Highest Field Strength Research Articles

Mid-infrared dielectric laser acceleration in a silicon dual pillar structure.

Dielectric laser accelerators use near-infrared laser pulses to accelerate electrons at dielectric structures. Driving these devices with mid-infrared light should result in relaxed requirements on the electron beam, easier fabrication, higher damage threshold, and thus higher acceleration gradients. In this paper, we demonstrate dielectric laser acceleration of electrons driven with 10 μm light in a silicon dual pillar structure. We observe the acceleration of 27 keV electrons by 1.4 keV, corresponding to a 93 MeV/m acceleration gradient. The damage threshold of the structures of 3.3 ± 0.6 GV/m peak field is significantly higher than for near-infrared accelerators. The dual pillar acceleration structure itself even survived 5.2 ± 0.9 GV/m, the highest field strength we could achieve with the current system. This together with the larger structure acceptance bodes well for future dielectric laser accelerators driven with mid-infrared light.

Polarization-Dependent Formation of Extremely Compressed Femtosecond Wave Packets and Supercontinuum Generation in Fused Silica

Previous studies of formation of extremely compressed wave packets during femtosecond filamentation in the region of anomalous group velocity dispersion in solid dielectrics mostly considered the case of linearly polarized laser pulses. However, recent results suggest potential applications of polarization state manipulation for ultrafast laser writing of optical structures in bulk solid-state media. In the present work, evolution of radiation polarization parameters during formation of such extreme wave packets at the pump wavelength of 1900 nm in fused silica is studied numerically on the basis of the carrier-resolved unidirectional pulse propagation equation (UPPE). It was revealed that initial close-to-circular polarization leads to higher intensity of the anti-Stokes wing in the spectrum of the generated supercontinuum. Numerical simulations indicate a complex, space–time variant polarization state, and the resulting spatiotemporal electric field distribution exhibits a strong dependence on the initial polarization of the femtosecond pulse. At the same time, electric field polarization tends to linear one in the region with the highest field strength regardless of the initial parameters. The origin of this behavior is attributed to the properties of the supercontinuum components generation during filament-induced plasma formation.

Managing Patients With Unlabeled Passive Implants on MR Systems Operating Below 1.5 T.

The standard of care for managing a patient with an implant is to identify the item and to assess the relative safety of scanning the patient. Because the 1.5 T MR system is the most prevalent scanner in the world and 3 T is the highest field strength in widespread use, implants typically have "MR Conditional" (i.e., an item with demonstrated safety in the MR environment within defined conditions) labeling at 1.5 and/or 3 T only. This presents challenges for a facility that has a scanner operating at a field strength below 1.5 T when encountering a patient with an implant, because scanning the patient is considered "off-label." In this case, the supervising physician is responsible for deciding whether to scan the patient based on the risks associated with the implant and the benefit of magnetic resonance imaging (MRI). For a passive implant, the MRI safety-related concerns are static magnetic field interactions (i.e., force and torque) and radiofrequency (RF) field-induced heating. The worldwide utilization of scanners operating below 1.5 T combined with the increasing incidence of patients with implants that need MRI creates circumstances that include patients potentially being subjected to unsafe imaging conditions or being denied access to MRI because physicians often lack the knowledge to perform an assessment of risk vs. benefit. Thus, physicians must have a complete understanding of the MRI-related safety issues that impact passive implants when managing patients with these products on scanners operating below 1.5 T. This monograph provides an overview of the various clinical MR systems operating below 1.5 T and discusses the MRI-related factors that influence safety for passive implants. Suggestions are provided for the management of patients with passive implants labeled MR Conditional at 1.5 and/or 3 T, referred to scanners operating below 1.5 T. The purpose of this information is to empower supervising physicians with the essential knowledge to perform MRI exams confidently and safely in patients with passive implants. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 3.

Transient surface charge of SF 6 ‐filled direct current gas‐insulated transmission lines insulator under thermal‐electric coupled fields: effects of ambient temperature, load current and gas pressure

The transient surface charge characteristics of a basin-type insulator in horizontally installed SF6-filled direct current gas-insulated transmission lines (DC-GIL) are investigated based on a three-dimension (3D) simulation model under thermal-electric coupled stress. The influence of ambient temperature, load current and gas pressure on the surface charge and electric field characteristics is investigated. Simulation results indicate that the surface charge accumulation process is accelerated due to the promotion of bulk conduction under high ambient temperature, high load current and low gas pressure. The transient field variation is accelerated as the consequence. The highest field strength on the convex surface increases and moves towards the enclosure with increasing time. With increasing load current, the field strength increases due to the influence of charge accumulation and temperature-dependent conductivity of the insulator. It is revealed that the transient surface charge under coupled fields should be focused when dealing with the insulation characteristics of DC-GIL insulators during long-term operation. The mentioned operating conditions should be paid attention. This method introduced in this study can help to evaluate the 3D transient charge and field characteristics under various conditions.

