Uncertainty relation for the discrete Fourier transform.

We derive an uncertainty relation for two unitary operators which obey a commutation relation of the form UV=e(i phi) VU. Its most important application is to constrain how much a quantum state can be localized simultaneously in two mutually unbiased bases related by a discrete fourier transform. It provides an uncertainty relation which smoothly interpolates between the well-known cases of the Pauli operators in two dimensions and the continuous variables position and momentum.

Spacelike Singularities and Hidden Symmetries of Gravity.

We review the intimate connection between (super-)gravity close to a spacelike singularity (the "BKL-limit") and the theory of Lorentzian Kac-Moody algebras. We show that in this limit the gravitational theory can be reformulated in terms of billiard motion in a region of hyperbolic space, revealing that the dynamics is completely determined by a (possibly infinite) sequence of reflections, which are elements of a Lorentzian Coxeter group. Such Coxeter groups are the Weyl groups of infinite-dimensional Kac-Moody algebras, suggesting that these algebras yield symmetries of gravitational theories.

Informed consent and home birth.

The history and purpose of informed consent are explored and its legal components are detailed. Recommendations are given to meet the criteria for informed decision-making at home, including discussion of unusual circumstances. The nature of assistance at childbirth, especially at home, is explored in relation to legal obligations.

The transition from lay midwife to certified nurse-midwife in the United States.

This paper presents the results of a survey that was conducted between November 1992 and March 1993. Its target group consisted of midwives in the United States who began their careers as lay midwives and later decided to become certified nurse-midwives (CNMs). Questions address their demographic and socioeconomic characteristics to compile a profile that can be compared with other midwife populations.