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排序方式: 共有301条查询结果,搜索用时 46 毫秒
51.
Florina Stefanoiu Laure Candy Carlos Vaca‐Garcia Elisabeth Borredon 《European Journal of Lipid Science and Technology》2008,110(5):441-447
Alkenyl succinic anhydrides (ASA) were obtained by reaction between maleic anhydride and high‐oleic sunflower oil (HOSO) esters. A kinetics study of the maleinization of alkyl esters indicated that the maleinization reaction was second order overall and first order with respect to the individual reactants, and the activation energy was 77.2 ± 3.3 kJ/mol in the investigated temperature range (185–225 °C). These results showed that the cis configuration and the central position of the double bond in HOSO esters facilitate the maleinization of the latter. On the contrary, the length of the linear ester moiety had no influence on the course of the maleinization reaction. Moreover, new evidence demonstrates that there are two different reaction mechanisms: ene‐reaction and addition in allylic position with a 2 : 1 ratio, respectively. This ratio was constant throughout the reaction, thus indicating that these mechanisms are independent. 相似文献
52.
Wigginton KR Menin L Sigstam T Gannon G Cascella M Hamidane HB Tsybin YO Waridel P Kohn T 《Chembiochem : a European journal of chemical biology》2012,13(6):837-845
Much research has been dedicated to understanding the molecular basis of UV damage to biomolecules, yet many questions remain regarding the specific pathways involved. Here we describe a genome-mediated mechanism that causes site-specific virus protein cleavage upon UV irradiation. Bacteriophage MS2 was disinfected with 254 nm UV, and protein damage was characterized with ESI- and MALDI-based FT-ICR, Orbitrap, and TOF mass spectroscopy. Top-down mass spectrometry of the products identified the backbone cleavage site as Cys46-Ser47 in the virus capsid protein, a location of viral genome-protein interaction. The presence of viral RNA was essential to inducing backbone cleavage. The similar bacteriophage GA did not exhibit site-specific protein cleavage. Based on the major protein fragments identified by accurate mass analysis, a cleavage mechanism is proposed by radical formation. The mechanism involves initial oxidation of the Cys46 side chain followed by hydrogen atom abstraction from Ser47 C(α). Computational protein QM/MM studies confirmed the initial steps of the radical mechanism. Collectively, this study describes a rare incidence of genome-induced protein cleavage without the addition of sensitizers. 相似文献
53.
This paper, which is based on the detailed analysis of the post-war archives of the French Christian union Confédération Fran?aise des Travailleurs Chrétiens (CFTC), which became the Confédération Fran?aise Démocratique du Travail (CFDT) in 1964, highlights the difficulties, both from a practical and ideological point of view, for a militant organisation to embrace the cause of immigrant workers and to give them a voice. The CFDT had to ‘construct’ immigrant workers as a group they could represent, which means as a group that relates to French workers, despite possible xenophobia. A key moment was the denunciation of their housing conditions that make immigrant workers not competitors in the job market but victims of injustice. The union had to reinvent its engagement frames in order to include the specific problems faced by the immigrant workforce. The study shows that the urban dimension was essential in this process as Paris slums made visible an important plight of migrants and provided the opportunity to change public opinion. 相似文献
54.
Wei Fan François Stoffelbach Jutta Rieger Laure Regnaud Angélique Vichot Bruno Bresson Nicolas Lequeux 《Cement and Concrete Research》2012,42(1):166-172
It is well-established that a competitive adsorption exists between polycarboxylate superplasticizers (SP) and sulfate ions solubilized in the interstitial solution of cement paste, which may cause a loss of the dispersing properties. This has been explained by competitive weak ionic interactions between functional carboxyl groups and sulfate ions with cement grains. In this study, SPs including trialkoxysilane functional groups have been synthesized. Adsorption and dispersing properties of these SPs were evaluated in the presence of different concentrations of Na2SO4 added in aqueous solution. It appeared that a partial substitution of carboxyl groups by trialkoxysilane in the polymer makes them more resistant to sulfate ions. We suggested that the high adsorption capacity of these SPs results from the formation of strong bonds between hydroxysilane groups and calcium silicate hydrate phases. The improved compatibility of these new silylated SPs has been demonstrated through the formulation of two different concrete equivalent mortars. 相似文献
55.
