Local Hopf bifurcation and global existence of periodic solutions in TCP system

This paper investigates the dynamics of a TCP system described by a first- order nonlinear delay differential equation. By analyzing the associated characteristic transcendental equation, it is shown that a Hopf bifurcation sequence occurs at the pos- itive equilibrium as the delay passes through a sequence of critical values. The explicit algorithms for determining the Hopf bifurcation direction and the stability of the bifur- cating periodic solutions are derived with the normal form theory and the center manifold theory. The global existence of periodic solutions is also established with the method of Wu （Wu, J. H. Symmetric functional differential equations and neural networks with memory. Transactions of the American Mathematical Society 350（12）, 4799-4838 （1998））.     

荧光光度法测定蔬果类罐头食品中的微量铅

以3mol/L HCl为介质,利用荧光光度计检测PbCl2-4的荧光强度,建立了测定蔬果类罐头食品中微量铅的新方法,该方法的检出限为8.8μg/mL,回收率为;97.0%.     

Metal-Carboxyl Helical Chain Secondary Units Supported Ion-Exchangeable Anionic Uranyl–Organic Framework

As a less explored avenue, actinide-based metal-organic frameworks (MOFs) are worth studying for the particularity of actinide nodes in coordination behaviour and assembly modes. In this work, an azobenzenetetracarboxylate-based anionic MOF supported by uranyl–carboxyl helical chain units was synthesized, incorporating linear uranyl as the metal centre. This kind of helical chain-type building unit is reported for the first time in uranyl-based MOFs. Structural analysis reveals that the formation of helical chain secondary units can be attributed to restricted equatorial coordination of rigid flat azobenzene ligand to uranyl centres. Meanwhile, this newly-synthesized anionic material has been used to remove Eu³⁺ ions, as a non-radioactive surrogate of Am³⁺ ion, through an ion-exchange process with [(CH₃)₂NH₂]⁺ ions in its open channels, as evidenced by a combination of ¹H NMR spectroscopy, EDS and PXRD.     

Microwave-assisted 6π-electrocyclization in water

The recent development of microwave-assisted aqueous synthesis of polyheterocyclic-fused quinoline-2-thiones through 6π-electrocyclization was highlighted.     

The reduction effect and mechanism of Deinococcus radiodurans transformed dsrA gene to uranyl ions

Journal of Radioanalytical and Nuclear Chemistry - Deinococcus radiodurans (DR) is highly resistant to ionizing radiation. This study aims to convert dsrA gene into DR to construct...     

Experimental study of dependence on humidity and flow rate for a modified flowthrough radon source

Journal of Radioanalytical and Nuclear Chemistry - Flow-through radon sources were widely utilized in the calibration of radon equipment and radon studies. In this paper a broken 266Ra source which...     

Optimization of the thoron progeny compensation system of a thoron calibration chamber

Journal of Radioanalytical and Nuclear Chemistry - The long-term stability and homogeneity of thoron progeny are key to the performance of a thoron calibration chamber, which is vital to quality...