Sex, lies and self-reported counts: Bayesian mixture models for heaping in longitudinal count data via birth-death processes

Surveys often ask respondents to report nonnegative counts, but respondents may misremember or round to a nearby multiple of 5 or 10. This phenomenon is called heaping, and the error inherent in heaped self-reported numbers can bias estimation. Heaped data may be collected cross-sectionally or longitudinally and there may be covariates that complicate the inferential task. Heaping is a well-known issue in many survey settings, and inference for heaped data is an important statistical problem. We propose a novel reporting distribution whose underlying parameters are readily interpretable as rates of misremembering and rounding. The process accommodates a variety of heaping grids and allows for quasi-heaping to values nearly but not equal to heaping multiples. We present a Bayesian hierarchical model for longitudinal samples with covariates to infer both the unobserved true distribution of counts and the parameters that control the heaping process. Finally, we apply our methods to longitudinal self-reported counts of sex partners in a study of high-risk behavior in HIV-positive youth.Comment: Published at http://dx.doi.org/10.1214/15-AOAS809 in the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

High-Temperature Shape Memory Polymers

physical conformation changes when exposed to an external stimulus, such as a change in temperature. Such materials have a permanent shape, but can be reshaped above a critical temperature and fixed into a temporary shape when cooled under stress to below the critical temperature. When reheated above the critical temperature (Tc, also sometimes called the triggering or switching temperature), the materials revert to the permanent shape. The current innovation involves a chemically treated (sulfonated, carboxylated, phosphonated, or other polar function group), high-temperature, semicrystalline thermoplastic poly(ether ether ketone) (Tg .140 C, Tm = 340 C) mix containing organometallic complexes (Zn++, Li+, or other metal, ammonium, or phosphonium salts), or high-temperature ionic liquids (e.g. hexafluorosilicate salt with 1-propyl-3- methyl imidazolium, Tm = 210 C) to form a network where dipolar or ionic interactions between the polymer and the low-molecular-weight or inorganic compound forms a complex that provides a physical crosslink. Hereafter, these compounds will be referred to as "additives". The polymer is semicrystalline, and the high-melt-point crystals provide a temporary crosslink that acts as a permanent crosslink just so long as the melting temperature is not exceeded. In this example case, the melting point is .340 C, and the shape memory critical temperature is between 150 and 250 C. PEEK is an engineering thermoplastic with a high Young fs modulus, nominally 3.6 GPa. An important aspect of the invention is the control of the PEEK functionalization (in this example, the sulfonation degree), and the thermal properties (i.e. melting point) of the additive, which determines the switching temperature. Because the compound is thermoplastic, it can be formed into the "permanent" shape by conventional plastics processing operations. In addition, the compound may be covalently cross - linked after forming the permanent shape by S-PEEK by applying ionizing radiation ( radiation, neutrons), or by chemical crosslinking to form a covalent permanent network. With respect to other shape memory polymers, this invention is novel in that it describes the use of a thermoplastic composition that can be thermally molded or solution-cast into complex "permanent" shapes, and then reheated or redissolved and recast from solution to prepare another shape. It is also unique in that the shape memory behavior is provided by a non-polymer additive