Barbara Lothenbach Laure Pelletier-Chaignat Frank Winnefeld 《Cement and Concrete Research》2012,42(12):1621-1634
The solubility of AH3, CAH10, C2AH7.5, and C3AH6 was determined experimentally at 7 to 40 °C and up to 570 days. During the reaction of CA, at 20 °C and above initially C2AH7.5 formed which was unstable in the long-term. The solubility products calculated indicate that the solubilities of CAH10, C2AH7.5 and C4AH19 increase with temperature while the solubility of C3AH6 decreases. Thus at temperatures above 20 °C, C3AH6 is stable, while at lower temperature also CAH10 and C4AH19 are stable, depending on the C/A ratio.At early hydration times, CAH10 can be stable initially at 30 °C and above, as the formation of amorphous AH3 stabilises CAH10 with respect to C3AH6 + 2AH3. With time, as the solubility AH3 decreases due to the formation of microcrystalline AH3, CAH10 becomes unstable at 20 °C and above. 相似文献
56.
Xi Wang Xinqiang Cao Laure Bourgeois Hasigaowa Guan Shimou Chen Yeteng Zhong Dai‐Ming Tang Huiqiao Li Tianyou Zhai Liang Li Yoshio Bando Dmitri Golberg 《Advanced functional materials》2012,22(13):2682-2690
A new facile route to fabricate N‐doped graphene‐SnO2 sandwich papers is developed. The 7,7,8,8‐tetracyanoquinodimethane anion (TCNQ?) plays a key role for the formation of such structures as it acts as both the nitrogen source and complexing agent. If used in lithium‐ion batteries (LIBs), the material exhibits a large capacity, high rate capability, and excellent cycling stability. The superior electrochemical performance of this novel material is the result from its unique features: excellent electronic conductivity related to the sandwich structure, short transportation length for both lithium ions and electrons, and elastomeric space to accommodate volume changes upon Li insertion/extraction. 相似文献
57.
58.
Protein digestion in two liquid dairy matrixes with different heat treatments (pasteurized and sterilized milks) and in one semi-liquid dairy matrix (stirred-yogurt) was investigated using an in vitro gastrointestinal digestion model. After buccal digestion, significantly lower amount of soluble proteins were measured in yogurt than in both milks. This difference between dairy matrixes decreased during gastric digestion and disappeared at the end of the duodenal digestion upon the proteolytic action of pepsin and pancreatin. Electrophoresis pattern of digested mixtures showed that casein digestion began at the gastric phase and was slower for pasteurized milk than sterilized milk and yogurt. At the end of duodenal digestion, no more intact caseins were present in all the dairy matrixes while faint bands of whey proteins were still visible for pasteurized milk and yogurt. The release of free amino acids during the duodenal phase varied according to their nature (acid, basic, neutral or hydrophobic) and seems to be governed by the specificity of the enzymes. These results suggest that the severity of milk's heat treatment influences the kinetics of protein digestion, mainly during the gastric phase, and that the impact of processing has to be considered to study protein digestion in dairy products. 相似文献
59.
The emergence of nanotechnology has coincided with an increased recognition of the need for new approaches to understand and manage the impact of emerging technologies on the environment and human health. Important elements in these new approaches include life-cycle thinking, public participation and adaptive management of the risks associated with emerging technologies and new materials. However, there is a clear need to develop a framework for linking research on the risks associated with nanotechnology to the decision-making needs of manufacturers, regulators, consumers and other stakeholder groups. Given the very high uncertainties associated with nanomaterials and their impact on the environment and human health, research resources should be directed towards creating the knowledge that is most meaningful to these groups. Here, we present a model (based on multi-criteria decision analysis and a value of information approach) for prioritizing research strategies in a way that is responsive to the recommendations of recent reports on the management of the risk and impact of nanomaterials on the environment and human health. 相似文献
60.