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While previous studies consistently suggest that North Atlantic Deep Water (NADW) was shallower at the Last Glacial Maximum (LGM) than at pre‐industrial, its strength is still controversial. Here, using a series of LGM experiments, we show that proxy records are consistent with a shallower and ∼50% weaker NADW, associated with a ∼3° equatorward shift of the sea ice edge and convection sites in the Norwegian Sea. A shoaling and weakening of NADW further allow penetration of Antarctic Bottom Water in the North Atlantic, despite Antarctic Bottom Water transport being reduced by ∼40%. While the Deep Western Boundary Current in the northwest Atlantic weakens with NADW, the mid‐depth southward flow on the east side of the north Mid‐Atlantic Ridge strengthens, consistent with paleorecords. This northeast Atlantic intensification is due to a change in density gradients: a weaker AMOC reduces the transport of equatorial waters to the northeast Atlantic, thus weakening the North Atlantic zonal density gradient. The resultant globally weaker oceanic circulation at the LGM would have contributed to an increase in oceanic carbon content and thus a decrease in atmospheric CO 2 concentration. Key Points: As the AMOC weakens, Nordic Sea sea ice and convection sites shift equatorward and the Deep Western Boundary Current weakens proportionallyAs the AMOC weakens, the southward flow on the eastern side of the Mid‐Atlantic Ridge strengthens by up to 100%Proxy records are consistent with both weaker NADW and AABW at the Last Glacial Maximum [ABSTRACT FROM AUTHOR]

We developed a fully automated magnetic field scanner dedicated to uniaxial magnetic field measurements to determine remanent magnetization intensities and their variations in sedimentary U‐channels. A fluxgate magnetometer located as close as possible to the sedimentary section is used to perform uniaxial measurements of magnetic fields generated by the isothermal remanent magnetization of the sediment. This artificial magnetization, which is known to be a powerful proxy in environmental magnetism, is produced perpendicular to the U‐channel long axis, and parallel to the fluxgate axis, using a Halbach cylinder prior to the measurement. The present magnetic scanner offers a maximal spatial resolution of 5.8 mm for point sources. A spatial resolution of 14 mm is obtained for U‐channel samples. The magnetic scanner presents a reliable magnetic field range over about 3 orders of magnitude allowing measurement of magnetizations that saturate the Superconducting Rock Magnetometer in its classical configuration. The estimation of remanent magnetization intensities along the U‐channel is based on a modeling approach that uses successive uniformly magnetized prisms. In lacustrine laminated sections, comparison between modeling results based on prisms of a constant thickness, on prisms determined from sedimentary facies, and on prisms determined from X‐ray fluorescence data helps to understand the detrital versus diagenetic history of the sedimentary succession. Key Points: We propose a fast and high‐resolution scanning of local magnetic field generated by isothermal remanent magnetization acquired on U‐channelsThe scanner offers an optimization of the spatial resolution according to the sedimentary section diameterThe modeling process is constrained by sedimentary features [ABSTRACT FROM AUTHOR]

Deals with a study of hydrogen[subc2] enhancement due to the addition of titanium to the matrix of bronze-processed niobium[sub3] tin wires. Information on how the values of γ can be obtained; Significance of the mechanism of hydrogen [subc2].

Presents a study that examined the enhanced high-field current carrying capacities and pinning behavior of Niobium-based alloys. List of alloys used in the study; Device used to examine the microstructural features of alloys; Current density capacity of NbTi superconducting alloys.

Deals with a study which investigated improvements in high-field superconducting performance of V[sub3]Ga by a two-stage reaction process. Preparation of the V[sub3]Ga specimens; Findings.

