WorldWideScience

Sample records for singleton earth convection

  1. Might electrical earthing affect convection of light

    International Nuclear Information System (INIS)

    Budrikis, Z.L.

    1982-01-01

    Partial convection of light by moving media was predicted by Fresnel and verified by Fizeau, Zeeman and others. It is accepted as an important argument in favour of the Special Theory of Relativity. The suggestion is made here that the convection is partial only when the propagating medium is moved with respect to its electrically earthed surroundings and that it would be total if an earthed shield was co-moving with the medium. This is based on a reinterpretation of Maxwell's equations wherein they are seen as macroscopic relationships that are in each case valid only in respect of a particular inertial frame of reference, the local electrical earth frame. (Auth.)

  2. Earth's core convection: Boussinesq approximation or incompressible approach?

    Czech Academy of Sciences Publication Activity Database

    Anufriev, A. P.; Hejda, Pavel

    2010-01-01

    Roč. 104, č. 1 (2010), s. 65-83 ISSN 0309-1929 R&D Projects: GA AV ČR IAA300120704 Grant - others:INTAS(XE) 03-51-5807 Institutional research plan: CEZ:AV0Z30120515 Keywords : geodynamic models * core convection * Boussinesq approximation Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 0.831, year: 2010

  3. Satellite Detection of the Convection Generated Stresses in Earth

    Science.gov (United States)

    Liu, Han-Shou; Kolenkiewicz, Ronald; Li, Jin-Ling; Chen, Jiz-Hong

    2003-01-01

    We review research developments on satellite detection of the convection generated stresses in the Earth for seismic hazard assessment and Earth resource survey. Particular emphasis is laid upon recent progress and results of stress calculations from which the origin and evolution of the tectonic features on Earth's surface can be scientifically addressed. An important aspect of the recent research development in tectonic stresses relative to earthquakes is the implications for earthquake forecasting and prediction. We have demonstrated that earthquakes occur on the ring of fire around the Pacific in response to the tectonic stresses induced by mantle convection. We propose a systematic global assessment of the seismic hazard based on variations of tectonic stresses in the Earth as observed by satellites. This space geodynamic approach for assessing the seismic hazard is unique in that it can pinpoint the triggering stresses for large earthquakes without ambiguities of geological structures, fault geometries, and other tectonic properties. Also, it is distinct from the probabilistic seismic hazard assessment models in the literature, which are based only on extrapolations of available earthquake data.

  4. Convectively driven decadal zonal accelerations in Earth's fluid core

    Science.gov (United States)

    More, Colin; Dumberry, Mathieu

    2018-04-01

    Azimuthal accelerations of cylindrical surfaces co-axial with the rotation axis have been inferred to exist in Earth's fluid core on the basis of magnetic field observations and changes in the length-of-day. These accelerations have a typical timescale of decades. However, the physical mechanism causing the accelerations is not well understood. Scaling arguments suggest that the leading order torque averaged over cylindrical surfaces should arise from the Lorentz force. Decadal fluctuations in the magnetic field inside the core, driven by convective flows, could then force decadal changes in the Lorentz torque and generate zonal accelerations. We test this hypothesis by constructing a quasi-geostrophic model of magnetoconvection, with thermally driven flows perturbing a steady, imposed background magnetic field. We show that when the Alfvén number in our model is similar to that in Earth's fluid core, temporal fluctuations in the torque balance are dominated by the Lorentz torque, with the latter generating mean zonal accelerations. Our model reproduces both fast, free Alfvén waves and slow, forced accelerations, with ratios of relative strength and relative timescale similar to those inferred for the Earth's core. The temporal changes in the magnetic field which drive the time-varying Lorentz torque are produced by the underlying convective flows, shearing and advecting the magnetic field on a timescale associated with convective eddies. Our results support the hypothesis that temporal changes in the magnetic field deep inside Earth's fluid core drive the observed decadal zonal accelerations of cylindrical surfaces through the Lorentz torque.

  5. Singleton strings

    Energy Technology Data Exchange (ETDEWEB)

    Engquist, J. [Institute for Theoretical Physics and Spinoza Institute, Utrecht University (Netherlands); Sundell, P. [INFN, Pisa (Italy); Scuola Normale Superiore, Pisa (Italy); Tamassia, L. [Instituut voor Theoretische Fysica, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven (Belgium)

    2007-05-15

    The group theoretical structure underlying physics in anti de Sitter (AdS) spacetime is intrinsically different with respect to the flat case, due to the presence of special ultra-short representations, named singletons, that do not admit a flat space limit. The purpose of this collaboration is to exploit this feature in the study of string and brane dynamics in AdS spacetime, in particular while trying to establish a connection between String Theory in AdS backgrounds (in the tensionless limit) and Higher-Spin Gauge Theory. (orig.)

  6. Convective cells of internal gravity waves in the earth's atmosphere with finite temperature gradient

    Directory of Open Access Journals (Sweden)

    O. Onishchenko

    2013-03-01

    Full Text Available In this paper, we have investigated vortex structures (e.g. convective cells of internal gravity waves (IGWs in the earth's atmosphere with a finite vertical temperature gradient. A closed system of nonlinear equations for these waves and the condition for existence of solitary convective cells are obtained. In the atmosphere layers where the temperature decreases with height, the presence of IGW convective cells is shown. The typical parameters of such structures in the earth's atmosphere are discussed.

  7. Archimedean Proof of the Physical Impossibility of Earth Mantle Convection

    OpenAIRE

    Herndon, J. Marvin

    2010-01-01

    Eight decades ago, Arthur Holmes introducted the idea of mantle convection as a mechanism for continental drift. Five decades ago, continental drift was modified to become plate tectonics theory, which included mantle convection as an absolutely critical component. Using the submarine design and operation concept of "neutral buoyancy", which follows from Archimedes' discoveries, the concept of mantle convection is proven to be incorrect, concomitantly refuting plate tectonics, refuting all ma...

  8. Mixing properties of thermal convection in the earth's mantle

    NARCIS (Netherlands)

    Schmalzl, J.T.

    1996-01-01

    The structure of mantle convection will greatly influence the generation and the survival of compositional heterogeneities. Conversely, geochemical observations can be used to obtain information about heterogeneities in the mantle and then, with certain model assumptions, information about the

  9. Large Prandtl number finite-amplitude thermal convection with Maxwell viscoelasticity. [earth mantle rheological model

    Science.gov (United States)

    Ivins, E. R.; Unti, T. W. J.; Phillips, R. J.

    1982-01-01

    It has long been known that the earth behaves viscoelastically. Viscoelasticity may be of importance in two aspects of mantle convection, including time-dependent behavior and local storage of recoverable work. The present investigation makes use of thermal convection in a box as a prototype of mantle flow. It is demonstrated that recoverable work can be important to the local mechanical energy balance in the descending lithosphere. It is shown that, even when assuming large viscoelastic parameters, an inherent time-dependence of viscoelastic convection appears only in local exchanges of mechanical energy. There is no strong exchange between buoyant potential energy and recoverable strain energy in the Rayleigh number range investigated. The investigation is mainly concerned with viscoelastic effects occurring on a buoyant time scale. It is found that viscoelastic effects have a negligible influence on the long term thermal energetics of mantle convection.

  10. Preconception and prenatal urinary concentrations of phenols and birth size of singleton infants born to mothers and fathers from the Environment and Reproductive Health (EARTH) study.

    Science.gov (United States)

    Messerlian, Carmen; Mustieles, Vicente; Minguez-Alarcon, Lidia; Ford, Jennifer B; Calafat, Antonia M; Souter, Irene; Williams, Paige L; Hauser, Russ

    2018-02-22

    Although pregnancy concentrations of some phenols have been associated with infant size at birth, there is limited data on the effect of preconception exposure. We aimed to examine paternal and maternal preconception and maternal prenatal urinary phenol concentrations in relation to birth weight and head circumference. We evaluated 346 singletons born to 346 mothers and 184 fathers (184 couples) from a prospective preconception cohort of subfertile couples from the Environment and Reproductive Health (EARTH) Study in Boston, USA. We used multiple urine samples collected before the index pregnancy in both men and women to estimate mean preconception urinary benzophenone-3, triclosan, butylparaben, propylparaben, methylparaben, or ethylparaben concentrations. We also estimated mean maternal prenatal urinary phenol concentrations by averaging trimester-specific urine samples. Birth weight and head circumference were abstracted from delivery records. We estimated the association of natural log-phenol concentrations with birth outcomes using multivariable linear regression models, adjusting for known confounders. In adjusted models, each log-unit increase in paternal preconception benzophenone-3 concentration was associated with a 137 g increase in birth weight (95% CI: 60, 214). Additional adjustment for prenatal benzophenone-3 concentration strengthened this association. None of the maternal preconception phenol concentrations were associated with birth weight. However, maternal prenatal triclosan concentrations were associated with a 38 g decrease in birth weight (95% CI: -76, 0). Few associations were observed between phenols and head circumference except for a decrease of 0.27 cm (95% CI: -54, 0) in relation to maternal preconception methylparaben concentration. Although our findings should be interpreted in light of inherent study limitations, these results suggest potential evidence of associations between some paternal or maternal phenol concentrations and

  11. Long Mantle Mixing Times for the early Earth Inferred from Convection Models with Grain-Damage

    Science.gov (United States)

    Foley, B. J.; Rizo, H.

    2015-12-01

    Mantle dynamics on the Hadean and Archean Earth, particularly whether plate tectonics was in operation or not, is hotly debated. One important constraint comes from evidence for long mantle mixing timescales in the early Earth based on observations of early-formed geochemical heterogeneities. Specifically, 142Nd anomalies recorded in 3.8 to 3.4 Ga rocks from southwest Greenland [e.g. 1] and 2.7 Ga rocks from the Superior Province (Canada) [2] indicate that chemically heterogeneous reservoirs, formed during the first ~ 10-100 million years of Earths' history, survived their remixing into the mantle for over 1 Gyr. Such a long mantle mixing time is difficult to explain with a traditional model of plate tectonics, where plate speeds increase significantly in the past due to a hotter mantle, thus prompting appeals to stagnant lid convection on the early Earth [e.g. 2]. However, a new model for generating plate tectonics from mantle convection based on grainsize reduction (called grain-damage) proposes that plate speeds may have decreased with increasing mantle temperature. Higher mantle temperatures lead to higher grain-growth rates that inhibit the formation of weak lithospheric shear zones. As a result, plate boundaries are more viscous and provide a stronger resistance to plate motions, and thus mantle-mixing times in the mobile lid regime may still be long even at Hadean or Archean mantle temperatures. We use new numerical models of convection with grain-damage to constrain mantle-mixing times for the early Earth with the effects of grainsize variation included. We find that mantle mixing times for mobile lid convection remain long as mantle temperature increases because of faster grain-growth rates in the mantle and lithosphere. Therefore the preservation of chemical heterogeneities for over 1 Gyr in the Hadean-Archean mantle is not inconsistent with the operation of mobile lid convection and subduction at this time. Early Earth subduction may still have differed

  12. Geodynamo and mantle convection simulations on the Earth Simulator using the Yin-Yang grid

    International Nuclear Information System (INIS)

    Kageyama, Akira; Yoshida, Masaki

    2005-01-01

    We have developed finite difference codes based on the Yin-Yang grid for the geodynamo simulation and the mantle convection simulation. The Yin-Yang grid is a kind of spherical overset grid that is composed of two identical component grids. The intrinsic simplicity of the mesh configuration of the Yin-Yang grid enables us to develop highly optimized simulation codes on massively parallel supercomputers. The Yin-Yang geodynamo code has achieved 15.2 Tflops with 4096 processors on the Earth Simulator. This represents 46% of the theoretical peak performance. The Yin-Yang mantle code has enabled us to carry out mantle convection simulations in realistic regimes with a Rayleigh number of 10 7 including strongly temperature dependent viscosity with spatial contrast up to 10 6

  13. Tomographic and Geodynamic Constraints on Convection-Induced Mixing in Earth's Deep Mantle

    Science.gov (United States)

    Hafter, D. P.; Forte, A. M.; Bremner, P. M.; Glisovic, P.

    2017-12-01

    Seismological studies reveal two large low-shear-velocity provinces (LLSVPs) in the lowermost mantle (e.g., Su et al. 1994; Wang & Wen 2007; He & Wen 2012), which may represent accumulations of subducted slabs at the CMB (Tan & Gurnis 2005; Christensen & Hoffman 1994) or primordial material generated in the early differentiation of Earth (e.g. Li et al. 2014). The longevity or stability of these large-scale heterogeneities in the deep mantle depends on the vigor and spatial distribution of the convective circulation, which is in turn dependent on the distribution of mantle buoyancy and viscosity (e.g. Glisovic & Forte 2015). Here we explore the state of convective mixing in the mantle using the ASPECT convection code (Kronbichler et al. 2012). A series of experiments are conducted to consider the geochemical and dynamical contributions of LLSVPs to deep-mantle upwellings and corresponding plume-sourced volcanism. The principal feature of these experiments is the use of particle tracers to track geochemical changes in the LLSVPs and mantle plumes in addition to identifying those parts of the mantle that may remain unmixed. We employ 3-D mantle density anomalies derived from joint inversions of seismic, geodynamic and mineral physics constraints and geodynamically-constrained viscosity distributions (Glisovic et al. 2015) to ensure that the predicted flow fields yield a good match to key geophysical constraints (e.g. heat flow, global gravity anomalies and plate velocities).

  14. Microwave heating device for internal heating convection experiments, applied to Earth's mantle dynamics.

    Science.gov (United States)

    Surducan, E; Surducan, V; Limare, A; Neamtu, C; Di Giuseppe, E

    2014-12-01

    We report the design, construction, and performances of a microwave (MW) heating device for laboratory experiments with non-contact, homogeneous internal heating. The device generates MW radiation at 2.47 GHz from a commercial magnetron supplied by a pulsed current inverter using proprietary, feedback based command and control hardware and software. Specially designed MW launchers direct the MW radiation into the sample through a MW homogenizer, devised to even the MW power distribution into the sample's volume. An adjustable MW circuit adapts the MW generator to the load (i.e., the sample) placed in the experiment chamber. Dedicated heatsinks maintain the MW circuits at constant temperature throughout the experiment. Openings for laser scanning for image acquisition with a CCD camera and for the cooling circuits are protected by special MW filters. The performances of the device are analyzed in terms of heating uniformity, long term output power stability, and load matching. The device is used for small scale experiments simulating Earth's mantle convection. The 30 × 30 × 5 cm(3) convection tank is filled with a water‑based viscous fluid. A uniform and constant temperature is maintained at the upper boundary by an aluminum heat exchanger and adiabatic conditions apply at the tank base. We characterize the geometry of the convective regime as well as its bulk thermal evolution by measuring the velocity field by Particle Image Velocimetry and the temperature field by using Thermochromic Liquid Crystals.

  15. Stochastic generation of MAC waves and implications for convection in Earth's core

    Science.gov (United States)

    Buffett, Bruce; Knezek, Nicholas

    2018-03-01

    Convection in Earth's core can sustain magnetic-Archemedes-Coriolis (MAC) waves through a variety of mechanisms. Buoyancy and Lorentz forces are viable sources for wave motion, together with the effects of magnetic induction. We develop a quantitative description for zonal MAC waves and assess the source mechanisms using a numerical dynamo model. The largest sources at conditions accessible to the dynamo model are due to buoyancy forces and magnetic induction. However, when these sources are extrapolated to conditions expected in Earth's core, the Lorentz force emerges as the dominant generation mechanism. This source is expected to produce wave velocities of roughly 2 km yr-1 when the internal magnetic field is characterized by a dimensionless Elsasser number of roughly Λ ≈ 10 and the root-mean-square convective velocity defines a magnetic Reynolds number of Rm ≈ 103. Our preferred model has a radially varying stratification and a constant (radial) background magnetic field. It predicts a broad power spectrum for the wave velocity with most power distributed across periods from 30 to 100 yr.

  16. Numerical experiments on thermal convection of highly compressible fluids with variable viscosity and thermal conductivity: Implications for mantle convection of super-Earths

    Science.gov (United States)

    Kameyama, Masanori; Yamamoto, Mayumi

    2018-01-01

    We conduct a series of numerical experiments of thermal convection of highly compressible fluids in a two-dimensional rectangular box, in order to study the mantle convection on super-Earths. The thermal conductivity and viscosity are assumed to exponentially depend on depth and temperature, respectively, while the variations in thermodynamic properties (thermal expansivity and reference density) with depth are taken to be relevant for the super-Earths with 10 times the Earth's. From our experiments we identified a distinct regime of convecting flow patterns induced by the interplay between the adiabatic temperature change and the spatial variations in viscosity and thermal conductivity. That is, for the cases with strong temperature-dependent viscosity and depth-dependent thermal conductivity, a "deep stratosphere" of stable thermal stratification is formed at the base of the mantle, in addition to thick stagnant lids at their top surfaces. In the "deep stratosphere", the fluid motion is insignificant particularly in the vertical direction in spite of smallest viscosity owing to its strong dependence on temperature. Our finding may further imply that some of super-Earths which are lacking in mobile tectonic plates on their top surfaces may have "deep stratospheres" at the base of their mantles.

  17. Mantle convection and the distribution of geochemical reservoirs in the silicate shell of the Earth

    Science.gov (United States)

    Walzer, Uwe; Hendel, Roland

    2010-05-01

    We present a dynamic 3-D spherical-shell model of mantle convection and the evolution of the chemical reservoirs of the Earth`s silicate shell. Chemical differentiation, convection, stirring and thermal evolution constitute an inseparable dynamic system. Our model is based on the solution of the balance equations of mass, momentum, energy, angular momentum, and four sums of the number of atoms of the pairs 238U-206Pb, 235U-207Pb, 232Th-208Pb, and 40K-40Ar. Similar to the present model, the continental crust of the real Earth was not produced entirely at the start of the evolution but developed episodically in batches [1-7]. The details of the continental distribution of the model are largely stochastic, but the spectral properties are quite similar to the present real Earth. The calculated Figures reveal that the modeled present-day mantle has no chemical stratification but we find a marble-cake structure. If we compare the observational results of the present-day proportion of depleted MORB mantle with the model then we find a similar order of magnitude. The MORB source dominates under the lithosphere. In our model, there are nowhere pure unblended reservoirs in the mantle. It is, however, remarkable that, in spite of 4500 Ma of solid-state mantle convection, certain strong concentrations of distributed chemical reservoirs continue to persist in certain volumes, although without sharp abundance boundaries. We deal with the question of predictable and stochastic portions of the phenomena. Although the convective flow patterns and the chemical differentiation of oceanic plateaus are coupled, the evolution of time-dependent Rayleigh number, Rat , is relatively well predictable and the stochastic parts of the Rat(t)-curves are small. Regarding the juvenile growth rates of the total mass of the continents, predictions are possible only in the first epoch of the evolution. Later on, the distribution of the continental-growth episodes is increasingly stochastic

  18. Magnetodynamo lifetimes for rocky, Earth-mass exoplanets with contrasting mantle convection regimes

    Science.gov (United States)

    van Summeren, Joost; Gaidos, Eric; Conrad, Clinton P.

    2013-05-01

    We used a thermal model of an iron core to calculate magnetodynamo evolution in Earth-mass rocky planets to determine the sensitivity of dynamo lifetime and intensity to planets with different mantle tectonic regimes, surface temperatures, and core properties. The heat flow at the core-mantle boundary (CMB) is derived from numerical models of mantle convection with a viscous/pseudoplastic rheology that captures the phenomenology of plate-like tectonics. Our thermal evolution models predict a long-lived ( 8 Gyr) field for Earth and similar dynamo evolution for Earth-mass exoplanets with plate tectonics. Both elevated surface temperature and pressure-dependent mantle viscosity reduce the CMB heat flow but produce only slightly longer-lived dynamos ( 8-9.5 Gyr). Single-plate ("stagnant lid") planets with relatively low CMB heat flow produce long-lived ( 10.5 Gyr) dynamos. These weaker dynamos can cease for several billions of years and subsequently reactivate due to the additional entropy production associated with inner core growth, a possible explanation for the absence of a magnetic field on present-day Venus. We also show that dynamo operation is sensitive to the initial temperature, size, and solidus of a planet's core. These dependencies would severely challenge any attempt to distinguish exoplanets with plate tectonics and stagnant lids based on the presence or absence of a magnetic field.

  19. Decadal Polar Motion of the Earth Excited by the Convective Outer Core From Geodynamo Simulations

    Science.gov (United States)

    Kuang, W.; Chao, B. F.; Chen, J.

    2017-10-01

    Long time geodetic observation records show that the orientation of the Earth's rotation axis with respect to the terrestrial reference frame, or polar motion, changes on a broad range of timescales. Apart from external torques from the luni-solar tides, these changes are excited by interactions among different components of the Earth system. The convective fluid outer core has long been conjectured a likely contributor to the observed polar motion on timescales upward of decades, such as the ˜30 year Markowitz wobble. We investigated the electromagnetic coupling scenario across the core-mantle boundary via numerical geodynamo simulation for different geodynamo parameters (Rayleigh numbers and magnetic Rossby numbers). Our simulated polar motion varies strongly with the dynamo parameters, while its excitation on decadal timescales appear to converge asymptotically within the adopted range of numerical Rossby numbers. Three strongest asymptotic modes emerge from numerical results, with periods around 30, 40, and 60 years for the prograde excitation and around 24, 30, and 60 years for the retrograde excitation. Their amplitudes are all larger than 5 × 10-8, or approximately 10 milliseconds of arc. The results suggest that the electromagnetic core-mantle coupling could explain a substantial portion, if not all, of the observed decadal polar motion. In particular, the predicted 60 year polar motion deserves special attention for future observations and studies.

  20. Archean greenstone-tonalite duality: Thermochemical mantle convection models or plate tectonics in the early Earth global dynamics?

    Science.gov (United States)

    Kerrich, Robert; Polat, Ali

    2006-03-01

    Mantle convection and plate tectonics are one system, because oceanic plates are cold upper thermal boundary layers of the convection cells. As a corollary, Phanerozoic-style of plate tectonics or more likely a different version of it (i.e. a larger number of slowly moving plates, or similar number of faster plates) is expected to have operated in the hotter, vigorously convecting early Earth. Despite the recent advances in understanding the origin of Archean greenstone-granitoid terranes, the question regarding the operation of plate tectonics in the early Earth remains still controversial. Numerical model outputs for the Archean Earth range from predominantly shallow to flat subduction between 4.0 and 2.5 Ga and well-established steep subduction since 2.5 Ga [Abbott, D., Drury, R., Smith, W.H.F., 1994. Flat to steep transition in subduction style. Geology 22, 937-940], to no plate tectonics but rather foundering of 1000 km sectors of basaltic crust, then "resurfaced" by upper asthenospheric mantle basaltic melts that generate the observed duality of basalts and tonalities [van Thienen, P., van den Berg, A.P., Vlaar, N.J., 2004a. Production and recycling of oceanic crust in the early earth. Tectonophysics 386, 41-65; van Thienen, P., Van den Berg, A.P., Vlaar, N.J., 2004b. On the formation of continental silicic melts in thermochemical mantle convection models: implications for early Earth. Tectonophysics 394, 111-124]. These model outputs can be tested against the geological record. Greenstone belt volcanics are composites of komatiite-basalt plateau sequences erupted from deep mantle plumes and bimodal basalt-dacite sequences having the geochemical signatures of convergent margins; i.e. horizontally imbricated plateau and island arc crust. Greenstone belts from 3.8 to 2.5 Ga include volcanic types reported from Cenozoic convergent margins including: boninites; arc picrites; and the association of adakites-Mg andesites- and Nb-enriched basalts. Archean cratons

  1. Laboratory convection experiments with internal, noncontact, microwave generated heating, applied to Earth's mantle dynamics

    Science.gov (United States)

    Limare, Angela; Surducan, Emanoil; di Giuseppe, Erika; Surducan, Vasile; Neamtu, Camelia; Vilella, Kenny; Fourel, Loic; Farnetani, Cinzia; Kaminski, Edouard; Jaupart, Claude

    2014-05-01

    The thermal evolution of terrestrial planets is controlled by secular cooling and internal heating due to the decay of radiogenic isotopes, two processes which are equivalent from the standpoint of convection dynamics. Few studies have been devoted to the intrinsic characteristics of this form of convection, which are dominated by instabilities of a single boundary layer and which involve a non-isentropic interior thermal structure. Laboratory studies of such convection have been plagued by considerable technical difficulties and have been mostly restricted to aqueous solutions with moderate values of the Prandtl number, contrary to planetary mantles. Here, we describe a new laboratory setup to generate internal heating in controlled conditions based on microwave (MW) absorption. The advantages of our technique include, but are not limited to: (1) a volumetric heat source that can be localized or distributed in space, (2) selectively heating part of the volume with time varying intensity and space distribution. Our tank prototype had horizontal dimensions of 30 cm × 30 cm and 5 cm height. A uniform and constant temperature was maintained at the upper boundary by an aluminium heat exchanger and adiabatic conditions were imposed at the tank base. Experimental fluids were hydroxyethylcellulose - water mixtures whose viscosities were varied within a wide range depending on concentration. Experimental Prandtl numbers were set at values larger than 100. Thermochromic Liquid Crystals (TLC) were used to visualize the temperature field, and the velocity field was determined using Particle Image Velocimetry (PIV). The Rayleigh-Roberts number was varied from 105 to 107. We also conducted numerical simulations in 3D cartesian geometry using Stag-3D (Tackley 1993) to reproduce the experimental conditions, including the tank aspect ratio and the temperature dependence of physical properties. We observed that convection is driven by cold descending plumes generated at the upper

  2. Parallel numerical simulation of the thermal convection in the Earth's outer core on the cubed-sphere

    Science.gov (United States)

    Yin, Liang; Yang, Chao; Ma, Shi-Zhuang; Huang, Ji-Zu; Cai, Ying

    2017-06-01

    Numerical simulations of the thermal convection in a rotating spherical shell play an important role in dynamo simulations. In this paper, we present a highly scalable parallel solver for the Earth's outer core convection. The solver uses a second-order cell-centred finite volume spatial discretization based on the cubed-sphere grid instead of the traditional latitude-longitude grid to avoid grid singularity and enhance the parallel scalability. A second-order approximate factorization method combined with the Crank-Nicolson scheme is employed for splitting temporal integration. The two resultant sparse linear systems are solved by the Krylov subspace iterative method pre-conditioned with a restricted additive Schwarz pre-conditioner based on the domain decomposition of the cubed-sphere. The numerical results are in good agreement with the benchmark solutions and more accurate than the existing finite volume results. The solvers scale to over 10 000 processor cores with nearly linear scalability on the Sunway TaihuLight supercomputer.

  3. Causes of convection in the earth's magnetosphere: a review of developments during the IMS

    Energy Technology Data Exchange (ETDEWEB)

    Cowley, S.W.H.

    1982-08-01

    The physical processes which give rise to convection in the earth's magnetosphere have been the subject of active debate for many years. Most of the discussion has centered on two basic pictures, one in which closed magnetospheric flux tubes are transported from dayside to nightside in a boundary layer around the flanks of the magnetosphere by a 'viscouslike' process occurring at the magnetopause and the other in which open flux tubes are transported over the poles of the earth after reconnection has taken place with the interplanetary magnetic field. These processes may coexist on a continuous basis, and the question then arises as to their relative contributions to usual total cross-magnetospheric voltages of approx.40--100 kV. The first detailed observations of plasmas and fields in the vicinity of the dayside magnetopause have recently been made during the International Magnetospheric Study by the ISEE 1 and 2 spacecraft and are discussed in this paper in relation to this question. Observations which relate to the occurrence of 'quasi-steady' as well as impulsive flux transfer event (FTE) reconnection are reviewed in detail in the paper, together with measurements of the properties of the boundary layer on the magnetospheric flanks. Particular emphasis is given to the interpretation of these data in terms of the physical process occurring. It is argued that the ISEE observations of quasi-steady reconnection are indeed compatible with the process playing a major role in magnetospheric dynamics.

  4. Feature singletons attract spatial attention independently of feature priming.

    Science.gov (United States)

    Yashar, Amit; White, Alex L; Fang, Wanghaoming; Carrasco, Marisa

    2017-08-01

    People perform better in visual search when the target feature repeats across trials (intertrial feature priming [IFP]). Here, we investigated whether repetition of a feature singleton's color modulates stimulus-driven shifts of spatial attention by presenting a probe stimulus immediately after each singleton display. The task alternated every two trials between a probe discrimination task and a singleton search task. We measured both stimulus-driven spatial attention (via the distance between the probe and singleton) and IFP (via repetition of the singleton's color). Color repetition facilitated search performance (IFP effect) when the set size was small. When the probe appeared at the singleton's location, performance was better than at the opposite location (stimulus-driven attention effect). The magnitude of this attention effect increased with the singleton's set size (which increases its saliency) but did not depend on whether the singleton's color repeated across trials, even when the previous singleton had been attended as a search target. Thus, our findings show that repetition of a salient singleton's color affects performance when the singleton is task relevant and voluntarily attended (as in search trials). However, color repetition does not affect performance when the singleton becomes irrelevant to the current task, even though the singleton does capture attention (as in probe trials). Therefore, color repetition per se does not make a singleton more salient for stimulus-driven attention. Rather, we suggest that IFP requires voluntary selection of color singletons in each consecutive trial.

  5. Singleton status and childhood obesity: Investigating effects and mechanisms Status :

    OpenAIRE

    Maoyong Fan; Yanhong Jin

    2015-01-01

    Over the past four decades, paralleling the increasing prevalence of childhood obesity, the share of families with only one child has been rising steadily. Using three waves of the National Survey of Children's Health, we examine the effect of being the only child in a family on childhood obesity and the mechanisms through which singleton status might affect childhood obesity. We find gender-specific and age-dependent singleton effects. That is, singletons have a higher level of body mass ind...

  6. Convective thinning of the lithosphere: A mechanism for rifting and mid-plate volcanism on Earth, Venus, and Mars

    Science.gov (United States)

    Spohn, T.; Schubert, G.

    1982-01-01

    Thinning of the Earth's lithosphere by heat advected to its base is a possible mechanism for continental rifting and continental and oceanic mid-plate volcanism. It might also account for continental rifting-like processes and volcanism on Venus and Mars. Earth's continental lithosphere can be thinned to the crust in a few tens of million years by heat advected at a rate of 5 to 10 times the normal basal heat flux. This much heat is easily carried to the lithosphere by mantle plumes. The continent is not required to rest over the mantle hot spot but may move at tens of millimeters per year. Because of the constant level of crustal radioactive heat production, the ratio of the final to the initial surface heat flow increases much less than the ratio of the final to initial basal heat flow. For large increases in asthenospheric heat flow, the lithosphere is almost thinned to the crust before any significant change in surface heat flow occurs. Uplift due to thermal expansion upon thinning is a few kilometers. The oceanic lithosphere can be thinned to the crust in less than 10 million years if the heat advection is at a rate around 5 or more times the basal heat flow into 100 Ma old lithosphere. Uplift upon thinning can compensate the subsidence of spreading and cooling lithosphere.

  7. Comparison of academic performance of twins and singletons in adolescence

    DEFF Research Database (Denmark)

    Christensen, Kaare; Petersen, Inge; Skytthe, Axel

    2006-01-01

    OBJECTIVES: To determine whether twins in recent cohorts show similar academic performance in adolescence to singletons and to test the effect of birth weight on academic performance in twins and singletons. DESIGN: Follow-up study. SETTING: Denmark. PARTICIPANTS: All twins (n=3411) and a 5% random...... increase in birth weight. CONCLUSIONS: Although older cohorts of twins have been found to have lower mean IQ scores than singletons, twins in recent Danish cohorts show similar academic performance in adolescence to that of singletons. Birth weight has a minimal effect on academic performance in recent...

  8. Pregnancy outcome in singleton term breeches from a referral ...

    African Journals Online (AJOL)

    Objective: To compare the pregnancy outcome in women with singleton breech presentation at term delivered by caesarean section (CS) and vaginal breech delivery. Design: A retrospective study. Setting: Abha Maternity hospital, Saudi Arabia. Material and Methods: 573 women with singleton breech presentation at term ...

  9. Role of Frontal Cortex in Attentional Capture by Singleton Distractors

    Science.gov (United States)

    de Fockert, Jan W.; Theeuwes, Jan

    2012-01-01

    The role of frontal cortex in selective attention to visual distractors was examined in an attentional capture task in which participants searched for a unique shape in the presence or absence of an additional colour singleton distractor. The presence of the additional singleton was associated with slower behavioural responses to the shape target,…

  10. Attentional control during visual search: The effect of irrelevant singletons

    NARCIS (Netherlands)

    Theeuwes, J.; Burger, R.

    1998-01-01

    Four experiments investigated whether a highly salient color singleton can be ignored during serial search. Observers searched for a target letter among nontarget letters and were instructed to ignore an irrelevant, highly salient color singleton that was either compatible or incompatible with the

  11. Coupled Heat and Fluid Flow Modeling of the Earth's Largest Zinc Ore Deposit at Red Dog, Alaska: Implications for Structurally-Focused, Free Convection in Submarine Sedimentary Basins

    Science.gov (United States)

    Garven, G.; Dumoulin, J. A.; Bradley, D. A.; Young, L. E.; Kelley, K. D.; Leach, D. L.

