Numerical model of the human cornea based on stromal microstructure: identification of mechanical properties for two age groups

The optical quality of the human eye mainly depends on the refractive performance of the cornea. The shape of the cornea is a mechanical balance between intraocular pressure and tissue intrinsic stiffness. Several surgical procedures in ophthalmology alter the biomechanics of the cornea to provoke local or global curvature changes for vision correction. Legitimated by the large number of surgical interventions performed every day, the demand for a deeper understanding of corneal biomechanics is rising to improve the safety of procedures and medical devices. The aim of our work is to propose a numerical model of corneal biomechanics, based on the stromal microstructure. Our novel anisotropic constitutive material law features a probabilistic weighting approach to model collagen fiber distribution as observed on human cornea by Xray scattering analysis (Aghamohammadzadeh et. al., Structure, February 2004). Furthermore, collagen cross-linking was explicitly included in the strain energy function. Results showed that the proposed model is able to successfully reproduce both inflation and extensiometry experimental data (Elsheikh et. al., Curr Eye Res, 2007; Elsheikh et. al., Exp Eye Res, May 2008). In addition, the mechanical properties calculated for patients of different age groups (Group A: 65-79 years; Group B: 80-95 years) demonstrate an increased collagen cross-linking, and a decrease in collagen fiber elasticity from younger to older specimen. These findings correspond to what is known about maturing fibrous biological tissue. Since the presented model can handle different loading situations and includes the anisotropic distribution of collagen fibers, it has the potential to simulate clinical procedures involving nonsymmetrical tissue interventions. In the future, such mechanical model can be used to improve surgical planning and the design of next generation ophthalmic devices.

An Exploratory Study about Microblogging Acceptance at Work

Microblogging is the new Web 2.0 hype in the media. Techies, politicians, family members and many more use Twitter to keep in touch with their interest groups, their voters or their friends and relatives. We wanted to know whether Twitter can also keep us aware about our team colleagues, how this improves teamwork and finally why Twitter is accepted and used in teams. Based on an action research study about Twitter usage in a team of seven researchers and the findings of prior literature, we attempt to extend the unified theory of technology acceptance (Venkatesh 2003) and adapt it to the specific context of microblogging in teams. Extending the performance expectancy construct, we propose two groups of factors inherent to social software that should be integrated into the UTAUT: the task characteristics of other users and the individual motivations for using social software

The coevolution of cooperation and dispersal in social groups and its implications for the emergence of multicellularity

Background Recent work on the complexity of life highlights the roles played by evolutionary forces at different levels of individuality. One of the central puzzles in explaining transitions in individuality for entities ranging from complex cells, to multicellular organisms and societies, is how different autonomous units relinquish control over their functions to others in the group. In addition to the necessity of reducing conflict over effecting specialized tasks, differentiating groups must control the exploitation of the commons, or else be out-competed by more fit groups. Results We propose that two forms of conflict – access to resources within groups and representation in germ line – may be resolved in tandem through individual and group-level selective effects. Specifically, we employ an optimization model to show the conditions under which different within-group social behaviors (cooperators producing a public good or cheaters exploiting the public good) may be selected to disperse, thereby not affecting the commons and functioning as germ line. We find that partial or complete dispersal specialization of cheaters is a general outcome. The propensity for cheaters to disperse is highest with intermediate benefit:cost ratios of cooperative acts and with high relatedness. An examination of a range of real biological systems tends to support our theory, although additional study is required to provide robust tests. Conclusion We suggest that trait linkage between dispersal and cheating should be operative regardless of whether groups ever achieve higher levels of individuality, because individual selection will always tend to increase exploitation, and stronger group structure will tend to increase overall cooperation through kin selected benefits. Cheater specialization as dispersers offers simultaneous solutions to the evolution of cooperation in social groups and the origin of specialization of germ and soma in multicellular organisms.

The Function of Norms and Values in the Construction of Social Identity in Groups who experienced intergroup Conflicts

I present my explorative research about conflict and social identity. The Social Identity Approach of Henri Tajfel and John Turner is used as theoretical frame in the study. The main question is how the construction of social identity of group members is influenced by an inter-group conflict. The research project consists of two parts: 1. An empirical study conducted with qualitative research methods to investigate a today’s congregation of the Swiss reformed Church who experienced a conflict about twenty years ago. This conflict ended by the separation of a sub-group from the congregations. This group forms an independent community today. Members of both congregations where interviewed about the meaning which membership has for them and about their interpretation of the conflict. 2. An analysis of the Gospel of Matthew with questions who where developed out of the empirical study and the Social Identity Approach to better understand the separation conflict between the Matthean community and the synagogue.

The role of chance events in the school-to-work transition: The influence of demographic, personality and career development variables

Chance events are considered important in career development, yet little empirical research is available on their predictors and consequences. The present study investigated socio-demographic (gender, nationality, school-type), personality (openness, locus of control) and career development variables (career decidedness, career planning) in relation to perceived chance events with a retrospective (N = 229, eleventh grade), and 1-year longitudinal prospective study (N = 245, eighth/ninth grade) among Swiss adolescents. The results showed that the majority of both groups reported a significant influence of chance events on their transition from compulsory school to vocational education or high school. Importance of chance events related to socio-demographics and personality but not career preparation. Career preparation and chance events predicted subjective career success in terms of wish correspondence and overall satisfaction with transition outcome among the younger cohort. Implications include the necessity to integrate both thorough career preparation and chance events in theory and counseling practice.

