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BACKGROUND AND PURPOSE The rate at which the chance of a good outcome of endovascular stroke therapy (EVT) decays with time when eligible patients are selected by baseline diffusion-weighted magnetic resonance imaging (DWI-MRI) and whether ischaemic core size affects this rate remain to be investigated. METHODS This study analyses a prospective multicentre registry of stroke patients treated with EVT based on pretreatment DWI-MRI that was categorized into three groups: small [Diffusion-Weighted Imaging Alberta Stroke Program Early Computed Tomography Score (DWI-ASPECTS)] (8-10), moderate (5-7) and large (

Cube textured Ni substrate were fabricated for YBCO coated conductors from the initial specimens prepared by powder metallurgy (P/M) and casting and the effects of annealing temperature and reduction ratio on texture formation and microstructural evolutio were evaluated. The initial specimens were rolled by 98.6% and 99.2% reduction ratio and then annealed in the temperature range of 600°C to 1200°C. The microstructure and texture were evaluated by optical microscopy and X-ray pole-figure analysis. We observed that microstructure of the initial specimen varied with preparation methods.Texture analysis indicated that a strong cube texture formed for substrate made by P/M, and the degree of texture did not significantly vary with annealing temperature of 600°C~1100°C. On the other hand, the texture of substrate made by casting was more dependent on the annealing temperature and twin texture ({221}) and several minor texture components started to form at 1000°C. In addition, the texture of substrate made by P/M was significantly dependent on the reduction ratio.

This paper presents the influence of current distribution on AC transport current loss in multi-strand high-temperature superconductor (HTS) tapes. The current-distribution-dependent-AC loss is analyzed by introducing a current distribution parameter. We calculated AC loss of multi-strand HTS tapes numerically and performed AC loss measurements as well. Though the effect of current distribution on AC transport current loss is relatively insignificant for a low applied transport current, the effect of nonuniform current distribution seriously increases AC loss for a high applied transport current. The AC loss measurement method used in this paper is also confirmed by comparison with numerical results: the experimental and computational results showed good agreement for various current distribution parameters

We fabricated Bi-2223/Ag jointed tape and evaluated its current carrying capacity and joint resistance at 77.3 K as a function of the contact length. The tapes were jointed by the conventional resistive joint method with 40Pb-60Sn solder as an insert material and their joint resistance was measured by two different techniques, i.e., the standard four-probe and field decay methods. It was observed that the current carrying capacity and joint resistance were significantly dependent on the contact length. As the contact length increased, the current carrying capacity improved and increased to the level of critical current in the unjoined tape at the contact length of 5 cm. On the other hand, the joint resistance linearly decreased as the contact length increased. In addition, the joint resistances measured by the two methods were similar to each other (7.3times10-9 Omega~8.0times10-9 Omega), indicating that the standard four-probe method maintained a moderate degree of accuracy at the level of resistance of 10-9 Omega

We fabricated cube textured Ni substrates for YBCO coated conductors from the initial specimens prepared by powder metallurgy (P/M) and casting and evaluated the effects of annealing temperature on microstructural evolution and texture formation. To characterize the roles of the two preparation methods, the initial specimens were prepared to be of the same size and experienced the same rolling conditions, and were then annealed in the temperature range of 600/spl deg/C to 1200/spl deg/C. The texture was evaluated by X-ray pole-figure analysis and transmission electron microscopy (TEM). The texture analysis indicated that a strong cube texture formed for the substrate made by P/M and this texture did not vary significantly with annealing temperature in the range of 600-1200/spl deg/C. On the other hand, the texture of the substrate made by casting was more dependent on the annealing temperature, and a twin texture ({221} ) and several minor texture components began to form at 1000/spl deg/C. Microstructural observation showed that the morphology of deformation band together with micro-band in the as-rolled tape prepared by P/M was more homogeneous and of higher density than that produced by casting, resulting in a strong cube texture in wider range of annealing temperatures and a finer microstructure after recrystallization.

