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Notes: The coupled interaction of vorticity ω and rate-of-strain S in homogeneous sheared turbulence is investigated using direct numerical simulation. Conditional sampling and comparison with linear simulations reveal various aspects of the structure and dynamics. Due to the influence of the imposed ω and S, distinct directional features develop. Initial stretching of fluctuating ω by mean extensional strain and the presence of mean vorticity establish a predominant misalignment of ω with respect to the principal axes of S. The associated locally induced rotation of the S axes results in preferred orientations in ω and S. In high amplitude rotation-dominated regions of the flow, distinct characteristics are exhibited by the pressure Hessian Π due to the presence of small-scale spatial structure. Nonlocally induced S axes rotation through Π tends to counteract locally induced rotation in these regions. These features are absent in the linear flow which suggests a lack of spatial coherence in the corresponding intense ω2 regions. High amplitude strain-dominated and comparable rotation-strain regions are also considered. In general, the high amplitude conditional samples capture the main features of the flow. The underlying behavior of ω and S is essentially the same as in isotropic turbulence; the directional preferences observed in shear flow demonstrate the physical implications of the associated mechanisms. Although there is greater directional variation in flows with high Reλ/Sh, results indicate the significance of the persistence of mean shear. © 2000 American Institute of Physics.

Notes: The structure and dynamics of stably stratified homogeneous sheared turbulence is investigated in terms of the triadic interaction of vorticity ω, rate-of-strain S, and scalar (density fluctuation) gradient G≡∇ρ′. Results of direct numerical simulations are presented. Due to the presence of the mean velocity and scalar gradients, distinct directional preferences develop which affect the dynamics of the flow. The triadic interaction is described in terms of the direct coupling of primary mechanism pairs and influential secondary effects. Interaction of ω and S is characterized by the coupling of vortex stretching and locally-induced rotation of the S axes. Due to the intrinsic directionality of baroclinic torque, the generated ω acts to impede S axes rotation. Interaction of ω and G involves an inherent negative feedback between baroclinic torque and reorientation of G by ω. This causes baroclinic torque to act as a sink which promotes decay of ω2. Interaction of S and G is characterized by a positive feedback between differential acceleration and gradient amplification by compressive straining which promotes persistence in vertical G. In high-amplitude, rotation-dominated regions of the flow, differential acceleration effects enhance the attenuation of vertical ω while shear and baroclinic torque tend to maintain horizontal ω. This leads to a predominance of horizontal ω in these regions which manifests itself as collapsed vortex structures. As the flow develops, the third invariant of the velocity gradient tensor tends towards zero indicating locally two-dimensional flow. © 2000 American Institute of Physics.

Notes: Turbulent mixing of an inhomogeneous passive scalar field is studied in the context of a nonpremixed reacting flow. Direct numerical simulations of an initial steplike scalar field subjected to homogeneous sheared turbulence have been performed and the results compared with those of the case of decaying isotropic turbulence. For both flow conditions, the gradient of the conserved scalar tends to align itself with the axis of the most compressive strain rate and orthogonal to the local vorticity. The magnitude of the scalar gradient is directly influenced by the local strain rate while its orientation is controlled by the local vorticity. Because of the directional features of sheared turbulence, the orientation of the scalar gradient is more ordered than in isotropic turbulence. In addition, the magnitude of vorticity indirectly affects that of the scalar gradient through strain-rate amplification by vortex stretching. In both flows, regions of high scalar-gradient magnitude or scalar dissipation (and therefore high reaction rates) tend to exist as sheets in the vicinity of sheetlike vortex structures of moderate to high vorticity. The probability density function (pdf) of the the scalar dissipation rate εF exhibits a nearly lognormal distribution with a slight negative skewness for both isotropic and sheared turbulence.

Notes: The characteristics of Ag-(Mg,Ni) and Ag-Mn alloys as substrate materials for Bi2Sr2CaCu2Ox (Bi-2212) tapes and their influence on the superconducting properties were studied. Alloying with Mg+Ni or Mn drastically decreased the grain size of Ag after heat treatment. The additives in Ag-(Mg,Ni) and Ag-Mn alloys were oxidized during heat treatment in air. Both the fine grain structure and the internal oxidation of the additives increased the mechanical strength of the Ag alloys. Both alloys were 3–6 times stronger than pure Ag. The superconducting properties of Bi-2212 prepared on these Ag alloys were slightly degraded; however the critical current densities at 4.2 K in 8 T were still well over 104 A/cm2.

Notes: Oxide superconductor tape with Ag-Au sheath was studied for current leads. A 100-cm-long current lead of 1000 A with 0.2 W/kA heat leakage was designed using Ag-11 at. % Au alloy sheath with low thermal conductivity. The overall current density of the superconducting tape is required to be 350–770 A/cm2 at 77 K when the superconductor cross-section ratio in the tape is 0.35–0.7. Bi-Pb-Sr-Ca-Cu-O superconducting tape with Ag-11 at. % Au alloy sheath was fabricated and the critical current density Jc was measured. The overall-Jc was 1700 A/cm2 at 77 K under 0 T. The possibility of the current lead of 1000 A under 0.28 T with 0.2 W/kA was made clear.