Generation of a Flat-Top Magnetic Field With Multiple-Capacitor Power Supply

The flat-top magnetic field (FTMF) can meet scientific experimental requirements for higher magnetic intensity, longer flat-top pulse width, and lower ripple in physics, chemistry, biology, and other scientific fields. This paper proposes an FTMF system powered by the multiple-capacitor power supply (MCPS). The MCPS consists of several capacitor banks with customizable capacitance and given voltage. These banks discharge sequentially based on the designed time-series to yield an FTMF. Compared with other methods for generating the FTMF, the MCPS can easily generate FTMFs with high parameters and flexible adjustability of the pulse width. Due to the coupled variable parameters between and within the power supply and the magnet, a hybrid algorithm based on the genetic algorithm (GA) and particle swarm optimization (PSO) is applied to calculate the discharge parameters of the MCPS. The optimal solution from the GA-PSO hybrid algorithm is visualized and selected by the basis vector method. For verifying the effectiveness of the MCPS and the optimization method, a series of FTMFs at different magnetic field strength levels are modeled in MATLAB/Simulink and achieved in the experiment. The generated FTMF with the highest field strength is 50 T, its pulse width is 70 ms, and ripple is less than 0.7%.

Percutaneous needle biopsy under 1.2 Tesla open MRI guidance.

To evaluate the feasibility of percutaneous needle biopsy using a 1.2 Tesla open magnetic resonance imaging (MRI) system, which has the highest field strength among the currently available open MRI systems. This single-center prospective study included 10 patients. The primary endpoint was the feasibility of biopsy needle insertion into a target lesion under 1.2 Tesla open MRI guidance. The secondary endpoints included adverse events, device failures, and success of tissue specimen acquisition. Biopsy was performed for targets in various organs using an MRI-compatible coaxial needle system consisting of a 16G introducer needle and 18G semi-automatic biopsy needle. A newly developed body coil with a suitable design for intervention was used for intraprocedural imaging. Biopsy procedures were performed for six musculoskeletal masses, two retroperitoneal masses, one renal mass, and one liver mass. The median diameter of the targets was 4.9cm (range 2.1-22.8cm). MRI-guided biopsy needle insertion was feasible in all 10 patients. In total, four grade 1 adverse events (as per Common Terminology Criteria for Adverse Events version 4.0) occurred in three patients. Adequate biopsy specimens for pathological diagnosis were successfully obtained from all 10 patients. Percutaneous needle biopsy using a 1.2 Tesla open MRI system was feasible for relatively large targets, especially in the musculoskeletal region.

Influence of the Distribution of the Properties of Permanent Magnets on the Field Homogeneity of Magnet Assemblies for Mobile NMR

We optimized the magnetic field homogeneity of two canonical designs for mobile microfluidic nuclear magnetic resonance (NMR) applications: two parallel magnets with an air gap and a modified Halbach array. Along with the influence of the sample length, general design guidelines will be presented. For a fair comparison, the sensitive length of the sample has been chosen to be the same as the gap size between the magnets to ensure enough space for the transmitting and receiving unit, as well as basic electric shimming components. Keeping the compactness of the final device in mind, a box with an edge length 5 times the gap size has been defined, in which the complete magnet configuration should fit. With the chosen boundary conditions, the simple parallel cuboid configuration reaches the best homogeneity without active shimming ( 0.5B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> , 41 ppm), while the pseudo-Halbach configuration has the highest field strength ( 0.9B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> , 994 ppm), assuming perfect magnets. However, permanent magnet configurations suffer from imperfections, such as magnetization, fabrication, and positioning errors, which results in worse magnetic field homogeneities than expected from simulations using a fixed optimized parameter set. We present a sensitivity analysis for a magnetic cube and the results of studies of the variations in the magnetization and angle of magnetization of magnets purchased from different suppliers, composed of different materials and coatings, and of different sizes. We performed a detailed Monte Carlo simulation on the effect of the measured distribution of magnetic properties on the mentioned configurations. The cuboid design shows a mean homogeneity of 430 ppm (std. dev. 350 ppm), the Pseudo-Halbach has a mean homogeneity of 1086 ppm (std dev. 8 ppm).

