Accurate theoretical fits to laser ARPES EDCs in the normal phase of cuprate superconductors

Anderson has recently proposed a theory of the strange metal state above Tc in the high Tc superconductors. [arXiv:cond-mat/0512471] It is based on the idea that the unusual transport properties and spectral functions are caused by the strong Mott- Hubbard interactions and can be computed by using the formal apparatus of Gutzwiller projection. In ref. 1 Anderson computed only the tunneling spectrum and the power-law exponent of the infrared conductivity. He had calculated the energy distribution curves (EDCs) in angle resolved photoemission spectroscopy (ARPES) but was discouraged when these differed radically from the best ARPES measurements available at the time, and did not include them. In this letter we compare the spectral functions computed within this model to the novel laser-ARPES data of the Dessau group.These are found to capture the shape of the experimental EDCs with unprecedented accuracy and in principle have only one free parameter

Evaluation of four gamma-based methods for calculating confidence intervals for age-adjusted mortality rates when data are sparse

Background Equal-tailed confidence intervals that maintain nominal coverage (0.95 or greater probability that a 95% confidence interval covers the true value) are useful in interval-based statistical reliability standards, because they remain conservative. For age-adjusted death rates, while the Fay–Feuer gamma method remains the gold standard, modifications have been proposed to streamline implementation and/or obtain more efficient intervals (shorter intervals that retain nominal coverage). Methods This paper evaluates three such modifications for use in interval-based statistical reliability standards, the Anderson–Rosenberg, Tiwari, and Fay–Kim intervals, when data are sparse and sample size-based standards alone are overly coarse. Initial simulations were anchored around small populations (P = 2400 or 1200), the median crude all-cause US mortality rate in 2010–2019 (833.8 per 100,000), and the corresponding age-specific probabilities of death. To allow for greater variation in the age-adjustment weights and age-specific probabilities, a second set of simulations draws those at random, while holding the mean number of deaths at 20 or 10. Finally, county-level mortality data by race/ethnicity from four causes are selected to capture even greater variation: all causes, external causes, congenital malformations, and Alzheimer disease. Results The three modifications had comparable performance when the number of deaths was large relative to the denominator and the age distribution was as in the standard population. However, for sparse county-level data by race/ethnicity for rarer causes of death, and for which the age distribution differed sharply from the standard population, coverage probability in all but the Fay–Feuer method sometimes fell below 0.95. More efficient intervals than the Fay–Feuer interval were identified under specific circumstances. When the coefficient of variation of the age-adjustment weights was below 0.5, the Anderson–Rosenberg and Tiwari intervals appeared to be more efficient, whereas when it was above 0.5, the Fay–Kim interval appeared to be more efficient. Conclusions As national and international agencies reassess prevailing data presentation standards to release age-adjusted estimates for smaller areas or population subgroups than previously presented, the Fay–Feuer interval can be used to develop interval-based statistical reliability standards with appropriate thresholds that are generally applicable. For data that meet certain statistical conditions, more efficient intervals could be considered

Theory of Structural Glasses and Supercooled Liquids

We review the Random First Order Transition Theory of the glass transition, emphasizing the experimental tests of the theory. Many distinct phenomena are quantitatively predicted or explained by the theory, both above and below the glass transition temperature $T_g$. These include: the viscosity catastrophe and heat capacity jump at $T_g$, and their connection; the non-exponentiality of relaxations and their correlation with the fragility; dynamic heterogeneity in supercooled liquids owing to the mosaic structure; deviations from the Vogel-Fulcher law, connected with strings or fractral cooperative rearrangements; deviations from the Stokes-Einstein relation close to $T_g$; aging, and its correlation with fragility; the excess density of states at cryogenic temperatures due to two level tunneling systems and the Boson Peak.Comment: submitted to Ann. Rev. Phys. Che

