Recently there has been a great deal of attention in the oilfield industry focused on the phenomenal properties of viscoelastic surfactants (VES). The interest is motivated by their applications as switchable smart fluids, their surface tension, and their thickening and rheology enhancement in aqueous solution. Surfactant molecules in solution are known for their ability to assemble spontaneously into complex structures. Under certain thermodynamic conditions, temperature and electrolyte concentrations, wormlike micelles are formed. These micelles share similar equilibrium and dynamic properties with polymer solutions, However, micellar chains can break and recombine spontaneously which make them part of the more general class of living polymers. It is vital to understand the properties of viscoelastic wormlike micelles with regard to their flow in porous media. The overall objective of this study is to establish a better understanding of counterion effect on behavior of VES. The dependence of macroscopic properties on intermolecular interactions of complex fluid systems such as VES is an enormous challenge. To achieve our objective, we use first-principle calculations and molecular dynamics (MD) simulations to resolve the full chemical details in order to study how the structure of the micellar and solution properties depends on the chemical structure of the surfactant head group (HG) and type of counterion. In particular, we run simulations for different structures in gas-phase and aqueous solutions together with their salt counterions at room temperature and atmospheric pressure. For this purpose, we consider four types of surfactant HG (anionic, cationic, betaine and amidoamine oxide) together with the most common ions present in the acidizing fluid of a carbonate reservoir such as Ca2+, Mg2+, Fe2+, Fe3+, Mn2+ and Zn2+, Cl-, OH- and HS-. Hydration of ions as well as interactions with surfactant the HG are studied using density functional theory (DFT). The results give important insight into the links between molecular details of VES HG structure and observed solution properties. This study proposes for the first time the possible mechanisms that explain the exotic behavior of VES at high Fe(III) concentration. Also, our MD simulation suggests that distribution of chloride ion around surfactant molecules is responsible for their viscosity behavior in HCl solution. We believe that our results are an important step to develop more systematic procedures for the molecular design and formulation of more effective and efficient VES systems.

Thesis (D. Min.)--Trinity Evangelical Divinity School, 1999. / Abstract. Includes bibliographical references (leaves 268-278).

Hydrogen sensor technology is a crucial component for safety and many other practical concerns in the hydrogen economy. To achieve a desired sensor performance, proper choice of sensing material is critical, because it directly affects the main features of a sensor, such as response time, sensitivity, and selectivity. Palladium is well-known for its ability to sorb a large amount of hydrogen. Most hydrogen sensors use Pd-based sensing materials. Since hydrogen sensing is based on surface and interfacial interactions between the sensing material and hydrogen molecules, nanomaterials, a group of low dimensional systems with large surface to volume ratio, have become the focus of extensive studies in the potential application of hydrogen sensors. Pd nanowires and Pd-coated carbon nanotubes have been successfully used in hydrogen sensors and excellent results have been achieved. Motivated by this fact, in this dissertation, we perform theoretical modeling to achieve a complete and rigorous description of molecular interactions, which leads to the understanding of molecular behavior and sensing mechanisms.To demonstrate the properties of Pd-based sensing materials, two separate modeling techniques, but with the same underlying aim, are presented in this dissertation. Molecular dynamic simulations are applied for the thermodynamic, structural and dynamic properties of Pd nanomaterials. Ab initio calculations are utilized for the study of sensing mechanism of Pd functionalized single wall carbon nanotubes. The studies reported in this dissertation show the applications of computational simulations in the area of hydrogen sensors. It is expected that this work will lead to better understanding and design of molecular sensor devices.