This paper investigates the magnetization loss of stacked Bi-2223/Ag tapes. A numerical code was developed to estimate the magnetization loss of stacked tapes in parallel and perpendicular external magnetic fields. To calculate magnetization loss and current distribution across the tapes, we used magnetic field dependent current-voltage characteristics of a tape. The numerically calculated result showed good agreement with the measured magnetization loss in a tape. In a perpendicular field, it was observed that the loss per unit volume decreased as the stacking number increased because of the screening current across the tapes. In a parallel field, the loss per unit volume remained virtually unchanged as the stacking number increased. The influence of stacking effect on magnetization loss is addressed with the induced current distribution obtained from numerical calculation.

We fabricated 55-filament Bi-2223/Ag tape and evaluated the dependence of critical current (I/sub c/) and index n in an external magnetic field up to 30 T at 4.2 K, in order to explore the possible application for a magnet in persistent current mode. I/sub c/ and index n were characterized as a function of temperature and the magnitude and orientation of the magnetic field by increasing and decreasing field. It was observed that I/sub c/ was dependent on the magnitude and orientation of the magnetic field. The I/sub c/ decreased exponentially as the field increased; in a parallel and increasing field, I/sub c/ was 128 A at 30 T, which is approximately 40% of the I/sub c/ in self-field. On the other hand, index n was not significantly dependent on the field up to 30 T, nor did it vary significantly on increasing or decreasing field; the n value in the range of 0.1/spl sim/1 /spl mu/V/cm was 23.0/spl plusmn/5.2 and 27.8/spl plusmn/8.0 on increasing and decreasing field, respectively, in the range of 0/spl sim/30 T. In addition, we observed that local I/sub c/ and index n of a long length of tape (4.2 m) were dispersed over a wide range and that the variation of each of these two values with the position of the tape was similar, suggesting that these properties depend on the microstructural uniformity.

We fabricated the textured Ni substrate and evaluated the effects of processing variables on microstructural evolution and texture transformation. Ni-rods as an initial specimen were prepared by two different methods, i.e., powder metallurgy (P/M) and plasma arc melting (PAM). To evaluate the effect of two preparation methods, the initial specimens were prepared to be of same size and experienced by same rolling conditions. The texture of the substrate was characterized by pole-figure and surface condition was evaluated by atomic force microscopy. It was observed that the texture of substrate made by P/M did not significantly varied with annealing temperature of 800 /spl sim/ 1200/spl deg/C and the full-width at half-maximums (FWHM) of both in-plane and out-of-plane were 9/spl deg/ /spl sim/ 10/spl deg/. On the other hand, the texture of substrate made by PAM was more dependent on the annealing temperature and the FWHM of in-plane texture was 9/spl deg/ /spl sim/ 13/spl deg/ at the temperature range. In addition, twin texture, (221), was formed as the temperature increased further. OM micrographs showed that the grain size of substrate made byP/M was smaller than that made by PAM and this difference was correlated to the microstructure of initial specimens.

We joined 19-multifilamentary Bi-2223 superconductor tapes and fabricated double-pancake coils by using resistive- and superconducting-joint methods. The critical current ratio (CCR) of the jointed tape and the decay characteristics, joint resistance, and n-value of the pancake coils were evaluated. The joint resistance of the coils was characterized by the field decay technique. It was observed that the CCR was higher in the joined tape made by the resistive-joint method, compared to that by the superconducting-joint method. On the other hand, joint resistance was measured to be 4 orders of magnitude smaller in the superconducting-joint coil; approximately 40% of critical current was retained in the persistent current mode and the joint resistance was 0.18 n/spl Omega/. Better and longer retention of the magnetic field in the superconducting-joint coil is believed to be due to the direct connection between the superconducting cores.

Superconducting motors have high efficiency as well as reduced size and weight. In superconducting motors, the field winding is composed of HTS tapes (Bi-2223) without any iron core because of magnetic saturation, and the current in the field winding is limited by the maximum magnetic field in the field winding. To enhance the performance of superconducting motor, we need to maximize the critical current of field winding as much as possible. This paper introduces the shape optimization method with the constraint of HTS characteristic (I/sub c/-B curve), and proposes a shape that improves the critical current of the field winding. Finite element analysis and discrete sensitivity approach are used for calculating the magnetic field of coil and shape optimization.

