All cases of endometrial cancer occurring among the residents of an affluent retirement community were compared with controls chosen from a roster of all women in the same community. Evidence of estrogen and other drug use and of selected medical conditions was obtained from three sources: medical records of the principal care facility, interviews, and the records of the local pharmacy. The risk ratio for any estrogen use was estimated from all available evidence to be 8.0 (95 per cent confidence interval, 3.5 to 18.1). and the for conjugated estrogen use to be 5.6 (95 per cent confidence interval, 2.8 to 11.1). Increased risk from estrogens was shown for invasive as well as noninvasive cancer, and a dose-response effect was demonstrated. For an estrogen user, the risk from endometrial cancer appeared to exceed by far the base-line risk from any other single cancer.

Characterizing structural and phase transformations of water at the molecular level is key to understanding a variety of multiphase processes ranging from ice nucleation in the atmosphere to hydration of biomolecules and wetting of solid surfaces. In this study, state-of-the-art quantum simulations with a many-body water potential energy surface, which exhibits chemical and spectroscopic accuracy, are carried out to monitor the microscopic melting of the water hexamer through the analysis of vibrational spectra and appropriate structural order parameters as a function of temperature. The water hexamer is specifically chosen as a case study due to the central role of this cluster in the molecular-level understanding of hydrogen bonding in water. Besides being in agreement with the experimental data available for selected isomers at very low temperature, the present results provide quantitative insights into the interplay between energetic, entropic, and nuclear quantum effects on the evolution of water clusters from "solid-like" to "liquid-like" structures. This study thus demonstrates that computer simulations can now bridge the gap between measurements currently possible for individual isomers at very low temperature and observations of isomer mixtures at ambient conditions.

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The self-consistent phonons (SCP) method provides a consistent way to include anharmonic effects when treating a many-body quantum system at thermal equilibrium. The system is then described by an effective temperature-dependent harmonic Hamiltonian, which can be used to estimate the system's properties, such as its free energy or its vibrational spectrum. The numerical bottleneck of the method is the evaluation of Gaussian averages of the potential energy and its derivatives. Several algorithmic ideas/tricks are introduced to reduce the cost of such integration by orders of magnitude, e.g., relative to that of the previous implementation of the SCP approach by Calvo et al. [J. Chem. Phys. 133, 074303 (2010)]. One such algorithmic improvement is the replacement of standard Monte Carlo integration by quasi-Monte Carlo integration utilizing low-discrepancy sequences. The performance of the method is demonstrated on the calculation of vibrational frequencies of pyrene. It is then applied to compute the free energies of five isomers of water hexamer using the WHBB potential of Bowman and co-workers [J. Chem. Phys. 134, 094509 (2011)]. The present results predict the hexamer prism being thermodynamically most stable, with the free energy of the hexamer cage being about 0.2 kcal mol(-1) higher at all temperatures below T = 200 K.