    2002-12-01

    Crustal heat flow can provide a strong mechanism for driving groundwater flow, particularly in submarine basins where other mechanisms for driving pore fluid flow such as topography, compaction and crustal deformation are too weak or too slow to have a significant effect on disturbing conductive heat flow. Fault zones appear to play a crucial role in focusing fluid migration in basins, as inferred in ancient rocks by many examples of hydrothermal deposits of sediment-hosted ores worldwide. Many rift-hosted deposits of lead, zinc, and barite ore appear to have formed at or near the seafloor by focused venting of hot basinal fluids and modified seawater, although the geophysical nature of these systems is not so well known. For example, the upper Kuna Formation, a finely laminated, black, organic-rich siliceous mudstone and shale in the Western Brooks Range of northwest Alaska, is host to the largest resources of zinc yet discovered in the Earth's crust, containing ore reserves in excess of 175 Mt averaging about 16% Zn and 5% Pb. Although situated today in a highly-deformed series of structural allocthonous plates thrusted during the Jurassic to Cretaceous Brookian Orogeny, the stratiform ores are thought to have formed much earlier in the anoxic, mud-rich Carboniferous-age Kuna Basin when adjacent carbonate platforms were drowned by rifting and tectonic subsidence. Fluid inclusion studies of ore-stage sphalerite and gangue minerals indicate sub-seafloor mineralization temperatures less than 200oC and most likely between 120 to 150 oC, during a period of sediment diagenesis and extensional faulting. We have constructed fully-coupled numerical models of heat and fluid flow to test hydrologic theories for free convection, submarine venting and subsequent ore formation, as constrained by paleoheat flow and petrologic observations. A finite element grid was designed and adapted for a cross section of the Kuna Basin, geologically restored to latest Mississippian time

  12. Vanishing twin syndrome among ART singletons and pregnancy outcomes.

    Science.gov (United States)

    Magnus, Maria C; Ghaderi, Sara; Morken, Nils-Halvdan; Magnus, Per; Bente Romundstad, Liv; Skjærven, Rolv; Wilcox, Allen J; Eldevik Håberg, Siri

    2017-11-01

    Among babies born by ART, do singleton survivors of a vanishing twin have lower birth weight than other singletons? Vanishing twin syndrome (VTS) was associated with lower birth weight among ART singletons; a sibship analysis indicated that the association was not confounded by maternal characteristics that remain stable between deliveries. Previous studies indicate that ART singletons with VTS have increased risk of adverse pregnancy outcomes, compared with other ART singletons. The potential contribution of unmeasured maternal background characteristics has been unclear. This was a Norwegian population-based registry study, including 17 368 mothers with 20 410 ART singleton deliveries between January 1984 and December 2013. The study population included 17 291 ART singletons without VTS, 638 ART singletons with VTS and 2418 ART singletons with uncertain vanishing twin status. We estimated differences in birth weight and gestational age comparing ART singletons with VTS first to all ART singletons without VTS, and subsequently to their ART siblings without VTS, using random- and fixed-effects linear regression, respectively. The corresponding comparisons for the associations with preterm birth and small for gestational age (SGA) were conducted using random-and fixed-effects logistic regression. The sibling analysis of preterm birth included 587 discordant siblings, while the sibling analysis of SGA included 674 discordant siblings. ART singletons with VTS had lower birth weight when compared to all ART singletons without VTS, with an adjusted mean difference (95% CI) of -116 g (-165, -67). When we compared ART singletons with VTS to their ART singletons sibling without VTS, the adjusted mean difference was -112 g (-209, -15). ART singletons with VTS also had increased risk of being born SGA, with an adjusted odds ratio (OR) (95% CI) of 1.48 (1.07, 2.03) compared to all ART singletons without VTS, and 2.79 (1.12, 6.91) in the sibship analyses. ART singletons with

  13. The impact of cloud inhomogeneities on the Earth radiation budget: the 14 October 1989 I.C.E. convective cloud case study

    Directory of Open Access Journals (Sweden)

    F. Parol

    1994-01-01

    Full Text Available Through their multiple interactions with radiation, clouds have an important impact on the climate. Nonetheless, the simulation of clouds in climate models is still coarse. The present evolution of modeling tends to a more realistic representation of the liquid water content; thus the problem of its subgrid scale distribution is crucial. For a convective cloud field observed during ICE 89, Landsat TM data (resolution: 30m have been analyzed in order to quantify the respective influences of both the horizontal distribution of liquid water content and cloud shape on the Earth radiation budget. The cloud field was found to be rather well-represented by a stochastic distribution of hemi-ellipsoidal clouds whose horizontal aspect ratio is close to 2 and whose vertical aspect ratio decreases as the cloud cell area increases. For that particular cloud field, neglecting the influence of the cloud shape leads to an over-estimate of the outgoing longwave flux; in the shortwave, it leads to an over-estimate of the reflected flux for high solar elevations but strongly depends on cloud cell orientations for low elevations. On the other hand, neglecting the influence of cloud size distribution leads to systematic over-estimate of their impact on the shortwave radiation whereas the effect is close to zero in the thermal range. The overall effect of the heterogeneities is estimated to be of the order of 10 W m-2 for the conditions of that Landsat picture (solar zenith angle 65°, cloud cover 70%; it might reach 40 W m-2 for an overhead sun and overcast cloud conditions.

  14. The impact of cloud inhomogeneities on the Earth radiation budget: the 14 October 1989 I.C.E. convective cloud case study

    Directory of Open Access Journals (Sweden)

    F. Parol

    Full Text Available Through their multiple interactions with radiation, clouds have an important impact on the climate. Nonetheless, the simulation of clouds in climate models is still coarse. The present evolution of modeling tends to a more realistic representation of the liquid water content; thus the problem of its subgrid scale distribution is crucial. For a convective cloud field observed during ICE 89, Landsat TM data (resolution: 30m have been analyzed in order to quantify the respective influences of both the horizontal distribution of liquid water content and cloud shape on the Earth radiation budget. The cloud field was found to be rather well-represented by a stochastic distribution of hemi-ellipsoidal clouds whose horizontal aspect ratio is close to 2 and whose vertical aspect ratio decreases as the cloud cell area increases. For that particular cloud field, neglecting the influence of the cloud shape leads to an over-estimate of the outgoing longwave flux; in the shortwave, it leads to an over-estimate of the reflected flux for high solar elevations but strongly depends on cloud cell orientations for low elevations. On the other hand, neglecting the influence of cloud size distribution leads to systematic over-estimate of their impact on the shortwave radiation whereas the effect is close to zero in the thermal range. The overall effect of the heterogeneities is estimated to be of the order of 10 W m-2 for the conditions of that Landsat picture (solar zenith angle 65°, cloud cover 70%; it might reach 40 W m-2 for an overhead sun and overcast cloud conditions.

  15. Earth

    CERN Document Server

    Carter, Jason

    2017-01-01

    This curriculum-based, easy-to-follow book teaches young readers about Earth as one of the eight planets in our solar system in astronomical terms. With accessible text, it provides the fundamental information any student needs to begin their studies in astronomy, such as how Earth spins and revolves around the Sun, why it's uniquely suitable for life, its physical features, atmosphere, biosphere, moon, its past, future, and more. To enhance the learning experience, many of the images come directly from NASA. This straightforward title offers the fundamental information any student needs to sp

  16. The interaction of a magnetic cloud with the Earth: Ionospheric convection in the Northern and Southern Hemispheres for a wide range of quasi-steady interplanetary magnetic field conditions

    International Nuclear Information System (INIS)

    Freeman, M.P.; Farrugia, C.J.; Burlaga, L.F.; Lepping, R.P.; Hairston, M.R.; Greenspan, M.E.; Ruohoniemi, J.M.

    1993-01-01

    This is the second of three papers which study a large interplanetary magnetic cloud, and its interaction with the earth's magnetosphere. Here the authors study flows within the ionosphere during the passage of the magnetic cloud on Jan 13-15, 1988. This is the first study of ionospheric convections during prolonged periods of stable and different IMF orientations, which result from the stable, but spatially varying field structure within the magnetic cloud. Data from IMP-8 and DMSP-F8 are analyzed for this work. This observation gave information on ionospheric responses to greater than 10 hour period of northward and southward IMF, with a gradual change from one to the other. Issues studied included strengths of peak flows for north and south IMF; changes in cross polar cap potential with IMF B z ; types and variations of convective patterns vs IMF; variations in size of the polar cap; etc

  17. Capture by colour: evidence for dimension-specific singleton capture.

    Science.gov (United States)

    Harris, Anthony M; Becker, Stefanie I; Remington, Roger W

    2015-10-01

    Previous work on attentional capture has shown the attentional system to be quite flexible in the stimulus properties it can be set to respond to. Several different attentional "modes" have been identified. Feature search mode allows attention to be set for specific features of a target (e.g., red). Singleton detection mode sets attention to respond to any discrepant item ("singleton") in the display. Relational search sets attention for the relative properties of the target in relation to the distractors (e.g., redder, larger). Recently, a new attentional mode was proposed that sets attention to respond to any singleton within a particular feature dimension (e.g., colour; Folk & Anderson, 2010). We tested this proposal against the predictions of previously established attentional modes. In a spatial cueing paradigm, participants searched for a colour target that was randomly either red or green. The nature of the attentional control setting was probed by presenting an irrelevant singleton cue prior to the target display and assessing whether it attracted attention. In all experiments, the cues were red, green, blue, or a white stimulus rapidly rotated (motion cue). The results of three experiments support the existence of a "colour singleton set," finding that all colour cues captured attention strongly, while motion cues captured attention only weakly or not at all. Notably, we also found that capture by motion cues in search for colour targets was moderated by their frequency; rare motion cues captured attention (weakly), while frequent motion cues did not.

  18. Heat convection

    Energy Technology Data Exchange (ETDEWEB)

    Jiji, L.M. [City Univ. of New York, NY (United States). Dept. of Mechanical Engineering

    2006-07-01

    Professor Jiji's broad teaching experience lead him to select the topics for this book to provide a firm foundation for convection heat transfer with emphasis on fundamentals, physical phenomena, and mathematical modelling of a wide range of engineering applications. Reflecting recent developments, this textbook is the first to include an introduction to the challenging topic of microchannels. The strong pedagogic potential of Heat Convection is enhanced by the following ancillary materials: (1) Power Point lectures, (2) Problem Solutions, (3) Homework Facilitator, and, (4) Summary of Sections and Chapters. (orig.)

  19. Heat Convection

    Science.gov (United States)

    Jiji, Latif M.

    Professor Jiji's broad teaching experience lead him to select the topics for this book to provide a firm foundation for convection heat transfer with emphasis on fundamentals, physical phenomena, and mathematical modelling of a wide range of engineering applications. Reflecting recent developments, this textbook is the first to include an introduction to the challenging topic of microchannels. The strong pedagogic potential of Heat Convection is enhanced by the follow ing ancillary materials: (1) Power Point lectures, (2) Problem Solutions, (3) Homework Facilitator, and, (4) Summary of Sections and Chapters.

  20. Congenital Malformations in Singleton Infants Conceived by Assisted Reproductive Technologies and Singleton Infants by Natural Conception in Tehran, Iran

    Directory of Open Access Journals (Sweden)

    Ramin Mozafari Kermani

    2017-10-01

    Full Text Available Background: Multiple pregnancies occur more frequently in assisted reproductive technology (ART compared to normal conception (NC. It is known that the risk of congenital malformations in a multiple pregnancy are higher than single pregnancy. The aim of this study is to compare congenital malformations in singleton infants conceived by ART to singleton infants conceived naturally. Materials and Methods: In this historical cohort study, we performed a historical cohort study of major congenital malformations (MCM in 820 singleton births from January 2012 to December 2014. The data for this analysis were derived from Tehran’s ART linked data file. The risk of congenital malformations was compared in 164 ART infants and 656 NC infants. We performed multiple logistic regression analyses for the independent association of ART on each outcome. Results: We found 40 infants with MCM 29 (4.4% NC infants and 14 (8.3% ART infants. In comparison with NC infants, ART infants had a significant 2-fold increased risk of MCM (P=0.046. After adjusting individually for maternal age, infant gender, prior stillbirth, mother’s history of spontaneous abortion, and type of delivery, we did not find any difference in risk. In this study the majority (95.1% of all infants were normal but 4.9% of infants had at least one MCM. We found a difference in risk of MCMs between in vitro fertilization (IVF and intracytoplasmic sperm injection (ICSI. We excluded the possible role of genotype and other unknown factors in causing more malformations in ART infants. Conclusion: This study reported a higher risk of MCMs in ART singleton infants than in NC singleton infants. Congenital heart disease, developmental dysplasia of the hip (DDH, and urogenital malformations were the most reported major malformations in singleton ART infants according to organ and system classification.

  1. Internal Wave Generation by Convection

    Science.gov (United States)

    Lecoanet, Daniel Michael

    In nature, it is not unusual to find stably stratified fluid adjacent to convectively unstable fluid. This can occur in the Earth's atmosphere, where the troposphere is convective and the stratosphere is stably stratified; in lakes, where surface solar heating can drive convection above stably stratified fresh water; in the oceans, where geothermal heating can drive convection near the ocean floor, but the water above is stably stratified due to salinity gradients; possible in the Earth's liquid core, where gradients in thermal conductivity and composition diffusivities maybe lead to different layers of stable or unstable liquid metal; and, in stars, as most stars contain at least one convective and at least one radiative (stably stratified) zone. Internal waves propagate in stably stratified fluids. The characterization of the internal waves generated by convection is an open problem in geophysical and astrophysical fluid dynamics. Internal waves can play a dynamically important role via nonlocal transport. Momentum transport by convectively excited internal waves is thought to generate the quasi-biennial oscillation of zonal wind in the equatorial stratosphere, an important physical phenomenon used to calibrate global climate models. Angular momentum transport by convectively excited internal waves may play a crucial role in setting the initial rotation rates of neutron stars. In the last year of life of a massive star, convectively excited internal waves may transport even energy to the surface layers to unbind them, launching a wind. In each of these cases, internal waves are able to transport some quantity--momentum, angular momentum, energy--across large, stable buoyancy gradients. Thus, internal waves represent an important, if unusual, transport mechanism. This thesis advances our understanding of internal wave generation by convection. Chapter 2 provides an underlying theoretical framework to study this problem. It describes a detailed calculation of the

  2. Singleton preterm births in Korle bu teaching hospital, Accra, Ghana ...

    African Journals Online (AJOL)

    Objective: To determine the singleton preterm birth rate, the relative proportions of the clinical categories of preterm births and to compare the outcomes in these categories. Setting: Department of Obstetrics & Gynaecol-ogy, Korle Bu Teaching Hospital. Participants: Preterm births from 1st July to 31st December 2003.

  3. The analysis of singletons in generalized birthday problems

    NARCIS (Netherlands)

    Koot, M.R.; Mandjes, M.R.H.

    2012-01-01

    This paper describes techniques to characterize the number of singletons in the setting of the generalized birthday problem, that is, the birthday problem in which the birthdays are non-uniformly distributed over the year. Approximations for the mean and variance presented which explicitly indicate

  4. The allocation of attention in displays with simultaneously presented singletons

    NARCIS (Netherlands)

    Akyürek, Elkan G; Schubö, Anna

    In an ERP experiment, we investigated whether a 'permanent salient distractor changes the deployment of attention to target and nontarget singletons. Observers searched for a color target in a search array that mainly consisted of black vertical lines, but also always contained a line in a

  5. Pregnancy outcome in singleton term breeches from a referral ...

    African Journals Online (AJOL)

    It is recommended that attention should be given to trainee obstetrician in selective external cephalic version at term and also the procedure of AVBD so as to reduce the caesarean section rate and also neonatal morbidity in term breeches in our community. Keywords: Pregnancy outcome, Singleton breech, Vaginal ...

  6. Study of Perineal Tears During Delivery of Singletons in Cephalic ...

    African Journals Online (AJOL)

    Study of Perineal Tears During Delivery of Singletons in Cephalic Presentation. E Nkwabong, L Kouam, GT Orock, MR Ekono, W Takang, KV Mve. Abstract. Background: Perineal lacerations are associated with short and long term maternal complications like perineal pain and superficial dyspareunia and must be prevented ...

  7. Prédiction des structures convectives terrestres

    OpenAIRE

    Bello , Léa

    2015-01-01

    Since its formation, the Earth is slowly cooling. The heat produced by the core and the radioactive decay in the mantle is evacuated toward the surface by convection. The evolving convective structures thereby created control a diversity of surface phenomena such as vertical motion of continents or sea level variation. The study presented here attempts to determine which convective structures can be predicted, to what extent and over what timescale. Because of the chaotic nature of convection...

  8. A simple 3-D numerical model of thermal convection in Earth's growing inner core: on the possibility of the formation of the degree-one structure with lateral viscosity variations

    Science.gov (United States)

    Yoshida, M.

    2015-12-01

    An east-west hemispherically asymmetric structure for Earth's inner core has been suggested by various seismological evidence, but its origin is not clearly understood. Here, to investigate the possibility of an "endogenic origin" for the degree-one thermal/mechanical structure of the inner core, I performed new numerical simulations of thermal convection in the growing inner core. A setup value that controls the viscosity contrast between the inner core boundary and the interior of the inner core, ΔηT, was taken as a free parameter. Results show that the degree-one structure only appeared for a limited range of ΔηT; such a scenario may be possible but is not considered probable for the real Earth. The degree-one structure may have been realized by an "exogenous factor" due to the planetary-scale thermal coupling among the lower mantle, the outer core, and the inner core, not by an endogenic factor due to the internal rheological heterogeneity.

  9. National Convective Weather Diagnostic

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Current convective hazards identified by the National Convective Weather Detection algorithm. The National Convective Weather Diagnostic (NCWD) is an automatically...

  10. Amnioreduction in the management of polyhydramnios complicating singleton pregnancies.

    Science.gov (United States)

    Dickinson, Jan Elizabeth; Tjioe, Yan Yan; Jude, Emily; Kirk, Daniel; Franke, Malcolm; Nathan, Elizabeth

    2014-10-01

    The purpose of this study was to evaluate the contribution of amnioreduction to the management of singleton pregnancies that are complicated by symptomatic polyhydramnios. Retrospective review of all singleton pregnancies that received at least 1 amnioreduction for polyhydramnios from 2000-2012 at a single obstetric unit that provides a statewide service. The indications, procedural techniques, and pregnancy outcomes were evaluated. One hundred thirty-eight women with polyhydramnios (maximal vertical pocket [MVP], ≥8 cm) had 271 amnioreduction procedures during the study period. The median gestation at the first drain was 31.4 weeks (interquartile range, 28.4-34 weeks) and a median of 1 procedure (interquartile range, 1-2 procedures) was performed per pregnancy. Sixty-three women (45.6%) required >1 amnioreduction. The median volume removed per pregnancy was 2100 mL (interquartile range, 1500-4260 mL). The median duration from the first amnioreduction until delivery was 26 days (interquartile range, 15-52.5 days). There was no significant association between gestation at delivery and the volume per procedure or total volume that was removed. Earlier gestation at first drain was associated positively with earlier gestations at delivery. In 4.1% of amnioreduction procedures (11/271 procedures), there was an unplanned preterm birth within 48 hours. The median gestation at delivery was 36.4 weeks (interquartile range, 34-38 weeks). The final diagnoses were gastrointestinal malformations (21%), idiopathic polyhydramnios (20.3%), chromosomal anomaly (15.2%), syndromic condition (13.7%), and neurologic condition (8%). Amnioreduction has a useful role in the management of polyhydramnios in singleton pregnancies. Complications are uncommon, and delivery typically occurs near term. Copyright © 2014 Elsevier Inc. All rights reserved.

  11. Convective heater

    Science.gov (United States)

    Thorogood, Robert M.

    1983-01-01

    A convective heater for heating fluids such as a coal slurry is constructed of a tube circuit arrangement which obtains an optimum temperature distribution to give a relatively constant slurry film temperature. The heater is constructed to divide the heating gas flow into two equal paths and the tube circuit for the slurry is arranged to provide a mixed flow configuration whereby the slurry passes through the two heating gas paths in successive co-current, counter-current and co-current flow relative to the heating gas flow. This arrangement permits the utilization of minimum surface area for a given maximum film temperature of the slurry consistent with the prevention of coke formation.

  12. Sonographic measurement of fetal thymus size in uncomplicated singleton pregnancies.

    Science.gov (United States)

    Tangshewinsirikul, Chayada; Panburana, Panyu

    2017-03-04

    To establish sonographic reference ranges of the normal fetal thymus size between 17 and 38 weeks of gestational age (GA). The study was conducted between April 1 and December 31, 2013. Low-risk singleton pregnancies without obstetrical and medical complications at the GAs between 17 and 38 weeks were recruited for thymus measurement. The fetal thymus was identified on transabdominal sonography at the three-vessel view. Maximal transverse diameter, perimeter, and thymus/thoracic ratio were measured. The best-fit models in predicting thymic dimensions as a function of GA and biparietal diameter (BPD) were determined using regression analysis, and percentile charts for predicting thymic dimensions were constructed. A total of 296 singleton pregnancies were recruited in this study. Maximal transverse diameter, perimeter, and thymus/thoracic ratio increased throughout pregnancy. The regression equation for maximal transverse diameter of the thymus as a function of GA was as follows: Predicted mean thymus diameter (mm) = -25.904 + 2.476 × GA - 0.019 × GA 2 (r = 0.915; p thymus diameter (mm) = 1.428 + 0.044 × GA (r = 0.017; p < 0.001). Sonographic reference ranges of the normal fetal thymic dimensions between 17 and 38 weeks of GA have been established. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 45:150-159, 2017. © 2016 Wiley Periodicals, Inc.

  13. Hypercoiling of the umbilical cord in uncomplicated singleton pregnancies.

    Science.gov (United States)

    Ma'ayeh, Marwan; McClennen, Evan; Chamchad, Dmitri; Geary, Michael; Brest, Norman; Gerson, Andrew

    2017-06-26

    The umbilical coiling index (UCI) is a measure of the number of coils in the umbilical cord in relation to its length. Hypercoiled cords with a UCI of >0.3 coils/cm have been associated with adverse fetal and neonatal outcomes. The primary aim is to determine the accuracy of UCI measured on second trimester ultrasound in predicting UCI at birth. The secondary outcome is to investigate the association between hypercoiling of the umbilical cord on prenatal ultrasound and adverse maternal, fetal and neonatal outcomes. This was a prospective cohort study of uncomplicated singleton pregnancies. Seventy two patients were included in the study. UCI was measured in the second trimester ultrasound, and compared to UCI measured postnatally. Outcomes of patients with hypercoiled cords on ultrasound were compared to outcomes of patients with normocoiled cords. Our results failed to show a strong correlation between the UCI determined with ultrasound, and the UCI determined with examination of the umbilical cord after delivery. We also did not demonstrate that measurement of the UCI on second trimester ultrasound is able to predict adverse maternal, fetal or neonatal outcomes. This study suggests that measurement of the umbilical coiling index should not be part of routine second trimester sonography in patients with uncomplicated singleton pregnancies, with no other medical or surgical comorbidities.

  14. Free convective boundary layers in variable-viscosity fluids by the method of local nonsimilarity: application to plumes in the earth's mantle

    International Nuclear Information System (INIS)

    Quareni, F.; Yuen, D.A.; Eby, H.E.

    1983-01-01

    The effects due to departures from local similarity in steady-state boundary layers ascending through a fluid with strongly variable viscosity are examined with the local-nonsimilarity method. Both the absolute temperature and the hydrostatic pressure appear in the argument of an exponential in the viscosity function. The fluid-dynamical system studied here is that which characterizes plume structures in the Earth's mantle. By means of an iterative approach, two successive nonlinear boundary value problems are solved simultaneously and the errors incurred in the locally similar solutions are then assessed from a comparison between the first (locally similar) and the second level of a system of truncated equations. Three different sources of nonsimilarity have been considered: 1) localized radiogenic hearting within the plume, 2) ambient thermal stratification, 3) pressure dependence of mantle rheology. Of particular interest is an appraisal of the degree of accuracy of the locally similar solutions as a function of viscosity contrast within the boundary layer. For the range of viscosity contrast examined, up to 10 8 , the velocity and temperature fields between the first- and second-level solutions differ at most by 20 to 30%, for the rheological parameter values relevant to the Earth's mantle

  15. The Continental Drift Convection Cell

    Science.gov (United States)

    Whitehead, J. A.; Behn, M. D.

    2014-12-01

    Continents on Earth periodically assemble to form supercontinents, and then break up again into smaller continental blocks (the Wilson Cycle). Highly developed but realistic numerical models cannot resolve if continents respond passively to mantle convection or whether they modulate flow. Our simplified numerical model addresses this problem: A thermally insulating continent floats on a stress-free surface for infinite Prandtl number cellular convection with constant material properties in a chamber 8 times longer than its depth. The continent moves back and forth across the chamber driven by a "continental drift convection cell" of a form not previously described. Subduction exists at the upstream end with cold slabs dipping at an angle beneath the moving continent. Fluid moves with the continent in the upper region of this cell with return flow near the bottom. Many continent/subduction regions on Earth have these features. The drifting cell enhances vertical heat transport by approximately 30% compared to a fixed continent, especially at the core-mantle boundary, and significantly decreases lateral mantle temperature differences. However, continent drift or fixity has smaller effects on profiles of horizontally averaged temperature. Although calculations are done at Rayleigh numbers lower than expected for Earth's mantle (2x105 and 106), the drift speed extrapolates to reasonable Wilson Cycle speeds for larger Ra.

  16. Overweight in Singletons Compared to Children with Siblings

    DEFF Research Database (Denmark)

    Hunsberger, Monica; Formisano, Annarita; Reisch, Lucia

    2012-01-01

    The aim of this study was to compare the prevalence of overweight in only children to those with siblings and to explore potential behavioral mediating factors. This study relies upon cross-sectional data collected at survey centers in eight European countries participating in Identification....... The three southernmost countries have over threefold risk of overweight, dominated by Italy, compared with the north-central countries, which is not explained by the prevalence of singleton children. The excess risk of overweight among children without siblings was robustly observed even when considering...... and prevention of Dietary- and lifestyle-induced health EFfects In Children and infantS (IDEFICS). The present analysis is based on measured anthropometry and parent or guardian-reported socio-demographic characteristics. Subjects include 12 720 children aged 2–9 years for whom number of siblings was known...

  17. Perinatal outcomes in 6,338 singletons born after intrauterine insemination in Denmark, 2007 to 2012

    DEFF Research Database (Denmark)

    Malchau, Sara Sofia; Loft, Anne; Henningsen, Anna-Karina Aaris

    2014-01-01

    OBJECTIVE: To study perinatal outcomes in singletons born after intrauterine insemination (IUI) compared with children born after in vitro fertilization (IVF), intracytoplasmic sperm injection, and spontaneous conception (SC), and to assess predictors of poor outcome in singletons born after IUI......, exploring the effect of ovarian stimulation. DESIGN: National cohort study, 2007-2012. SETTING: Danish national registries. PATIENT(S): Four thousand two hundred twenty-eight singletons born after insemination with partner semen (IUI-H) and 1,881 singletons born after insemination with donor semen...

  18. Cord around neck in singleton term pregnancies and its outcome

    International Nuclear Information System (INIS)

    Sajjad, R.; Mustafa, N.

    2014-01-01

    To enlist the complications with nuchal cord in singleton term pregnancies and to determine maternal and fetal outcome in singleton term pregnancies. Design: Descriptive study. Place and duration of study: The study was carried out at Gynaecology and Obstetric department Combined Military Hospital Quetta from Nov 2007 to May 2008. Patients and methods: One hundred women irrespective of parity with healthy, singleton term pregnancy and cephalic presentation, labouring or not labouring, were selected from outpatient department. A total of 41 patients were booked with Doppler ultrasound done in antenatal period. Other 59 were poorly booked and diagnosed with cord around neck by clinical criteria e.g. high head at term, fetal distress, meconium discharge, slow progress in labour leading to prolonged labour. All patients signed well informed written proforma regarding study and its outcome. Vigilant feto maternal monitoring was done during labour. All events during labour were mentioned in proformas which were attached with patients case notes. Data was interperated in term of frequency and percentages. Results: Complications with cord around neck found were still birth 3%, fetal distress 15%, intrauterine death 1%. Prolonged labour was seen in 14%, Meconium discharge in 5%, and high presenting part was found in 11% of cases. Maternal outcome were elective caesarean section in 6%, emergency caesarean-section in 32%, spontaneous vaginal delivery in 54% and instrumental vaginal delivery in 8% of the cases. Different fetal outcomes seen were intrauterine death, stillbirth in 1%, and 3% patients respectively. Regarding neonatal outcome, 31% stayed in neonatal intensive care unit (NICU) for less than 48 hours, 69% stayed in NICU for more than 48 hours out of which 4% had early neonatal deaths (ENND). Fifty nine percent patients detected and suspected during labour were with, high head, slow progress in labour, decreased fetal movements, intra partum fetal distress, meconium

  19. Tropical deep convective cloud morphology

    Science.gov (United States)

    Igel, Matthew R.

    A cloud-object partitioning algorithm is developed. It takes contiguous CloudSat cloudy regions and identifies various length scales of deep convective clouds from a tropical, oceanic subset of data. The methodology identifies a level above which anvil characteristics become important by analyzing the cloud object shape. Below this level in what is termed the pedestal region, convective cores are identified based on reflectivity maxima. Identifying these regions allows for the assessment of length scales of the anvil and pedestal of the deep convective clouds. Cloud objects are also appended with certain environmental quantities from the ECMWF reanalysis. Simple geospatial and temporal assessments show that the cloud object technique agrees with standard observations of local frequency of deep-convective cloudiness. Additionally, the nature of cloud volume scale populations is investigated. Deep convection is seen to exhibit power-law scaling. It is suggested that this scaling has implications for the continuous, scale invariant, and random nature of the physics controlling tropical deep convection and therefore on the potentially unphysical nature of contemporary convective parameterizations. Deep-convective clouds over tropical oceans play important roles in Earth's climate system. The response of tropical, deep convective clouds to sea surface temperatures (SSTs) is investigated using this new data set. Several previously proposed feedbacks are examined: the FAT hypothesis, the Iris hypothesis, and the Thermostat hypothesis. When the data are analyzed per cloud object, each hypothesis is broadly found to correctly predict cloud behavior in nature, although it appears that the FAT hypothesis needs a slight modification to allow for cooling cloud top temperatures with increasing SSTs. A new response that shows that the base temperature of deep convective anvils remains approximately constant with increasing SSTs is introduced. These cloud-climate feedbacks are

  20. Convective transfers; Transferts convectifs

    Energy Technology Data Exchange (ETDEWEB)

    Accary, G.; Raspo, I.; Bontoux, P. [Aix-Marseille-3 Univ. Paul Cezanne, CNRS, Lab. MSNM-GP UMR 6181, 13 - Marseille (France); Zappoli, B. [Centre National d' Etudes Spatiales (CNES), 31 - Toulouse (France); Polidori, G.; Fohanno, S. [Laboratoire de Thermomecanique, 51 - Reims (France); Hirata, S.C.; Goyeau, B.; Gobin, D. [Paris-6 et Paris-11 Univ., FAST-UMR CNRS 7608, 91 - Orsay (France); Cotta, R.M. [UFRJ/LTTC/PEM/EE/COPPE, Rio de Janeiro (Brazil); Perrin, L.; Reulet, P.; Micheli, F.; Millan, P. [Office National d' Etudes et de Recherches Aerospatiales (ONERA), 31 - Toulouse (France); Menard, V. [France Telecom R and D, 22 - Lannion (France); Benkhelifa, A.; Penot, F. [Ecole Nationale Superieure de Mecanique et d' Aerotechnique (ENSMA), Lab. d' Etudes Thermiques, UMR CNRS 6608, 86 - Poitiers (France); Ng Wing Tin, M.; Haquet, J.F.; Journeau, C. [CEA Cadarache (DEN/DTN/STRI/LMA), Lab. d' Essais pour la Maitrise des Accidents Graves, 13 - Saint-Paul-lez-Durance (France); Naffouti, T.; Hammani, M.; Ben Maad, R. [Faculte des Sciences de Tunis, Lab. d' Energetique et des Transferts Thermique et Massique, Dept. de Physique, Tunis (Tunisia); Zinoubi, J. [Institut Preparatoire aux Etudes d' Ingenieurs de Nabeul (Tunisia); Menard, V.; Le Masson, S.; Nortershauser, D. [France Telecom R and D, 22 - Lannion (France); Stitou, A.; Perrin, L.; Millan, P. [ONERA, 31 - Toulouse (France)

    2005-07-01

    This session about convective transfers gathers 31 articles dealing with: numerical study of the hydrodynamic stability of a bottom heated supercritical fluid layer; establishment of laminar-turbulent transition criteria of free convection dynamic and thermal boundary layers; heat transfer changes in free convection by mechanical and thermal disturbances; natural convection stability in partially porous horizontal layers; experimental characterization of the dynamic and thermal aspects of a natural convection flow inside a confined space; determination of transitions towards non-stationary natural convection inside a differentially heated inclined cavity; interface temperatures for the convection of fluids with variable viscosity; influence of the height of a vertical cylinder on the flow resulting from a plume-thermosyphon interaction; simultaneous measurement of dynamic and thermal fields by thermo-chromic liquid crystals in natural convection; numerical simulation of turbulent natural convection flows inside a heated room; numerical and experimental study of mixed convection heat transfer inside an axisymmetrical network; analysis of laminar flow instabilities in assisted mixed convection; entropy generation in mixed convection; thermal and mass convection in non-stationary regime inside a ventilated cavity; study of a low Reynolds number mixed convection flow; numerical study of a convective flow inside a rotating annular cavity; study of the dynamical behaviour of a transient mixed convection flow inside a thick vertical duct; internal laminar convection: selection criteria for the identification of natural, mixed or forced regimes; turbulent flow and convection heat transfer inside a channel with corrugated walls; study of the impact of an axisymmetrical jet on a concave wall; modeling of volume irreversibilities of turbulent forced convection; numerical study of forced convection irreversibilities around a network of cylindrical tubes; estimation of the

  1. Driving forces: Slab subduction and mantle convection

    Science.gov (United States)

    Hager, Bradford H.

    1988-01-01

    Mantle convection is the mechanism ultimately responsible for most geological activity at Earth's surface. To zeroth order, the lithosphere is the cold outer thermal boundary layer of the convecting mantle. Subduction of cold dense lithosphere provides tha major source of negative buoyancy driving mantle convection and, hence, surface tectonics. There are, however, importnat differences between plate tectonics and the more familiar convecting systems observed in the laboratory. Most important, the temperature dependence of the effective viscosity of mantle rocks makes the thermal boundary layer mechanically strong, leading to nearly rigid plates. This strength stabilizes the cold boundary layer against small amplitude perturbations and allows it to store substantial gravitational potential energy. Paradoxically, through going faults at subduction zones make the lithosphere there locally weak, allowing rapid convergence, unlike what is observed in laboratory experiments using fluids with temperature dependent viscosities. This bimodal strength distribution of the lithosphere distinguishes plate tectonics from simple convection experiments. In addition, Earth has a buoyant, relatively weak layer (the crust) occupying the upper part of the thermal boundary layer. Phase changes lead to extra sources of heat and bouyancy. These phenomena lead to observed richness of behavior of the plate tectonic style of mantle convection.

  2. National Convective Weather Forecast

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NCWF is an automatically generated depiction of: (1) current convection and (2) extrapolated signficant current convection. It is a supplement to, but does NOT...

  3. Recurrence risk of low Apgar score among term singletons: a population-based cohort study

    NARCIS (Netherlands)

    Ensing, Sabine; Schaaf, Jelle M.; Abu-Hanna, Ameen; Mol, Ben W. J.; Ravelli, Anita C. J.

    2014-01-01

    To examine the risk of recurrence of low Apgar score in a subsequent term singleton pregnancy. Population-based cohort study. The Netherlands. A total of 190,725 women with two subsequent singleton term live births between 1999 and 2007. We calculated the recurrence risk of low Apgar score after

  4. Monozygotic Triplets and a Singleton After ICSI and Day 3 Transfer of Two Embryos

    Directory of Open Access Journals (Sweden)

    Singpetch Suksompong

    2017-07-01

    Full Text Available Monozygotic triplets are a rare condition to occur naturally or even in assisted reproductive technologies. In this report, we present a case of monozygotic triplets with a singleton pregnancy following embryo transfer of 2 embryos. To our knowledge, this is the first published case of one singleton and monozygotic triplets after ICSI and transfer of two day 3 embyos in Thailand.

