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Purpose: This article summarizes the short lecture on gantries given at the "Hadrontherapy: status and perspectives. Development of a hadrontherapy facility: learning from the existing" event. Methods and materials: An introduction to gantries is given describing what a gantry is and which are the main difficulties and choices for an ion gantry. The gantry design activities ongoing at CNAO are shortly described. Results: The first part of the lecture and of the article describes some of the main choices to be made when designing a carbon ion gantry. The second part of the lecture reports shortly about the activities ongoing at CNAO within the HITRIplus and the EuroSIG projects. Conclusions: Carbon ion gantries are large, complicated and expensive objects and presently only three gantries for carbon are operational worldwide. The design of a gantry can be optimized in many ways and in many respects. In the paper, without the ambition of being exhaustive, some of the main choices are illustrated and the pros and cons of the possible options are discussed. Finally the gantry design activities ongoing in the EuroSIG collaboration and in the HITRIplus project are shortly reported. [ABSTRACT FROM AUTHOR]

Precast segmental construction can shorten the construction time of the bridge and reduce the impacts on traffic and environment. Thus, this approach has been widely used in many countries. The relevant literature suggests that in the existing segmental precast bridges, nearly all of the centerlines of the girders are aligned with the centerline of the bridge piers. This paper introduces a wide urban viaduct comprising twin separate box girder cells using segmental prefabrication. To save space under the bridge, the bridge has only one row of piers and long cantilever crossbeams are set at the top of each pier. Additionally, the centerline of the girder and the centerline of the pier do not overlap. To prevent eccentric loading and improve the construction speed, two bridge erection gantries are used for synchronous construction. This study is a pioneering attempt at bridge construction with a precast segmental twin‐deck box girder bridge simultaneously erected with double gantries. To investigate the stress state of the whole system (crossbeam, gantries, and box girder segments) during construction and demonstrate the feasibility of the construction method, a real bridge was used. The test results provide a reference for the design and construction of similar projects. [ABSTRACT FROM AUTHOR]

Simple Summary: Carbon ion radiotherapy (CIRT) facilities are proliferating throughout Asia and Europe. They are costly to build, operate and maintain. Rotating gantries can deliver individualized treatments to patients with CIRT-eligible malignancies due to the increased number of choices of beam angles for treatment delivery. They help to minimize compromises in the treatment planning process, optimizing local tumor control and reducing the risk for acute and late adverse events, but they are expensive. Our aim is to retrospectively report the number and range of beam angles utilized to deliver proton therapy with a rotating gantry to a wide variety of patients with CIRT-eligible malignancies and to determine the proportion of tumor sites treated with unimodal, bimodal and multimodal groupings of beam angles. We found that only esophagus and pancreas cancers were treated with unimodal or bimodal beam groupings. Rotating gantries provide individualized beam arrangements for most CIRT-eligible patients. Purpose: This study evaluates beam angles used to generate highly individualized proton therapy treatment plans for patients eligible for carbon ion radiotherapy (CIRT). Methods and Materials: We retrospectively evaluated patients treated with pencil beam scanning intensity modulated proton therapy from 2015 to 2020 who had indications for CIRT. Patients were treated with a 190° rotating gantry with a robotic patient positioning system. Treatment plans were individualized to provide maximal prescription dose delivery to the tumor target volume while sparing organs at risk. The utilized beam angles were grouped, and anatomic sites with at least 10 different beam angles were sorted into histograms. Results: A total of 467 patients with 484 plans and 1196 unique beam angles were evaluated and characterized by anatomic treatment site and the number of beam angles utilized. The most common beam angles used were 0° and 180°. A wide range of beam angles were used in treating almost all anatomic sites. Only esophageal cancers had a predominantly unimodal grouping of beam angles. Pancreas cancers showed a modest grouping of beam angles. Conclusions: The wide distribution of beam angles used to treat CIRT-eligible patients suggests that a rotating gantry is optimal to provide highly individualized beam arrangements. [ABSTRACT FROM AUTHOR]

