Hydration effects turn a highly stretched polymer from an entropic into an energetic spring

Polyethylene glycol (PEG) is a structurally simple and nontoxic water-soluble polymer that is widely used in medical and pharmaceutical applications as molecular linker and spacer. In such applications, PEG’s elastic response against conformational deformations is key to its function. According to text-book knowledge, a polymer reacts to the stretching of its end-to-end separation by a decrease in entropy that is due to the reduction of available conformations, which is why polymers are commonly called entropic springs. By a combination of single-molecule force spectroscopy experiments with molecular dynamics simulations in explicit water, we show that entropic hydration effects almost exactly compensate the chain conformational entropy loss at high stretching. Our simulations reveal that this entropic compensation is due to the stretching-induced release of water molecules that in the relaxed state form double hydrogen bonds with PEG. As a consequence, the stretching response of PEG is predominantly of energetic, not of entropic, origin at high forces and caused by hydration effects, while PEG backbone deformations only play a minor role. These findings demonstrate the importance of hydration for the mechanics of macromolecules and constitute a case example that sheds light on the antagonistic interplay of conformational and hydration degrees of freedom

Measuring self-differentiation and academic commitment in University students : a case study of education and engineering students

More than half of university students in South Africa leave university before they complete their studies. Factors associated with student drop out include poor schooling, lack of fluency in the language of instruction, poor financial support, and inadequate student support services. In the present study, we focus on the way meaningful commitment influences self-regulation, and we draw on the investment model of commitment to examine the hypothesis that commitment will be related to satisfaction, quality of alternatives, and investment size, and that self-differentiation will provide additional predictive power to commitment. Results indicate that satisfaction and self-differentiation only are significant predictors of level of academic commitment. Meaningful commitment is predicted by satisfaction, quality of alternatives, investment, and self-differentiation to a lesser extent. Investment size was associated significantly with self-regulatory behaviours such as setting learning goals, managing studies effectively, and spending more time on studies. The results are discussed in terms of the literature on commitment, self-differentiation, and academic achievement in higher education.http://www.sap.sagepub.comhb201

Metal-assisted and solvent-mediated synthesis of two-dimensional triazine structures on gram scale

We thank the German Science Foundation (DFG) for financial support within the grants SFB 765 and SFB 658. M.F.G. and J.P.R. also acknowledge the support of the Cluster of Excellence “Matters of Activity. Image Space Material” funded by the DFG under Germany’s Excellence Strategy EXC 2025-390648296. Furthermore, A.T. acknowledges the DFG for funding within the project TH 1463/12-1. We thank Dr. Andreas Schäfer and Maiko Schulze for solid NMR experiments and we appreciate the effort of Vahid Ahmadi Soureshjani in MALDI-TOF experiments. We acknowledge M. Eng. Jörg M. Stockmann for operating the XPS instrument at the BAM and Prof. Stephanie Reich and Dr. Antonio Setaro for fruitful discussions. 2DTs-HRTEM and -EELS studies were conducted at the Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragon, Universidad de Zaragoza, Spain. R.A. gratefully acknowledges the support from the Spanish Ministry of Economy and Competitiveness (MINECO) through project grant MAT2016-79776-P (AEI/FEDER, UE) and from the European Union H2020 programs ETN projects “Graphene Flagship” (785219 and 881603), FLAG-ERA - Graphene (MICINN) GATES (PCI2018-093137) and “ESTEEM3” (823717).Peer reviewe

Self-differentiation, pride and commitment of university students

In the present study the overarching aim was to investigate the relationship between commitment, self-differentiation and pride in undergraduate university students with the view to achieve a better understanding of the extent to which identity-related factors such as self-differentiation and pride as a self-relevant emotion may shape the strength of commitments in a higher education setting. Findings of the study may contribute to the literature on the psychology of academic commitment by distinguishing it from academic engagement (Baldwin & Koh, 2012) and by broadening the study of commitment to include identity-related constructs in the development of academic commitment (Lord, Diefendorff, Schmidt & Hall, 2010). I argue that a well-differentiated self is relevant to academic commitment because it may provide coherency and consistency in commitments. Academic commitment was operationalised as the extent to which students experience their studies as a source of satisfaction and meaning, the extent to which they have invested resources in their studies, and the quality of alternatives available (Rusbult, Martz & Agnew, 1998). I examined self-differentiation in terms of the ability to take an I-position in the absence of Emotional Reactivity, Emotional Cutoff and Fusion with Others (Skowron & Friedlander, 1998). Authentic pride was described as a self-relevant emotion consisting of two dimensions, namely Authentic and Hubristic pride (Tracy & Robins, 2007d). The Meaning Maintenance Model (MMM) as discussed by Heine, Proulx & Vohs (2006) was the conceptual framework that guided the study. A quantitative cross-sectional survey was asked for the implementation of a questionnaire that consisted of demographic factors, the Academic Commitment Scale (ACS), the Differentiation of Self Inventory (DSI-R) and the Authentic and Hubristic Pride Scales (AHP). A pilot study was conducted to test the new Academic Commitment Scale’s reliability and construct validity. A one-stage random cluster sampling method was used to complete a sample of undergraduate students from two faculties at the same university. Results of the main study were reported in Chapter 4 and a discussion of findings and conclusions, as well as the contribution, limitations and recommendations for future research were addressed in Chapter 5. Findings of the study indicate that commitment as an identity-level construct, related to identity-related constructs such as differentiation of self and pride, can be utilised in a higher education setting to differentiate between high performance students and students at risk of failure. The results can thus assist policy makers, lecturers, educationists and psychologists to achieve a better understanding of the factors underpinning academic success on the one hand and student dropout on the other hand, in order to develop appropriate support programs. A main feature of the study was the development of a new scale to measure commitment in an academic context. The Academic Commitment Scale was created based on an adapted version of the Rusbult et al. (1998) Investment Model. Meaningfulness was added as a fifth subscale which turned out to be a strong predictor of academic commitment.Thesis (PhD)--University of Pretoria, 2014.gm2014Educational Psychologyunrestricte