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  • 1
    Electronic Resource
    Electronic Resource
    Properties of niobium–titanium superconducting wires with Nb artificial pinning centers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1640-1646 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Artificial pinning center (APC) Nb 47 wt % Ti composite wires containing 24 vol % Nb pins were characterized as the wire diameter was reduced. As the nominal pin diameter dp was reduced from 165 to 15 nm, the nominally round pins transformed into ribbons with a relatively wide distribution in thickness, as compared to the α-Ti ribbons in optimized, conventionally processed Nb 47 wt % Ti. The maximum in the bulk flux pinning force Fp of 25 GN/m3 (4.2 K, 2.5 T) occurred at dp=40 nm, for which the measured Nb ribbon thickness ranged from 1 to 16 nm. This Fp value was about one third higher than that found in the best conventional Nb 47 wt % Ti. The upper critical magnetic field Hc2, measured by magnetization, decreased from 10.3 to 9 T as the Nb pins became proximity-effect coupled to the matrix. To better compare APC and conventional wires, we measured the properties of the best APC wire at a reduced temperature so that its Hc2 was the same as Hc2(4.2 K) for Nb 47 wt % Ti. The peak value of Fp was then 36 GN/m3 at 3 T, almost twice the maximum value yet reported for conventional Nb–Ti (∼19 GN/m3 at 5 T). In spite of the pinning force curve remaining sharply peaked at lower fields, the equalized 5 T critical current density was 4600 A/mm2, some 25% higher than the best values of conventional Nb–Ti. These properties demonstrate the strong potential of APC composites. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362979
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  • 2
    Electronic Resource
    Electronic Resource
    Strongly enhanced critical current density in Nb 47 wt. % Ti having a highly aligned microstructure (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 2984-2986 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transport critical current density increased from 2610 to 5200 A/mm2 at 5 T, 4.2 K, when a round monofilament Nb 47 wt. % Ti composite was rolled to an aspect ratio of 9.7 and was tested with the broad face of the tape parallel to the field. This value exceeds the previous maximum of 3700 A/mm2 by about 50%. Transmission electron micrographs show that more than 90% of the α-Ti precipitates in the optimum-rolled filament are aligned within 10° of the broad face of the tape, whereas the precipitates had a random azimuthal orientation prior to rolling. The strong alignment caused the elementary pinning force to be greatly enhanced in the parallel-field orientation; however, in the orthogonal orientation the Jc fell to low values characteristic of conventional wires having no α-Ti flux pinning centers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104689
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  • 3
    Electronic Resource
    Electronic Resource
    Proximity effect depression of the critical temperature in two-phase Nb-Ti superconductors (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 688-689 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The superconducting critical temperature of high critical current density Nb-Ti composites has been measured at various stages in the critical current optimization process. This process involves heat treatment steps which cause precipitation of normal α-Ti and make the matrix more Nb rich. Tc rises from 9.1 to 9.5 K during this stage. The final optimization stage involves extensive wire drawing during which the α-Ti precipitates are reduced to less than a coherence length in thickness. This does not result in a reduction in Jc but Tc is found to fall from 9.44 to 8.7 K during this step. The depression of Tc is found to be in fair agreement with the predicted proximity effect suppression of Tc. Wires of optimum transport critical current density are seen to have Tc of around 9 K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.98335
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  • 4
    Electronic Resource
    Electronic Resource
    Artificial two-phase Nb-Ti nanostructures using powder metallurgy techniques (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 767-769 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Several techniques to form artifical high critical current density superconducting Nb-Ti nanostructures have been reported. A drawback to virtually all of these techniques is that they require fabrication strains of 30 or more to reduce the second phase pinning center to the optimum 1–10 nm size at which critical current densities of 103–104 A/mm2 are obtained. Here we describe a powder metallurgy process that yields 6020 A/mm2 at 2 T and 1470 A/mm2 at 5 T for an alloy with an upper critical field of ∼8 T within the same strain space (∼13) employed in the conventional Nb-Ti fabrication process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112224
