Quasi-static aberrations induced by laser guide stars in adaptive optics

Laser Guide Star Adaptive Optics (LGS AO) systems use the return from an artificial guide star to measure the wavefront aberrations in the direction of the science object. We observe quasi-static differences between the measured wavefront and the wavefront aberration of the science object. This paper quantifies and explains the source of the difference between the wavefronts measured using an LGS and a natural guide star at the W. M. Keck Observatory, which can be as high as 1000 nm RMS

Minimax Estimation of Nonregular Parameters and Discontinuity in Minimax Risk

When a parameter of interest is nondifferentiable in the probability, the existing theory of semiparametric efficient estimation is not applicable, as it does not have an influence function. Song (2014) recently developed a local asymptotic minimax estimation theory for a parameter that is a nondifferentiable transform of a regular parameter, where the nondifferentiable transform is a composite map of a continuous piecewise linear map with a single kink point and a translation-scale equivariant map. The contribution of this paper is two fold. First, this paper extends the local asymptotic minimax theory to nondifferentiable transforms that are a composite map of a Lipschitz continuous map having a finite set of nondifferentiability points and a translation-scale equivariant map. Second, this paper investigates the discontinuity of the local asymptotic minimax risk in the true probability and shows that the proposed estimator remains to be optimal even when the risk is locally robustified not only over the scores at the true probability, but also over the true probability itself. However, the local robustification does not resolve the issue of discontinuity in the local asymptotic minimax risk

Relativistic dynamical polarizability of hydrogen-like atoms

Using the operator representation of the Dirac Coulomb Green function the analytical method in perturbation theory is employed in obtaining solutions of the Dirac equation for a hydrogen-like atom in a time-dependent electric field. The relativistic dynamical polarizability of hydrogen-like atoms is calculated and analysed.Comment: 15 pages, 3 figures (not included, but hard copies are available upon request

Interpretive discourses in South Africa\'s Education White Paper No. 6: Special Needs Education

No Abstract. South African Journal of EducationVol. 23(2) 2003: pp. 152-15

Quantum sections and Gauge algebras

Using quantum sections of filtered rings and the associated Rees rings one can lift the scheme structure on Proj of the associated graded ring to the Proj of the Rees ring . The algebras of interest here are positively filtered rings having a non-commutative regular quadratic algebra for the associated graded ring ; these are the socalled gauge algebras obtaining their name from special examples appearing in E. Witten's gauge theories . The paper surveys basic definitions and properties but concentrates on the development of several concrete examples

Teaching respect: a philosophical analysis

According to a Zulu proverb a human being can only become truly human because of others. Each person can only become more human, more himself- regardless of his sex - through the co-involvement of others. It is the love for one’s neighbour and the respect one has for him/her as a person which makes one consider the other party's feelings, viewpoints and circumstances. In order to arrive at a situation of peaceful coexistence it is important to realize that human attitudes and a mature life style evolve through a process of learning and interaction with others. It is a timeconsuming and costly process which starts at infancy and continues throughout someone's life. Instruction concerning interpersonal relations and the teaching of respect cannot be confined to individual lessons or working sessions at home or in school. Discussions and conversations concerning interpersonal relations need to form an integral and natural part of a child’s life within the home environment and throughout the pupil's school career. It is senseless if educators talk about the importance of teaching respect only to reveal disrespectful behaviour themselves, or to talk about the importance of self-esteem in the paying of respect whilst causing children to feel negative about themselves. To be able to express respect to other human beings, one needs to be respected. A child needs to experience how it feels when homage is paid. The following rule of life applies in this regard: one can never give if one has never received respect

Coupling constants and transition potentials for hadronic decay modes of a meson

Within the independent-harmonic-oscillator model for quarks inside a hadron, a rigorous method is presented for the calculation of coupling constants and transition potentials for hadronic decay, as needed in a multi-channel description of mesons.Comment: 19 pages, 4 figure