Products of two 1ϕ1 series and implications

An expansion formula into bivariate formal power series is established that implies, as consequences, three remarkable identities of partial theta functions due to Warnaar (2003), Schilling–Warnaar (2002) and Andrews–Warnaar (2007).     

On-line Time Differential Perturbed Angular Correlation with Light Probe Nucleus 19F

An on-line time differential perturbed angular correlation technique has been developed with the light probe nucleus ¹⁹F. The first on-line TDPAC measurement was carried out to determine the field gradient in Cd and quadrupole moment of ¹⁹F (0.197 MeV: I ^π = 5/2⁺, T_1/2 = 89 ns). This revised version was published online in September 2006 with corrections to the Cover Date.     

四苯基卟吩激发—重态衰变的“外部重原子效应”的研究

考查了在有芳烃卤代物RX(如氯苯、溴苯和碘苯)存在时,四苯基卟吩TPP的荧光衰变现象。基于荧光衰变动力学分析,发现:在RX和TPP之间生成复合物是引起重原子效应的一个基本步骤。荧光衰变的动力学参数则进一步表明:可观察的外部重原子效应主要是由于发生分子间电荷转移相互作用而引起的。     

Si–Si optical phonon behavior in localized Si clusters of Si<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript> alloy nanocrystals

Raman spectra acquired from Si _x Ge_1−x -nanocrystal-embedded SiO₂ films show dependence of the Si–Si optical phonon frequency on Si content. The frequency upshifts, and peak intensity increases as the silicon concentration increases. For a given Si content, the frequency remains unchanged with annealing temperature. Spectral analysis and density functional theory calculation reveal that the optical Si–Si phonon is related to the formation of localized Si clusters surrounded by Si/Ge atomic layers in the Si _x Ge_1−x nanocrystals and the intensity enhancement arises from the larger cluster size. The synergetic effect of surface tensile stress and phonon confinement determines the Si–Si optical phonon behavior.     

再生资源基热塑性橡实淀粉/聚己内酯复合材料的制备及红外光谱分析

以橡实淀粉为主要原料,采用熔融挤出法制备了热塑性橡实淀粉(TPAS)和热塑性橡实淀粉(TPAS)/聚己内酯(PCL)二元复合材料.通过对样品FTIR和XRD的分析,研究了乙二醇、丙三醇、乙醇胺、二乙醇胺、三乙醇胺五种不同增塑剂对样品的分子结构的影响,亦研究了不同增塑体系对复合材料分子结构和力学性能的影响.结果表明:五种...     

Retrospectively gated cardiac cine imaging with temporal and spatial acceleration

Parallel imaging methods are routinely used to accelerate the image acquisition process in cardiac cine imaging. The addition of a temporal acceleration method, whereby k-space is sampled differently for different time frames, has been shown in prior work to improve image quality as compared to parallel imaging by itself. However, such temporal acceleration strategies prove difficult to combine with retrospectively gated cine imaging. The only currently published method to feature such combination, by Hansen et al. [Magn Reson Med 55 (2006) 85-91] tends to be associated with prohibitively long reconstruction times. The goal of the present work was to develop a retrospectively gated cardiac cine method that features both parallel imaging and temporal acceleration, capable of achieving significant acceleration factors on commonly available hardware and associated with reconstruction times short enough for practical use in a clinical context.Seven cardiac patients and a healthy volunteer were recruited and imaged, with acceleration factors of 3.5 or 4.5, using an eight-channel product cardiac array on a 1.5-T system. The prescribed FOV value proved slightly too small in three patients, and one of the patients had a bigemini condition. Despite these additional challenges, good-quality results were obtained for all slices and all patients, with a reconstruction time of 0.98±0.07 s per frame, or about 20 s for a 20-frame slice, using a single processor on a single PC. As compared to using parallel imaging by itself, the addition of a temporal acceleration strategy provided much resistance to artifacts.     

Radiation-induced changes in electrical conductivity and structure of BaPbO3 after γ-irradiation

Several barium plumbate (BaPbO₃) solid samples, made from PbO and BaCO₃ powder by chemistry liquid-phase coprecipitation, were investigated before and after γ-irradiation. The solid samples were irradiated by a ⁶⁰Co γ-irradiation source whose dose rate is about 0.7?kGy per hour. The irradiation times were 0, 72, 144, 216, 288 and 360?h. Then, the four-probe method, X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were used to indicate the changes in electrical conductivity and microstructure of BaPbO₃ after γ-irradiation. The XRD results indicated that the content of PbO was reduced as the irradiation dose was increased and eventually vanished from the surface of samples. However, there was no new obvious substance phase found from the XRD atlas. It seems that the PbO transformed into nearly amorphous Pb₅O₈. The conjecture could be proved by the results of annealing experiment and SEM. The XPS results seem to show that the microstructure of BaPbO₃ was slightly changed.