Holocene Eastern Mediterranean Sea sediments contain an organic-rich sapropel S1 layer that was formed in oxygen-depleted waters. The spatial distribution of this layer revealed that during S1 deposition deep waters were permanently anoxic below 1800 m in water depth. To provide further insight into past Eastern Mediterranean Sea circulation, a multi-proxy approach was applied to a core retrieved close to the 1800 m boundary (at 1780 m). We measured the bulk sediment elemental composition, the stable isotopic composition of the planktonic foraminifer Globigerinoides ruber, and the abundance of benthic foraminifera since the last deglaciation. The result indicates that authigenic U and Mo accumulation began around 13-12 cal ka BP, in concert with surface water freshening estimated from the G. ruber δ18O record. The onset of bottom/pore water oxygen depletion occurred prior to S1 deposition inferred from barium enrichment. In the middle of the S1 deposition period, between 9 and 8 cal ka BP, reduced authigenic V, Fe and As contents and Br / Cl ratio indicated short-term bottom water re-oxygenation. A sharp Mn peak and maximal abundance for benthic foraminifera marked a total recovery for circulation at approximately 7 cal ka BP. Based on our results and existing data, we suggest that S1 formation withinthe upper 1780 m of the Eastern Mediterranean Sea was preconditioned by reduced ventilation, resulting from excess fresh water inputs due to insolation changes under deglacial conditions, that initiated between 15 and 12 ka. Short-term re-oxygenation in the Levantine Basin is estimated to have affected bottom water below and above the anoxic boundary. We tentatively propose that complete ventilation recovery at the S1 termination was attained earlier within the upper 1780 m than at deeper water depths. Our results provided new constraints for eastern Mediterranean Sea thermohaline circulation. [ABSTRACT FROM AUTHOR]

Holocene Eastern Mediterranean Sea sediments contain an organic-rich sapropel S1 layer that was formed in oxygen-depleted waters. The spatial distribution of this layer revealed that during S1 deposition deep waters were permanently anoxic below 1800m in water depth. To provide further insight into past Eastern Mediterranean Sea circulation, a multi-proxy approach was applied to a core retrieved close to the 1800m boundary (at 1780 m). We measured the bulk sediment elemental composition, the stable isotopic composition of the planktonic foraminifer Globigerinoides ruber, and the abundance of benthic foraminifera since the last deglaciation. The result indicates that authigenic U and Mo accumulation began around 13-12 cal kaBP, in concert with surface water freshening estimated from the G. ruber δ18O record. The onset of bottom/pore water oxygen depletion occurred prior to S1 deposition inferred from barium enrichment. In the middle of the S1 deposition period, between 9 and 8 cal ka BP, reduced authigenic V, Fe and As contents and Br = Cl ratio indicated short-term bottom water re-oxygenation. A sharp Mn peak and maximal abundance for benthic foraminifera marked a total recovery for circulation at approximately 7 cal ka BP. Based on our results and existing data, we suggest that S1 formation within the upper 1780m of the Eastern Mediterranean Sea was preconditioned by reduced ventilation, resulting from excess fresh water inputs due to insolation changes under deglacial conditions, that initiated between 15 and 12 ka. Short-term re-oxygenation in the Levantine Basin is estimated to have affected bottom water below and above the anoxic boundary. We tentatively propose that complete ventilation recovery at the S1 termination was attained earlier within the upper 1780m than at deeper water depths. Our results provided new constraints for eastern Mediterranean Sea thermohaline circulation. [ABSTRACT FROM AUTHOR]

The intensity and/or extent of the northeastern Pacific Oxygen Minimum Zone (OMZ) varied in-phase with the Northern Hemisphere high latitude climate on millennial timescales during the last glacial period, indicating the occurrence of atmospheric and oceanic connections under glacial conditions. While millennial variability was reported for both the Greenland and the northern Atlantic Ocean during the last interglacial period, the climatic connections with the northeastern Pacific OMZ has not yet been observed under warm interglacial conditions. Here we present a new geochemical dataset, spanning the past 120 ka, for major components (terrigenous fraction, marine organic matter, biogenic opal, and carbonates) generated by X-ray fluorescence scanning alongside with biological productivity and redox sensitive trace element content (Mo, Ni, Cd) of sediment core MD02-2508 at 23° N, retrieved from the northern limit of the modern OMZ. Based on elemental ratios Si / Ti (proxy for opal), Cd / Al and Ni / Al, we suggest that biological productivity was high during the last interglacial (MIS5). Highly resolved opal reconstruction presents millennial variability corresponding to all the Dansgaard-Oeschger interstadial events over the last interglacial, while the Mo / Al ratio indicates reduced oxygenation during these events. Extremely high opal content during warm interstadials suggests high diatom productivity. Despite the different climatic and oceanic background between glacial and interglacial periods, rapid variability in the northeastern Pacific OMZ seems to be tightly related to Northern Hemisphere high latitude climate via atmospheric and possibly oceanic processes. [ABSTRACT FROM AUTHOR]