Variable speed limits (VSL) aim at improving safety and traffic fluidity by increasing drivers' awareness. In the present simulator study, VSL displayed on overhead gantries on a motorway were also displayed on a mobile phone, fixed on the vehicle's centre console, with distance-based triggers (250 m vs. 500 m from the overhead gantry). Results showed drivers (N = 20) complied with the in-vehicle information, which was congruent with the upcoming gantry. The sooner the in-vehicle VSL, the faster the speed when speed limits increased. Similarly, the sooner the in-vehicle VSL, the slower the speed when speed limits decreased. Later in-vehicle VSL resulted in lower speed homogeneity, which is a safety concern. Speed homogeneity was greater when no in-vehicle VSL were displayed. Finally, the 70 mph VSL were affecting driving behaviour differently. These results suggested that there might be traffic disruption and more erratic longitudinal vehicle control on real roads. [ABSTRACT FROM AUTHOR]

Superconductors enable extremely high field magnets that can be used to develop compact heavy-ion rotating gantries and accelerators. To achieve high fields, a large quantity of superconducting material is required. This results in high costs and difficulties on cooling. An effective design algorithm is necessary to optimize the magnet designs and reduce materials needed. In this article, we propose a new design method for high temperature superconducting (HTS) magnets with combined function for carbon-ion therapy rotating gantries. The new method applies a layer-by-layer design process, which effectively reduces the total volume of superconducting material required and improves field precision. First, the cross section of a multilayer magnet was designed to achieve combined fields of dipole and quadrupole. Based on this, 3-D magnet coil ends were designed, considering mechanical constraints of the HTS coated conductors. Results show that the new design requires 26.3% less material than the existing design with a highly precise field strength and distribution. [ABSTRACT FROM AUTHOR]

During the shipbuilding processes carried out in the shipyards, there is a need to transport the sections of ship structure, from the place where they are built to the assembly location. When the shape and structure of the sections allow, they are built in an inverted position, and after finishing all the works that can be performed in this type of placement, the section will have to be turned to continue the section building process and subsequent the assembly. Loads that appear in the structure during these maneuvers are different from those that appear during the operation and from those for which calculations were made at the stage of the initial project. Therefore, it is necessary to calculate them and design a lifting / turning installation, which should also contain stiffening elements where required, in order to prevent both accidents and deformations or detachments that could occur at the section level. From this necessity appears the plan generically called "lifting plan" and which contains the installations, the schemes, the necessary instructions to remove the units from the section building hall, turn it to the gantry cranes and brought into the mounting position. [ABSTRACT FROM AUTHOR]

Mayo Clinic Florida will initially open with the capability to treat with a single horizontal port for carbon ion therapy. Carbon ion therapy is traditionally done using a multi fixed port treatment approach. In this study, for nine treatment sites, clinically approved treatment plan of Osaka Heavy Ion Therapy Center was compared to a treatment plan using only a horizontal port. The treatment sites evaluated in this study were prostate cancer, pancreatic cancer, cervical cancer, recurrent rectal cancer, liver cancer, head and neck cancer, bone cancer (sarcoma and chordoma), and lung cancer. As expected, the prostate plans are identical and are only included for completeness. The DVH results for the pancreas and cervical cancer were very similar. The results for recurrent rectal, head and neck, sarcoma, chordoma, and lung cancer indicate that a single horizontal port with couch roll and yaw will accommodate certain medial targets but will be challenging to treat for laterally located targets without creative mitigations., Competing Interests: Conflicts of Interest The authors declare no conflicts of interest to disclose., (Copyright © 2024 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.)

Particle therapy is rapidly expanding and claiming its position as the treatment modality of choice in teletherapy. However, the rate of expansion continues to be restricted by the size and cost of the associated particle therapy systems and their operation. Additional technical limitations such as dose delivery rate, treatment process efficiency, and achievement of superior dose conformity potentially hinder the complete fulfillment of the promise of particle therapy. These topics are explored in this review considering the current state of particle therapy systems and what improvements are required to overcome the current challenges. Beam production systems (accelerators), beam transport systems including gantries and beam delivery systems are addressed explicitly in these regards. [ABSTRACT FROM AUTHOR]