  5. Recurrence risk of preterm birth in subsequent twin pregnancy after preterm singleton delivery

    NARCIS (Netherlands)

    Schaaf, J. M.; Hof, M. H. P.; Mol, B. W. J.; Abu-Hanna, A.; Ravelli, A. C. J.

    2012-01-01

    Please cite this paper as: Schaaf J, Hof M, Mol B, Abu-Hanna A, Ravelli A. Recurrence risk of preterm birth in subsequent twin pregnancy after preterm singleton delivery.BJOG 2012;119:16241629. Objective To determine the risk of preterm birth in a subsequent twin pregnancy after previous singleton

  6. Recurrence risk of preterm birth in subsequent singleton pregnancy after preterm twin delivery

    NARCIS (Netherlands)

    Schaaf, Jelle M.; Hof, Michel H. P.; Mol, Ben Willem J.; Abu-Hanna, Ameen; Ravelli, Anita C. J.

    2012-01-01

    OBJECTIVE: The purpose of this study was to investigate the recurrence risk of preterm birth ( <37 weeks' gestation) in a subsequent singleton pregnancy after a previous nulliparous preterm twin delivery. STUDY DESIGN: We included 1957 women who delivered a twin gestation and a subsequent singleton

  7. Earth materials and earth dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, K; Shankland, T. [and others

    2000-11-01

    In the project ''Earth Materials and Earth Dynamics'' we linked fundamental and exploratory, experimental, theoretical, and computational research programs to shed light on the current and past states of the dynamic Earth. Our objective was to combine different geological, geochemical, geophysical, and materials science analyses with numerical techniques to illuminate active processes in the Earth. These processes include fluid-rock interactions that form and modify the lithosphere, non-linear wave attenuations in rocks that drive plate tectonics and perturb the earth's surface, dynamic recrystallization of olivine that deforms the upper mantle, development of texture in high-pressure olivine polymorphs that create anisotropic velocity regions in the convecting upper mantle and transition zone, and the intense chemical reactions between the mantle and core. We measured physical properties such as texture and nonlinear elasticity, equation of states at simultaneous pressures and temperatures, magnetic spins and bonding, chemical permeability, and thermal-chemical feedback to better characterize earth materials. We artificially generated seismic waves, numerically modeled fluid flow and transport in rock systems and modified polycrystal plasticity theory to interpret measured physical properties and integrate them into our understanding of the Earth. This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL).

  8. Modes of convection in the magnetotail

    International Nuclear Information System (INIS)

    Baumjohann, Wolfgang

    2002-01-01

    The flow of plasma in the Earth's magnetotail cannot reach a steady state, since adiabatic convection would lead to exceedingly high pressure of the associated magnetic flux tubes closer to the Earth, the so-called pressure catastrophe. The natural way to avoid the pressure catastrophe is to significantly reduce the flux tube volume by reconnection, and observations show a near-Earth reconnection line typically around 20-25 Earth radii down tail. Earthward flows from this reconnection line are rather bursty and typically seen outside of 10 Earth radii. At this point they are strongly braked by the here dominant dipolar magnetic field. The pressure gradients piled up by the flow lead to the substorm current wedge, and possibly other substorm phenomena observed in the Earth's ionosphere. When more and more flux tubes are piled up, the dipolarization front moves tailward and finally shuts off near-Earth reconnection

  9. Ovarian hyperstimulation syndrome in a spontaneous singleton pregnancy.

    Science.gov (United States)

    Cabar, Fábio Roberto

    2016-05-24

    The ovarian hyperstimulation syndrome is the combination of increased ovarian volume, due to the presence of multiple cysts and vascular hyperpermeability, with subsequent hypovolemia and hemoconcentration. We report a case of spontaneous syndrome in a singleton pregnancy. This was a spontaneous pregnancy with 12 weeks of gestational age. The pregnancy was uneventful until 11 weeks of gestational age. After that, the pregnant woman complained of progressive abdominal distention associated with abdominal discomfort. She did not report other symptoms. In the first trimester, a routine ultrasonography showed enlarged ovaries, multiples cysts and ascites. Upon admission, the patient was hemodynamically stable, her serum β-hCG was 24,487mIU/mL, thyroid-stimulating hormone was 2.2µUI/mL and free T4 was 1.8ng/dL. All results were within normal parameters. However, levels of estradiol were high (10,562pg/mL). During hospitalization, she received albumin, furosemide and prophylactic dose of enoxaparin. The patient was discharged on the sixth hospital day. RESUMO A síndrome de hiperestimulação ovariana é a combinação do aumento dos ovários, devido à presença de múltiplos cistos e de hiperpermeabilidade vascular, com subsequente hipovolemia e hemoconcentração. Relata-se um caso de síndrome espontânea em uma gestação única. Trata-se de gravidez espontânea com 12 semanas de idade gestacional. A gravidez ocorreu sem intercorrências até 11 semanas de idade gestacional. Após, a gestante passou a se queixar de distensão abdominal progressiva, associada com desconforto abdominal. A paciente não relatava outros sintomas. A ultrassonografia de rotina no primeiro trimestre mostrou ovários aumentados com múltiplos cistos e ascite. No momento da internação, a paciente apresentava-se hemodinamicamente estável, com β-hCG sérico de 24.487mUI/mL, hormônio estimulante da tireoide de 2,2µUI/m e T4 livre de 1,8ng/dL, ou seja, valores dentro dos par

  10. [Incidence of singleton macrosomia in Beijing and its risk factors].

    Science.gov (United States)

    Ren, J H; Wang, C; Wei, Y M; Yang, H X

    2016-06-25

    To evaluate the prevalence of macrosomia in Beijing in 2013 and identify its risk factors. Retrospective six months analysis of 14 188 full-term singleton pregnant women from 15 hospitals with different levels in Beijing in 2013. Each participant's demographic data and medical information were collected individually by questionnaires. Multiple logistic regression analysis was used to examine the associations between variables and the risk of macrosomia. (1)The total prevalence of macrosomia was 7.069% (1 003/14 188) in Beijing in 2013. (2)The prevalence varied between the 15 hospitals, the lowest was 5.36% (89/1 659), while the highest reached 8.80%(46/523). Furthermore, the incidence of macrosomia was 1.284 times (95% CI: 1.114- 1.480, P=0.001) higher in the second graded hospitals than that in the tertiary hospitals. (3) Multiple logistic regression analyses showed that risk factors for macrosomia were maternal height≥160 cm (adjusted OR=1.875, 95% CI: 1.559- 2.256), pre-pregnant body mass index (p-BMI) ≥24.0 kg/m(2) (24.0- 27.9 kg/m(2): adjusted OR=1.696, 95% CI: 1.426- 2.018; p-BMI≥28.0 kg/m(2): adjusted OR=2.393, 95% CI: 1.831- 3.127), gestational weight gain (GWG) ≥15.9 kg (adjusted OR=2.462, 95% CI: 2.125- 2.853), gravidity>1 (adjusted OR=1.408, 95% CI: 1.224- 1.620), gestational weeks≥40 (adjusted OR=2.007, 95%CI: 1.745-2.308) and gestational diabetes mellitus (adjusted OR=1.522, 95%CI: 1.298-1.784). GWG≥15.9 kg, p-BMI≥28.0 kg/m(2) and gestational weeks≥40 were three risk factors that had the strongest associations with macrosomia (all Pmacrosomia in hospitals with different levels is obvious different. Gestational weeks, p-BMI and GWG are three main controllable risk factors for macrosomia, thus should receive more attentions.

  11. Attenuation of ductus arteriosus intimal thickening in preterm sheep twins compared with singletons.

    Science.gov (United States)

    Ito, Satoko; Yokoyama, Utako; Saito, Junichi; Sato, Shinichi; Usuda, Haruo; Watanabe, Shimpei; Kitanishi, Ryuta; Miura, Yuichiro; Saito, Masatoshi; Hanita, Takushi; Matsuda, Tadashi; Ishikawa, Yoshihiro

    2017-11-01

    Preterm twins have a higher morbidity rate of patent ductus arteriosus (PDA) than do singletons. However, the effect of multiple births on maturation of the ductus arteriosus (DA) has not been reported. Because intimal thickening (IT) is required for DA anatomical closure, we examined IT development in the DA of preterm twins and singletons. Sheep DA tissues obtained from preterm fetuses were subjected to elastica van Gieson staining to evaluate IT. The total IT score in each DA was the sum of the IT scores obtained from six evenly divided parts of the DA, which was positively correlated with gestational ages in singletons. Total IT scores were smaller in preterm twins than in singletons, although no difference in gestational age, birth weight, or gender ratio was observed. These data suggest that IT development of the DA is attenuated in sheep preterm twins, which may affect the higher morbidity of PDA.

  12. Lower perinatal mortality in preterm born twins than in singletons: a nationwide study from The Netherlands.

    Science.gov (United States)

    Vasak, Blanka; Verhagen, Jessica J; Koenen, Steven V; Koster, Maria P H; de Reu, Paul A O M; Franx, Arie; Nijhuis, Jan G; Bonsel, Gouke J; Visser, Gerard H A

    2017-02-01

    Twin pregnancies are at increased risk for perinatal morbidity and death because of many factors that include a high incidence of preterm delivery. Compared with singleton pregnancies, overall perinatal risk of death is higher in twin pregnancies; however, for the preterm period, the perinatal mortality rate has been reported to be lower in twins. The purpose of this study was to compare perinatal mortality rates in relation to gestational age at birth between singleton and twin pregnancies, taking into account socioeconomic status, fetal sex, and parity. We studied perinatal mortality rates according to gestational age at birth in 1,502,120 singletons pregnancies and 51,658 twin pregnancies without congenital malformations who were delivered between 2002 and 2010 after 28 weeks of gestation. Data were collected from the nationwide Netherlands Perinatal Registry. Overall the perinatal mortality rate in twin pregnancies (6.6/1000 infants) was higher than in singleton pregnancies (4.1/1000 infants). However, in the preterm period, the perinatal mortality rate in twin pregnancies was substantially lower than in singleton pregnancies (10.4 per 1000 infants as compared with 34.5 per 1000 infants, respectively) for infants who were born at <37 weeks of gestation; this held especially for antepartum deaths. After 39 weeks of gestation, the perinatal mortality rate was higher in twin pregnancies. Differences in parity, fetal sex, and socioeconomic status did not explain the observed differences in outcome. Overall the perinatal mortality rate was higher in twin pregnancies than in singleton pregnancies, which is most likely caused by the high preterm birth rate in twins and not by a higher mortality rate for gestation, apart from term pregnancies. During the preterm period, the antepartum mortality rate was much lower in twin pregnancies than in singleton pregnancies. We suggest that this might be partially due to a closer monitoring of twin pregnancies, which indirectly

  13. Large baby syndrome in singletons born after frozen embryo transfer (FET)

    DEFF Research Database (Denmark)

    Pinborg, Anja; Henningsen, AA; Loft, A

    2013-01-01

    Are singletons born after frozen embryo transfer (FET) at increased risk of being born large for gestational age (LGA) and if so, is this caused by intrinsic maternal factors or related to the freezing/thawing procedures?......Are singletons born after frozen embryo transfer (FET) at increased risk of being born large for gestational age (LGA) and if so, is this caused by intrinsic maternal factors or related to the freezing/thawing procedures?...

  14. Academic achievement of twins and singletons in early adulthood: Taiwanese cohort study.

    Science.gov (United States)

    Tsou, Meng-Ting; Tsou, Meng-Wen; Wu, Ming-Ping; Liu, Jin-Tan

    2008-07-21

    To examine the long term effects of low birth weight on academic achievements in twins and singletons and to determine whether the academic achievement of twins in early adulthood is inferior to that of singletons. Cohort study. Taiwanese nationwide register of academic outcome. A cohort of 218 972 singletons and 1687 twins born in Taiwan, 1983-5. College attendance and test scores in the college joint entrance examinations. After adjustment for birth weight, gestational age, birth order, and sex and the sociodemographic characteristics of the parents, twins were found to have significantly lower mean test scores than singletons in Chinese, mathematics, and natural science, as well as a 2.2% lower probability of attending college. Low birthweight twins had an 8.5% lower probability of college attendance than normal weight twins, while low birthweight singletons had only a 3.2% lower probability. The negative effects of low birth weight on the test scores in English and mathematics were substantially greater for twins than for singletons. The twin pair analysis showed that the association between birth weight and academic achievement scores, which existed for opposite sex twin pairs, was not discernible for same sex twin pairs, indicating that birth weight might partly reflect other underlying genetic variations. These data support the proposition that twins perform less well academically than singletons. Low birth weight has a negative association with subsequent academic achievement in early adulthood, with the effect being stronger for twins than for singletons. The association between birth weight and academic performance might be partly attributable to genetic factors.

  15. Conformity expectations: Differential effects on IVF twins and singletons' parent-child relationships and adjustment.

    Science.gov (United States)

    Anderson, Kayla N; Rueter, Martha A; Connor, Jennifer J; Chen, Muzi; Damario, Mark

    2015-08-01

    Increased utilization of in vitro fertilization (IVF) to treat infertility has resulted in a growing twin birthrate. Despite early childhood risks, twins have fewer psychosocial problems in middle childhood than singleton children. This study proposes that parents' conformity expectations for children have differential effects on parent-child relationships for twin and singleton children, which indirectly explains twins' more optimum psychosocial adjustment. Parental conformity expectations, parent-child relationship satisfaction, and children's emotional, behavioral, and attention problems were assessed in a sample of 288 6- to 12-year-old IVF-conceived twins and singletons. Overall, parents of twins had higher expectations for child conformity to parent rules than singleton parents. Path models demonstrate that twin status and parental expectations for child conformity interact to influence parent-child relationships, and this interaction indirectly accounted for differences in twins' and singletons' psychosocial adjustment. Findings suggest parenting constructs have differential influences on the association between twin status and parent-child relationships. Parenting research, predominantly conducted with singletons, should be reexamined before applying existing research to twin children and their families. (c) 2015 APA, all rights reserved).

  16. Urban effects of Chennai on sea breeze induced convection and ...

    Indian Academy of Sciences (India)

    Department of Marine, Earth and Atmospheric Sciences, North Carolina State University,. Raleigh, NC ... convergence along the sea breeze front. Shape. Keywords. Convection; sea breeze; urban heat island. J. Earth Syst. Sci. 117, No. 6, December 2008, pp. 897–909 .... (hollow diamond data points) measured over the.

  17. Effects of Brinkman number on thermal-driven convective spherical ...

    African Journals Online (AJOL)

    Brinkman number effects on the thermal-driven convective spherical dynamos are studied analytically. The high temperature of the Earth's inner core boundary is usually conducted by the viscous, electrically conducting fluid of the outer core to the core mantle boundary as the Earth cools. The problem considers conducting ...

  18. No. 261-Prenatal Screening for Fetal Aneuploidy in Singleton Pregnancies.

    Science.gov (United States)

    Chitayat, David; Langlois, Sylvie; Wilson, R Douglas

    2017-09-01

    To develop a Canadian consensus document on maternal screening for fetal aneuploidy (e.g., Down syndrome and trisomy 18) in singleton pregnancies. Pregnancy screening for fetal aneuploidy started in the mid 1960s, using maternal age as the screening test. New developments in maternal serum and ultrasound screening have made it possible to offer all pregnant patients a non-invasive screening test to assess their risk of having a fetus with aneuploidy to determine whether invasive prenatal diagnostic testing is necessary. This document reviews the options available for non-invasive screening and makes recommendations for Canadian patients and health care workers. To offer non-invasive screening for fetal aneuploidy (trisomy 13, 18, 21) to all pregnant women. Invasive prenatal diagnosis would be offered to women who screen above a set risk cut-off level on non-invasive screening or to pregnant women whose personal, obstetrical, or family history places them at increased risk. Currently available non-invasive screening options include maternal age combined with one of the following: (1) first trimester screening (nuchal translucency, maternal age, and maternal serum biochemical markers), (2) second trimester serum screening (maternal age and maternal serum biochemical markers), or (3) 2-step integrated screening, which includes first and second trimester serum screening with or without nuchal translucency (integrated prenatal screen, serum integrated prenatal screening, contingent, and sequential). These options are reviewed, and recommendations are made. Studies published between 1982 and 2009 were retrieved through searches of PubMed or Medline and CINAHL and the Cochrane Library, using appropriate controlled vocabulary and key words (aneuploidy, Down syndrome, trisomy, prenatal screening, genetic health risk, genetic health surveillance, prenatal diagnosis). Results were restricted to systematic reviews, randomized controlled trials, and relevant observational

  19. Prenatal screening for fetal aneuploidy in singleton pregnancies.

    Science.gov (United States)

    Chitayat, David; Langlois, Sylvie; Douglas Wilson, R

    2011-07-01

    To develop a Canadian consensus document on maternal screening for fetal aneuploidy (e.g., Down syndrome and trisomy 18) in singleton pregnancies. Pregnancy screening for fetal aneuploidy started in the mid 1960s, using maternal age as the screening test. New developments in maternal serum and ultrasound screening have made it possible to offer all pregnant patients a non-invasive screening test to assess their risk of having a fetus with aneuploidy to determine whether invasive prenatal diagnostic testing is necessary. This document reviews the options available for non-invasive screening and makes recommendations for Canadian patients and health care workers. To offer non-invasive screening for fetal aneuploidy (trisomy 13, 18, 21) to all pregnant women. Invasive prenatal diagnosis would be offered to women who screen above a set risk cut-off level on non-invasive screening or to pregnant women whose personal, obstetrical, or family history places them at increased risk. Currently available non-invasive screening options include maternal age combined with one of the following: (1) first trimester screening (nuchal translucency, maternal age, and maternal serum biochemical markers), (2) second trimester serum screening (maternal age and maternal serum biochemical markers), or (3) 2-step integrated screening, which includes first and second trimester serum screening with or without nuchal translucency (integrated prenatal screen, serum integrated prenatal screening, contingent, and sequential). These options are reviewed, and recommendations are made. Studies published between 1982 and 2009 were retrieved through searches of PubMed or Medline and CINAHL and the Cochrane Library, using appropriate controlled vocabulary and key words (aneuploidy, Down syndrome, trisomy, prenatal screening, genetic health risk, genetic health surveillance, prenatal diagnosis). Results were restricted to systematic reviews, randomized controlled trials, and relevant observational

  20. Twin versus singleton pregnancies: the incidence, pregnancy complications, and obstetric outcomes in a Nigerian tertiary hospital.

    Science.gov (United States)

    Obiechina, Nj; Okolie, Ve; Eleje, Gu; Okechukwu, Zc; Anemeje, Oa

    2011-01-01

    Twin pregnancy is associated with more pregnancy complications and poorer pregnancy outcome than singleton pregnancy. Hence periodic review is necessary to improve on the pregnancy outcome. To determine the incidence and compare pregnancy complications and obstetric outcomes of twin pregnancies and singleton pregnancies. The twin pregnancies (study group) that were delivered at Nnamdi Azikiwe University Teaching Hospital (NAUTH), Nnewi, South-East Nigeria from 1st February 2005 to 31st January 2010 were compared with singleton deliveries (control group) that occurred in the same hospital during the same period. A total of 3351 deliveries were conducted during the study period, of which 113 were twin deliveries, giving an incidence of 1:29.6 deliveries. Only 100 case files could be retrieved for analysis. The mean parities for the twins and singletons were 2.7 ± 2.33 weeks and 1.96 ± 1.87 weeks whereas the mean gestational age at delivery for twin and singleton deliveries were 34 ± 5.2 weeks and 38.7 ± 2.4 weeks respectively (P < 0.05). The mean birth weights were 3.14 ± 0.73 kg and 2.3 ± 1.0 kg for singletons and twins respectively (P < 0.05). Hypertensive disorders of pregnancy, cord prolapse, malpresentation, premature rupture of membranes, low Apgar scores, cesarean section rate, and perinatal death were significantly higher in twin pregnancies than in singleton. The incidence of twin pregnancy over the study period was high and was significantly associated with more pregnancy complications and poorer obstetric outcomes. Close antenatal and intrapartum care are needed in order to improve outcome and decrease complications.

  1. Solar Surface Convection

    Directory of Open Access Journals (Sweden)

    Nordlund Åke

    2009-04-01

    Full Text Available We review the properties of solar convection that are directly observable at the solar surface, and discuss the relevant underlying physics, concentrating mostly on a range of depths from the temperature minimum down to about 20 Mm below the visible solar surface.The properties of convection at the main energy carrying (granular scales are tightly constrained by observations, in particular by the detailed shapes of photospheric spectral lines and the topology (time- and length-scales, flow velocities, etc. of the up- and downflows. Current supercomputer models match these constraints very closely, which lends credence to the models, and allows robust conclusions to be drawn from analysis of the model properties.At larger scales the properties of the convective velocity field at the solar surface are strongly influenced by constraints from mass conservation, with amplitudes of larger scale horizontal motions decreasing roughly in inverse proportion to the scale of the motion. To a large extent, the apparent presence of distinct (meso- and supergranulation scales is a result of the folding of this spectrum with the effective “filters” corresponding to various observational techniques. Convective motions on successively larger scales advect patterns created by convection on smaller scales; this includes patterns of magnetic field, which thus have an approximately self-similar structure at scales larger than granulation.Radiative-hydrodynamical simulations of solar surface convection can be used as 2D/3D time-dependent models of the solar atmosphere to predict the emergent spectrum. In general, the resulting detailed spectral line profiles agree spectacularly well with observations without invoking any micro- and macroturbulence parameters due to the presence of convective velocities and atmosphere inhomogeneities. One of the most noteworthy results has been a significant reduction in recent years in the derived solar C, N, and O abundances with

  2. Observing Convective Aggregation

    Science.gov (United States)

    Holloway, Christopher E.; Wing, Allison A.; Bony, Sandrine; Muller, Caroline; Masunaga, Hirohiko; L'Ecuyer, Tristan S.; Turner, David D.; Zuidema, Paquita

    2017-11-01

    Convective self-aggregation, the spontaneous organization of initially scattered convection into isolated convective clusters despite spatially homogeneous boundary conditions and forcing, was first recognized and studied in idealized numerical simulations. While there is a rich history of observational work on convective clustering and organization, there have been only a few studies that have analyzed observations to look specifically for processes related to self-aggregation in models. Here we review observational work in both of these categories and motivate the need for more of this work. We acknowledge that self-aggregation may appear to be far-removed from observed convective organization in terms of time scales, initial conditions, initiation processes, and mean state extremes, but we argue that these differences vary greatly across the diverse range of model simulations in the literature and that these comparisons are already offering important insights into real tropical phenomena. Some preliminary new findings are presented, including results showing that a self-aggregation simulation with square geometry has too broad distribution of humidity and is too dry in the driest regions when compared with radiosonde records from Nauru, while an elongated channel simulation has realistic representations of atmospheric humidity and its variability. We discuss recent work increasing our understanding of how organized convection and climate change may interact, and how model discrepancies related to this question are prompting interest in observational comparisons. We also propose possible future directions for observational work related to convective aggregation, including novel satellite approaches and a ground-based observational network.

  3. Magneto-convection.

    Science.gov (United States)

    Stein, Robert F

    2012-07-13

    Convection is the transport of energy by bulk mass motions. Magnetic fields alter convection via the Lorentz force, while convection moves the fields via the curl(v×B) term in the induction equation. Recent ground-based and satellite telescopes have increased our knowledge of the solar magnetic fields on a wide range of spatial and temporal scales. Magneto-convection modelling has also greatly improved recently as computers become more powerful. Three-dimensional simulations with radiative transfer and non-ideal equations of state are being performed. Flux emergence from the convection zone through the visible surface (and into the chromosphere and corona) has been modelled. Local, convectively driven dynamo action has been studied. The alteration in the appearance of granules and the formation of pores and sunspots has been investigated. Magneto-convection calculations have improved our ability to interpret solar observations, especially the inversion of Stokes spectra to obtain the magnetic field and the use of helioseismology to determine the subsurface structure of the Sun.

  4. Blending geological observations and convection models to reconstruct mantle dynamics

    Science.gov (United States)

    Coltice, Nicolas; Bocher, Marie; Fournier, Alexandre; Tackley, Paul

    2015-04-01

    Knowledge of the state of the Earth mantle and its temporal evolution is fundamental to a variety of disciplines in Earth Sciences, from the internal dynamics to its many expressions in the geological record (postglacial rebound, sea level change, ore deposit, tectonics or geomagnetic reversals). Mantle convection theory is the centerpiece to unravel the present and past state of the mantle. For the past 40 years considerable efforts have been made to improve the quality of numerical models of mantle convection. However, they are still sparsely used to estimate the convective history of the solid Earth, in comparison to ocean or atmospheric models for weather and climate prediction. The main shortcoming is their inability to successfully produce Earth-like seafloor spreading and continental drift self-consistently. Recent convection models have begun to successfully predict these processes. Such breakthrough opens the opportunity to retrieve the recent dynamics of the Earth's mantle by blending convection models together with advanced geological datasets. A proof of concept will be presented, consisting in a synthetic test based on a sequential data assimilation methodology.

  5. Physical examination-indicated cerclage in singleton and twin pregnancies: maternal-fetal outcomes.

    Science.gov (United States)

    Bernabeu, Andrea; Goya, Maria; Martra, Miquel; Suy, Anna; Pratcorona, Laia; Merced, Carme; Llurba, Elisa; Casellas, Manel; Carreras, Elena; Cabero, Luis

    2016-01-01

    To study maternal and perinatal outcomes after physical examination-indicated cerclage in both singleton and twin pregnancies and evaluate the possible risk factors associated. Retrospective review of all women undergoing physical examination-indicated cerclage at the Hospital Vall d'Hebro, Barcelona from January 2009 to December 2012 after being diagnosed with cervical incompetence and risk of premature birth. During the study period, 60 cases of women diagnosed with cervical incompetence who were carrying live and morphologically-normal fetuses (53 singleton and 7 twin pregnancies), and who had an imminent risk of premature birth were evaluated. Mean gestational age until birth was 35 weeks in singleton and 32 weeks in twin pregnancies. Four cases (7.5%) of immature births and one case (2.0%) of neonatal death were recorded in singleton pregnancies. No cases of immature births or neonatal deaths were recorded in twin pregnancies. Diagnostic amniocentesis was performed IN all cases to rule out possible chorioamnionitis. Physical examination-indicated cerclage for cervical incompetence in women at risk for immature or preterm birth demonstrates good perinatal prognosis without increasing maternal morbidity in either singleton or twin pregnancies. The increase in gestation time in our study may also have been due to the fact that patients with subclinical chorioamnionitis were excluded by diagnostic amniocentesis.

  6. Changes in the convective population and thermodynamic environments in convection-permitting regional climate simulations over the United States

    Science.gov (United States)

    Rasmussen, K. L.; Prein, A. F.; Rasmussen, R. M.; Ikeda, K.; Liu, C.

    2017-11-01

    Novel high-resolution convection-permitting regional climate simulations over the US employing the pseudo-global warming approach are used to investigate changes in the convective population and thermodynamic environments in a future climate. Two continuous 13-year simulations were conducted using (1) ERA-Interim reanalysis and (2) ERA-Interim reanalysis plus a climate perturbation for the RCP8.5 scenario. The simulations adequately reproduce the observed precipitation diurnal cycle, indicating that they capture organized and propagating convection that most climate models cannot adequately represent. This study shows that weak to moderate convection will decrease and strong convection will increase in frequency in a future climate. Analysis of the thermodynamic environments supporting convection shows that both convective available potential energy (CAPE) and convective inhibition (CIN) increase downstream of the Rockies in a future climate. Previous studies suggest that CAPE will increase in a warming climate, however a corresponding increase in CIN acts as a balancing force to shift the convective population by suppressing weak to moderate convection and provides an environment where CAPE can build to extreme levels that may result in more frequent severe convection. An idealized investigation of fundamental changes in the thermodynamic environment was conducted by shifting a standard atmospheric profile by ± 5 °C. When temperature is increased, both CAPE and CIN increase in magnitude, while the opposite is true for decreased temperatures. Thus, even in the absence of synoptic and mesoscale variations, a warmer climate will provide more CAPE and CIN that will shift the convective population, likely impacting water and energy budgets on Earth.

  7. Turbulent convection in liquid metal with and without rotation

    OpenAIRE

    King, Eric M.; Aurnou, Jonathan M.

    2013-01-01

    The magnetic fields of Earth and other planets are generated by turbulent, rotating convection in liquid metal. Liquid metals are peculiar in that they diffuse heat more readily than momentum, quantified by their small Prandtl numbers, . Most analog models of planetary dynamos, however, use moderate fluids, and the systematic influence of reducing is not well understood. We perform rotating Rayleigh–Bénard convection experiments in the liquid metal gallium over a range of nondimensional bu...

  8. Transition to finger convection in double-diffusive convection

    OpenAIRE

    Kellner, M.; Tilgner, A.

    2014-01-01

    Finger convection is observed experimentally in an electrodeposition cell in which a destabilizing gradient of copper ions is maintained against a stabilizing temperature gradient. This double-diffusive system shows finger convection even if the total density stratification is unstable. Finger convection is replaced by an ordinary convection roll if convection is fast enough to prevent sufficient heat diffusion between neighboring fingers, or if the thermal buoyancy force is less than 1/30 of...

  9. Convective heat transfer

    CERN Document Server

    Kakac, Sadik; Pramuanjaroenkij, Anchasa

    2014-01-01

    Intended for readers who have taken a basic heat transfer course and have a basic knowledge of thermodynamics, heat transfer, fluid mechanics, and differential equations, Convective Heat Transfer, Third Edition provides an overview of phenomenological convective heat transfer. This book combines applications of engineering with the basic concepts of convection. It offers a clear and balanced presentation of essential topics using both traditional and numerical methods. The text addresses emerging science and technology matters, and highlights biomedical applications and energy technologies. What’s New in the Third Edition: Includes updated chapters and two new chapters on heat transfer in microchannels and heat transfer with nanofluids Expands problem sets and introduces new correlations and solved examples Provides more coverage of numerical/computer methods The third edition details the new research areas of heat transfer in microchannels and the enhancement of convective heat transfer with nanofluids....

  10. Prevention of Preterm Birth with Pessary in Singletons (PoPPS): a randomized controlled trial.

    Science.gov (United States)

    Dugoff, Lorraine; Berghella, Vincenzo; Sehdev, Harish; Mackeen, A Dhanya; Goetzl, Laura; Ludmir, Jack

    2017-09-20

    To determine if pessary use prevents preterm birth in singleton gestations with a short transvaginal ultrasound cervical length and without a prior spontaneous preterm birth. In this open-label multicenter randomized trial we enrolled asymptomatic women with singleton gestations with a transvaginal ultrasound cervical length ≤ 25 mm at 18 0 -23 6 weeks and no prior spontaneous preterm birth. Subjects were randomized to receive the Bioteque cup pessary or no pessary. Pessaries were inserted by trained maternal fetal medicine staff.. Vaginal progesterone was recommended to women with a cervical length ≤20mm. The primary outcome was preterm birth preterm birth preterm birth preterm birth preterm birth in women with singleton gestations with a short transvaginal ultrasound cervical length and without a prior spontaneous preterm birth in this small underpowered randomized controlled trial. This trial was registered on ClinicalTrials.gov, number NCT 02056652. This article is protected by copyright. All rights reserved.

  11. Risk of Metabolic Syndrome and Diabetes Mellitus Among Young Twins and Singletons in Guinea-Bissau

    DEFF Research Database (Denmark)

    Bjerregaard-Andersen, Morten; Hansen, Lone; da Silva, Leontina I

    2013-01-01

    OBJECTIVETwins in Africa may be at increased risk of metabolic disorders due to strained conditions in utero, including high exposure to infections. We studied metabolic syndrome (MS) and diabetes mellitus (DM) among young twins and singletons in Guinea-Bissau.RESEARCH DESIGN AND METHODSThe study...... was cross-sectional and occurred from October 2009 until August 2011 at the Bandim Health Project, a demographic surveillance site in the capital Bissau. Twins and singleton controls between 5 and 32 years were visited at home. Fasting blood samples for metabolic measurements were collected. Zygosity...... was established genetically for a subset. DM was defined as HbA1c ≥6.5% (48 mmol/mol) and MS by the International Diabetes Federation criteria.RESULTSHbA1c was available for 574 twins and 463 singletons. Mean age was 15.3 years versus 15.8 years, respectively. Eighteen percent of twins were monozygotic...

  12. Stovetop Earth Pecan Pie

    Science.gov (United States)

    Robin, C. M.

    2005-12-01

    Many fluid mechanical experiments with direct applications to Earth Science are performed with sugary syrups using conceptually straightforward procedures. Corn syrup has indeed proven to be a godsend for those studying convection and related non-linear phenomena. In addition, however, it gives experimentalists a deep physical intuition for the interior workings of hot planets. The basic concepts behind plate tectonics and mantle convection are not difficult; indeed, although they may not be aware of it, most students probably have a basic intuitive understanding of fluid mechanics gained in their daily life. However, the large size and long time scale of geophysical processes may be quite intimidating to young students. Even a simple geophysical experiment requires a complicated array of coolers, heaters and measuring and recording equipment. It is of interest to introduce students to the geodynamical concepts that can be visualized in a high-tech lab using familiar processes and equipment. Using a homemade apparatus and grocery store supplies, I propose using a 'Stove-top Earth pecan pie' to introduce simple geodynamic concepts to middle- and high-school students. The initially cold syrup heats up and the pecans begin to float (continent formation), the syrup begins to convect (mantle convection), and convection slows down after the heat is removed (secular cooling). Even Wilson cycles can be simulated by moving the pan to one side or the other of the stovetop or heating element. The activity formally introduces students to convection and its application to the earth, and makes them think about plate motion, heat transfer, scaling, and experimental procedures. As an added bonus, they can eat their experiments after recess!

  13. Healthcare expenses associated with multiple vs singleton pregnancies in the United States.

    Science.gov (United States)

    Lemos, Elkin V; Zhang, Dongmu; Van Voorhis, Bradley J; Hu, X Henry

    2013-12-01

    The purpose of this study was to document cost that is associated with multiple births vs singleton births in the United States. This was a retrospective cohort study that used a claims database. Women 19-45 years old with live-born infants from 2005-2010 were identified. Infant deliveries were identified by International Classification of Diseases, 9th Revision, Clinical Modification diagnosis codes. The cost entailed all payment made by insurers and patients. For mothers, the cost included expenses from 27 weeks before delivery to 1 month after delivery. For infants, the cost contained all expenses until their first birthday. Adjusted cost was estimated by generalized linear models after adjustment for the potential confounding variables with a gamma distribution and a log link. The analysis included 437,924 eligible deliveries. Of them, 97.02% were singletons; 2.85% were twins, and 0.13% was triplets or more. Women with multiple pregnancies had higher systemic and localized comorbidities compared with women with singleton pregnancies (P < .0001). Twins and triplets or more were more likely to have stayed in a neonatal intensive care unit than were singletons (P < .0001). On average, adjusted total all-cause health care cost was $21,458 (95% confidence interval [CI], $21,302-21,614) per delivery with singletons, $104,831 (95% CI, $103,402-106,280) with twins, and $407,199 (95% CI, $384,984-430,695) with triplets or more. Pregnancies with the delivery of twins cost approximately 5 times as much when compared with singleton pregnancies; pregnancies with delivery of triplets or more cost nearly 20 times as much. Copyright © 2013 Mosby, Inc. All rights reserved.