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Nanocrystalline (NC) metals with averaged grain size smaller than 100 nm have shown promising mechanical properties such as higher hardness and toughness than conventional coarse-grained metals. Unlike conventional metals in which the deformation is controlled by dislocation activities, the microstructural evolution in NC metals is mainly dominated by grain rotation and stress-driven grain boundary motion (SDGBM) due to the high density of grain boundaries (GBs). SDGBM is thus among the most studied modes of microstructural evolution in NC materials with particular interests on their fundamental atomistic mechanisms. In the first part of this thesis, molecular dynamics simulations were used to investigate the influences of Triple Junctions (TJs) on SDGBM of symmetric tilt GBs in copper by considering a honeycomb NC model. TJs exhibited asymmetric pinning effects to the GB migration and the constraints by the TJs and neighboring grains led to remarkable non-linear GB motion in directions both parallel and normal to the applied shear. Based on these findings, a generalized model for SDGBM in NC Cu was proposed. In the second part, the interaction of SDGBM with crack, voids and precipitates was investigated. It was found that depending on the GB structure, material type and temperature, there is a competition between different atomistic mechanisms such as crack healing, recrystallization and GB decohesion. It is hoped that the findings of this work could clarify the micro-mechanisms of various experimental phenomena such as grain refinement in metals during severe plastic deformation, which can be used to design optimized route of making stabilized bulk NC metals. / February 2016

This thesis focus on the analysis of spin-lattice NMRD relaxation profilesmeasured in various complex systems such as proteins, zeolites and ionicliquids. Proton, deuterium and fluoride T1-NMRD relaxation profiles wereobtained from a fast-field cycling (FFC) instrument. It is found that alsopossible to obtain NMRD profiles from the molecular dynamics (MD)simulation trajectories. NMRD Profiles were analyzed by using differentrelaxation models, such as the Solomon-Bloembergen-Morgan (SBM) theoryand the Stochastic Liouville (SL) theory. Paper I described the hydration of protein PrxV obtained from a MDsimulation, and compared with the picture emerges from an analysis byusing a generally accepted relaxation model [appendix C]. The result showsthat the information from NMRD analysis is an averaged picture of watermolecules with similar relaxation times; and the MD simulations containsinformation of all types of interested water molecules with differentresidence times. In paper II NMRD profiles have been used to characterize the hydration ofthe oxygen-evolving complex in state S1 of photosystem II. NMRDexperiments were performed on both intact protein samples and Mndepletedsamples, and characteristic dispersion difference were foundbetween 0.03 MHz to 1 MHz; approximately. Both the SBM theory and theSL theory have been used to explain this dispersion difference, and it isfound that this is due to a paramagnetic enhancement of 1-2 water moleculesnearby ~10 Å from the spin center of the Mn4CaO5 cluster. The result showsthe reorientation of the molecular cluster is in μs time interval. Whencompare these two theories, the SL theory presented a better interpretationbecause parameters obtained from the SBM theory shows they didn’t fulfilthe presupposed perturbation criterion (the Kubo term). Paper III deals with the water dynamics in the restricted/confined spaces inthe zeolite samples (H-ZSM-5 and NH4-ZSM-5) and obtained by proton anddeuterium spin-lattice NMRD profiles. The results show that the spin-latticeNMRD can be used to characterize various zeolites. The temperature has aweak effect on the relaxation rate R1, but the change of different counter ionsmay change the hydration and the translational diffusion pores and givedifferent R1. Proton and fluoride NMRD profiles and MD simulations were both used tostudy the dynamics of BMIM[PF6] in paper IV. Results indicate the reorientation of the molecules are in the ns time regime, and the effectivecorrelation time obtained from 1H and 19F are the same. From the MDsimulation it is found the reorientation of [PF6]- ions is much faster (in ps)compare with BMIM+ ion which moves in the ns time range. With previous results, the FFC NMRD profiles are indeed very informativetools to study the molecular dynamics of complex systems. The MDsimulation can be used as a complementary method to obtain detailedinformation. By combine these two methods, it provide a more colorfulpicture in the study of protein hydration and liquid molecular dynamics.