A new design scheme is developed to use the topology optimization method in the superconducting system. The critical current condition is considered in the sensitivity calculation for accurate analysis and design of the system. The density method is used to model the design space, and the normalized density of superconducting filament in each cell is used as design variables. The designs of SMES (superconducting magnetic energy storage) coil and MRI (magnetic resonance imaging) coil are given as numerical examples.

We evaluated the effect of alloying additions to Ag on thermal conductivity and mechanical properties of Ag-alloy sheathed Bi-2223 (BSCCO) superconductor tape. The tapes were made with combinations of Ag alloys such as Ag-Mg, Ag-Sb, and Ag-Au for inner and outer sheath. Thermal conductivity of the tapes was evaluated by using thermal integral method at 10-120 K. It was observed that the addition of alloys reduced remarkably thermal conductivity and improved mechanical strength. The thermal conductivity for Ag-Mg, Ag-Sb, and Ag-Au at 40 K was measured to be 411.4, 142.3, and 109.7 W/(m/spl middot/K), respectively, which is approximately 2 to 9 times lower than that of Ag (1004.6 W/(m/spl middot/K)). In addition, the thermal conductivity of alloy-sheathed tape significantly depended on their thermal conductivity of sheath materials. For Ag-alloy sheathed tapes, the thermal conductivity was much lower (i.e., 5 -18 times lower) than that of the Ag sheathed tape The mechanical property of alloy-sheathed tape was also evaluated and correlated to the microstructural evolution.

The core–shell type nanoparticles composed of poly(γ-benzyl- l -glutamate) (PBLG) as hydrophobic inner core and poly(ethylene oxide) (PEO) as hydrophilic outer shell are formed from organic solution of the block copolymer by the diafiltration method. Amphiphilic merocyanine dyes (MDs) were self-assembled in the self-assembled copolymeric nanoparticles which provide a chiral microenvironment as red-shifted aggregates (J-aggregates). Also, the circular dichroism (CD) of MD was induced in the self-assembled copolymeric nanoparticles with negative and positive Cotton effect in the range of 575–625 nm whose crossing point matched λmax in the UV region of MD. This result indicated that the PBLG chains and MDs were associated together to form spherical nanoparticles by hydrophobic interaction and the chiral PBLG core in the self-assembled copolymeric nanoparticles induced CD of J-aggregated MD. The helix sense of induced circular dichroism (ICD) of MD in the copolymeric nanoparticles was affected by the helix sense of PBLG in the copolymeric nanoparticles.

The quench characteristics of Bi-2223 single and four double pancake coils operating at liquid helium temperature were investigated based on experiments and numerical simulations. Broad resistive transition was observed in the double pancake coils. The Bi-2223 double pancake coil operating at liquid helium showed a slow normal zone propagation velocity. The stability margin of the coil was confirmed to be high because of the low operating temperature and a good cooling condition. The quench characteristics of a four double pancake coil system was simulated by a numerical method. It is clear that the protection resistance has a great influence on the current decay, transient voltage and hot-spot temperature.

The role of Ag additions in the microstructural evolution and related mechanical properties of YBCO has been studied. Various amounts of Ag have been added to YBCO by two different mixing techniques, i.e. in the form of metallic Ag powder and solution. The strength and fracture toughness of YBCO specimen increased with increasing Ag content, probably because of strengthening mechanisms resulting from Ag addition. In addition, YBCO-Ag composites showed higher values of strength and fracture toughness when Ag was added in the form of solution compared with those when it was added in the form of metallic Ag powder. Specifically, an addition of 10 vol% Ag, made by mixing with metallic Ag powder, increased strength from 88 to 116 MPa and fracture toughness from 1.6 to . Corresponding improvements in strength and fracture toughness were 128 MPa and , respectively, when YBCO was mixed with solution. The better mechanical properties of the YBCO-Ag specimen mixed by the solution method are believed to be due to the microstructure of more finely and uniformly distributed Ag particles. Furthermore, addition of Ag did not have an adverse effect on the critical current density of YBCO superconductors.