The effect of an electric field on ion separation and water desalination using molecular dynamics simulations.

Using molecular dynamics simulations, we analyze ion separation and water purification through a piston-driven graphene/carbon-nanotube filter in the presence of an external electric field. Three different magnitudes of electric field are applied along the nanotube's axial direction with the goal of separating sodium and chloride ions in a NaCl aqueous solution. For comparison purposes, we also study the same system in zero fields. Our results show that sufficiently large values of the electric field strength greatly improve the ion separation process. At the highest field strength, the theoretical efficiency of the filter in removing salt from water exceeds 95% indicating its applicability in commercial filtration processes to produce fresh water. These results suggest that the proposed set-up can be used to design highly efficient nanostructured membranes for water desalination.

Triboelectric charging of dust particles during hand-held circular sawing of wood and wood-based materials

ABSTRACT During machining, wood particles are generated, released, and accelerated at high speed. Wood dust is known to be unpleasant, causing technical problems, but bears also considerable health risks. Wood dust consists of fractured tissues and has a high, irregularly structured surface due to tiny hooks formed by abundant sticking out fibrillar fragments. Targeting at a novel approach for dust reduction, this communication investigates triboelectric charging of wood particles upon cutting of wood samples using a hand-guided miter saw. The impact of wood species, number of saw blade teeth, cutting direction, and wood moisture, on electric field strength levels and polarity of generated wood particles were measured, using a electrostatic detection apparatus. The generated wood particles have shown accumulated triboelectric charging, as indicated by electric field strengths, which varied between −4 and +10 V m−1. The intensity of the charge transfer was inversely proportional to the moisture content, especially when cut cross-sectionally. Highest field strengths were observed for beech, cut perpendicular to grain. Even though being a highly undesired effect, triboelectric charging of wood bears a novel opportunity for reducing the current dust burden in home and industrial wood processing environments, which is subject of ongoing and future research.

4π-spherically focused electromagnetic wave: diffraction optics approach and high-power limits.

The focused field and its intensity distribution achieved by the 4π-spherical focusing scheme are investigated within the framework of diffraction optics. Generalized mathematical formulas describing the spatial distributions of the focused electric and magnetic fields are derived for the transverse magnetic and transverse electric mode electromagnetic waves with and without the orbital angular momentum attribute. The mathematical formula obtained shows no singularity in the field in the focal region and satisfies the finite field strength and electromagnetic energy conditions. The 4π-spherical focusing of the transverse magnetic mode electromagnetic wave provides the highest field strength at the focus and the peak intensity reaches 1026 W/cm2 for the laser power of 100 PW at 800 nm wavelength. As an example of using the mathematical formula, the electron-positron pair production via the Schwinger mechanism is analyzed and compared with previous results.

Competitive effects of modifier charge and size on mechanical and chemical resistance of aluminoborate glasses

Lithium aluminoborate glasses exhibit high resistance to cracking under contact loading, but low hardness and poor chemical durability in aqueous media. On the other hand, alkaline earth aluminoborate glasses feature improved chemical resistance and hardness, but lower resistance to cracking. In this work, we investigate the possibility to simultaneously improve the mechanical and chemical resistance of aluminoborate glasses by mixing alkali and alkaline earth modifiers. We study the mixed Li/Ba and Li/Mg aluminoborate glasses, since Li+ and Ba2+ have different charge and size but similar modifier field strength (charge to size ratio), while Mg2+ has the highest field strength among these modifiers due to its small size. The two glass series will thus give insights into the competitive effects of modifier charge and size on glass structure, mechanical properties, and dissolution rates in acidic, neutral, and basic solutions. The substitution of barium for lithium at fixed [Al2O3]/[B2O3] ratio does not affect the network structure and properties, such as hardness and dissolution rate. However, the substitution of magnesium for lithium leads to an increase in hardness and chemical durability for all pH solutions (2, 7, and 14), likely as a result of the increase in the fractions of five- and six-fold coordinated aluminum species and atomic packing density. The glass with 5 mol% Li2O and 20 mol% MgO exhibits the best combination of high hardness and low dissolution rate, while maintaining a good crack-resistance comparable to that of the Li-aluminoborate glass. In both mixed glass series, the lowest dissolution rates are measured in neutral solutions, while those in acidic and especially basic media are higher. The structural origins of the trends in chemical and mechanical properties are discussed based on 11B and 27Al nuclear magnetic resonance (NMR) spectroscopy measurements.

