Steady state magnetic sensors for ITER and beyond: Development and final design (invited).

The measurements of the magnetic field in tokamaks such as ITER and DEMO will be challenging due to the long pulse duration, high neutron flux, and elevated temperatures. The long duration of the plasma pulse makes standard techniques, such as inductive coils, prone to errors. At the same time, the hostile environment, with repairs possible only on blanket exchange, if at all, requires a robust magnetic sensor. This contribution presents the final design of novel, steady-state, magnetic sensors for ITER. A poloidal array of 60 sensors mounted on the vacuum vessel outer shell contributes to the measurement of the plasma current, plasma-wall clearance, low-frequency MHD modes and will allow for crosscheck with the outer-vessel inductive coils. Each sensor hosts a pair of bismuth Hall probes, themselves an outcome of extensive R&D, including neutron irradiations (to 1023 n/m2), temperature cycling tests (73-473 K) and tests at high magnetic field (to 12 T). A significant effort has been devoted to optimize the sensor housing by design and prototyping. The production version features an indium-filled cell for in situ recalibration of the onboard thermocouple, vital for the interpretation of the Hall sensor measurement.

High magnetic field test of the ITER outer vessel steady-state magnetic field Hall sensors at ITER relevant temperature.

The ITER outer vessel steady-state magnetic field sensor diagnostics consist of sixty sensor units. Each sensor unit features a pair of ceramic-metal Hall sensors with a sensing layer made of bismuth. The sensors were tested simultaneously in the magnetic field ranging from -12 T to +12 T at the temperature range from 27 to 127 °C. The Hall coefficient and magnetoresistance of the bismuth layer related to the sensors were identified. In the sensor operating conditions, the Hall coefficient dependence on temperature was fitted with an exponential function with a relative error of less than 0.08%, and the dependence on the magnetic field was fitted with a Gaussian-like function with a relative error of less than 0.11%. An alternative expression based on the physical understanding of the free charge carrier transport in semimetals was derived to describe the dependence of the Hall coefficient on the magnetic field, and its fitting error of 1.2 mT in terms of the magnetic field measurement has met the ITER measurement accuracy requirements.

A fast feedback controlled magnetic drive for the ASDEX Upgrade fast-ion loss detectors.

A magnetically driven fast-ion loss detector system for the ASDEX Upgrade tokamak has been designed and will be presented here. The device is feedback controlled to adapt the detector head position to the heat load and physics requirements. Dynamic simulations have been performed taking into account effects such as friction, coil self-induction, and eddy currents. A real time positioning control algorithm to maximize the detector operational window has been developed. This algorithm considers dynamical behavior and mechanical resistance as well as measured and predicted thermal loads. The mechanical design and real time predictive algorithm presented here may be used for other reciprocating systems.

Stokes-Doppler coherence imaging for ITER boundary tomography.

An optical coherence imaging system is presently being designed for impurity transport studies and other applications on ITER. The wide variation in magnetic field strength and pitch angle (assumed known) across the field of view generates additional Zeeman-polarization-weighting information that can improve the reliability of tomographic reconstructions. Because background reflected light will be somewhat depolarized analysis of only the polarized fraction may be enough to provide a level of background suppression. We present the principles behind these ideas and some simulations that demonstrate how the approach might work on ITER. The views and opinions expressed herein do not necessarily reflect those of the ITER Organization.

Conceptual design of the ITER fast-ion loss detector.

A conceptual design of a reciprocating fast-ion loss detector for ITER has been developed and is presented here. Fast-ion orbit simulations in a 3D magnetic equilibrium and up-to-date first wall have been carried out to revise the measurement requirements for the lost alpha monitor in ITER. In agreement with recent observations, the simulations presented here suggest that a pitch-angle resolution of ∼5° might be necessary to identify the loss mechanisms. Synthetic measurements including realistic lost alpha-particle as well as neutron and gamma fluxes predict scintillator signal-to-noise levels measurable with standard light acquisition systems with the detector aperture at ∼11 cm outside of the diagnostic first wall. At measurement position, heat load on detector head is comparable to that in present devices.

High magnetic field test of bismuth Hall sensors for ITER steady state magnetic diagnostic.

Performance of bismuth Hall sensors developed for the ITER steady state magnetic diagnostic was investigated for high magnetic fields in the range ±7 T. Response of the sensors to the magnetic field was found to be nonlinear particularly within the range ±1 T. Significant contribution of the planar Hall effect to the sensors output voltage causing undesirable cross field sensitivity was identified. It was demonstrated that this effect can be minimized by the optimization of the sensor geometry and alignment with the magnetic field and by the application of "current-spinning technique."

Signalling profiles of H3 relaxin, H2 relaxin and R3(BΔ23-27)R/I5 acting at the relaxin family peptide receptor 3 (RXFP3).

