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A 4th generation ECR (electron cyclotron resonance) ion source FECR (first 4th generation ECR ion source) is under construction at IMP (Institute of Modern Physics). Aiming to be operated with the microwave power of 20 kW at 45 GHz, a fully superconducting Nb3Sn magnet is to be developed to realize the optimum ECR plasma confinement. As the first superconducting ECR magnet that utilizes single-strand Nb3Sn (niobium three tin) wire for the winding of coils consisting of 4 sets of axial solenoids and one sextupole, it poses many challenges in the coil fabrication, cold mass assembly, magnet quench protection, and so on. With a shell-based structure and bladder-and-key technology, we have completed a 1/2-length FECR cold mass prototype. It has been fully tested when immersed in 4.2 K liquid helium. The critical issue in this work is to keep the brittle Nb3Sn wire safe during the complicated mechanical process and protect it against the high current high magnetic field excitation. In this paper, we will report on the details of how to design, fabricate, assemble, and test a high-performance Nb3Sn sextupole with the existence of sophisticated magnetic fields and stresses. The successful test of a high-current sextupole coil in a so-called mirror structure will be reported. The application of the bladder-and-key structure to the prototype and the performance will be presented. This research has also tackled the solutions to mitigate very intense flux jump that has caused severe challenges to quench detection and protection. [ABSTRACT FROM AUTHOR]

Nanoindentation has now become the key technique for measuring the mechanical properties of materials at small scales. However, the quantitative and accurate processing of nanoindentation data relies on a physical quantity that is not directly available: the contact area (Ac) between the indenter tip and the sample under test. In complex systems, determining Ac is challenging due to the limitations of standard methods: analytical models have restricted validity domains (sample homogeneity and rheology), and post-mortem observations of residual imprints are time-consuming, do not appraise property gradients and cannot be applied to materials with significant elastic recovery. In this paper, a comprehensive methodology is proposed to continuously measure contact area during indentation. The proposed methodology, referred to as electrical-nanoindentation (ENI), is based on real-time monitoring of the electrical contact resistance (ECR). The protocol only requires mechanical and electrical calibrations of the indenter tip on reference materials, leading to one-to-one relationship between ECR and contact area. An original approach is also proposed to deal with the presence of surface passivating layers that generally disturb ECR measurements. As an illustration, the methodology is applied to the characterization of a multi-phase alloy (MPA) composed of silver, copper and palladium. This alloy raises the same challenges as those usually faced by nanoindentation in advanced metallurgy: heterogenous distribution of individual phases at the micro-scale, composite response of a complex mixture of hard/stiff and ductile/soft phases, ... In addition, the ohmicity of contact is disturbed by surface passivating layers. Despite these numerous hindrances, the proposed methodology is successfully applied to this material. The evolution of contact area is compared with standard methods: an impressive accuracy of <2% standard-deviation is achieved when compared to post-mortem observations. The elastic moduli and hardnesses of individual phases are then accurately extracted. In addition, in order to gain in spatial definition, the ENI set-up is integrated into a scanning electron microscope (SEM), enabling indent positioning with a precision close to 100 nm. Two challenges are successfully met with the ENI methodology. On a mechanical point of view, the response of individual phases can be identified despite the complex rheology of heterogeneous materials, proving the approach applies to all mechanical behaviors (sink-in or pile-up rheologies, homogeneous or heterogeneous materials, with or without elastic recovery, ...). On an electrical point of view, even if contact ohmicity is the only requirement of the methodology, it is possible to identify and overcome deviations from contact ohmicity induced by surface passivation. In particular, the non-linear resistive contribution of insulating layers fades during indentation thanks to its dependence as the reciprocal of the square of contact radius. The present work provides the keys to monitoring the contact area on any metallic sample, whether oxide-free or oxidized, making this methodology a promising alternative to standard methods. [Display omitted] • A methodology is proposed to continuously measure contact area during indentation. • The methodology processes ECR after simple electrical and mechanical calibrations. • The effect of surface passivating layer on electrical contact ohmicity is discussed. • Applied to a multi-phase alloy, an impressive accuracy is obtained (2% std-dev.). • Hardness and modulus can then be extracted accurately at a micrometer-scale. [ABSTRACT FROM AUTHOR]

Regenerative ability often declines as animals mature past embryonic and juvenile stages, suggesting that regeneration requires redirection of growth pathways that promote developmental growth. Intriguingly, the Drosophila larval epithelia require the hormone ecdysone (Ec) for growth but require a drop in circulating Ec levels to regenerate. Examining Ec dynamics more closely, we find that transcriptional activity of the Ec-receptor (EcR) drops in uninjured regions of wing discs, but simultaneously rises in cells around the injury-induced blastema. In parallel, blastema depletion of genes encoding Ec biosynthesis enzymes blocks EcR activity and impairs regeneration but has no effect on uninjured wings. We find that local Ec/EcR signaling is required for injury-induced pupariation delay following injury and that key regeneration regulators upd3 and Ets21c respond to Ec levels. Collectively, these data indicate that injury induces a local source of Ec within the wing blastema that sustains a transcriptional signature necessary for developmental delay and tissue repair. [ABSTRACT FROM AUTHOR]

Background: The performance and endurance of lubricating greases is often assessed through model tests (like four-ball tests or SRV tests). This approach has some limitations, especially when greases with special fillers are investigated, because simplified laboratory test conditions can never replicate real operating conditions. Objective: For a more reliable assessment on the performance of a lubricating grease, lubricants must be tested in close-to-actual operational conditions, e.g. through component tests. This paper presents both the design and implementation of a dedicated test rig to test lubricating greases through middle-sized thrust ball bearings. Methods: The test rig design is optimized to monitor the effectiveness of lubrication and determine the useful life of grease by recording representative parameters, namely bearing temperature at different location in the bearing, vibration level, and electric contact resistance (ECR) through the bearing. Results: The results of a couple of assessment tests are presented and confirm that the test rig is working as expected. Conclusions: The chart of the parameters being monitored shows that the instant performance of grease lubrication can be tracked during the endurance tests, and grease failure identified. The special mechanical layout of the rig also allows the user to obtain additional information that is usually not available in other commercial greased bearing testers. This work is meant to be the first step of the development a new approach to evaluate the grease lubrication performance and a few experimental results are included as they are intended as a functional validation of the prototyped test rig.