Abstract 3722: Efficacy of irreversible electroporation in combination with liposome-nvp-bez235 for head and neck cancer

Abstract Introduction: Irreversible electroporation (IRE) is an emerging, minimally invasive ablation technique with the advantage of not being affected by heat sink effect and the ability of ablation in close vicinity of major blood vessels. One limitation is local recurrence at the original ablated site. We hypothesize that combining IRE with a chemotherapeutic drug could prevent recurrence. NVP-BEZ235 (BEZ) is a dual PI3K/mTOR inhibitor that has shown promise for treating advanced solid malignancies, including sensitizing head and neck squamous cell carcinoma to radiotherapy. However, clinical trials revealed low bioavailability and high toxicity due to high dose oral administration over a long period of time. Thus, we formulated a liposomal BEZ (L-BEZ) and studied its antitumor effect in combination with IRE and compared the results with orally delivered BEZ (oral-BEZ). Methods: IRE was performed using ECM 830 (BTX Harvard Apparatus) at various field strengths. BEZ was loaded into liposome (L-BEZ) by hydration-sonication method. The in vitro and in vivo efficacy was tested against head and neck cancer cell line, HN5 cells and in nude mice bearing HN5 xenografts (n=4/group). Mice were divided into control (no treatment), IRE (2500 V/cm for 99 pulses), IRE + L-BEZ (IRE at 2500 V/cm for 99 pulses and 7 doses of L-BEZ) and IRE + oral-BEZ (IRE at 2500 V/cm for 99 pulses and 21 doses of oral-BEZ) groups. Tumor size was monitored for 60 days. Results: The hydrodynamic volume of NVP-BEZ ranged from 100-500nm. Maximum drug loading was achieved at 2.7mg/mL of BEZ. Electroporation disrupted nanoparticle's integrity even at the lowest tested field strength (250 V/cm) and released BEZ. At the highest field strength (2500 V/cm), approximately 5% of cells survived with IRE, while cells electroporated at 500 V/cm increased cell viability (114%) as compared to the untreated group (100 %). Combination of electroporation and L-BEZ significantly decreased cell viability at 500 V/cm (p&amp;lt;0.05). In vivo, IRE + L-BEZ suppressed tumor growth the longest, as compared with control (no treatment), IRE, and IRE + oral-BEZ. It was also the only group that resulted in no palpable tumor from day 30 to day 60. Survival studies show a significant difference between IRE + L-BEZ and the other groups. IRE + L-BEZ group had 100% animal survival on day 60. IRE + oral-BEZ had 50%, while IRE and control groups had 0% animal survival, on day 60. Also, the total administered BEZ amount in IRE + L-BEZ group was only 6.6% of that in IRE + oral-BEZ group. Conclusion: Incomplete electroporation increases the viability of surviving cells both in vitro and in vivo. Co-delivery of L-BEZ enhances the antitumor efficacy of IRE alone. L-BEZ also decreases BEZ exposure compared to oral-BEZ. Thus, L-BEZ in combination with IRE potentially ensures complete eradication of surviving cells left after IRE. Citation Format: Li Tian, Lucas Wang, Yang Qiao, Saisree Ravi, Ashley Chang, Thomas Alexander Rogers, Linfeng Lu, Adam D. Melancon, Marites Pasuelo Melancon. Efficacy of irreversible electroporation in combination with liposome-nvp-bez235 for head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3722.

Low-Field Cardiac Magnetic Resonance Imaging: A Compelling Case for Cardiac Magnetic Resonance's Future.