  14. Assisted Reproductive Technology and Newborn Size in Singletons Resulting from Fresh and Cryopreserved Embryos Transfer.

    Directory of Open Access Journals (Sweden)

    Galit Levi Dunietz

    Full Text Available The aim of this study was two-fold: to investigate the association of Assisted Reproductive Technology (ART and small newborn size, using standardized measures; and to examine within strata of fresh and cryopreserved embryos transfer, whether this association is influenced by parental infertility diagnoses. We used a population-based retrospective cohort from Michigan (2000-2009, Florida and Massachusetts (2000-2010. Our sample included 28,946 ART singletons conceived with non-donor oocytes and 4,263,846 non-ART singletons.Regression models were used to examine the association of ART and newborn size, measured as small for gestational age (SGA and birth-weight-z-score, among four mutually exclusive infertility groups: female infertility only, male infertility only, combined female and male infertility, and unexplained infertility, stratified by fresh and cryopreserved embryos transfer.We found increased SGA odds among ART singletons from fresh embryos transfer compared with non-ART singletons, with little difference by infertility source [adjusted odds-ratio for SGA among female infertility only: 1.18 (95% CI 1.10, 1.26, male infertility only: 1.20 (95% CI 1.10, 1.32, male and female infertility: 1.18 (95% CI 1.06, 1.31 and unexplained infertility: 1.24 (95% CI 1.10, 1.38]. Conversely, ART singletons, born following cryopreserved embryos transfer, had lower SGA odds compared with non-ART singletons, with mild variation by infertility source [adjusted odds-ratio for SGA among female infertility only: 0.56 (95% CI 0.45, 0.71, male infertility only: 0.64 (95% CI 0.47, 0.86, male and female infertility: 0.52 (95% CI 0.36, 0.77 and unexplained infertility: 0.71 (95% CI 0.47, 1.06]. Birth-weight-z-score was significantly lower for ART singletons born following fresh embryos transfer than non-ART singletons, regardless of infertility diagnoses.

  15. Lower marriage and divorce rates among twins than among singletons in Danish birth cohorts 1940-1964

    DEFF Research Database (Denmark)

    Petersen, Inge; Martinussen, Torben; McGue, Matthew

    2011-01-01

    compare rates of marriage and divorce in a sample of 35,975 twins and 81,803 singletons born 1940-1964. Cox-regressions are used in order to control for potential confounders. We find that compared with singletons twins have significantly lower marriage rates: (males: 15-19 years: Hazard Ratio (HR) = 0...... twins compared with singletons (HR=0.87, 95%CI: 0.83-0.90). These differences offset each other, thus 57% of both populations remain in their first marriage until censoring. The interpretation may be that since twins have a partner from birth, they do not have the same need for marriage as singletons...

  16. Why do singletons conceived after assisted reproduction technology have adverse perinatal outcome?

    DEFF Research Database (Denmark)

    Pinborg, A; Wennerholm, U B; Romundstad, L B

    2013-01-01

    Assisted reproduction technology (ART) is used worldwide, at increasing rates, and data show that some adverse outcomes occur more frequently than following spontaneous conception (SC). Possible explanatory factors for the well-known adverse perinatal outcome in ART singletons were evaluated....

  17. Ambulatory arterial stiffness index is unchanged in uncomplicated third-trimester singleton and twin pregnancies.

    Science.gov (United States)

    Kärkkäinen, Henna; Heiskanen, Nonna; Saarelainen, Heli; Valtonen, Pirjo; Lyyra-Laitinen, Tiina; Laitinen, Tomi; Vanninen, Esko; Heinonen, Seppo

    2011-05-01

    To document the ambulatory arterial stiffness index (AASI) during pregnancy compared to three months after delivery in singleton and twin pregnancies. Descriptive study with a follow-up design. University hospital in Eastern Finland. 43 childbearing women; 32 with singleton and 11 with twin pregnancies. Ambulatory blood pressure measurements were conducted using a digital ambulatory blood pressure system. AASI was calculated as 1 minus the regression slope of diastolic on systolic blood pressures obtained from 24-hour monitoring. Arterial stiffness measured by AASI. In normotensive pregnant women, the 95th percentiles of AASI were 0.40 in singleton and 0.46 in twin pregnancies, respectively, implying arterial normality and high elasticity. There were no differences in AASI values between singleton and twin pregnancies and no changes were observed postpartum. After delivery, but not during pregnancy, AASI correlated negatively with nocturnal systolic and diastolic blood pressure reduction (dipping) (r=-0.536, p=0.001; r=-0.674, ptwin pregnancies had no detectable effects on AASI. However, pregnancy appeared to overcome the negative effects of low high-density lipoproteins, unfavorable dipping status and advanced maternal age on arterial stiffness, but not the effect caused by maternal body mass index. © 2011 The Authors Acta Obstetricia et Gynecologica Scandinavica© 2011 Nordic Federation of Societies of Obstetrics and Gynecology.

  18. Trends in preterm birth in singleton deliveries in a Hong Kong population

    NARCIS (Netherlands)

    Hui, Annie S. Y.; Lao, Terence T.; Leung, Tak Yeung; Schaaf, Jelle M.; Sahota, Daljit S.

    2014-01-01

    To examine trends in preterm birth and its relationship with perinatal mortality in Hong Kong. In a retrospective cohort study, data were reviewed from singletons delivered between 1995 and 2011 at a university teaching hospital. Trends in preterm birth (between 24 and 36 weeks of pregnancy),

  19. Body size in five-year-old twins: Heritability and comparison to singleton standards

    NARCIS (Netherlands)

    Estourgie-van Burk, G.F.; Bartels, M.; van Beijsterveldt, C.E.M.; Delemarre-van de Waal, H.A.; Boomsma, D.I.

    2006-01-01

    The aim of this study is to examine causes of individual differences in height, weight and body mass index (BMI) in 5-year-old children registered with the Netherlands Twin Register. In addition, we examine whether the results of twin studies can be expanded to the singleton population by comparing

  20. Comparison of Late Mortality Among Twins Versus Singletons With Congenital Heart Defects

    DEFF Research Database (Denmark)

    Herskind, Anne Maria; Larsen, Lisbeth Aagaard; Pedersen, Dorthe Almind

    2017-01-01

    In 2014, in the United States, nearly 7% of newborns were twins. Congenital heart defects (CHDs) are more frequent in both monozygotic and dizygotic twins than in singletons. Still, the longer-term prognosis for CHD twins is unknown. Here we assess the mortality pattern for CHD twins up to age 36...... years and compare it with that for non-CHD twins, non-CHD co-twins, and CHD singletons. We identified all twins and a 5% random sample of all singletons born in Denmark from 1977 to 2009 by linking Danish national population and health registers. CHD cases were defined as subjects having a primary...... inpatient diagnosis of CHD (excluding preterm ductus) within the first year of life, and mortality was assessed through 2013. Among 63,362 live-born twin individuals, a total of 373 twins (0.59%) had a CHD diagnosis, whereas the corresponding numbers for singletons were 383 of 98,647 (0.39%). During...

  1. Systematic review of progesterone for the prevention of preterm birth in singleton pregnancies

    DEFF Research Database (Denmark)

    Rode, Line; Langhoff-Roos, Jens; Andersson, Charlotte

    2009-01-01

    BACKGROUND: A Cochrane review in 2006 concluded that further knowledge is required before recommendation can be made with regard to progesterone in the prevention of preterm birth. OBJECTIVE: To provide an update on the preventive effect of progesterone on preterm birth in singleton pregnancies. ...

  2. Trends in preterm birth: singleton and multiple pregnancies in the Netherlands, 2000-2007

    NARCIS (Netherlands)

    Schaaf, J. M.; Mol, B. W. J.; Abu-Hanna, A.; Ravelli, A. C. J.

    2011-01-01

    Several studies have reported increasing trends in preterm birth in developed countries, mainly attributable to an increase in medically indicated preterm births. Our aim was to describe trends in preterm birth among singleton and multiple pregnancies in the Netherlands. Prospective cohort study.

  3. Development and health of 5 - 8-year-old singletons born after intracytoplasmic sperm injection

    NARCIS (Netherlands)

    Knoester, Marjolein

    2007-01-01

    This thesis describes the Leiden Artificial Reproductive Techniques Follow-up Project. In this project, the potential long-term effects of intracytoplasmic sperm injection (ICSI) were assessed in 5 – 8-year-old singleton children. ICSI is the method of artificial reproduction in which a sperm cel is

  4. Stillbirth rates in singleton pregnancies in a stable population at Karl ...

    African Journals Online (AJOL)

    To determine the changes in stillbirth rates in singleton pregnancies in a stable population over a period of 50 years. Methods. Stillbirth rates for ... stillbirths, neonatal deaths and deliveries, from which the stillbirth rates for fetuses ≥500 g ... from black residential areas have recently increased rapidly, the study was limited to ...

  5. Trends in birth asphyxia, obstetric interventions and perinatal mortality among term singletons: a nationwide cohort study

    NARCIS (Netherlands)

    Ensing, Sabine; Abu-Hanna, Ameen; Schaaf, Jelle M.; Mol, Ben Willem J.; Ravelli, Anita C. J.

    2015-01-01

    The objective of the present study is to investigate trends in birth asphyxia and perinatal mortality in the Netherlands over the last decade. A nationwide cohort study among women with a term singleton pregnancy. We assessed trends in birth asphyxia in relation to obstetric interventions for fetal

  6. Preterm birth in singleton and multiple pregnancies : evaluation of costs and perinatal outcomes

    NARCIS (Netherlands)

    van Baaren, Gert J.; Peelen, Myrthe J. C. S.; Schuit, Ewoud; van der Post, Joris A. M.; Mol, Ben W. J.; Kok, Marjolein; Hajenius, Petra J.

    Objective: To estimate costs of preterm birth in singleton and multiple pregnancies. Study design: Cost analysis based on data from a prospective cohort study and three multicentre randomised controlled trials (2006-2012) in a Dutch nationwide consortium for women's health research. Women with

  7. Simulating deep convection with a shallow convection scheme

    Directory of Open Access Journals (Sweden)

    C. Hohenegger

    2011-10-01

    Full Text Available Convective processes profoundly affect the global water and energy balance of our planet but remain a challenge for global climate modeling. Here we develop and investigate the suitability of a unified convection scheme, capable of handling both shallow and deep convection, to simulate cases of tropical oceanic convection, mid-latitude continental convection, and maritime shallow convection. To that aim, we employ large-eddy simulations (LES as a benchmark to test and refine a unified convection scheme implemented in the Single-column Community Atmosphere Model (SCAM. Our approach is motivated by previous cloud-resolving modeling studies, which have documented the gradual transition between shallow and deep convection and its possible importance for the simulated precipitation diurnal cycle.

    Analysis of the LES reveals that differences between shallow and deep convection, regarding cloud-base properties as well as entrainment/detrainment rates, can be related to the evaporation of precipitation. Parameterizing such effects and accordingly modifying the University of Washington shallow convection scheme, it is found that the new unified scheme can represent both shallow and deep convection as well as tropical and mid-latitude continental convection. Compared to the default SCAM version, the new scheme especially improves relative humidity, cloud cover and mass flux profiles. The new unified scheme also removes the well-known too early onset and peak of convective precipitation over mid-latitude continental areas.

  8. Do very preterm twins and singletons differ in their neurodevelopment at 5 years of age?

    Science.gov (United States)

    Bodeau-Livinec, Florence; Zeitlin, Jennifer; Blondel, Béatrice; Arnaud, Catherine; Fresson, Jeanne; Burguet, Antoine; Subtil, Damien; Marret, Stéphane; Rozé, Jean-Christophe; Marchand-Martin, Laetitia; Ancel, Pierre-Yves; Kaminski, Monique

    2013-11-01

    Twins have inconsistently shown poorer outcomes than singletons. Although a high proportion of twins are born very preterm, data are sparse on the long-term outcomes in very preterm twins. The objective of this study was to compare mortality and neurodevelopmental outcomes of very preterm singletons and twins and to study outcomes in relation to factors specific to twins. Birth cohort study Etude Epidemiologique sur les Petits Ages Gestationnels (EPIPAGE). Nine regions in France. All very preterm live births occurring from 22 to 32 weeks of gestation in all maternity wards of nine French regions in 1997 (n=2773). Neurodevelopmental status, including cerebral palsy, and a cognitive assessment with the Kaufman Assessment Battery for Children, with scores on the Mental Processing Composite (MPC) scale, was available for 1732 and 1473 children at 5 years of age, respectively. Among live births, twins had higher hospital mortality than singletons (adjusted (a)OR: 1.4 (95% CI 1.1 to 1.9)). Among survivors, there was no crude difference at 5 years between twins and singletons in the prevalence of cerebral palsy (8.0% vs 9.1%, respectively), MPC <70 (9.5% vs 11.1%) and mean MPC (94.6 vs 94.4). However, after adjustment for sex, gestational age, intrauterine growth restriction and social factors, twins were more likely to have lower MPC scores (mean difference: -2.4 (95% CI-4.8 to 0.01)). Live born twins had a higher risk of mortality when birth weight discordance was present (aOR:2.9 (95% CI 1.7 to 4.8)), but there were no differences in long-term outcomes. Compared with very preterm singletons, twins had higher mortality, no difference with respect to severe deficiencies, but slightly lower MPC scores at 5 years.

  9. Gestational diabetes mellitus: glycemic control during pregnancy and neonatal outcomes of twin and singleton pregnancies.

    Science.gov (United States)

    Guillén-Sacoto, María Augusta; Barquiel, Beatriz; Hillman, Natalia; Burgos, María Ángeles; Herranz, Lucrecia

    2018-04-20

    To assess the impact of glycemic control in gestational on neonatal weight and metabolic complications of twin and singleton pregnancies. An observational, retrospective study to monitor 120 twin and 240 singleton pregnancies in women with GDM. Maternal glycemic parameters during pregnancy (oral glucose tolerance test results, treatment, insulinization rate, mean HbA1c in the third trimester), and neonatal complications and weight were recorded. A higher infant birth weight ratio (IBWR 1.02±0.12 vs. 0.88±0.12, P<.001) and a lower rate of newborns small for gestational age (severe SGA 2.5% vs. 8.3%, P=.012) were seen after singleton pregnancies as compared to twin pregnancies. The rates of newborns large for gestational age (LGA 12.6% vs. 12.5%, P=.989); macrosomic (6.7% vs. 7.5%, P=.777); or small for gestational age (SGA 6.7% vs. 10.8%, P=.175) were similar in both groups. Neonates from twin pregnancies had a higher risk of hypoglycemia (adjusted OR 4.71; 1.38-16.07, P=.013) and polycythemia (adjusted OR 10.05; 1.82-55.42, P=0.008). A linear relationship was seen between third trimester HbA1c levels and IBWR in singleton (r=.199, P=.003), but not in twin pregnancies (r=0.049, P=0.610). Risk of severe SGA, hypoglycemia, and polycythemia was significantly higher in twin pregnancies of women with GDM. Neonatal weight outcomes and metabolic complications in twin pregnancies of women with GDM were not related to glycemic control. Moreover, in our study population, fasting glucose at diagnosis and mean HbA1c in the third trimester showed a linear relationship with higher birth weights in singleton, but not in twin pregnancies. Copyright © 2018 SEEN y SED. Publicado por Elsevier España, S.L.U. All rights reserved.

  10. Placenta previa and risk of major congenital malformations among singleton births in Finland.

    Science.gov (United States)

    Kancherla, Vijaya; Räisänen, Sari; Gissler, Mika; Kramer, Michael R; Heinonen, Seppo

    2015-06-01

    Placenta previa has been associated with adverse birth outcomes, but its association with congenital malformations is inconclusive. We examined the association between placenta previa and major congenital malformations among singleton births in Finland. We performed a retrospective population register-based study on all singletons born at or after 22+0 weeks of gestation in Finland during 2000 to 2010. We linked three national health registers: the Finnish Medical Birth Register, the Hospital Discharge Register, and the Register of Congenital Malformations, and examined several demographic and clinical characteristics among women with and without placenta previa, in association with major congenital malformations. We estimated adjusted odds ratios and 95% confidence intervals using multivariable logistic regression models. The prevalence of placenta previa was estimated as 2.65 per 1000 singleton births in Finland (95% confidence interval, 2.53-2.79). Overall, 6.2% of women with placenta previa delivered a singleton infant with a major congenital malformation, compared with 3.8% of unaffected women (p ≤ 0.001). Placenta previa was positively associated with almost 1.6-fold increased risk of major congenital malformations in the offspring, after controlling for maternal age, parity, fetal sex, smoking, socio-economic status, chorionic villus biopsy, In vitro fertilization, pre-existing diabetes, depression, preeclampsia, and prior caesarean section (adjusted odds ratio = 1.55; 95% confidence interval, 1.27-1.90). Using a large population-based study, we found that placenta previa was weakly, but significantly associated with an increased risk of major congenital malformations in singleton births. Future studies should examine the association between placenta previa and individual types of congenital malformations, specifically in high-risk pregnancies. © 2015 Wiley Periodicals, Inc.

  11. Mathematical models of convection

    CERN Document Server

    Andreev, Victor K; Goncharova, Olga N; Pukhnachev, Vladislav V

    2012-01-01

    Phenomena of convection are abundant in nature as well as in industry. This volume addresses the subject of convection from the point of view of both, theory and application. While the first three chapters provide a refresher on fluid dynamics and heat transfer theory, the rest of the book describes the modern developments in theory. Thus it brings the reader to the ""front"" of the modern research. This monograph provides the theoretical foundation on a topic relevant to metallurgy, ecology, meteorology, geo-and astrophysics, aerospace industry, chemistry, crystal physics, and many other fiel

  12. Impact of obstetric history on the risk of spontaneous preterm birth in singleton and multiple pregnancies: a systematic review.

    Science.gov (United States)

    Kazemier, B M; Buijs, P E; Mignini, L; Limpens, J; de Groot, C J M; Mol, B W J

    2014-09-01

    Information about the recurrence of spontaneous preterm birth in subsequent twin/singleton pregnancies is scattered. To quantify the risk of recurrence of spontaneous preterm birth in different subtypes of subsequent pregnancies. An electronic literature search in OVID MEDLINE and EMBASE, complemented by PubMed, to find recent studies. Studies comparing the risk of spontaneous preterm birth after a previous preterm and previous term pregnancy. The absolute risk of recurrence with a 95% confidence interval and the absolute risk of preterm birth after a term delivery were calculated. Data from studies were pooled using the Mantel-Haenszel method. We detected 13 relevant studies. The risk of recurrence of preterm birth was significantly increased in all preterm pregnancy subtypes, compared with their term counterparts. Women pregnant with twins after a previous preterm singleton had the highest absolute risk of recurrence (57.0%, 95% CI 51.9-61.9%), and after a previous term singleton their absolute risk was 25% (95% CI 24.3-26.5%). Women pregnant with a singleton after a previous preterm twin pregnancy have an absolute recurrence risk of 10% (95% CI 8.2-12.3%), whereas a singleton pregnancy after delivering a previous twin up to term yields a low absolute risk of only 1.3% (95% CI 0.8-2.2). Women pregnant with a singleton after a previous preterm singleton have an absolute recurrence risk of 20% (95% CI 19.9-20.6). The risk of recurrence of preterm birth is influenced by the singleton/twin order in both pregnancies, and varies between 10% for a singleton after previous preterm twins to 57% for twins after a previous preterm singleton. © 2014 Royal College of Obstetricians and Gynaecologists.

  13. CDM Convective Forecast Planning guidance

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The CDM Convective Forecast Planning (CCFP) guidance product provides a foreast of en-route aviation convective hazards. The forecasts are updated every 2 hours and...

  14. Turbulent convection in liquid metal with and without rotation.

    Science.gov (United States)

    King, Eric M; Aurnou, Jonathan M

    2013-04-23

    The magnetic fields of Earth and other planets are generated by turbulent, rotating convection in liquid metal. Liquid metals are peculiar in that they diffuse heat more readily than momentum, quantified by their small Prandtl numbers, Pr rotating Rayleigh-Bénard convection experiments in the liquid metal gallium (Pr = 0.025) over a range of nondimensional buoyancy forcing (Ra) and rotation periods (E). Our primary diagnostic is the efficiency of convective heat transfer (Nu). In general, we find that the convective behavior of liquid metal differs substantially from that of moderate Pr fluids, such as water. In particular, a transition between rotationally constrained and weakly rotating turbulent states is identified, and this transition differs substantially from that observed in moderate Pr fluids. This difference, we hypothesize, may explain the different classes of magnetic fields observed on the Gas and Ice Giant planets, whose dynamo regions consist of Pr 1 fluids, respectively.

  15. Convective overshooting in stars

    NARCIS (Netherlands)

    Andrássy, R.

    2015-01-01

    Numerous observations provide evidence that the standard picture, in which convective mixing is limited to the unstable layers of a star, is incomplete. The mixing layers in real stars are significantly more extended than what the standard models predict. Some of the observations require changing

  16. Stochasticc convection parameterization

    NARCIS (Netherlands)

    Dorrestijn, J.

    2016-01-01

    Clouds are chaotic, difficult to predict, but above all, magnificent natural phenomena. There are different types of clouds: stratus, a layer of clouds that may produce drizzle, cirrus, clouds in the higher parts of the atmosphere, and cumulus, clouds that arise in convective updrafts. Thermals,

  17. Scaling of plate tectonic convection with pseudoplastic rheology

    Science.gov (United States)

    Korenaga, Jun

    2010-11-01

    The scaling of plate tectonic convection is investigated by simulating thermal convection with pseudoplastic rheology and strongly temperature-dependent viscosity. The effect of mantle melting is also explored with additional depth-dependent viscosity. Heat flow scaling can be constructed with only two parameters, the internal Rayleigh number and the lithospheric viscosity contrast, the latter of which is determined entirely by rheological properties. The critical viscosity contrast for the transition between plate tectonic and stagnant lid convection is found to be proportional to the square root of the internal Rayleigh number. The relation between mantle temperature and surface heat flux on Earth is discussed on the basis of these scaling laws, and the inverse relationship between them, as previously suggested from the consideration of global energy balance, is confirmed by this fully dynamic approach. In the presence of surface water to reduce the effective friction coefficient, the operation of plate tectonics is suggested to be plausible throughout the Earth history.

  18. Convective Propagation Characteristics Using a Simple Representation of Convective Organization

    Science.gov (United States)

    Neale, R. B.; Mapes, B. E.

    2016-12-01

    Observed equatorial wave propagation is intimately linked to convective organization and it's coupling to features of the larger-scale flow. In this talk we a use simple 4 level model to accommodate vertical modes of a mass flux convection scheme (shallow, mid-level and deep). Two paradigms of convection are used to represent convective processes. One that has only both random (unorganized) diagnosed fluctuations of convective properties and one with organized fluctuations of convective properties that are amplified by previously existing convection and has an explicit moistening impact on the local convecting environment We show a series of model simulations in single-column, 2D and 3D configurations, where the role of convective organization in wave propagation is shown to be fundamental. For the optimal choice of parameters linking organization to local atmospheric state, a broad array of convective wave propagation emerges. Interestingly the key characteristics of propagating modes are the low-level moistening followed by deep convection followed by mature 'large-scale' heating. This organization structure appears to hold firm across timescales from 5-day wave disturbances to MJO-like wave propagation.

  19. Intra-hole fluid convection: High-resolution temperature monitoring

    Czech Academy of Sciences Publication Activity Database

    Čermák, Vladimír; Šafanda, Jan; Krešl, Milan

    2008-01-01

    Roč. 348, č. 3-4 (2008), s. 464-479 ISSN 0022-1694 Institutional research plan: CEZ:AV0Z30120515 Keywords : temperature monitoring * convection * fluid dynamics * borehole logging Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 2.305, year: 2008

  20. Convective heat transfer on Mars

    International Nuclear Information System (INIS)

    Arx, A.V. von; Delgado, A. Jr.

    1991-01-01

    An examination was made into the feasibility of using convective heat transfer on Mars to reject the waste heat from a Closed Brayton Cycle. Forced and natural convection were compared to thermal radiation. For the three radiator configurations studied, it was concluded that thermal radiation will yield the minimum mass and forced convection will result in the minimum area radiator. Other issues such as reliability of a fan motor were not addressed. Convective heat transfer on Mars warrants further investigation. However, the low density of the Martian atmosphere makes it difficult to utilize convective heat transfer without incurring a weight penalty

  1. Twin-singleton differences in intelligence: a register-based birth cohort study of Norwegian males.

    Science.gov (United States)

    Eriksen, Willy; Sundet, Jon M; Tambs, Kristian

    2012-10-01

    The aim was to determine the difference in intelligence between singletons and twins in young adulthood. Data from the Medical Birth Register of Norway were linked with register data from the Norwegian National Conscript Service. The study base consisted of data on the 445,463 males who were born alive in either single or twin births in Norway during 1967-1984 and who were examined at the time of the mandatory military conscription (age 18-20). Within this study base, there were data on 1,653 sibships of full brothers that included at least one man born in single birth and at least one man born in twin birth (4,307 persons, including 2,378 twins and 1,929 singletons). The intelligence scores of the singletons were 11% (95% confidence interval [CI]: 9-14%) of a standard deviation higher than those of the twins, after adjustment for birth year, birth order, parental ages at delivery, parental education levels, and other factors. The adjusted within-family difference was also 11% (95 % CI: 6-16%) of a standard deviation, indicating that unmeasured factors shared by siblings (e.g., maternal body height) have not influenced the estimate in important ways. When gestational age at birth was added to the model, the estimate for the difference in intelligence score was approximately the same. Including birth weight in the model strongly reduced the estimate. In conclusion, twins born in Norway during 1967-1984 had slightly lower intelligence in early adulthood compared with the singletons.

  2. Maternal risk factors for singleton preterm births and survival at the ...

    African Journals Online (AJOL)

    2015-02-24

    Feb 24, 2015 ... ratio [aOR] = 2.63; 95% confidence interval [CI] 1.92, 6.07), Previous preterm birth (aOR = 5.06; 95% CI: 2.66, 9.12), ... on gestational age at birth and mode of delivery, but not on maternal sociodemographic risk factors for singleton preterm births. ... of preterms in this area have become important in order to.

  3. Conformal Maxwell Theory as a Singleton Field Theory on $ADS_{5}$, IIB Three Branes and Duality

    CERN Document Server

    Ferrara, Sergio

    1998-01-01

    We examine the boundary conditions associated with extended supersymmetric Maxwell theory in 5-dimensional anti-De Sitter space. Excitations on the boundary are identical to those of ordinary 4-dimensional conformal invariant super electrodynammics. Extrapolations of these excitations give rise to a 5-dimensional topological gauge theory of the singleton type. The possibility of a connection of this phenomenon to the world volume theory of 3-branes in IIB string theory is discussed.

  4. Hierarchical singleton-type recurrent neural fuzzy networks for noisy speech recognition.

    Science.gov (United States)

    Juang, Chia-Feng; Chiou, Chyi-Tian; Lai, Chun-Lung

    2007-05-01

    This paper proposes noisy speech recognition using hierarchical singleton-type recurrent neural fuzzy networks (HSRNFNs). The proposed HSRNFN is a hierarchical connection of two singleton-type recurrent neural fuzzy networks (SRNFNs), where one is used for noise filtering and the other for recognition. The SRNFN is constructed by recurrent fuzzy if-then rules with fuzzy singletons in the consequences, and their recurrent properties make them suitable for processing speech patterns with temporal characteristics. In n words recognition, n SRNFNs are created for modeling n words, where each SRNFN receives the current frame feature and predicts the next one of its modeling word. The prediction error of each SRNFN is used as recognition criterion. In filtering, one SRNFN is created, and each SRNFN recognizer is connected to the same SRNFN filter, which filters noisy speech patterns in the feature domain before feeding them to the SRNFN recognizer. Experiments with Mandarin word recognition under different types of noise are performed. Other recognizers, including multilayer perceptron (MLP), time-delay neural networks (TDNNs), and hidden Markov models (HMMs), are also tested and compared. These experiments and comparisons demonstrate good results with HSRNFN for noisy speech recognition tasks.

  5. The Singleton case: enforcing medical treatment to put a person to death.

    Science.gov (United States)

    Garasic, Mirko Daniel

    2013-11-01

    In October 2003 the Supreme Court of the United States allowed Arkansas officials to force Charles Laverne Singleton, a schizophrenic prisoner convicted of murder, to take drugs that would render him sane enough to be executed. On January 6 2004 he was killed by lethal injection, raising many ethical questions. By reference to the Singleton case, this article will analyse in both moral and legal terms the controversial justifications of the enforced medical treatment of death-row inmates. Starting with a description of the Singleton case, I will highlight the prima facie reasons for which this case is problematic and merits attention. Next, I will consider the justification of punishment in Western society and, in that context, the evolution of the notion of insanity in the assessment of criminal responsibility during the past two centuries, both in the US and the UK. In doing so, I will take into account the moral justification used to enforce treatment, looking at the conflict between the prisoner's right to treatment and his right to refuse medication where not justified by outcomes that can be reasonably expected to be positive for the individual. Finally, in contrast with some retributivist arguments in favour of enforced treatment to enable execution, I will propose a possible alternative, necessary if we are to consistently uphold the notion of autonomy.

  6. Convection and stellar oscillations

    DEFF Research Database (Denmark)

    Aarslev, Magnus Johan

    2017-01-01

    energy exchange between convection and pulsations, i.e. the modal part of the surface effect. Studying excitation and damping mechanisms requires a non-adiabatic treatment. A major part of my research has been modelling damping rates of red giant stars observed by {\\Kp}. The basis for the non...... atmospheres to replace the outer layers of stellar models. The additional turbulent pressure and asymmetrical opacity effects in the atmosphere model, compared to convection in stellar evolution models, serve to expand the atmosphere. The enlarged acoustic cavity lowers the pulsation frequencies bringing them....... However, the effects are barely prominent enough to be distinguishable with today's observational precision. But it does provide means of determining the mixing-length and enables consistent patching. The previously mentioned investigations are based on adiabatic frequency calculations, which neglect...

  7. Convection heat transfer

    CERN Document Server

    Bejan, Adrian

    2013-01-01

    Written by an internationally recognized authority on heat transfer and thermodynamics, this second edition of Convection Heat Transfer contains new and updated problems and examples reflecting real-world research and applications, including heat exchanger design. Teaching not only structure but also technique, the book begins with the simplest problem solving method (scale analysis), and moves on to progressively more advanced and exact methods (integral method, self similarity, asymptotic behavior). A solutions manual is available for all problems and exercises.

  8. Birthweight distribution in ART singletons resulting from embryo culture in two different culture media compared with the national population.

    Science.gov (United States)

    Lemmen, J G; Pinborg, A; Rasmussen, S; Ziebe, S

    2014-10-10

    Is there a difference in birthweight distribution in ART singletons born after IVF culture in two different culture media? There is no effect of culture media on both crude and adjusted birthweight distributions in ART singletons from nulliparous mothers. Studies on human ART singletons have reported a difference in birthweight in singletons following IVF culture in different culture media. However, other studies comparing different culture media have not shown any significant differences in birthweight. This study was a retrospective comparison of birthweights in IVF/ICSI singletons conceived after fresh embryo transfer following embryo culture in Cook or Medicult medium and in a national cohort of naturally conceived singletons in nulliparous women. The study compares four independent groups consisting of singletons in nulliparous women from Cook-d2: 2-day culture in Cook medium at Rigshospitalet (n = 974), Medicult-d2: 2-day culture in Medicult EmbryoAssist medium at Rigshospitalet (n = 147), Medicult-d3: 3-day culture in Medicult EmbryoAssist medium with and without added GM-CSF (n = 204), and DK: pregnancies from the Danish birth registry (n = 106842). The study compares the birthweights of singletons from nulliparous women in the four independent groups mentioned above; Cook-d2: Medicult-d2: Medicult-d3: and DK. In addition, distributions of large and small for gestational age infants were compared between the groups and a multiple linear regression analysis was used to determine which factors determined birthweight. We found no significant difference in the crude birthweight distributions between singletons born after culture in Cook-d2 or Medicult-groups. Singleton girls from the Cook-d2 group weighed 3302 ± 28 g, versus 3252 ± 76 in the Medicult-d2 group (difference 50 g; P = 0.547). Singleton boys from the Cook-d2 group weighed 3430 ± 27 g, versus 3354 ± 56 in the Medicult-d2 group (difference 76 g; P = 0.279). In the background population, mean

  9. Shear heating in creeping faults changes the onset of convection

    Science.gov (United States)

    Tung, R.; Poulet, T.; Alevizos, S.; Veveakis, E.; Regenauer-Lieb, K.

    2017-10-01

    The interaction between mechanical deformation of creeping faults and fluid flow in porous media has an important influence on the heat and mass transfer processes in Earth sciences. Creeping faults can act as heat sources due to the effect of shear heating and as such could be expected to alter the conditions for hydrothermal convection. In this work, we provide a finite element-based numerical framework developed to resolve the problem of heat and mass transfer in the presence of creeping faults. This framework extends the analytical approach of the linear stability analysis (LSA) frequently used to determine the bifurcation criterion for onset of convection, allowing us to study compressible cases with the option of complex geometry and/or material inhomogeneities. We demonstrate the impact of creeping faults on the onset of convection and show that shear heating—expressed through its dimensionless group the Gruntfest number Gr—has exponential influence on the critical value of the Lewis number Le (inversely proportional to the Rayleigh number Ra) required for convection: Lec ˜ Lec0 eGr. In this expression, Lec0 is the critical value of Le in the absence of shear heating. This exponential scaling shows that shear heating increases the critical Lewis number and triggers hydrothermal convection at lower permeability than in situations without it. We also show that the effect of shear heating in a fault significantly alters the pattern of convection in and around the fault zone.

