On the Bergman representative coordinates

We study the set where the so-called Bergman representative coordinates (or Bergman functions) form an immersion. We provide an estimate of the size of a maximal geodesic ball with respect to the Bergman metric, contained in this set. By concrete examples we show that these estimates are the best possible.Comment: 20 page

From the Complete Yang Model to Snyder's Model, de Sitter Special Relativity and Their Duality

By means of Dirac procedure, we re-examine Yang's quantized space-time model, its relation to Snyder's model, the de Sitter special relativity and their UV-IR duality. Starting from a dimensionless dS_5-space in a 5+1-d Mink-space a complete Yang model at both classical and quantum level can be presented and there really exist Snyder's model, the dS special relativity and the duality.Comment: 7 papge

Ultrasonic-assisted extraction and evaluation of biological activities of flavonoids from Flemingia philippinensis Merr et Rolfe

Purpose: To develop a simple and rapid method for extracting total flavonoids from the roots of Flemingia philippinensis and to investigate the antioxidant and anti-tumor activities of the extracts of the materials from various locations in China.Methods: The total flavonoids in F. philippinensis were obtained by ultrasonic-assisted conventional solvent extraction method, and the extraction conditions were optimized by single factor and orthogonal test. 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and anti-tumor activities, using 3-(4,5- dimethylthiazol-2-yl)- 2,5-diphenyltetrazolium bromide (MTT) assay, of the extract were evaluated. The contents of flemiphilippinin A, auriculasin, 5,7,3',4'-tetrahydroxy-6,8 –diprenylisoflavone and dorsmanins I were also determined.Results: Optimal extraction conditions were as follows: extraction time, 40 min; methanol concentration, 85 %; and solvent to solid ratio, 40 mL/g; and number of extraction, once. Total flavonoid content varied greatly (3.7 - 14.35 %) among the 19 samples collected from different origins in China. Flemiphilippin A, 5,7,3',4'- tetrahydroxy-6,8 -diprenylisoflavone, auriculasin and dorsmanins I showed varying DPPH radical scavenging activities with effective half maximal concentration (EC50) of 18.36, 23.59, 57.25 and 63.54 μg/mL, respectively.  Flemiphilippinin A (5 μg/mL) also exhibited some level of antitumor activity against human hepatocellular carcinoma cell (BEL-7402), human lung epithelial (A-549) and human ileocecal adenocarcinoma cell (HCT-8) with inhibition of 91.13 ± 1.6, 91.22 ± 3.23, and 79.77 ± 3.57 %, respectively.Conclusion: Total flavonoids can be extracted efficiently from F.  philippinensis by ultrasonic-assisted extraction method. Flemiphilippinin A has a potential for use in medicine as an antioxidant and antitumor drug

Magnetic Reconnection resulting from Flux Emergence: Implications for Jet Formation in the lower solar atmosphere?

We aim at investigating the formation of jet-like features in the lower solar atmosphere, e.g. chromosphere and transition region, as a result of magnetic reconnection. Magnetic reconnection as occurring at chromospheric and transition regions densities and triggered by magnetic flux emergence is studied using a 2.5D MHD code. The initial atmosphere is static and isothermal, with a temperature of 20,000 K. The initial magnetic field is uniform and vertical. Two physical environments with different magnetic field strength (25 G and 50 G) are presented. In each case, two sub-cases are discussed, where the environments have different initial mass density. In the case where we have a weaker magnetic field (25 G) and higher plasma density ($N_e=2\times 10^{11}$ cm$^{-3}$), valid for the typical quiet Sun chromosphere, a plasma jet would be observed with a temperature of 2--3 $\times 10^4$ K and a velocity as high as 40 km/s. The opposite case of a medium with a lower electron density ($N_e=2\times 10^{10}$ cm$^{-3}$), i.e. more typical for the transition region, and a stronger magnetic field of 50 G, up-flows with line-of-sight velocities as high as 90 km/s and temperatures of 6 $\times$ 10$^5$ K, i.e. upper transition region -- low coronal temperatures, are produced. Only in the latter case, the low corona Fe IX 171 \AA\ shows a response in the jet which is comparable to the O V increase. The results show that magnetic reconnection can be an efficient mechanism to drive plasma outflows in the chromosphere and transition region. The model can reproduce characteristics, such as temperature and velocity for a range of jet features like a fibril, a spicule, an hot X-ray jet or a transition region jet by changing either the magnetic field strength or the electron density, i.e. where in the atmosphere the reconnection occurs.Comment: 11 pages, 13 figures, 2 table

An extensible product structure model for product lifecycle management in the make-to-order environment

This paper presents a product structure model with a semantic representation technique that make the product structure extensible for developing product lifecycle management (PLM) systems that is flexible for make-to-order environment. In the make-to-order business context, each product could have a number of variants with slightly different constitutions to fulfill different customer requirements. All the variants of a family have common characteristics and each variant has its specific features. A master-variant pattern is proposed for building the product structure model to explicitly represent common characteristics and specific features of individual variants. The model is capable of enforcing the consistency of a family structure and its variant structure, supporting multiple product views, and facilitating the business processes. A semantic representation technique is developed that enables entity attributes to be defined and entities to be categorized in a neutral and semantic format. As a result, entity attributes and entity categorization can be redefined easily with its configurable capability for different requirements of the PLM systems. An XML-based language is developed for semantically representing entities and entity categories. A prototype as a proof-of-concept system is presented to illustrate the capability of the proposed extensible product structure model