Numerical investigation of the flow over delta wing and reverse delta wing

Abstract This study aims to give some thoughts and initial understanding of passive wake vortex alleviation by introducing add-ons devices onto the aircraft, which are delta wing (DW) and reverse delta wing (RDW). However, as a preliminary investigation, the study has treated these devices separately from the aircraft in order to clearly visualize the wake vortex formation behind the wing as a standalone. Simulations were performed using RANS turbulence model. The results were obtained and quantified at measurement section locations downstream, of x/c=1.359 and x/c=3.418 measured from leading edge point of the model. Comparison between numerical and experimental results has shown good agreement in term of aerodynamic forces for RDW, whereas the comparison is not so good for DW as far as the prediction of drag coefficient is concerned. Although the simulations capture vortex roll-up trends, the size of the vortex is not predicted correctly by RANS turbulence model. Overall, it can be concluded from the results that the wake vortex generated from DW exhibit higher tangential velocity magnitude and circulation than the one generated from RDW at a particular angle of attack (AOA) between 20º to 30º

Wake structure and kinematics in two insectivorous bats

We compare kinematics and wake structure over a range of flight speeds (4.0–8.2 m s(−1)) for two bats that pursue insect prey aerially, Tadarida brasiliensis and Myotis velifer. Body mass and wingspan are similar in these species, but M. velifer has broader wings and lower wing loading. By using high-speed videography and particle image velocimetry of steady flight in a wind tunnel, we show that three-dimensional kinematics and wake structure are similar in the two species at the higher speeds studied, but differ at lower speeds. At lower speeds, the two species show significant differences in mean angle of attack, body–wingtip distance and sweep angle. The distinct body vortex seen at low speed in T. brasiliensis and other bats studied to date is considerably weaker or absent in M. velifer. We suggest that this could be influenced by morphology: (i) the narrower thorax in this species probably reduces the body-induced discontinuity in circulation between the two wings and (ii) the wing loading is lower, hence the lift coefficient required for weight support is lower. As a result, in M. velifer, there may be a decreased disruption in the lift generation between the body and the wing, and the strength of the characteristic root vortex is greatly diminished, both suggesting increased flight efficiency. This article is part of the themed issue ‘Moving in a moving medium: new perspectives on flight’

On the combination of high-pressure and low-pressure exhaust gas recirculation loops for improved fuel economy and reduced emissions in high-speed direct-injection engines