  10. Using pattern recognition to infer parameters governing mantle convection

    Science.gov (United States)

    Atkins, Suzanne; Valentine, Andrew P.; Tackley, Paul J.; Trampert, Jeannot

    2016-08-01

    The results of mantle convection simulations are fully determined by the input parameters and boundary conditions used. These input parameters can be for initialisation, such as initial mantle temperature, or can be constant values, such as viscosity exponents. However, knowledge of Earth-like values for many input parameters are very poorly constrained, introducing large uncertainties into the simulation of mantle flow. Convection is highly non-linear, therefore linearised inversion methods cannot be used to recover past configurations over more than very short periods of time, which makes finding both initial and constant simulation input parameters very difficult. In this paper, we demonstrate a new method for making inferences about simulation input parameters from observations of the mantle temperature field after billions of years of convection. The method is fully probabilistic. We use prior sampling to construct probability density functions for convection simulation input parameters, which are represented using neural networks. Assuming smoothness, we need relatively few samples to make inferences, making this approach much more computationally tractable than other probabilistic inversion methods. As a proof of concept, we show that our method can invert the amplitude spectra of temperature fields from 2D convection simulations, to constrain yield stress, surface reference viscosity and the initial thickness of primordial material at the CMB, for our synthetic test cases. The best constrained parameter is yield stress. The reference viscosity and initial thickness of primordial material can also be inferred reasonably well after several billion years of convection.

  11. Facilitating atmosphere oxidation through mantle convection

    Science.gov (United States)

    Lee, K. K. M.; Gu, T.; Creasy, N.; Li, M.; McCammon, C. A.; Girard, J.

    2017-12-01

    Earth's mantle connects the surface with the deep interior through convection, and the evolution of its redox state will affect the distribution of siderophile elements, recycling of refractory isotopes, and the oxidation state of the atmosphere through volcanic outgassing. While the rise of oxygen in the atmosphere, i.e., the Great Oxidation Event (GOE) occurred 2.4 billion years ago (Ga), multiple lines of evidence point to oxygen production in the atmosphere well before 2.4 Ga. In contrast to the fluctuations of atmospheric oxygen, vanadium in Archean mantle lithosphere suggests that the mantle redox state has been constant for 3.5 Ga. Indeed, the connection between the redox state of the deep Earth and the atmosphere is enigmatic as is the effect of redox state on mantle dynamics. Here we show a redox-induced density contrast affects mantle convection and may potentially cause the oxidation of the upper mantle. We compressed two synthetic enstatite chondritic samples with identical bulk compositions but formed under different oxygen fugacities (fO2) to lower mantle pressures and temperatures and find Al2O3 forms its own phase separate from the dominant bridgmanite phase in the more reduced composition, in contrast to a more Al-rich, bridgmanite-dominated assemblage for a more oxidized starting composition. As a result, the reduced material is 1-1.5% denser than the oxidized material. Subsequent experiments on other plausible mantle compositions, which differ only in redox state of the starting glass materials, show similar results: distinct mineral assemblages and density contrasts up to 4%. Our geodynamic simulations suggest that such a density contrast causes a rapid ascent and accumulation of oxidized material in the upper mantle, with descent of the denser reduced material to the core-mantle boundary. The resulting heterogeneous redox conditions in Earth's interior may have contributed to the large low-shear velocity provinces in the lower mantle and the

  12. Modelling of stellar convection

    Science.gov (United States)

    Kupka, Friedrich; Muthsam, Herbert J.

    2017-07-01

    The review considers the modelling process for stellar convection rather than specific astrophysical results. For achieving reasonable depth and length we deal with hydrodynamics only, omitting MHD. A historically oriented introduction offers first glimpses on the physics of stellar convection. Examination of its basic properties shows that two very different kinds of modelling keep being needed: low dimensional models (mixing length, Reynolds stress, etc.) and "full" 3D simulations. A list of affordable and not affordable tasks for the latter is given. Various low dimensional modelling approaches are put in a hierarchy and basic principles which they should respect are formulated. In 3D simulations of low Mach number convection the inclusion of then unimportant sound waves with their rapid time variation is numerically impossible. We describe a number of approaches where the Navier-Stokes equations are modified for their elimination (anelastic approximation, etc.). We then turn to working with the full Navier-Stokes equations and deal with numerical principles for faithful and efficient numerics. Spatial differentiation as well as time marching aspects are considered. A list of codes allows assessing the state of the art. An important recent development is the treatment of even the low Mach number problem without prior modification of the basic equation (obviating side effects) by specifically designed numerical methods. Finally, we review a number of important trends such as how to further develop low-dimensional models, how to use 3D models for that purpose, what effect recent hardware developments may have on 3D modelling, and others.

  13. Convective diffusion in protein crystal growth

    Science.gov (United States)

    Baird, J. K.; Meehan, E. J.; Xidis, A. L.; Howard, S. B.

    1986-08-01

    We considered a protein crystal in the form of a flat plate suspended in its parent solution so that the normal to the largest face was perpendicular to the acceleration due to gravity. For simplicity, the protein concentration in the solution adjacent to the plate was taken to be the equilibrium solubility. The bulk of the solution was supersaturated, however, which gave rise to a horizontal concentration gradient driving fluid toward the plate. We also took into account the diffusion of the dissolved protein with respect to the moving fluid. In the boundary layer next to the plate, we solved the Navier-Stokes equation and the equation for convective diffusion to determine the flow velocity and the protein mass flux. We found that, because of the convection, the local rate of growth of the plate varied strongly with depth. The variation was diminished by a factor of 1/30 when the local gravity was reduced from g to 10 -6g as occurs aboard the Space Shuttle in earth orbit. For an aqueous solution of lysozyme at a concentration of 40 mg/ml, the boundary layer at the top of a 1 mm high crystal has a thickness of 80 μm in earths gravity and 2570 μm in 10 -6g. We examined the optical transmission of the boundary layer and compared it with the "haloes" observed by Feher et al. about growing hemispherical crystals of lysozyme.

  14. Bidispersive-inclined convection

    Science.gov (United States)

    Mulone, Giuseppe; Straughan, Brian

    2016-01-01

    A model is presented for thermal convection in an inclined layer of porous material when the medium has a bidispersive structure. Thus, there are the usual macropores which are full of a fluid, but there are also a system of micropores full of the same fluid. The model we employ is a modification of the one proposed by Nield & Kuznetsov (2006 Int. J. Heat Mass Transf. 49, 3068–3074. (doi:10.1016/j.ijheatmasstransfer.2006.02.008)), although we consider a single temperature field only. PMID:27616934

  15. An unusual case of asymptomatic hyperreactio luteinalis present at cesarean section of a spontaneous singleton pregnancy

    Directory of Open Access Journals (Sweden)

    Ahmed M. Abbas

    2017-06-01

    Full Text Available Hyperreactio Luteinalis (HL is a benign self-limited pregnancy-related condition characterized by bilateral ovarian enlargement with multiple theca lutein cysts. It is commonly associated with gestational trophoblastic diseases and multiple pregnancy. We report a rare case of HL discovered accidentally during cesarean section (CS of a spontaneously conceived normal singleton pregnancy. CS was performed due to fetal malpresentation and previously scarred uterus, and delivered a healthy male neonate. Expectant management was performed to permit conservation of both ovaries without unnecessary surgical intervention. The condition resolved within 6 weeks postpartum without adding morbidity to the patient.

  16. Convective Lyapunov spectra

    Science.gov (United States)

    Kenfack Jiotsa, Aurélien; Politi, Antonio; Torcini, Alessandro

    2013-06-01

    We generalize the concept of the convective (or velocity-dependent) Lyapunov exponent from the maximum rate Λ(v) to an entire spectrum Λ(v, n). Our results are derived by following two distinct computational protocols: (i) Legendre transform within the chronotopic approach (Lepri et al 1996 J. Stat. Phys. 82 1429); (ii) by letting evolve an ensemble of initially localized perturbations. The two approaches turn out to be mutually consistent. Moreover, we find the existence of a phase transition: above a critical value n = nc of the integrated density of exponents, the zero-velocity convective exponent is strictly smaller than the corresponding Lyapunov exponent. This phenomenon is traced back to a change of concavity of the so-called temporal Lyapunov spectrum for n > nc, which, therefore, turns out to be a dynamically invariant quantity. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Lyapunov analysis: from dynamical systems theory to applications’.

  17. Umbilical cord length in singleton gestations: a Finnish population-based retrospective register study.

    Science.gov (United States)

    Georgiadis, L; Keski-Nisula, L; Harju, M; Räisänen, S; Georgiadis, S; Hannila, M-L; Heinonen, S

    2014-04-01

    Many complications of pregnancy and delivery are associated with umbilical cord length. It is important to examine the variation in length, in order to identify normal and abnormal conditions. Moreover, the factors influencing cord growth and development are not precisely known. The main objectives were to provide updated reference charts for umbilical cord length in singleton pregnancies and to evaluate potential factors affecting cord length. Birth register data of 47,284 singleton pregnant women delivering in Kuopio University Hospital, Finland was collected prospectively. Gender-specific centile charts for cord length from 22 to 44 gestational weeks were obtained using generalized additive models for location, scale, and shape (GAMLSS). Gestational, fetal, and maternal factors were studied for their potential influence on cord length with single variable analysis and stepwise multiple linear regression analysis. Cord length increased according to gestational age, while the growth decelerated post-term. Birth weight, placental weight, pregravid maternal body mass index, parity, and maternal age correlated to cord length. Gestational diabetes and previous miscarriages were associated with longer cords, while female gender and placental abruption were associated with shorter cords. Girls had shorter cords throughout gestation although there was substantial variation in length in both genders. Cord length associated significantly with birth weight, placental weight, and gestational age. Significantly shorter cords were found in women with placental abruption. This important finding requires further investigation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  18. Reference charts and equations of fetal biometry for normal singleton pregnant women in Shaanxi, China.

    Science.gov (United States)

    Jiang, X; Zhang, Y H; Li, Y; Ma, X; Zhu, Y S H; Shang, L

    2013-01-01

    To construct reference charts and equations of fetal biometry for singleton pregnant women in Shaanxi, China. This was a cross-sectional study involving 6,832 singleton pregnant women. One set of fetal ultrasonographic measurement data between the 16th to 41st gestational weeks (GW) was randomly selected from each pregnant woman, and biparietal diameter (BPD), abdominal circumference (AC), and femur length (FL) were recorded. Mean and standard deviation (SD) of BPD, AC, and FL were fitted by polynomial. Centile = Mean + Z(alpha) x SD was used to calculate centiles. Differences in the 50th centile of BPD, AC, and FL between Hong Kong, Korean, Italian and Shaanxi fetuses were compared. Mean of BPD, AC, and FL were well-fitted by quadratic polynomial, SD of BPD, AC and FL were fitted by linear regression. Equations for estimating mean and SD for BPD, AC, and FL from GW were obtained. Centiles for BPD,AC, and FL were calculated. From the 21st GW, the differences in BPD,AC, and FL between Hong Kong, Korean, Italian, and Shaanxi fetuses became larger. Fetal biometry reference charts and equations for estimating fetal size and GW could be used in obstetrics practice and research in Shaanxi, China.

  19. Mixing in heterogeneous internally-heated convection

    Science.gov (United States)

    Limare, A.; Kaminski, E. C.; Jaupart, C. P.; Farnetani, C. G.; Fourel, L.; Froment, M.

    2017-12-01

    Past laboratory experiments of thermo chemical convection have dealt with systems involving fluids with different intrinsic densities and viscosities in a Rayleigh-Bénard setup. Although these experiments have greatly improved our understanding of the Earth's mantle dynamics, they neglect a fundamental component of planetary convection: internal heat sources. We have developed a microwave-based method in order to study convection and mixing in systems involving two layers of fluid with different densities, viscosities, and internal heat production rates. Our innovative laboratory experiments are appropriate for the early Earth, when the lowermost mantle was likely enriched in incompatible and heat producing elements and when the heat flux from the core probably accounted for a small fraction of the mantle heat budget. They are also relevant to the present-day mantle if one considers that radioactive decay and secular cooling contribute both to internal heating. Our goal is to quantify how two fluid layers mix, which is still very difficult to resolve accurately in 3-D numerical calculations. Viscosities and microwave absorptions are tuned to achieve high values of the Rayleigh-Roberts and Prandtl numbers relevant for planetary convection. We start from a stably stratified system where the lower layer has higher internal heat production and density than the upper layer. Due to mixing, the amount of enriched material gradually decreases to zero over a finite time called the lifetime. Based on more than 30 experiments, we have derived a scaling law that relates the lifetime of an enriched reservoir to the layer thickness ratio, a, to the density and viscosity contrasts between the two layers, and to their two different internal heating rates in the form of an enrichment factor beta=1+2*a*H1/H, where H1 is the heating rate of the lower fluid and H is the average heating rate. We find that the lifetime of the lower enriched reservoir varies as beta**(-7/3) in the low

  20. Elemental content of the placenta: A comparison between two high-risk obstetrical populations, adult women carrying multiples and adolescents carrying singletons.

    Science.gov (United States)

    de Angelis, Paolo; Miller, Richard K; Darrah, Thomas H; Katzman, Philip J; Pressman, Eva K; Kent, Tera R; O'Brien, Kimberly O

    2017-10-01

    The placenta is responsible for the exchange of nutrients and for preventing harmful compounds from entering the fetal circulation. With increasing industrialization, exposures to commercial and toxic metals become a concern for both pregnant women and those planning a pregnancy. The understanding of transport mechanisms and pharmacokinetics for most inorganic elements is incomplete and limited to normal term deliveries. To obtain novel data on 46 inorganic elements in placentae from two high-risk obstetric populations, women carrying multiples and adolescents carrying singletons, evaluating differences, if present, and identifying predictors of placental content. Placental tissue was collected from adolescents carrying singletons and adults carrying multiples. Elemental content was analyzed using inductively coupled plasma-mass spectrometry (ICP-MS). Multivariate regression and factor analyses were used. With the exception of Au and Pt, almost all placentae contained quantifiable concentrations of each element analyzed. All placentae contained the essential elements Ca, Fe, Mg, Se and Zn, which clustered together onto the same factor. Most elements were higher in placentae from women carrying multiples. Differences in placental content disappeared after adjusting for maternal age. Rare earth elements (REEs) clustered together and remained higher in the multiples even after adjusting for maternal age. Human placentae contain a wide range of elements, including REEs. Ranges differed considerably between cohorts. Elements with similar chemical properties, like REEs or nutritionally essential elements, clustered together. Maternal age, and therefore longer environmental exposure, was significantly associated with elevated element concentrations in the placenta. Placental concentrations of several metals that are known to be nutritionally essential (e.g., Fe, Ca, Mg, and Zn) did not differ significantly between cohorts, suggesting tight regulation, whereas

  1. Convection in porous media

    CERN Document Server

    Nield, Donald A

    1992-01-01

    This book provides a user-friendly introduction to the topic of convection in porous media The authors as- sume that the reader is familiar with the basic elements of fluid mechanics and heat transfer, but otherwise the book is self-contained The book will be useful both as a review (for reference) and as a tutorial work, suitable as a textbook in a graduate course or seminar The book brings into perspective the voluminous research that has been performed during the last two decades The field has recently exploded because of worldwide concern with issues such as energy self-sufficiency and pollution of the environment Areas of application include the insulation of buildings and equipment, energy storage and recovery, geothermal reservoirs, nuclear waste disposal, chemical reactor engineering, and the storage of heat-generating materials such as grain and coal Geophysical applications range from the flow of groundwater around hot intrusions to the stability of snow against avalanches

  2. Convection in Porous Media

    CERN Document Server

    Nield, Donald A

    2013-01-01

    Convection in Porous Media, 4th Edition, provides a user-friendly introduction to the subject, covering a wide range of topics, such as fibrous insulation, geological strata, and catalytic reactors. The presentation is self-contained, requiring only routine mathematics and the basic elements of fluid mechanics and heat transfer. The book will be of use not only to researchers and practicing engineers as a review and reference, but also to graduate students and others entering the field. The new edition features approximately 1,750 new references and covers current research in nanofluids, cellular porous materials, strong heterogeneity, pulsating flow, and more. Recognized as the standard reference in the field Includes a comprehensive, 250-page reference list Cited over 2300 times to date in its various editions Serves as an introduction for those entering the field and as a comprehensive reference for experienced researchers Features new sections on nanofluids, carbon dioxide sequestration, and applications...

  3. First trimester β-hCG and estradiol levels in singleton and twin pregnancies after assisted reproduction.

    Science.gov (United States)

    Póvoa, Ana; Xavier, Pedro; Matias, Alexandra; Blicksttein, Isaac

    2017-07-28

    To compare levels of β-hCG and estradiol collected during the first trimester in singleton and twin pregnancies following assisted reproduction technologies (ART). We prospectively evaluated 50 singleton and 47 dichorionic twin pregnancies that eventually ended in live births. Patients were recruited from a single ART center with standard treatment protocols followed by fresh embryo transfers. Hormone measurements were performed within a narrow gestational age range and analyzed in a single laboratory thus minimizing inter- and intra-assay variability. We measured serum β-hCG at 13 days after embryo transfer as well as samples of β-hCG and estradiol at 8-9 weeks+6 days. No significant differences existed between singletons and twins in respect to demographic and cycle characteristics. β-hCG and estradiol were all significantly higher in twins (PhCG and estradiol in twins, pointing to the potential role of these placental hormones in early support of a twin pregnancy.

  4. The convection patterns in microemulsions

    International Nuclear Information System (INIS)

    Korneta, W.; Lopez Quintela, M.A.; Fernandez Novoa, A.

    1991-07-01

    The Rayleigh-Benard convection in the microemulsion consisting of water (7.5%), cyclohexan (oil-61.7%) and diethylenglycolmonobutylether (surfactant-30.8%) is studied from the onset of convection to the phase separation. The five classes of convection patterns are observed and recorded on the video: localized travelling waves, travelling waves, travelling waves and localized steady rolls, steady rolls and steady polygons. The Fourier transforms and histograms of these patterns are presented. The origin of any pattern is discussed. The intermittent behaviour close to the phase separation was observed. Possible applications of the obtained results are suggested. (author). 6 refs, 4 figs

  5. Convection-enhanced water evaporation

    Directory of Open Access Journals (Sweden)

    B. M. Weon

    2011-03-01

    Full Text Available Water vapor is lighter than air; this can enhance water evaporation by triggering vapor convection but there is little evidence. We directly visualize evaporation of nanoliter (2 to 700 nL water droplets resting on silicon wafer in calm air using a high-resolution dual X-ray imaging method. Temporal evolutions of contact radius and contact angle reveal that evaporation rate linearly changes with surface area, indicating convective (instead of diffusive evaporation in nanoliter water droplets. This suggests that convection of water vapor would enhance water evaporation at nanoliter scales, for instance, on microdroplets or inside nanochannels.

  6. Analysis of intracranial hemorrhage grade in preterm singleton pregnancies delivered vaginally or by cesarean section

    Directory of Open Access Journals (Sweden)

    Ljuština Saša

    2013-01-01

    Full Text Available Background/Aim. Preterm birth is the leading cause of neonatal mortality. Periventricular hemorrhage-intraventricular hemorrhage (PVH-IVH remains a significant cause of both morbidity and mortality in infants prematurely born. The aim of the study was to evaluate the perinatal outcome regarding IVH of premature babies according to the mode of delivery. Methods. A total of 126 women in preterm singleton pregnancies with vertex presentation and 126 neonates weighted from 750 g to 1,500 g at birth were enrolled. The outcomes of 64 neonates born vaginally were compared to 62 neonates born by cesarean section. Results. There was no significant difference in the incidence of IVH among both groups. Conclusion. Our data is consistent with the hypothesis that the mode of delivery does not influence IVH and consenquently perinatal outcome in preterm neonates.

  7. Excess Mortality in Patients Diagnosed With Hypothyroidism: A Nationwide Cohort Study of Singletons and Twins

    Science.gov (United States)

    Thvilum, Marianne; Brandt, Frans; Almind, Dorthe; Christensen, Kaare; Brix, Thomas Heiberg

    2013-01-01

    Background: Although hypothyroidism is associated with increased morbidity, an association with increased mortality is still debated. Our objective was to investigate, at a nationwide level, whether a diagnosis of hypothyroidism influences mortality. Methods: In an observational cohort study from January 1, 1978 until December 31, 2008 using record-linkage data from nationwide Danish health registers, 3587 singletons and 682 twins diagnosed with hypothyroidism were identified. Hypothyroid individuals were matched 1:4 with nonhypothyroid controls with respect to age and gender and followed over a mean period of 5.6 years (range 0–30 years). The hazard ratio (HR) for mortality was calculated using Cox regression analyses. Comorbidity was evaluated using the Charlson score (CS). Results: In singletons with hypothyroidism, the mortality risk was increased (HR 1.52; 95% confidence interval [CI]: 1.41–1.65). Although the effect attenuated, hypothyroidism remained associated with increased mortality when evaluating subjects with a CS = 0 (HR 1.23; 95% CI: 1.05–1.44). In twin pairs discordant for hypothyroidism, the hypothyroid twin had excess mortality compared with the corresponding euthyroid cotwin (HR 1.40; 95% CI 0.95–2.05). However, after stratifying for zygosity, hypothyroidism was associated with excess mortality in dizygotic twin pairs (HR 1.61; 95% CI 1.00–2.58), whereas the association attenuated in monozygotic pairs (HR 1.06; 95% CI 0.55–2.05). Conclusions: Hypothyroidism is associated with an excess mortality of around 50%, which to some degree is explained by comorbidity. In addition, the finding of an association between hypothyroidism and mortality within disease discordant dizygotic but not monozygotic twin pairs indicates that the association between hypothyroidism and mortality is also influenced by genetic confounding. PMID:23365121

  8. Deep Convection in the Ocean

    National Research Council Canada - National Science Library

    McWilliams, James

    1999-01-01

    ... mechanism of water mass transformation. The resultant newly mixed deep water masses form a component of the thermohaline circulation, and hence it is essential to understand the deep convection process if the variability of the meridional...

  9. Convective heat flow probe

    Science.gov (United States)

    Dunn, James C.; Hardee, Harry C.; Striker, Richard P.

    1985-01-01

    A convective heat flow probe device is provided which measures heat flow and fluid flow magnitude in the formation surrounding a borehole. The probe comprises an elongate housing adapted to be lowered down into the borehole; a plurality of heaters extending along the probe for heating the formation surrounding the borehole; a plurality of temperature sensors arranged around the periphery of the probe for measuring the temperature of the surrounding formation after heating thereof by the heater elements. The temperature sensors and heater elements are mounted in a plurality of separate heater pads which are supported by the housing and which are adapted to be radially expanded into firm engagement with the walls of the borehole. The heat supplied by the heater elements and the temperatures measured by the temperature sensors are monitored and used in providing the desired measurements. The outer peripheral surfaces of the heater pads are configured as segments of a cylinder and form a full cylinder when taken together. A plurality of temperature sensors are located on each pad so as to extend along the length and across the width thereof, with a heating element being located in each pad beneath the temperature sensors. An expansion mechanism driven by a clamping motor provides expansion and retraction of the heater pads and expandable packer-type seals are provided along the probe above and below the heater pads.

  10. Convection-enhanced water evaporation

    OpenAIRE

    B. M. Weon; J. H. Je; C. Poulard

    2011-01-01

    Water vapor is lighter than air; this can enhance water evaporation by triggering vapor convection but there is little evidence. We directly visualize evaporation of nanoliter (2 to 700 nL) water droplets resting on silicon wafer in calm air using a high-resolution dual X-ray imaging method. Temporal evolutions of contact radius and contact angle reveal that evaporation rate linearly changes with surface area, indicating convective (instead of diffusive) evaporation in nanoliter water droplet...

  11. Plasma convection in the magnetotail lobes: statistical results from Cluster EDI measurements

    Directory of Open Access Journals (Sweden)

    S. Haaland

    2008-08-01

    Full Text Available A major part of the plasma in the Earth's magnetotail is populated through transport of plasma from the solar wind via the magnetotail lobes. In this paper, we present a statistical study of plasma convection in the lobes for different directions of the interplanetary magnetic field and for different geomagnetic disturbance levels. The data set used in this study consists of roughly 340 000 one-minute vector measurements of the plasma convection from the Cluster Electron Drift Instrument (EDI obtained during the period February 2001 to June 2007. The results show that both convection magnitude and direction are largely controlled by the interplanetary magnetic field (IMF. For a southward IMF, there is a strong convection towards the central plasma sheet with convection velocities around 10 km s−1. During periods of northward IMF, the lobe convection is almost stagnant. A By dominated IMF causes a rotation of the convection patterns in the tail with an oppositely directed dawn-dusk component of the convection for the northern and southern lobe. Our results also show that there is an overall persistent duskward component, which is most likely a result of conductivity gradients in the footpoints of the magnetic field lines in the ionosphere.

  12. Theory of Earth

    Science.gov (United States)

    Anderson, D. L.

    2014-12-01

    Earth is an isolated, cooling planet that obeys the 2nd law. Interior dynamics is driven from the top, by cold sinking slabs. High-resolution broad-band seismology and geodesy has confirmed that mantle flow is characterized by narrow downwellings and ~20 broad slowly rising updrafts. The low-velocity zone (LVZ) consists of a hot melange of sheared peridotite intruded with aligned melt-rich lamellae that are tapped by intraplate volcanoes. The high temperature is a simple consequence of the thermal overshoot common in large bodies of convecting fluids. The transition zone consists of ancient eclogite layers that are displaced upwards by slabs to become broad passive, and cool, ridge feeding updrafts of ambient mantle. The physics that is overlooked in canonical models of mantle dynamics and geochemistry includes; the 2nd law, convective overshoots, subadiabaticity, wave-melt interactions, Archimedes' principle, and kinetics (rapid transitions allow stress-waves to interact with melting and phase changes, creating LVZs; sluggish transitions in cold slabs keep eclogite in the TZ where it warms up by extracting heat from mantle below 650 km, creating the appearance of slab penetration). Canonical chemical geodynamic models are the exact opposite of physics and thermodynamic based models and of the real Earth. A model that results from inverting the assumptions regarding initial and boundary conditions (hot origin, secular cooling, no external power sources, cooling internal boundaries, broad passive upwellings, adiabaticity and whole-mantle convection not imposed, layering and self-organization allowed) results in a thick refractory-yet-fertile surface layer, with ancient xenoliths and cratons at the top and a hot overshoot at the base, and a thin mobile D" layer that is an unlikely plume generation zone. Accounting for the physics that is overlooked, or violated (2nd law), in canonical models, plus modern seismology, undermines the assumptions and conclusions of these

  13. A comparison of perinatal outcomes in singletons and multiples born after IVF or ICSI, stratified for neonatal risk criteria

    NARCIS (Netherlands)

    van Heesch, Mirjam M. J.; Evers, Johannes L. H.; Dumoulin, John C. M.; van der Hoeven, Mark A. H. B. M.; van Beijsterveldt, Catharina E. M.; Bonsel, Gouke J.; Dykgraaf, Ramon H. M.; van Goudoever, Johannes B.; Koopman-Esseboom, Corine; Nelen, Willianne L. D. M.; Steiner, Katerina; Tamminga, Pieter; Tonch, Nino; van Zonneveld, Piet; Dirksen, Carmen D.

    2014-01-01

    To compare perinatal singleton and multiple outcomes in a large Dutch in-vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) population and within risk subgroups. Newborns were assigned to a risk category based on gestational age, birthweight, Apgar score and congenital malformation.

  14. Can early ultrasonography explain the lower miscarriage rates in twin as compared to singleton pregnancies following assisted reproduction?

    Science.gov (United States)

    Póvoa, Ana; Matias, Alexandra; Xavier, Pedro; Blickstein, Isaac

    2017-06-20

    To compare first trimester 2D conventional and 3D power Doppler angiography measures in twins and singletons following assisted reproduction. We prospectively evaluated 50 singleton and 47 twin pregnancies that eventually ended in live births. Patients were recruited from a single assisted reproductive technology (ART) center with standard treatment protocols. Obstetric ultrasound was performed at 8-9 weeks +6 days. Intervillous flow, uteroplacental circulation and uterine artery pulsatility (PI) and resistance index (RI) using two-dimensional (2D) ultrasound examination were evaluated. Using three-dimensional (3D) power Doppler angiography, placental volume and the 3D power Doppler indices from the intervillous and uteroplacental circulation were calculated. Demographic and cycle characteristics were similar in mothers of singletons and twins. Placental volume was significantly (1.6-fold) larger in twins. Vascular density and blood perfusion in the intervillous space were lower in twins. The comparison of the other parameters did not show significant differences between singletons and twins. The data confirm the larger placental volume in twins, denoting a probable higher production of placental hormones that would support an early twin pregnancy. The lower vascular density and blood perfusion in the intervillous space in twins may also confer a reproductive advantage to them.

  15. Differences in outcome between twins and singletons born very preterm: results from a population-based European cohort.

    NARCIS (Netherlands)

    Papiernik, E.; Zeitlin, J.; Delmas, D.; Blondel, B.; Kunzel, W.; Cuttini, M.; Weber, T.; Petrou, S.; Gortner, L.; Kollee, L.A.A.; Draper, E.S.

    2010-01-01

    BACKGROUND: About 10% of twins are born before 32 weeks of gestation and very preterm birth rates are increasing. Preterm twins tend to have more favourable outcomes than singletons of the same gestational age, but fewer data are available for very preterm infants. This study aims to determine

  16. Prevalence of impaired glucose tolerance and other types of dysglycaemia among young twins and singletons in Guinea-Bissau

    DEFF Research Database (Denmark)

    Egegaard Hennild, Ditte; Bjerregaard-Andersen, Morten; Joaquím, Luis Carlos

    2016-01-01

    BACKGROUND: Twins may be at increased risk of dysglycaemic disorders due to adverse fetal conditions. Data from Africa regarding this association is limited. We studied impaired glucose tolerance (IGT) and other types of dysglycemia among twins and singletons in Guinea-Bissau. METHODS: The study...

  17. Impact of obstetric history on the risk of spontaneous preterm birth in singleton and multiple pregnancies: a systematic review

    NARCIS (Netherlands)

    Kazemier, B. M.; Buijs, P. E.; Mignini, L.; Limpens, J.; de Groot, C. J. M.; Mol, B. W. J.; von Dadelszen, P.; Magee, L.; Sawchuck, D.; Gao, E.; Oude Rengerink, K.; Zamora, J.; Fox, C.; Daniels, J.; Khan, K. S.; Thangaratinam, S.; Meads, C.

    2014-01-01

    Information about the recurrence of spontaneous preterm birth in subsequent twin/singleton pregnancies is scattered. To quantify the risk of recurrence of spontaneous preterm birth in different subtypes of subsequent pregnancies. An electronic literature search in OVID MEDLINE and EMBASE,

  18. The Oscillatory Nature of Rotating Convection in Liquid Metal

    Science.gov (United States)

    Aurnou, J. M.; Bertin, V. L.; Grannan, A. M.

    2016-12-01

    Earth's magnetic field is assumed to be generated by fluid motions in its liquid metal core. In this fluid, the heat diffuses significantly more than momentum and thus, the ratio of these two diffusivities, the Prandtl number Pr=ν/Κ, is well below unity. The convective flow dynamics of liquid metal is very different from Pr ≈ 1 fluids like water and those used in current dynamo simulations. In order to characterize rapidly rotating thermal convection in low Pr number fluids, we have performed laboratory experiments in a cylinder using liquid gallium (Pr ≈ 0.023) as the working fluid. The Ekman number, which characterizes the effect of rotation, varies from E = 4 10-5 to 4 10-6 and the dimensionless buoyancy forcing (Rayleigh number, Ra) varies from Ra =3 105 to 2 107. Using heat transfer measurements (Nusselt number, Nu) as well as temperature measurements within the fluid, we characterize the different styles of low Pr rotating convective flow. The convection threshold is first overcome in the form of a container scale inertial oscillatory mode. At stronger forcing, wall-localized modes are identified for the first time in liquid metal laboratory experiments. These wall modes coexist with the bulk inertial oscillatory modes. When the strengh of the buoyancy increases, the bulk flow becomes turbulent while the wall modes remain. Our results imply that rotating convective flows in liquid metals do not develop in the form of quasi-steady columns, as in Pr ≈ 1 dynamo models, but in the form of oscillatory motions. Therefore, the flows that drive thermally-driven dynamo action in low Pr geophysical and astrophysical fluids can differ substantively than those occuring in current-day Pr ≈ 1 numerical models. In addition, our results suggest that relatively low wavenumber, wall-attached modes may be dynamically important in rapidly-rotating convection in liquid metals.

  19. High accuracy mantle convection simulation through modern numerical methods

    KAUST Repository

    Kronbichler, Martin

    2012-08-21

    Numerical simulation of the processes in the Earth\\'s mantle is a key piece in understanding its dynamics, composition, history and interaction with the lithosphere and the Earth\\'s core. However, doing so presents many practical difficulties related to the numerical methods that can accurately represent these processes at relevant scales. This paper presents an overview of the state of the art in algorithms for high-Rayleigh number flows such as those in the Earth\\'s mantle, and discusses their implementation in the Open Source code Aspect (Advanced Solver for Problems in Earth\\'s ConvecTion). Specifically, we show how an interconnected set of methods for adaptive mesh refinement (AMR), higher order spatial and temporal discretizations, advection stabilization and efficient linear solvers can provide high accuracy at a numerical cost unachievable with traditional methods, and how these methods can be designed in a way so that they scale to large numbers of processors on compute clusters. Aspect relies on the numerical software packages deal.II and Trilinos, enabling us to focus on high level code and keeping our implementation compact. We present results from validation tests using widely used benchmarks for our code, as well as scaling results from parallel runs. © 2012 The Authors Geophysical Journal International © 2012 RAS.

  20. Mid-pregnancy, perinatal, and neonatal reproductive endocrinology: a prospective cohort study in twins and singleton control subjects.

    Science.gov (United States)

    Kuijper, Esther A M; Twisk, Jos W R; Korsen, Ted; Caanen, Mirte R; Kushnir, Mark M; Rockwood, Alan L; Meikle, A Wayne; Hompes, Peter G; Wit, Jan M; Lambalk, Cornelis B

    2015-12-01

    To answer the questions: Are perinatal reproductive hormone profiles different in case of a twin compared with a singleton pregnancy? Are reproductive endocrine profiles of twin girls influenced by their male co-twin and vice versa? Prospective cohort study from January 2004 to October 2009. Not applicable. A total of 204 mothers of twins and 248 singleton control subjects, aged >18 years, pregnant with a twin or singleton and no endocrine disease or malignancy. Blood samples were collected at mid-gestation from the mother and at delivery from the mothers and the umbilical cords. Estrogens, androgens, sex hormone-binding globulin, progesterone, and gonadotropins were measured. Hormonal profiles were compared between singletons and twins, different types of twins, and opposite-sex and same-sex twins. Estrogen and progesterone concentrations were higher in mothers of twins compared with singletons, but twin babies had lower estrogen and progesterone concentrations at birth. Opposite-sex twin girls did not have higher androgens in cord blood compared with same-sex twin girls. Boys of an opposite-sex twin had lower luteinizing hormone concentrations compared with dizygotic twin boys with a brother as a co-twin. Children from a twin are not overexposed to sex steroids at the time of birth, despite higher concentrations in their mothers, and girls from opposite sex twins do not show androgenic influences from their male co-twin. The female co-twin may influence the hypothalamic-pituitary-testicular axis of her brother via central inhibition. Copyright © 2015 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

  1. How the cervix shortens: an anatomic study using 3-dimensional transperineal sonography and image registration in singletons and twins.