The western Pacific warm pool (WPWP) is an important heat source for the atmospheric circulation and influences climate conditions worldwide. Understanding its sensitivity to past radiative perturbations may help better contextualize the magnitudes and patterns of current and projected tropical climate change. Here we present a new Mg/Ca-based sea surface temperature (SST) reconstruction over the past 400 kyr from the Bismarck Sea, off Papua New Guinea, along with results from a transient earth system model simulation. Our results document the primary influence of CO2 forcing on glacial/interglacial WPWP SSTs and secondary effects due to changes in wind-driven tropical boundary currents. In addition to the SST, deep ocean temperature reconstructions from this core are linked with Southern Ocean temperature and sea-ice variations on timescales of ~23 kyr. It is proposed that Southern Hemisphere insolation changes serve as pacemaker for sea-ice variations in the Southern Ocean, which in turn modulate windstress curl-driven upwelling of carbon-rich waters, hence controlling atmospheric CO2 and tropical WPWP temperatures. [ABSTRACT FROM AUTHOR]

A high-resolution sedimentological and geochemical study of a high-altitude proglacial lake (Lake Blanc, Aiguilles Rouges, 2352 m a.s.l.) revealed 195 turbidites, 190 of which are related to flood events over the last 1400 years. We used the coarsest sediment fraction of each turbidite as a proxy for the intensity of each flood event. Because most flood events at this locality are triggered by localized summer convective precipitation events, the reconstructed sedimentary record reveals changes in the frequency and intensity of such events over the last millennium. Comparisons with other temperature, palaeohydrological and glacier reconstructions in the region suggest that the most intense events occurred during the warmest periods, i.e. during the Medieval Climate Anomaly (AD 800-1300) and the current period of global warming. On a multi-decadal time scale, almost all the flood frequency peaks seem to correspond to warmer periods, whereas multi-centennial variations in flood frequency appear to follow the regional precipitation pattern. Consequently, this new Alpine flood record provides further evidence of a link between climate warming and an increase in the frequency and intensity of flooding on a multi-decadal time scale, whereas the centennial variability in flood frequencies is related to regional precipitation patterns. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

MgB2 superconducting thin wires sheathed with stainless steel (SS) have been prepared by in-situ powder-in-tube (PIT) process. Using Magnesium hydride MgH2 and amorphous B powders, SS sheathed MgB2 thin wires have been fabricated through drawing to form the round wires of 0.20 mm \sim0.10 mm in diameter. The SS sheath of 0.1 mm in diameter was hardened to be a Vickers hardness of around 600 HV through cold-working at room temperature without annealing. The heat treatment was performed at 630^\circC for 5 h in Ar gas atmosphere. The SS sheath recovered the hardness of 400 HV after heat treatment. [ABSTRACT FROM PUBLISHER]

Sn-based sheets with Ta, B or Nb particle dispersion have been prepared from consolidated alloys. A small amount of Ti addition strengthened the bonding between dispersed particles and the Sn matrix, which improved the workability of the sheet. The sheet was laminated with a Nb sheet, and wound into a Jelly Roll (JR) composite. The composite was easily fabricated to a wire without intermediate annealing. Thick and uniform \ Nb3{{\ {Sn}}} layers with nearly stoichiometric Sn concentration were synthesized by the mutual diffusion between Nb and Sn-based alloy layers. An offset Tc of \sim18.1 K and an offset Bc2 (4.2 K) of \sim26.5 T have been obtained after the heat treatment. The non-Cu Jc of the wires increased with decreasing the wire diameter. A non-Cu Jc of \sim \ 150 A/mm^2 has been obtained at 4.2 K and 22 T. The Sn–Ta, Sn–B and Sn–Nb based sheet JR wires exhibited similar microstructures and superconducting performances. [ABSTRACT FROM AUTHOR]

