Optimization of transport protocols in complex networks

In this paper, an optimal routing strategy is proposed to enhance the traffic capacity of complex networks. In order to avoid nodes overloading, the new algorithm is derived on the basis of generalized betweenness centrality which gives an estimate of traffic handled by the node for a route set. Since the nodes with large betweenness centrality are more susceptible to traffic congestion, the traffic can be improved, as our strategy, by redistributing traffic load from nodes with large betweenness centrality to nodes with small betweenness centrality in the proceeding of computing collective routing table. Particularly, depending on a parameter that controls the optimization scale, the new routing can not only enlarge traffic capacity of networks more, but also enhance traffic efficiency with smaller average path length. Comparing results of previous routing strategies, it is shown that the present improved routing performs more effectively.     

Sono-assisted preparation of highly-efficient peroxidase-like Fe3O4 magnetic nanoparticles for catalytic removal of organic pollutants with H2O2

Fe₃O₄ magnetic nanoparticles (Fe₃O₄ MNPs) with much improved peroxidase-like activity were successfully prepared through an advanced reverse co-precipitation method under the assistance of ultrasound irradiation. The characterizations with XRD, BET and SEM indicated that the ultrasound irradiation in the preparation induced the production of Fe₃O₄ MNPs possessing smaller particle sizes (16.5 nm), greater BET surface area (82.5 m² g^?1) and much higher dispersibility in water. The particle sizes, BET surface area, chemical composition and then catalytic property of the Fe₃O₄ MNPs could be tailored by adjusting the initial concentration of ammonia water and the molar ratio of Fe²⁺/Fe³⁺ during the preparation process. The H₂O₂-activating ability of Fe₃O₄ MNPs was evaluated by using Rhodamine B (RhB) as a model compound of organic pollutants to be degraded. At pH 5.4 and temperature 40 °C, the sonochemically synthesized Fe₃O₄ MNPs were observed to be able to activate H₂O₂ and remove ca. 90% of RhB (0.02 mmol L^?1) in 60 min with a apparent rate constant of 0.034 min^?1 for the RhB degradation, being 12.6 folds of that (0.0027 min^?1) over the Fe₃O₄ MNPs prepared via a conventional reverse co-precipitation method. The mechanisms of the peroxidase-like catalysis with Fe₃O₄ MNPs were discussed to develop more efficient novel catalysts.     

电化学促进铱催化乙烯基C—H键官能团化高效合成α-吡喃酮

电化学有机合成技术在过去十年来蓬勃发展,越来越受到学术和企业界合成化学工作者的青睐[1-5].跟传统化学反应相比,它的优势是利用电流代替常规的化学氧化剂或还原剂来促进化学反应,同时通过电势的调节,实现独特的反应性和化学选择性.电化学和过渡金属协同催化的碳氢键官能团化修饰(C-Hfunctionalization),不仅有效避免底物的预官能团化,而且为逆合成分析提供了可能的新颖断键方法,日益成为一种更为绿色经济的反应类型[6].     

Practical resolution of an atropoisomeric α,α-disubstituted glycine with l-phenylalanine cyclohexylamide as chiral auxiliary

l-Phenylalanine cyclohexylamide has been used as a chiral auxiliary for the medium-scale resolution of 2′,1′:1,2;1″,2″:3,4-dinaphthcyclohepta-1,3-diene-6-amino-6-carboxylic acid (Bin), an α,α-disubstituted glycine with only axial dissymmetry. Coupling of X–Bin–OH (X=Ac; Bz) with H–(l)-Phe–NH–C₆H₁₁ by the EDC/HOBt method gave the dipeptide diastereoisomers X–(R)-Bin–(l)-Phe–NH–C₆H₁₁ and X–(S)-Bin–(l)-Phe–NH–C₆H₁₁, which were separated by crystallization (X=Bz) and/or chromatography. Extensive acidic hydrolysis, followed by esterification of the resulting free amino acid enantiomers, led to enantiomerically pure (−)-(R)-H–Bin–OMe and (+)-(S)-H–Bin–OMe with high yields.     

