Dissolution influences on gypsum rock under short and long-term loading: Implications for dams

Dissolution of soluble substrates such as gypsum presents a major hazard to dams in many parts of the world. This research simulates hypothesised conditions beneath the Mosul Dam, northwest Iraq, where collapse of a karstic system associated with continuous fresh water supply from its reservoir is a recognised problem. Gypsum rocks from northern Iraq and similar rocks from Bantycock gypsum mine, UK, were analysed for short-term mechanical response following immersion (5 to 50 weeks) and long-term loading during immersion (maximum 50 weeks). New experimental devices were developed from a conventional oedometer. Cylinder samples provided a proxy for massive gypsum strata. Samples were permanently submerged at atmospheric water pressure, with groundwater recharge, flow and dissolution simulated by regular changes of water. Stress on each sample was progressively increased to a maximum of 2688 kPa. Small increases in strain were recorded by the end of each test but no failures occurred within 60 days. However, notable failure due to atmospheric water pressure and axial stress occurred over long time periods. Visible physical changes included a decrease in sample mass and volume. Similar change was recorded in ultrasonic velocities. These indicate that gypsum collapse risk beneath dams requires prolonged exposure to dissolution. The modified device performed well and was robust, and demonstrates that such a modification can provide a simple low cost system for conducting laboratory creep tests on weak rocks

Comparing the impact of environmental conditions and microphysics on the forecast uncertainty of deep convective clouds and hail

Severe hailstorms have the potential to damage buildings and crops. However, important processes for the prediction of hailstorms are insufficiently represented in operational weather forecast models. Therefore, our goal is to identify model input parameters describing environmental conditions and cloud microphysics, such as the vertical wind shear and strength of ice multiplication, which lead to large uncertainties in the prediction of deep convective clouds and precipitation. We conduct a comprehensive sensitivity analysis simulating deep convective clouds in an idealized setup of a cloud-resolving model. We use statistical emulation and variance-based sensitivity analysis to enable a Monte Carlo sampling of the model outputs across the multi-dimensional parameter space. The results show that the model dynamical and microphysical properties are sensitive to both the environmental and microphysical uncertainties in the model. The microphysical parameters lead to larger uncertainties in the output of integrated hydrometeor mass contents and precipitation variables. In particular, the uncertainty in the fall velocities of graupel and hail account for more than 65 % of the variance of all considered precipitation variables and for 30 %–90 % of the variance of the integrated hydrometeor mass contents. In contrast, variations in the environmental parameters – the range of which is limited to represent model uncertainty – mainly affect the vertical profiles of the diabatic heating rates

Less-healthy eating behaviors have a greater association with a high level of sugar-sweetened beverage consumption among rural adults than among urban adults

Background: Sugar-sweetened beverage (SSB) consumption is associated with the increasing prevalence of overweight and obesity in the United States; however, little is known about how less-healthy eating behaviors influence high levels of SSB consumption among rural adults. Objective: We assessed the frequency of SSB consumption among rural and urban adults, examined the correlates of frequent SSB consumption, and determined difference in correlates between rural and urban adults in a large region of Texas. Design: A cross-sectional study using data on 1,878 adult participants (urban = 734 and rural = 1,144), who were recruited by random digit dialing to participate in the seven-county 2006 Brazos Valley Community Health Assessment. Data included demographic characteristics, eating behaviors (SSB consumption, frequency of fast-food meals, frequency of breakfast meals, and daily fruit and vegetable intake), and household food insecurity. Results: The prevalence of any consumption of SSB and the prevalence of high consumption of SSB were significantly higher among rural adults compared with urban counterparts. The multivariable logistic regression models indicated that a high level of SSB consumption (≥3 cans or glasses SSB/day) was associated with demographic characteristics (poverty-level income and children in the home), frequent consumption of fast-food meals, infrequent breakfast meals, low fruit and vegetable intake, and household food insecurity especially among rural adults. Conclusions: This study provides impetus for understanding associations among multiple eating behaviors, especially among economically and geographically disadvantaged adults. New strategies are needed for educating consumers, not only about how to moderate their SSB intake, but also how to simultaneously disrupt the co-occurrence of undesirable eating and promote healthful eating

