New type of antiferromagnetic polaron and bipolaron in HTc - superconductors

The possibility of formation of a new type of polaron based on the quantum aniferromagnet (AF) model is reported. We take into account exchange interactions between localized d-d spins of the AF, as well as the p-d interaction of the AF with p-carriers. The energy minimum is found when maximum charge density occurs on every second spin. The formation of such ``comb''-like polarons results from the damping of quantum fluctuations and the appearance of Van Vleck-like staggered magnetization. Such polarons tend to form pairs coupled by an AF ``glue''.Comment: 3 pages 2 figure

Spin resonance of 2D electrons in a large-area silicon MOSFET

We report electron spin resonance (ESR) measurements on a large-area silicon MOSFET. An ESR signal at g-factor 1.9999(1), and with a linewidth of 0.6 G, is observed and found to arise from two-dimensional (2D) electrons at the Si/SiO2 interface. The signal and its intensity show a pronounced dependence on applied gate voltage. At gate voltages below the threshold of the MOSFET, the signal is from weakly confined, isolated electrons as evidenced by the Curie-like temperature dependence of its intensity. The situation above threshold appears more complicated. These large-area MOSFETs provide the capability to controllably tune from insulating to conducting regimes by adjusting the gate voltage while monitoring the state of the 2D electron spins spectroscopically.Comment: 7 pages, 3 figures, submitted to Physica E special edition for EPS2DS-1

The Feminine Other: A Study of the Women in Shakespeare\u27s Major Tragedies

The central examination of this thesis concentrates on the essential contributions of the female characters in Shakespeare\u27s major tragedies--Hamlet, Othello, King Lear, and Macbeth. Without the women\u27s conflict with the patriarchal order, the males would be unable to recognize and combat the corrupt elements in their society. The awareness of the female characters allows them to perceive the tainted patriarchal atmosphere they dwell in and operate within it as best as they can. In short, each woman\u27s individual field of awareness allows her to act as the executor of the dénoucement in the tragedy. Even those women with limited or inconsistent awareness of their realities play a significant part in exposing the contaminated deeds of the guilty. While Gertrude and Ophelia may not always be aware of the dire circumstances that surround them, both shift the balance of power from Claudius\u27s hands to Hamlet\u27s. The sacrifices of both women provide Hamlet with the opportunity to punish Claudius for his crimes. In a similar fashion, the inconsistent perceptions of Desdemona and Emilia provide Othello with the means to uncover Iago\u27s malicious nature. In standing up for one another, the women lose their lives; however, their atonement paves the way for Iago\u27s punishment. With a greater field of awareness, the women of King Lear and Macbeth contribute to the downfall of the corruption in the patriarchy. Cordelia and Lady Macduff directly confront the patriarchal neglect of the feminine Other, while Goneril, Regan, and Lady Macbeth reflect the need for women to sacrifice their femininity in order to wield authority in their lives. Even though these alert females die as a result of their stances, their actions create the necessary elements for the dénoucement in the tragedies to occur. Although the main female characters die in Shakespeare\u27s major tragedies, their deaths do not make them any less important than their male counterparts. Besides allowing the male protagonists to fulfill their roles to the greatest degree possible, the women deserve major attention because they challenge the patriarchal restraints imposed on their existence. In attempting to defy a world that supplies little chance for advancement, the female characters of the major tragedies generate hope for women that did not exist previously

Spin-Hall effect in semiconductor heterostructures with cubic Rashba spin-orbit interaction

We study the spin-Hall effect in systems with weak cubic Rashba spin-orbit interaction. To this end we derive particle and spin diffusion equations and explicit expressions for the spin-current tensor in the diffusive regime. We discuss the impact of electric fields on the Green's functions and the diffusion equations and establish a relationship between the spin-current tensor and the spin diffusion equations for the model under scrutiny. We use our results to calculate the edge spin-accumulation in a spin-Hall experiment and show that there is also a new Hall-like contribution to the electric current in such systems.Comment: 14 page

Chemical diversity of talcs in relation to their origin

Apart from main constituents, chemical compositions of talc show various elements, such as Fe, Al, Cr, Ni, Mn , alkalies and fluorine. Several analyses of talcs from Egypt (El-Sharkawy 2000) show the rectilinear negative correlation of Si and Fe 3+ suggesting simultaneous substitution of Fe 3 ' both in tetrahedra and in octahedra according to the mechanism MgSiSi. Much weaker correlation shows octahedral Al (R2 =0.50). Sodium content shows positive correlation both with temperature and pressure of talc crystallization. It is likely that high PT-conditions favour incorporating Na into the talc structure

Security Assessment Using Neural Computing

The advantage of fast computation capability of an artificial neural network (ANN) is used to introduce an iterative scheme for security assessment of power systems. Two related approaches are shown which demonstratedly work satisfactorily. The idea of feedback in a single-layer feedforward neural network is experimented yielding higher accuracy. The ANN is trained by using a set of data obtained from off-line analysis of the power network. After training, an approximate solution for a given condition may be found almost immediately. The approximate solution obtained is judged adequate for assessing the security of the power system. A case study is also presented for demonstrating the applicability of the approach