Chemical composition and in vitro evaluation of the cytotoxic and antioxidant activities of supercritical carbon dioxide extracts of pitaya (dragon fruit) peel

Background

Hylocereus polyrhizus and Hylocereus undatus are two varieties of the commonly called pitaya fruits, and pitaya fruits have gained popularity in many countries all over the world. However, studies on chemical composition and the nutritional quality of pitaya flesh peel are limited.

Results

Extracts of pitaya (H. polyrhizus and H. undatus) peel were extracted by supercritical carbon dioxide extraction, and analyzed by gas chromatography–mass spectrometry analysis. Their cytotoxic and antioxidant activities were investigated. The main components of H. polyrhizus extract were β-amyrin (15.87%), α-amyrin (13.90%), octacosane (12.2%), γ-sitosterol (9.35%), octadecane (6.27%), 1-tetracosanol (5.19%), stigmast-4-en-3-one (4.65%), and campesterol (4.16%), whereas H. undatus were β-amyrin (23.39%), γ-sitosterol (19.32%), and octadecane (9.25%), heptacosane (5.52%), campesterol (5.27%), nonacosane (5.02%), and trichloroacetic acid, hexadecyl ester (5.21%). Both of the two extracts possessed good cytotoxic activities against PC3, Bcap-37, and MGC-803 cells (IC₅₀ values ranging from 0.61 to 0.73 mg/mL), and the activities of their main components were also studied. Furthermore, these extracts also presented some radical scavenging activities, with IC₅₀ values of 0.83 and 0.91 mg/mL, respectively.

Conclusion

This paper provides evidence for studying the chemical composition of supercritical carbon dioxide extracts of pitaya peel and their biological activity.     

High Carbon-Resistance Ni@CeO<Subscript>2</Subscript> Core–Shell Catalysts for Dry Reforming of Methane

Ni@CeO₂ core–shell catalysts were synthesized via a facile surfactant-assisted hydrothermal method and their catalytic performance in the dry reforming of methane (DRM) reaction was evaluated. A variety of techniques including XRD, N₂ adsorption–desorption, SEM, TEM, TPO, TGA were employed to characterize the prepared or spent catalysts. The encapsulation by the CeO₂ shell, on one side, can restrict the sintering and growth of Ni nanoparticles under harsh reaction conditions. On the other side, compared to the conventional shell material of SiO₂, CeO₂ can provide more lattice oxygens and vacancies, which is helpful to suppress coke deposition. Consequently, the Ni@CeO₂ core–shell catalysts exhibited better catalytic activity and stability in the DRM reaction with respect to the referenced Ni@SiO₂ core–shell catalysts and Ni/CeO₂ supported catalysts.     

Gamma-radiation combined with tricycloazole to protect tempera paintings in ancient Egyptian tombs (Nile Delta,Lower Egypt)

In order to comprehensively understanding the metabolism process of fluvastatin, the stable isotope-labeled (3R, 5S)-fluvastatin and (3S, 5R)-fluvastatin were required. Both of (3R, 5S)-fluvastatin and (3S, 5R)-fluvastatin were synthesized via a seven steps procedure starting from aniline and [²H₆] 2-bromopropane. Two versions of deuterium labeled compound revealed over 98% deuterium enrichment, using as an internal standard.

     

Detection of systemic pesticide residues in tea products at trace level based on SERS and verified by GC–MS

Analytical and Bioanalytical Chemistry - Surface-enhanced Raman spectroscopy (SERS) has the potential to detect pesticide residues in agricultural products. However, some systemic pesticides, such...     

Detect early stage lung cancer by a LAMP microfluidic chip system with a real-time fluorescent filter processor

This work presents a promising clinical molecular diagnostics for early stage lung cancer. This novel diagnostic method utilized the loop-mediated isothermal amplification (LAMP), microfluidic chips and a confocal optical detector with a non-linear fluorescent filter processor. An isothermal amplification based microfluidic chip for the early diagnostics of lung cancer was developed and a confocal optical detector was improved by a novel real-time fluorescent filter to sensitively monitor the DNA amplification procedure with high signal to noise ratio and fluorescence collecting ability. Experiment showed that a rapid diagnostic of lung cancer by detecting the existence of the CEA mRNA could be performed in only 5 μL of reaction assay in less than 45 min. While the traditional in-tube RT-PCR set consumed more than 25 μL of the assay and took more than 90 min.