The fusion power density produced in a tokamak is proportional to its magnetic field strength to the fourth power. Second-generation high temperature superconductor (2G HTS) wires demonstrate ...remarkable engineering current density (averaged over the full wire), JE, at very high magnetic fields, driving progress in fusion and other applications. The key challenge for HTS wires has been to offer an acceptable combination of high and consistent superconducting performance in high magnetic fields, high volume supply, and low price. Here we report a very high and reproducible JE in practical HTS wires based on a simple YBa2Cu3O7 (YBCO) superconductor formulation with Y2O3 nanoparticles, which have been delivered in just nine months to a commercial fusion customer in the largest-volume order the HTS industry has seen to date. We demonstrate a novel YBCO superconductor formulation without the c-axis correlated nano-columnar defects that are widely believed to be prerequisite for high in-field performance. The simplicity of this new formulation allows robust and scalable manufacturing, providing, for the first time, large volumes of consistently high performance wire, and the economies of scale necessary to lower HTS wire prices to a level acceptable for fusion and ultimately for the widespread commercial adoption of HTS.
Charged-particle nested traps are considered to be free from impurity-charged particles. However, that is not always the case. We show that in addition to the original ions, charged particles are ...generated in nested traps during the plasma translation experiments. This study demonstrates electrons being accelerated by a pair of positive potential wells in a nested trap as soon as they are translated from the adjacent trap. The accelerated electrons cause ionization of the residual gas on impact and produce ions in addition to the ions already present in the nested trap. Well-known ions such as H2+, H2O+, and N2+, were also detected. We also explore methods for reducing experimental errors due to such impurity ions.
•Impurity ions besides the original ions arise in nested traps in plasma translation experiments.•It is identified that the species of the impurity ions consist of well-known ions that may be contained in any traps.•The mechanism is due to electrons that are side-trapped in potential wells of a nested trap.•This study also clarified ways to avoid experimental errors due to such impurity ions.
The reflectance spectra of the most abundant meteorites, ordinary chondrites, are different from those of the abundant S-type (mnemonic for siliceous) asteroids. This discrepancy has been thought to ...be due to space weathering, which is an alteration of the surfaces of airless bodies exposed to the space environment. Here we report evidence of space weathering on particles returned from the S-type asteroid 25143 Itokawa by the Hayabusa spacecraft. Surface modification was found in 5 out of 10 particles, which varies depending on mineral species. Sulfur-bearing Fe-rich nanoparticles exist in a thin (5 to 15 nanometers) surface layer on olivine, low-Ca pyroxene, and plagioclase, which is suggestive of vapor deposition. Sulfur-free Fe-rich nanoparticles exist deeper inside (<60 nanometers) ferromagnesian silicates. Their texture suggests formation by metamictization and in situ reduction of Fe2+.
Summary Objective When endoplasmic reticulum (ER) stress, i.e., the excessive accumulation of unfolded proteins in ER, endangers homeostasis, apoptosis is induced by C/EBP homologous protein (Chop). ...In osteoarthritis (OA) cartilage, Chop expression and apoptosis increase as degeneration progresses. We investigated the role of Chop in murine chondrocyte apoptosis and in the progression of cartilage degeneration. Method We induced experimental OA in Chop -knockout ( Chop −/− ) mice by medial collateral ligament transection and meniscectomy and compared cartilage degeneration, apoptosis, and ER stress in Chop −/− - and wild-type ( Chop +/+ ) mice. In our in vitro experiments we treated murine Chop −/− chondrocytes with the ER stress inducer tunicamycin (TM) and evaluated apoptosis, ER stress, and chondrocyte function. Results In vivo , the degree of ER stress was similar in Chop −/− - and Chop +/+ mice. However, in Chop −/− mice apoptosis and cartilage degeneration were lower by 26.4% and 42.4% at 4 weeks, by 26.8% and 44.9% at 8 weeks, and by 26.9% and 32.3% at 12 weeks after surgery than Chop +/+ mice, respectively. In vitro , the degree of ER stress induction by TM was similar in Chop −/− - and Chop +/+ chondrocytes. On the other hand, apoptosis was 55.3% lower and the suppression of collagen type II and aggrecan mRNA was 21.0% and 23.3% less, and the increase of matrix metalloproteinase-13 mRNA was 20.0% less in Chop −/− - than Chop +/+ chondrocytes. Conclusion Our results indicate that Chop plays a direct role in chondrocyte apoptosis and that Chop-mediated apoptosis contributes to the progression of cartilage degeneration in mice.
