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- Lin, Lili
(författare)
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Theoretical Modeling of Intra- and Inter-molecular Charge Transport
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on theoretical study of charge transportproperties in molecular systems. The understanding of the transportprocess and mechanism in molecular systems is essential forthe design of new functional molecular materials and molecularelectronic devices. The molecular junctions and organic molecularcrystals have been used as the model systems to highlight the usefulnessof theoretical modelling. A molecular junction is a system that consists ofone or several molecules sandwiched between two electrodes.The charge transport in molecular junctions is a very complex processthat is affected by the interaction between molecules and electrodes,the surroundings, as well as electron-electron (e-e) andelectron-phonon (e-p) couplings. When the molecule-electrode couplingis strong, the transport process can be very quick. If the e-p couplingis weak, the inelastic tunneling has only negligible contributions to thetotal current and the elastic electron tunneling plays the dominant role.Furthermore, the hopping process becomes dominant in the case of strong e-pcoupling, for which the geometric relaxation of the molecule needsto be considered. In this thesis, we have examined these three kinds oftransport processes separately. The first studied system is a molecular junction consisting of aromaticallycoupled bimolecules. Its elastic electron tunneling property is simulatedusing Green's functional theory at density functional theory level.The dependence of the conductance of bimolecular junctions on the vertical distances,horizontal distances and the tilt angles has been systematically studied. Theinelastic electron tunneling spectra (IETS) of molecular junctions have beencalculated for several systems that were experimentally measured with conflictingresults and controversial assignments. Our calculations provide the reliableassignments for the experimental spectra and revealed unprecedented detailsabout the molecular conformations within the junctions under different conditions.It demonstrates that a combined theoretical and experimental IETS study is capableof accurately determining the structure of a single molecule inside the junction.The hopping process is a dominant charge transfer process in organic molecularcrystals. We have studied the charge transport ability of four kinds of n-typeorganic semiconductor materials to find out the related structure-to-propertyrelationship. It is done by adopting the quantum charge transfer rate equationcombined with the random walk approach.
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| 2. |
- Lin, Na, 1981-
(författare)
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Theoretical Studies on Electronic and Vibrationally Resolved Multi-Photon Absorption and Dichroism
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents time-dependent density functional theory studies on electronic and vibronically resolved linear and nonlinear optical absorption and dichroism spectra of organic molecules. Special attention has been paid to the influence of solvent environment and molecular vibrations on one-, two- and three-photon absorption and one- and two-photon circular dichroism. It is found that dielectric medium as described by polarizable continuum model can enhance remarkably three-photon absorption cross section of a highly conjugated fluorene derivative, for which the simplified two-state model is shown to be largely inadequate. Origin-invariant density functional calculations on one- and two-photon circular dichroisms of a chiral molecule confirm that the recently developed CAMB3LYP functional performs better than the popular B3LYP functional for Rydberg-states. The first experimental measurement of TPCD spectra is performed on an axial chiral system in tetrahydrofunan, where the double L-scan technique is applied. Theoretical calculations well reproduce the experimental profiles when both the electron correlation and the solvent effect are taken into account. Vibronically resolved one- and two-photon absorption spectra of charge-transfer molecules have been obtained using a Linear Coupling model, where the 'borrowing mechanism' for the so-called Herzberg-Teller contribution is analyzed in detail. It is shown that Herzberg-Teller contribution can introduce a change of sign to the chiral responses of a molecule without the involvement of different electronic states, which has important consequences for the assignment of absolute configurations of chiral molecules. Adiabatic harmonic Franck-Condon model is also applied to simulate vibronically resolved one- and two-photon circular dichroism spectra of the same chiral system, where the sign-inversion and the interference between Franck-Condon and Herzberg-Teller contributions are also observed.
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| 3. |
- Lin, Yi-Ting, 1981-
(författare)
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Proteomic, metabolomic, and microbiome studies of blood pressure
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hypertension is a major risk factor for cardiovascular disease and premature death with a substantial global economic burden. To prevent and treat hypertension, it is crucial to improve our understanding of the pathophysiological mechanisms. Hypertension is a multifactorial condition influenced both by genetic and environmental factors. Detailed measurement of the molecular composition in plasma (“omics”) and the gut microbiota can enable novel biological understanding. The overall aim of this thesis was to investigate the associations of proteins, metabolites, and gut microbiome composition with blood pressure and blood pressure changes over time.Study I investigated the associations of 79 proteins with 5-year blood pressure progression using a proximity extension assay. Only renin was significantly associated with blood pressure stage progression in discovery cohort. In the replication cohort, the association was attenuated and not statistically significant. However, in all three cohorts combined, higher baseline renin was associated with higher blood pressure at follow-up.Study II investigated the longitudinal associations of 220 metabolites with 5-year blood pressure progression using gas chromatography mass spectrometry and liquid chromatography-tandem mass spectrometry. Levels of ceramide (d18:1,C24:0), triacylglycerol (C16:0,C16:1), total glycerolipids, and oleic acid (C18:cis[9]1) were positively associated, and cholesterylester C16:0 was negatively associated, with diastolic blood pressure change in the discovery cohort. Of the five top findings in the discovery cohort, two had related metabolites with a similar chemical structure that were also associated with diastolic blood pressure change over time in an independent cohort (the glycerolipids diacylglycerol (36:2) and monoacyl-glycerol (18:0)).Study III investigated the prevalence, variability, and reproducibility of blood pressure phenotypes based on office and 24-hour ambulatory measurements in SCAPIS (Swedish CArdioPulmonary BioImage Study), a large community-based cohort. The total sample size was 5881 participants (3026 women), with a mean office blood pressure of 125/77 mmHg and mean 24-hour ambulatory blood pressures of 124/76 mmHg. Approximately one-third of the participants had evidence of white-coat hypertension, similar to the proportion that had evidence of masked hypertension.Study IV investigated the associations between gut microbiota species and 24-hour ambulatory blood pressure in the SCAPIS study. We found robust evidence of a positive association of Dorea longicatena, and a negative association of Alistipes sp. 6CPBBH3, with the 24-h mean systolic blood pressure and diastolic blood pressure.This thesis demonstrated the utility of high-throughput omics technologies to identify proteins, metabolites and gut microbiota species associated with blood pressure phenotypes, and highlights the large problem of uncontrolled hypertension.
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