Measuring the societal value of lifetime health

This paper considers two societal concerns in addition to health maximisation: first, concerns for the societal value of lifetime health for an individual; and second, concerns for the value of lifetime health across individuals. Health-related social welfare functions (HRSWFs) have addressed only the second concern. We propose a model that expresses the former in a metric – the adult healthy-year equivalent (AHYE) – that can be incorporated into standard HRSWFs. An empirical study based on this formulation shows that both factors matter: health losses in childhood are weighted more heavily than losses in adulthood and respondents wish to reduce inequalities in AHYEs

Measuring the societal value of lifetime health

This paper considers two societal concerns in addition to health maximisation: first, concerns for the societal value of lifetime health for an individual; and second, concerns for the value of lifetime health across individuals. Health-related social welfare functions (HRSWFs) have addressed only the second concern. We propose a model that expresses the former in a metric – the adult healthy-year equivalent (AHYE) – that can be incorporated into standard HRSWFs. An empirical study based on this formulation shows that both factors matter: health losses in childhood are weighted more heavily than losses in adulthood and respondents wish to reduce inequalities in AHYEs

Competition between Pauli and orbital effects in a charge-density wave system

We present angular dependent magneto-transport and magnetization measurements on alpha-(ET)2MHg(SCN)4 compounds at high magnetic fields and low temperatures. We find that the low temperature ground state undergoes two subsequent field-induced density-wave type phase transitions above a critical angle of the magnetic field with respect to the crystallographic axes. This new phase diagram may be qualitatively described assuming a charge density wave ground state which undergoes field-induced transitions due to the interplay of Pauli and orbital effects.Comment: 11 pages, 4 figures, shown at the APS march meeting 2000, appears in the Ph.D. thesis of J. S. Qualls (Florida State University, 1999), and submitted to PR

Will systems biology offer new holistic paradigms to life sciences?

A biological system, like any complex system, blends stochastic and deterministic features, displaying properties of both. In a certain sense, this blend is exactly what we perceive as the “essence of complexity” given we tend to consider as non-complex both an ideal gas (fully stochastic and understandable at the statistical level in the thermodynamic limit of a huge number of particles) and a frictionless pendulum (fully deterministic relative to its motion). In this commentary we make the statement that systems biology will have a relevant impact on nowadays biology if (and only if) will be able to capture the essential character of this blend that in our opinion is the generation of globally ordered collective modes supported by locally stochastic atomisms

Collective Dynamics of Gene Expression in Cell Populations

The phenotypic state of the cell is commonly thought to be determined by the set of expressed genes. However, given the apparent complexity of genetic networks, it remains open what processes stabilize a particular phenotypic state. Moreover, it is not clear how unique is the mapping between the vector of expressed genes and the cell's phenotypic state. To gain insight on these issues, we study here the expression dynamics of metabolically essential genes in twin cell populations. We show that two yeast cell populations derived from a single steady-state mother population and exhibiting a similar growth phenotype in response to an environmental challenge, displayed diverse expression patterns of essential genes. The observed diversity in the mean expression between populations could not result from stochastic cell-to-cell variability, which would be averaged out in our large cell populations. Remarkably, within a population, sets of expressed genes exhibited coherent dynamics over many generations. Thus, the emerging gene expression patterns resulted from collective population dynamics. It suggests that in a wide range of biological contexts, gene expression reflects a self-organization process coupled to population-environment dynamics

GENE EXPRESSION WAVES: CELL CYCLE INDEPENDENT COLLECTIVE DYNAMICS IN CULTURED CELLS

The ergodic hypothesis, which assumes the independence of each cell of the ensemble from all the others, is a necessary prerequisite to attach single cell based explanations to the grand averages taken from population data. This was the prevailing view about the interpretation of cellular biology experiments that typically are performed on colonies of billions of cells. By analysing gene expression data of different cells going from yeast to mammalian cell cultures, we demonstrate that cell cultures display a sort of ‘ecology-in-a-plate’ giving rise to a rich dynamics of gene expression that are independent from reproductive cycles, hence contradicting simple ergodic assumptions The aspecific character of the observed coordinated gene expression activity inhibits any simple mechanistic hypothesis and highlights the need to consider population effects in the interpretation of data coming from cell cultures