Mosaic origin of the eukaryotic kinetochore

The emergence of eukaryotes from ancient prokaryotic lineages embodied a remarkable increase in cellular complexity. While prokaryotes operate simple systems to connect DNA to the segregation machinery during cell division, eukaryotes use a highly complex protein assembly known as the kinetochore. Although conceptually similar, prokaryotic segregation systems and the eukaryotic kinetochore are not homologous. Here we investigate the origins of the kinetochore before the last eukaryotic common ancestor (LECA) using phylogenetic trees, sensitive profile-versus-profile homology detection, and structural comparisons of its protein components. We show that LECA’s kinetochore proteins share deep evolutionary histories with proteins involved in a few prokaryotic systems and a multitude of eukaryotic processes, including ubiquitination, transcription, and flagellar and vesicular transport systems. We find that gene duplications played a major role in shaping the kinetochore; more than half of LECA’s kinetochore proteins have other kinetochore proteins as closest homologs. Some of these have no detectable homology to any other eukaryotic protein, suggesting that they arose as kinetochore-specific folds before LECA. We propose that the primordial kinetochore evolved from proteins involved in various (pre)eukaryotic systems as well as evolutionarily novel folds, after which a subset duplicated to give rise to the complex kinetochore of LECA.

Bearing Length on Cold-Formed Sections

The effective bearing length of trapezoidal sheeting on cold formed sections at inner supports is 10 mm according to EN 1999-1-4 (aluminium) and EN 1993-1-3 (steel). In the original design provisions the effective bearing length on Z-sections was the actual width of the loaded flange. In order to find out the appropriate effective bearing length, FEM calculations were made on simply supported beams with C-, Z-and Sigma-cross-section. Contact elements between the trough of the trapezoidal sheeting and the loaded flange of the beam made it possible to evaluate the contact area. This area and the stresses in the trapezoidal sheeting show that the effective bearing length is very small for C-sections. For Z-sections and for Sigma sections with large folds in the web the contact area is the flange width, unless the flange width versus profile height is large and the plate thickness is small.

Political Parties and Political Representation

Although Sweden is characterized by a stable formal framework for political representation, major changes during recent decades have affected the conditions in which political representation is exercised. A once orderly five-party system has evolved into an unwieldy eight-party system, and turnover in the Riksdag has increased. Parties are challenged from the inside by an increased presence of previously excluded groups, such as women and foreign-born representatives. Analyzing a unique series of mail surveys to Swedish MPs from 1985–2010, the chapter reports congruence on left–right issues versus profile issues for newcomer parties, gender gaps in policy priorities and policy standpoints, and trends in citizens’ trust in representative institutions. The long-term perspective demonstrates that Swedish political parties are successful survivors. There is stability in policy agreement on left–right issues, and the increased number of parties and women MPs has meant stronger agreement between certain segments of MPs and voters.

"Why am i a volunteer?": building a quantitative scale

This paper aims to analyze the validity of a quantitative instrument to identify what attracts someone to volunteer work, as well as what makes them stay and what makes them quit such an activity. The theoretical framework lists aspects related to volunteer work, which is followed by a discussion on models of analysis of volunteer motivation. As to the objectives, this research is descriptive, since it presents the analysis of the validity of a quantitative instrument that seeks to understand and describe the reasons for volunteering at the Pastoral da Criança, a Brazilian NGO. This instrument is based on theoretical ideas by Souza, Medeiros and Fernandes (2006). Reliability - Cronbach's Alpha - reached values between 0.7 and 0.8. Regarding Kaiser-Meyer-Olkin measure of sampling adequacy a good index was also obtained: 0.74. Despite the good results of reliability and sampling adequacy of factor analysis, none of the variables resulted in the expected combination, namely: indicators versus profile. It is necessary to improve the semantic meaning of certain factors, or even increase the number of indicators so as to generate additional correlations among them.

Some Analytical Results on Transmission Errors in Narrow-Faced Spur and Helical Gears: Influence of Profile Modifications

Some theoretical developments are presented, which lead to approximate analytical results on quasi-static transmission errors valid for low and high contact ratio spur and helical gears. Based on a multidegree-of-freedom gear model, a unique scalar equation for transmission error is established. The role of profile relief is analyzed by using Fourier series and it is shown that transmission error fluctuations depend on a very limited number of parameters representative of gear geometry and profile relief definition. An original direct solution to the optimum relief minimizing transmission error fluctuations is presented, which is believed to be helpful for designers. The analytical results compare well with the numerical results provided by a variety of models and it is demonstrated that some general laws of evolution for transmission error fluctuations versus profile modifications can be established for spur and helical gears.