BACKGROUND AND PURPOSE: Relaxin family peptide receptor 3 (RXFP3) is expressed in brain areas important for processing sensory information and feeding, suggesting that it may be a target for anti-anxiety and anti-obesity drugs. We examined the effects of H3 relaxin, the biased agonist H2 relaxin and the antagonist, R3(BΔ23-27)R/I5, on RXFP3 signalling to establish their suitability as tools to assess the physiological roles of RXFP3. EXPERIMENTAL APPROACH: The signalling profile of the RXFP3 ligands was determined using reporter gene assays, multiplexed signalling assays and direct examination of receptor-G protein and receptor-ß-arrestin interactions using BRET. KEY RESULTS: H2 relaxin activated p38MAPK and ERK1/2 with lower efficacy than H3 relaxin, but had similar efficacy for JNK1/2 phosphorylation. H2 or H3 relaxin activation of p38MAPK, JNK1/2 or ERK1/2 involved Pertussis toxin-sensitive G-proteins. R3(BΔ23-27)R/I5 blocked H3 relaxin AP-1 reporter gene activation, but not H2 relaxin AP-1 activation or H3 relaxin NF-κB activation. R3(BΔ23-27)R/I5 activated the SRE reporter, but did not inhibit either H2 or H3 relaxin SRE activation. R3(BΔ23-27)R/I5 blocked H3 relaxin-stimulated p38MAPK and ERK1/2 phosphorylation, but was a weak partial agonist for p38MAPK and ERK1/2 signalling. p38MAPK activation by R3(BΔ23-27)R/I5 was G protein-independent. H3 relaxin-activated RXFP3 interacts with Gαi2 , Gαi3 , Gαo A and Gαo B whereas H2 relaxin or R3(BΔ23-27)R/I5 induce interactions only with Gαi2 or Gαo B . Only H3 relaxin promoted RXFP3/ß-arrestin interactions that were blocked by R3(BΔ23-27)R/I5. CONCLUSION AND IMPLICATIONS: Understanding signalling profile of drugs acting at RXFP3 is essential for development of therapies targeting this receptor.

Tungsten injector for scrape-off layer impurity transport experiments in the Tore Supra tokamak.

This paper describes the design and operation of a new tungsten (W) injection system for impurity transport experiments in the Tore Supra tokamak. The system is mounted on a reciprocating manipulator and injects a controlled amount of gaseous tungsten hexacarbonyl, W(CO)6 at arbitrary depth in the scrape-off layer, using an inertially activated valve. Injected W(CO)6 is dissociated in the plasma, forming a radially localized plume of W atoms. The injector does not require an external gas feed and can perform a large number of injections from an on-board reservoir of W(CO)6. Some examples of W injections in Tore Supra are included, demonstrating successful operation and discussing some technical issues of the injector prototype.

Relaxin family peptides and their receptors.

There are seven relaxin family peptides that are all structurally related to insulin. Relaxin has many roles in female and male reproduction, as a neuropeptide in the central nervous system, as a vasodilator and cardiac stimulant in the cardiovascular system, and as an antifibrotic agent. Insulin-like peptide-3 (INSL3) has clearly defined specialist roles in male and female reproduction, relaxin-3 is primarily a neuropeptide involved in stress and metabolic control, and INSL5 is widely distributed particularly in the gastrointestinal tract. Although they are structurally related to insulin, the relaxin family peptides produce their physiological effects by activating a group of four G protein-coupled receptors (GPCRs), relaxin family peptide receptors 1-4 (RXFP1-4). Relaxin and INSL3 are the cognate ligands for RXFP1 and RXFP2, respectively, that are leucine-rich repeat containing GPCRs. RXFP1 activates a wide spectrum of signaling pathways to generate second messengers that include cAMP and nitric oxide, whereas RXFP2 activates a subset of these pathways. Relaxin-3 and INSL5 are the cognate ligands for RXFP3 and RXFP4 that are closely related to small peptide receptors that when activated inhibit cAMP production and activate MAP kinases. Although there are still many unanswered questions regarding the mode of action of relaxin family peptides, it is clear that they have important physiological roles that could be exploited for therapeutic benefit.

On the reliability of scrape-off layer ion temperature measurements by retarding field analyzers.

The retarding field analyzer (RFA) is one of the only widely accepted diagnostics for measurements of ion temperature Ti in the tokamak scrape-off layer. In this paper we analyze some instrumental effects of the RFA and their influence on Ti measurements. It is shown that selective ion transmission through the RFA slit is responsible for an overestimation of Ti by less than 14%, even for a relatively thick slit plate. Therefore, thicker slit plates are preferable, since they reduce, e.g., the risk of melting during off-normal events, and the effect of positive space charge inside the cavity. The influence of the electron repelling grid, as well as misalignment of the slit with respect to the magnetic field on Ti measurements are negligible.

Cardiovascular effects of acute stroke.

A wide variety of dysrhythmias, conduction defects, and repolarization abnormalities have been observed following all types of stroke, most likely related to disruptions in the autonomic nervous system. Patients at highest risk for developing ECG changes include those with hemorrhagic stroke, those with strokes involving the right cerebral hemisphere, and elderly patients with stroke. Nursing interventions for these patients revolve around vigilant monitoring of both neurologic and cardiovascular status, to identify any negative consequences from the interaction of these systems. Strict blood pressure monitoring is required, with different management goals depending upon the type of stroke. Also important is the prevention of further exacerbation of ECG abnormalities by maintaining normal electrolyte levels.

