise concern about data accuracy; provider use is heterogenous and lacking. Provider awareness of field availability and variable workflows may impede use. EHR metadata highlights areas for improvement of sex and gender field utilization.

Influence of thickness and domain structure on the vortex instability of superconducting/ferromagnetic bilayers

We report on the vortex instability in superconducting/ferromagnetic (FM) bilayers. Samples consisting of a 23 nm thick Mo2N superconducting layer with a capping layer of Co, Fe20Ni80, or FePt ferromagnets were grown by sputtering at room temperature on silicon (100). Our study reveals that the critical vortex velocity in these superconducting bilayers is significantly influenced by the thickness of the FM layers rather than the specific magnetic domain structure. When comparing samples with FM layers of 10 nm and 50 nm thickness, we observe a notable increase in vortex velocities at low magnetic fields, with speeds rising from approximately 3.5 km s−1 to around 6 km s−1 as the thickness increases. This trend extends to moderate and high magnetic fields. Furthermore, we establish a direct correlation between vortex velocities and the thermal conductance of the FM layers. These findings provide valuable insights for the interplay of magnetic and thermal properties within these hybrid systems, with potential implications for the design of future devices and applications.

Abstract 128: Multi-Direction Diffusion Weighted Imaging on Portable, Low-Field Magnetic Resonance Imaging

Background and aims: Portable, low-field (LF) MRI has the potential to improve access to expeditious, definitive brain imaging and facilitate diagnosis of acute stroke. Currently available diffusion-weighted imaging (DWI) protocols at LF are limited to a single diffusion direction due to acquisition duration. However, single-direction diffusion has reduced sensitivity for detecting acute ischemic infarcts, particularly small lesions residing in white matter tracts. The purpose of this study was to establish the feasibility of acquiring multi-direction DWI compared with single-direction counterparts on LF-MRI. Methods: Patients presenting with a diagnosis of acute ischemic stroke between July and September 2023 were eligible. Consented patients underwent DWI acquisition on a 0.064T LF-MRI (Mk1.9; Hyperfine Research Inc). Three diffusion directions (x, y, and z) were acquired with a b weighting of 900 s/mm 2 and a single acquisition with a b 0 s/mm 2 . The b 900 images were co-registered to the b 0, trace and apparent diffusion coefficient (ADC) maps calculated, and the final images interpolated at 1 mm 3 . Results: Ten patients presenting to the Massachusetts General Hospital with acute ischemic stroke were consented and imaged within 72 hours of last known well. The total acquisition time was 14 minutes, with all subjects able to tolerate the scan duration. Ischemic lesions as small as 0.1 mL were detectable on the LF-MRI (17.5 +/- 18.2 mL). An example of each diffusion direction individually, the combined trace, and corresponding ADC maps are shown in Figure 1, compared with conventional high-field (HF) diffusion images acquired within 30 minutes of the LF acquisition. Conclusion: Multi-direction DWI imaging is feasible on a 0.064T LF-MRI scanner. Our experience suggests further modifications to the pulse sequence and scanner configuration may facilitate a reduction in acquisition time, improve resolution, or both.

Electric Field Measurement Techniques And Their Practical Applications

Static, quasi-static and low frequency electric fields are being used in many fields of science and engineering. They are utilized in research studies of fundamental properties of materials, exploration of high-energy physics, in biology and medicine, etc., but also in a multitude of practical applications such as precipitation, painting, xerography, to name a few. In all these endeavors it is a good practice to find out what the electric fields are in terms of value, direction, and temporal and spatial distribution. This information can be crucial for making the application successful. Electric fields are also being created by many naturally occurring and man-made phenomena. The aim of this paper is to present different options for electric field evaluation and measurement. Aside from traditional approaches, new concepts using machine learning in electric field assessment and interpretation are discussed. As technologies progress, electric field detection methods become a part of sensor fusion realm by providing additional capabilities in process, environmental and situational awareness monitoring. They can provide unique information enhancing our knowledge and understanding. Examples of such sensor integrations are shown and explained.