By reconstructing past hydrologic variations in the Northern Caribbean Sea and their influence on the stability of the Atlantic Meridional Overturning Circulation (AMOC) during the last 940 ka, we seek to document climate changes in this tropical area in response to the Mid-Pleistocene Transition (MPT). Using core MD03-2628, we estimated past changes in sea surface salinity (SSS) using Δδ18O, the difference between the modern, and the past Δδ18O of seawater (obtained by combining alkenone thermometer data with the Δδ18O of the planktonic foraminifera Globigerinoides ruber (white) and corrected for ice-sheet volume effects). Today, the lowest SSS values in the area studied are associated with the northernmost location of the Inter-Tropical Convergence Zone (ITCZ). The Δδ18O record obtained from core MD03- 2628 exhibits glacial/interglacial cyclicity with higher values during all glacial periods spanning the last 940 ka, indicating increased SSS. A long-term trend was also observed in the Δδ18O values that exhibited a shift toward lower values for interglacial periods during the last 450 ka, as compared to interglacial stages older than 650 ka. A rise in SSS during glacial stages may be related to the southernmost location of the ITCZ, which is induced by a steeper cross-equator temperature gradient and associated with reduced northward cross-equatorial oceanic transport. Therefore, the results suggest a permanent link between the tropical salinity budget and the AMOC during the last 940 ka. Following the MPT, lower salinities during the last five interglacial stages indicated a northernmost ITCZ location that was forced by changes in the cross-equator temperature gradient and that was associated with the poleward position of Southern Oceanic Fronts that amplify the transport of heat and moisture to the North Atlantic. These processes may have contributed to the amplification of the climate cycles that followed the MPT. [ABSTRACT FROM AUTHOR]

This study aimed at documenting climate changes in tropical area in response to the Mid-Pleistocene Transition (MPT) by reconstructing past hydrologic variations in the Northern Caribbean Sea and its influence on the stability of the Atlantic Meridional 5 Overturning Circulation (AMOC) during the last 940 kyr. Using core MD03-2628, we estimated past changes in sea surface salinity (SSS) using Δ18O, the difference between the modern and the past δ18O of seawater (obtained by combining alkenone thermometer data with the δ18O of the planktonic foraminifera Globigerinoides ruber (white) and corrected for ice-sheet volume effects). Today, the lowest SSS values in 10 the studied area are associated with the northernmost location of the Inter-Tropical Convergence Zone (ITCZ). The Δ18O record exhibits glacial/interglacial cyclicity with higher values during all glacial periods spanning the last 940 kyr, indicating increased SSS. At a longer timescale, the Δδ18O exhibits a shift toward lower values for interglacial periods during the last 450 kyr, when compared to interglacial stages older than 650 kyr. A rise in SSS during glacial stages may be related to the southernmost location of the ITCZ, which is induced by a steeper interhemispheric temperature gradient and associated with reduced northward cross equatorial oceanic transport. Therefore, the results suggest a permanent link between the tropical salinity budget and the AMOC during the last 940 kyr. Following the MPT, lower salinities during the last five interglacial stages indicate a northernmost ITCZ location, forced by changes in the interhemispheric temperature gradient that is associated with the poleward position of Southern Oceanic Fronts that amplified the transport of heat and moisture to the North Atlantic. These processes may have contributed to amplification of the climate cycles that followed the MPT. [ABSTRACT FROM AUTHOR]

In-situ powder-in-tube MgB2 tapes have been prepared through a hot pressing process. Magnesium hydride MgH2 and amorphous B powders were mixed to synthesize MgB2 superconductor. The mixed powder was encased in a steel tube and rolled into a monocore tape of about 4 mm in width and 0.5 mm in thickness. Nano-sized SiC and TiC powders were added to the MgB2 core. The tapes were hot-pressed under 100 MPa during the heat treatment in Ar gas atmosphere. The Ic for the hot-pressed tapes with 5 mass% SiC addition exceeds 300 A at 4.2 K and 5 T, which corresponds to a core Jc of nearly 1,000 A/mm2. The core Jc is enhanced by more than a factor of two compared to that of tapes without pressing during the heat treatment. The higher Jc in hot pressed tapes results from the improvement of the denser MgB2 structures with less voids and better linkage among MgB2 grains. [ABSTRACT FROM AUTHOR]

