Permanence,extinction and periodic solutions in a mathematical model of cell populations affected by periodic radiation

A periodic mathematical model of cell populations affected by periodic radiation is presented and studied in this paper. We obtain some sufficient conditions on the permanence and extinction of the system. Furthermore, criteria on the existence and global asymptotic stability of unique positive periodic solutions are established. Some numerical examples are shown to verify our results. A discussion is presented for further study.     

An alternative class of irreducible polynomials for optimal extension fields

Optimal extension fields (OEF) are a class of finite fields used to achieve efficient field arithmetic, especially required by elliptic curve cryptosystems (ECC). In software environment, OEFs are preferable to other methods in performance and memory requirement. However, the irreducible binomials required by OEFs are quite rare. Sometimes irreducible trinomials are alternative choices when irreducible binomials do not exist. Unfortunately, trinomials require more operations for field multiplication and thereby affect the efficiency of OEF. To solve this problem, we propose a new type of irreducible polynomials that are more abundant and still efficient for field multiplication. The proposed polynomial takes the advantage of polynomial residue arithmetic to achieve high performance for field multiplication which costs O(m ^3/2) operations in \mathbbF_p{\mathbb{F}_p} . Extensive simulation results demonstrate that the proposed polynomials roughly outperform irreducible binomials by 20% in some finite fields of medium prime characteristic. So this work presents an interesting alternative for OEFs.     

模糊蚁群算法及其在TSP中的应用

在传统蚁群算法的基础上加入了使用模糊规则表更新信息素的策略,提出了一种新的算法——模糊蚁群算法.算法结合了模糊控制中输入输出的模糊化处理和蚁群寻优的特点,为实际问题提供了新的解决手段.文中将模糊蚁群算法应用于TSP问题,通过对中国31个省会城市等实例数据进行的测试,验证表明了新算法具有良好的有效性和鲁棒性.     

Controlled formation of mass-selected Cu-Au core-shell cluster beams

Synthesis of bimetallic clusters is a topic of accelerated interest; their physical and chemical properties are greatly dependent on their composition, size, and structure. The cluster beam technique is widely used for preparation of clusters. However, creating bimetallic clusters with well-controlled composition, size, and structure, especially for larger clusters (>100 atoms), is still a big challenge. Here we demonstrate that not only size and composition but also the structure of bimetallic clusters can be controlled by tuning aggregation parameters.     

Direct analysis of oligosaccharides and alpha hydroxy acids in fruits using electrosonic spray ionization mass spectrometry

Electrosonic spray ionization (ESSI) is a derivative technique of electrospray ionization (ESI) for mass spectrometry (MS) in which droplets are charged in the course of sonic spray. In this study, we applied ESSI MS to direct analysis of oligosaccharides and alpha hydroxy acids (AHAs) in fruits. The components were extracted from fruit fleshes by a feasible method prior to ESSI MS analysis, but the fruit juices were analyzed without further pretreatment. The results demonstrate that mainly alkali metal adducts of oligosaccharides are favorably produced in positive ion mode, while deprotonated AHAs and oligosaccharides are produced in negative ion mode. Compared with mass spectra obtained using electrospray droplet impact/secondary ion mass spectrometry (EDI/SIMS), mass spectra using ESSI make the identification of oligosaccharides more straightforward in positive ion mode than in negative ion mode.     

Biotransformation of a taxadiene by ginkgo cell cultures and the tumor multi-drug resistant reversal activities of the metabolites

The biotransformation of 2α,5α,10β-triacetoxy-14-oxo-taxa-4(20),11-diene (1) by cultured Gingko cells afforded four products. Their structures were identified on the basis of analyses of the chemical and spectroscopic (IR, MS, 1H- and 13C-NMR) data. Among them, 2, 3 and 5 were three new compounds, and 4 displayed potent multi-drug resistant (MDR) reversal activities to MX-1/T tumor MDR cells.     

ent‐Kaurane Diterpenes and Further Constituents from Wedelia trilobata

Two new ent‐kaurane diterpenes, wedelidins A ( 8 ) and B ( 9 ), together with eighteen other constituents, including the sesquiterpenoids 1 and 2 , ent‐kaurane diterpenes 3 – 7 , triterpenoids 10 and 11 , steroids 12 – 14 , and flavonoids 15 – 17 as well as benzene derivatives 18 – 20 , were isolated from the aerial parts of Wedelia trilobata. The structures of wedelidins A ( 8 ) and B ( 9 ) were elucidated by extensive spectroscopic analyses (including UV, IR, NMR, and MS). Furthermore, the structures of compounds 2 and 3 were confirmed by X‐ray single‐crystal diffraction analyses.     

Photocatalytic reduction of CO2 in methanol to methyl formate over CuO-TiO2 composite catalysts

Photocatalytic reduction of CO(2) on CuO-TiO(2) composite catalysts in the presence of methanol to prepare methyl formate had been investigated. Methanol was used as sacrificial reagent to react with the photo-generated holes in the valence band, and CO(2) was reduced by the electrons in the conduction band. CuO-TiO(2) was optimized for CuO loading, preparation method and calcination temperature. The catalyst of 1.0CuO-TiO(2), calcined at 450°C and CTAB as a dispersant showed the highest overall activity. The heterojunction between CuO and TiO(2) demonstrated with HRTEM played an important role in enhancing the photocatalytic activity.     

Density functional study of AgnPd and AgnPdH clusters

Small Ag_nPd (n = 5) clusters and their hydrides Ag_nPdH (n = 5) have been studied by density functional theory calculations. For bare clusters, the structures in which the Pd atom has a maximum number of neighboring Ag atoms tend to be energetically favorable. Hydrogen prefers binding to Ag? Pd bridge site of Ag_nPd clusters except for Ag₅Pd. The binding energy has a strong odd–even oscillation. The electron transfers are from Ag atoms to Pd in bare clusters and are from metal clusters to H in cluster hydrides. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Three-step calcination synthesis of high-purity Li8ZrO6 with CO2 absorption properties

Li(8)ZrO(6) contains a high lithium content and may bear a great ability of CO(2) absorption, yet the reports about the properties of CO(2) absorption on Li(8)ZrO(6) are few to date for its difficulty in production. In this paper, high-purity Li(8)ZrO(6) is synthesized via a three-step calcination method combined with an effective lithium source and a suitable initial Li/Zr molar ratio. The produced Li(8)ZrO(6) possesses a great CO(2) absorption capacity of about 53.98 wt % at 998 K, which could be well-maintained in a wide range of CO(2) partial pressures of 0.1-1.0 bar although it decreased gradually during the multicycle process of CO(2) absorption-desorption in a 10% CO(2) feed stream because of the high working temperature. These properties imply that Li(8)ZrO(6) may be a new option for high-temperature CO(2) capture applied in industrial processes such as a steam methane reformer.