The differences in phase transition characteristics of antiferroelectric PbZrO3 thin films via grain size engineering

PbZrO3 (PZO) possesses a unique antiferroelectric-ferroelectric (AFE-FE) phase transition under an external electric field and engages more attention in understanding and regulating the phase transition behavior. In this work, changing annealing temperature (600–750 °C) and ultralow content (5‰) ions doping are used to optimize the phase transition of PZO films via grain size engineering. As annealing temperature increases, the maximum polarization Pmax increases but forward/backward switching fields EF/EA reduce accompanied by the average grain size enhances from 622 to 686 nm. Following, 5‰ mol aliovalent ion La3+ or K+ doped PZO-650 films both enhance Pmax and EF/EA indicating the strengthened antiferroelectricity, and meanwhile the grain size enhances to ∼800 nm. A high discharge density of 31 J/cm3 is achieved for 5‰ mol La-doped PZO films at a low electric field of 1 MV/cm, which is ∼100 % higher than those of pure PZO films at different annealing temperatures. This work compares the phase transition characteristics changes in PZO films by changing annealing temperature and ultra-low content ion doping strategy, which would provide new thinking in grain size-engineered antiferroelectric materials for energy storage applications.

HGTD DC/DC converter in low temperature and magnetic field operation

The BPOL12V is a DC/DC converter designed to supply power to the High Granularity Timing Detector (HGTD) as part of the ATLAS Phase II upgrade project. The HGTD operates in an environment characterized by low temperatures and a magnetic field. Ensuring the reliable functionality of the BPOL12V under such conditions is of utmost importance. This paper outlines a series of functionality tests for the BPOL12V, including efficiency, ripple, and rise/fall edge assessments across various operational scenarios. The performance of the BPOL12V consistently meets the requirements of the HGTD, whether it operates in low temperatures down to -30 °C or in the presence of a 0.4 T magnetic field.

Electromagnetic analysis of permanent magnet-assisted synchronous reluctance motor based on magnetic equivalent circuit

As rare-earth permanent magnet prices continue to fluctuate, interest in non-rare-earth permanent magnet-assisted synchronous reluctance motors (PMa-SynRMs) is increasing. However, non-rare-earth PMa-SynRMs have a multi-layer structure with interior permanent magnets to compensate for the low magnetic fields. Therefore, the rotor has several design parameters, and electromagnetic analysis is time-consuming. To overcome these challenges, magnetic equivalent circuit analysis was used to perform fast electromagnetic analysis of non-rare-earth PMa-SynRMs. In addition, the validity of the proposed method was confirmed through a comparison of the obtained results with those of finite element analysis.

Statistical Analysis of Mercury's Magnetotail Lobe Field Using MESSENGER Observations

AbstractThe magnetotail lobe region at Mercury is characterized by low plasma density and low magnetic field variability compared to the nightside magnetosheath and central plasma sheet. At Mercury, as well as other planets, lobe magnetic fields play a crucial role in storing and releasing magnetic flux in response to changing upstream solar wind conditions such as interplanetary magnetic field (IMF) orientation and solar wind dynamic pressure (Pdyn). This makes the region significant for studying the magnetospheric interaction with the intense solar wind conditions at Mercury's orbit. Here, we identify and analyze magnetotail lobe observations made by the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft during its 4 years orbital phase. We empirically determined a set of criteria using magnetometer (MAG) and the Fast Imaging Plasma Spectrometer instruments onboard MESSENGER to identify lobe magnetic field intervals. From 3,332 MESSENGER orbits, we identify 1,242 lobe field intervals. We derive an expression for the average lobe magnetic field strength in nanotesla with respect to radial distance downtail: Blobe(r) = (135 ± 8) * r(−2.1±0.3) + (31 ± 8). The lobe magnetic field exhibits both small‐scale (∼3 min) and orbit‐to‐orbit (∼8–12 hr) variability in magnetic field strength compared to this averaged field strength expression. The orbit‐to‐orbit variability in lobe field strength is not significantly correlated with estimated IMF orientation, but is directly correlated with Pdyn. Thus, our findings provide evidence for the pressure balance between the inward facing Pdyn on the nightside magnetopause and the outward facing magnetic pressure supplied by the lobes.

