Three-Dimensional Quantification of Cellular Traction Forces and Mechanosensing of Thin Substrata by Fourier Traction Force Microscopy

We introduce a novel three-dimensional (3D) traction force microscopy (TFM) method motivated by the recent discovery that cells adhering on plane surfaces exert both in-plane and out-of-plane traction stresses. We measure the 3D deformation of the substratum on a thin layer near its surface, and input this information into an exact analytical solution of the elastic equilibrium equation. These operations are performed in the Fourier domain with high computational efficiency, allowing to obtain the 3D traction stresses from raw microscopy images virtually in real time. We also characterize the error of previous two-dimensional (2D) TFM methods that neglect the out-of-plane component of the traction stresses. This analysis reveals that, under certain combinations of experimental parameters (\ie cell size, substratums' thickness and Poisson's ratio), the accuracy of 2D TFM methods is minimally affected by neglecting the out-of-plane component of the traction stresses. Finally, we consider the cell's mechanosensing of substratum thickness by 3D traction stresses, finding that, when cells adhere on thin substrata, their out-of-plane traction stresses can reach four times deeper into the substratum than their in-plane traction stresses. It is also found that the substratum stiffness sensed by applying out-of-plane traction stresses may be up to 10 times larger than the stiffness sensed by applying in-plane traction stresses

A note on the combustion of blends of diesel and soya, sunflower and rapeseed vegetable oils in a light boiler

Producción CientíficaThis paper deals with the study of the vegetable oils (VO) used as fuel for heating. The properties of sunflower, rape and soya oils are studied and these are compared with the properties of C-diesel fuel (used for heating domestic purposes in Spain). The mixtures of VO and diesel are studied and characterized and, finally, the results of a series of combustion trials of the mixtures in a conventional heating installation with a mechanical pulverization burner are presented. The results show that viscosity of VO limits the use of blends up to 40% of them, and the oxygen present in their structures contributes to an efficiency gai

Sibling competition and not maternal allocation drives differential offspring feeding in a sexually size-dimorphic bird

Sex allocation models still fail to predict the complex sex ratio patterns in broods of vertebrates. A major problem when studying mother–brood interactions is the difficulty in disentangling hypotheses involving maternal preferences from processes that do not imply maternal manipulation. We studied maternal resource allocation in mixed-sex, same-sex and single-chick broods in the great bustard, Otis tarda. Females normally rear a single chick, and previous work has shown that maternal investment influences male more than female breeding success. Therefore, mothers of two-chick broods were assumed to be in good condition and candidates to show a preference for sons. Results showed that male chicks of mixed-sex broods remained close to the mother for twice as long as their sisters, and received double the number of maternal feedings. However, sex differences in maternal feeding rate disappeared when considering only simultaneous begging approaches from both siblings. Proximity to the mother and its interaction with begging approach intensity were the factors determining the higher begging success of male chicks. In single-chick broods, females did not receive fewer maternal feedings than males. Overall, our results suggest that female chicks of mixed-sex broods become outcompeted by their larger brothers, which remain close to the mother much longer, preventing their sisters from taking a larger share of maternal feedings. We conclude that mothers do not show a preference for feeding male over female chicks, and that the sex differences in feeding rate are determined by the higher food requirements of male chicks due to their sexually selected, much faster growth rates. The higher mortality of females in mixed-sex broods contrasts with the pattern of male-biased mortality typical in this species, and supports our interpretation of an asymmetric competitive ability of male offspring as the mechanism responsible for the sex bias in maternal expenditure.This work was supported by the Dirección General de Investigación Científica y Técnica (projects PB91-0081 and PB94-0068, with contributions from other projects awarded to J.C.A. for marking and radiotracking birds 1987–2013); the Instituto Nacional para la Conservación de la Naturaleza; and the Junta de Castilla y León. During the study, E.M. benefitted from a predoctoral fellowship of the Dirección General de Investigación Científica y Técnica. Research by J.C.A. and J.A.A. was supported by project CGL2012-36345 during the writing of the pape

Migration Patterns in Male Great Bustards (Otis tarda)

5 paginas, 1 figura y 1 tableThe Great Bustard (Otis tarda) is distributed from Iberia and Morocco in the west to China in the east and has been considered sedentary in all but the northern and eastern parts of its range (Gewalt 1959, Glutz et al. 1973, Cramp and Simmons 1980). However, some studies have reported seasonal changes in population numbers in different areas in the Iberian Peninsula (Hidalgo and Carranza 1990, Alonso et al. 1995), suggesting that the species is a partial migrant (sensu Terrill and Able 1988) in this region. We describe seasonal movements of marked adult male Great Bustards and discuss observed patterns in relation to the following questions: (1) Do migratory males display interannual fidelity to breeding and postbreeding areas? (2) Do males travel significantly farther than females in their seasonal movements? We also suggest several hypotheses that could explain patterns of partial and differential migration in male Great Bustards.This study is a contribution to DGICYT-project PB94–0068.Peer reviewe

Evaluation of captive breeding as a method to conserve threatened Great Bustard populations.

