An advanced fully 3D OSEM reconstruction for positron emission tomography

A fully 3D OSEM reconstruction method for positron emission tomography (PET) based on sym-metries and sparse matrix technique is described. Great savings in both storage space and computation time were achieved by exploiting the symmetries of scanner and sparseness of the system matrix. More reduction of storage requirement was obtained by introducing the approximation of system matrix. Iteration-filter was per-formed to restrict image noise in reconstruction. Performances of simulation data and phantom data got from Micro-PET (Type: Epuls-166) demonstrated that similar image quality was achieved using the approximation of the system matrix.     

Coupling Parameter in the Single-j Shell Model

We propose a modified formula which is used to determine the coupling parameter C in the Hamiltonian of the single-j shell. In comparison with the previously known formula, the new formula improves the agreement between the intruder single-j levels and the Nilsson ones. For studies of chiral bands within the particle rotor model, the new coupling parameter will considerably influence the energy splitting between the doublet bands.     

The β Decay of 21N

The β-delayed neutron and γ energy spectra taken from the decay of neutron-rich nucleus ²¹N were measured by using the β-γ and β-n coincidence detection method. Thirteen new neutron groups ranging from 0.28MeV to 4.98MeV and with a total branching ratio of 88.7±4.2% were observed andpresented. One γ transition with an energy of 1222keV emitted from the excited state of ²¹O, and four γ transitions with energies of 1674, 2397, 2780, and 3175keV emitted from the excited states of ²⁰O were identified in the β decay chain of ²¹N. The β decay half-life for ²¹N is determined to be 82.9±1.9ms. The uncertainty of half-life is much smaller than the previous result.     

原子级结构精确Cu13团簇的光致发光和电化学传感研究

铜基纳米材料在发光和(生物)化学传感领域展现出广阔的应用前景. 铜纳米团簇作为一种新型的纳米材料, 由于其具有原子级精确的结构而引起了研究人员的广泛关注, 但是合成稳定并且具有优异性能的铜簇仍然具有挑战性. 本工作通过引入还原剂(NaBH₄)成功地制备出一种新型的巯基咪唑配体保护的一价铜纳米团簇[Cu₁₃(SR)₁₂]NO₃ (Cu₁₃ NC, 其中RSH=2-巯基苯并咪唑), 并通过单晶X射线衍射分析和电喷雾电离质谱(ESI-MS)对其结构和组成进行了表征. Cu₁₃ NC的金属骨架可以看成是三个三角双锥共享一个或两个顶点构成, 并通过简单的桥联模式被12个巯基配体保护. 固态Cu₁₃ NC具有良好的稳定性及亮红色的发光(λ_em=627 nm). 同时, 结构的两端有两个裸露的铜原子, 这使其在电化学检测H₂O₂的实验中表现出良好的电化学活性. 本工作为更好地研究纳米铜簇的结构和其光、电性能之间的联系提供了机会.     

Linker Flexibility-Dependent Cluster Transformations and Cluster-Controlled Luminescence in Isostructural Silver Cluster-Assembled Materials (SCAMs)

Silver chalcogenolate clusters (SCCs) and silver cluster-assembled materials (SCAMs) are an important category of novel luminescent materials, the emission of which can be modulated by variation of the cluster nodes and linker species. Here, the successfully synthesis of two isostructural 2D SCAMs is reported: Ag₁₂bpa and Ag₁₂bpe are formed by using two linkers with different conformational freedom (bpa=1,2-bis(4-pyridyl)ethane, bpe=1,2-bis(4-pyridyl)ethylene), with dodenuclear silver chalcogenolate clusters as secondary building units (SBUs). Interestingly, nonluminescent Ag₁₂bpa at room temperature could quickly transform into 1D Ag₁₀bpa , with concomitant dissociation of two silver atoms and the remaining ten silver atoms rearranging in the cluster, thus exhibiting an intense yellow phosphorescence after being triggered by acetonitrile (CH₃CN). Similarly, stimulating Ag₁₂bpe with CH₃CN, by contrast, gave another 2D structure Ag₁₂bpe-1b with the distorted SBUs and different topology structure, and both of them are merely red-emissive at low temperature. To note, after exchanging ligands, room-temperature nonluminescent 2D Ag₁₂bpe-1b can be transformed into intensely luminescent 1D Ag₁₀bpa . This linker-flexibility-dependent structural transformation and cluster-based SBU controlled luminescence remains scarce. Our work provides new insights into structure–luminescence relationship in clustered metal–organic frameworks and intelligent stimulus-responsive luminescent materials.     

Benzenepolycarboxylate-templated assembly of silver coordination polymers exhibiting argentophilic honeycomb layer and tubular motifs

Organic anion template-controlled reactions of benzenepolycarboxylic acids with silver(I) salts resulted in two coordination polymers with distinct structural features based on the argentophilic interaction, one exhibiting a honeycomb layer formed by the fusion of macrocyclic Ag(16) rings and the other furnishing the first example of a Ag(∞) tubular motif.     

Respiratory motion correction with an improved demons algorithm for PET images

Respiratory motion is a major factor that affects the quality of PET images of the thoracic area. The diaphragm moves about 15-20 mm due to respiratory motion, which substantially degrades the effective spatial resolution of PET. In this paper, a gated acquisition method is used to correct the motion effects. In this method, an improved demons algorithm is proposed to align the gated images. The experimental results show that the quality of PET images is significantly improved when using our improved method and the proposed method has a faster convergence rate than the original demons algorithm.     

以一维谐振子势阱中的单粒子为工质的量子热机性能分析

建立了以一维谐振子势阱中的单粒子为工质的量子热机模型.当势阱壁宽度和粒子的量子态缓慢改变时, 该热机类似于经典卡诺热机对外做功.假设势阱壁移动速度非常缓慢并且考虑热漏, 推导出量子热机循环的输出功率和效率等重要性能参数的一般表达式.通过优化分析, 获得了热机循环中各主要性能参数的最佳优化值和优化区间.     

High-Spin Level Scheme of Odd-odd 142Pm

The level structure of doubly odd nucleus ¹⁴²Pm has been studied via the ¹²⁸Te(¹⁹F,5nγ)¹⁴²Pm reaction in the energy region from 75 to 95MeV. In-beam γ rays were measureed including the excited function, γ-ray singles and γ-γ coincidences in experiment. The level scheme of ¹⁴²Pm has been extended up to excitation energy of 7030.0keV including 25 new γ rays and 13 new levels. Based on the measured γ-ray anisotropies, the level spins in ¹⁴²Pm have been suggested.     

核磁共振氢谱内标法测定茚地普隆的含量

建立了测定无对照品的新型非苯二氮唑类镇静催眠药茚地普隆含量的快速、专属、简单的核磁共振氢谱内标法。用Varian Mercury Plus400MHz核磁共振谱仪,在25℃、以氘代氯仿为溶剂、3,4-二硝基甲苯为内标、观察频率400.121MHz、谱宽6410Hz、90°脉冲宽度6.45μs、采集时间4s和延迟时间15s的条件下采集试样的氢谱。以化学位移分别在δ8.72和δ8.72处的茚地普隆和3,4-二硝基甲苯的单峰作为定量峰,其峰面积比(As/Ar,y)与其质量比(ms/mr,x)的线性回归方程为y=6.1458x 0.0055,相关系数为r=0.99996,含量测定重复性实验的RSD为0.29%(n=6)。分析结果表明,在没有对照品的情况下,核磁共振氢谱内标法,可用于茚地普隆的含量测定和质量控制。