Studies on the Neodymium-induced Pinacol Coupling of Aromatic Aldehydes and Ketones in Aqueous Media

1,2-Diols are very useful synthons for a variety of organic synthesis1, which have been used as intermediates for the construction of the skeletons of the biologically important natural products2. Within the last several years, various metals, such as Mg3…     

Mikheyev–Smirnov–Wolfenstein Effect¶for Linear Electron Density

When the electron density is a linear function of distance, it is known that the MSW equations for two neutrino species can be solved in terms of known functions. It is shown here that more generally, for any number of neutrino species, these MSW equations can be solved exactly in terms of single integrals. While these integrals cannot be expressed in terms of known functions, some of their simple properties are obtained. Application to the solar neutrino problem is briefly discussed. Received: 3 April 2000 / Accepted: 10 April 2000     

NEW FREQUENCY STEP-TUNABLE ECRH SYSTEM FOR ASDEX UPGRADE

A new broadband ECRH (Electron Cyclotron Resonance Heating) system is currently under construction at the ASDEX Upgrade tokamak. This system will employ multi-frequency gyrotrons step-tunable in the range 105–140 GHz. In its final stage the system will consist of 4 gyrotrons with a total power of 4 MW and a pulse length of 10 s. It employs a fast steerable launcher for feedback controlled deposition that allows for poloidal steering of 10° within 100 ms. Transmission line elements, such as corrugated waveguides, polarizer mirrors and vacuum windows, are designed to cope for this frequency band.     

Total Synthesis of (±)-Iridolactone

A total synthesis of (±)-iridolactone ( 1 ) from bicyclo[2.2.1]ketone 6 is described. Trisubstituted cyclopentenoid aldehyde 7 is a key intermediate.     

On transverse momentum event–by–event fluctuations in string hadronic models

Transverse momentum event–by–event fluctuations are studied within the string–hadronic model of high energy nuclear collisions, LUCIAE. Data on non–statistical fluctuations in p+p interactions are reproduced. Fluctuations of similar magnitude are predicted for nucleus–nucleus collisions, in contradiction to the preliminary NA49 results. The introduction of a string clustering mechanism (Firecracker Model) leads to a further, significant increase of fluctuations for nucleus–nucleus collisions. Secondary hadronic interactions, as implemented in LUCIAE, cause only a small reduction of fluctuations. Received: 23 October 1998 / Published online: 11 March 1999     

Structural and magnetic properties of Mg(In2−xMnx)O4 system

We synthesized the Mn-doped Mg(In_2−xMn_x)O₄ oxides with 0.03?x?0.55 using a solid-state reaction method. The X-ray diffraction patterns of the samples were in a good agreement with that of a distorted orthorhombic spinel phase. Their lattice parameters and unit-cell volumes decrease with x due to the substitution of the smaller Mn³⁺ ions to the larger In³⁺ ions. The undoped MgIn₂O₄ oxide presents diamagnetic signals for 5 K?T?300 K. The M(H) at T=300 K reveals a fairly negative-sloped linear relationship. Neither magnetic hysteresis nor saturation behavior was observed in this parent sample. For the Mn-doped samples, however, positive magnetization were observed between 5 and 300 K even if the x value is as low as 0.03. The mass susceptibility enhances with Mn content and it reaches the highest value of 1.4×10⁻³ emu/g Oe (at T=300 K) at x=0.45. Furthermore, the Mn-doped oxides with x=0.06 and 0.2, respectively, exhibit nonlinear magnetization curves and small hysteretic loops in low magnetic fields. Susceptibilities of the Mn-doped samples are much higher than those of MnO₂, Mn₂O₃ oxides, and Mn metals. These results show that the oxides have potential to be magnetic semiconductors.     

对称群的分歧数据系统分类

含特征标的分歧数据系统能被用来分类PM箭图Hopf代数.本文给出了对称群Sn(n≠6)上含特征标的分歧数据系统的同构类个数的计算公式.     

烧成工艺对低压用BaTiO3基PTCR陶瓷性能的影响

采用固相反应法制备低压用BaTiO3基PTCR陶瓷。采用XRD、SEM分析陶瓷的相组成及表面形貌。研究了烧成工艺对陶瓷性能的影响。当烧成温度为1280℃,降温时低温保温温度为1045℃时,制备出低阻高耐压BaTiO3基PTCR陶瓷,其室温电阻率ρRT为36Ω·cm,温度系数α为13.8%/℃,耐电压强度E为100 V/mm。