Spin dependent electron transport in chiral molecules, the so-called chirality induced spin selectivity (CISS) effect, have attracted much attention over the past few years. Experimentally the spin polarization has been detected, and there is a theoretical consensus on the necessity of both spin-orbit coupling and geometrical helicity in order to get a non-vanishing spin polarization. Several model Hamiltonians has been proposed to describe the CISSS effect, and while they can yield spin polarization agreeing with the experimentally observed magnitudes, they are relying on unrealistic values of the spin orbit interaction parameters. In recent years the importance of electron correlation has been emphasized. Thus, this thesis presents the general theory on how to treat the CISS effect as a many body problem, taking electron correlation into account. The Hamiltonian modelling is described and one approach on how to treat the helical structure of the molecule and the spin-orbit coupling is presented. Building on this thesis, further studies will hopefully lead to a first principle understanding of the CISS effect.

Syfte: Studiens syfte var att ta reda på om det finns någon korrelation mellan fixationsdisparitet och dissocierad fori på nära håll samt deras korrelation till symtom.   Metod: Mätningarna utfördes på totalt 57 personer mellan 12-45 år. De deltagare som hade någon form av tropi eller ett stereoseende sämre än 100 bågsekunder uteslöts. Mätningarna utfördes på 40 cm avstånd och för att mäta den dissocierade forin användes Modifierad Thorington. För att mäta fixationsdispariteten användes Saladin kort. Deltagarna fick fylla i en symtomenkät som bestod av 15 frågor och med hjälp av denna kunde man avgöra om deltagarna var symtomatiska eller ej.   Resultat: Det fanns en svag men positiv statistisk signifikant korrelation mellan fixationsdisparitet och dissocierad fori (r = 0,35; p <0,001). Två av deltagarna hade motsatt riktning på den dissocierade forin och fixationsdispariteten, dessa hade exofori med eso fixationsdisparitet. Varken forier eller fixationsdisparitet hade någon korrelation till symtom, men deltagarna med en högre poäng på symtomenkäten hade exofori.   Slutsats: Det finns en svag positiv korrelation mellan dissocierad fori och fixationsdisparitet. Det kunde inte hittas någon korrelation mellan fixationsdisparitet och symtom eller mellan forier och symtom, detta kan bero på att en grupp som var relativt asymtomatisk undersöktes. / The aim of this study was to investigate if there is any correlation between fixation disparity and dissociated phoria at near. Additionally a second aim was to evaluate if correlation between symptom questionnaire (CISS), dissociated phoria and fixation disparity exists.   The measurements were performed on a total of 57 people between the ages of 12-45 years old. The participants with any tropia and stereopsis less than 100 sec of arc were excluded. A subjective refraction was performed to make sure that the subjects were fully corrected. Modified Thorington was used to measure the dissociated phoria and the fixation disparity was measured with a Saladin card. All measurements were performed at a distance of 40 cm. To evaluate subject’s symptoms, a symptom questionnaire (CISS) with 15 questions was used.   A regression analysis showed a weak but statistically significant positive correlation between dissociated phoria and fixation disparity (r = 0.35; p <0.001). Two of the participants had a opposite direction on the dissociated phoria and the fixation disparity, they had exophoria and eso fixation disparity. Neither dissociated phorias or fixation disparity were correlated to symptoms. The subjects with higher points on the symptom questionnaire were shown to have exophoria.   There was a weak positive correlation between dissociated phoria and fixation disparity at near. A similar correlation between fixation disparity and symptoms could not be found, between neither dissociated phoria and symptoms or fixation disparity and symptoms. This could be because a relatively asymptomatic group was examined.