Tightly shrunk Sn-Ta ingots with good workability were prepared by the reaction at 750°C–800°C from the mixed powder of Sn and Ta containing 25–30at%Ta. Then Jelly Roll processed wires were fabricated starting from Sn-Ta/Nb composites in which thick (Nb, Ta)3Sn layers were produced after the heat treatment. A few wt% Cu addition to the Sn-Ta mixed powder reduces the heat treatment temperature. Moreover, a few at% Ti substitution for Sn + Ta enhances the formation of (Nb, Ta)3Sn layer, and improves the non-Cu Jc of the wire. In the present study, effect of the Sn-Ta-Ti-Cu sheet composition on the structure and high-field performance of the wire has been studied. It has been found that a small amount of Ti and Cu addition decreases the amount of Ta in the sheet from 25–30at% to 10at%, which is favorable for the material cost reduction. Moreover, it has been revealed that thick (Nb, Ta)3Sn layers are synthesized even if the Cu concentration in the sheet is decreased less than lwt% when a few at% Ti is substituted. A non-Cu Jc of ∼ 150 A/mm2 has been obtained at 22 T and 4.2 K in the wires with different sheet composition after the heat treatment at 725°–750°C. [ABSTRACT FROM AUTHOR]

Bi2212 HTS conical tubular conductors have been prepared by the diffusion process for current lead application. The Bi2212 HTS layers are synthesized through the diffusion reaction between a Sr-Ca-Cu oxide substrate and a Bi-Cu oxide coating with Ag addition. The HTS diffusion layers about 150 micrometer in thickness are formed around both outside and inside of the conical tubes 37/29 mm in outside/inside diameter at the larger end, 27/19 mm in outside/inside diameter at the smaller end, and 200 mm in length. The Ag added to the coating enhances the diffusion reaction, and precipitates on the surface of the specimen decreasing its contact resistance. The transport current of the specimen exceeds 7,000 A at 4.2 K and self-field, which corresponds to the current density of 32,000 A/cm² for the Bi2212 layer. The transport current decreases with increasing temperature at the warm end of the conical specimen, and is about 4,600 A at 30 K, 3,200 A at 40 K or 2,000 A at 50 K. The total heat loads composed of heat leakage conducted through the conical tube and Joule heating at the joint are estimated to be about 320 mW at 3,000 A between the warm end of 42 K and the cold end of 4.2 K, and is 400 mW at 2,000 A between 50 K and 4.2 K, respectively. Present Pb-free Bi2212 conical tubes seem to be promising as large transport current leads with small heat loads for superconducting magnets. [ABSTRACT FROM AUTHOR]

We fabricated three kinds of A 15-type superconducting tapes by applying ex situ Powder-In-Tube method. Nb3Su, Nb3AI, or V3Si superconducting powder was tightly packed into a stainless steel (SUS 316) tube or a Cu-10wt%Ni tube. These tubes were cold-rolled into tapes. All tapes showed substantial Jc values at 4.2 K without any heat treatment. The SUS 316 tube with superior mechanical hardness was effective for obtaining high density A15 cores and realizing high Jc values although Tc values were depressed by the lattice distortion. Annealing after cold rolling recovered Tc values and enhanced Jc values of all three kinds of tapes. Jc increased with increasing annealing temperature. More than two orders of magnitude higher Jc values were obtained for Nb3 Sn and V3Si tapes after the annealing at 900° C, while the Jc enhancement of Nb3 Al tape was smaller than one order of magnitude. This difference of Jc enhancement can be explained by the difference of microstructural change by the annealing. The field dependence of Jc decreased with increasing annealing temperature, which can also be explained by the recovery of Tc. [ABSTRACT FROM AUTHOR]