In this paper, the performance of a typical composite work cell structure that includes multiple machines and a material handling gantry is studied. A mathematic model is established to analyze the performance of such gantry systems. Due to the unique features of the gantry system, cycle time and waiting time of the gantry and machines are discussed and formulated based on two basic scenarios. To measure the impact of disruption events, permanent production loss is evaluated by using the sensor data collected from plant floors. Data-driven diagnostic methods are developed to identify the bottleneck machine and to evaluate permanent production loss attribution of each machine. The results provide a solid base to efficiently and effectively improve the performance of a composite work system. Performance diagnostics of gantry systems provides a theoretical and practical basis for production improvement. A gantry system for composite lay-up processes is used for numerical simulation case studies, by which the performance diagnostic methodologies and improvements are demonstrated. Note to Practitioners—Accurate performance diagnostics and effective improvement methods are critical to manufacturing operation and management. Most existing efforts are devoted to analyzing the performance of a whole production line rather than considering the complexity of each station/work cell in the line. This paper zooms into a composite work cell with a material handling gantry and focuses on the performance diagnostics of the lay-up station in a composite work center. The methods presented in this paper can be extended and applied to other manufacturing work cells comprising the similar gantry structure. We build a mathematical model to analyze the characteristics of the gantry system such as gantry cycle and waiting time. The evaluation of system production loss, which directly adopts sensor data from the factory floors, provides a quantitative tool for production engineers to monitor and control the system in real-time operation. In addition, the performance diagnostic methods based on production loss attribution and bottleneck identification are developed to guide the decision makers to improve the production system under different resource conditions. The methods are developed based on a work cell with only one gantry under a fixed gantry moving sequence. In the future research, we will extend the study to the systems with more gantries and more complex gantry moving policies. [ABSTRACT FROM AUTHOR]

Guideway-induced errors are the main factors affecting the machining accuracy in computer numerical control (CNC) machine tools. In this paper, the guideway-induced errors of a large CNC gantry guideway grinder are analyzed and measured to realize the traceability analysis and coupling compensation. To establish the error model, an automatic error modeling application is developed based on the least-square fitting of orthogonal polynomial method and visual basic. The comprehensive error model of the grinder is established using the homogenous transformation matrix to realize the error distribution analysis in a three-dimensional workspace. The error separation method is used to achieve the traceability analysis of the guideway-induced errors. To realize the coupling compensation for guideway-induced errors, an external mechanical origin offset (EMOO) and Ethernet-based error compensation method are proposed in this research. Experimental results showed that the maximum error was compensated by 91.2 % compared with no compensation. [ABSTRACT FROM AUTHOR]

Particle therapy is a field in remarkable development, with the goal of increasing the number of indications which could benefit from such treatments and the access to the therapy. The therapeutic usage of a particle beam defines the technical requirements of all the elements of the therapy chain: we summarize the main characteristics of accelerators, the beam line, the treatment room, the integrated therapy and imaging systems used in particle therapy. Aiming at a higher flexibility in the choice of treatments, an increasing number of centers around the world have chosen to equip their treatment rooms with gantries, rotating beam line structures that allow a complete flexibility in the choice of the treatment angle. We review the current designs. A particle therapy gantry though is a quite expensive structure, and future development will increasingly consider reducing the cost and the footprint. Increasing the number of indications also means development in the delivery techniques and solving some of the issues which traditionally affected particle therapy, for example the precision of the delivery in presence of motion and the large penumbras for low depths. We show the current strategies in these fields, focusing on pencil beam scanning (PBS), and give some hints about future developments. [ABSTRACT FROM AUTHOR]

This study comparatively analysed dose distributions between the fixed and rotating gantry positions of volumetric-modulated arc therapy (VMAT) plans measured using different dosimetric techniques with the intent to provide pretreatment quality assurance (QA). A total of 12 VMAT plans for the treatment of anatomical sites of various complexities were chosen. An ion chamber was used to measure the absolute central point doses,while EPID, Seven29, Matrixx and Delta4 were used to measure the dose distributions. With the exception of Delta4, all detectors were used in one of two different settings: the gantry was either fixed at 0°, or the gantry was rotating. The results were analysed using the Υ -evaluation method. Regarding absolute central point doses, the ion chamber results were within 3% of the treatment planning system (TPS) calculated results. For the dose distributions measured by detectors and calculated by TPS, the Υ pass rates, with 3% maximum dose and 3 mm Υ criteria, were above 96% when the gantry was fixed at 0°. When the gantry was rotating, the pass rates decreased slightly but were still above 90%. The results obtained from the comparison between the measured and calculated doses demonstrated the reliability of four detectors associated with VMAT. However, the treatment delivery and detector response may impact the results when the gantry is rotating. [ABSTRACT FROM AUTHOR]

