Ethical Approaches to Adolescent Participation in Sexual Health Research

In this paper we make the case for the importance of adolescent sexual health research, and argue that requiring parental consent for adolescent participation may (a) be unwarranted, (b) be inconsistent with the principles of justice and inclusiveness, (c) be confusing, and (d) serve to silence young people who most need to have a voice in sexual health research.MethodsThrough a case study of the Toronto Teen Survey, we offer concrete suggestions and alternatives for protecting adolescent health research participants in community-based settings and promoting ethical research approaches.ResultsStrategies suggested include: (1) adopting a community-based participatory research approach, (2) careful attention to youth-friendly protocols and consent procedures, (3) proper training of all research staff and peer researchers, (4) partnering with experienced community based youth-serving agencies, (5) paying maximum attention to issues of confidentiality and anonymity, and (6) valuing participation appropriately.ConclusionsInstitutional review boards and researchers should be encouraged to adopt localized context-dependent strategies that attend to the unique vulnerabilities of their particular study populations. Attention to flexibility, vulnerability, and community-specific needs is necessary to ensure appropriate ethical research practices that attend to the health and well-being of young people

An invitation to quantum tomography

We describe quantum tomography as an inverse statistical problem and show how entropy methods can be used to study the behaviour of sieved maximum likelihood estimators. There remain many open problems, and a main purpose of the paper is to bring these to the attention of the statistical community.Comment: 19 pages, submitted to J. Royal Stat. Soc. B. Note added 31/05/04: a revised version with further statistical results but less mathematical details, and with co-author Luis Artiles, has been posted on arXiv as math.ST/040559

Symmetric Hilbert spaces arising from species of structures

Symmetric Hilbert spaces such as the bosonic and the fermionic Fock spaces over some `one particle space' \K are formed by certain symmetrization procedures performed on the full Fock space. We investigate alternative ways of symmetrization by building on Joyal's notion of a combinatorial species. Any such species $F$ gives rise to an endofunctor \G_F of the category of Hilbert spaces with contractions mapping a Hilbert space \K to a symmetric Hilbert space \G_F(\K) with the same symmetry as the species $F$. A general framework for annihilation and creation operators on these spaces is developed, and compared to the generalised Brownian motions of R. Speicher and M. Bo\.zejko. As a corollary we find that the commutation relation $a_ia_j^*-a_j^*a_i=f(N)\delta_{ij}$ with $Na_i^*-a_i^*N=a_i^*$ admits a realization on a symmetric Hilbert space whenever $f$ has a power series with infinite radius of convergence and positive coefficients.Comment: 39 page

Generalised Brownian Motion and Second Quantisation

A new approach to the generalised Brownian motion introduced by M. Bozejko and R. Speicher is described, based on symmetry rather than deformation. The symmetrisation principle is provided by Joyal's notions of tensorial and combinatorial species. Any such species V gives rise to an endofunctor F_V of the category of Hilbert spaces with contractions. A generalised Brownian motion is an algebra of creation and annihilation operators acting on F_V(H) for arbitrary Hilbert spaces H and having a prescription for the calculation of vacuum expectations in terms of a function t on pair partitions. The positivity is encoded by a *-semigroup of "broken pair partitions" whose representation space with respect to t is V. The existence of the second quantisation as functor Gamma_t from Hilbert spaces to noncommutative probability spaces is proved to be equivalent to the multiplicative property of the function t. For a certain one parameter interpolation between the fermionic and the free Brownian motion it is shown that the ``field algebras'' Gamma(K) are type II_1 factors when K is infinite dimensional.Comment: 33 pages, 5 figure

Stochastic Schrodinger equations

A derivation of stochastic Schrodinger equations is given using quantum filtering theory. We study an open system in contact with its environment, the electromagnetic field. Continuous observation of the field yields information on the system: it is possible to keep track in real time of the best estimate of the system's quantum state given the observations made. This estimate satisfies a stochastic Schrodinger equation, which can be derived from the quantum stochastic differential equation for the interaction picture evolution of system and field together. Throughout the paper we focus on the basic example of resonance fluorescence.Comment: 24 page