Background: Gliomas are neuroepithelial tumours classified by cell type and grade. In adults, low-grade gliomas are comprised mainly of astrocytomas and oligodendrogliomas grade II. The aim was to non-invasively characterise suspected low-grade gliomas through use of 11C-methionine-PET and physiological MRI in order to facilitate treatment decisions. Materials and methods: Patients with suspected low-grade glioma were prospectively and consecutively included after referral to the Neurosurgical Department, Uppsala University Hospital, between February 2010 and February 2014. All patients underwent morphological MRI, perfusion MRI, diffusion MRI and 11C-methionine PET. The institutional review board approved the study, and written informed consent was obtained prior to participation from each patient. Results: 11C-methionine PET hot spot regions corresponded spatially with regions of maximum relative cerebral blood volume in dynamic susceptibility contrast (DSC) perfusion MRI. The skewness of the transfer constantin dynamic contrast-enhanced (DCE) perfusion MRI, and the standard deviation of relative cerebral blood flow in DSC perfusion MRI could most efficiently discriminate between glioma grades II and III. In diffusion MRI, tumour fractional anisotropy differed between suspected low-grade gliomas of different neuropathological types. Quantitative diffusion tensor tractography was applicable for the evaluation of tract segment infiltration. Conclusion: PET and physiological MRI are able to characterise low-grade gliomas and are promising tools for guiding therapy and clinical decisions before neuropathological diagnosis has been obtained.

RNA tetraloop is the smallest, simplest and the most frequent motif which is involved in numerous important biological functions. A local deviation from the RNA standard tetraloop, d2 tetraloop, has been identified with high abundance in 5S, 16S and 23S rRNAs. The presence of d2 tetraloops in highly conserved regions of 16S and 23S rRNAs suggests their functional importance. With one less residue in the loop, d2 tetraloops are considered more energetically restrained and less stable than standard tetraloops. The deletion at position j+2 in the loop is always correlated with adjacent stem distortion. MD simulations of 314-d2-tetraloop (a sample structure of d2 tetraloops) and cutd2-tetraloop (an artificially built perfect d2 tetraloop with no stem defects) have shown that stem defects are the stabilizing factor of d2 tetraloops. Simulations have also revealed that the insertion residue 318C (an example of stem defect) is stabilizing 314-d2-tetraloop by forming hydrogen bonding interactions with both the loop and the stem. When these two hydrogen bonding interactions are eliminated, the structure remained relatively stable compared to cutd2-tetraloop where the insertion residue was completely removed from the stem. This suggests the insertion residue is also stabilizing 314-d2-tetraloop by providing some conformational relaxation in the stem. Investigation of RNA standard tetraloop high temperature unfolding has revealed that the d2 tetraloop is possibly a kinetically trapped intermediate state during the folding of the standard tetraloop. High temperature unfolding simulations of standard tetraloop have shown a three-state folding behavior: a folded state, an intermediate state and an unfolded state. The folding of standard tetraloop starts with the formation of the loop. The closing base pair forms first, followed by the loop and the stem which form critical interactions such as base pairing and stacking that make a tetraloop. ROMP PNB has been investigated as supports to immobilize homogeneous catalysts to achieve both high reactivity and selectivity and easy separation. Polymers with intermediate conformational order can increase the accessibility of tethered homogeneous catalysts. Simulations of ROMP PNBDC_UD have shown the importance of bulky side groups in enabling the polymer to adopt a helical conformation. Such helical conformations have been associated with intermediate structural order in similar polymers such as PNB made by non-ROMP mechanisms. This intermediate order manifests itself as a split in the amorphous halo of WAXD pattern. Bulk simulations generated WAXD patterns that are close to the experimentally generated WAXD patterns where there are two split peaks: lower angle peak representing intermolecular interaction and higher angle peak representing intramolecular interaction.

Thesis (Ph. D.)--Catholic University of America, 1929. / The first chapter gives a résumé of Bruté's career from 1779 to 1810, and the last chapter, of the concluding years of his life, 1834-1839. Published also in slightly different form as part of the author's larger work, "Simon Bruté de Rémur, first bishop of Vincennes." Bibliography: p. 123-125.

Thesis (D. Min.)--Westminster Theological Seminary, Philadelphia, 1993. / Includes bibliographical references (leaves 197-202).