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  • 5
    Electronic Resource
    Electronic Resource
    Periodic pin array at the fluxon lattice scale in a high-field superconducting wire (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1298-1300 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A periodic pin array has been made at dimensions approaching the diameter and spacing of the fluxon cores in an "island''-type of artificial pinning center superconducting composite wire. Gun-barrel drilling was used to precisely incorporate a hexagonal array of Nb 1.3 wt. % Ti pinning centers into an ingot of Nb 46.5 wt. % Ti, before extrusion and wire drawing. Transmission electron microscopy images showed little evidence of pin geometry alteration down to 100 nm pin diameter. At ∼30 nm effective pin diameter, the aspect ratio of the pins was 3–5, and the pin array retained its hexagonal geometry. Bulk pinning force curves had temperature-independent structure down to 15 nm effective pin diameter, suggestive of matching between fluxons and pins. Because of the uniform pin geometry, the maximum bulk pinning force exceeded that of the best conventional composites, even though the upper critical field and the volume fraction of pins were significantly lower.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111940
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  • 6
    Electronic Resource
    Electronic Resource
    Increased critical current density in Nb–Ti wires having Nb artificial pinning centers (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 901-903 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Artificial pinning center (APC) wires containing Nb 47 wt.% Ti with 24 vol.% of round Nb pins have produced very high critical current densities (Jc) which are attributed to a sharply defined, nanometer-scale Nb-pin array. By reducing both the number of warm extrusion steps from four to three and the temperature of the third extrusion from 650 °C to 250 °C, the degree of pin-matrix interdiffusion has been reduced and Jc values at all applied magnetic fields increased by 25–45% over those for a previous composite of almost identical design. The best wire achieved the very high Jc(5 T, 4.2 K) value of 4600 A/mm2. These results underscore the importance of the thermomechanical treatment in determining the maximum flux pinning properties of APC Nb–Ti wires. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118238
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  • 7
    Electronic Resource
    Electronic Resource
    Quantitative description of a high Jc Nb-Ti superconductor during its final optimization strain. I. Microstructure, Tc, Hc2, and resistivity (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 5962-5970 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A most important step in the critical current density (Jc) optimization of Nb-Ti is the large final drawing strain, in which α-Ti precipitates, initially approximately equiaxed and 100–200 nm in diameter, are drawn into ribbons, whose thickness (1–2 nm) is less than the superconducting coherence length [ξ (4.2 K)∼5 nm]. Using transmission electron microscopy, the precipitate thickness, spacing, cross-sectional area, and circumference were measured over the whole final drawing strain range. Each of these parameters was found to have a simple power dependence on the wire diameter. Tc, Hc2, and the resistivity (ρn) were also change considerably during the refinement of the precipitates. Directly after precipitation, Tc increased, and (dHc2/dT)Tc and ρn were reduced from the single-phase values. Drawing the wire returned these parameters to their single-phase values, as the precipitate thickness was reduced to less than ξ. This observation explains a long-standing peculiarity in this system, namely that the optimum Hc2 of high Jc conductors occurs for a composition close to Nb 46 wt.% Ti, even when the precipitation of 18 vol % of α-Ti shifts the matrix composition to a Nb-rich composition of theoretically lower Hc2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343624
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  • 8
    Electronic Resource
    Electronic Resource