Sn-Ta-Cu buttons with enough ductility to be fabricated into thin sheets were synthesized by melting a mixture of Sn+Ta+(Cu) powder. (Nb, Ta)3Sn wires have been prepared by a Jelly Roll (JR) process and a filamentary process. In the JR process a Sn-Ta(-Cu) sheet was laminated with a Nb sheet forming a JR composite. In the filamentary process a Sn-Th(-Cu) sheet was wrapped around thirteen Nb-1.0 at%Ta rods forming a filamentary composite. Both composites were fabricated into wires without intermediate annealing, and then heat treated. The effect of Ge and Ti addition to the Sn-Ta-Cu sheet has been studied in the JR wires. A small amount of Ge addition improves the workability of the sheet, while that of Ti addition enhances appreciably the Jc of the JR wires. Meanwhile, the 13-core filamentary wires exhibit equivalent high-field performance as that of the JR wires. Present new (Nb, Ta)3Sn wires can be fabricated through a relatively easy process, and show attractive Jc in the field range of 22-23 T at 4.2 K and that of 24-25 Tat 2.1 K. [ABSTRACT FROM AUTHOR]

Tapes and wires of V3Ga were first made in Japan based on the discovery of the effect of Cu additive for the promotion of V3Ga synthesis. The bronze process applied to V3Ga was extended to the fabrication of Nb3Sn. The Ti addition to the bronze matrix was also initiated in Japan so as to improve significantly high-field performance. The so-called internal tin and Nb tube processes were also initiated in Japan. These achievements on V3Ga and Nb3Sn lead into the recent active development of high-field, large-scale, and refrigerator-cooled superconducting magnet applications. As for Nb3Al, which shows excellent strain tolerance, various approaches were made in Japan to achieve stoichiometry and fine grain structures. Among them the Jelly-Roll process is the most reliable method to produce long-lengths of Nb3Al wire for fusion uses. High performance Nb3Al conductors for high-field use are being produced by the rapidly heating, quenching and transformation annealing (RHQT) process. Future progress in the A15 conductor development in Japan may be expected through improved processes. [ABSTRACT FROM AUTHOR]

Structure and high-field performance of(Nb, Ta)3 Sn conductors fabricated by using ductile Sn-Ta matrix are reported. A mixed powder of Sn and Ta with or without a small amount of Cu addition was melted at 800° C in vacuum. The resulting Sn-Ta alloy was rolled into a sheet 100 μm in thickness. The Sn-Ta sheet was laminated with a Nb foil of the same thickness, and wound around a Nb-4at%Ta rod forming a Jelly Roll composite. The composite was encased in a Nb-4at%Ta tube, and then fabricated into a wire without intermediate annealing. The wire with no Cu addition to the Sn-Ta sheet and reacted at 900°C showed a non-Cu Jc of 100 A/mm2 at 23 T and 4.2 K. The non-Cu Jc of the wire at 2.1 K and 25 T reached 100 A/mm<2, the upper critical field of the wire being 28.4 T. A small amount of Cu addition to the Sn-Ta sheet appreciably reduced the reaction temperature, and produced a non-Cu Jc of 100 A/mm2 at 22 T and 4.2 K after the reaction at 800° C. Another process for fabricating multifilamentary-type (Nb, Ta)3 Sn conductors using ductile Sn-Ta/Nb composite is also being studied. [ABSTRACT FROM AUTHOR]

Bi2212 HTS bulk cylinders have been prepared by the diffusion process for current lead application. The Bi2212 HTS layer is synthesized through a diffusion reaction between a Sr-Ca-Cu oxide substrate and a Bi-Cu oxide coating with Ag addition. The HTS diffusion layer about 150 μm in thickness formed around the cylinder 37/29 mm in outside/inside diameter and 200 mm in length. The transport current of the cylindrical specimen exceeds 7,500 A at 4.2 K and self-field, which corresponds to a transport current density of 24,000 A/cm². The total heat toads, including heat leakage conducted through the cylindrical specimen between 4 K and 20 K and between 8 K and 40 K, are estimated to be 100 mW at 5,000 A and 300 mW at 3,000 A, respectively. Present Bi2212 HTS cylinders with large transport current as well as low joint resistance and thermal conductivity, seem to be promising as a current lead for superconducting magnets. [ABSTRACT FROM AUTHOR]