No description available.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24904号 / 工博第5184号 / 新制||工||1990(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 関 修平, 准教授 須田 理行, 教授 生越 友樹, 教授 水落 憲和 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The spin dynamics within a chiral and achiral molecule was investigated. It was investigated through a diminishing periodic potential, depicting the molecules being dropped onto a substrate. Born-Oppenheimers approximation and a tight-binding model was used to describe the molecules. Moreover, Schrödingers equation was defined for the problem and an iterative approach was used to solve it. The results indicated an induced spin selectivity for the chiral molecule, which varied over time. In contrast, the achiral molecule exhibited weaker spin selectivity. This difference might lie in how the spin couples to the linear momentum in the different structures.

Over the past two decades, chirality induced spin selectivity (CISS) has emerged as its own field of research. As a phenomenon, it reveals how the shape of molecules interplay with electron dynamics, showcasing how a helical molecule acts as a filter for electron spins, and thus, provides valuable insights into the correlation between molecular structure and electron properties. The interpretation is that the influence of the helical molecular structure, along with spin-orbit interaction and non-equilibrium conditions causes the charge-carrying electrons to become spin-polarized. Consequently, the structure of these molecules effectively filters electrons based on their spin direction. In this project, we investigate the time evolution of the probability densities for each spin as well as the spin polarization in a simplified model of the helical molecule under non-equilibrium. The problem is treated both analytically for a simpler case and numerically for a more general one. In the more general case, the solutions are divided into two parts, namely 1) The unperturbed system, to determine the properties of the system, and 2) The perturbed system, to investigate consequences of different types of perturbations. Two types of sources of perturbation were considered, namely metals, both magnetic and non-magnetic, and external electric fields, where these are assumed both constant and time-dependent, such as harmonic or decaying. The results from the analytical and numerical models turned out to give essentially the same results, however a larger molecule than the very smallest was required to display the expected symmetry of spin polarization between helicities. The properties of the unperturbed system were consistent withprevious research, and the perturbations had a varying effect, with the magnetic metals producing distinct changes to the spin polarization while the electric field mostly shifted the total charge.

Syfte: Syftet med denna studie var att undersöka om ett kortare synavstånd till smartphone resulterar i mer ögonrelaterade symtom. Metod: Deltagarna var slumpmässigt tillfrågade mellan åldrarna 19 och 37 år. Deltagarna (n=63) fick svara på symtomenkäten Convergence insufficience symptom survey (CISS) gällande närseende och läsning. Under tiden mättes synavståndet mellan deltagarnas ögon och smartphone. Symtomenkäten var webbaserad och deltagarna svarade med sin smartphone. Höjden på versalen [H] mättes och tillsammans med synavståndet räknades synvinkeln ut. Resultat: 76% av deltagarna var kvinnor, 22% var män och 2% saknade könstillhörighet. Deltagarnas medelålder var 24 år. Studien indikerade inte på ett statistiskt signifikant samband (r=0,219, p=0,102) mellan CISS-poäng och synavstånd till smartphone. Däremot indikerades en svag korrelation mellan de två variablerna. Resultatet visade även att endast 2 deltagare i studien hade en mindre synvinkel än 16 bågminuter. Slutsats: Denna studie fann inget statistiskt signifikant samband mellan synavstånd till smartphone och astenopiska besvär. Däremot påvisar studien en svag korrelation mellan synavstånd till smartphone och astenopiska besvär.

The physical origin of the so-called chirality-induced spin selectivity (CISS) effect has puzzled experimental and theoretical researchers over the past few years. Early experiments were interpreted in terms of unconventional spin–orbit interactions mediated by the helical geometry. However, more recent experimental studies have clearly revealed that electronic exchange interactions also play a key role in the magnetic response of chiral molecules in singlet states. In this investigation, we use spin-polarized closed-shell density functional theory calculations to address the influence of exchange contributions to the interaction between helical molecules as well as of helical molecules with magnetized substrates. We show that exchange effects result in differences in the interaction properties with magnetized surfaces, shedding light into the possible origin of two recent important experimental results: enantiomer separation and magnetic exchange force microscopy with AFM tips functionalized with helical peptides.