振荡奇异积分的L~p有界性

文中讨论了振荡奇异积分:其中对满足一定凸性条件的P以及Ω∈L~q(S~(n-1))(q>1),证明了T在L~P(R~n)上有界,p>1.     

Mössbauer study of magnetic ordering and superconductivity in YBa2(Cu1−xFex)3O7

We have made superconducting samples of the Y?Ba?Cu?O system with Fe substituted for the Cu. The percentage of Fe substituted varied from 2 to 100. The samples have been verified by x-ray diffraction to be single-phase 1–2–3 compounds. The 6% Fe substitution reduces T_c from 94 K to 80 K. The room temperature Mössbauer spectrum shows two pairs of doublets, indicating there are two distinct Cu sites in the sample. The most surprising result is that magnetic ordering of the Fe coexists with superconductivity of the material at 4.2 K.     

杂多阴离子的NMR和ESR研究——P-V-W Keggin阴离子的31P、51V、17O-NMR谱

本文合成了六种含有P-V-W和V-V-W Keggin结构的杂多阴离子,并研究了它们的³¹P、⁵¹V、¹⁷O-NMR谱,对于PV_xW_12-xO₄₀^(x+3)-(x=1~4)阴离子,当x=1时,³¹P和⁵¹V-NMR谱只有一条线,并且此线化学位移和pH无关。当x ≥ 2时,谱线数目随着x迅速增加,其原因是几何异构体的数目和类型迅速增加。它们的化学位移δ_p,和δ_v。依赖于溶液的酸性和x,即δ_p,随pH值和x增加而减少,而δ_v,却随pH和x的增加而增加。最后简短讨论了桥氧上质子化的影响。     

The classification for dynamics of an STD model

In this paper, a 3(n+1) dimensional sexually transmitted disease model is studied. The model involves two competing strains 1 and 2, where females are divided into n different groups based on their susceptibility to two distinct pathogenic strains. The first and second reproduction numbers , which have their biological meaning, are defined for strain , respectively. With the non-degeneracy assumption (H), a complete classification for dynamics of this model in terms of is presented, which is based on the theory of type-K monotone dynamical systems.     

Existence and asymptotic behavior of positive solutions for a variable exponent elliptic system without variational structure

We mainly consider the existence and asymptotic behavior of positive solutions of the following system

     

沿齐次曲线的强奇异积分算子在调幅空间上的有界性

设Γ_θ(t)为R~n(n≥2)中的齐次曲线,定义沿齐次曲线的强奇异积分算子T_(n,α,β)f(x)=p.v.∫_(-1)~1f(x-Γ_θ(t))(e~((-2πi|t|)~(-β))/(t|t|~α))dt,α,β>0.本文讨论了上述奇异积分算子在广义调幅空间上的有界性.     

Preparation and application of solid-phase microextraction fiber based on molecularly imprinted polymer for determination of anabolic steroids in complicated samples

A relatively selective, chemically and physically robust SPME fiber was developed in a simple way with testosterone-imprinted polymer, and then directly coupled with gas chromatography-mass spectrometry (GC-MS) for selective extraction and analysis of anabolic steroids. The factors influencing polymerization (i.e., cross-linker, polymerization solvent, polymerization time) were optimized in detail and the polymer was characterized by scanning electron microscope, infrared spectrometer and thermogravimetric analyzer. Furthermore, the extraction performance of the MIP-coated SPME fibers such as extraction ability and selectivity was evaluated. Moreover, the interaction mode between target analytes and fiber coating was deducted. Finally, the method for extraction and determination of androsterone, stanolone, androstenedione and methyltestosterone by the homemade MIP-coated SPME fibers with GC-MS was obtained. It was applied to the simultaneous analysis of four anabolic steroids in the spiked human urine with the satisfactory recoveries.