Randomized Polypill Crossover Trial in People Aged 50 and Over

PMCID: PMC3399742This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

Learning Through Rich Environments

Research into games in education most frequently expresses itself in the form of noting that games interest and motivate, and that we might therefore find the learning process improved if we were to use games as a vehicle for the delivery of learning content. We do not wish to take this approach, but to analyse what it is that makes games interesting and motivating and apply this in the context of designing learning scenarios. Many papers propose taxonomies of game style and criteria for good game design, tending to list good ideas and observed issues, but meeting difficulties when trying to generalise. We review some of the more important contributions in the area, and distil these into models to help us understand what's involved by defining the concept of a “Rich Environment.” We conclude with an example of how these models may be applied to the design of a learning environment

ASR expansion behavior in reinforced concrete : experimentation and numerical modeling for practical application

Most practicing structural engineers are not well-equipped with the knowledge or tools necessary to adequately address the problem of alkali-silica reaction (ASR). While the mechanisms and consequences of ASR in plain, unloaded concrete are fairly well-understood, such a statement cannot be made about ASR-affected reinforced concrete (RC). Central to the problem is that the expansion behavior of ASR-affected RC behavior as influenced by restraint in the form of embedded reinforcing bars and sustained applied loads is unclear. It is these ASR-induced expansions in concrete that lead to cracking, possible strength and stiffness degradation of the material, and the introduction of unanticipated material stresses that may impair the durability, serviceability, functionality, and integrity of affected structures. In an effort to transition from a materials science perspective on ASR toward a practical structural engineering approach for addressing ASR in RC, experimental and analytical research was conducted with the goals of: 1) generating more insight into the mechanism of ASR expansion in RC and better assessing how a variety of structural details influence expansion behavior, 2) enlarging the database of information on ASR expansion behavior in RC within the literature, and 3) developing a new tool that could be used to reliably estimate life-cycle expansions for subsequent use in quantifying current and future load-carrying response of existing ASR-affected structures. Expansion monitoring studies were carried out at the Ferguson Structural Engineering Laboratory on a large-scale, biaxially reinforced concrete beam and large-scale, multi-axially reinforced concrete cubes affected by ASR. The multi-directional expansion behaviors of these elements were measured over time and with volumetric expansion development to evaluate the influences of different reinforcing schemes (e.g., amounts, directions, and layouts of reinforcement) on overall behavior. Using principles of mechanics, a new ASR expansion model, the Distributed Volumetric Expansion Pressure (DVEP) model, was developed to estimate the multi-directional distribution of volumetric expansions developing in RC structures. The DVEP model was designed as a non-incremental analysis tool accounting for constitutive relationships and utilizing simple, structural detailing inputs (e.g., reinforcement ratios and material properties) for rapid and accurate assessment of global RC expansion behavior by hand or within the framework of finite element analysis programs employing secant stiffness solution algorithms. The modeling approach was extensively validated and shown to be robust and capable of being implemented with limited subjective application. The results obtained from the numerical modeling of expansion behavior were used to preliminarily examine the consequences of expansion on RC load-deformation behavior. Finally, several recommendations for future work were provided.Civil, Architectural, and Environmental Engineerin

Reconciling the Evidence on Serum Homocysteine and Ischaemic Heart Disease: A Meta-Analysis

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Spatial and temporal distribution of slip for the 1992 Landers, California, earthquake

We have determined a source rupture model for the 1992 Landers earthquake (M_W 7.2) compatible with multiple data sets, spanning a frequency range from zero to 0.5 Hz. Geodetic survey displacements, near-field and regional strong motions, broadband teleseismic waveforms, and surface offset measurements have been used explicitly to constrain both the spatial and temporal slip variations along the model fault surface. Our fault parameterization involves a variable-slip, multiple-segment, finite-fault model which treats the diverse data sets in a self-consistent manner, allowing them to be inverted both independently and in unison. The high-quality data available for the Landers earthquake provide an unprecedented opportunity for direct comparison of rupture models determined from independent data sets that sample both a wide frequency range and a diverse spatial station orientation with respect to the earthquake slip and radiation pattern. In all models, consistent features include the following: (1) similar overall dislocation patterns and amplitudes with seismic moments of 7 to 8 × 10^(26) dyne-cm (seismic potency of 2.3 to 2.7 km^3); (2) very heterogeneous, unilateral strike slip distributed over a fault length of 65 km and over a width of at least 15 km, though slip is limited to shallower regions in some areas; (3) a total rupture duration of 24 sec and an average rupture velocity of 2.7 km/sec; and (4) substantial variations of slip with depth relative to measured surface offsets. The extended rupture length and duration of the Landers earthquake also allowed imaging of the propagating rupture front with better resolution than for those of prior shorter-duration, strike-slip events. Our imaging allows visualization of the rupture evolution, including local differences in slip durations and variations in rupture velocity. Rupture velocity decreases markedly at shallow depths, as well as near regions of slip transfer from one fault segment to the next, as rupture propagates northwestward along the multiply segmented fault length. The rupture front slows as it reaches the northern limit of the Johnson Valley/Landers faults where slip is transferred to the southern Homestead Valley fault; an abrupt acceleration is apparent following the transfer. This process is repeated, and is more pronounced, as slip is again passed from the northern Homestead Valley fault to the Emerson fault. Although the largest surface offsets were observed at the northern end of the rupture, our modeling indicates that substantial rupture was also relatively shallow (less than 10 km) in this region