    Science.gov (United States)

    Parikh, Reshma; Patel, Atur; Stack, Trevor; Socrate, Simona; House, Michael

    2011-09-01

    The purpose of this study was to use a fixed reference to study movement (displacement) of the cervical internal os from the second to the third trimester in singletons and twins. The rationale was to gain insight into anatomic changes associated with cervical shortening. For each patient, 2 transperineal scans were performed 12 weeks apart (20 and 32 weeks). The internal os and symphysis pubis were visualized in the same field of view. Image registration techniques were used to align the 2 scans using the symphysis as a fixed reference. Total displacement, anterior displacement, and inferior displacement of the internal os were measured. Displacements were correlated with cervical shortening. Bland-Altman plots and interobserver intraclass correlation coefficients were calculated. A total of 42 healthy participants were studied: 28 with singletons and 14 with twins. The mean ± SD values for total displacement were 2.1 ± 1.2 and 2.0 ± 1.2 cm for singletons and twins, respectively (P = .75). The direction of displacement was significantly different. The mean anterior displacement was 1.1 cm greater for singletons than for twins (95% confidence interval, 0.29-2.0 cm, P = .01). Mean inferior displacement was 1.3 cm greater for twins than for singletons (95% confidence interval, 2.2-0.1 cm; P = .03). Only inferior displacement correlated with cervical shortening (P < .001; R(2) = 0.74). For every 2.2 cm of inferior displacement, the cervix shortened 1.0 cm. Assessments of reliability showed good agreement between 2 observers. The anatomic position of the internal cervical os depends on gestational age and fetal number. Cervical shortening correlated most strongly with inferior displacement.

  2. Long-term preservation of early formed mantle heterogeneity by mobile lid convection: Importance of grainsize evolution

    Science.gov (United States)

    Foley, Bradford J.; Rizo, Hanika

    2017-10-01

    The style of tectonics on the Hadean and Archean Earth, particularly whether plate tectonics was in operation or not, is debated. One important, albeit indirect, constraint on early Earth tectonics comes from observations of early-formed geochemical heterogeneities: 142Nd and 182W anomalies recorded in Hadean to Phanerozoic rocks from different localities indicate that chemically heterogeneous reservoirs, formed during the first ∼500 Myrs of Earth's history, survived their remixing into the mantle for over 1 Gyrs. Such a long mixing time is difficult to explain because hotter mantle temperatures, expected for the early Earth, act to lower mantle viscosity and increase convective vigor. Previous studies found that mobile lid convection typically erases heterogeneity within ∼100 Myrs under such conditions, leading to the hypothesis that stagnant lid convection on the early Earth was responsible for the observed long mixing times. However, using two-dimensional Cartesian convection models that include grainsize evolution, we find that mobile lid convection can preserve heterogeneity at high mantle temperature conditions for much longer than previously thought, because higher mantle temperatures lead to larger grainsizes in the lithosphere. These larger grainsizes result in stronger plate boundaries that act to slow down surface and interior convective motions, in competition with the direct effect temperature has on mantle viscosity. Our models indicate that mobile lid convection can preserve heterogeneity for ≈0.4-1 Gyrs at early Earth mantle temperatures when the initial heterogeneity has the same viscosity as the background mantle, and ≈1-4 Gyrs when the heterogeneity is ten times more viscous than the background mantle. Thus, stagnant lid convection is not required to explain long-term survival of early formed geochemical heterogeneities, though these heterogeneities having an elevated viscosity compared to the surrounding mantle may be essential for their

  3. Effect of Body Mass Index on pregnancy outcomes in nulliparous women delivering singleton babies

    Directory of Open Access Journals (Sweden)

    Liston William A

    2007-07-01

    Full Text Available Abstract Background The increasing prevalence of obesity in young women is a major public health concern. These trends have a major impact on pregnancy outcomes in these women, which have been documented by several researchers. In a population based cohort study, using routinely collected data, this paper examines the effect of increasing Body Mass Index (BMI on pregnancy outcomes in nulliparous women delivering singleton babies. Methods This was a retrospective cohort study, based on all nulliparous women delivering singleton babies in Aberdeen between 1976 and 2005. Women were categorized into five groups – underweight (BMI 2, normal (BMI 20 – 24.9 Kg/m2 overweight (BMI 25 – 29.9 Kg/m2, obese (BMI 30 – 34.9 Kg/m2 and morbidly obese (BMI > 35 Kg/m2. Obstetric and perinatal outcomes were compared by univariate and multivariate analyses. Results In comparison with women of BMI 20 – 24.9, morbidly obese women faced the highest risk of pre-eclampsia {OR 7.2 (95% CI 4.7, 11.2} and underweight women the lowest {OR 0.6 (95% CI 0.5, 0.7}. Induced labour was highest in the morbidly obese {OR 1.8 (95% CI 1.3, 2.5} and lowest in underweight women {OR 0.8 (95% CI 0.8, 0.9}. Emergency Caesarean section rates were highest in the morbidly obese {OR 2.8 (95% CI 2.0, 3.9}, and comparable in women with normal and low BMI. Obese women were more likely to have postpartum haemorrhage {OR 1.5 (95% CI 1.3, 1.7} and preterm delivery ( 4,000 g was in the morbidly obese {OR 2.1 (95% CI 1.3, 3.2} and the lowest in underweight women {OR 0.5 (95% CI 0.4, 0.6}. Conclusion Increasing BMI is associated with increased incidence of pre-eclampsia, gestational hypertension, macrosomia, induction of labour and caesarean delivery; while underweight women had better pregnancy outcomes than women with normal BMI.

  4. Pitfalls in modeling mantle convection with internal heat production

    Science.gov (United States)

    Korenaga, Jun

    2017-05-01

    The mantle of the Earth, and probably of other terrestrial planets as well, is heated from below and within. The heating mode of mantle convection is thus mixed heating, and it is also time dependent because the amount of heat-producing isotopes in the mantle is steadily decreasing by radioactive decay and because the basal heat flux originating in the cooling of the core can vary with time. This mode of transient mixed heating presents its own challenges to the study of mantle convection, but such difficulties are not always appreciated in the recent literature. The purpose of this tutorial is to clarify the issue of heating mode by explaining relevant concepts in a coherent manner, including the internal heating ratio, the Urey ratio, secular cooling, and the connection between the thermal budget of the Earth and the geochemical models of the Earth. The importance of such basic concepts will be explained with some illustrative examples in the context of the thermal evolution of the Earth, and a summary of common pitfalls will be provided, with a possible strategy for how to avoid them.

  5. Divergence of estimated fetal weight and birth weight in singleton fetuses.

    Science.gov (United States)

    Sotiriadis, Alexandros; Eleftheriades, Makarios; Papadopoulos, Vassileios; Sarafidis, Kosmas; Pervanidou, Panagiota; Assimakopoulos, Efstratios

    2018-03-01

    To evaluate differences in distribution of estimated fetal weight (EFW) and birth weight (BW) of ongoing fetuses and neonates of the same gestational age. Reference curves for EFW (Hadlock BPD-HC-AC-FL formula, N = 1191) and BW (N = 1036) in singleton pregnancies from 24 +0 to 40 +6 gestational weeks were calculated. Multiple pregnancies, fetuses with major or multiple abnormalities or syndromes and iatrogenic preterm deliveries due to preeclampsia or abnormal fetal Doppler were excluded. The standardized residuals for EFW and BW were calculated and compared. EFW and BW can be accurately described by quadratic equations (R 2  = 0.944 and 0.807, respectively). The distribution of standardized residuals for BW using the EFW formula was negative from 28 +0 to 35 +6 weeks. The 50th and 5th centiles of BW were lower than those of EFW throughout prematurity, and they converged at approximately 38 gestational weeks. The 5th centile for BW was 30% lower than the 5th centile for EFW at 27 weeks, 27.5% lower at 30 weeks and 19.4% at 34 weeks. Preterm infants have lower BW distribution compared to the expected EFW of ongoing pregnancies of the same gestational age, supporting the concept of hidden intrauterine morbidity for a proportion of these infants.

  6. Determinants of successful breastfeeding initiation in healthy term singletons: a Swiss university hospital observational study.

    Science.gov (United States)

    Gubler, Tabea; Krähenmann, Franziska; Roos, Malgorzata; Zimmermann, Roland; Ochsenbein-Kölble, Nicole

    2013-05-01

    Breastfeeding significantly benefits mothers and infants. We aimed to identify the determinants of its successful initiation. A retrospective study of 1893 mothers delivering healthy term singletons at a Swiss university hospital from 1/2008 to 3/2009 determined the associations between multiple breastfeeding and early postpartum parameters by univariate and multiple regression analysis. Multiparity was associated with nursing exclusively at the breast at discharge (Ppacifier use (P<0.05). Among obese mothers, nursing exclusively at the breast at discharge was less frequent, and use of all feeding aids more frequent, than among normal-weight women (both P<0.001). Neuraxial anesthesia was associated with use of maltodextrin and bottle (both P<0.05) compared to no anesthesia. Delayed first skin-to-skin contact and rooming-in for <24 h/day were each associated with maltodextrin and cup (P<0.05). Nursing exclusively at the breast at discharge was less frequent (P<0.001), and bottle use more frequent (P<0.05), in women with sore nipples than in those without. Obesity is a potent inhibitor of breastfeeding initiation. Delivery without anesthesia by a multiparous normal-weight mother, followed by immediate skin-to-skin contact, rooming-in for 24 h/day, and dedicated nipple care, provides the best conditions for successful early postpartum breastfeeding without the need for feeding aids or nutritional supplements

  7. RIG-I-Like Receptor Signaling in Singleton-Merten Syndrome

    Directory of Open Access Journals (Sweden)

    Changming Lu

    2017-09-01

    Full Text Available Singleton-Merten syndrome (SMS is an autosomal dominant, multi-system innate immune disorder characterized by early and severe aortic and valvular calcification, dental and skeletal abnormalities, psoriasis, glaucoma, and other varying clinical findings. Recently we identified a specific gain-of-function mutation in IFIH1, interferon induced with helicase C domain 1, segregated with this disease. SMS disease without hallmark dental anomalies, termed atypical SMS, has recently been reported caused by variants in DDX58, DEXD/H-box helicase 58. IFIH1 and DDX58 encode retinoic acid-inducible gene I (RIG-I-like receptors family members melanoma differentiation-associated gene 5 and RIG-I, respectively. These cytosolic pattern recognition receptors function in viral RNA detection initiating an innate immune response through independent pathways that promote type I and type III interferon expression and proinflammatory cytokines. In this review, we focus on SMS as an innate immune disorder summarizing clinical features, molecular aspects of the pathogenetic pathway and discussing underlying mechanisms of the disease.

  8. Tectonic predictions with mantle convection models

    Science.gov (United States)

    Coltice, Nicolas; Shephard, Grace E.

    2018-04-01

    Over the past 15 yr, numerical models of convection in Earth's mantle have made a leap forward: they can now produce self-consistent plate-like behaviour at the surface together with deep mantle circulation. These digital tools provide a new window into the intimate connections between plate tectonics and mantle dynamics, and can therefore be used for tectonic predictions, in principle. This contribution explores this assumption. First, initial conditions at 30, 20, 10 and 0 Ma are generated by driving a convective flow with imposed plate velocities at the surface. We then compute instantaneous mantle flows in response to the guessed temperature fields without imposing any boundary conditions. Plate boundaries self-consistently emerge at correct locations with respect to reconstructions, except for small plates close to subduction zones. As already observed for other types of instantaneous flow calculations, the structure of the top boundary layer and upper-mantle slab is the dominant character that leads to accurate predictions of surface velocities. Perturbations of the rheological parameters have little impact on the resulting surface velocities. We then compute fully dynamic model evolution from 30 and 10 to 0 Ma, without imposing plate boundaries or plate velocities. Contrary to instantaneous calculations, errors in kinematic predictions are substantial, although the plate layout and kinematics in several areas remain consistent with the expectations for the Earth. For these calculations, varying the rheological parameters makes a difference for plate boundary evolution. Also, identified errors in initial conditions contribute to first-order kinematic errors. This experiment shows that the tectonic predictions of dynamic models over 10 My are highly sensitive to uncertainties of rheological parameters and initial temperature field in comparison to instantaneous flow calculations. Indeed, the initial conditions and the rheological parameters can be good enough

  9. Lightning-based propagation of convective rain fields

    Directory of Open Access Journals (Sweden)

    S. Dietrich

    2011-05-01

    Full Text Available This paper describes a new multi-sensor approach for continuously monitoring convective rain cells. It exploits lightning data from surface networks to propagate rain fields estimated from multi-frequency brightness temperature measurements taken by the AMSU/MHS microwave radiometers onboard NOAA/EUMETSAT low Earth orbiting operational satellites. Specifically, the method allows inferring the development (movement, morphology and intensity of convective rain cells from the spatial and temporal distribution of lightning strokes following any observation by a satellite-borne microwave radiometer. Obviously, this is particularly attractive for real-time operational purposes, due to the sporadic nature of the low Earth orbiting satellite measurements and the continuous availability of ground-based lightning measurements – as is the case in most of the Mediterranean region. A preliminary assessment of the lightning-based rainfall propagation algorithm has been successfully made by using two pairs of consecutive AMSU observations, in conjunction with lightning measurements from the ZEUS network, for two convective events. Specifically, we show that the evolving rain fields, which are estimated by applying the algorithm to the satellite-based rainfall estimates for the first AMSU overpass, show an overall agreement with the satellite-based rainfall estimates for the second AMSU overpass.

  10. True polar wander on convecting planets

    Science.gov (United States)

    Rose, Ian Robert

    Rotating planets are most stable when spinning around their maximum moment of inertia, and will tend to reorient themselves to achieve this configuration. Geological activity redistributes mass in the planet, making the moment of inertia a function of time. As the moment of inertia of the planet changes, the spin axis shifts with respect to a mantle reference frame in order to maintain rotational stability. This process is known as true polar wander (TPW). Of the processes that contribute to a planet's moment of inertia, convection in the mantle generates the largest and longest-period fluctuations, with corresponding shifts in the spin axis. True polar wander has been hypothesized to explain several physiographic features on planets and moons in our solar system. On Earth, TPW events have been invoked in some interpretations of paleomagnetic data. Large swings in the spin axis could have enormous ramifications for paleogeography, paleoclimate, and the history of life. Although the existence of TPW is well-verified, it is not known whether its rate and magnitude have been large enough for it to be an important process in Earth history. If true polar wander has been sluggish compared to plate tectonic speeds, then it would be difficult to detect and its consequences would be minor. I investigate rates of true polar wander on convecting planets using scaling, numerics, and inverse problems. I perform a scaling analysis of TPW on a convecting planet, identifying a minimal set of nondimensional parameters which describe the problem. The primary nondimensional numbers that control the rate of TPW are the ratio of centrifugal to gravitational forces m and the Rayleigh number Ra. The parameter m sets the size of a planet's rotational bulge, which determines the amount of work that needs to be done to move the spin axis. The Rayleigh number controls the size, distribution, and rate of change of moment of inertia anomalies, all of which affect the rate of TPW. I find that

  11. [Singleton and twin pregnancies of PKU patients - individual variability of phenylalanine tolerance: experience of a single treatment center (Preliminary report)].

    Science.gov (United States)

    Żółkowska, Joanna; Hozyasz, Kamil K; Nowacka, Maria

    2017-01-01

    Phenylketonuria (PKU) is the autosomal recessive deficiency of phenylalanine hydroxylase resulting in the accumulation of phenylalanine (Phe) in blood and in the brain. Phe restriction in a patient's diet is determined depending on the amount of Phe intake which allows for stable blood Phe levels within the therapeutic range of 120-360µmol/L. In clinical practice the empirical determination of Phe tolerance relies on frequent assessment of blood Phe concentrations in relation to Phe intake from food records. Untreated maternal PKU may lead to maternal PKU syndrome in offspring. The objective of the study was to compare Phe tolerance during the course of singleton and multiple pregnancies of PKU patients. Case subjects and methods: The cases reviewed included three sets of classical PKU-affected Polish women on a low-phenylalanine diet during the course of singleton and twin pregnancies and their PKU-unaffected newborns. All the patients were under regular supervision of a metabolic dietitian to stabilize blood Phe levels and determine Phe tolerance. Data on pregnancy weight gain, the gestational age when the diet initiated, the percent of Phe assessments 360 µmol/L, as well as offspring birth measurements were analyzed. The total increase in Phe tolerance and its pattern during the course of singleton and twin pregnancies differed remarkably in each patient. Three PKU women (Q383X/R408W, EX3DEL/EX3DEL, R281L/R408W) increased their Phe tolerance in singleton and twin pregnancies by 579%/468%, 674%/261%, and 427%/236%, respectively. During the last 10 weeks of singleton and twin pregnancy Phe tolerance showed an increase by 62%/149%, 33%/64%, and 37%/40%, respectively. The analysis of predictors for Phe tolerance showed that an individual's weight gain and the fetal weight gain as estimated from liveborn birth-weight data had no predictive capacity. Individual Phe tolerance in singleton pregnancies of PKU patients does not predict tolerance in twin pregnancy

  12. A stochastic parameterization for deep convection using cellular automata

    Science.gov (United States)

    Bengtsson, L.; Steinheimer, M.; Bechtold, P.; Geleyn, J.

    2012-12-01

    large-scale variables in regions where convective activity is large. A two month extended evaluation of the deterministic behaviour of the scheme indicate a neutral impact on forecast skill. References: Bengtsson, L., H. Körnich, E. Källén, and G. Svensson, 2011: Large-scale dynamical response to sub-grid scale organization provided by cellular automata. Journal of the Atmospheric Sciences, 68, 3132-3144. Frenkel, Y., A. Majda, and B. Khouider, 2011: Using the stochastic multicloud model to improve tropical convective parameterization: A paradigm example. Journal of the Atmospheric Sciences, doi: 10.1175/JAS-D-11-0148.1. Huang, X.-Y., 1988: The organization of moist convection by internal 365 gravity waves. Tellus A, 42, 270-285. Khouider, B., J. Biello, and A. Majda, 2010: A Stochastic Multicloud Model for Tropical Convection. Comm. Math. Sci., 8, 187-216. Palmer, T., 2011: Towards the Probabilistic Earth-System Simulator: A Vision for the Future of Climate and Weather Prediction. Quarterly Journal of the Royal Meteorological Society 138 (2012) 841-861 Plant, R. and G. Craig, 2008: A stochastic parameterization for deep convection based on equilibrium statistics. J. Atmos. Sci., 65, 87-105.

  13. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science. M Venkat Ratnam. Articles written in Journal of Earth System Science. Volume 120 Issue 5 October 2011 pp 807-823. Long-term variations in outgoing long-wave radiation (OLR), convective available potential energy (CAPE) and temperature in the tropopause region over ...

  14. ENVIRONMENTAL ASPECTS OF THE INTENSIFICATION CONVECTIVE DRYING

    Directory of Open Access Journals (Sweden)

    A. M. Gavrilenkov

    2012-01-01

    Full Text Available Identified and analyzed the relationship of the intensity convective drying and air pollution emissions of heat. The ways to reduce the thermal pollution of the atmosphere at convective drying.

  15. Critical stability of almost adiabatic convection in a rapidly rotating thick spherical shell

    Energy Technology Data Exchange (ETDEWEB)

    Starchenko, S. V., E-mail: sstarchenko@mail.ru [Russian Academy of Sciences, Institute of Terrestrial Magnetism, the Ionosphere, and Radiowave Propagation (Russian Federation); Kotelnikova, M. S. [Lavrentyev Institute of Hydrodynamics (Russian Federation)

    2013-02-15

    In this work, the convection equations in the almost adiabatic approximation is studied for which the choice of physical parameters is primarily based on possible applications to the hydrodynamics of the deep interiors of the Earth and planets and moons of the terrestrial group. The initial system of partial differential equations (PDEs) was simplified to a single second-order ordinary differential equation for the pressure or vertical velocity component to investigate the linear stability of convection. The critical frequencies, modified Rayleigh numbers, and distributions of convection are obtained at various possible Prandtl numbers and in different thick fluid shells. An analytical WKB-type solution was obtained for the case when the inner radius of the shell is much smaller than the outer radius and convective sources are concentrated along the inner boundary.

  16. Damping of Solute Convection During Crystal Growth by Applying Magnetic Field Gradients

    Science.gov (United States)

    Wakayama, Nobuko I.

    2005-06-01

    One of the advantages of crystal growth under microgravity conditions is the damping of solute convection that affects crystal quality. The mechanism of the dampening effect of magnetic field gradients, B(dB/dz), on solute convection was studied, and the magnitude of B(dB/dz) required for dampening was calculated. When the absolute value of mass magnetic susceptibility, χg, of a solute is about 70% of that of a solvent (e.g., KCl crystal growth from an aqueous solution) and the weight ratio is 0.26, the gradient to damp convection considerably is estimated to be -3018 T2/m. On the other hand, when the χg of the solute is nearly equal to that of the solvent [protein crystal growth (lysozyme)], a gradient of -1394 T2/m damps convection completely on the earth.

  17. On the Existence of Oscillatory-Convective Thermohaline Flow in Sedimentary Basins

    Science.gov (United States)

    Graf, T.; Diersch, H. G.; Simmons, C. T.

    2009-05-01

    In the Earth's crust, both groundwater temperature and salinity increase with depth. As a consequence, water density is variable, thereby creating density-driven thermohaline groundwater flow. While prior steady-state studies of thermohaline flow in porous media identified conductive, oscillatory and convective thermohaline flow modes, the present study numerically analyzes thermohaline flow using a transient approach. We discovered the existence of an oscillatory-convective flow mode within a specific range of thermal and haline Raleigh numbers. Oscillatory-convective thermohaline flow only exists when water temperature and salinity increase with depth (positive RaT, negative RaS). Candidate sedimentary basins of oscillatory-convective thermohaline flow may be found in Western Canada (Alberta), in the Gulf of Mexico, in Northern Germany, or in Australia.

  18. Solar Surface Magneto-Convection

    Directory of Open Access Journals (Sweden)

    Robert F. Stein

    2012-07-01

    Full Text Available We review the properties of solar magneto-convection in the top half of the convection zones scale heights (from 20 Mm below the visible surface to the surface, and then through the photosphere to the temperature minimum. Convection is a highly non-linear and non-local process, so it is best studied by numerical simulations. We focus on simulations that include sufficient detailed physics so that their results can be quantitatively compared with observations. The solar surface is covered with magnetic features with spatial sizes ranging from unobservably small to hundreds of megameters. Three orders of magnitude more magnetic flux emerges in the quiet Sun than emerges in active regions. In this review we focus mainly on the properties of the quiet Sun magnetic field. The Sun’s magnetic field is produced by dynamo action throughout the convection zone, primarily by stretching and twisting in the turbulent downflows. Diverging convective upflows and magnetic buoyancy carry magnetic flux toward the surface and sweep the field into the surrounding downflow lanes where the field is dragged downward. The result is a hierarchy of undulating magnetic Ω- and U-loops of different sizes. New magnetic flux first appears at the surface in a mixed polarity random pattern and then collects into isolated unipolar regions due to underlying larger scale magnetic structures. Rising magnetic structures are not coherent, but develop a filamentary structure. Emerging magnetic flux alters the convection properties, producing larger, darker granules. Strong field concentrations inhibit transverse plasma motions and, as a result, reduce convective heat transport toward the surface which cools. Being cooler, these magnetic field concentrations have a shorter scale height and become evacuated. The field becomes further compressed and can reach strengths in balance with the surrounding gas pressure. Because of their small internal density, photons escape from deeper in

  19. Stationary thermal convection in a viscoelastic ferrofluid

    Energy Technology Data Exchange (ETDEWEB)

    Laroze, D., E-mail: david.laroze@gmail.co [Max Planck Institute for Polymer Research, D 55021 Mainz (Germany); Instituto de Alta Investigacion, Universidad de Tarapaca, Casilla 7D, Arica (Chile); Martinez-Mardones, J. [Instituto de Fisica, Pontificia Universidad Catolica de Valparaiso, Casilla 4059, Valparaiso (Chile); Perez, L.M. [Departamento de Ingenieria Metalurgica, Universidad de Santiago de Chile, Av. Bernardo OHiggins 3363, Santiago (Chile); Rojas, R.G. [Instituto de Fisica, Pontificia Universidad Catolica de Valparaiso, Casilla 4059, Valparaiso (Chile)

    2010-11-15

    We report theoretical and numerical results on convection for a magnetic fluid in a viscoelastic carrier liquid. We focus in the stationary convection for idealized boundary conditions. We obtain explicit expressions of convective thresholds in terms of the control parameters of the system. Close to bifurcation, the coefficients of the corresponding amplitude equation are determined analytically. Finally, the secondary instabilities are performed.

  20. Mutations in DDX58, which Encodes RIG-I, Cause Atypical Singleton-Merten Syndrome

    Science.gov (United States)

    Jang, Mi-Ae; Kim, Eun Kyoung; Now, Hesung; Nguyen, Nhung T.H.; Kim, Woo-Jong; Yoo, Joo-Yeon; Lee, Jinhyuk; Jeong, Yun-Mi; Kim, Cheol-Hee; Kim, Ok-Hwa; Sohn, Seongsoo; Nam, Seong-Hyeuk; Hong, Yoojin; Lee, Yong Seok; Chang, Sung-A; Jang, Shin Yi; Kim, Jong-Won; Lee, Myung-Shik; Lim, So Young; Sung, Ki-Sun; Park, Ki-Tae; Kim, Byoung Joon; Lee, Joo-Heung; Kim, Duk-Kyung; Kee, Changwon; Ki, Chang-Seok

    2015-01-01

    Singleton-Merten syndrome (SMS) is an autosomal-dominant multi-system disorder characterized by dental dysplasia, aortic calcification, skeletal abnormalities, glaucoma, psoriasis, and other conditions. Despite an apparent autosomal-dominant pattern of inheritance, the genetic background of SMS and information about its phenotypic heterogeneity remain unknown. Recently, we found a family affected by glaucoma, aortic calcification, and skeletal abnormalities. Unlike subjects with classic SMS, affected individuals showed normal dentition, suggesting atypical SMS. To identify genetic causes of the disease, we performed exome sequencing in this family and identified a variant (c.1118A>C [p.Glu373Ala]) of DDX58, whose protein product is also known as RIG-I. Further analysis of DDX58 in 100 individuals with congenital glaucoma identified another variant (c.803G>T [p.Cys268Phe]) in a family who harbored neither dental anomalies nor aortic calcification but who suffered from glaucoma and skeletal abnormalities. Cys268 and Glu373 residues of DDX58 belong to ATP-binding motifs I and II, respectively, and these residues are predicted to be located closer to the ADP and RNA molecules than other nonpathogenic missense variants by protein structure analysis. Functional assays revealed that DDX58 alterations confer constitutive activation and thus lead to increased interferon (IFN) activity and IFN-stimulated gene expression. In addition, when we transduced primary human trabecular meshwork cells with c.803G>T (p.Cys268Phe) and c.1118A>C (p.Glu373Ala) mutants, cytopathic effects and a significant decrease in cell number were observed. Taken together, our results demonstrate that DDX58 mutations cause atypical SMS manifesting with variable expression of glaucoma, aortic calcification, and skeletal abnormalities without dental anomalies. PMID:25620203

  1. Intrapartum and neonatal outcomes in singleton pregnancies following conception by assisted reproduction techniques.

    Science.gov (United States)

    Rozdarz, Kellie M; Flatley, Christopher J; Kumar, Sailesh

    2017-12-01

    To characterise maternal demographics and ascertain whether clinically important differences exist in the intrapartum and neonatal outcomes associated with assisted reproductive technology (ART). A retrospective study was undertaken between January 2007 and December 2013 of all singleton pregnancies conceived via ART at a major tertiary unit in Brisbane, Australia. Intrapartum outcomes were mode of delivery and indication for emergency caesarean. Neonatal outcomes investigated were gestation at delivery, birth weight, Apgar scores, acidosis at birth, respiratory distress, need for resuscitation, admission to neonatal intensive care and stillbirth. There were 4733 (7.4%) ART and 59 277 (92.6%) spontaneous conception pregnancies. Women who conceived using ART were less likely to have a spontaneous vaginal delivery (odds ratio (OR) 0.60, 95% CI 0.57-0.64) and were more likely to require operative or assisted birth: elective caesarean (adjusted OR (aOR) 1.31, 95% CI 1.22-1.40), emergency caesarean (aOR 1.19, 95% CI 1.09-1.28), or instrumental delivery (aOR 1.45, 95% CI 1.32-1.58). Neonates who were conceived using ART were less likely to be born at term (aOR 0.64, 95% CI 0.58-0.71) and have lower birth weights. No differences were observed in rates of respiratory distress, admission to the neonatal intensive care unit, or stillbirth between the ART and spontaneous conception cohorts. The odds of neonatal acidosis (OR 0.71, 95% CI0.63-0.81) were lower in the ART cohort. Although higher rates of operative deliveries were seen for women who conceive using ART, neonatal outcomes were generally no different between the two cohorts. © 2017 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists.

  2. Abnormal human chorionic gonadotropin (hCG) trends after transfer of multiple embryos resulting in viable singleton pregnancies.

    Science.gov (United States)

    Brady, Paula C; Farland, Leslie V; Missmer, Stacey A; Racowsky, Catherine; Fox, Janis H

    2017-12-19

    The purpose of this study is to investigate whether abnormal hCG trends occur at a higher incidence among women conceiving singleton pregnancies following transfer of multiple (two or more) embryos (MET), as compared to those having a single embryo transfer (SET). Retrospective cohort study was performed of women who conceived singleton pregnancies following fresh or frozen autologous IVF/ICSI cycles with day 3 or day 5 embryo transfers between 2007 and 2014 at a single academic medical center. Cycles resulting in one gestational sac on ultrasound followed by singleton live birth beyond 24 weeks of gestation were included. Logistic regression models adjusted a priori for patient age at oocyte retrieval and day of embryo transfer were used to estimate the Odds Ratio of having an abnormal hCG rise (defined as a rise or hCG rises between the first and second measurements, compared to 2.7% (n = 17) of patients undergoing SET (OR 2.16, 95% CI 1.26-3.71). Among patients with initially abnormal hCG rises who had a third level checked (89%), three-quarters had normal hCG rises between the second and third measurements. Patients who deliver singletons following MET were more likely to have suboptimal initial hCG rises, potentially due to transient implantation of other non-viable embryo(s). While useful for counseling, these findings should not change standard management of abnormal hCG rises following IVF. The third hCG measurements may clarify pregnancy prognosis.

  3. Initiation of Plate Tectonics from Post-Magma Ocean Thermo-Chemical Convection

    OpenAIRE

    Foley, Bradford J.; Bercovici, David; Elkins-Tanton, Linda T.

    2014-01-01

    Leading theories for the presence of plate tectonics on Earth typically appeal to the role of present day conditions in promoting rheological weakening of the lithosphere. However, it is unknown whether the conditions of the early Earth were favorable for plate tectonics, or any form of subduction, and thus how subduction begins is unclear. Using physical models based on grain-damage, a grainsize-feedback mechanism capable of producing plate-like mantle convection, we demonstrate that subduct...

  4. Perinatal outcomes among singletons after assisted reproductive technology with single-embryo or double-embryo transfer versus no assisted reproductive technology.

    Science.gov (United States)

    Martin, Angela S; Chang, Jeani; Zhang, Yujia; Kawwass, Jennifer F; Boulet, Sheree L; McKane, Patricia; Bernson, Dana; Kissin, Dmitry M; Jamieson, Denise J

    2017-04-01

    To examine outcomes of singleton pregnancies conceived without assisted reproductive technology (non-ART) compared with singletons conceived with ART by elective single-embryo transfer (eSET), nonelective single-embryo transfer (non-eSET), and double-embryo transfer with the establishment of 1 (DET -1) or ≥2 (DET ≥2) early fetal heartbeats. Retrospective cohort using linked ART surveillance data and vital records from Florida, Massachusetts, Michigan, and Connecticut. Not applicable. Singleton live-born infants. None. Preterm birth (PTB Reproductive Medicine. All rights reserved.

  5. A community benchmark for viscoplastic thermal convection in a 2-D square box

    NARCIS (Netherlands)

    Tosi, N.; Stein, C.; Noack, L.; Hüttig, C.; Samuel, H.; Maierová, P.; Davies, D. R.; Wilson, C.R.; Kramer, S. C.; Thieulot, C.A.P.; Glerum, A.C.; Fraters, M.R.T.; Spakman, W.; Rozel, A.; Tackley, P.J.

    Numerical simulations of thermal convection in the Earth's mantle often employ a pseudoplastic rheology in order to mimic the plate-like behavior of the lithosphere. Yet the benchmark tests available in the literature are largely based on simple linear rheologies in which the viscosity is either

  6. Constraints on thermo-chemical convection from numerical modelling and geophysical data. Geologica Ultraectina (298)

    NARCIS (Netherlands)

    van Summeren, J.R.G.

    2008-01-01

    In modern geoscience, mounting evidence in support of large-scale lateral variations in the composition of Earth's deep mantle has fueled the debate on the structure and evolution of mantle convection. Seismological data supports the view that material transport across the mantle transition zone is

  7. A transilient matrix for moist convection

    Energy Technology Data Exchange (ETDEWEB)

    Romps, D.; Kuang, Z.

    2011-08-15

    A method is introduced for diagnosing a transilient matrix for moist convection. This transilient matrix quantifies the nonlocal transport of air by convective eddies: for every height z, it gives the distribution of starting heights z{prime} for the eddies that arrive at z. In a cloud-resolving simulation of deep convection, the transilient matrix shows that two-thirds of the subcloud air convecting into the free troposphere originates from within 100 m of the surface. This finding clarifies which initial height to use when calculating convective available potential energy from soundings of the tropical troposphere.

  8. Seismic Constraints on Interior Solar Convection

    Science.gov (United States)

    Hanasoge, Shravan M.; Duvall, Thomas L.; DeRosa, Marc L.

    2010-01-01

    We constrain the velocity spectral distribution of global-scale solar convective cells at depth using techniques of local helioseismology. We calibrate the sensitivity of helioseismic waves to large-scale convective cells in the interior by analyzing simulations of waves propagating through a velocity snapshot of global solar convection via methods of time-distance helioseismology. Applying identical analysis techniques to observations of the Sun, we are able to bound from above the magnitudes of solar convective cells as a function of spatial convective scale. We find that convection at a depth of r/R(solar) = 0.95 with spatial extent l < 30, where l is the spherical harmonic degree, comprise weak flow systems, on the order of 15 m/s or less. Convective features deeper than r/R(solar) = 0.95 are more difficult to image due to the rapidly decreasing sensitivity of helioseismic waves.