Over a period of ten months, a 15 m-long, 50 mm-aperture superconducting SSC Collider dipole was taken through a series of thermal and power cycles to check for changes in performance. One quench below operating current was experienced during this period. Small changes in the coil preload and certain harmonics were observed. >

Eighteen 5-cm-aperture, 15-m-long Superconducting Super Collider (SSC) dipole magnet prototypes have been produced and cold tested. On each prototype, the dependence of harmonic field coefficients on magnetic current was measured as part of a study of the magnetic field quality. For most of the magnets, the observed behavior conforms to what can be expected from the effects of persistent magnetization currents and iron yoke saturation. A few prototypes, however, exhibited anomalies during current ramp at 4 A/s which can be attributed to large cable eddy currents. >

The authors summarize the mechanical performance of the most recent 5-cm-aperture, 15-m-long SSC dipole magnet prototypes. The magnets were produced at Brookhaven National Laboratory (BNL) and Fermi National Accelerator Laboratory (FNAL) under contract with the Superconducting Super Collider Laboratory (SSCL). The BNL magnets rely on a horizontally split yoke with collared ends, while the FNAL magnets rely on a vertically split yoke with collet-style end clamps. Magnets of both designs are equipped with strain gauges enabling measurement of the azimuthal pressures exerted by the coils against the collar poles as well as the axial forces transmitted from the coil ends to the end plates. A comparison of the mechanical behaviors measured by the strain gauges is presented. How the behavior of the 5-cm-aperture magnets compares to that of the 4-cm-aperture prototypes is also discussed. >

The quench performance and ramp rate sensitivity of 18 5-cm-aperture, 15-m-long Superconducting Super Collider (SSC) dipole magnet prototypes are discussed. All the magnets appear to reach a quench plateau near their extrapolated short sample current limit and well in excess of the operating current with very little training. Most of the magnets, however, exhibit a dramatic degradation of their quench current as a function of ramp rate, which, for the most part, can be attributed to large cable eddy currents. >

This paper assesses the potential of magnetically modified zeolite (MMZ) for ammonia removal from aqueous solution. The effects of relevant parameters such as contact time, pH and initial ammonia concentration were examined. The results show that ammonium ion removal by MMZ occurs rapidly within the first five minutes, pH has an effect on ammonium ion removal efficiency, and the ammonium ion removal capacity of MMZ increases with increase in initial ammonium ion concentration. The Langmuir and Freundlich adsorption isotherms were used to determine the adsorption characteristics. Ammonium‐laden MMZ seems to be regenerated completely by sodium chloride solution at pH 11–12.

This paper investigated the chemical, mechanical, and structural properties of carbon nanotubes by altering their contents in order to be used as component parts for semiconductive shields used in underground power transmission cables. A multi luminescence spectrometer MLA-GOLDS was used to investigate the chemical properties of specimens. In addition, a density meter EW-200SG was used to investigate the mechanical properties of specimens. A FE-SEM S-4300 meter by Hitachi was used to apply dispersions of CNT (Carbon nanotube). As a result, the cl intensity, showing the effects of oxidation, decreased in CNT by approximately 1[wt%], and the density values for semiconductive shield materials with CNT and EEA (Ethylene Ethyl Acrylate) was lower than commercial semiconductive shield materials. Furthermore, dispersion properties showed increases according to the increase in CNT ratio. These properties demonstrated the best conditions at 5wt%. Therefore, it was evident that such exceptional chemical, mechanical, and structural properties could be improved with just a small amount of CNT.

Chitosan, a natural cationic polysaccharide, is a candidate non-viral vector for gene delivery because of its high positive charges and low cytotoxicity. In this study, low molecular weight chitosan (LMWC, molecular weight of 22 kDa) was characterized and evaluated as a gene carrier.Plasmid/LMWC complex was analyzed in 1% agarose gel electrophoresis. To confirm that the LMWC protected plasmids from nuclease. DNase I protection assays were performed. pSV-beta-galactosidase plasmid/LMWC complex was transfected into 293T cells and transfection efficiency was evaluated by beta-galactosidase assay. Cytotoxicity of LMWC was determined by MTT assay.Unlike high molecular weight chitosan (HMWC), LMWC is highly water soluble, and can form complex with plasmids in physiological buffer. The plasmid DNA was completely retarded at a weight ratio of 1:2 (plasmid:LMWC) in 1% agarose gel. DNase I protection assay showed that plasmids were protected from DNase-I over 60 min. The most efficient transfection was obtained at a weight ratio of 1:3 (plasmid:LMWC). The transfection efficiency of LMWC was significantly higher than naked DNA and higher than poly-L-lysine (PLL). MTT assay showed that LMWC was less cytotoxic than PLL.LMWC is non-toxic and has higher transfection efficiency than PLL. Therefore, LMWC will be useful in the development of safe gene carriers.

