Numerical calculation of current density distributions in high temperature superconducting tapes with finite thickness in self field and external field

The current density distribution of high temperature superconducting (HTS) tapes is modeled for the combined case of an alternating self and applied magnetic field. This numerical analysis is based on the two-dimensional Poisson equation for the vector potential. A one-dimensional current (z-direction) and a one-dimensional applied field (y-direction) are assumed. The vector potential is rewritten into an equation of motion for the current density J(x,y,t). The model covers the finite thickness of the conductor and an n-power E–J relation. The magnetic field dependence of J_c is also included in this E–J relation. A time-dependent two-dimensional current distribution that is influenced by the aspect ratio of the conductor and the material properties in E=f(J,B) is calculated numerically. The numerical results are compared with the experimental results for the AC loss of a tape driven by a transport current. Finally, a total AC loss factor is given for two cases in magnetic field direction, perpendicular and parallel to the conductor broad side.     

A synthetic approach to the phorboxazoles – A strategy for the synthesis of the C1–C19 polyketide fragment

A synthetic approach to the C1–C19 polyketide fragment of the phorboxazoles is disclosed here. While an initial two-directional approach was efficient, it did not proceed in a high enough yield to justify moving forward. A subsequent successful strategy for the generation of the C11–C15 pyrans of both of the phorboxazoles was achieved, and the installation of the C9 stereocenter was able to be demonstrated. Furthermore, an efficient route for the preparation of the C1–C8 fragment with suitable functionality to allow for elaboration into the complete C1–C19 fragment, with the capricious C2–C3 Z-geometry installed, was also achieved.     

A novel stopped flow injection-amperometric procedure for the determination of chlorate

A novel stopped flow injection—amperometric (sFI-Amp) procedure for determination of chlorate has been developed. The reaction of chlorate with excess potassium iodide and hydrochloric acid, forming iodine/triiodide that is further electrochemically reduced at a glassy carbon electrode at +200 mV versus Ag/AgCl electrode is employed. In order to increase sensitivity without using of too high acid concentration, promoting of the reaction by increasing reaction time and temperature can be carried out. This can be done without increase of dispersion of the product zone by stopping the flow while the injected zone is being in a mixing coil which is immersed in a water bath of 55 ± 0.5 °C. In a closed system of FIA, a side reaction of oxygen with iodide is also minimized. Under a set of conditions, linear calibration graphs were in the ranges of 1.2 × 10⁻⁶-6.0 × 10⁻⁵ mol l⁻¹and 6.0 × 10⁻⁵-6.0 × 10⁻⁴ mol l⁻¹. A sample throughput of 25 h⁻¹ was accomplished. Relative standard deviation was 2% (n = 21, 1.2 × 10⁻⁴ mol l⁻¹ chlorate). The proposed sFI-Amp procedure was successfully applied to the determination of chlorate in soil samples from longan plantation area.     

The electron-poor phosphines P{C6H3(CF3)2-3,5}3 and P(C6F5)3 do not mimic phosphites as ligands for hydroformylation. A comparison of the coordination chemistry of P{C6H3(CF3)2-3,5}3 and P(C6F5)3 and the unexpectedly low hydroformylation activity of their rhodium complexes

The fluoroaryl phosphines P{C6H3(CF3)2-3,5}3 (La) and P(C6F5)3 (Lb) form the complexes trans-[MCl2(La)2] and trans-[MCl2(Lb)2](M = Pd or Pt) which have been isolated and fully characterised. 31P NMR studies of competition experiments show that the stability of trans-[PdCl2L2] is in the order L = Lb< La 相似文献   

Apoptolidins B and C: isolation, structure determination, and biological activity

[reaction: see text] Apoptolidin (1) is a promising new therapeutic lead that exhibits remarkable selectivity against cancer cells relative to normal cells. We report the isolation, characterization, solution structure, stability, and biological activity of two new members of this family: apoptolidins B (2) and C (3). These new agents are found to have antiproliferative activity on par with or better than apoptolidin itself in an assay with H292 lung cancer cells.     

A dynamic liquid-liquid interfacial pressure detector for the rapid analysis of surfactants in a flowing organic liquid

Design and development of a dynamic interfacial pressure detector (DIPD) is reported. The DIPD measures the differential pressure as a function of time across the liquid-liquid interface of organic liquid drops (i.e., n-hexane) that repeatedly grow in water at the end of a capillary tip. Using a calibration technique based on the Young-Laplace equation, the differential pressure signal is converted, in real-time, to a relative interfacial pressure. This allows the DIPD to monitor the interfacial tension of surface active species at liquid-liquid interfaces in flow-based analytical techniques, such as flow injection analysis (FIA), sequential injection analysis (SIA) and high performance liquid chromatography (HPLC). The DIPD is similar in principle to the dynamic surface tension detector (DSTD), which monitors the surface tension at the air-liquid interface. In this report, the interfacial pressure at the hexane-water interface was monitored as analytes in the hexane phase diffused to and arranged at the hexane-water interface. The DIPD was combined with FIA to analytically measure the interfacial properties of cholesterol and Brij^®30 at the hexane-water interface. Results show that both cholesterol and Brij^®30 exhibit a dynamic interfacial pressure signal during hexane drop growth. A calibration curve demonstrates that the relative interfacial pressure of cholesterol in hexane increases as the cholesterol concentration increases from 100 to 10,000 μg ml⁻¹. An example of the utility of the DIPD as a selective detector for a chromatographic separation of interface-active species is also presented in the analysis of cholesterol in egg yolk by normal-phase HPLC-DIPD.     

A comparison of the Kjeldahl and Dumas methods for the determination of protein in foods,using data from a proficiency testing scheme

Both the Kjeldahl and the Dumas methods for the determination of protein in foodstuffs are currently in use, but the empirical nitrogen factors used to convert the determined nitrogen content to protein content are based on the Kjeldahl method alone. Non-equivalence between the two methods could therefore result in some laboratories reporting an incorrect protein content. We report here a study using data accumulated over several years in the results of a proficiency testing scheme. On average the Dumas method provided results that were relatively higher by about 1.4% than the Kjeldahl method, but the difference between the methods depended on the type of foodstuff. The methodology of looking for bias between analytical methods is critically discussed.     

Synthetic anisomycin analogues activating the JNK/SAPK1 and p38/SAPK2 pathways

The synthesis of C(4)H and C(4)Me analogues of the JNK/p38 pathway activator anisomycin, based upon an aldol or Claisen construction of the C(3)-C(4) bond, has been demonstrated. The relative activation of the JNK/SAPK1 and p38/SAPK2 pathways in RAW macrophages by these analogues, and their synthetic precursors, has been assessed using immunoblot assays against phosphorylated c-Jun and MAPKAP-K2. These studies demonstrate that some of the synthetic C(4) analogues are also potent activators of these stress kinase pathways.