Emergent friction in two-dimensional Frenkel-Kontorova models

Simple models for friction are typically one-dimensional, but real interfaces are two-dimensional. We investigate the effects of the second dimension on static and dynamic friction by using the Frenkel-Kontorova (FK) model. We study the two most straightforward extensions of the FK model to two dimensions and simulate both the static and dynamic properties. We show that the behavior of the static friction is robust and remains similar in two dimensions for physically reasonable parameter values. The dynamic friction, however, is strongly influenced by the second dimension and the accompanying additional dynamics and parameters introduced into the models. We discuss our results in terms of the thermal equilibration and phonon dispersion relations of the lattices, establishing a physically realistic and suitable two-dimensional extension of the FK model. We find that the presence of additional dissipation channels can increase the friction and produces significantly different temperature-dependence when compared to the one-dimensional case. We also briefly study the anisotropy of the dynamic friction and show highly nontrivial effects, including that the friction anisotropy can lead to motion in different directions depending on the value of the initial velocity.Comment: 14 pages, 13 figure

Fingerprints of light induced molecular transients from quantum chemical models of ultrafast x ray spectroscopy

Abstract Absorption of sunlight generates renewable electricity and powers the growth of plants, but also causes severe damage both to synthetic materials and biological tissue. The wildly varying outcomes of these light induced processes are ultimately determined by much slighter differences in their underlying reaction pathways, induced by the transient properties of shortlived and miniscule molecules; a powerful approach to their detection and characterization is offered by ultrafast x ray spectroscopy, with identification of spectral fingerprints and further guidance from quantum chemical models. This thesis contains the computational half of three experimentally joint projects that push the limits for detection of electronic, spin and structural dynamics of small molecular systems in solution. A wide selection of theoretical frameworks are combined to model various aspects of the measurements from multi configurational descriptions of non adiabatic couplings in the photo dynamics and multi electron transitions in the x ray spectroscopy, to affordable simulations of extensive aqueous solutions by density functional theory and classical mechanics. Applied to experimental data, the presented quantum chemical results allowed in particular to simultaneously identify molecular forms and electronic states of aqueous 2 thiopyridone, to determine a detailed pathway for its excited state proton transfer; characterize the charge transfer state of aqueous ferricyanide, to extend well known concepts from steadystate spectroscopy into the ultrafast domain; establish the newly implemented framework of multi configurational Dyson orbitals, as a powerful tool for simulation of photoelectron spectroscopy. A number of computational predictions are additionally presented for hitherto unexplored experimental regions, which may help to guide and optimize future measurement

Elastic constants and sound velocities of Fe0.87Mn0.13 random alloy from first principles

In this study the elastic properties of a fcc Fe0.87Mn0.13 random alloy are studied by ab initio calculations. Ground state lattice parameters and elastic properties are calculated with Density Functional Theory using the Exact Muffin-Tin Orbital method and the Coherent Potential Approximation. Several magnetic models, approximations and distortion techniques are evaluated for optimized results, which are obtained by a Disordered Local Moment model with the Frozen Core and Generalized Gradient approximations using volume-conserving distortions.  Conclusively the longitudinal sound velocities are calculated from second order elastic stiffness constants and visualized by two different codes. The importance of magnetism for elastic properties is confirmed, as is the usefulness of the optimized computational scheme; all quantities obtained via the scheme is in accord with earlier theoretical and experimental results. Volume-conserving distortions are found to be more precise than volume-altering for calculation of elastic constants but also to be highly dependent on the precision of bulk modulus determination. The two sound-velocity codes are in complete agreement

Another Anna and the new step of Thomas : A discourse analysis covering the altered representation by swedish newspapers of Anna Holmlund and Thomas Fogdö following disabilities