Cardiac magnetic resonance (CMR) is arguably unmatched in its ability to evaluate cardiovascular structure and function, to characterize myocardial tissue by a wide variety of mechanisms, and to quantitatively assess blood flow and perfusion without the use of radiation or the need for invasive catheterization. CMR research and development continues at a rapid pace both in academia and by commercial vendors, and every year, new techniques are put forth that improve on existing applications and provide new capabilities that further expand the clinical utility of this powerful modality. Real-time and single-shot techniques have made CMR feasible in patients with rhythm irregularities and inability to breath-hold. Ongoing development and regulatory approval of magnetic resonance imaging (MRI) conditional pacemakers and implanted cardioverter defibrillators continues to grow the patient population amenable to CMR. Larger clinical trials are coming out that support the clinical value of CMR.1–3 Despite the advances in CMR technology over the past decades, the growing data supporting its effectiveness, and the increasing availability of both CMR-capable scanners and practitioners, the penetration of CMR into routine diagnostic cardiovascular imaging remains limited. It is clear that those involved in CMR research must not only engage in developing new and exciting applications made feasible by technological advances, but must also ask whether their technology will promote the routine clinical utilization of CMR beyond academic and isolated private centers. There are many factors at play in answering this question, but important considerations must be affordability and ease of use. A CMR system is one of the most expensive devices in the hospital, and the cost of the system scales with field strength. Prior to 2001, the highest field strength available for clinical MRI was 1.5T; however, recent years have witnessed an expanded utilization of 3T MRI that has been driven mainly …

Superconducting magnets for the RAON electron cyclotron resonance ion source

The RAON linear accelerator of Rare Isotope Science Project has been developed since 2011, and the superconducting magnet for ECRIS was designed. The RAON ECR ion source was considered as a 3rd generation source. The fully superconducting magnet has been designed for operating using 28 GHz radio frequency. The RAON ECRIS operates in a minimum B field configuration which means that a magnetic sextupole field for radial confinement is superimposed with a magnetic mirror field for axial confinement. The highest field strength reaches 3.5 T on axis and 2 T at the plasma chamber wall for operating frequency up to 28 GHz. In this paper, the design results are presented of optimized superconducting magnet consisting of four solenoids and sextupole. The prototype magnet for ECRIS was fabricated and tested to verify the feasibility of the design. On the basis of test results, a fully superconducting magnet will be fabricated and tested.

OP 11. Optimized tDCS electrode configurations for five targets determined via an inverse FE modeling approach

Introduction Transcranial direct current stimulation (tDCS) has shown potential in improving brain function in both healthy subjects and patients suffering from a wide range of neuropathologies. Unfortunately, the effects are too small and short-lived for tDCS to be used as a clinical therapy. Increasing the effect size of tDCS could possibly be achieved by better targeting the current, both in direction and amplitude. Volume conduction modeling has shown that the areas with the highest electric fields strengths do not, as is often assumed, lie beneath the electrodes (Datta et al., 2009). Attempts at optimization have been published for point and ring electrodes (Im et al., 2008; Dmochowski et al., 2011), but not for the square patches used in most labs. In order to find for these electrodes, configurations that do result in maximum stimulation at the target area, we propose an inverse modeling approach. Objectives We simulate tDCS for ∼7000 configurations and determine which of these lead to optimal electric fields, both in strength and direction, at the five most target locations in tDCS research: motor cortex (M1), dorsolateral prefrontal cortex, inferior frontal gyrus, occipital cortex and cerebellum. Methods A detailed finite element (FE) head model was made by automatic segmentation of MR images aided by manual corrections. The model contains over 4 million elements and 11 tissue types. Special attention was given to the skull, the main barrier for the tDCS current, by including the spongiosa layer and skull holes. Brain anisotropy was derived from DTI measurements. On the skin surface, a grid of 89 points was placed consisting of the standard 10–10 EEG system and extra points on the cheeks and neck. For each combination of 2 points, we placed 5×5cm electrode patches onto the model, centred on the two points, and simulated 1mA tDCS. At each target, we placed a cylindrical volume in the brain and selected the configurations leading to highest mean field strength or optimal direction in the target volume. Results For all targets, the optimized configurations did not include the commonly used configurations. Often, highest field strengths were found in configurations that are near-perpendicular to the standard configurations. Optimization based on either strength or direction of the field lead to completely different configurations. Conclusion The optimized configurations found in this study suggest that improved results of tDCS can be expected. We found different optimized configurations by looking at either strength or direction of the field. Comparing these optimized configurations experimentally will not only verify our modeling approach, but also provide valuable information on the mechanisms behind tDCS. This approach can be used to optimize stimulation for any target location.