Improving Energy Storage Properties of KNN Ceramic through Composition Modification

In this study, (1−x)K0.5Na0.5NbO3−xBa0.5Sr0.5(Zn1/3Nb2/3)O3, [(1−x)KNN-xBSZN] lead-free relaxor ceramics were fabricated by a conventional solid-state reaction method. XRD and Raman spectra confirm the R-C phase transition of the ceramics. The incorporation of BSZN effectively suppresses grain growth, enhanced the electrical resistivity, and improved the relaxation behavior. By analyzing the ferroelectric property of the sample under breakdown field, it is found that when x = 0.08, the ceramic demonstrates the smallest variation in polarization (∆P = 12.43 μC cm−2), the highest recoverable energy storage density (W rec = 0.8 J cm−3) and energy storage efficiency (η = 58.8%). The enhancement of energy storage is attributed to the introduction of BSZN, which effectively suppresses grain growth and improves the relaxation behavior of the ceramics. The results show that the ceramic enables be used in pulsed-power systems at low electrical field.

Perineural differentiation in neurotized nevi

BackgroundPerineuriomatous melanocytic nevi are rare and this may indicate the similar embryological source of melanocytes and peripheral nerves in the neural crest. Neurotized melanocytic nevi may resemble nerve sheath tumors histologically, and show schwannian differentiation. However, literature on whether neurotized nevi differentiate into perineural cells is controversial. We examined our cases of neurotized nevi for evidence of perineural differentiation. Materials and methodsA total of 100 benign nevi with large neurotized component (microscopically involved a low power field 4.2 mm in diameter) were prospectively evaluated in excisional biopsy samples. Immunohistochemical stainings for EMA, Claudin1, Glut1 and neurofilament were performed. ResultsPerineural differentiation was immunohistochemically detected in the neurotized component of the nevi in 61% of the cases with EMA and in all the cases with Glut1 and Claudin1. Axonal differentiation was not detected with neurofilament. The expression pattern, especially with Glut1, was usually in form of partial or complete staining surrounding the Meissner's corpuscle-like structure (MCLS). Also, a linear/curvilinear staining pattern was observed particularly with Claudin1. A diffuse staining pattern with EMA, Glut1 and Claudin1 was detected in a case with a microscopically distinct whorl structure, and in which spindle cells are separated from the superficial epithelioid melanocytes with an abrupt transition histologically. These findings of the case are compatible with previous reports of perineuromatous nevus. ConclusionPerineural differentiation is not uncommon and immunohistochemically observed in all nevi with a relatively large component of neurotization. To prevent misdiagnosing desmoplastic melanoma and overtreating patients, it is crucial to be aware of perineuromatous nevi.

Nonmetallic graphite for tumor magnetic hyperthermia therapy

Magnetic hyperthermia therapy (MHT) has garnered immense interest due to its exceptional spatiotemporal specificity, minimal invasiveness and remarkable tissue penetration depth. Nevertheless, the limited magnetothermal heating capability and the potential toxicity of metal ions in magnetic materials based on metallic elements significantly impede the advancement of MHT. Herein, we introduce the concept of nonmetallic materials, with graphite (Gra) as a proof of concept, as a highly efficient and biocompatible option for MHT of tumors in vivo for the first time. The Gra exhibits outstanding magnetothermal heating efficacy owing to the robust eddy thermal effect driven by its excellent electrical conductivity. Furthermore, being composed of carbon, Gra offers superior biocompatibility as carbon is an essential element for all living organisms. Additionally, the Gra boasts customizable shapes and sizes, low cost, and large-scale production capability, facilitating reproducible and straightforward manufacturing of various Gra implants. In a mouse tumor model, Gra-based MHT successfully eliminates the tumors at an extremely low magnetic field intensity, which is less than one-third of the established biosafety threshold. This study paves the way for the development of high-performance magnetocaloric materials by utilizing nonmetallic materials in place of metallic ones burdened with inherent limitations.