Notes: Ag-sheathed Bi2Sr2Ca1Cu2Ox(Bi-2212) tapes with various oxide superconductor core (SC-core) thicknesses, SC-core ratios (SC-core area to overall cross-sectional area), and tape configurations were prepared by a partial melting and slow cooling process. For single-core tapes the critical current density, Jc(core), for SC-core, increases with decreasing SC-core thickness, due to the highly aligned Bi-2212 grains, and the highest Jc(core) of 1.4×105 A/cm2 at 4.2 K in 10 T is achieved at a core thickness of 15 μm. Furthermore, the Jc(core) increases with increasing SC-core ratio (i.e., with decreasing Ag-sheath thickness). From the practical point of view, high Jc(overall) as well as high critical current (Ic) is more important than Jc(core). This requirement is attained by the double-tube method, which shows the highest Jc(overall) value of 3.0×104 A/cm2 at 4.2 K in 10 T. In the tape fabrication process, the slow heating rate just below the partial melting becomes important, because oxygen released from the SC-core during heating makes void swelling in the Ag sheath and leads to the degradation of Jc.

Notes: The influence of Ag-Au and Ag-Cu alloy substrates on the microstructure and superconducting properties of Bi2Sr2CaCu2Ox (Bi-2212) was studied. The critical current density (Jc) of Bi-2212/(Ag-Au) was not degraded by increasing the Au content of the Ag-Au alloy, while the Jc of Bi-2212/(Ag-Cu) was drastically degraded by increasing the Cu content of the Ag-Cu alloy. The microstructure of Bi-2212 on the Ag-Au alloy was uniform and no precipitates were observed. The Jc degradation of Bi-2212 in contact with the Ag-Cu alloy was understood by the fact that Cu absorption of Bi-2212 from the Ag-Cu alloys changed the composition of the oxide layer. Ag-Au alloys are superior substrate materials for Bi-2212 for power current leads for superconducting magnets, taking into account their low thermal conductivity.

Notes: Clubroot disease caused by Plasmodiophora brassicae is one of the major diseases of Brassica crops, often devastating to the cultivation of cruciferous crops in temperate regions. In a previous study (Moriguchi et al. 1999) identified three major quantitative trait loci (QTLs) for clubroot resistance, each in a separate linkage group, in a population derived from a cross between a clubroot-susceptible inbred cabbage line, Y2A and a resistant inbred kale line, K269. In this study, the original random amplified polymorphic DNA (RAPD) and restriction fragment length polymorphism (RFLP) markers were converted into sequence-characterized amplified region (SCAR) markers to facilitate large-scale marker-assisted screening of clubroot resistance in cabbage breeding. Of 15 RAPD markers closely linked to the three QTLs, nine SCARs were developed as dominant markers after cloning and sequencing. In addition, two RAPD markers were converted into co-dominant cleaved amplified polymorphic sequence (CAPS) markers, and one RFLP marker out of three tested was converted to a dominant SCAR marker. The effect of selection for resistance by the improved markers was evaluated in progeny plants in the F2 and F3. A total of 138 F2 plants were genotyped with nine SCARs and 121 well-distributed makers consisting of 98 RAPD, 19 RFLP, two isozymes, and two morphological markers in order to estimate the level of resistance and the proportion of undesirable alleles from the kale in non-target areas in each of the F2 populations. An F2 plant, YK118, had kale alleles at QTL1, QTL3 and QTL9. Three F2 plants, namely, YK107, YK25 and YK51 had kale alleles at only QTL1, QTL3 and QTL9, respectively. These F2 plants were selected for their low proportion of alleles derived from kale in non-target regions. YK118, like the resistant kale parent, expressed very high resistance to three field isolates of Plasmodiophora brassicae, whereas the mean disease index in the F2 and F3 plants carrying only single QTLs was intermediate. The QTLs showed no differential response to the isolates. These plants with improved resistance will be useful as parental inbred lines for F1 hybrids.

Notes: A case of uterine carcinosarcoma with extensive neuroectodermal differentiation occurring in a 54-year-old woman is described. Microscopically, the endometrial tumour was predominantly composed of a sheet-like proliferation of small- and medium-sized cells. These cells were characterized by fibrillary cytoplasmic processes, rosette-like formations, perivascular palisading patterns, and immunoreactivity for glial fibrillary acidic protein, synaptophysin, leu 7 and neuron-specific enolase. In limited areas, features of conventional carcinosarcoma, including squamous cell carcinoma, leiomyosarcoma and islands of the above mentioned small-to medium-sized cells that were intermingled, were observed. The tumour was aneuploid by flow cytometry. The patient is alive with tumour for three months. It is suggested that at least some cases of uterine primitive neuroectodermal tumour may be explained by one-sided neuroectodermal development within a carcinosarcoma.