Foreshocks and Aftershocks of the Great 1857 California Earthquake

The San Andreas fault is the longest fault in California and one of the longest strike-slip faults anywhere in the world, yet we know little about many aspects of its behavior before, during, and after large earthquakes. We conducted a study to locate and to estimate magnitudes for the largest foreshocks and aftershocks of the 1857 M 7.9 Fort Tejon earthquake on the central and southern segments of the fault. We began by searching archived first-hand accounts from 1857 through 1862, by grouping felt reports temporally, and by assigning modified Mercalli intensities to each site. We then used a modified form of the grid-search algorithm of Bakun and Wentworth, derived from empirical analysis of modern earthquakes, to find the location and magnitude most consistent with the assigned intensities for each of the largest events. The result confirms a conclusion of Sieh that at least two foreshocks (“dawn” and “sunrise”) located on or near the Parkfield segment of the San Andreas fault preceded the mainshock. We estimate their magnitudes to be M ≈ 6.1 and M ≈ 5.6, respectively. The aftershock rate was below average but within one standard deviation of the number of aftershocks expected based on statistics of modern southern California mainshock-aftershock sequences. The aftershocks included two significant events during the first eight days of the sequence, with magnitudes M ≈ 6.25 and M ≈ 6.7, near the southern half of the rupture; later aftershocks included a M ≈ 6 event near San Bernardino in December 1858 and a M ≈ 6.3 event near the Parkfield segment in April 1860. From earthquake logs at Fort Tejon, we conclude that the aftershock sequence lasted a minimum of 3.75 years

Slip distribution and tectonic implication of the 1999 Chi‐Chi, Taiwan, Earthquake

We report on the fault complexity of the large (M_w = 7.6) Chi‐Chi earthquake obtained by inverting densely and well‐distributed static measurements consisting of 119 GPS and 23 doubly integrated strong motion records. We show that the slip of the Chi-Chi earthquake was concentrated on the surface of a ”wedge shaped” block. The inferred geometric complexity explains the difference between the strike of the fault plane determined by long period seismic data and surface break observations. When combined with other geophysical and geological observations, the result provides a unique snapshot of tectonic deformation taking place in the form of very large (>10m) displacements of a massive wedge‐shaped crustal block which may relate to the changeover from over‐thrusting to subducting motion between the Philippine Sea and the Eurasian plates

Non-Stationary Dark Energy Around a Black Hole

Numerical simulations of the accretion of test scalar fields with non-standard kinetic terms (of the k-essence type) onto a Schwarzschild black hole are performed. We find a full dynamical solution for the spherical accretion of a Dirac-Born-Infeld type scalar field. The simulations show that the accretion eventually settles down to a well known stationary solution. This particular analytical steady state solution maintains two separate horizons. The standard horizon is for the usual particles propagating with the limiting speed of light, while the other sonic horizon is for the k-essence perturbations propagating with the speed of sound around this accreting background. For the case where the k-essence perturbations propagate superluminally, we show that one can send signals from within a black hole during the approach to the stationary solution. We also find that a ghost condensate model settles down to a stationary solution during the accretion process.Comment: 8 pages, 10 figure

The Internal Spin Angular Momentum of an Asymptotically Flat Spacetime

In this paper we investigate the manner in which the internal spin angular momentum of a spinor field is encoded in the gravitational field at asymptotic infinity. The inclusion of internal spin requires us to re-analyze our notion of asymptotic flatness. In particular, the Poincar\'{e} symmetry at asymptotic infinity must replaced by a spin-enlarged Poincar\'{e} symmetry. Likewise, the generators of the asymptotic symmetry group must be supplemented to account for the internal spin. In the Hamiltonian framework of first order Einstein-Cartan gravity, the extra generator comes from the boundary term of the Gauss constraint in the asymptotically flat context. With the additional term, we establish the relations among the Noether charges of a Dirac field, the Komar integral, and the asymptotic ADM-like geometric integral. We show that by imposing mild restraints on the generating functionals of gauge transformations at asymptotic infinity, the phase space is rendered explicitly finite. We construct the energy-momentum and the new total (spin+orbital) angular momentum boundary integrals that satisfy the appropriate algebra to be the generators of the spin-enlarged Poincar\'{e} symmetry. This demonstrates that the internal spin is encoded in the tetrad at asymptotic infinity. In addition, we find that a new conserved and (spin-enlarged) Poincar\'{e} invariant charge emerges that is associated with the global structure of a gauge transformation.Comment: V2: No major changes, journal reference adde