Abstract: Intensity Modulated Radiation Therapy (IMRT) is a complex treatment modality that requires pre-treatment patient-specific quality control (QC) in order to assess a correct treatment delivery. The aim of this work is to investigate pre-treatment patient-specific per-field QCs performed with an on-board EPID at the gantry angle of 0° and at the treatment ones, and to asses if measurements executed at 0° are able to guarantee a correct treatment. Ten patients with prostate cancer were evaluated. Two “verification” plans were created for each patient in order to calculate the dose at the EPID surface: one with all fields positioned at 0° and one with all fields at the actual treatment angles. EPID’s mechanical shifts due to gravity effects were always taken into account and corrected. 0 and no-0 plans were compared using a gamma-index method (3%, 3 mm). The gamma index was found dependent on gantry angles but the difference between 0 and no-0 samples was small (−0.3% mean value) and the criteria of acceptability of the gamma method was always satisfied for every field delivered at angles different from 0. Therefore patient-specific pre-treatment QCs should be done at treatments angles, but, if periodical quality assurance is performed on dynamic MLC for different gantry angles, this requirement was shown not strictly mandatory and pre-treatment IMRTQC can be reasonably executed at 0° angles too. [Copyright &y& Elsevier]

We propose amethod to incorporate independent verification of gantry angle for electronic portal imaging device (EPID)-based pre-treatment quality assurance (QA) of clinical volumetric modulated arc therapy (VMAT) plans. Gantry angle is measured using projections in the EPID of a custom phantom placed on the couch and the treatment plan is modified so as to be incident on the phantom with a portion of the beam that is collimated in the clinical plan. For our implementation, collimator and couch angles were set to zero and the inferior jaw and two most inferior multi-leaf collimator pairs were opened for the entire QA delivery. A phantom containing five gold coils was used to measure the gantry rotation through which each portal image was acquired. We performed the EPID QA for ten clinical plans and evaluated accuracy of gantry angle measurement, scatter incident on the imager due to the phantom, inter-image pixel linearity and inter- and intra-image noise. The gantry angle could be measured to within 0.0 ± 0.3° for static gantry and 0.2 ± 0.2° for arc acquisitions. Scatter due to the presence of the phantom was negligible. The procedure was shown to be feasible and adds gantry angle to the treatment planning parameters that can be verified by EPID-based pre-treatment VMAT QA. [ABSTRACT FROM AUTHOR]

Major roads can reduce bat abundance and diversity over considerable distances. To mitigate against these effects and comply with environmental law, many European countries install bridges, gantries or underpasses to make roads permeable and safer to cross. However, through lack of appropriate monitoring, there is little evidence to support their effectiveness. Three underpasses and four bat gantries were investigated in northern England. Echolocation call recordings and observations were used to determine the number of bats using underpasses in preference to crossing the road above, and the height at which bats crossed. At gantries, proximity to the gantry and height of crossing bats were measured. Data were compared to those from adjacent, severed commuting routes that had no crossing structure. At one underpass 96% of bats flew through it in preference to crossing the road. This underpass was located on a pre-construction commuting route that allowed bats to pass without changing flight height or direction. At two underpasses attempts to divert bats from their original commuting routes were unsuccessful and bats crossed the road at the height of passing vehicles. Underpasses have the potential to allow bats to cross roads safely if built on pre-construction commuting routes. Bat gantries were ineffective and used by a very small proportion of bats, even up to nine years after construction. Most bats near gantries crossed roads along severed, pre-construction commuting routes at heights that put them in the path of vehicles. Crossing height was strongly correlated with verge height, suggesting that elevated verges may have some value in mitigation, but increased flight height may be at the cost of reduced permeability. Green bridges should be explored as an alternative form of mitigation. Robust monitoring is essential to assess objectively the case for mitigation and to ensure effective mitigation. [ABSTRACT FROM AUTHOR]

