On toughness and (g, f)-factors in bipartite graphs

Let G be a bipartite graph andg and f be two positive integer-valued functions defined on vertex setV(G) ofG such thatg(x) ≤ f(x) for anyx ? V(G). In this paper, a new isolated toughness ofG is defined and some sufficient conditions related to the new toughness forG to have (g,f )-factors are obtained. Furthermore, these results are proved to be sharp in some sense.     

Luminosity function of optically-selected type II QSOs

For a sample of 411 type II QSOs with redshifts less then 0.3, we use the Balmer decrements to do the reddening correction of the [O III] luminosities and then derive the intrinsic [O III] luminosity function. We find that the host reddening correction of the [O III] 5007 luminosity for type II QSOs cannot be neglected. The median Balmer decrement of Hα/Hβ=4.0 corresponds to an extinction of 0.94 mag for the [O III] 5007 line, which is consistent with the result derived from the median Hβ/Hγ. Comparing the intrinsic luminosity function of type II QSOs with that of type I QSOs, we find that the upper limit of the type II QSO’s fraction in the total QSOs is 80% for type II QSOs with z < 0.3 and 8.6⩽log (L _{[O III]}/L _⊙)⩽9.4.

     

MgB_2超导体参量的拟和简化计算

关联长度ξ、临界Cooper对速度、London穿透深度λ以及临界电流密度jc与温度T的变化关系一直是二硼化镁超导体倍受关注的焦点。文中在各向同性的GL理论的框架内对以上参量随温度的变化关系通过计算机进行拟和,得出了数学形式相对简单、物理内涵又比较清晰的数学表达式,达到了对MgB2超导体参量拟和简化计算的目的。     

Fabrication and characterization of ZnO particles with different morphologies for photocatalytic degradation of pentachlorophenol

In this work, ZnO particles with different morphologies were successfully prepared by a simple solution route at low temperature. The products were characterized by SEM, EDS, XRD, TEM, HRTEM, SAED, TG–DTA and UV–Vis DRS. To further understand the formation processes of these ZnO particles, XRD analyses of the intermediates and concentration measurements of Zn(II) remaining in the reaction solution were made at regular intervals throughout the reactions. A possible formation mechanism is discussed. Photocatalytic activity of the as-prepared ZnO powders, evaluated by degradation of pentachlorophenol under UV irradiation, is found to be closely related to the particle morphology.     

A novel thermotropic liquid crystalline copolyester containing phosphorus and aromatic ether moity toward high flame retardancy and low mesophase temperature

A series of thermotropic liquid crystalline polyesters containing phosphorus and aromatic ether groups (TLCP‐AEs) were synthesized from p‐acetoxybenzoic acid (p‐ABA), terephthalic acid (TPA), 4,4′‐oxybis(benzoic acid) (OBBA), and acetylated 2‐(6‐oxid‐6H‐dibenz(c,e) (1,2) oxaphosphorin 6‐yl) 1,4‐benzenediol (DOPO‐AHQ). The chemical structure and the properties of TLCP‐AEs were characterized by Fourier‐transform spectroscopy (FTIR), proton nuclear magnetic resonance spectroscopy (¹H NMR), differential scanning calorimetry (DSC), X‐ray diffraction (XRD), thermogravimetry analysis (TGA), scanning electronic microscopy (SEM), polarizing optical microscopy (POM), limiting oxygen index, and UL‐94 tests, respectively. The results showed that TLCP‐AEs had low and broad mesophase temperatures (230–400 °C). TLCP‐AEs also showed excellent thermal stability; their 5%‐weight‐loss temperatures were above 440 °C and the char yields at 700 °C were higher than 45 wt %. All TLCP‐AE polyesters exhibited high flame retardancy with a LOI value of higher than 70 and UL‐94 V‐0 rating. The SEM observation revealed that TLCP‐AEs had good fibrillation ability. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1182–1189, 2010     

Parallel signaling-based fast restoration scheme in distributed optical networks

The fast parallel restoration （FPR） scheme is proposed to achieve the fast setup of restoration label switched path （LSP） in the distributed optical networks. The scheme is derived by dividing the whole restoration LSP into several segments of sub-LSP and triggering each sub-LSP along the new route to finish the signaling procedure concurrently, and subsequently merging all sub-LSPs into a whole LSP. The theoretical analysis and simulation results show that the FPR scheme outperforms the other two typical restoration schemes in terms of connection setup time.     

类比思维在物理解题中的应用

尽管类比不能代替论证,但可以为理解新知识、概念和规律提供依托,做为一种"从特殊推到特殊的科学方法"在物理学中有着广泛的应用.现将中学物理解题中常见的类比推理方法归纳整理如下.     

Isolation and purification of recombinant human plasminogen Kringle 5 by liquid chromatography and ammonium sulfate salting‐out

In this work, a novel method was established to isolate and purify Human plasminogen Kringle 5 (HPK5) as a histidine‐tagged fusion protein expressed in Escherichia coli BL21 (DE3). This method consisted of sample extraction using a Ni‐chelated Sepharose Fast‐Flow affinity column, ammonium sulfate salting‐out and Sephadex G‐75 size‐exclusion column in turn. The purity analysis by SDS–PAGE, high‐performance size‐exclusion and reversed‐phase chromatographies showed that the obtained recombinant fusion HPK5 was homogeneous and its purity was higher than 96%; the activity analysis by chorioallantoic membrane model of chicken embryos revealed that the purified recombinant HPK5 exhibited an obvious anti‐angiogenic activity under the effective range of 5.0–25.0 µg/mL. Through this procedure, about 19 mg purified recombinant fusion HPK5 can be obtained from 1 L of original fermentation solution. Approximate 32% of the total recombinant fusion HPK5 can be captured and the total yield was approximately 11%. Copyright © 2013 John Wiley & Sons, Ltd.