Sustained eruptions on Enceladus explained by turbulent dissipation in tiger stripes

Spacecraft observations suggest that the plumes of Saturn's moon Enceladus draw water from a subsurface ocean, but the sustainability of conduits linking ocean and surface is not understood. Observations show sustained (though tidally modulated) fissure eruptions throughout each orbit, and since the 2005 discovery of the plumes. Peak plume flux lags peak tidal extension by $\sim$1 radian, suggestive of resonance. Here we show that a model of the tiger stripes as tidally-flexed slots that puncture the ice shell can simultaneously explain the persistence of the eruptions through the tidal cycle, the phase lag, and the total power output of the tiger stripe terrain, while suggesting that the eruptions are maintained over geological timescales. The delay associated with flushing and refilling of \emph{O}(1) m-wide slots with ocean water causes erupted flux to lag tidal forcing and helps to buttress slots against closure, while tidally pumped in-slot flow leads to heating and mechanical disruption that staves off slot freeze-out. Much narrower and much wider slots cannot be sustained. In the presence of long-lived slots, the 10$^6$-yr average power output of the tiger stripes is buffered by a feedback between ice melt-back and subsidence to \emph{O}(10$^{10}$) W, which is similar to the observed power output, suggesting long-term stability. Turbulent dissipation makes testable predictions for the final flybys of Enceladus by the \emph{Cassini} spacecraft. Our model shows how open connections to an ocean can be reconciled with, and sustain, long-lived eruptions. Turbulent dissipation in long-lived slots helps maintain the ocean against freezing, maintains access by future Enceladus missions to ocean materials, and is plausibly the major energy source for tiger stripe activity

Using datasets from the Internet for hydrological modeling: an example from the Kntnk Menderes Basin, Turkey

River basin development / Water resources / Data collection / Models / Hydrology / Land classification / Water management / Water scarcity / Water allocation / Stream flow / Water demand / Turkey / Kntnk Menderes Basin

Forth Replacement Crossing – Scotland, UK

AbstractThe Forth Replacement Crossing will be built across the Firth of Forth in Scotland to maintain and enhance a vital transport link. The wide estuary will be crossed by a cable stayed bridge with 3 towers and a pair of 650 m main spans. In the centre of each main span the stay cables will overlap to stabilise the central tower, a unique design feature for a bridge of this scale. The scheme design of the crossing has been carried out by the Jacobs Arup joint venture in accordance with the Eurocodes and project specific design criteria. The structure will provide a fitting 21st century icon, to stand alongside the existing cantilever rail bridge from the 19th century and road suspension bridge from the 20th century, both Grade A listed bridges

Thermal Regime of a Cold Air Trap in Central Pennsylvania, USA: the Trough Creek Ice Mine

Air temperatures internal and external to a talus cave (‘ice mine’) in central Pennsylvania were measured hourly for three years. Despite its location near the base of a talus slope, the cave demonstrated the thermal characteristics of an apparently static cave, with limited connections to the external environment other than through the cave entrance. Congelation ice that lasted until late spring formed as drip or flowstone and ponded ice from the limited influx of infiltrating water during late winter/early spring. A closed period of thermal stratification and slow warming of cave air was followed by an open period in winter months during which the cave was cooled by the influx of cold dry air. Unlike the occasionally strong and localised cooling induced by the flow of cold air from vents at the base of talus slopes, static cold traps retain their cold air and have little apparent effect on surrounding biota, instead providing potential refugia for organisms that prefer colder temperatures. Published 2012. This article is a U.S. Government work and is in the public domain in the USA

Determining the structure of the United States marine instrumentation industry and its position in the world industry

This report is a general, but comprehensive, description and analysis of industrial organization in the field of marine electronic instrumentation (MEl), a broadly defined "industry," which until now has received little systematic, scholarly attention. The report reviews the current literature on international trade and competitiveness, as well as trade and scientific journals relevant to the industry. The resul ts of a series of interviews with representatives of the industry and responsible government agencies are presented and industry and government data on R&D and output have been collected and analyzed together with other indicators of industrial performance. On the basis of these sources, the structure of the industry and its markets is characterized and the importance of marine electronic instrumenation in international high technology trade is established. Over 350 firms in the U.S. industry are identified, which annually earn total estimated gross revenues of approximately $5 billion. These firms fall into three largely distinct industry groups: (1) defense systems contractors; (2) commercial marine electronics; and (3) scientific instrumentation. The first group is by far the largest in sales volume and is oligopolistic in structure, consisting of a few large rivals for infrequent and complex defense systems contracts. The other groups are more purely competitive. Four major customer groups are distinguished: (1) military; (2) commercial and recreational shipping and boating; (3) offshore oil and gas; and (4) oceanographic/environmental. Most of the firms in the industry face international competititon. The importance of marine electronic instrumentation to technological advance and economic activity in the world's oceans is strongly apparent. Parameters affecting the international competitiveness of firms in this industry, including those relating to industry structure and behavior and governmental practices and institutions such as sponsored research, procurement, intellectual property rights, tax allowances, antitrust enforcement, small business encouragements, export controls, import restrictions, exchange rates, and technology transfer are summarized. A number of issues relating to international competititon, economic analysis, and government policy that are fruitful areas for further research also are identified.Funding was provided by the Department of Commerce, NOAA, National Ocean Service, Office of Marine Operations through a grant to the Massachusetts Centers of Excellence Corporation, grant Number NA87-AA-D-M0037

Predictive Effects of Good Self-Control and Poor Regulation on Alcohol-Related Outcomes: Do Protective Behavioral Strategies Mediate?