In this paper, an experimental study of the combination of low-pressure and high-pressure exhaust gas recirculation architectures has been carried out. In the first part of the paper, the effects of both high-pressure and low-pressure exhaust gas recirculation architectures on engine behaviour and performance are analysed by means of a series of steady tests. In the second part, the effects of the combination of both architectures are addressed. The results show that the low-pressure configuration improves high-pressure exhaust gas recirculation results in brake-specific fuel consumption, nitrogen oxides and exhaust gas opacity; nevertheless, hydrocarbon emissions are increased, especially during the engine warm up. In addition, the exhaust gas recirculation rate achieved with low-pressure systems is limited by the pressure difference between diesel particulate matter outlet and compressor inlet; therefore, the high-pressure system can be used to achieve the required exhaust gas recirculation levels without increasing pumping losses. In this sense, the combination of both exhaust gas recirculation layouts offers significant advantages to reduce emissions and fuel consumption to meet future emission requirements.This work was supported by the Ministry of Science and Innovation (Spanish Government) [grant number IPT-370000-2010-022].Desantes Fernández, JM.; Luján, JM.; Plá Moreno, B.; Soler Muniesa, JA. (2013). On the combination of high-pressure and low-pressure exhaust gas recirculation loops for improved fuel economy and reduced emissions in high-speed direct-injection engines. International Journal of Engine Research. 14(1):3-11. https://doi.org/10.1177/1468087412437623S311141Taylor, A. M. K. P. (2008). Science review of internal combustion engines. Energy Policy, 36(12), 4657-4667. doi:10.1016/j.enpol.2008.09.001Lü, X.-C., Chen, W., & Huang, Z. (2005). A fundamental study on the control of the HCCI combustion and emissions by fuel design concept combined with controllable EGR. Part 2. Effect of operating conditions and EGR on HCCI combustion. Fuel, 84(9), 1084-1092. doi:10.1016/j.fuel.2004.12.015Nakano, M., Mandokoro, Y., Kubo, S., & Yamazaki, S. (2000). Effects of exhaust gas recirculation in homogeneous charge compression ignition engines. International Journal of Engine Research, 1(3), 269-279. doi:10.1243/1468087001545173Zheng, M., Reader, G. T., & Hawley, J. G. (2004). Diesel engine exhaust gas recirculation––a review on advanced and novel concepts. Energy Conversion and Management, 45(6), 883-900. doi:10.1016/s0196-8904(03)00194-8Hountalas, D. T., Mavropoulos, G. C., & Binder, K. B. (2008). Effect of exhaust gas recirculation (EGR) temperature for various EGR rates on heavy duty DI diesel engine performance and emissions. Energy, 33(2), 272-283. doi:10.1016/j.energy.2007.07.002Luján, J. M., Galindo, J., Serrano, J. R., & Pla, B. (2008). A methodology to identify the intake charge cylinder-to-cylinder distribution in turbocharged direct injection Diesel engines. Measurement Science and Technology, 19(6), 065401. doi:10.1088/0957-0233/19/6/065401Ladommatos, N., Abdelhalim, S., & Zhao, H. (2000). The effects of exhaust gas recirculation on diesel combustion and emissions. International Journal of Engine Research, 1(1), 107-126. doi:10.1243/1468087001545290Maiboom, A., Tauzia, X., & Hétet, J.-F. (2008). Influence of high rates of supplemental cooled EGR on NOxand PM emissions of an automotive HSDI diesel engine using an LP EGR loop. International Journal of Energy Research, 32(15), 1383-1398. doi:10.1002/er.1455Gautier, P., Albrecht, A., Chasse, A., Moulin, P., Pagot, A., Fontvieille, L., & Issartel, D. (2009). A Simulation Study of the Impact of LP EGR on a Two-Stage Turbocharged Diesel Engine. Oil & Gas Science and Technology - Revue de l’IFP, 64(3), 361-379. doi:10.2516/ogst/2009019Torregrosa, A. J., Olmeda, P., Martín, J., & Degraeuwe, B. (2006). Experiments on the influence of inlet charge and coolant temperature on performance and emissions of a DI Diesel engine. Experimental Thermal and Fluid Science, 30(7), 633-641. doi:10.1016/j.expthermflusci.2006.01.00

Spatial assessment of intertidal seagrass meadows using optical imaging systems and a lightweight drone

Seagrass ecosystems are highly sensitive to environmental change. They are also in global decline and under threat from a variety of anthropogenic factors. There is now an urgency to establish robust monitoring methodologies so that changes in seagrass abundance and distribution in these sensitive coastal environments can be understood. Typical monitoring approaches have included remote sensing from satellites and airborne platforms, ground based ecological surveys and snorkel/scuba surveys. These techniques can suffer from temporal and spatial inconsistency, or are very localised making it hard to assess seagrass meadows in a structured manner. Here we present a novel technique using a lightweight (sub 7 kg) drone and consumer grade cameras to produce very high spatial resolution (∼4 mm pixel−1) mosaics of two intertidal sites in Wales, UK. We present a full data collection methodology followed by a selection of classification techniques to produce coverage estimates at each site. We trialled three classification approaches of varying complexity to investigate and illustrate the differing performance and capabilities of each. Our results show that unsupervised classifications perform better than object-based methods in classifying seagrass cover. We also found that the more sparsely vegetated of the two meadows studied was more accurately classified - it had lower root mean squared deviation (RMSD) between observed and classified coverage (9–9.5%) compared to a more densely vegetated meadow (RMSD 16–22%). Furthermore, we examine the potential to detect other biotic features, finding that lugworm mounds can be detected visually at coarser resolutions such as 43 mm pixel−1, whereas smaller features such as cockle shells within seagrass require finer grained data (<17 mm pixel−1)