The mechanism of thick (Nb,Ta)[sub 3]Sn layer synthesis in the Ta-Sn core/Nb (Nb-Ta) sheath composite is studied. The diffusion of Nb from the sheath to the core seems to play a key roll to enhance that of Sn from the core to the sheath synthesizing (Nb,Ta)[sub 3]Sn layer. A simplified powder core process, in which Ta + Sn mixed powder is used instead of Ta-Sn reacted powder as the core, does not degrade the high-field performance of the (Nb,Ta)[sub 3]Sn conductor. A finer dispersion of Ta in the core is found to improve the J[sub c] of the conductor below 23 T. New Jelly Roll processed (Nb,Ta)[sub 3]Sn wires are fabricated using Sn-Ta sheets richer in Sn. The JR wires exhibit attractive high-field performance, and a small amount of Cu addition to the Sn-Ta sheet effectively decreases the reaction temperature. [ABSTRACT FROM AUTHOR]

MgB[sub 2] commercial powder was encased in a Ni tube and rolled into a monocore tape of about 5 mm in width and 0.3 mm in thickness. Different kinds of metal powder, i.e., In, Sn, Ag, Cu and Ni, were added to the MgB[sub 2] core. Addition of the low melting point metal powder, e.g., In and Sn, has been found to enhance significantly the J[sub c] value in MgB[sub 2] tapes. Annealing at a low temperature yields further increase in the J[sub c] of tapes with In and Sn addition. The enhancement in J[sub c] by the In addition and the low temperature annealing reaches a factor of 6-7. The J[sub c] of the tapes with 10vol% In addition, annealed at 200°C for 10 h is on the order of 10[sup 5] A/cm² at 4.2 K and 0.5 T. The TEM observation shows that In fills up the gaps among MgB[sub 2] grains. The additional annealing produces better impregnation of In in the core. The improvement in grain linkage seems to be the probable origin for the enhancement in J[sub c] by the In addition. The optimum amount of In addition to the MgB[sub 2] core is likely 10-15vol%. Ag, Cu and Ni powder addition yields no apparent effect on J[sub c] of PIT MgB[sub 2] tapes. [ABSTRACT FROM AUTHOR]

Examines the fabrication and performance of bismuth strontium copper oxide high temperature superconductor current leads. Diffusion reaction process; Transport current density; Heat load; Heat leakage; Thermal conductivity.

Discusses the application of high temperature superconductor (HTS) to a fusion plasma systems in the National Institute for Fusion Science. HTS application in the large current feedthrough to a superconducting coil; Development of HTS current lead; Development of superconducting magnetic levitation coil.

AbstractPolyamines are a ubiquitous group of amines that play diverse biological roles. In the anterior pituitary, intracellular polyamine levels are reported to show diurnal changes, although the biological significance remains to be elucidated. In this study, we examined the effects of polyamines on the transcriptional activity of the rat pro-opiomelanocortin (POMC) gene using AtT20PL, a clone of the AtT20 cell line in which an approximately 0.7 kb of the rat POMC 5′ promoter-luciferase fusion gene was stably incorporated. The results showed that three representative polyamines (putrescine, spermidine and spermine) all stimulated POMC promoter activity in a time- and dose-related manner, spermine showing the most potent effect (maximum approximate three-fold increase). This effect was not observed under treatment with actinomycin D, suggesting the effect of polyamine at the transcriptional level. On the other hand, methylglyoxal bis (guanylhydrazone), an inhibitor of polyamine synthesis, showed the opposite effect, further supporting the positive role of intracellular polyamines. Taken together, our findings suggest that polyamines are involved in the regulation of POMC gene expression (especially in terms of diurnal changes) in corticotroph cells. The precise molecular mechanisms of polyamine effects await further research. [ABSTRACT FROM AUTHOR]

Studies the high-field performance and structure of (Nb,Ta)[sub 3]Sn superconductors produced by Ta-Sn metallic alloy core. X-ray diffraction patterns of (Nb,Ta)[sub 3]Sn superconductors; Relative thickness ratio of quoted layers versus total tape thickness; Critical current versus magnetic field curve measurements.

Examines the Y-Ba-Cu-O semiconductor film growth on Y[sub 2]O[sub 3] buffered and nonbuffered SrTiO[sub 3] single crystals using precursor films including fluoride. Fabrication of flexible Yba[sub 2]Cu[sub 3]O[sub 7-x] coated conductors on a textured metal with oxide buffer layers.