    Enrichment enhances the expression of sgk, a glucocorticoid-induced gene, and facilitates spatial learning through glutamate AMPA receptor mediation (2003)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 18 (2003), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We have previously demonstrated that the serum and glucocorticoid-inducible kinase (sgk) gene plays a causal role in facilitating memory performance in rats. Environment enrichment is known to facilitate spatial learning. We therefore examined the effect of enrichment on sgk expression. We also examined the role of sgk in spatial and nonspatial learning and the regulation of sgk expression by activation of different glutamate receptors. Both real-time polymerase chain reaction and Western blot analyses revealed that enrichment training preferentially increased sgk mRNA and protein levels in the hippocampus. Transfection of sgk mutant DNA to the hippocampal CA1 area markedly impaired spatial learning, fear-conditioning learning and novel object-recognition learning in rats, but enrichment training effectively reversed these learning deficits. Meanwhile, S422A mutant DNA transfection prevented enrichment-induced spatial learning facilitation. In studying glutamate receptor regulation of sgk expression, we found that blockade of N-methyl-d-aspartate (NMDA) receptors in general, and the NR2B subunit in particular both effectively blocked enrichment-induced spatial learning facilitation, but they did not block enrichment-induced sgk expression. Upon various glutamate agonist infusions, only α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) increased sgk mRNA levels significantly in the hippocampus. Furthermore, blockade of AMPA receptors effectively blocked both enrichment-induced spatial learning facilitation and sgk expression. These results indicate that there is a dissociation between NMDA receptor activation and sgk expression. Enrichment enhanced spatial learning through both NMDA and AMPA receptor activation, whereas enrichment-induced sgk expression is specifically mediated through AMPA receptors. These results suggest that sgk could serve as a novel molecular mechanism, in addition to the NMDA receptor NR2B, underlying enrichment-induced learning facilitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1460-9568.2003.03032.x
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  • 9
    Electronic Resource
    Electronic Resource
    Plants lacking the main light-harvesting complex retain photosystem II macro-organization (2003)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 421 (2003), S. 648-652 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Photosystem II (PSII) is a key component of photosynthesis, the process of converting sunlight into the chemical energy of life. In plant cells, it forms a unique oligomeric macrostructure in membranes of the chloroplasts. Several light-harvesting antenna complexes are organized precisely in ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature01344
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  • 10
    Electronic Resource
    Electronic Resource
    Docetaxel in the community setting: An analysis of 377 breast cancer patients treated with docetaxel (Taxotere®) in the UK (1999)
    Springer
    Annals of oncology 10 (1999), S. 205-210 
    Details
    ISSN: 1569-8041
    Keywords: breast cancer ; docetaxel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Given as first- or second-line chemotherapy, docetaxel appears to have great potential in advanced breast cancer. Patients and methods: Three hundred and seventy-seven locally advanced or metastatic breast cancer patients received docetaxel (Taxotere®) as part of a named patient programme under the care of 108 oncologists from 61 cancer units across the UK. The recommended starting dose was 100 mg/m2, but patients at higher risk of toxicity started at 75 mg/m2. All patients received corticosteroid premedication. The modal number of prior chemotherapy regimens was 2 (range 1–7), 342 patients (91%) had at least one prior anthracycline-based regimen. Results: Response was graded according to the managing clinician's best judgement without formal criteria. The overall response rate (ORR) was 46% among the 331 evaluable patients, 46% among the 299 patients who were 'anthracycline resistant' and 35% among the 82 patients who were 'anthracycline refractory' (progressive disease being the best response obtained to the most recent anthracycline containing regimen). One hundred and ninety-three patients started at the full dose of 100 mg/m2 with an ORR of 55% and 129 started at 75 mg/m2 with an ORR of 33%. In October 1997, some two years after the programme had started, 26 of 377 patients were still alive, although no complete remissions have lasted to this date. Kaplan–Meier survival analysis yielded a median survival of 194 days (95% CI: 178–218 days). Haematological parameters were checked before each course of docetaxel and additionally as clinically indicated. The safety data confirmed that docetaxel has a manageable, predictable side effect profile; 29 of 377 (7.7%) patients were hospitalised as a result of neutropenic sepsis. Conclusions: The results of this named patient programme over a two year timespan confirm that docetaxel is an effective chemotherapy option in patients with locally advanced and/or metastatic breast cancer, including an 'anthracycline refractory' population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008370930599
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