A conceptual design of curved superconducting magnet for a carbon therapy gantry has been proposed. The design can reduce the gantry's size and weight and make it more comparable with gantries used for proton therapy. In this paper we report on a combined function, 5 T, superconducting dipole magnet with a 260 mm bore diameter that is curved 90 degrees at a radius of 1269 mm. The magnet superimposes two layers of oppositely wound and skewed solenoids like windings, energized in a way that nulls the solenoid field and doubles the dipole field component. Furthermore, the combined architecture of the windings can create a selection of field terms that are off the near-pure dipole field. Combined harmonics such as a quadrupole and sextupole are needed to adjust the beam trajectory. Ways to adjust the field and beam trajectory, magnet size and assembly, structure and pre-stress are considered. [ABSTRACT FROM PUBLISHER]

As mechanical stability of radiation therapy treatment devices has gone beyond sub-millimeter levels, there is a rising demand for simple yet highly accurate measurement techniques to support the routine quality control of these devices. A combination of using high-resolution radiosensitive film and computeraided analysis could provide an answer. One generally known technique is the acquisition of star shot films to determine the mechanical stability of rotations of gantries and the therapeutic beam. With computer-aided analysis, mechanical performance can be quantified as a radiation isocenter radius size. In this work, computer-aided analysis of star shot film is further refined by applying an analytical solution for the smallest intersecting circle problem, in contrast to the gradient optimization approaches used until today. An algorithm is presented and subjected to a performance test using two different types of radiosensitive film, the Kodak EDR2 radiographic film and the ISP EBT2 radiochromic film. Artificial star shots with a priori known radiation isocenter size are used to determine the systematic errors introduced by the digitization of the film and the computer analysis. The estimated uncertainty on the isocenter size measurement with the presented technique was 0.04 mm (2σ) and 0.06 mm (2σ) for radiographic and radiochromic films, respectively. As an application of the technique, a study was conducted to compare the mechanical stability of O-ring gantry systems with C-arm-based gantries. In total ten systems of five different institutions were included in this study and star shots were acquired for gantry, collimator, ring, couch rotations and gantry wobble. It was not possible to draw general conclusions about differences in mechanical performance between O-ring and C-arm gantry systems, mainly due to differences in the beam-MLC alignment procedure accuracy. Nevertheless, the best performing O-ring system in this study, a BrainLab/MHI Vero system, and the best performing C-arm system, a Varian Truebeam system, showed comparable mechanical performance: gantry isocenter radius of 0.12 and 0.09 mm, respectively, ring/couch rotation of below 0.10 mm for both systems and a wobble of 0.06 and 0.18 mm, respectively. The methodology described in this work can be used to monitor mechanical performance constancy of high-accuracy treatment devices, with means available in a clinical radiation therapy environment [ABSTRACT FROM AUTHOR]

The article reports on overhead and under-slung gantries used for span by span construction of precast segmental bridge decks. It mentions that the decks are the most common structural systems applied for precast segmental viaducts. It notes that the gantries' performance standard and configuration are directly affected by a method wherein segments are joined and activated to self-supporting spans. It also justifies the features of the frameworks and compares their application ranges.

The article reports in the application of gantry machines in pre-cast segmental balanced cantilever bridges. It discusses their generic forms along with the impact they have on permanent structure and design of the bridge. It highlights their components with consideration of their effect on cost and productivity. It describes the advantages of expenditure, quality and programmes of their utilization. It also points the benefits of separating their design from supply.

Purpose - The purpose of this paper is to review the latest developments, both in terms of products and manufacturing, of the Festo company. Design/methodology/approach - This paper is a result of a visit made to Festo and also the Motek show in 2010. Findings - Festo is developing new products which will not only enable new applications for automation, but also challenge the traditional approach of applying standard robots or gantries. Originality/value - The paper provides an overview of the latest Festo developments highlighting their importance. [ABSTRACT FROM AUTHOR]

The Centro Nazionale di Adroterapia Oncologica (National Center for Oncological Hadrantherapy, CNAO) will be the first Italian center for deep hadrontherapy. It is presently under construction in Pavia. It will be based on an evolution of the PIMMS synchrotron capable to accelerate carbon ions up to 400 MeV/u kinetic energy and protons up to 250 MeV, energies which are necessary to treat deep seated tumors. Four treatment lines, in three treatment rooms, and a dedicated facility for clinical and radiobiological researches are foreseen in a first stage. Space for two additional rooms eventually equipped with gantries has been left aside the center and the synchrotron has been designed to work with these two additional lines, but they are intended as a future upgrade. The beam is injected into the synchrotron from the inside, to allow positioning all the injection chain inside the synchrotron ring itself, and also to better exploit the two nondispersive regions in the synchrotron. The injection chain is made by a 8 keV/u Low Energy Beam Transfer line (LEBT), a RFQ accelerating the beam to 400 keV/u, a LINAC to reach the injection energy of 7 MeV/u and a Medium Energy Beam Transfer line (MEBT) to transport the beam to the synchrotron. This report describes the design and the performances of the CNAO, and reports about the status of the construction of the center. [ABSTRACT FROM AUTHOR]