Sheaf representations of MV-algebras and lattice-ordered abelian groups via duality

We study representations of MV-algebras -- equivalently, unital lattice-ordered abelian groups -- through the lens of Stone-Priestley duality, using canonical extensions as an essential tool. Specifically, the theory of canonical extensions implies that the (Stone-Priestley) dual spaces of MV-algebras carry the structure of topological partial commutative ordered semigroups. We use this structure to obtain two different decompositions of such spaces, one indexed over the prime MV-spectrum, the other over the maximal MV-spectrum. These decompositions yield sheaf representations of MV-algebras, using a new and purely duality-theoretic result that relates certain sheaf representations of distributive lattices to decompositions of their dual spaces. Importantly, the proofs of the MV-algebraic representation theorems that we obtain in this way are distinguished from the existing work on this topic by the following features: (1) we use only basic algebraic facts about MV-algebras; (2) we show that the two aforementioned sheaf representations are special cases of a common result, with potential for generalizations; and (3) we show that these results are strongly related to the structure of the Stone-Priestley duals of MV-algebras. In addition, using our analysis of these decompositions, we prove that MV-algebras with isomorphic underlying lattices have homeomorphic maximal MV-spectra. This result is an MV-algebraic generalization of a classical theorem by Kaplansky stating that two compact Hausdorff spaces are homeomorphic if, and only if, the lattices of continuous [0, 1]-valued functions on the spaces are isomorphic.

Promising anchoring groups for single-molecule conductance measurements

The understanding of the charge transport through single molecule junctions is a prerequisite for the design and building of electronic circuits based on single molecule junctions. However, reliable and robust formation of such junctions is a challenging task to achieve. In this topical review, we present a systematic investigation of the anchoring group effect on single molecule junction conductance by employing two complementary techniques, namely scanning tunneling microscopy break junction (STM-BJ) and mechanically controllable break junction (MCBJ) techniques, based on the studies published in the literature and important results from our own work. We compared conductance studies for conventional anchoring groups described earlier with the molecular junctions formed through π-interactions with the electrode surface (Au, Pt, Ag) and we also summarized recent developments in the formation of highly conducting covalent Au–C σ-bonds using oligophenyleneethynylene (OPE) and an alkane molecular backbone. Specifically, we focus on the electron transport properties of diaryloligoyne, oligophenyleneethynylene (OPE) and/or alkane molecular junctions composed of several traditional anchoring groups, (dihydrobenzo[b]thiophene (BT), 5-benzothienyl analogue (BTh), thiol (SH), pyridyl (PY), amine (NH2), cyano (CN), methyl sulphide (SMe), nitro (NO2)) and other anchoring groups at the solid/liquid interface. The qualitative and quantitative comparison of the results obtained with different anchoring groups reveals structural and mechanistic details of the different types of single molecular junctions. The results reported in this prospective may serve as a guideline for the design and synthesis of molecular systems to be used in molecule-based electronic devices.

Latent profiles of work motivation in adolescents in relation to work expectations, goal engagement, and changes in work experiences

Motivation plays a key role in successful entry into working life. Based on a cross-sectional and a one-year longitudinal study, we used a person-centered approach to explore work-related motivation (i.e., autonomous goals, positive affect, and occupational self-efficacy) among 577 students in 8th grade (Study 1) and 949 adolescents in vocational training (Study 2). Based on latent profile analysis, in both studies we identified four groups that were characterized by different levels of overall motivation and one group characterized by low positive affect and mean levels in autonomous goals and self-efficacy. Profiles characterized by high levels of motivation showed the highest levels of positive work expectations and goal engagement and the lowest levels of negative work expectations in Study 1 and the highest levels of person-job fit, work engagement, and job satisfaction in Study 2. Moreover, latent difference score analysis showed that motivational profiles predicted changes in person-job fit and work engagement across one year but not in job satisfaction. The results imply that career counselors should be aware of characteristic motivational patterns of clients that may require specific counseling approaches.

Chance Events and Career Decidedness: Latent Profiles in Relation to Work Motivation

Research has shown that chance events affect careers but has not established the nature of their effects. Moreover, the relationship between chance and career decidedness is not well understood. The present study used a person-centered approach with latent profile analysis to examine 312 Swiss adolescents in their first year of vocational training. We identified five qualitatively differing profiles according to levels of perceived chance events and career decidedness: balanced scorers, undecided with mean chance, undecided with high chance, decided with chance, and decided without chance. The groups differed significantly in work motivation (i.e., occupational self-efficacy beliefs, perceived person-job fit, and work engagement). Decided adolescents reported more favorable work motivation regardless of their level of perceived chance events. The results imply that promoting decidedness remains a valuable goal in career counseling despite the occurrence of unpredicted events.