INVESTIGATION OF INFLUENCE OF SURFACE NANOPARTICLE ON EMISSION PROPERTIES OF SCANDIA-DOPED DISPENSER CATHODES

The microstructure of a fully activated scandia doped dispenser (SDD) cathode has been studied by scanning electron microscope (SEM). The observation results display that nanoparticles appear at the growth steps and the surface of tungsten grains of the fully activated SDD cathode. To study the influence of the nanoparticles on the emission, the local electric field strengths around the nanoparticles have been calculated by Maxwell 2D code and Comsol. The calculation results show that the local electric field strengths are enhanced by 1.1 to 3.8 times to average value based on different model conditions. The highest field strength is about 1.54 × 105 V/cm at an average field strength of 40 KV/cm, which is related to a space-charge limited (SCL) current density of 100 A/cm2 in the experimental configuration. This implies the field strength is not high enough to cause field emission.

Semiconductor quantum well excitons in strong, narrowband terahertz fields

Optical transitions between exciton states in semiconductors—intraexcitonic transitions—usually fall into the terahertz (THz) range and can be resonantly excited with narrowband, intense THz radiation as provided by a free-electron laser. We investigate this situation for two different quantum well structures by probing the near-infrared excitonic absorption spectrum near the band edge. We observe the dynamical Stark—or Autler–Townes—splitting of the 1s exciton ground state and follow its evolution for various THz photon energies and field strengths. The behavior is considerably more complex as compared to the atomic systems. At the highest field strengths, where the Rabi energy is of the same order of magnitude as the exciton level separation, the system cannot be described within the standard framework of a two-level system in rotating wave approximation. When the ponderomotive energy approaches the exciton binding energy, signatures of exciton field ionization are observed.

A charge-driven molecular flip-flop

Using molecular dynamics simulations, we exploit a charge-driven flip-flop that is composed several water molecules confined in a single-walled carbon nanotube. The flip-flop has two stable states and can be used to store state information. It can toggle between the two states within 2.5–3.5 ps (286 GHz–400 GHz). We reveal that the underlying mechanism is dominated by the interaction between the water molecules and nonuniform electric field generated by point charges. Namely, each water molecule tends to maintain its lowest electric energy by moving toward the location with the highest field strength. This flip-flop may be of value for molecular computing.

Magnetic Resonance Compatibility of Intraocular Lenses Measured at 7 Tesla

To determine whether intraocular lenses (IOLs) are compatible with magnetic resonance imaging (MRI) at a magnetic field strength of 7 Tesla, the highest field strength at which clinical MRI scans are performed. A set of 23 intraocular lenses was selected based on the presence of dyes and metals and different geometric shapes. MR compatibility was evaluated in a high-field 7-Tesla MRI scanner according to the American Standard Test Method (ASTM). The magnetically induced displacement was measured via the angular deflection method. The degree of magnetic susceptibility artifact formation was evaluated by positioning the IOLs in a phantom gel for scanning, using a three-dimensional gradient echo (GRE) sequence. All images were visually inspected to determine the spatial extent of any signal voids. Fiber-optic temperature probes were deployed to measure radio-frequency (RF) heating using a GRE sequence with powers 10 times higher than clinical settings. No significant displacement was detected with any of the tested IOLs. A significant magnetic susceptibility artifact was caused by the small platinum component of the Worst Platinum Clip IOL. None of the other 22 IOLs caused measurable susceptibility artifacts. Measurements on RF-induced heating showed no significant temperature rise (<0.25°C) of the tested IOLs. MRI did not induce movement or RF heating of any of the IOLs. We conclude that all the tested intraocular lenses are considered safe for MRI up to and including 7 Tesla. One IOL, the Worst Platinum Clip IOL, caused a significant imaging artifact.

Alignment of carbon nanotubes in polyimide under electric and magnetic fields

AbstractUsually alignment of carbon nanotubes (CNT) in polymer composites can be induced by a single electrical or magnetic field. Here we report a comparison between the results of simultaneous application of both fields to the polyimide composite and a single field. Alignment of CNT in polyimide was performed under a 2 Tesla magnetic field and various electric fields (150, 300, 450, and 600 V/cm). Polarized Raman spectroscopy was used for assessing the degree of alignment of the nanotubes in the composites and many details of the alignment were examined. The results indicated that at the same electric field strength, incorporation of a magnetic field in a given direction will enhance the level of alignment as compared with only using an electric or magnetic field alone. The best alignment condition was for the CNT samples under parallel magnetic and electric fields. Optical microscopy observations also indicated that nanotube alignment appeared at the highest field strength and decreased when the field strength decreased. A possible mechanism for field alignment is presented. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012