During 1992 at Fermilab, a series of nine 50-mm-aperture, 15-m-long, SSC superconducting dipole magnets, designed jointly by Fermilab, Brookhaven National Laboratory, and the SSC Laboratory, have been built and successfully cold tested. Seven of these dipole magnets, designated for the Accelerator System String Test (ASST) carried out at SSCL in Dallas, were assembled at Fermilab by General Dynamics personnel, and have achieved the nominal operating current level without significant training.1,2 In addition, a series of four R&D magnets (DCA320 323) were manufactured at Fermilab to test an alternative insulation schemes. In this paper we present the quench performance of these four R&D magnets, which were cold tested at the Fermilab Magnet Test Facility at nominal temperatures of 4.35 K, 3.85 K, and 3.50 K. An extended characterization test was performed on one of these magnets (DCA322). During this test the magnet was successfully cooled down to superfluid He temperature (1.8 K) and reached a field B ≥ 9.5 T.

In this paper we present results of quench testing of full length SSC dipole magnets at Fermilab. The data are from the first six of a series of thirteen 15 m long, 50 mm aperture SSC dipole magnets which are being built and tested at Fermilab. These magnets were designed jointly by Fermilab, Brookhaven Laboratory, Lawrence Berkeley Laboratory and the SSC Laboratory. Among the major goals for this series of magnets are to transfer magnet production technology to the lead vendor for the Collider Dipole Magnet, the General Dynamics Corporation, and to demonstrate industrial production by the vendor. The first magnet in the series, DCA311, was built by Fermilab technicians to establish assembly procedures. The second magnet, DCA312, was the “technology transfer magnet and was built jointly by Fermilab and General Dynamics technicians. The next seven, DCA313-319 are being built by General Dynamics personnel using Fermilab facilities and procedures. However, Fermilab personnel still operate the major tooling, provide the welders, perform assembly of items that would not be part of production magnets (e.g. voltage taps), and oversee the QA program. Five of these 7 GD-built magnets will be used in the Accelerator Systems String Test (ASST) to be carried out in Dallas later this year. The last four magnets, DCA320-323, are being built by Fermilab alone.”

A series of full-scale demonstration SSC collider dipole magnets were built for the ASST (Accelerator System String Test). These magnets, DCA311 through DCA319, have 50 mm aperture and 15 m magnetic length with 6.6 Tesla uniform field. For the support structure of the W6733B cross section[1], the Fermilab design uses a vertical split[2] in the yoke. The end sections of the magnet have solid spacers and are supported by collet clamps[3]. The splices between inner and outer coils are made in preforms which lie outside of the high field region. The magnets were produced in pipeline fashion with no intentional major changes between magnets. As a part of the technology transfer program, the last 7 magnets were built by General Dynamics personnel using the magnet construction facilities of Fermilab, while the first two magnets were built entirely by Fermilab personnel.

Eight 5-cm-aperture, 15-m-long dipole magnet prototypes have been produced and cold-tested at Brookhaven National Laboratory (BNL) and Fermi National Accelerator Laboratory (FNAL) under contract with the Superconducting Super Collider Laboratory (SSCL). These magnets are the last phase of an R&D program aimed at demonstrating the feasibility of the 5-cm-aperture designs developed by BNL and FNAL. They are also used as vehicles to transfer technology from the National Laboratories to the collider dipole magnet contractors. The BNL magnets, which rely on an horizontally-split yoke, and the FNAL magnets, which rely on a vertically-split yoke, perform according to their somewhat different mechanical designs and have equally successful quench performance.

This paper reports results of field quality measurements of the initial 15 m-long, 50 mm-aperture SSC Collider dipoles tested at Brookhaven National Laboratory and Fermi National Laboratory. These data include multipole coefficients and the dipole angle at room temperature and 4.35 K, 4.35 K integral field measurements, and time-dependent effects. Systematic uncertainties are also discussed.