Lab-based Martian analogue experiments investigating electric and magnetic fields of dust devils

Dust devils – rotating vortices of lofted particulates formed by convection from solar heating - are a prevalent aspect of Martian weather.Within a dust devil, particles become charged though triboelectrification, and observations of terrestrial dust devils have revealed electric and magnetic fields. Understanding the behaviour of these aeolian events is vital for mission planning and duration, for example, with the Insight lander as a prime example of a mission cut short due to obscuration of solar panels by lofted dust, which is highly likely to be charged. Charged dust devils on Mars strongly imply the existence of electric discharges due to the low breakdown field. The existence of discharges would in turn imply a global electric circuit on the planet – with implications for organic chemical formation and methane losses.This work presents a laboratory-based experimental set up for investigation into both electric and magnetic fields and the feasibility of using Martian analogue dust as alternative to in-situ measurements. In a dust devil, there are two main driving motions – a vertical separation of small and large particles, and the characteristic tight spiralling motion. The experimental set-up splits these components, allowing investigation into each. It is made up of a carefully designed cylindrical tank into which dusts or powders can be dropped to allow triboelectric charging as they fall under gravity. The base of the tank has a Faraday cup for charge measurement and there is also a field mill looking into the tank from the top. The rotational component is achieved using a paddle arrangement for samples placed in the base of the tank. Electric and magnetic fields have successfully been detected from charged dust with this system.

Generalization of numerical simulation results on the electrical coalescence threshold for two conducting droplets based on non-dimensional parameters

Electrocoalescence, the physical process underlying the demulsification of a dielectric dispersion medium containing small conductive droplets (e.g., water), involves droplet merging at low electric fields and splashing at higher voltages. Understanding the physics of electrocoalescence is crucial for optimizing industrial electrocoalescers. However, mathematical modeling of these complex, multiphysics phenomena is challenging, and many published results are questionable. In this study, we utilized a previously developed reliable model for computing the threshold between electrical coalescence and non-coalescence. We investigate the applicability of dimensionless parameters, such as the Ohnesorge number and Weber electric number, to describe the coalescence threshold for uncharged droplets of equal size. Using COMSOL Multiphysics software, we analyze the dependency of the threshold electric field strength on water droplet radius and establish an equivalent dimensionless relationship. Our findings reveal that a universal Weber number quite accurately describes the threshold over a wide range of droplet radii, regardless of changes in liquid viscosity and inter-electrode gap. Direct mathematical simulations using up-to-date numerical models enable us to determine non-dimensional parameter values corresponding to the threshold electric field strength, providing generalizable results.

Research and development of the high precision low field dipole magnet for CEPC Booster

In the Conceptual Design Report (CDR) stage of the Circular Electron and Positron Collider (CEPC), the injection energy of the Booster is 10 GeV and minimal working field of the dipole magnets is only 29 G, the magnets with iron cores could not meet the requirement of the field precision due to the remnant field. In the CEPC Technical Design Report (TDR) stage, the injection energy of the Booster is increased to 30 GeV and the minimal working field of the dipole magnets is raised to 95 G so that the influence of the remnant field becomes relatively small, the iron core dipole magnets can be used for the Booster. In this paper, the technical design of the CEPC Booster dipole magnets is described, the development and test of a full scale prototype pure dipole magnet are presented.