6 paginas y 1 tableThe recent Great Bustard Action Plan summarizes de main recommended lines of action to preserve current populations and their habitats in Europe. Among others, captive breeding is mentioned as a method to save clutches found in the field whose hatching success probability is suspected to be low for any reason. Birds hatched from these clutches have been used to either build up small captive-breeding flocks that ensure preservation of the genetic pool of seriously threatened populations once these may be extinct, or to be released into the natural populations as juveniles. In this paper we evaluate the viability of captive breeding in the light of new results of a recent study of juvenile Great Bustards during their maternal dependence period, family break-up and dispersal. The few data available on survival of captive-bred young after being released suggest that they suffer a high mortality, probably due to the lack of the experience acquired in natural conditions from their mothers. The negative effects of imprinting by their human keepers, particularly in relation with display and mating, has not been sufficiently investigated. These and other aspects make captive breeding questionable as an effective method, as compared with habitat protection measures.PB94-0068 of the Dirección General de Investigacion Cientifica y TecnicaPeer reviewe

Migration Patterns in Male Great Bustards (Otis tarda)

5 paginas, 1 figura y 1 tableThe Great Bustard (Otis tarda) is distributed from Iberia and Morocco in the west to China in the east and has been considered sedentary in all but the northern and eastern parts of its range (Gewalt 1959, Glutz et al. 1973, Cramp and Simmons 1980). However, some studies have reported seasonal changes in population numbers in different areas in the Iberian Peninsula (Hidalgo and Carranza 1990, Alonso et al. 1995), suggesting that the species is a partial migrant (sensu Terrill and Able 1988) in this region. We describe seasonal movements of marked adult male Great Bustards and discuss observed patterns in relation to the following questions: (1) Do migratory males display interannual fidelity to breeding and postbreeding areas? (2) Do males travel significantly farther than females in their seasonal movements? We also suggest several hypotheses that could explain patterns of partial and differential migration in male Great Bustards.This study is a contribution to DGICYT-project PB94–0068.Peer reviewe

Biological evolution and human cognition are analogous information processing systems

The mechanisms that govern biological evolution and human cognition are analogous, as both follow the same principles of natural information processing systems. In this article, we describe the following five principles that provide an analogy between biological evolution and human cognition: (a) Randomness as Genesis Principle and (b) Borrowing and Reorganizing Principle, which indicate how natural information processing systems obtain information; (c) Narrow Limits of Change Principle and (d) Information Store Principle, which indicate how information is processed and stored; and (e) Environmental Organizing and Linking Principle, which indicate how stored information is used to generate actions appropriate to an environment. In human cognition, these analogs only apply to cognitive processes associated with biologically secondary knowledge, the knowledge typically taught in educational institutions. Based on these five principles, cognitive load theory researchers have provided diverse prescriptions to optimize instructional activities and materials. We conclude by discussing general instructional implications and future research directions based on this analogy

Bacillus subtilis RecU Holliday-junction resolvase modulates RecA activities

The Bacillus subtilis RecU protein is able to catalyze in vitro DNA strand annealing and Holliday-junction resolution. The interaction between the RecA and RecU proteins, in the presence or absence of a single-stranded binding (SSB) protein, was studied. Substoichiometric amounts of RecU enhanced RecA loading onto single-stranded DNA (ssDNA) and stimulated RecA-catalyzed D-loop formation. However, RecU inhibited the RecA-mediated three-strand exchange reaction and ssDNA-dependent dATP or rATP hydrolysis. The addition of an SSB protein did not reverse the negative effect exerted by RecU on RecA function. Annealing of circular ssDNA and homologous linear 3′-tailed double-stranded DNA by RecU was not affected by the addition of RecA both in the presence and in the absence of SSB. We propose that RecU modulates RecA activities by promoting RecA-catalyzed strand invasion and inhibiting RecA-mediated branch migration, by preventing RecA filament disassembly, and suggest a potential mechanism for the control of resolvasome assembly

Nutritional Status of Non-Institutionalized Adults Aged over 65. Study of Weight and Health in Older Adults (PYSMA)

Background. A significant increase in the prevalence of malnourishment, obesity, and sarcopenic obesity has been observed in developed countries over the last few decades. In Spain, this especially happens in populations over 65 who are not institutionalized. Differences in lifestyle, medication, and economic capacity partially explain this increase. Objective. To study the nutritional status of a population of 65 year-olds and subjects who are not institutionalized, in the Cadiz region (Spain). Methods. Observational, transversal study carried out on 2621 subjects who are 65 years old and over, with a direct weight and height measurement, in 150 pharmacy offices from 44 locations. A mobile application was designed for homogeneous data collection in all the pharmacy offices. The data required from all subjects was gender, age, postal code, social security contribution regime, if the patient lives alone, type of food consumed as the main meals, level of physical activity, polypharmacy, weight, and height. Results. The prevalence of overweight and obesity amounts to 82.2% of the population (43.2% overweight and 39% obese). We found an inverse relationship between the prevalence of overweight and obesity with carrying out physical activity and having full dinners. Conclusion. We identify the need to reinforce the messages to the elderly aimed at maintaining adequate physical activity and assessing the quality and quantity of dinners, as well as reducing, as much as possible, the treatments that may lead to weight gain

Integrating cognitive load theory with other theories, within and beyond educational psychology

Background and Aims: The long-standing aim of cognitive load theory (CLT) has been to generate instructional design principles that show teachers how to instruct students effectively, based on knowledge of the intricacies of human cognitive architecture. Historically, the focus of CLT has been on identifying cognitive processes related to learning and instruction. However, the theory has become more multidisciplinary over time, drawing on theoretical perspectives both within, and beyond, educational psychology. Results: This Editorial presents a brief historical overview of key developments in CLT and seven key themes that are pertinent to research on CLT. These themes are as follows: Level of Expertise, Cognitive Load Measurement, Embodied Cognition, Self-Regulated Learning, Emotion Induction, Replenishment of Working Memory, and Two Subprocessors of Working Memory. Summaries of the nine empirical contributions to the special issue are presented and discussed in relation to how they provide insight into one or more of these themes. Conclusions: Understanding the variables that impact student learning and instruction has always represented the core aim of CLT. The growing multidisciplinary features of CLT should provide researchers and practitioners with more holistic perspectives of the factors that predict student learning and, in turn, guide instructional design