The brain-heart connection: cardiac effects of acute ischemic stroke.

Cerebrovascular events are known to produce changes in the electrocardiogram (ECG). Whether or not these changes are actually reflective of myocardial damage has been the topic of much research. There are indications that these ECG changes result from an imbalance in the autonomic nervous system, resulting in a relative excess of sympathetic activity. This article provides an overview of the ECG and physiologic changes noted in patients with acute ischemic stroke and identifies subgroups that may be at high risk for developing these changes. Implications for nursing care are discussed.

Intrahospital transport of neuro ICU patients.

Neuroscience intensive care unit (NICU) patients are frequently transported out of the critical care environment for diagnostic and interventional procedures. Four hundred and seventy-one such transports from seventeen clinical centers were studied to identify the characteristics of intrahospital transport. Data collected included the destination and duration of transport, number and type of personnel involved, changes in monitoring and treatment during transport, adverse patient responses and the impact on patients left in the unit. Differences between transports characterized as elective or emergent in nature were noted. Results validate that intrahospital transport of NICU patients is both time and labor intensive. The study also suggests that the optimal process for safe and efficient transport is yet to be designed.

Applying critical pathways to neurosurgery patients at the University of Michigan Medical Center.

UNLABELLED: Project Overview: In April 1990, The University of Michigan Hospitals began a major, multidisciplinary project to standardize care processes in order to increase efficiency and reduce costs while maintaining the quality of clinical care. A team of nurses began the project by developing critical pathways for two neurosurgery procedures--lumbar laminectomy and transphenoidal pituitary tumor resection. The pathways were reviewed by physicians and other staff from other disciplines and were implemented in January of 1991. KEY FINDINGS: Data from the first 14 months show a decrease in patients' average lengths of stay in both the intensive care unit (ICU) and routine care unit. Costs and variance data are being analyzed and further improvements to the pathways are being made. Eleven critical paths are now being used for neurosurgery patients. In retrospect, participants learned that physicians should be involved at the earliest stages of critical pathway development and in the process of implementation.

Changes in self- and object representation as revealed by reflection response.

This article considers the three Rorschach tests obtained over an 8-year period for one female patient who struggled around her image of herself and others. Her struggle is revealed in the vicissitudes of the reflection responses over the three testings. A formulation is advanced regarding the meaning and significance of the reflection response as an indication of an emerging self-experience.

Pulmonary considerations in the critical care phase.

Spinal cord injuries create alterations in ventilatory mechanics that range from complete ventilator dependence in high cervical injuries to the need for an assisted cough to clear secretions in low thoracic injuries. The initial nursing assessment should include the degree of respiratory muscle impairment, the effectiveness of the patient's inspiratory efforts, and the ability to cough. Once the mechanisms responsible for respiratory difficulty have been determined, nursing interventions can be planned to compensate for impaired function. This may involve assisted coughing, frequent chest physiotherapy and suctioning, monitoring vital capacity and ABGs, and use of kinetic beds. Perhaps the greatest challenge for both the nurse and the patient is weaning from mechanical ventilation. Weaning requires a coordinated plan, based on trust between patient and nurse, in order to achieve maximum independence from ventilatory support.

Electrocardiographic changes following subarachnoid hemorrhage.

Electrocardiographic abnormalities are frequently seen in patients who have experienced a subarachnoid hemorrhage (SAH). These changes often mimic those seen in acute myocardial infarction although often patients have no history or other symptoms of cardiac disease. This paper reviews the types of rhythm disturbances seen following SAH and discusses the pathophysiologic basis for these changes. It also presents possible nursing interventions for these patients and explores areas needing further research.

The Triservice anaesthetic apparatus. Trial of isoflurane and enflurane as alternatives to halothane.

Sixty male patients undergoing limb surgery were anaesthetised using a drawover technique with the Triservice apparatus. They were randomly allocated to receive trichloroethylene and one of three other volatile agents (halothane, enflurane or isoflurane) after thiopentone induction. Signs of inadequate anaesthesia were noted. The incidence of such signs was not significantly different in the three groups. Similarly, no qualitative difference could be demonstrated in the immediate recovery, but the recovery time was significantly shorter with enflurane.

A comparison of continuous and intermittent enteral nutrition in NICU patients.

Tube feedings are frequently used for the nutritional support of neurologically impaired patients. Feedings may be delivered either continuously or intermittently. There is little evidence for advantages of one method over the other in patients with neurologic problems. In this study, a convenience sample of 34 adult neurological intensive care unit (NICU) patients were randomly assigned to either continuous or intermittent administration. No significant differences were found in number or consistency of stools per day, presence of blue dye in pulmonary secretions as evidence of aspiration, or in caloric intake as a percent of the patient's nutritional goal. Also, there was no correlation between patient's level of consciousness, based on Glasgow Coma Scale (GCS), and the incidence of aspiration. Implications for nursing practice are discussed.