The aim of this thesis was to examine how the media representation of elite skiers Anna Holmlund and Thomas Fogdö was altered following their accidents resulting in disabilities. In order to examine this a critical discourse analysis was performed on 16 newspaper articles from Tidningarnas Telegrambyrå, Expressen, Dagens Nyheter, Göteborgs-posten, Sundsvalls Tidning and Aftonbladet, out of which eight of them had been published before the skiers respective accidents and the other eight afterwards. The results showed that swedish newspapers shifted their focus from how the skiers performed in competitions prior to their accidents to how their bodies functioned and how they would perform everyday tasks following the accidents. We found that this would distance Holmlund and Fogdö, representing them as deviants when compared to non-disabled people. In contrast to this we found that Holmlund and Fogdö would be allowed to talk about or show their lives and bodies in great detail. This would seem to function as a way of teaching non-disabled people of what it’s like to live with a disability. Through this Holmlund and Fogdö were represented as ambassadors for the disabled collective. We also found that there was a risk of objectification which would increase in connection with a decrease in Holmlund and Fogdö’s represented ability to communicate and function as a non-disabled person does. This also appears to increase the risk of having one’s voice excluded by other people talking in one’s place

Another Anna and the new step of Thomas : A discourse analysis covering the altered representation by swedish newspapers of Anna Holmlund and Thomas Fogdö following disabilities

The aim of this thesis was to examine how the media representation of elite skiers Anna Holmlund and Thomas Fogdö was altered following their accidents resulting in disabilities. In order to examine this a critical discourse analysis was performed on 16 newspaper articles from Tidningarnas Telegrambyrå, Expressen, Dagens Nyheter, Göteborgs-posten, Sundsvalls Tidning and Aftonbladet, out of which eight of them had been published before the skiers respective accidents and the other eight afterwards. The results showed that swedish newspapers shifted their focus from how the skiers performed in competitions prior to their accidents to how their bodies functioned and how they would perform everyday tasks following the accidents. We found that this would distance Holmlund and Fogdö, representing them as deviants when compared to non-disabled people. In contrast to this we found that Holmlund and Fogdö would be allowed to talk about or show their lives and bodies in great detail. This would seem to function as a way of teaching non-disabled people of what it’s like to live with a disability. Through this Holmlund and Fogdö were represented as ambassadors for the disabled collective. We also found that there was a risk of objectification which would increase in connection with a decrease in Holmlund and Fogdö’s represented ability to communicate and function as a non-disabled person does. This also appears to increase the risk of having one’s voice excluded by other people talking in one’s place

