12,261 research outputs found

    Informal names for surface features in the Apollo 15 landing area

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    Informal names and descriptions of lunar topographic features in Apollo 15 landing regio

    Some geologic observations concerning lunar geophysical models

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    The distribution of lunar geologic units in space and time and their mode of origin were considered since they provided significant data which bear on a number of current problems in lunar geophysics. Observations and problems were discussed which deal with the characterization of the upper 25 km of the lunar crust, the tectonic style of the crust, the formation of mascons within major basins, analysis of lunar magnetic anomalies, and the history of the lunar crust

    Derivation of topographic feature names in the Apollo 15 landing region

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    Location and derivation of nomenclature for lunar topographic features in Apollo 15 landing regio

    Significant achievements in the planetary geology program, 1975 - 1976

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    Developments in planetology research as reported at the 1976 NASA Planetology Program Principal Investigators' meeting are summarized. Topics range from solar system evolution, comparative planetology, and geologic processes to techniques and instrument development for future exploration

    The Anisotropic Bak-Sneppen model

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    The Bak-Sneppen model is shown to fall into a different universality class with the introduction of a preferred direction, mirroring the situation in spin systems. This is first demonstrated by numerical simulations and subsequently confirmed by analysis of the multitrait version of the model, which admits exact solutions in the extremes of zero and maximal anisotropy. For intermediate anisotropies, we show that the spatiotemporal evolution of the avalanche has a power law `tail' which passes through the system for any non-zero anisotropy but remains fixed for the isotropic case, thus explaining the crossover in behaviour. Finally, we identify the maximally anisotropic model which is more tractable and yet more generally applicable than the isotropic system

    The distribution and modes of occurrence of impact melt at lunar craters

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    Numerous studies of the returned lunar samples as well as geologic and remote-sensing investigations have emphasized the importance of impact melts on the surface of the Moon. Information concerning the distribution and relative volumes is important for (1) an improved understanding of cratering processes, (2) kinetic energy estimates and energy partitioning studies, (3) the proper interpretation of melt-bearing lunar samples, and (4) comparative planetology studies. The identification of major flows of fluidized material associated with impact craters on the surface of Venus has increased interest in impact melt flows on the other terrestrial planets. For a number of years, we have been investigating the distribution, modes of occurrence, and relative and absolute amounts of impact melt associated with lunar craters as well as the manner in which melt volumes vary as a function of crater size, morphology, and target characteristics. The results of this effort are presented

    Rift systems on Venus: An assessment of mechanical and thermal models

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    The formation and distribution of major tectonic features on Venus are closely linked to the dominant mechanism of lithospheric heat loss. Among the most spectacular and extensive of the major tectonic features on Venus are the Chasmata, deep linear valleys generally interpreted to be the products of lithospheric extension and rifting. Systems of chasmata and related features can be traced along several tectonic zones up to 20,000 km in linear extent. Mechanical and thermal models for terrestrial continental-rifting are applied to the rift systems of Venus. The models are tested against known topographic and tectonic characteristics of Venus chasmata as well as independent information on the physical properties of the Venus crust and lithosphere

    Telehealth in Palliative Care: A Systematic Review of Patient Reported Outcomes

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    A systematic review was conducted to explore published quantitative and qualitative research describing patient-reported outcomes of palliative telehealth intervention studies. Multiple databases were searched for articles published between January 2006 and May 2016, which met study criteria. Methodological quality was assessed using Cochrane Collaboration’s tool for assessing risk of bias for quantitative articles. For studies reporting qualitative outcomes, a checklist was used to evaluate trustworthiness of the methodology. Of the 6 studies reporting quantitative outcomes, 3 studies were rated as having moderate study quality, and 3 studies were rated as having low study quality. Of the 6 studies reporting qualitative outcomes, 3 reported 5 different methods for ensuring trustworthiness, whereas 1 article reported 4 methods, 1 reported 3, and 1 article reported 2 methods. Studies were notably diverse in terms of patient population, technology used, outcomes measures, and methodology. Results across studies were also variable. Methodological factors were major limitations. Recruitment problems, participant attrition, and lack of standardized outcomes measures impacted outcome assessment. Overall, research support for positive patient outcomes in palliative telehealth interventions was weak. However, all studies but one found positive results to support the intervention

    Extremal driving as a mechanism for generating long-term memory

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    It is argued that systems whose elements are renewed according to an extremal criterion can generally be expected to exhibit long-term memory. This is verified for the minimal extremally driven model, which is first defined and then solved for all system sizes N\geq2 and times t\geq0, yielding exact expressions for the persistence R(t)=[1+t/(N-1)]^{-1} and the two-time correlation function C(t_{\rm w}+t,t_{\rm w})=(1-1/N)(N+t_{\rm w})/(N+t_{\rm w}+t-1). The existence of long-term memory is inferred from the scaling of C(t_{\rm w}+t,t_{\rm w})\sim f(t/t_{\rm w}), denoting {\em aging}. Finally, we suggest ways of investigating the robustness of this mechanism when competing processes are present.Comment: 5 pages, no figures; requires IOP style files. To appear as a J. Phys. A. lette
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