Shale oil : potential economies of large-scale production, preliminary phase

Producing shale oil on a large scale is one of the possible alternatives for reducing dependence of the United States on imported petroleum. Industry is not producing shale oil on a commercial scale now because costs are too high even though industry dissatisfaction is most frequently expressed about "non-economic" barriers: innumerable permits, changing environmental regulations, lease limitations, water rights conflicts, legal challenges, and so on. The overall purpose of this study is to estimate whether improved technology might significantly reduce unit costs for production of shale oil in a planned large-scale industry as contrasted to the case usually contemplated: a small industry evolving slowly on a project-by-project basis. In this preliminary phase of the study, we collected published data on the costs of present shale oil technology and adjusted them to common conditions; these data were assembled to help identify the best targets for cost reduction through improved large-scale technology They show that the total cost of producing upgraded shale oil (i.e. shale oil accpetable as a feed to a petroleum refinery) by surface retorting ranges from about $18 to$28/barrel in late '78 dollars with a 20% chance that the costs would be lower than and 20% higher than that range. The probability distribution reflects our assumptions about ranges of shale richness, process performance, rate of return, and other factors that seem likely in a total industry portfolio of projects. About 40% of the total median cost is attributable to retorting, 20% to upgrading, and the remaining 40% to resource acquisition, mining, crushing, and spent shale disposal and revegetation. Capital charges account for about 70% of the median total cost and operating costs for the other 30%. There is a reasonable chance that modified in-situ processes (like Occidental's) may be able to produce shale oil more cheaply than surface retorting, but no reliable cost data have been published; in 1978, DOE estimated a saving of roughly $5/B for in-situ. Because the total costs of shale oil are spread over many steps in the production process, improvements in most or all of those steps are required if we seek a significant reduction in total cost. A June 1979 workshop of industry experts was held to help us identify possible cost-reduction technologies. Examples of the improved large-scale technologies proposed (for further evaluation) to the workshop were: - Instead of hydrotreating raw shale oil to make syncrude capable of being refined conventionally, rebalance all of a refinery's processes (or develop new catalysts/processes less sensitive to feed nitrogen) to accommodate shale oil feed -- a change analogous to a shift from sweet crude to sour crude. - Instead of refining at or near the retort site, use heated pipelines to move raw shale oil to existing major refining areas. - Instead of operating individual mines, open-pit mine all or much of the Piceance Creek Basin. - Instead of building individual retorts, develop new methods for mass production of hundreds of retorts

Numerical simulation of long wave runup for breaking and nonbreaking waves

Tsunamis produce a wealth of quantitative data that can be used to improve tsunami hazard awareness and to increase the preparedness of the population at risk. These data also allow for a performance evaluation of the coastal infrastructure and observations of sediment transport, erosion, and deposition. The interaction of the tsunami with coastal infrastructures and with the movable sediment bed is a three-dimensional process. Therefore, for runup and inundation prediction, three-dimensional numerical models must be employed. In this study, we have employed Smoothed Particle Hydrodynamics (SPH) to simulate tsunami runup on idealized geometries for the validation and exploration of three-dimensional flow structures in tsunamis. We make use of the canonical experiments for long-wave runup for breaking and nonbreaking waves. The results of our study prove that SPH is able to reproduce the runup of long waves for different initial and geometric conditions. We have also investigated the applicability and the effectiveness of different viscous terms that are available in the SPH literature. Additionally, a new breaking criterion based on numerical experiments is introduced, and its similarities and differences with existing criteria are discussed

Synthesis and Characterization of a Phosphonated Graft Copolyimide

A new synthesis route of phosphonated multiblock, branched copolyimide is proposed in this research. The synthesis and characterization of the series of new phosphonated graft copolyimides were prepared by combination of one-step high temperature polymerization and phosphonation method by lithiation and reaction with excess diethylchlorophosphate. The phosphonate ester product was converted to the phosphonic acid by hydrolysis. A branched polyimide structure was achieved by coupling the two polyimides with 3, 3'-diaminobenzidine. A phosphonated branched copolyimide with 32% mol phosphonation exhibited high thermal stability, with a decomposition temperature in nitrogen of ∼475°C. Proton exchange membranes prepared from these copolyimides had proton conductivity of 0.02 - 0.03 S/cm at 100% humidity over a temperature range of 40 - 100°C

Quantum Friction in Nanomechanical Oscillators at Millikelvin Temperatures

We report low-temperature measurements of dissipation in megahertz-range, suspended, single-crystal nanomechanical oscillators. At millikelvin temperatures, both dissipation (inverse quality factor) and shift in the resonance frequency display reproducible features, similar to those observed in sound attenuation experiments in disordered glasses and consistent with measurements in larger micromechanical oscillators fabricated from single-crystal silicon. Dissipation in our single-crystal nanomechanical structures is dominated by internal quantum friction due to an estimated number of roughly 50 two-level systems, which represent both dangling bonds on the surface and bulk defects.Comment: 5 pages, two-column format. Related papers available at http://nano.bu.ed