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.
Static stretching (SS) has been used for inducing acute and long-term increases in range of motion (ROM). Foam rolling (FR) has recently gained popularity for acutely increasing ROM. However, the long-term effects of FR on ROM have not been thoroughly evaluated. Therefore, the purpose of this study was to investigate the acute and long-term changes in dorsiflexion ROM as a result of 6 wk of FR, SS, and FR followed by SS (FR + SS). Methods Participants (n = 44) were randomly assigned to FR, SS, and FR + SS groups. The FR group foam rolled the triceps surae. The SS group performed a wall stretch for both legs. The FR + SS group performed FR immediately followed by SS. All groups completed 12 training sessions in 6 wk. Dorsiflexion ROM was assessed before and after the first training session, before the second session of week 3, before and after the last session in week 6, and at week 7. Results There was a 4.0% acute increase in ROM at week 6 (P = 0.004) for all three groups. ROM increased 8.4% from week 3 to week 7 for all three groups (P < 0.001). When comparing week 1 baseline to week 7, ROM increased 18.3% for all three groups (P = 0.003). Conclusion SS and FR seem to be comparable in terms of increasing dorsiflexion ROM acutely as well as after 6 wk of training for healthy, university-age participants. FR combined with SS does not seem to provide a synergistic effect on improving dorsiflexion ROM.
The diffusion Monte Carlo (DMC) method is applied to the water monomer, dimer, and hexamer using q-TIP4P/F, one of the most simple empirical water models with flexible monomers. The bias in the time step (Δτ) and population size (Nw) is investigated. For the binding energies, the bias in Δτ cancels nearly completely, whereas a noticeable bias in Nw remains. However, for the isotope shift (e.g, in the dimer binding energies between (H2O)2 and (D2O)2), the systematic errors in Nw do cancel. Consequently, very accurate results for the latter (within ∼0.01 kcal/mol) are obtained with moderate numerical effort (Nw ∼ 10(3)). For the water hexamer and its (D2O)6 isotopomer, the DMC results as a function of Nw are examined for the cage and prism isomers. For a given isomer, the issue of the walker population leaking out of the corresponding basin of attraction is addressed by using appropriate geometric constraints. The population size bias for the hexamer is more severe, and to maintain accuracy similar to that of the dimer, Nw must be increased by ∼2 orders of magnitude. Fortunately, when the energy difference between the cage and prism is taken, the biases cancel, thereby reducing the systematic errors to within ∼0.01 kcal/mol when using a population of Nw = 4.8 × 10(5) walkers. Consequently, a very accurate result for the isotope shift is also obtained. Notably, both the quantum and isotope effects for the prism-cage energy difference are small.
A novel resonant ultrasound technique is used to measure all elastic constants and their temperature dependence in single-crystal Lai 86Sro 14CUO4. The in-plane shear modulus C66 drops by nearly half upon cooling to 227 K, an effect attributed to order-parameter fluctuations (of 2D Gaussian character) near the tetragonal-orthorhombic phase boundary. Implications for current models of the structural phase transition are discussed, as well as the effect of domains in the low-temperature orthorhombic state.PACS numbers: 74.70.Vy, 43.35.+d, 62.65.+k The rich assortment of phases found in La2-*M X -CUO4 includes superconducting, magnetic, and structurally distorted materials. The relation between magnetic and superconducting phases is a critical issue that continues to attract attention. 1 A relation between the tetragonal-orthorhombic (TO) structural phase transition (SPT) and high-7 c superconductivity seemed less compelling until the recent work by Axe et al. 2 showed that a rearrangement of the structural distortion can destroy superconductivity. Here we report a surprisingly large elastic anomaly at the same SPT.Studies on polycrystals 3,4 indicate that all the elastic moduli and their temperature dependences are important for modeling both the superconducting transition at T c and the SPT at T JO in La 2 Cu0 4 . Bhattacharya et al. 4 found a break in slope of the shear-wave speed at T c in sintered powders of Lai.ssSro.isCuO^ Complicating the issue was the observation of similar behavior 5 at the same temperature in nonsuperconducting single-crystal La2CuC>4 and features in the thermal expansion of nonsuperconducting polycrystal. 6 At higher temperatures, both shear and longitudinal velocities of the sintered superconductor exhibited an extremely large softening 7 (-15% near 200 K), in contrast to the weak temperature dependence of the insulator. This unusual softening could not be attributed unambiguously to the development of the tetragonal-orthorhombic SPT. 8 This Letter resolves some of these issues by reporting high-resolution measurements of all c /y in a single-crystal sample of Lai.86Sro.uCu04. The measurements cover the temperature range 220-300 K, including 7>o (about 220 K in our sample). The most interesting feature observed is the monotonic and strong decrease of c^. At 227 K, c^ has less than 60% of its room-temperature value, while the other c,/s show only small changes (C44 increases less than 0.8% over the same temperature range). We will show that the unusual elastic behavior can be understood from a Landau theory of the SPT.The sample was prepared from a Cu-O flux using a traveling solvent floating-zone technique. 9 The crystal was aligned along the principal axes of the tetragonal cell and polished so the faces were parallel to within 1°, leaving a finished sample with dimensions 2.890x2.816 x2.405 mm 3 all ±0.01 mm, the shortest dimension corresponding to the tetragonal c axis. The density was measured to be 6.882 g/cm 3 , consistent with the nominal strontium concentration. Although we...
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