  9. Covariability in the Monthly Mean Convective and Radiative Diurnal Cycles in the Amazon

    Science.gov (United States)

    Dodson, Jason B.; Taylor, Patrick C.

    2015-01-01

    The diurnal cycle of convective clouds greatly influences the radiative energy balance in convectively active regions of Earth, through both direct presence, and the production of anvil and stratiform clouds. Previous studies show that the frequency and properties of convective clouds can vary on monthly timescales as a result of variability in the monthly mean atmospheric state. Furthermore, the radiative budget in convectively active regions also varies by up to 7 Wm-2 in convectively active regions. These facts suggest that convective clouds connect atmospheric state variability and radiation variability beyond clear sky effects alone. Previous research has identified monthly covariability between the diurnal cycle of CERES-observed top-of-atmosphere radiative fluxes and multiple atmospheric state variables from reanalysis over the Amazon region. ASVs that enhance (reduce) deep convection, such as CAPE (LTS), tend to shift the daily OLR and cloud albedo maxima earlier (later) in the day by 2-3 hr. We first test the analysis method using multiple reanalysis products for both the dry and wet seasons to further investigate the robustness of the preliminary results. We then use CloudSat data as an independent cloud observing system to further evaluate the relationships of cloud properties to variability in radiation and atmospheric states. While CERES can decompose OLR variability into clear sky and cloud effects, it cannot determine what variability in cloud properties lead to variability in the radiative cloud effects. Cloud frequency, cloud top height, and cloud microphysics all contribute to the cloud radiative effect, all of which are observable by CloudSat. In addition, CloudSat can also observe the presence and variability of deep convective cores responsible for the production of anvil clouds. We use these capabilities to determine the covariability of convective cloud properties and the radiative diurnal cycle.

  10. Parents' anxiety and depression symptoms after successful infertility treatment and spontaneous conception: does singleton/twin pregnancy matter?

    Science.gov (United States)

    Tendais, I; Figueiredo, B

    2016-10-01

    Does mode of conception [spontaneous/after infertility treatment (IT)], type of pregnancy (singleton/twin) and parent gender have an effect on anxiety and depression levels and trajectories during pregnancy and the post-partum period? Conception after IT was associated with a transitory increase in anxiety during the perinatal period for parents of singletons, while for IT parents of twins higher levels of psychopathological symptoms tended to persist during pregnancy and the post-partum period. Most previous studies have shown that successful IT is not associated with poor psychological well-being during pregnancy and the post-partum period, but there is also some evidence for heightened pregnancy-related anxiety, lower self-esteem and lower self-efficacy. Parents of twins experience increased postnatal anxiety and depression. This prospective longitudinal study assessed 267 couples (N = 534) at each trimester of pregnancy, after childbirth and at 3 months post-partum. The sample comprised 36 couples who had conceived after IT (19 twin pairs and 17 singletons) and 231 couples who had conceived spontaneously (SC; 28 twin pairs and 203 singletons). Couples were recruited at four public hospitals in Portugal, and self-report measures of anxiety and depression symptoms were administered. IT parents reported higher anxiety after childbirth than parents who SC, regardless of pregnancy type. IT parents of twins showed higher anxiety at mid-pregnancy, as well as higher anxiety and depression at 3 months post-partum than IT parents of singletons. Among IT mothers, those who had twins exhibited higher depression after childbirth than those who had singletons. Differences according to mode of conception, pregnancy type and parents gender over time were also noted. During pregnancy, IT parents of twins showed no significant change in depression scores, while the other groups depression scores statistically significantly decreased over time. From pregnancy to the post

  11. Convective aggregation in realistic convective-scale simulations

    Science.gov (United States)

    Holloway, Christopher E.

    2017-06-01

    To investigate the real-world relevance of idealized-model convective self-aggregation, five 15 day cases of real organized convection in the tropics are simulated. These include multiple simulations of each case to test sensitivities of the convective organization and mean states to interactive radiation, interactive surface fluxes, and evaporation of rain. These simulations are compared to self-aggregation seen in the same model configured to run in idealized radiative-convective equilibrium. Analysis of the budget of the spatial variance of column-integrated frozen moist static energy shows that control runs have significant positive contributions to organization from radiation and negative contributions from surface fluxes and transport, similar to idealized runs once they become aggregated. Despite identical lateral boundary conditions for all experiments in each case, systematic differences in mean column water vapor (CWV), CWV distribution shape, and CWV autocorrelation length scale are found between the different sensitivity runs, particularly for those without interactive radiation, showing that there are at least some similarities in sensitivities to these feedbacks in both idealized and realistic simulations (although the organization of precipitation shows less sensitivity to interactive radiation). The magnitudes and signs of these systematic differences are consistent with a rough equilibrium between (1) equalization due to advection from the lateral boundaries and (2) disaggregation due to the absence of interactive radiation, implying disaggregation rates comparable to those in idealized runs with aggregated initial conditions and noninteractive radiation. This points to a plausible similarity in the way that radiation feedbacks maintain aggregated convection in both idealized simulations and the real world.Plain Language SummaryUnderstanding the processes that lead to the organization of tropical rainstorms is an important challenge for weather

  12. Intrauterine death in singleton pregnancies with trisomy 21, 18, 13 and monosomy X

    Directory of Open Access Journals (Sweden)

    Vanessa Vigna Goulart

    2016-04-01

    Full Text Available Summary A retrospective study from November 2004 to May 2012, conducted at the Obstetric Clinic of Hospital das Clínicas, Faculdade de Medicina, Universidade de São Paulo (HC-FMUSP, which included 92 singleton pregnancies with prenatal diagnosis of trisomy of chromosome 21 (T21, 18, 13 (T13/18 and monosomy X (45X, with diagnosis performed until the 26th week of pregnancy. The aim of the study was to describe the frequency and to investigate predictors of spontaneous fetal death (FD. Diagnosis (T21, n=36; T13/18, n=25; 45X, n=31 was made at a mean gestational age of 18.3±3.7 weeks, through chorionic villus biopsy (n=22,24%, amniocentesis (n=66, 72% and cordocentesis (n=4, 4%. Major malformations were present in 45 (49%; with hydrops in 32 (35% fetuses, more frequently in 45X [n=24/31, 77% vs. T21 (n=6/36, 17% and T13/18 (n=2/25, 8%, p<0.001]. Specialized fetal echocardiography was performed in 60% (55/92. Of these, 60% (33/55 showed changes in heart morphology and/or function. Fetuses with T13/18 had a higher incidence of cardiac anomalies [60 vs. 25% (T21 and 29% (45X, p= 0.01]. FD occurred in 55 (60% gestations, being more frequent in 45X [n=26/31, 84% vs. T21 (n=13/36, 36% and T13/18 (n=16/25, 64%, p<0.01]. Stepwise analysis showed a correlation between hydrops and death in fetuses with T21 (LR= 4.29; 95CI=1.9-8.0, p<0.0001. In fetuses with 45X, the presence of echocardiographic abnormalities was associated with lower risk of FD (LR= 0.56; 95CI=0.27- 0.85, p=0.005. No predictive factors were identified in the T13/18 group. Intra- uterine lethality of aneuploid fetuses is high. Occurrence of hydrops increases risk of FD in pregnancies with T21. In pregnancies with 45X, the occurrence of echocardiographic changes reduces this risk.

  13. CRUCIB: an axisymmetric convection code

    International Nuclear Information System (INIS)

    Bertram, L.A.

    1975-03-01

    The CRUCIB code was written in support of an experimental program aimed at measurement of thermal diffusivities of refractory liquids. Precise values of diffusivity are necessary to realistic analysis of reactor safety problems, nuclear waste disposal procedures, and fundamental metal forming processes. The code calculates the axisymmetric transient convective motions produced in a right circular cylindrical crucible, which is surface heated by an annular heat pulse. Emphasis of this report is placed on the input-output options of the CRUCIB code, which are tailored to assess the importance of the convective heat transfer in determining the surface temperature distribution. Use is limited to Prandtl numbers less than unity; larger values can be accommodated by replacement of a single block of the code, if desired. (U.S.)

  14. Vaginal progesterone for preventing preterm birth and adverse perinatal outcomes in singleton gestations with a short cervix: a meta-analysis of individual patient data.

    Science.gov (United States)

    Romero, Roberto; Conde-Agudelo, Agustin; Da Fonseca, Eduardo; O'Brien, John M; Cetingoz, Elcin; Creasy, George W; Hassan, Sonia S; Nicolaides, Kypros H

    2018-02-01

    The efficacy of vaginal progesterone for preventing preterm birth and adverse perinatal outcomes in singleton gestations with a short cervix has been questioned after publication of the OPPTIMUM study. To determine whether vaginal progesterone prevents preterm birth and improves perinatal outcomes in asymptomatic women with a singleton gestation and a midtrimester sonographic short cervix. We searched MEDLINE, EMBASE, LILACS, and CINAHL (from their inception to September 2017); Cochrane databases; bibliographies; and conference proceedings for randomized controlled trials comparing vaginal progesterone vs placebo/no treatment in women with a singleton gestation and a midtrimester sonographic cervical length ≤25 mm. This was a systematic review and meta-analysis of individual patient data. The primary outcome was preterm birth preterm birth preterm birth preterm birth preterm birth and improves perinatal outcomes in singleton gestations with a midtrimester sonographic short cervix, without any demonstrable deleterious effects on childhood neurodevelopment. Published by Elsevier Inc.

  15. Cryogenic helium gas convection research

    International Nuclear Information System (INIS)

    Donnelly, R.J.

    1994-10-01

    This is a report prepared by a group interested in doing research in thermal convection using the large scale refrigeration facilities available at the SSC Laboratories (SSCL). The group preparing this report consists of Michael McAshan at SSCL, Robert Behringer at Duke University, Katepalli Sreenivasan at Yale University, Xiao-Zhong Wu at Northern Illinois University and Russell Donnelly at the University of Oregon, who served as Editor for this report. This study reports the research and development opportunities in such a project, the technical requirements and feasibility of its construction and operation, and the costs associated with the needed facilities and support activities. The facility will be a unique national resource for studies of high-Reynolds-number and high-Rayleigh-number and high Rayleigh number turbulence phenomena, and is one of the six items determined as suitable for potential funding through a screening of Expressions of Interest. The proposed facility is possible only because of the advanced cryogenic technology available at the SSCL. Typical scientific issues to be addressed in the facility will be discussed. It devolved during our study, that while the main experiment is still considered to be the thermal convection experiment discussed in our original Expression of Interest, there are now a very substantial set of other, important and fundamental experiments which can be done with the large cryostat proposed for the convection experiment. We believe the facility could provide several decades of front-line research in turbulence, and shall describe why this is so

  16. Scaling rates of true polar wander in convecting planets and moons

    Science.gov (United States)

    Rose, Ian; Buffett, Bruce

    2017-12-01

    Mass redistribution in the convecting mantle of a planet causes perturbations in its moment of inertia tensor. Conservation of angular momentum dictates that these perturbations change the direction of the rotation vector of the planet, a process known as true polar wander (TPW). Although the existence of TPW on Earth is firmly established, its rate and magnitude over geologic time scales remain controversial. Here we present scaling analyses and numerical simulations of TPW due to mantle convection over a range of parameter space relevant to planetary interiors. For simple rotating convection, we identify a set of dimensionless parameters that fully characterize true polar wander. We use these parameters to define timescales for the growth of moment of inertia perturbations due to convection and for their relaxation due to true polar wander. These timescales, as well as the relative sizes of convective anomalies, control the rate and magnitude of TPW. This analysis also clarifies the nature of so called "inertial interchange" TPW events, and relates them to a broader class of events that enable large and often rapid TPW. We expect these events to have been more frequent in Earth's past.

  17. Compressible Convection Experiment using Xenon Gas in a Centrifuge

    Science.gov (United States)

    Menaut, R.; Alboussiere, T.; Corre, Y.; Huguet, L.; Labrosse, S.; Deguen, R.; Moulin, M.

    2017-12-01

    We present here an experiment especially designed to study compressible convection in the lab. For significant compressible convection effects, the parameters of the experiment have to be optimized: we use xenon gaz in a cubic cell. This cell is placed in a centrifuge to artificially increase the apparent gravity and heated from below. With these choices, we are able to reach a dissipation number close to Earth's outer core value. We will present our results for different heating fluxes and rotation rates. We success to observe an adiabatic gradient of 3K/cm in the cell. Studies of pressure and temperature fluctuations lead us to think that the convection takes place under the form of a single roll in the cell for high heating flux. Moreover, these fluctuations show that the flow is geostrophic due to the high rotation speed. This important role of rotation, via Coriolis force effects, in our experimental setup leads us to develop a 2D quasigeostrophic compressible model in the anelastic liquid approximation. We test numerically this model with the finite element solver FreeFem++ and compare its results with our experimental data. In conclusion, we will present our project for the next experiment in which the cubic cell will be replace by a annulus cell. We will discuss the new expected effects due to this geometry as Rossby waves and zonal flows.

  18. The convection electric field in auroral substorms

    DEFF Research Database (Denmark)

    Gjerløv, Jesper Wittendorff; Hoffman, R.A.

    2001-01-01

    Dynamics Explorer 2 (DE 2) electric field and ion drift data are used in a statistical study of the ionospheric convection electric field in bulge-type auroral substorms. Thirty-one individual DE 2 substorm crossings were carefully selected and organized by the use of global auroral images obtained...... this database enabled us to compile a model of the ionospheric convection electric field. The characteristics of the premidnight convection reversal show a pronounced local time dependency. Far west of the surge it is a fairly well defined point reversal or convection shear. Approaching the surge and within...... the surge it is a region of weak electric fields increasing in width toward midnight that separates regions of equatorward and poleward electric fields. Therefore we adopt the term Harang region rather than the Harang discontinuity for the premidnight convection reversal. A relatively narrow convection...

  19. Controls on sublithospheric small-scale convection on Curie depths

    Science.gov (United States)

    Likerman, Jeremias; Zlotnik, Sergio; Chun-Feng, Li

    2017-04-01

    As the ocean lithosphere cools and thickens, its bottom layer goes unstable leading to sub-lithospheric small-scale convection (SSC). Since SSC was originally proposed, there have been considerable efforts regarding the understanding of the physics that rules the thermal instabilities of the SSC (e.g. Dumoulin et al, 1999; Solomatov and Moresi, 2000). Over the last several years, it is understood that the interaction between the plate movement and the SSC tends to form longitudinal (LRs or also called 'Richter rolls') and transverse rolls (TRs), of which the axis is parallel and perpendicular to the plate motion, respectively. The geometry of these rolls have been been recently inferred by Li et al (2013) using Curie depths from the North Atlantic as proxies for plates temperatures. They showed that Curie depths have a large oscillating and heterogeneous patterns that could be related to SSC. In the North Atlantic transverse rolls seem predominant. In this work we analyze, by means of 3D dynamical numerical simulations, the influence of SSC on the Curie depths patterns observed in the North Atlantic and Pacific plates. We investigate the behaviour of the Curie isotherms trying to determine if SSC is able to reproduce the observed data, and the influence of several poorly constrained rheological parameters. Our numerical simulations show that: a) using realistic laboratory-constrained rheologies and temperature it is possible to modify temperatures as low as those at Curie depths; b) transverse rolls are generated as well as longitudinal rolls on those isotherms; c) the spreading rate is a first order control on the developing of transverse rolls. References Dumoulin, C., Doin, M. P., & Fleitout, L. (1999). Heat transport in stagnant lid convection with temperature-and pressure-dependent Newtonian or non-Newtonian rheology. Journal of Geophysical Research: Solid Earth, 104(B6), 12759-12777. Li, C. F., Wang, J., Lin, J., & Wang, T. (2013). Thermal evolution of the

  20. The Colombo Twin and Singleton Follow-up Study: a population based twin study of psychiatric disorders and metabolic syndrome in Sri Lanka.

    Science.gov (United States)

    Jayaweera, Kaushalya; Aschan, Lisa; Pannala, Gayani; Adikari, Anushka; Glozier, Nicholas; Ismail, Khalida; Pariante, Carmine M; Rijsdijk, Fruhling; Siribaddana, Sisira; Zavos, Helena M S; Zunszain, Patricia A; Sumathipala, Athula; Hotopf, Matthew

    2018-01-17

    The disease burden related to mental disorders and metabolic syndrome is growing in low-and middle-income countries (LMIC). The Colombo Twin and Singleton Study (COTASS) is a population-based sample of twins and singletons in Colombo, Sri Lanka. Here we present prevalence estimates for metabolic syndrome (metS) and mental disorders from a follow-up (COTASS-2) of the original study (COTASS-1), which was a mental health survey. In COTASS-2, participants completed structured interviews, anthropometric measures and provided fasting blood and urine samples. Depressive disorder, depressive symptoms, anxiety symptoms, post-traumatic stress disorder (PTSD) and hazardous alcohol use were ascertained with structured psychiatric screens (Composite International Diagnostic Interview (CIDI), Beck Depression Inventory (BDI-II), Generalised Anxiety Disorder Questionnaire (GAD-7), PTSD Checklist - Civilian Version (PCL-C), and Alcohol Use Disorders Identification Test (AUDIT)). We defined metS according to the International Diabetes Federation (IDF) criteria and the revised National Cholesterol Education Programme Adult Treatment Panel (NCEP ATP III) criteria. We estimated the prevalence of psychiatric disorders and metS and metS components, and associations with gender, education and age. Two thousand nine hundred thirty-four twins and 1035 singletons were followed up from COTASS-1 (83.4 and 61.8% participation rate, respectively). Prevalence estimates for depressive disorder (CIDI), depressive symptoms (BDI ≥ 16), anxiety symptoms (GAD-7 ≥ 10) and PTSD (PCL-C DSM criteria) were 3.8, 5.9, 3.6, and 4.5% respectively for twins and 3.9, 9.8, 5.1 and 5.4% for singletons. 28.1 and 30.9% of male twins and singletons respectively reported hazardous alcohol use. Approximately one third met the metS criteria (IDF: 27.4% twins, 44.6% singletons; NCEP ATP III: 30.6% twins, 48.6% singletons). The most prevalent components were central obesity (59.2% twins, 71.2% singletons) and

  1. Transitions Between Convective Patterns in Chemical Fronts

    OpenAIRE

    Wu, Y.; Vasquez, D. A.; Edwards, Boyd F.; Wilder, J. W.

    1995-01-01

    We present a theory for the transition from nonaxisymmetric to axisymmetric convection in iodate-arsenous acid reaction fronts propagating in a vertical slab. The transition takes place away from the onset of convection, where a convectionless flat front becomes unstable to a nonaxisymmetric convective front. The transition is studied by numerically solving a reaction-diffusion equation coupled with nonlinear hydrodynamics in a two-dimensional slab.

  2. Natural convection with combined driving forces

    Science.gov (United States)

    Ostrach, S.

    1980-01-01

    The problem of free and natural convection with combined driving forces is considered in general and all possible configurations are identified. Dimensionless parameters are discussed in order to help categorize the various problems, and existing work is critically evaluated. Four distinct cases are considered for conventional convection and for the situation when the body force and the density gradient are parallel but opposed. Considerable emphasis is given to unstable convection in horizontal layers.

  3. Convection of Moist Saturated Air: Analytical Study

    OpenAIRE

    Robert Zakinyan; Arthur Zakinyan; Roman Ryzhkov; Kristina Avanesyan

    2016-01-01

    In the present work, the steady-state stationary thermal convection of moist saturated air in a lower atmosphere has been studied theoretically. Thermal convection was considered without accounting for the Coriolis force, and with only the vertical temperature gradient. The analytical solution of geophysical fluid dynamics equations, which generalizes the formulation of the moist convection problem, is obtained in the two-dimensional case. The stream function is derived in the Boussinesq appr...

  4. New patterns of centrifugally driven thermal convection

    OpenAIRE

    Jaletzky, M.; Busse, F. H.

    2000-01-01

    An experimental study is described of convection driven by thermal buoyancy in the annular gap between two corotating coaxial cylinders, heated from the outside and cooled from the inside. Steady convection patterns of the hexaroll and of the knot type are observed in the case of high Prandtl number fluids, for which the Coriolis force is sufficiently small. Oblique rolls and phase turbulence in the form of irregular patterns of convection can also be observed in wide regions of the parameter...

  5. Airborne In Situ and Ground-based Polarimetric Radar Measurements of Tropical Convection in Support of CRYSTAL-FACE

    Science.gov (United States)

    Poellot, Michael R.; Kucera, Paul A.

    2004-01-01

    This report describes the work performed by the University of North Dakota (UND) under NASA Grant NAG5-11509, titled Airborne In Situ and Ground-based Polarimetric Radar Measurements of Tropical Convection in Support of CRYSTAL-FACE. This work focused on the collection of data by two key platforms: the UND Citation II research aircraft and the NASA NPOL radar system. The CRYSTAL-FACE (C-F) mission addresses several key issues from the NASA Earth System Enterprise, including the variability of water in the atmosphere, the forcing provided by tropical cirrus and the response of the Earth system to this forcing. In situ measurements and radar observations of tropical convection, cirrus clouds and their environment are core elements of C-F. One of the primary issues that C-F is addressing is the relationship of tropical cirrus anvils to precipitating deep convection. The in situ measurements from C-F are being used to validate remote sensing of Earth-Atmosphere properties, increase our knowledge of upper tropospheric water vapor and its distribution, and increase our knowledge of tropical cirrus cloud morphology and composition. Radar measurements, especially polarimetric diversity observations available fiom the NASA NPOL radar, are providing essential information about the initiation, modulation, and dissipation of convective cores and the generation of associated anvils in tropical convection. Specifically, NPOL radar measurements contain information about convective intensity and its vertical structure for comparison with thermodynamic and kinematic environmental measurements observed from soundings. Because of the polarimetric diversity of MOL, statistics on bulk microphysical properties can be retrieved and compared to the other characteristics of convection and associated cirrus anvils. In summary, the central objectives of this proposal were to deploy the UND Citation research aircraft as an in situ sensing platform for this mission and to provide collaborative

  6. Tropical convective onset statistics and establishing causality in the water vapor-precipitation relation

    Science.gov (United States)

    Neelin, J. D.; Kuo, Y. H.; Schiro, K. A.; Langenbrunner, B.; Mechoso, C. R.; Sahany, S.; Bernstein, D. N.

    2015-12-01

    Previous work by various authors has pointed to the role of humidity in the lower free troposphere in affecting the onset of deep convection in the tropics. Empirical relations between column water vapor and the onset of precipitation have been inferred to be related to this. Evidence includes deep-convective conditional instability calculations for entraining plumes, in which the lower free-tropospheric environment affects the onset of deep convection due to the impact on buoyancy of turbulent entrainment of dry versus moist air. Tropical Western Pacific in situ observations, and tropical ocean basin satellite retrievals in comparison to climate model diagnostics each indicate that substantial entrainment is required to explain the observed relationship. In situ observations from the GoAmazon field campaign confirm that the basic relationship holds over tropical land much as it does over tropical ocean (although with greater additional sensitivity to boundary layer variations and to freezing processes). The relationship between deep convection and water vapor is, however, a two-way street, with convection moistening the free troposphere. One might thus argue that there has not yet been a smoking gun in terms of establishing the causality of the precipitation-water vapor relationship. Parameter perturbation experiments in the coupled Community Earth System Model show that when the deep convective scheme has low values of entrainment, the set of statistics associated with the transition to deep convection are radically altered, and the observed pickup of precipitation with column water vapor is no longer seen. In addition to cementing the dominant direction of causality in the fast timescale precipitation-column water vapor relationship, the results point to impacts of this mechanism on the climatology. Because at low entrainment the convection can fire before the lower troposphere is moistened, the climatology of water vapor remains lower than observed. These

  7. Titan Balloon Convection Model, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This innovative research effort is directed at determining, quantitatively, the convective heat transfer coefficients applicable to a Montgolfiere balloon operating...

  8. REVERSALS IN THE 6-CELLS CONVECTION DRIVEN

    Directory of Open Access Journals (Sweden)

    G.M. Vodinchar

    2015-12-01

    Full Text Available We describe the large-scale model geodynamo, which based on indirect data of inhomogeneities in the density of the Earth’s core. Convection structure is associated with spherical harmonic Y24 , which defines the basic poloidal component of velocity. Coriolis drift of this mode determines the toroidal component of velocity. Thus, 6 convective cells are formed. The model takes into account the feedback effect of the magnetic field on convection. It was ascertained that the model contains stable regimes of field generation. The velocity of convection and the dipole component of the magnetic field are close to the observed ones.

  9. Continuous reorientation of synchronous terrestrial planets due to mantle convection

    Science.gov (United States)

    Leconte, Jérémy

    2018-02-01

    Many known rocky exoplanets are thought to have been spun down by tidal interactions to a state of synchronous rotation, in which a planet's period of rotation is equal to that of its orbit around its host star. Investigations into atmospheric and surface processes occurring on such exoplanets thus commonly assume that day and night sides are fixed with respect to the surface over geological timescales. Here we use an analytical model to show that true polar wander—where a planetary body's spin axis shifts relative to its surface because of changes in mass distribution—can continuously reorient a synchronous rocky exoplanet. As occurs on Earth, we find that even weak mantle convection in a rocky exoplanet can produce density heterogeneities within the mantle sufficient to reorient the planet. Moreover, we show that this reorientation is made very efficient by the slower rotation rate of a synchronous planet when compared with Earth, which limits the stabilizing effect of rotational and tidal deformations. Furthermore, a relatively weak lithosphere limits its ability to support remnant loads and stabilize against reorientation. Although uncertainties exist regarding the mantle and lithospheric evolution of these worlds, we suggest that the axes of smallest and largest moment of inertia of synchronous exoplanets with active mantle convection change continuously over time, but remain closely aligned with the star-planet and orbital axes, respectively.

  10. Scale analysis of convective clouds

    Directory of Open Access Journals (Sweden)

    Micha Gryschka

    2008-12-01

    Full Text Available The size distribution of cumulus clouds due to shallow and deep convection is analyzed using satellite pictures, LES model results and data from the German rain radar network. The size distributions found can be described by simple power laws as has also been proposed for other cloud data in the literature. As the observed precipitation at ground stations is finally determined by cloud numbers in an area and individual sizes and rain rates of single clouds, the cloud size distributions might be used for developing empirical precipitation forecasts or for validating results from cloud resolving models being introduced to routine weather forecasts.

  11. Characterizing Convection in Stellar Atmospheres

    International Nuclear Information System (INIS)

    Tanner, Joel; Basu, Sarbani; Demarque, Pierre; Robinson, Frank

    2011-01-01

    We perform 3D radiative hydrodynamic simulations to study the properties of convection in the superadiabatic layer of stars. The simulations show differences in both the stratification and turbulent quantities for different types of stars. We extract turbulent pressure and eddy sizes, as well as the T-τ relation for different stars and find that they are sensitive to the energy flux and gravity. We also show that contrary to what is usually assumed in the field of stellar atmospheres, the structure and gas dynamics of simulations of turbulent atmospheres cannot be parameterized with T eff and log(g) alone.

  12. Melting of the Earth's inner core.

    Science.gov (United States)

    Gubbins, David; Sreenivasan, Binod; Mound, Jon; Rost, Sebastian

    2011-05-19

    The Earth's magnetic field is generated by a dynamo in the liquid iron core, which convects in response to cooling of the overlying rocky mantle. The core freezes from the innermost surface outward, growing the solid inner core and releasing light elements that drive compositional convection. Mantle convection extracts heat from the core at a rate that has enormous lateral variations. Here we use geodynamo simulations to show that these variations are transferred to the inner-core boundary and can be large enough to cause heat to flow into the inner core. If this were to occur in the Earth, it would cause localized melting. Melting releases heavy liquid that could form the variable-composition layer suggested by an anomaly in seismic velocity in the 150 kilometres immediately above the inner-core boundary. This provides a very simple explanation of the existence of this layer, which otherwise requires additional assumptions such as locking of the inner core to the mantle, translation from its geopotential centre or convection with temperature equal to the solidus but with composition varying from the outer to the inner core. The predominantly narrow downwellings associated with freezing and broad upwellings associated with melting mean that the area of melting could be quite large despite the average dominance of freezing necessary to keep the dynamo going. Localized melting and freezing also provides a strong mechanism for creating seismic anomalies in the inner core itself, much stronger than the effects of variations in heat flow so far considered.

  13. Subfertility factors rather than assisted conception factors affect cognitive and behavioural development of 4-year-old singletons.

    Science.gov (United States)

    Schendelaar, Pamela; La Bastide-Van Gemert, Sacha; Heineman, Maas Jan; Middelburg, Karin J; Seggers, Jorien; Van den Heuvel, Edwin R; Hadders-Algra, Mijna

    2016-12-01

    Research on cognitive and behavioural development of children born after assisted conception is inconsistent. This prospective study aimed to explore underlying causal relationships between ovarian stimulation, in-vitro procedures, subfertility components and child cognition and behaviour. Participants were singletons born to subfertile couples after ovarian stimulation IVF (n = 63), modified natural cycle IVF (n = 53), natural conception (n = 79) and singletons born to fertile couples (reference group) (n = 98). At 4 years, cognition (Kaufmann-ABC-II; total IQ) and behaviour (Child Behavior Checklist; total problem T-score) were assessed. Causal inference search algorithms and structural equation modelling was applied to unravel causal mechanisms. Most children had typical cognitive and behavioural scores. No underlying causal effect was found between ovarian stimulation and the in-vitro procedure and outcome. Direct negative causal effects were found between severity of subfertility (time to pregnancy) and cognition and presence of subfertility and behaviour. Maternal age and maternal education acted as confounders. The study concludes that no causal effects were found between ovarian stimulation or in-vitro procedures and cognition and behaviour in childrenaged 4 years born to subfertile couples. Subfertility, especially severe subfertility, however, was associated with worse cognition and behaviour. Copyright © 2016 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

  14. The effect of gestational diabetes, pre-gravid maternal obesity, and their combination ('diabesity') on outcomes of singleton gestations.

    Science.gov (United States)

    Blickstein, Isaac; Doyev, Reut; Trojner Bregar, Andreja; Bržan Šimenc, Gabrijela; Verdenik, Ivan; Tul, Natasa

    2018-03-01

    To assess the effect of the combination of gestational diabetes mellitus (GDM) and pre-gravid obesity ('diabesity') in singleton gestations. We compared perinatal outcomes of singleton gestations in mothers with GDM and pre-gravid obesity, with GDM but with normal pre-gravid BMI, and obese mothers without GDM. We compared diabesity mothers (n = 1525, 24.4% of mothers with GDM, 9.9% of all obese women) to mothers with GDM but with normal BMI (n = 4704, 75.6% of mothers with GDM) and to obese mothers without GDM (n = 13,937, 90.1% of all obese mothers). Obesity, with and without GDM, increased the odds of having chronic hypertension whereas preeclampsia appears to be influenced by obesity only, as were the risk of births at 4000 g, low 5-min Apgar scores and NICU admissions. Obesity (without diabetes) is more frequently associated with adverse perinatal outcomes than diabesity or GDM in non-obese mothers. A campaign to decrease pre-gravid obesity should have at least the same priority as any campaign to control GDM.

  15. Obstetric and perinatal outcomes of singletons after single blastocyst transfer: is there any difference according to blastocyst morphology?

    Science.gov (United States)

    Bouillon, Céline; Celton, Noémie; Kassem, Sandra; Frapsauce, Cynthia; Guérif, Fabrice

    2017-08-01

    A strong correlation between blastocyst morphology and implantation has been shown by many studies. The consequences and effects of assisted reproductive techniques on children's short and long-term health have always been a source of discussion. The obstetric and perinatal outcome of singletons according to blastocyst morphology has rarely been evaluated. The aim of this observational study is to determine whether a relationship exists between blastocyst morphology and obstetric and perinatal outcomes. A total of 799 singleton clinical pregnancies were analysed after transfer of a single fresh blastocyst on day 5 between 2006 and 2013. Blastocysts were divided into four groups based on their morphology on day 5: group 1 = good morphology blastocysts; group 2 = fair morphology blastocysts; group 3 = poor morphology blastocysts and group 4 = early (B1/B2) blastocysts. Obstetric and perinatal outcomes were compared between the four groups. After adjustment for some confounding variables, main obstetric and perinatal outcomes after transfer of blastocysts with poor morphological characteristics were not associated with increased adverse obstetric and perinatal events. Sex ratio was significantly higher in group 1 compared with groups 2, 3 and 4, and in Group 2 compared with Group 3 (P < 0.001) even after adjustment (P < 0.05). Copyright © 2017 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

  16. Earth's Decelerating Tectonic Plates

    Energy Technology Data Exchange (ETDEWEB)

    Forte, A M; Moucha, R; Rowley, D B; Quere, S; Mitrovica, J X; Simmons, N A; Grand, S P

    2008-08-22

    Space geodetic and oceanic magnetic anomaly constraints on tectonic plate motions are employed to determine a new global map of present-day rates of change of plate velocities. This map shows that Earth's largest plate, the Pacific, is presently decelerating along with several other plates in the Pacific and Indo-Atlantic hemispheres. These plate decelerations contribute to an overall, globally averaged slowdown in tectonic plate speeds. The map of plate decelerations provides new and unique constraints on the dynamics of time-dependent convection in Earth's mantle. We employ a recently developed convection model constrained by seismic, geodynamic and mineral physics data to show that time-dependent changes in mantle buoyancy forces can explain the deceleration of the major plates in the Pacific and Indo-Atlantic hemispheres.

  17. Rare earths

    International Nuclear Information System (INIS)

    Cranstone, D.A.

    1980-01-01

    There has been no Canadian production of the rare earth oxides since 1977. World production in 1978, the last year for which figures are available, is estimated to have been about 41000 tonnes, mostly from Australia and the United States. The United States Bureau of Mines estimates that world reserves contain about 7 million tonnes of rare earth oxides and 35 million tonnes of yttrium. The largest yttrium reserves are in India, while China is believed to have the world's largest reserves of rare earth oxides. World consumption of rare aarths increased slightly in 1980, but is still only a small fraction of known reserves. Rare earths are used mainly in high-strength magnets, automobile exhaust systems, fluorescent tube and television screen phosphors, metallurgical applications, petroleum cracking catalysts, and glass polishing

  18. Earth Sciences

    International Nuclear Information System (INIS)

    Anon.

    1980-01-01

    The following papers were presented at the earth science session: earth science developments in support of water isolation; development of models and parameters for ground-water flow in fractured rock masses; isotope geochemistry as a tool for determining regional ground-water flow; natural analogs of radionuclide migration; nuclide retardation data: its use in the NWTS program; and ground-water geochemistry and interaction with basalt at Hanford

  19. Convective mixing and accretion in white dwarfs

    International Nuclear Information System (INIS)

    Koester, D.

    1976-01-01

    The evolution of convection zones in cooling white dwarfs with helium envelopes and outer hydrogen layers is calculated with a complete stellar evolution code. It is shown that white dwarfs of spectral type DB cannot be formed from DA stars by convective mixing. However, for cooler temperatures (Tsub(e) [de

  20. New population-based references for birth weight, length, and head circumference in singletons and twins from 23 to 43 gestation weeks.