Exploring How Eruption Source Parameters Affect Volcanic Radiative Forcing Using Statistical Emulation

The radiative forcing caused by a volcanic eruption is dependent on several eruption source parameters such as the mass of sulfur dioxide (SO2) emitted, the eruption column height, and the eruption latitude. General circulation models with prognostic aerosol and chemistry schemes can be used to investigate how each parameter influences the volcanic forcing. However, the range of multidimensional parameter space that can be explored is restricted because such simulations are computationally expensive. Here we use statistical emulation to explore the radiative impact of eruptions over a wide covarying range of SO2 emission magnitudes, injection heights, and eruption latitudes based on only 30 simulations. We use the emulators to build response surfaces to visualize and predict the sulfate aerosol e-folding decay time, the stratospheric aerosol optical depth, and net radiative forcing of thousands of different eruptions. We find that the volcanic stratospheric aerosol optical depth and net radiative forcing are primarily determined by the mass of SO2 emitted, but eruption latitude is the most important parameter in determining the sulfate aerosol e-folding decay time. The response surfaces reveal joint effects of the eruption source parameters in influencing the net radiative forcing, such as a stronger influence of injection height for tropical eruptions than high-latitude eruptions. We also demonstrate how the emulated response surfaces can be used to find all combinations of eruption source parameters that produce a particular volcanic response, often revealing multiple solutions

The Origin of Black Hole Entropy in String Theory

I review some recent work in which the quantum states of string theory which are associated with certain black holes have been identified and counted. For large black holes, the number of states turns out to be precisely the exponential of the Bekenstein-Hawking entropy. This provides a statistical origin for black hole thermodynamics in the context of a potential quantum theory of gravity.Comment: 18 pages (To appear in the proceedings of the Pacific Conference on Gravitation and Cosmology, Seoul, Korea, February 1-6, 1996.

Gamma-Ray Telescopes (in "400 Years of Astronomical Telescopes")

The last half-century has seen dramatic developments in gamma-ray telescopes, from their initial conception and development through to their blossoming into full maturity as a potent research tool in astronomy. Gamma-ray telescopes are leading research in diverse areas such as gamma-ray bursts, blazars, Galactic transients, and the Galactic distribution of aluminum-26.Comment: 11 pages, 6 figures/ in "400 Years of Astronomical Telescopes: A Review of History, Science and Technology", ed. B.R. Brandl, R. Stuik, & J.K. Katgert-Merkeli (Exp. Astron. 26, 111-122 [2009]

Single to Double Hump Transition in the Equilibrium Distribution Function of Relativistic Particles

We unveil a transition from single peaked to bimodal velocity distribution in a relativistic fluid under increasing temperature, in contrast with a non-relativistic gas, where only a monotonic broadening of the bell-shaped distribution is observed. Such transition results from the interplay between the raise in thermal energy and the constraint of maximum velocity imposed by the speed of light. We study the Bose-Einstein, the Fermi-Dirac, and the Maxwell-J\"uttner distributions, all exhibiting the same qualitative behavior. We characterize the nature of the transition in the framework of critical phenomena and show that it is either continuous or discontinuous, depending on the group velocity. We analyze the transition in one, two, and three dimensions, with special emphasis on two-dimensions, for which a possible experiment in graphene, based on the measurement of the Johnson-Nyquist noise, is proposed.Comment: 5 pages, 5 figure

Patient symptom experience prior to a diagnosis of oesophageal or gastric cancer: a multi-methods study.