Effect of low intensity direct-current electric field on anti-browning of apple juice: Enzyme inactivation kinetics and juice properties

For the first time, the efficacy of low intensity (1–7 V/cm) direct-current (DC) electric field in preventing browning in apple juice is examined. The results show that applying a 5 V/cm electric field can inactivate 89.24% of polyphenol oxidase (PPO) within 90 min and achieve complete inactivation of peroxidase (POD) within 70 min, maintaining the juice temperature below 30 °C throughout the process. The Weibull model fits the PPO and POD inactivation effectively, suggesting varied responses among isoenzymes. Under the optimal conditions (5 V/cm for 90 min), a 15.89% increase in total phenolic content (TPC) was observed alongside significant improvements in antioxidant activity. Furthermore, this method preserved the natural flavor and lightened the color of the apple juice, enhancing its sensory appeal. These findings indicate that low intensity DC electric field is an innovative and effective choice for preventing juice browning, offering significant potential for application in the food industry.

Opportunities for Improving Glaucoma Clinical Trials via Deep Learning-Based Identification of Patients with Low Visual Field Variability

Develop and evaluate the performance of a deep learning model (DLM) that forecasts eyes with low future visual field (VF) variability, and study the impact of using this DLM on sample size requirements for neuroprotective trials. Retrospective cohort and simulation study. We included 1 eye per patient with baseline reliable VFs, OCT, clinical measures (demographics, intraocular pressure, and visual acuity), and 5 subsequent reliable VFs to forecast VF variability using DLMs and perform sample size estimates. We estimated sample size for 3 groups of eyes: all eyes (AE), low variability eyes (LVE: the subset of AE with a standard deviation of mean deviation [MD] slope residuals in the bottom 25th percentile), and DLM-predicted low variability eyes (DLPE: the subset of AE predicted to be low variability by the DLM). Deep learning models using only baseline VF/OCT/clinical data as input (DLM1), or also using a second VF (DLM2) were constructed to predict low VF variability (DLPE1 and DLPE2, respectively). Data were split 60/10/30 into train/val/test. Clinical trial simulations were performed only on the test set. We estimated the sample size necessary to detect treatment effects of 20% to 50% in MD slope with 80% power. Power was defined as the percentage of simulated clinical trials where the MD slope was significantly worse from the control. Clinical trials were simulated with visits every 3 months with a total of 10 visits. A total of 2817 eyes were included in the analysis. Deep learning models 1 and 2 achieved an area under the receiver operating characteristic curve of 0.73 (95% confidence interval [CI]: 0.68, 0.76) and 0.82 (95% CI: 0.78, 0.85) in forecasting low VF variability. When compared with including AE, using DLPE1 and DLPE2 reduced sample size to achieve 80% power by 30% and 38% for 30% treatment effect, and 31% and 38% for 50% treatment effect. Deep learning models can forecast eyes with low VF variability using data from a single baseline clinical visit. This can reduce sample size requirements, and potentially reduce the burden of future glaucoma clinical trials. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Enhanced energy-storage performances in lead-free ceramics via the Co-modulation by conduction effect and domain engineering

The main factors that limit the practical application of bismuth ferrite-based energy storage ceramics are their low breakdown electric field strength and large remnant polarization. Here, we achieve high energy storage behavior in (0.72-x)BiFeO3-0.28BaTiO3-xLa(Mg1/2Zr1/2)O3 (BF-BT-xLMZ) ferroelectric ceramics through directional defect modulation based on a transformation of the conductance mechanisms. The systematic experimental analysis coupled with the vacancy sink model suggests that the introduction of LMZ changes the trap-filled-limit conduction mode dominated by oxygen vacancy, leading to 4 times enhancement of the breakdown electric field in BF-BT-0.2LMZ. Meanwhile, the induced nanodomains create a size effect that effectively reduces the remnant polarization, resulting in an increase in efficiency by 3.5 times. As a result, the recoverable energy storage density of the ceramic reaches an outstanding 4.2 J/cm3, together with a high efficiency of 75.2%. This work provides a feasible strategy for the development of ferroelectric family in the field of high-energy storage.