High-precision operation in gantry systems is required to meet higher demands on positioning accuracy in a wide range of applications such as circuit assembly, precision metrology, and wafer stepping. In this paper, the experimental study of an observer-augmented composite control scheme for coordinated motion control of moving gantry stages for precision applications is presented. The scheme will be implemented and compared to other control schemes currently available for this purpose, including a master-slave and a set-point coordinated scheme. Experimental results will illustrate the enhanced performance of the fully coordinated control scheme with respect to fight trajectory tracking purposes. [ABSTRACT FROM AUTHOR]

OBJECTIVES:: In a multiplanar reconstruction CT program (CT/MPR), the altered gantry angle corresponding to the patient's position during scanning for multiplanar reformatted CT may cause distortion of the image. The aim of this study was to quantitatively assess the distortion in reformatted central panoramic and cross-sectional images owing to the change of gantry angle. METHODS:: A resin block model with four cylindrical holes and a human dry mandible were used in high resolution conventional CT scanning. A MPR software package was used for reformatted panoramic and cross-sectional images. The block and the gantry were equally inclined at 0°, 15° and 30°. The relationship between the positional difference and depth of the hole as determined in the reformatted image, and the actual depth was analysed with respect to the gantry angle. The actual depths (H) were calculated by use of the measured depths (h) and the inclined angles: H=h×cos β. The positional differences of the hole bases (W) were also calculated by use of the measured depths and the inclined angles: W=h×sin β or H×tan β. RESULTS:: Increasing the gantry angle, increased the depth and inclination of the holes in the reformatted central panoramic images. Inclined angle (β) was the same as gantry angle. CONCLUSION:: When the gantry angle is not at 0°, certain CT/MPR programs may distort the reformatted image. If distortion occurs, the corrected position and usable length of pre-implant sites can be calculated by use of the above formula.Dentomaxillofacial Radiology (2002) 31, 273–277 doi:10.1038/sj.dmfr.4600702 [ABSTRACT FROM AUTHOR]

Isocenter calibration transforms cardiac structures in digitized biplane angiograms to absolute dimensions, calculating their radiological magnification and video transformation. Since a scaling device is not required, isocenter calibration yields to more accurate measurements than the widely used reference object calibration. Both isocenter methods reported so far, regarding geometrically inaccurate x-ray gantries, yield to different and complex computational formulas. Since these formulas are hard to understand, isocenter calibration is less widely used. To facilitate the implementation of the isocenter calibration, the basic formulas for accurate x-ray gantries are derived. Shifting virtually one x-ray system onto the other, basic isocenter calibration is derived geometrically in three simple steps. The radiological magnification of an object is illustrated as a ratio of planes. The calculation of all parameters entering the computations is demonstrated geometrically, by use of the isocenter of the x-ray gantry. The derivation gives a clear idea of isocenter calibration. It is simple to derive and facilitates the understanding of the error regarding developments. When geometrical inaccuracies vanish, all formulas become equivalent. However, even if the inaccuracies increase, all methods provide nearly identical results, indicating the robustness of isocenter calibration. [ABSTRACT FROM AUTHOR]

At the Paul Scherrer Institute (PSI/Switzerland) a new proton gantry for cancer treatment is planned. A fast 3 dimensional scanning technique of the tumor volume is one of the medical highlights of this new gantry. The gantry will be driven by the new COMET proton cyclotron, which will deliver a cw proton beam. The energy of this beam will be adjusted by a fast degrader device. All beam line magnets should follow the energy changes of the degrader as fast as possible. Therefore the eddy current effects in the laminated bending magnets of the beam line and the gantry must be reduced by an appropriate magnet design. The paper shows measurements and numerical simulation of the dynamic behavior of the fast switched bending magnets and design schemes for eddy current reduction in the bending magnets. [ABSTRACT FROM AUTHOR]