358 research outputs found

    Sedimentology and kinematics of a large, retrogressive growth-fault system in Upper Carboniferous deltaic sediments, western Ireland

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    Growth faulting is a common feature of many deltaic environments and is vital in determining local sediment dispersal and accumulation, and hence in controlling the resultant sedimentary facies distribution and architecture. Growth faults occur on a range of scales, from a few centimetres to hundreds of metres, with the largest growth faults frequently being under-represented in outcrops that are often smaller than the scale of feature under investigation. This paper presents data from the exceptionally large outcrops of the Cliffs of Moher, western Ireland, where a growth-fault complex affects strata up to 60 m in thickness and extends laterally for 3 km. Study of this Namurian (Upper Carboniferous) growth-fault system enables the relationship between growth faulting and sedimentation to be detailed and permits reconstruction of the kinematic history of faulting. Growth faulting was initiated with the onset of sandstone deposition on a succession of silty mudstones that overlie a thin, marine shale. The decollement horizon developed at the top of the marine shale contact for the first nine faults, by which time aggradation in the hangingwall exceeded 60 m in thickness. After this time, failure planes developed at higher stratigraphic levels and were associated with smaller scale faults. The fault complex shows a dominantly landward retrogressive movement, in which only one fault was largely active at any one time. There is no evidence of compressional features at the base of the growth faults, thus suggesting open-ended slides, and the faults display both disintegrative and non-disintegrative structure. Thin-bedded, distal mouth bar facies dominate the hangingwall stratigraphy and, in the final stages of growth-fault movement, erosion of the crests of rollover structures resulted in the highest strata being restricted to the proximity of the fault. These upper erosion surfaces on the fault scarp developed erosive chutes that were cut parallel to flow and are downlapped by the distal hangingwall strata of younger growth faults

    Crossover effects in the Wolf-Villain model of epitaxial growth in 1+1 and 2+1 dimensions

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    A simple model of epitaxial growth proposed by Wolf and Villain is investigated using extensive computer simulations. We find an unexpectedly complex crossover behavior of the original model in both 1+1 and 2+1 dimensions. A crossover from the effective growth exponent βeff ⁣ ⁣0.37\beta_{\rm eff}\!\approx\!0.37 to βeff ⁣ ⁣0.33\beta_{\rm eff}\!\approx\!0.33 is observed in 1+1 dimensions, whereas additional crossovers, which we believe are to the scaling behavior of an Edwards--Wilkinson type, are observed in both 1+1 and 2+1 dimensions. Anomalous scaling due to power--law growth of the average step height is found in 1+1 D, and also at short time and length scales in 2+1~D. The roughness exponents ζeffc\zeta_{\rm eff}^{\rm c} obtained from the height--height correlation functions in 1+1~D ( ⁣3/4\approx\!3/4) and 2+1~D ( ⁣2/3\approx\!2/3) cannot be simultaneously explained by any of the continuum equations proposed so far to describe epitaxial growth.Comment: 11 pages, REVTeX 3.0, IC-DDV-93-00

    The first dozen years of the history of ITEP Theoretical Physics Laboratory

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    The theoretical investigations at ITEP in the years 1945-1958 are reviewed. There are exposed the most important theoretical results, obtained in the following branches of physics: 1) the theory of nuclear reactors on thermal neutrons; 2) the hydrogen bomb project ("Tube" in USSR and "Classical Super" in USA); 3) radiation theory; ~4) low temperature physics; 5) quantum electrodynamics and quantum field theories; 6) parity violation in weak interactions, the theory of β\beta-decay and other weak processes; 7) strong interaction and nuclear physics. To the review are added the English translations of few papers, originally published in Russian, but unknown (or almost unknown) to Western readers.Comment: 55 pages, 5 fig

    Prospective Cohort Study of Uterine Fibroids and Miscarriage Risk

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    We sought to determine the relationship of fibroids to pregnancy loss in a prospective cohort in which fibroid status was uniformly documented in early pregnancy. Participants had an intake interview, transvaginal ultrasonography, computer-assisted telephone interview, and follow-up assessment of outcomes. We recruited diverse participants for the Right From the Start study from 8 metropolitan areas in 3 states in the United States during 2000-2012. Participants were at least 18 years of age, trying to become pregnant or at less than 12 weeks' gestation, not using fertility treatments, fluent in English or Spanish, and available for telephone interviews. Miscarriage was defined as loss before 20 weeks' gestation. Fibroid presence, number, type, and volume were assessed using standardized ultrasonography methods. We used proportional hazards models to estimate associations. Among 5,512 participants, 10.4% had at least 1 fibroid, and 10.8% experienced a miscarriage. Twenty-three percent had experienced a prior miscarriage and 52% prior births. Presence of fibroids was associated with miscarriage in models without adjustments. Adjusting for key confounders indicated no increase in risk (adjusted hazard ratio = 0.83, 95% confidence interval: 0.63, 1.08). No characteristic of fibroids was associated with risk. Prior evidence attributing miscarriage to fibroids is potentially biased. These findings imply that surgical removal of fibroids to reduce risk of miscarriage deserves careful scrutiny

    Surface Kinetics and Generation of Different Terms in a Conservative Growth Equation