In Chapter 34 of Leviathan, Hobbes developed an original philological analysis of 'spirit'. Despite the uniqueness of this analysis, modern Hobbes scholars have shown little interest in it, without ...adding much to the common knowledge that it is one implication of his materialism.
However, this peculiar philological interpretation deserves attention, as it reflects various important factors and tackles delicate and complex issues. This article examines the interpretative, theoretical and political aspects of Hobbes's philological analysis to identify its distinctive
features and to explain why he developed it for the first time in Leviathan.
Electrostatic levitators have been around for more than 30 years and have become mature tools for the material science community. Originally developed as positioners for materials and fluid science ...experiments in space, they saw a myriad of offsprings throughout the world for ground-based research, not only in space agencies but also in governmental laboratories, in universities and in the industry. Electrostatic levitators eliminate any physical contact with a container allowing to process and study corrosive or high temperature materials in their solid or liquid phases. Moreover, heterogeneous contamination from the container being avoided, it is possible to reach and maintain supercooled and metastable phases. This, in turns, permits a host of fundamental and applied studies. The nucleation and solidification phenomena can be scrutinized, the atomic structure and dynamic of liquid and metastable phases can be probed and the physics of molten drops could be investigated. On a more applied standpoint, the measure of thermophysical properties and the synthesis of materials with new properties are also possible with current facilities.
This paper first describes the principle of electrostatic levitation and retraces the development of various facilities throughout the world, focusing on the advances made by each research group. The capabilities of electrostatic levitation for materials processing and synthesis under different environments are then presented. The paper successively covers in length its contribution for the measurements of thermophysical properties and for fundamental studies using high energy particle beams. Finally, the outlook of electrostatic levitators and its attractiveness for space experiments in materials sciences are discussed.
Rubble-Pile Asteroid Itokawa as Observed by Hayabusa Fujiwara, A; Kawaguchi, J; Yeomans, D.K ...
Science (American Association for the Advancement of Science),
06/2006, Letnik:
312, Številka:
5778
Journal Article
Recenzirano
During the interval from September through early December 2005, the Hayabusa spacecraft was in close proximity to near-Earth asteroid 25143 Itokawa, and a variety of data were taken on its shape, ...mass, and surface topography as well as its mineralogic and elemental abundances. The asteroid's orthogonal axes are 535, 294, and 209 meters, the mass is 3.51 x 10¹⁰ kilograms, and the estimated bulk density is 1.9 ± 0.13 grams per cubic centimeter. The correspondence between the smooth areas on the surface (Muses Sea and Sagamihara) and the gravitationally low regions suggests mass movement and an effective resurfacing process by impact jolting. Itokawa is considered to be a rubble-pile body because of its low bulk density, high porosity, boulder-rich appearance, and shape. The existence of very large boulders and pillars suggests an early collisional breakup of a preexisting parent asteroid followed by a re-agglomeration into a rubble-pile object.
The field and temperature dependence of the critical current I c is a vital factor in designing the superconducting magnets. The standard method of measuring I c involves applying a dc current and ...measuring voltage. However, when assessing the field dependence of I c , the high magnetic field's space constraints and cooling power limit the injection of dc current into the sample. To address this, we have developed a method using pulsed current to significantly reduce heat generation. Our previous research reported an I c measurement system capable of handling up to 19 T and variable temperatures with a pulse current up to 500 A. In this study, we have enhanced the system with electric double layer capacitors, known as supercapacitors, allowing currents up to 2 kA. This upgrade enables the measurement of I c in the high-temperature superconducting REBCO tapes, which are 4 mm wide, at cryogenic temperatures as low as 4.2 K in magnetic fields or 20 K even under a self-field. We have verified the system's reliability by comparing measurements of dc and pulsed currents. Additionally, we contrasted the I c values of full width samples with those of samples containing micro-bridges.
We previously reported that giant crystal enantiomeric excess (CEE) can be obtained when sodium chlorate (NaClO3) chiral crystallization from a solution is induced by the excitation of localized ...surface plasmon resonance (LSPR) of a Au triangle trimer nanostructure by a circularly polarized laser. However, the role of the LSPR excitation in the giant CEE remains unclear. In this work, we showed, by finite-difference time-domain analysis of plasmonic near-field, that the magnitude of a chiral optical gradient force originating from the strong superchiral near-field at the Au trimer nanogap on a virtual NaClO3 chiral crystalline cluster is comparable to that of the electric-field gradient force in previous laser-trapping-induced crystallization from unsaturated solution. We revealed that the giant CEE resulted from a difference in the frequency of attachment of chiral crystalline clusters to crystal nuclei or in the local concentration due to chirally biased diffusion rather than enantioselective optical trapping.
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