搜狗浏览器1.4正式版评测

说到目前上网速度最快的浏览器,搜狗浏览器的名字一定会被提及。凭借着＂全网加速＂和＂多任务异步浏览＂这两项业内首创的技术,搜狗浏览器一举成为上网最流畅的浏览器之一。而近日,搜狗浏览器又推出了1.4正式版。新加入了网络收藏夹、Windows7新特性完美支持等功能。笔者有幸在第一时间对这款软件进行深度评测。     

Activating a zymogen without proteolytic processing: mutation of Lys15 and Asn194 activates trypsinogen

The zymogen and mature enzyme forms of trypsin-like serine proteases exhibit a wide range of activities. The prototypical trypsinogen-trypsin system is an example of a minimally active zymogen and a maximally active mature protease. The present work identifies several features of trypsinogen which govern its activity. Our results indicate that rat trypsin is 10(8)-fold more active than rat trypsinogen. Rat trypsinogen appears to be less active than bovine trypsinogen. His40 is believed to be an important determinant of zymogen activity. We are unable to verify this role for His40 in trypsinogen since the mutation of His40 to Phe appears to change the trypsin-substrate interface. Deletion of the N-terminal Ile16 from trypsin is expected to produce a trypsinogen-like protein since the Ile16-Asp194 salt bridge cannot form. Such mutants have higher activity and BPTI affinity than trypsinogen, which indicates that the activation peptide stabilizes the inactive trypsinogen conformation. The mutation of Lys15 to Ala increases the BPTI affinity and activity of trypsinogen to an even greater extent; thus, removal of Lys15 can account for the effect of the loss of the activation peptide. These results suggest that Lys15 is an important determinant of zymogen activity. The mutation of Asp194 to Asn also increases the BPTI affinity and activity of trypsinogen. This result suggests that in addition to stabilizing the active conformation of trypsin via the Ile16-Asp194 salt bridge, Asp194 also maintains the inactive conformation of trypsinogen. A correlation exists between the values of kcat/Km and BPTI affinity of mutant trypsinogens and trypsins. However, the slope of this correlation is 0.64, which indicates that different "active" conformations are involved in BPTI binding and substrate hydrolysis. DeltaI16V17 trypsinogen is the lone outlier; its BPTI affinity is higher than would be expected based on the value of kcat/Km. We show that the rate of BPTI association is slower for DeltaI16V17 trypsinogen than for a mutant trypsinogen with a similar BPTI affinity. This observation suggests that BPTI binds to an "active" trypsinogen conformation that is not kinetically accessible to substrates.     

BIOLOGICAL SYSTEMS AS ORGANIZATIONAL PARADIGMS†

It is suggested that biological systems provide the best source of paradigms for the consideration of the kinds of organizations which we find in human systems; social, political or economic. A brief review of the several ways in which biological activities can be mathematically modelled is given, together with indications of the manner in which these ideas can be extended and applied beyond biology.     

WEAKENING STRONG BLACK POLITICAL EMPOWERMENT: IMPLICATIONS FROM ATLANTA'S 2009 MAYORAL ELECTION

Atlanta is perhaps the city with the greatest degree of black political empowerment (BPE) in the United States. Yet in 2009 a relatively weak white mayoral candidate nearly won the general and runoff elections over a field of stronger black candidates. Why? Treating Atlanta as a prototypical case, the article examines factors that undermine the capacity of blacks to retain control of mayoralties in strong BPE cities, with an emphasis on disruptions to black electorates, discontent among black citizens, and reinvestment in electoral politics by whites at the local level.     

Symmetrical overhead in flow networks

Recent work by one of the authors has identified the average mutual information and the conditional entropy as two measures from information theory that are useful in quantifying the system organization and incoherence, respectively. While the scaled average mutual information, or network ascendency, is inherently symmetrical with respect to inputs and outputs, the scaled conditional entropy, or overhead, remains asymmetrical. Employing the joint entropy, instead of the conditional entropy, to characterize the overhead, results in a symmetrical overhead and also permits the decomposition of the system capacity, or complexity, into components useful in following the response of the whole system to perturbations.     

URBAN POLICY,PRESS, AND PLACE: CITY‐MAKING IN FLORIDA'S MIAMI‐DADE COUNTY

This article enhances the notion of city‐making by explicating its communicative processes and functions within the press. Through a quantitative content analysis and qualitative textual analysis of Miami Herald news coverage related to incorporation and annexation policies and practices over a period of 3 years, we argue for a stronger implication of the press in coverage of local policy‐ and place‐making. Through a quantitative content analysis of 437 articles from the Miami Herald about communities affected by incorporation and annexation and a qualitative textual analysis of 51 articles related to general coverage of geographic policy‐making in Miami‐Dade County over a 3‐year period, we argue that this coverage reveals the press as being a central feature and function of policy‐making through the lens of city‐making.     

COMPLEXITY AND ERROR IN SOCIAL DYNAMICS

A model of cultural dynamics based on the work of Colin Renfrew is briefly described. It is shown how the general concepts of complexity and error pertain to this kind of cultural model. In particular, it is suggested that conflict in cultural contexts arises through the generation of diverse simple models of the culture, created by different members of the culture. We indicate how general system-theoretic concepts can thus be brought to bear on problems of conflict in and between cultures.     

Milling parameter optimization through a discrete variable transformation

Although milling is one of the most common chip metal removal processes, little has been done to aid in identifying the optimum operational conditions for milling processes. In this paper, a mathematical model for milling operations is developed and the five primary control variables identified. The model is then decomposed and an efficient optimization procedure developed for control variable identification.     

Minimal realizations of transfer-function matrices by means of matrix continued fraction

The matrix continued fraction technique is utilized to obtain the minimal realization of a transfer-function matrix with various inputs and outputs. If the ratio of the rank and the order of a square transfer-function matrix is an integer and there are no numerically ill-conditional elements in the matrix, then the matrix Routh algorithm is applied for the minimal realization. A method is also presented to deal with ill-conditional cases.     

Contribution of Lipids to Volatiles Generation in Extruded Corn-Based Model Systems

Volatile compounds generated by model systems of zein, corn amylopectin and corn oil extruded at barrel temperatures of 120°C and 165°C were analyzed by GC and GU/MS. The largest quantities of lipid oxidation products were detected in systems containing all three components. In each system, the quantity of 2,4-decadienal was low relative to the quantities of hexanal, heptanal, and benzaldehyde. Identification of the Maillard reaction products, 2-methyl-3(or 6)-pen-tylpyrazine, 2-methyl-3(or 6)-hexylpyrazine, and 2,5-dimethyl-3-pen-tylpyrazine, suggested that lipid-derived aldehydes might be involved in the formation of substituted pyrazines.