In the present study, we examined whether use of protective behavioral strategies mediated the relationship between self-control constructs and alcohol-related outcomes. According to the two-mode model of self-control, good self-control (planfulness; measured with Future Time Perspective, Problem Solving, and Self-Reinforcement) and poor regulation (impulsivity; measured with Present Time Perspective, Poor Delay of Gratification, Distractibility) are theorized to be relatively independent constructs rather than opposite ends of a single continuum. The analytic sample consisted of 278 college student drinkers (68% women) who responded to a battery of surveys at a single time point. Using a structural equation model based on the two-mode model of self-control, we found that good self-control predicted increased use of three types of protective behavioral strategies (Manner of Drinking, Limiting/Stopping Drinking, and Serious Harm Reduction). Poor regulation was unrelated to use of protective behavioral strategies, but had direct effects on alcohol use and alcohol problems. Further, protective behavioral strategies mediated the relationship between good self-control and alcohol use. The clinical implications of these findings are discussed

The Assessment of Protective Behavioral Strategies: Comparing the Absolute Frequency and Contingent Frequency Response Scales

The purpose of the present studies was to examine the effects of response scale on the observed relationships between protective behavioral strategies (PBS) measures and alcohol-related outcomes. We reasoned that an absolute frequency scale (stem: how many times... ; response scale: 0 times to 11 + times) conflates the frequency of using PBS with the frequency of consuming alcohol; thus, we hypothesized that the use of an absolute frequency response scale would result in positive relationships between types of PBS and alcohol-related outcomes. Alternatively, a contingent frequency scale (stem: When drinking ... how often ... ; response scale: never to always) does not conflate frequency of alcohol use with use of PBS; therefore, we hypothesized that use of a contingent frequency scale would result in negative relationships between use of PBS and alcohol-related outcomes. Two published measures of PBS were used across studies: the Protective Behavioral Strategies Survey (PBSS) and the Strategy Questionnaire (SQ). Across three studies, we demonstrate that when measured using a contingent frequency response scale, PBS measures relate negatively to alcohol-related outcomes in a theoretically consistent manner; however, when PBS measures were measured on an absolute frequency response scale, they were nonsignificantly or positively related to alcohol-related outcomes. We discuss the implications of these findings for the assessment of PBS

Dynamic Economic Analysis of Marine Pollution Prevention Technologies: An Application to Double Hulls and Electronic Charts

Marine pollution associated with shipping accidents has resulted in a Congressional mandate for double hulls on tankers in U.S. waters. In this paper, we formulate a social planner's problem using optimal control theory to examine the relative cost-effectiveness of double hulls and alternative pollution retention technologies, and the optimal installation strategy for such technologies. The model encompasses the costs and benefits associated with shipping operations, damage to the marine environment, and investment in each technology. A computer simulation of the model is used to evaluate investment strategies for two technological options: double hulls and electronic chart systems. Results indicate that electronic charts may be a far more cost-effective approach to marine pollution control

Fomalhaut's Debris Disk and Planet: Constraining the Mass of Formalhaut B from Disk Morphology

Following the optical imaging of exoplanet candidate Fomalhaut b (Fom b), we present a numerical model of how Fomalhaut's debris disk is gravitationally shaped by a single interior planet. The model is simple, adaptable to other debris disks, and can be extended to accommodate multiple planets. If Fom b is the dominant perturber of the belt, then to produce the observed disk morphology it must have a mass M(sub pl) 101.5AU, and an orbital eccentricity e(sub pl) = 0.11 - 0.13. These conclusions are independent of Fom b's photometry. To not disrupt the disk, a greater mass for Fom b demands a smaller orbit farther removed from the disk; thus, future astrometric measurement of Fom b's orbit, combined with our model of planet-disk interaction, can be used to determine the mass more precisely. The inner edge of the debris disk at a approximately equals 133AU lies at the periphery of Fom b's chaotic zone, and the mean disk eccentricity of e approximately equals 0.11 is secularly forced by the planet, supporting predictions made prior to the discovery of Fom b. However, previous mass constraints based on disk morphology rely on several oversimplifications. We explain why our constraint is more reliable. It is based on a global model of the disk that is not restricted to the planet's chaotic zone boundary. Moreover, we screen disk parent bodies for dynamical stability over the system age of approximately 100 Myr, and model them separately from their dust grain progeny; the latter's orbits are strongly affected by radiation pressure and their lifetimes are limited to approximately 0.1 Myr by destructive grain-grain collisions. The single planet model predicts that planet and disk orbits be apsidally aligned. Fomalhaut b's nominal space velocity does not bear this out, but the astrometric uncertainties are difficult to quantify. Even if the apsidal misalignment proves real, our calculated upper mass limit of 3 M(sub J) still holds. Parent bodies are evacuated from mean-motion resonances with Fom b; these empty resonances are akin to the Kirkwood gaps opened by Jupiter. The belt contains at least 3M(sub Earth) of solids that are grinding down to dust, their velocity dispersions stirred so strongly by Fom b that collisions are destructive. Such a large mass in solids is consistent with Fom b having formed in situ