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    A method based on the kinetics of adatoms on a growing surface under epitaxial growth at low temperature in (1+1) dimensions is proposed to obtain a closed form of local growth equation. It can be generalized to any growth problem as long as diffusion of adatoms govern the surface morphology. The method can be easily extended to higher dimensions. The kinetic processes contributing to various terms in the growth equation (GE) are identified from the analysis of in-plane and downward hops. In particular, processes corresponding to the (h -> -h) symmetry breaking term and curvature dependent term are discussed. Consequence of these terms on the stable and unstable transition in (1+1) dimensions is analyzed. In (2+1) dimensions it is shown that an additional (h -> -h) symmetry breaking term is generated due to the in-plane curvature associated with the mound like structures. This term is independent of any diffusion barrier differences between in-plane and out of-plane migration. It is argued that terms generated in the presence of downward hops are the relevant terms in a GE. Growth equation in the closed form is obtained for various growth models introduced to capture most of the processes in experimental Molecular Beam Epitaxial growth. Effect of dissociation is also considered and is seen to have stabilizing effect on the growth. It is shown that for uphill current the GE approach fails to describe the growth since a given GE is not valid over the entire substrate.Comment: 14 pages, 7 figure

    From dynamical scaling to local scale-invariance: a tutorial

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    Dynamical scaling arises naturally in various many-body systems far from equilibrium. After a short historical overview, the elements of possible extensions of dynamical scaling to a local scale-invariance will be introduced. Schr\"odinger-invariance, the most simple example of local scale-invariance, will be introduced as a dynamical symmetry in the Edwards-Wilkinson universality class of interface growth. The Lie algebra construction, its representations and the Bargman superselection rules will be combined with non-equilibrium Janssen-de Dominicis field-theory to produce explicit predictions for responses and correlators, which can be compared to the results of explicit model studies. At the next level, the study of non-stationary states requires to go over, from Schr\"odinger-invariance, to ageing-invariance. The ageing algebra admits new representations, which acts as dynamical symmetries on more general equations, and imply that each non-equilibrium scaling operator is characterised by two distinct, independent scaling dimensions. Tests of ageing-invariance are described, in the Glauber-Ising and spherical models of a phase-ordering ferromagnet and the Arcetri model of interface growth.Comment: 1+ 23 pages, 2 figures, final for

    HiFlo-DAT: Indian Himalayan Flood Database, for Disaster Risk Reduction in the Kullu District

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    ‘HiFlo-DAT’ is an ongoing bi-lateral research project (UK and India, UGC-UKIERI funded, 2018-2020), focussing on historical floods in the Kullu District, Himachal Pradesh, Indian Himalaya. The project team, comprising academic and state/district disaster management authorities, are together developing a new historical flood hazard database as a foundation for improved disaster risk management functions in the region. This is necessary as current management relies on incomplete knowledge of past flood event occurrence, bringing elevated exposure/ risk to development. The HiFlo-DAT database provides a step-change, drawing on extensive mining of archive materials held in private and public collections in India, UK and USA. These materials include newspapers, government reports/ registers, diaries, books, academic articles etc. Most extensive are English language Indian region newspapers, of which we have amassed overlapping holdings over 184 years (1835 to present), totalling c. 150,000 pages. Our acquisition includes coverage of annual periods where publications are digitally searchable (e.g. The Tribune, The Times of India, The Indian Express). In contrast, where archives remain in an analogue microfilm format (e.g. The Civil and Military Gazette, The Friend of India) we restricted data searches to monsoon season months (i.e. July to September) given this is the typical window for floods in the Western Himalaya. The HiFlo-DAT database architecture takes account of best practice, having systematically reviewed global (most commonly European) flood database research in the last c. 30 years, in regard to database structure, data entry/verification protocols, analytical foci and societal impact. HiFlo-DAT has 103 possible entry categories for each event record, which are aggregated into 11 principal groups (i.e. database management, citation information, timing/ duration, location, causation and hydro-meteorological magnitude, channel/ catchment geomorphological impacts, damage/ destruction/ costs, human casualties, pre-event actions, event response, post-event actions). The bi-lateral review of source materials and population of the database are governed by an agreed set of protocols. Initial analyses are focussing on: (1) event spatial/ temporal/ impact signatures; (2) the relationship between flood occurrence and rainfall conditions. The latter makes use of a unique long-term daily rainfall series for Naggar Farm, being compiled from British government records (1891-1950) and current IARI data (1962 to present). HiFlo-DAT is designed with capacity for future updating, and will be open access via the BathSPAdata repository and HPSDMA website

    Plasma Wakefield Acceleration with a Modulated Proton Bunch

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    The plasma wakefield amplitudes which could be achieved via the modulation of a long proton bunch are investigated. We find that in the limit of long bunches compared to the plasma wavelength, the strength of the accelerating fields is directly proportional to the number of particles in the drive bunch and inversely proportional to the square of the transverse bunch size. The scaling laws were tested and verified in detailed simulations using parameters of existing proton accelerators, and large electric fields were achieved, reaching 1 GV/m for LHC bunches. Energy gains for test electrons beyond 6 TeV were found in this case.Comment: 9 pages, 7 figure
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