This paper suggests that the energy flow on which all living structures depend only started up slowly, the low-energy, initial phase starting up a second, slightly more energetic phase, and so on. In this way, the build up of the energy flow follows a bootstrapping process similar to that found in the development of computers, the first generation making possible the calculations necessary for constructing the second one, etc. In the biogenetic upstart of an energy flow, non-metals in the lower (...) periods of the Periodic Table of Elements would have constituted the most primitive systems, their operation being enhanced and later supplanted by elements in the higher periods that demand more energy. This bootstrapping process would put the development of the metabolisms based on the second period elements carbon, nitrogen and oxygen at the end of the evolutionary process rather than at, or even before, the biogenetic event. (shrink)

This paper reviews and extends ideas of eukaryotization by endosymbiosis. These ideas are put within an historical context of processes that may have led up to eukaryotization and those that seem to have resulted from this process. Our starting point for considering the emergence and development of life as an organized system of chemical reactions should in the first place be in accordance with thermodynamic principles and hence should, as far as possible, be derived from these principles. One trend to (...) be observed is the ever-increasing complexity resulting in several layers of compartmentalization of the reaction system, either spatial (of which the eukaryotic cell is an example), or functional (as in the gradually deepening distinction between metabolic, enzymatic and information-storing functions within the cell). One of the causes of this complexification of living systems will have been the changes in environmental conditions, particularly the geochemical impoverishment of the biosphere during geological history, partly brought about by living systems themselves, and partly by the trend towards increasing efficiency and specificity of the reactions that occur. (shrink)

We obtain in this paper a representation of the formulae of extensions ofL by generalized quantifiers through functors between categories of first-order structures and partial isomorphisms. The main tool in the proofs is the back-and-forth technique. As a corollary we obtain the Caicedo's version of Fraïssés theorem characterizing elementary equivalence for such languages. We also discuss informally some geometrical interpretations of our results.

DNA double‐strand breaks (DSBs) are extremely hazardous lesions for all DNA‐bearing organisms and the mechanisms of DSB repair are highly conserved. In the eukaryotic mitotic cell cycle, DSBs are often present following DNA replication while, in meiosis, hundreds of DSBs are generated as a prelude to the reshuffling of the maternally and paternally derived genomes. In both cases, the DSBs are repaired by a process called homologous recombinational repair (HRR), which utilises an intact DNA molecule as the repair template. Mitotic (...) and meiotic HRR are managed by ‘checkpoints’ that inhibit cell division until DSB repair is complete. Here we attempt to summarise the substantial recent progress in understanding the checkpoint management of HRR in mitosis (focussing mainly on mammals) and then go on to use this information as a framework for understanding the presumed checkpoint management of HRR in mammalian meiosis. BioEssays 29:974–986, 2007. © 2007 Wiley Periodicals, Inc. (shrink)

Buildings are constructed for accommodating living and industrial needs. Floor cleaning robots have been developed to cater to the demand of these buildings. Area coverage and coverage time are crucial performance factors of a floor cleaning robot. Reconfigurable tiling robots have been introduced over fixed shape robots to improve area coverage in floor cleaning applications compared to robots with fixed morphologies. However, area coverage and coverage time of a tiling robot compromised one another. This study proposes a novel concept that (...) considers the ability of a tiling robot to configure both its morphology and size according to the environment. This concept is inspired by the pleomorphism that could be seen in bacteria. In this regard, P-hTetro, a pleomorphic tiling robot that can reconfigure its morphology and size, is considered. A novel coverage strategy for realizing the size reconfiguration is also proposed. According to this strategy, the robot covers obstacle-free areas with its maximum size, while an obstacle cluster is covered after shrinking to an optimum size. The optimum size for reconfiguration is determined by the genetic algorithm based on the arrangement of the environment. The performance and behavior of the proposed P-hTetro have been compared against that of an existing tiling robot which has a fixed size. According to the statistical outcomes, a tiling robot with the ability to reconfigure its size can significantly improve the performance in the aspects of area coverage and coverage time compared to a tiling robot with no ability to reconfigure its size. (shrink)

Background: Discussing treatment risks has become increasingly important in medical communication. Still, despite regulations, physicians must decide how much and what kind of information to present. Objective: To investigate patients’ preference for information about a small risk of a complication of colonoscopy, and whether medical and personal factors contribute to such preference. To propose a disclosure policy related to our results. Design: Vignettes study. Setting: Department of Gastroenterology, Academic Medical Centre, the Netherlands. Patients: 810 consecutive colonoscopy patients. Intervention: A home-sent (...) questionnaire containing three vignettes. Vignettes varied in the indication for colonoscopy, complication severity and level of risk. Patients were invited to indicate their wish to be informed and the importance of such information. In addition, sociodemograhic, illness-related and psychological characteristics were assessed. Main outcome measurements: Wish to be informed and importance of information. Results: Of 810 questionnaires, 68% were returned. Patients generally wished to be informed about low-risk complications, regardless of the indication for colonoscopy or the severity of the complication. The level of risk did matter, though (OR = 2.48, SE = 0.28, p = 0.001). The information was considered less important if done for population screening purposes or diagnosis of colon cancer, if the complication was less severe (bleeding) and if the risk was smaller (0.01% and 0.1%). Patients’ information preference was also related to age, mood and coping style. Limitations: Difficulty of vignettes. Conclusions: Patients generally wish to be informed about all possible risks. However, this might become uninformative. A stepwise approach is suggested. (shrink)

If self-interested behavior conflicts with the collective welfare, rules of cooperation are often installed to prevent egoistic behavior. We hypothesized that installing such rules may instigate personal moral norms of cooperation, but that they fail in doing so when installed by a leader who is self-interested rather than self-sacrificing. Three studies confirmed this and also showed that, consequently, only self-sacrificing leaders were able to install rules that increase cooperation without the need for a perfectly operating monitoring system.

Das Grab des Königs Ninetjer in Saqqara: Architektonische Entwicklung frühzeitlicher Grabanlagen in Ägypten. By Claudia M. Lacher-Raschdorff. Deutsches Archäologisches Institut Kairo, Archäologische Veröffentlichungen, vol. 125. Wiesbaden: Harrassowitz Verlag, 2014. Pp. 295, 44 pls., plans. €247.