Female leaders in male dominated industries : The importance of roles

Bakgrund: Jämställdhetsbarometern (2020) visar att det fortfarande råder stora könsskillnader i det svenska arbetslivet. Att jämställdheten inte är optimal visar bland annat fördelningen av kvinnor respektive män på ledande positioner, där den största skillnaden av andelen kvinnor respektive män på chefspositioner finns inom mansdominerade branscher. Ledarrollen är förknippad med maskulina handlingskraftiga egenskaper som ses som synonymt med den manliga könsstereotypen. Den kvinnliga könssterotypen är i kontrast feminin, och diskrepansen mellan rollerna har resulterat i negativa konsekvenser för kvinnliga ledare. Sverige anno 2021 målas upp som ett jämställt land vilket borde medföra att problemen inte existerar i Sverige som de gör i andra nationella kontext.              Syfte: Syftet med studien var att undersöka hur följare ser på kvinnliga ledare och vilken typ av egenskaper de föredrar hos en ledare i en mansdominerad bransch i Sverige utifrån ett Implicit Leadership Theory, där bedömningen av kvinnliga ledare sätts i relation till Role Congruity Theory. Teoretisk referensram: Studien utgår från empiri inom Implicit Leadership Theory (ILT) och Role Congruity Theory (RCT). ILT är en ledarskapsteori som berör perceptionen av ledare och menar att ledarskap skapas av kognitiva kategoriseringar, som avgör vem som ses som ledare. RCT är en teori som uppkom genom en analys av de deskriptiva aspekterna av könsroller för att förstå hur könsfördomar möjligtvis skadar kvinnliga ledare. Metod: Den kvantitativa undersökningen, som utfördes i den här studien, genomfördes via en enkätstudie och riktades till medarbetare på en organisation inom verkstadsindustrin som hade en kvinnlig produktionsledare som närmsta chef. Slutsats: Det finns signifikanta samband mellan åsikter om kvinnor och andra faktorer, som vi anser berör ledarskap, i mansdominerade branscher. Fördomar verkar vara av betydelse när det kommer till preferensen av maskulina ledare samt om man upplever en kvinnlig ledare som effektiv eller inte. Resultatet från den här studien stödjer tidigare forskning som visade att maskulinitet och femininitet är något som har ett positivt samband till hur följare upplever ledare i relation till effektivitet. Däremot kan inga kausala slutsatser dras.Background: The Equality Barometer (2020) shows that gender differences are large in  Swedish work life. That equality isn’t optimal shows in the distribution of women, respectively men, in leading positions, where the largest difference in the amount of women respectively men can be seen in director/management level positions in male-dominated industries. The leader role is associated with masculine, agentic, characteristics which is seen as synonymous with the male gender stereotype. The female gender stereotype is, in contrast,feminine, and the discrepancy between roles have resulted in negative consequences for female leaders. Sweden year 2021 is branded as an equal country which should mean that the problems should not exist in Sweden to the same extent as they do in other national contexts. Purpose: The purpose with the study was to investigate how followers view female leaders and what kind of characteristics they prefer a ledare expresses, in a male-dominated industry in Sweden. This will be done from an Implicit Leadership Theory perspective, where the evaluation of female leaders are put in relation to the Role Congruity Theory. Theoretical framework: The study emanates from the empirical work within Implicit Leadership Theory (ILT) and Role Congruity Theory (RCT). ILT is a leadership theory which focuses on the perception of leaders and says that leadership is created out of cognitive categorisations which decide who is seen as a leader and who is not. RCT is a theory which arose from an analysis of the descriptive aspects of gender roles to understand how gender prejudice possibly harms female leaders. Method: The quantitative research, which was conducted in this study, was conducted through a survey and aimed at workers at an organisation within the engineering industry which had a female production manager as their closest boss. Conclusion: There are significant correlations between opinions about women and other factors, which we consider affect leadership, in a male-dominated industry in Sweden. Prejudice appears to be of significance when it comes to preference for masculine leaders and if female leaders are perceived as effective or not. The results from this study support previous research which showed masculinity and femininity as something with a positive 4correlation to how followers perceive leaders in relation to effectiveness. However, nofactitive conclusions can be made.

Ultrafast dynamics of photo-excited 2-thiopyridone : Theoretical insights into triplet state population and proton transfer pathways

Ultrafast non-adiabatic dynamics of the small heteroaromatic compound 2-thiopyridone has been studied with surface hopping simulations based on multi-configurational quantum chemistry. Initial excitation of the bright S-2(pi,pi*) state is found to promptly relax to S-1(n, pi*) through in-plane motion. The subsequent dynamics are oppositely driven by out-of-plane motion, which results in both complex population transfers among all the available states and intersystem crossing predominantly through the "El-Sayed forbidden" S-1(n, pi*) to T-2(n, pi*) channel, through significant mixing of electronic excitation characters. Despite this complexity, the femto- to picosecond triplet population, expected from several spectroscopic measurements, is well described as a simple exponential decay of the singlet state manifold. No proton transfer is found in the reported trajectories, but two mechanisms for its possible mediation in previously reported experiments are proposed based on the observed structural dynamics: (i) ultrafast intra-molecular transfer driven by the initially coherent in-plane motion and (ii) inter-molecular solvent-mediated transfer driven by the out-of-plane modes that dominate the later motion

Neural network approach for shape-based euhedral pyrite identification in X-ray CT data with adversarial unsupervised domain adaptation

We explore an attenuation and shape-based identification of euhedral pyrites in high-resolution X-ray Computed Tomography (XCT) data using deep neural networks. To deal with the scarcity of annotated data we generate a complementary training set of synthetic images. To investigate and address the domain gap between the synthetic and XCT data, several deep learning models, with and without domain adaption, are trained and compared. We find that a model trained on a small set of human annotations, while displaying over-fitting, can rival the human annotators. The unsupervised domain adaptation approaches are successful in bridging the domain gap, which significantly improves their performance. A domain-adapted model, trained on a dataset that fuses synthetic and real data, is the overall best-performing model. This highlights the possibility of using synthetic datasets for the application of deep learning in mineralogy