BACKGROUND: Late stage diagnosis of oesophageal and gastric cancer is common, which limits treatment options and contributes to poor survival. AIM: To explore patients' understanding, experience and presentation of symptoms before a diagnosis of oesophageal or gastric cancer. DESIGN & SETTING: Between May 2016 and October 2017, all patients newly diagnosed with oesophageal or gastric cancer were identified at weekly multidisciplinary team meetings at two large hospitals in England. A total of 321 patients were invited to participate in a survey and secondary care medical record review; 127 (40%) participants responded (102 patients had oesophageal cancer and 25 had gastric cancer). Of these, 26 participated in an additional face-to-face interview. METHOD: Survey and medical record data were analysed descriptively. Interviews were analysed using thematic analysis, informed by the Model of Pathways to Treatment. RESULTS: Participants experienced multiple symptoms before diagnosis. The most common symptom associated with oesophageal cancer was dysphagia (n = 66, 65%); for gastric cancer, fatigue or tiredness (n = 20, 80%) was the most common symptom. Understanding of heartburn, reflux and indigestion, and associated symptoms differed between participants and often contrasted with clinical perspectives. Bodily changes attributed to personal and/or lifestyle factors were self-managed, with presentation to primary care prompted when symptoms persisted, worsened, or impacted daily life, or were notably severe or unusual. Participants rarely presented all symptoms at the initial consultation. CONCLUSION: The patient interval may be lengthened by misinterpretation of key terms, such as heartburn, or misattribution or non-recognition of important bodily changes. Clearly defined symptom awareness messages may encourage earlier help-seeking, while eliciting symptom experience and meanings in primary care consultations could prompt earlier referral and diagnosis.This research was funded by the Medical Research Council and the Raymond and Beverly Sackler Fund as part of EH’s PhD. FMW was supported by an NIHR Clinician Scientist award. JDE was supported by an NHMRC Practitioner Fellowship. JB was supported by the National Institute for Health Research School for Primary Care Research

The value of remote marine aerosol measurements for constraining radiative forcing uncertainty

Aerosol measurements over the Southern Ocean are used to constrain aerosol–cloud interaction radiative forcing (RFaci) uncertainty in a global climate model. Forcing uncertainty is quantified using 1 million climate model variants that sample the uncertainty in nearly 30 model parameters. Measurements of cloud condensation nuclei and other aerosol properties from an Antarctic circumnavigation expedition strongly constrain natural aerosol emissions: default sea spray emissions need to be increased by around a factor of 3 to be consistent with measurements. Forcing uncertainty is reduced by around 7 % using this set of several hundred measurements, which is comparable to the 8 % reduction achieved using a diverse and extensive set of over 9000 predominantly Northern Hemisphere measurements. When Southern Ocean and Northern Hemisphere measurements are combined, uncertainty in RFaci is reduced by 21 %, and the strongest 20 % of forcing values are ruled out as implausible. In this combined constraint, observationally plausible RFaci is around 0.17 W m−2 weaker (less negative) with 95 % credible values ranging from −2.51 to −1.17 W m−2 (standard deviation of −2.18 to −1.46 W m−2). The Southern Ocean and Northern Hemisphere measurement datasets are complementary because they constrain different processes. These results highlight the value of remote marine aerosol measurements

hp-DGFEM for Partial Differential Equations with Nonnegative Characteristic Form

Presented as Invited Lecture at the International Symposium on Discontinuous Galerkin Methods: Theory, Computation and Applications, in Newport, RI, USA.\ud \ud We develop the error analysis for the hp-version of a discontinuous finite element approximation to second-order partial differential equations with nonnegative characteristic form. This class of equations includes classical examples of second-order elliptic and parabolic equations, first-order hyperbolic equations, as well as equations of mixed type. We establish an a priori error bound for the method which is of optimal order in the mesh size h and 1 order less than optimal in the polynomial degree p. In the particular case of a first-order hyperbolic equation the error bound is optimal in h and 1/2 an order less than optimal in p