Calculation of the force field required for nucleus deformation during cell migration through constrictions

During cell migration in confinement, the nucleus has to deform for a cell to pass through small constrictions. Such nuclear deformations require significant forces. A direct experimental measure of the deformation force field is extremely challenging. However, experimental images of nuclear shape are relatively easy to obtain. Therefore, here we present a method to calculate predictions of the deformation force field based purely on analysis of experimental images of nuclei before and after deformation. Such an inverse calculation is technically non-trivial and relies on a mechanical model for the nucleus. Here we compare two simple continuum elastic models of a cell nucleus undergoing deformation. In the first, we treat the nucleus as a homogeneous elastic solid and, in the second, as an elastic shell. For each of these models we calculate the force field required to produce the deformation given by experimental images of nuclei in dendritic cells migrating in microchannels with constrictions of controlled dimensions. These microfabricated channels provide a simplified confined environment mimicking that experienced by cells in tissues. Our calculations predict the forces felt by a deforming nucleus as a migrating cell encounters a constriction. Since a direct experimental measure of the deformation force field is very challenging and has not yet been achieved, our numerical approaches can make important predictions motivating further experiments, even though all the parameters are not yet available. We demonstrate the power of our method by showing how it predicts lateral forces corresponding to actin polymerisation around the nucleus, providing evidence for actin generated forces squeezing the sides of the nucleus as it enters a constriction. In addition, the algorithm we have developed could be adapted to analyse experimental images of deformation in other situations.

Generous Attitudes and Online Participation

Some of the most popular websites depend on user-generated content produced and aggregated by unpaid volunteers. Contributing in such ways constitutes a type of generous behavior, as it costs time and energy while benefiting others. This study examines the relationship between contributions to a variety of online information resources and an experimental measure of generosity, the dictator game. Results suggest that contributors to any type of online content tend to donate more in the dictator game than those who do not contribute at all. When disaggregating by type of contribution, we find that those who write reviews, upload public videos, write or answer questions, and contribute to encyclopedic collections online are more generous in the dictator game than their non-contributing counterparts. These findings suggest that generous attitudes help to explain variation in contributions to review, question-and-answer, video, and encyclopedic websites.

INFLUENCE OF EARTH COMPOSITION ON ADSORPTION CAPACITY OF METHYLENE BLUE DYE

Final properties of unfired earth are influenced by composition of earth mixtures. Methylene blue test could be useful method for analysis of earth composition. This would facilitate of designing unfired earth building structures because composition of natural earth is various. Principle of methylene blue test is measure of amount of adsorbed methylene blue dye by clay. The essential component of earth mixtures is clay because clay fulfils a function of binder. Experimental measure of adsorption capacity of individual kind of clay is described in this paper. Adsorption capacity was investigated in montmorillonite, kaolinite, illite-kaolinite and illite clays. The obtained results show that the adsorption capacity of clays is significantly different.

Antibiotic resilience: a necessary concept to complement antibiotic resistance?

Resilience is the capacity of systems to recover their initial state or functions after a disturbance. The concepts of resilience and resistance are complementary in ecology and both represent different aspects of the stability of ecosystems. However, antibiotic resilience is not used in clinical bacteriology whereas antibiotic resistance is a recognized major problem. To join the fields of ecology and clinical bacteriology, we first review the resilience concept from ecology, socio-ecological systems and microbiology where it is widely developed. We then review resilience-related concepts in microbiology, including bacterial tolerance and persistence, phenotypic heterogeneity and collective tolerance and resistance. We discuss how antibiotic resilience could be defined and argue that the use of this concept largely relies on its experimental measure and its clinical relevance. We review indicators in microbiology which could be used to reflect antibiotic resilience and used as valuable indicators to anticipate the capacity of bacteria to recover from antibiotic treatments.

Computational and experimental studies on the index of antiaromaticity for 4n π-systems (n ≥ 2)

A method to evaluate the relative hardness of 4n π-systems (n ≥ 2) as a new experimental measure of antiaromaticity has been developed.

Gender, Competitiveness, and Study Choices in High School: Evidence from Switzerland

Willingness to compete has been found to predict individual and gender differences in educational choices and labor market outcomes. We provide further evidence for this relationship by linking Swiss students' Baccalaureate school (high school) specialization choices to an experimental measure of willingness to compete. Boys are more likely to specialize in math in Baccalaureate school. In line with previous findings, competitive students are more likely to choose a math specialization. Boys are more likely to opt for competition than girls and this gender difference in competitiveness could partially explain why girls are less likely to choose a math-intensive specialization.