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DNA is the carrier of biological information and damage to DNA has been believed to be responsible for many diseases including aging and cancer. One electron oxidation by charge migration through DNA is one of the processes that lead to DNA damage. It is known that the guanine N1 imino proton can be transferred to the N3 of cytidine that is hydrogen bonded to it. Some reports have implication that this proton transfer and radical cation migration are coupled to each other. We have incorporated 5-fluoro-2 -deoxycytidine (F5dC) in place of normal dC in DNA duplexes. Although, the lower pKa of F5dC should perturb the proton transfer process from the guanine to it, we do not see any change in the charge migration ability compared to the strands having normal cytidines. However, there is a considerable decrease in the guanine damage, when there is F5dC opposite to it. These results indicate that the charge migration is not coupled with proton transfer process, but the change in basicity affects the reactivity of the guanine radical cation. We have also reported a systematic study on the charge migration through adenine (A) and thymidine (T) containing DNA strands. The damage has predominantly seen in thymidine, although from oxidation potentials reaction at adenine was expected. The thymidine reaction has been analyzed thoroughly. It has similar distance dependence property as the well known guanine damage. Study of thymidine damage in presence of radical scavengers, replacement of thymidines by Uracil and HPLC-MS study point toward reactions involving tandem lesion. On the basis of these information and molecular modeling study we have proposed a possible pathway leading to one-electron oxidation at the thymidines.

Battery is the sole electrical energy source when electric vehicle(EV) is moving. To reduce traveling anxiety, an effective energy management system to indicate the state-of-charge (SOC) of the battery and make a balance between vehicle performance and endurance is very important. This research is aimed to develop a SOC estimation system with high accuracy. The proposed method in this thesis is based on under load voltage and multilevel Peukert's equation to estimate the SOC. The proposed method is compared with the open circuit voltage method for initial SOC estimation and with coulometric method for cumulative SOC estimation under various EV driving conditions simulated by an adjustable electronics load. Experimental results indicate that the proposed method can provide reasonable accuracy as compared with other tested methods for LiFePO4 battery SOC estimations.

The manganites of the type RMnO3 (R=La, Nd, Pr, Sm) are antiferromagnetic and the end (n= µ) members of the so-called Ruddlesden-Popper series, Rn+1MnnO3n+1. These oxide materials illustrate many interesting properties like colossal magnetoresistance (CMR)1-13, charge ordering (CO)14-21, magnetic field induced structural and ferromagnetic transitions22-24 when R is partially substituted by divalent cation A (=Ca, Sr, Ba, Pb) as R1-xAxMnO3. According our results of resistivity (r) and specific heat (C) on the Pr1-xCaxMnO3 series, we confirmed the Pr0.65Ca0.35MnO3 is the good choice to investigate the interplay of double exchange (DE) interaction and charge(CO)/orbital(OO) ordering. A systematic study of r, magnetization (M) and C on polycrystalline Pr0.65Ca0.35-xSrxMnO3 (x=0-0.35) perovskite manganites has been reported. The T-x phase diagram presenting their electrical and magnetic properties is prevailed. The Pr0.65Ca0.25Sr0.1MnO3 (for x=0.1) sample is particularly unique showing a CO transition at TCO ~ 200K, an antiferromagnetic (AFM) ordering transition at TN ~ 175K, a metal-insulator (MI) transition at TMI ~ 80K and a ferromagnetic (FM) ordering transition at TC ~ 45K in the absence of magnetic fields. However, the C data of it do not show any anomaly at TMI for MI transition but illustrates a much smaller anomaly than expected one at TC and is suppressed by magnetic fields. This may indicate that the FM ordering in it, commonly related to MI transition, is of meta-stable characteristic and is ascribed to electronic and magnetic instability induced by spin fluctuations. This is established from the T-H phase diagram, as well as the thermal and magnetic hysteresis in r, M and C.

Thèse de doctorat : Chimie : Strasbourg 1 : 2008. / Titre provenant de l'écran-titre. Bibliogr. p. 207-220.

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references.

The effect of pH on fiber and paper properties, during beating and sheet formation, was investigated for three different pulps. The pulps were pH adjusted to four different pH levels between 3 and 9. Isotropic laboratory sheet were made of both unbeaten and beaten pulps. The beaten neutral sulfite semi-chemical pulp and bleached softwood kraft pulp were affected by changes in pH; bleached softwood kraft pulp in a minor extent due to less fiber surface charges. Compared to the other pH levels, pH 3 showed a lower fiber surface charge, water retention value, tensile index, tensile stiffness index, compressive index and edge crush resistance index. SEM pictures showed a denser network at pH 9 than for pH 3. This was seen for both neutral sulphite semi-chemical and softwood kraft pulp. The unbeaten pulps and beaten bleached hardwood kraft pulp were not affected by changes in pH. SEM pictures showed no difference in the fiber network for bleached hardwood kraft pulp. A mill trial, with neutral sulphite semi-chemical pulp, at pH levels between pH 4.8 and pH 5.6 was completed. No significant difference was seen for any mechanical property.

Models of inner-shell vacancy production which include translation factors are developed for the change transfer process in ion-atom collisions. Translation factors are included in the basis set in which the electronic wavefunction is expanded in order to correctly describe the motion of the electron during the collision. Though several numerical studies have been done which employ this concept, the present models for change exchange are based on stationary state expansions. We first formulate the problem in the adiabatic framework. Having chosen a case in which the form of the translation factors is simple and in which additional approximations may be made, i.e., the case of long-range coupling, all terms in the equations of motion can be evaluated in closed form. An analytic solution is derived with the adiabatic theory which shows explicitly the effect of translation factors on the sharing ratio (defined as the ratio of vacancy production cross-sections of the high Z to low Z partners). The result reduces to that of the Demkov model in the low velocity limit. As the velocity increases, we predict a sharing ratio which drops below the Demkov curve and reaches a maximum at finite velocity. Numerical calculations using translation factors in a molecular orbital basis exhibit such a fall-off. We show that this effect is due solely to the inclusion of the momentum transfer of the electron. The assumptions of the adiabatic approach, however, limit its application to the low velocity region. We develop a new formulation of the problem which is not limited by the adiabatic assumptions. We obtain solutions of the equations of motion in closed form. This new treatment gives not only the correct adiabatic limit but also the exact Born result directly from the analytic solution of the coupled equations. Thus, translation factors are shown to provide a unification between an adiabatic Demkov-type approach and first-order perturbation theory at high velocity with a formalism which retains unitarity. In addition, it offers new insights onto the competing effects taking place in the collision process as a function of velocity and, within the approximations made, describes the intermediate velocity region which cannot be treated by either the adiabatic or high velocity, perturbation theories.

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