    Science.gov (United States)

    Sankilampi, Ulla; Hannila, Marja-Leena; Saari, Antti; Gissler, Mika; Dunkel, Leo

    2013-09-01

    Birth size curves are needed for clinical and epidemiological purposes. We constructed birth weight (BW), length (BL), and head circumference (BHC) references, assessed effects of twinness and parity, and defined cut-off points for small, appropriate, and large for gestational age. Birth register data of all 753,036 infants born in 1996-2008 in Finland were cleaned to create references reflecting optimal intrauterine growth. The final data included 533,666 singletons and 15,033 twins (median gestation weeks (gws) 40.0 and 37.1, respectively, 41.6% primiparous). Sex-specific BW, BL, and BHC references were constructed from 23 to 43 gws separately for singletons and twins born to primiparous or multiparous mothers. GAMLSS method was used for modelling. In singletons from 36 gws onwards, increased BW and BL were observed in comparison to previous reference from 1979-1983. Twins diverged from singletons from 30 gws onwards. At 37.0 gws, mean BW was 400 g lower and mean BL 1.2 cm shorter than in singletons. From 30 gws onwards, birth size was larger in infants of multiparous than primiparous mothers. Population-based birth size references are available for the evaluation of birth size. Accounting for plurality and parity improves the accuracy of birth size evaluation.

  1. Convective penetration in a young sun

    Science.gov (United States)

    Pratt, Jane; Baraffe, Isabelle; Goffrey, Tom; MUSIC developers group

    2018-01-01

    To interpret the high-quality data produced from recent space-missions it is necessary to study convection under realistic stellar conditions. We describe the multi-dimensional, time implicit, fully compressible, hydrodynamic, implicit large eddy simulation code MUSIC. We use MUSIC to study convection during an early stage in the evolution of our sun where the convection zone covers approximately half of the solar radius. This model of the young sun possesses a realistic stratification in density, temperature, and luminosity. We approach convection in a stellar context using extreme value theory and derive a new model for convective penetration, targeted for one-dimensional stellar evolution calculations. This model provides a scenario that can explain the observed lithium abundance in the sun and in solar-like stars at a range of ages.

  2. Convection of Moist Saturated Air: Analytical Study

    Directory of Open Access Journals (Sweden)

    Robert Zakinyan

    2016-01-01

    Full Text Available In the present work, the steady-state stationary thermal convection of moist saturated air in a lower atmosphere has been studied theoretically. Thermal convection was considered without accounting for the Coriolis force, and with only the vertical temperature gradient. The analytical solution of geophysical fluid dynamics equations, which generalizes the formulation of the moist convection problem, is obtained in the two-dimensional case. The stream function is derived in the Boussinesq approximation with velocity divergence taken as zero. It has been shown that the stream function is asymmetrical in vertical direction contrary to the dry and moist unsaturated air convection. It has been demonstrated that the convection in moist atmosphere strongly depends on the vapor mass fraction gradient.

  3. The development of small-scale convection below evolving oceanic plates

    Science.gov (United States)

    Coltice, N.; Garnero, E.

    2015-12-01

    Seafloor of older ages shows a constancy of heat flow, and bathymetry that is different from what is expected for a half-space cooling model. These observations led to consideration of the existence of small-scale convection below the lithosphere (Parsons and McKenzie, 1978). Previous studies have characterized the detailed physics of such processes (Davaille and Jaupart, 1994; Choblet and Sotin, 2000; Solomatov and Moresi, 2000; Korenaga and Jordan, 2003 among others). However, questions remain for applications to the Earth: what is the shape of developed small-scale convection, what length-scales are involved, how does associated small-scale convection depend on the plate layout and its time-dependence. Using 3D spherical models of mantle convection with plate-like behaviour (Tackley, 2008), we will present a study of developed small-scale convection in a context of self-organization of plates and mantle flow. Small-scale convection depends on the resistance of the lithosphere, and its development beneath large plates produce network shapes with specific length-scales and orientations (see figure). We will show the impact of the size of plates and the evolution of subduction on the small-scale convection, and characterize how the age-heat flow relationship can change with time. The potential for seismic detection of the spatiotemporal patterns of temperature heterogeneity will also be discussed. ReferencesChoblet, G., and C. Sotin, Phys. Earth Planet. Inter. 119, 321-336 (2000). Davaille, A., and C. Jaupart, J. Geophys. Res. 99, 19,853-19,866 (1994). Korenaga, J., and T. H. Jordan, J. Geophys. Res. 108, 2333, (2003). Parsons, B., and D. McKenzie, J. Geophys. Res. 83, 4485-4496 (1978). Solomatov, V. S., and L. N. Moresi, J. Geophys. Res. 105, 21,795-21,817 (2000). Tackley, P. J., Phys. Earth Planet. Inter. 171, 7-18 (2008). Figure: Age of the seafloor in Myrs and white countour of a cold temperature isotherm showing the network of small-scale convection.

  4. Scaling and excitation of combined convection in a rapidly rotating plane layer

    Energy Technology Data Exchange (ETDEWEB)

    Starchenko, S. V., E-mail: sstarchenko@mail.ru [Russian Academy of Sciences, Pushkov Institute of Terrestrial Magnesium, Ionosphere and Radio Wave Propagation (Russian Federation)

    2017-02-15

    The optimum (to my mind) scaling of the combined thermal and compositional convection in a rapidly rotating plane layer is proposed.This scaling follows from self-consistent estimates of typical physical quantities. Similarity coefficients are introduced for the ratio convection dissipation/convection generation (s) and the ratio thermal convection/compositional convection (r). The third new and most important coefficient δ is the ratio of the characteristic size normal to the axis of rotation to the layer thickness. The faster the rotation, the lower δ. In the case of the liquid Earth core, δ ~ 10{sup –3} substitutes for the generally accepted Ekman number (E ~ 10{sup –15}) and s ~ 10{sup –6} substitutes for the inverse Rayleigh number 1/Ra ~ 10{sup –30}. It is found that, at turbulent transport coefficients, number s and the Prandtl number are on the order of unity for any objects and δ is independent of transport coefficients. As a result of expansion in powers of δ, an initially 3D system of six variables is simplified to an almost 2D system of four variables without δ. The problem of convection excitation in the main volume is algebraically solved and this problem for critical values is analytically solved. Dispersion relations and general expressions for critical wavenumbers, numbers s (which determine Rayleigh numbers), other critical parameters, and asymptotic solutions are derived. Numerical estimates are made for the liquid cores in the planets that resemble the Earth. Further possible applications of the results obtained are proposed for the interior of planets, moons, their oceans, stars, and experimental objects.

  5. Scaling and excitation of combined convection in a rapidly rotating plane layer

    Science.gov (United States)

    Starchenko, S. V.

    2017-02-01

    The optimum (to my mind) scaling of the combined thermal and compositional convection in a rapidly rotating plane layer is proposed.This scaling follows from self-consistent estimates of typical physical quantities. Similarity coefficients are introduced for the ratio convection dissipation/convection generation ( s) and the ratio thermal convection/compositional convection ( r). The third new and most important coefficient δ is the ratio of the characteristic size normal to the axis of rotation to the layer thickness. The faster the rotation, the lower δ. In the case of the liquid Earth core, δ 10-3 substitutes for the generally accepted Ekman number ( E 10-15) and s 10-6 substitutes for the inverse Rayleigh number 1/Ra 10-30. It is found that, at turbulent transport coefficients, number s and the Prandtl number are on the order of unity for any objects and δ is independent of transport coefficients. As a result of expansion in powers of δ, an initially 3D system of six variables is simplified to an almost 2D system of four variables without δ. The problem of convection excitation in the main volume is algebraically solved and this problem for critical values is analytically solved. Dispersion relations and general expressions for critical wavenumbers, numbers s (which determine Rayleigh numbers), other critical parameters, and asymptotic solutions are derived. Numerical estimates are made for the liquid cores in the planets that resemble the Earth. Further possible applications of the results obtained are proposed for the interior of planets, moons, their oceans, stars, and experimental objects.

  6. The GeoFlow experiment-spherical Rayleigh-Benard convection under the influence of an artificial central force field

    International Nuclear Information System (INIS)

    Gellert, M; Beltrame, P; Egbers, C

    2005-01-01

    Spherical Rayleigh-Benard convection under the influence of an artificial central force field produced by the so-called dielectrophoretic effect is studied as a simplified model of the flow in the outer earth core. The fluid motion there is most probably driving the earth's dynamo and the energy source for the earth's magnetic field. Studying convective flows in earth-like geometry could lead to a deeper understanding of the basics of these processes. This research is a preparatory study for the experiments on the International Space Station (ISS). A bifurcation-theoretical approach shows the existence of heteroclinic cycles between spherical modes (l, l + 1) for the non-rotating system. This behavior depends strong on the radius ratio of the spheres and will be hard to detect in the experiment. For slow rotations interactions of the azimuthal modes (m, m + 1) found in numerical simulations for supercritical states are supposed to be experimentally observable

  7. Axisymmetric Marangoni convection in microencapsulation

    Science.gov (United States)

    Subramanian, Pravin; Zebib, Abdelfattah; McQuillan, Barry

    2005-07-01

    Spherical shells used as laser targets in inertial confinement fusion (ICF) experiments are made by microencapsulation. In one phase of manufacturing, the spherical shells contain a solvent (fluorobenzene (FB)) and a solute (polystyrene (PAMS)) in a water-FB environment. Evaporation of the FB results in the desired hardened plastic hollow spherical shells, 1-2 mm in diameter. Perfect sphericity is demanded for efficient fusion ignition and the observed surface roughness maybe driven by Marangoni instabilities due to surface tension dependence on the FB concentration (buoyant forces are negligible in this micro-scale problem). Here we model this drying process and compute nonlinear, time-dependent, axisymmetric, variable viscosity, infinite Schmidt number solutocapillary convection in the shells. Comparison with results from linear theory and available experiments are made.

  8. Convective evaporation of vertical films.

    Science.gov (United States)

    Boulogne, François; Dollet, Benjamin

    2018-02-28

    Motivated by the evaporation of soap films, which has a significant effect on their lifetime, we performed an experimental study on the evaporation of vertical surfaces with model systems based on hydrogels. From the analogy between heat and mass transfer, we adopt a model describing the natural convection in the gas phase due to a density contrast between dry and saturated air. Our measurements show a good agreement with this model, both in terms of scaling law with the Grashof number and in terms of order of magnitude. We discuss the corrections to take into account, notably the contribution of edge effects, which have a small but visible contribution when lateral and bottom surface areas are not negligible compared to the main evaporating surface area.

  9. Thermochemical structure of the Earth's mantle and continental crust

    DEFF Research Database (Denmark)

    Guerri, Mattia

    in determining crustal seismic discontinuities. In the second chapter, I deal about the possibility to disentangle the dynamic and isostatic contribution in shaping the Earth's surface topography. Dynamic topography is directly linked to mantle convection driven by mantle thermo-chemical anomalies, and can......A detailed knowledge of the Earth's thermal structure and chemical composition is fundamental in order to understand the processes driving the planet ormation and evolution. The inaccessibility of most of the Earth's interior makes the determination of its thermo-chemical conditions a challenging...... argue therefore that our understandings of the lithosphere density structure, needed to determine the isostatic topography, and of the mantle density and viscosity, required to compute the dynamic topography, are still too limited to allow a robust determination of mantle convection effects on the Earth...

  10. Actively convected liquid metal divertor

    International Nuclear Information System (INIS)

    Shimada, Michiya; Hirooka, Yoshi

    2014-01-01

    The use of actively convected liquid metals with j × B force is proposed to facilitate heat handling by the divertor, a challenging issue associated with magnetic fusion experiments such as ITER. This issue will be aggravated even more for DEMO and power reactors because the divertor heat load will be significantly higher and yet the use of copper would not be allowed as the heat sink material. Instead, reduced activation ferritic/martensitic steel alloys with heat conductivities substantially lower than that of copper, will be used as the structural materials. The present proposal is to fill the lower part of the vacuum vessel with liquid metals with relatively low melting points and low chemical activities including Ga and Sn. The divertor modules, equipped with electrodes and cooling tubes, are immersed in the liquid metal. The electrode, placed in the middle of the liquid metal, can be biased positively or negatively with respect to the module. The j × B force due to the current between the electrode and the module provides a rotating motion for the liquid metal around the electrodes. The rise in liquid temperature at the separatrix hit point can be maintained at acceptable levels from the operation point of view. As the rotation speed increases, the current in the liquid metal is expected to decrease due to the v × B electromotive force. This rotating motion in the poloidal plane will reduce the divertor heat load significantly. Another important benefit of the convected liquid metal divertor is the fast recovery from unmitigated disruptions. Also, the liquid metal divertor concept eliminates the erosion problem. (letter)

  11. Actively convected liquid metal divertor

    Science.gov (United States)

    Shimada, Michiya; Hirooka, Yoshi

    2014-12-01

    The use of actively convected liquid metals with j × B force is proposed to facilitate heat handling by the divertor, a challenging issue associated with magnetic fusion experiments such as ITER. This issue will be aggravated even more for DEMO and power reactors because the divertor heat load will be significantly higher and yet the use of copper would not be allowed as the heat sink material. Instead, reduced activation ferritic/martensitic steel alloys with heat conductivities substantially lower than that of copper, will be used as the structural materials. The present proposal is to fill the lower part of the vacuum vessel with liquid metals with relatively low melting points and low chemical activities including Ga and Sn. The divertor modules, equipped with electrodes and cooling tubes, are immersed in the liquid metal. The electrode, placed in the middle of the liquid metal, can be biased positively or negatively with respect to the module. The j × B force due to the current between the electrode and the module provides a rotating motion for the liquid metal around the electrodes. The rise in liquid temperature at the separatrix hit point can be maintained at acceptable levels from the operation point of view. As the rotation speed increases, the current in the liquid metal is expected to decrease due to the v × B electromotive force. This rotating motion in the poloidal plane will reduce the divertor heat load significantly. Another important benefit of the convected liquid metal divertor is the fast recovery from unmitigated disruptions. Also, the liquid metal divertor concept eliminates the erosion problem.

  12. Non-singleton colors are not attended faster than categories, but they are encoded faster: A combined approach of behavior, modeling and ERPs.

    Science.gov (United States)

    Callahan-Flintoft, Chloe; Wyble, Brad

    2017-11-01

    The visual system is able to detect targets according to a variety of criteria, such as by categorical (letter vs digit) or featural attributes (color). These criteria are often used interchangeably in rapid serial visual presentation (RSVP) studies but little is known about how rapidly they are processed. The aim of this work was to compare the time course of attentional selection and memory encoding for different types of target criteria. We conducted two experiments where participants reported one or two targets (T1, T2) presented in lateral RSVP streams. Targets were marked either by being a singleton color (red letter among black letters), being categorically distinct (digits among letters) or non-singleton color (target color letter among heterogeneously colored letters). Using event related potential (ERPs) associated with attention and memory encoding (the N2pc and the P3 respectively), we compared the relative latency of these two processing stages for these three kinds of targets. In addition to these ERP measures, we obtained convergent behavioral measures for attention and memory encoding by presenting two targets in immediate sequence and comparing their relative accuracy and proportion of temporal order errors. Both behavioral and EEG measures revealed that singleton color targets were attended much more quickly than either non-singleton color or categorical targets, and there was very little difference between attention latencies to non-singleton color and categorical targets. There was however a difference in the speed of memory encoding for non-singleton color and category latencies in both behavioral and EEG measures, which shows that encoding latency differences do not always mirror attention latency differences. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Substorms and polar cap convection: the 10 January 2004 interplanetary CME case

    Directory of Open Access Journals (Sweden)

    Y. Andalsvik

    2012-01-01

    Full Text Available The expansion-contraction model of Dungey cell plasma convection has two different convection sources, i.e. reconnections at the magnetopause and in the magnetotail. The spatial-temporal structure of the nightside source is not yet well understood. In this study we shall identify temporal variations in the winter polar cap convection structure during substorm activity under steady interplanetary conditions. Substorm activity (electrojets and particle precipitations is monitored by excellent ground-satellite DMSP F15 conjunctions in the dusk-premidnight sector. We take advantage of the wide latitudinal coverage of the IMAGE chain of ground magnetometers in Svalbard – Scandinavia – Russia for the purpose of monitoring magnetic deflections associated with polar cap convection and substorm electrojets. These are augmented by direct observations of polar cap convection derived from SuperDARN radars and cross-track ion drift observations during traversals of polar cap along the dusk-dawn meridian by spacecraft DMSP F13. The interval we study is characterized by moderate, stable forcing of the magnetosphere-ionosphere system (EKL = 4.0–4.5 mV m−1; cross polar cap potential (CPCP, Φ (Boyle = 115 kV during Earth passage of an interplanetary CME (ICME, choosing an 4-h interval where the magnetic field pointed continuously south-west (Bz By By polarity of the ICME magnetic field, a clear indication of a nightside source.

  14. A Test of Sensitivity to Convective Transport in a Global Atmospheric CO2 Simulation

    Science.gov (United States)

    Bian, H.; Kawa, S. R.; Chin, M.; Pawson, S.; Zhu, Z.; Rasch, P.; Wu, S.

    2006-01-01

    Two approximations to convective transport have been implemented in an offline chemistry transport model (CTM) to explore the impact on calculated atmospheric CO2 distributions. GlobalCO2 in the year 2000 is simulated using theCTM driven by assimilated meteorological fields from the NASA s Goddard Earth Observation System Data Assimilation System, Version 4 (GEOS-4). The model simulates atmospheric CO2 by adopting the same CO2 emission inventory and dynamical modules as described in Kawa et al. (convective transport scheme denoted as Conv1). Conv1 approximates the convective transport by using the bulk convective mass fluxes to redistribute trace gases. The alternate approximation, Conv2, partitions fluxes into updraft and downdraft, as well as into entrainment and detrainment, and has potential to yield a more realistic simulation of vertical redistribution through deep convection. Replacing Conv1 by Conv2 results in an overestimate of CO2 over biospheric sink regions. The largest discrepancies result in a CO2 difference of about 7.8 ppm in the July NH boreal forest, which is about 30% of the CO2 seasonality for that area. These differences are compared to those produced by emission scenario variations constrained by the framework of Intergovernmental Panel on Climate Change (IPCC) to account for possible land use change and residual terrestrial CO2 sink. It is shown that the overestimated CO2 driven by Conv2 can be offset by introducing these supplemental emissions.

  15. A new method to reconstruct the ionospheric convection patterns in the polar cap

    Directory of Open Access Journals (Sweden)

    P. L. Israelevich

    1999-06-01

    Full Text Available A new method to reconstruct the instantaneous convection pattern in the Earth's polar ionosphere is suggested. Plasma convection in the polar cap ionosphere is described as a hydrodynamic incompressible flow. This description is valid in the region where the electric currents are field aligned (and hence, the Lorentz body force vanishes. The problem becomes two-dimensional, and may be described by means of stream function. The flow pattern may be found as a solution of the boundary value problem for stream function. Boundary conditions should be provided by measurements of the electric field or plasma velocity vectors along the satellite orbits. It is shown that the convection pattern may be reconstructed with a reasonable accuracy by means of this method, by using only the minimum number of satellite crossings of the polar cap. The method enables us to obtain a reasonable estimate of the convection pattern without knowledge of the ionospheric conductivity.Key words. Ionosphere (modelling and forecasting; plasma convection; polar ionosphere

  16. A new method to reconstruct the ionospheric convection patterns in the polar cap

    Directory of Open Access Journals (Sweden)

    P. L. Israelevich

    Full Text Available A new method to reconstruct the instantaneous convection pattern in the Earth's polar ionosphere is suggested. Plasma convection in the polar cap ionosphere is described as a hydrodynamic incompressible flow. This description is valid in the region where the electric currents are field aligned (and hence, the Lorentz body force vanishes. The problem becomes two-dimensional, and may be described by means of stream function. The flow pattern may be found as a solution of the boundary value problem for stream function. Boundary conditions should be provided by measurements of the electric field or plasma velocity vectors along the satellite orbits. It is shown that the convection pattern may be reconstructed with a reasonable accuracy by means of this method, by using only the minimum number of satellite crossings of the polar cap. The method enables us to obtain a reasonable estimate of the convection pattern without knowledge of the ionospheric conductivity.

    Key words. Ionosphere (modelling and forecasting; plasma convection; polar ionosphere

  17. Prenatal screening at 11-13+6 weeks in assisted reproductive technology singleton pregnancies and those conceived naturally.

    Science.gov (United States)

    Gong, Meng; Shi, Hua; Zhang, Yu-guo; Ming, Lei

    2015-10-01

    To investigate whether assisted reproductive technology (ART) increases the risk of fetal chromosomal abnormalities. A total of 2034 singleton pregnant women were included in this retrospective study. They were divided into ART (574 fetuses) and control groups (1460 fetuses conceived naturally). All pregnant women received screening according to the Fetal Medicine Foundation, London 2004 Kypros H. Nicolaides guidelines at 11-13+6 weeks of gestation. Accordingly, women with value at risk of chromosomal abnormalities >1:250 underwent chorionic villus sampling or amniocentesis. Mean body mass index was 22.83 ± 3.27 versus 21.29 ± 2.81 kg/m(2) in the ART and control groups, respectively (P fetal chromosomal abnormalities. Additionally, fetus size in the ART group was bigger than that in the natural conception group. © 2015 Japan Society of Obstetrics and Gynecology.

  18. Velamentous Cord Insertion in a Singleton Pregnancy: An Obscure Cause of Emergency Cesarean—A Case Report

    Directory of Open Access Journals (Sweden)

    Juliana Rocha

    2012-01-01

    Full Text Available Approximately 2% of low-risk pregnant women still require an emergency Cesarean section after the onset of labor. Because it is likely that half of these cases are associated with placental and umbilical cord abnormalities, it is thought that prenatal detection of such abnormalities would reduce the number of emergency cesarean sections in low-risk women. Velamentous cord insertion is an abnormal cord insertion in which the umbilical vessels diverge as they traverse between the amnion and chorion before reaching the placenta. With a reported incidence of 1% in singleton pregnancies, it has been associated with several obstetric complications. This condition has been diagnosed by ultrasonography with a sensitivity of 67% and specificity of 100% in the second trimester. The present case highlights the importance of the systematic assessment of the placental cord insertion site at routine obstetric ultrasound and the potential of identifying pregnancies with velamentous insertion and, therefore, those at risk for obstetric complications.

  19. The influence of maternal glucose metabolism on fetal growth, development and morbidity in 917 singleton pregnancies in nondiabetic women.

    Science.gov (United States)

    Farmer, G; Russell, G; Hamilton-Nicol, D R; Ogenbede, H O; Ross, I S; Pearson, D W; Thom, H; Kerridge, D F; Sutherland, H W

    1988-03-01

    To study the effects on the fetus of variations in maternal glucose tolerance, a 25 g rapid intravenous glucose tolerance test was performed at or about 32 weeks gestation in 917 randomly selected nondiabetic women with singleton pregnancies. The results were withheld from the patients and their obstetricians and paediatricians, and no treatment or advice was offered. Fasting plasma glucose and indices of glucose disposal (including a new index which we have termed "summed glucose") were distributed unimodally, with no evidence of a separate pathological group towards the diabetic end of the distributions. Significant associations were found between maternal glucose metabolism and various measures of neonatal nutrition and morbidity, including the incidence of congenital malformations and morbidity related to asphyxia, suggesting that variations within the normal range in maternal glucose metabolism can influence growth and development in the fetus. These relationships were continuous throughout the range of maternal glucose tolerance and were not of predictive value in individual cases.

  20. The Venus-Earth-Jupiter spin-orbit coupling model

    Science.gov (United States)

    Wilson, I. R. G.

    2013-12-01

    A Venus-Earth-Jupiter spin-orbit coupling model is constructed from a combination of the Venus-Earth-Jupiter tidal-torquing model and the gear effect. The new model produces net tangential torques that act upon the outer convective layers of the Sun with periodicities that match many of the long-term cycles that are found in the 10Be and 14C proxy records of solar activity.

  1. Risk factors associated with preterm birth among singletons following assisted reproductive technology in Australia 2007–2009–a population-based retrospective study

    OpenAIRE

    Xu, Xu K; Wang, Yueping A; Li, Zhuoyang; Lui, Kei; Sullivan, Elizabeth A

    2014-01-01

    Background Preterm birth, a leading cause of neonatal death, is more common in multiple births and thus there has being an increasing call for reducing multiple births in ART. However, few studies have compared risk factors for preterm births amongst ART and non-ART singleton birth mothers. Methods A population-based study of 393,450 mothers, including 12,105 (3.1%) ART mothers, with singleton gestations born between 2007 and 2009 in 5 of the 8 jurisdictions in Australia. Univariable and mult...

  2. Hospitalization in adolescence and young adulthood among twins and singletons: a Swedish cohort study of subjects born between 1973 and 1983.

    Science.gov (United States)

    Bladh, Marie; Carstensen, John; Josefsson, Ann; Finnström, Orvar; Sydsjö, Gunilla

    2013-06-01

    Children born with non-optimal birth characteristics - that is, are small for gestational age and/or preterm - have an increased risk for several long-term effects such as neurological sequelae and chronic disease. The purpose of this study was to examine whether twins exhibited a different outcome, compared with singletons, in terms of hospitalization during adolescence and early adulthood, and to what extent differences remain when considering the divergence in birth characteristics between singletons and twins. Persons born between 1973 and 1983 in Sweden and surviving until age 13 were included and followed until the end of 2006. Data on birth characteristics, parental socio-demographic factors, and hospitalizations were collected from national registers. Adjusting for parental socio-demographic factors, twins had a higher risk of being hospitalized than singletons (odds ratio, OR = 1.17, 95% confidence interval, CI = 1.10-1.25) and more often due to 'Congenital anomalies' (OR = 1.18, 95% CI = 1.06-1.28), 'Infections' (OR = 1.14; 95% CI = 1.08-1.20), 'External causes of illness' (OR = 1.10, 95% CI = 1.06-1.15), and 'Diseases of the nervous system' (OR = 1.18, 95% CI = 1.10-1.26). Stratifying for birth characteristics, this difference diminishes, and for some diagnoses non-optimal twins seem to do slightly better than non-optimal singletons. Thus, twins with non-optimal birth characteristics had a lower risk of hospitalization than non-optimal singletons on, for example, 'Congenital anomalies' and 'Diseases of the nervous system' (OR = 0.86, 95% CI = 0.77-0.96; OR = 0.88, 95% CI = 0.81-0.97, respectively) and Total (any) hospitalization (OR = 0.87, 95% CI = 0.83-0.92). Among those with optimal birth characteristics, twins had an increased hospitalization due to 'External causes of illness' (OR = 1.07, 95% CI = 1.02-1.13) compared with optimal singletons. Twins have higher hospitalization rates than singletons. In stratifying for birth characteristics, this

  3. Digital Earth - A sustainable Earth

    Science.gov (United States)

    Mahavir

    2014-02-01

    All life, particularly human, cannot be sustainable, unless complimented with shelter, poverty reduction, provision of basic infrastructure and services, equal opportunities and social justice. Yet, in the context of cities, it is believed that they can accommodate more and more people, endlessly, regardless to their carrying capacity and increasing ecological footprint. The 'inclusion', for bringing more and more people in the purview of development is often limited to social and economic inclusion rather than spatial and ecological inclusion. Economic investment decisions are also not always supported with spatial planning decisions. Most planning for a sustainable Earth, be at a level of rural settlement, city, region, national or Global, fail on the capacity and capability fronts. In India, for example, out of some 8,000 towns and cities, Master Plans exist for only about 1,800. A chapter on sustainability or environment is neither statutorily compulsory nor a norm for these Master Plans. Geospatial technologies including Remote Sensing, GIS, Indian National Spatial Data Infrastructure (NSDI), Indian National Urban Information Systems (NUIS), Indian Environmental Information System (ENVIS), and Indian National GIS (NGIS), etc. have potential to map, analyse, visualize and take sustainable developmental decisions based on participatory social, economic and social inclusion. Sustainable Earth, at all scales, is a logical and natural outcome of a digitally mapped, conceived and planned Earth. Digital Earth, in fact, itself offers a platform to dovetail the ecological, social and economic considerations in transforming it into a sustainable Earth.

  4. Plate tectonics, mantle convection and D'' seismic structures

    Science.gov (United States)

    Wen, Lianxing

    This thesis adopts multidisciplinary (geodynamical and seismological) approaches toward understanding dynamics of the Earth's mantle. My geodynamical approach is directed at understanding the relationship between large-scale surface observables (geoid, topography, plate motions) and mantle rheology and convection of the present-day Earth. In chapter 2, I remove shallow mantle structure of various tectonic features to generate "residual tomography." In chapter 3, I show that the pattern, spectrum and amplitude of the "residual topography" are consistent with shallow origin of the "Earth surface dynamic topography;" the long wavelength geoid and topography (l = 2-3) are successfully explained by density models inferred from the "residual tomography," assuming layered mantle convection stratified at the "920 km seismic discontinuity." In chapter 4, I develop a new method to calculate mantle flow with lateral variation of viscosity. The viscosity contrast between continental and oceanic regions is identified to have dominating effects on both the observed poloidal/toroidal ratio and pattern of toroidal motions at long wavelengths. My seismological approach is focused on exploring fine structures near the core-mantle boundary (CMB) and developing new seismic techniques. I discuss the method development and strategies to explore fine structures in the following chapters. In chapter 5, I develop a hybrid method, a combination of analytical and numerical methods, with numerical methods applied in heterogeneous regions only. In chapter 6, I constrain the general structures of the ultra low velocity zones (ULVZ) near the CMB under the south-east Pacific and Iceland. The SKS-SPdKS data are explained by ULVZ with P-velocity reduction of 10%, horizontal length-scales of about 250 km and height of about 40 km. S-velocity reduction of 30% is consistent with the data. In chapter 7, I constrain the detailed structures of the ULVZ near the CMB from observed broadband PKP precursors

  5. Convective Replica-Exchange in Ergodic Regimes.

    Science.gov (United States)

    Signorini, Giorgio F; Giovannelli, Edoardo; Spill, Yannick G; Nilges, Michael; Chelli, Riccardo

    2014-03-11

    In a recent article (J. Comput. Chem. 2013, 34, 132-140), convective replica-exchange (convective-RE) has been presented as an alternative to the standard even-odd transition scheme. Computations on systems of various complexity have shown that convective-RE may increase the number of replica round-trips in temperature space with respect to the standard exchange scheme, leading to a more effective sampling of energy basins. Moreover, it has been shown that the method may prevent the formation of bottlenecks in the diffusive walk of replicas through the space of temperature states. By using an ideal temperature-RE model and a classical harmonic-oscillator RE scheme, we study the performances of convective-RE when ergodicity is not broken and convergence of acceptance probabilities is attained. In this dynamic regime, the round-trip ratio between convective and standard-RE is at maximum ∼ 1.5, a value much smaller than that observed in nonergodic simulations. For large acceptance probabilities, the standard-RE outperforms convective-RE. Our observations suggest that convective-RE can safely be used in either ergodic or non-ergodic regimes; however, convective-RE is advantageous only when bottlenecks occur in the state-space diffusion of replicas, or when acceptance probabilities are globally low. We also show that decoupling of the state-space dynamics of the stick replica from the dynamics of the remaining replicas improves the efficiency of convective-RE at low acceptance probability regimes.

  6. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 117; Issue 6. Volume 117, Issue 6. December 2008, pages 897-1002. pp 897-909. Urban effects of Chennai on sea breeze induced convection and precipitation · Matthew Simpson Sethu Raman R Suresh U C Mohanty · More Details Abstract Fulltext PDF. Doppler ...

  7. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 116; Issue 5. Volume 116, Issue 5. October 2007, pages 369-463. pp 369-384 ... pp 385-406. Link between convection and meridional gradient of sea surface temperature in the Bay of Bengal · D Shankar S R Shetye P V Joseph · More Details Abstract Fulltext PDF.

  8. Granular convection driven by shearing inertial forces.

    Science.gov (United States)

    Rodríguez-Liñán, G M; Nahmad-Molinari, Y

    2006-01-01

    Convection velocity measurements in vertically vibrated granular materials are presented. The convection velocity close to the walls grows quadratically with the difference between the maximum and critical, or excess, amplitude (proposed as a dynamic parameter to describe related problems) and it is shown numerically that the average bed-bottom relative velocity during the distancing between them, grows linearly with the squared as well. This is interpreted as the signature of an inertial shearing force or momentum transfer proportional to the bed-container relative velocity, acting mainly during the bed-plate distancing part of each cycle which leads to the formation of the convective flux.

  9. Transient Mixed Convection Validation for NGNP

    International Nuclear Information System (INIS)

    Smith, Barton; Schultz, Richard

    2015-01-01

    The results of this project are best described by the papers and dissertations that resulted from the work. They are included in their entirety in this document. They are: (1) Jeff Harris PhD dissertation (focused mainly on forced convection); (2) Blake Lance PhD dissertation (focused mainly on mixed and transient convection). This dissertation is in multi-paper format and includes the article currently submitted and one to be submitted shortly; and, (3) JFE paper on CFD Validation Benchmark for Forced Convection.

  10. Measuring Convective Mass Fluxes Over Tropical Oceans

    Science.gov (United States)

    Raymond, David

    2017-04-01

    Deep convection forms the upward branches of all large-scale circulations in the tropics. Understanding what controls the form and intensity of vertical convective mass fluxes is thus key to understanding tropical weather and climate. These mass fluxes and the corresponding conditions supporting them have been measured by recent field programs (TPARC/TCS08, PREDICT, HS3) in tropical disturbances considered to be possible tropical storm precursors. In reality, this encompasses most strong convection in the tropics. The measurements were made with arrays of dropsondes deployed from high altitude. In some cases Doppler radar provided additional measurements. The results are in some ways surprising. Three factors were found to control the mass flux profiles, the strength of total surface heat fluxes, the column-integrated relative humidity, and the low to mid-tropospheric moist convective instability. The first two act as expected, with larger heat fluxes and higher humidity producing more precipitation and stronger lower tropospheric mass fluxes. However, unexpectedly, smaller (but still positive) convective instability produces more precipitation as well as more bottom-heavy convective mass flux profiles. Furthermore, the column humidity and the convective instability are anti-correlated, at least in the presence of strong convection. On spatial scales of a few hundred kilometers, the virtual temperature structure appears to be in dynamic balance with the pattern of potential vorticity. Since potential vorticity typically evolves on longer time scales than convection, the potential vorticity pattern plus the surface heat fluxes then become the immediate controlling factors for average convective properties. All measurements so far have taken place in regions with relatively flat sea surface temperature (SST) distributions. We are currently seeking funding for a measurement program in the tropical east Pacific, a region that exhibits strong SST gradients and

  11. Transient Mixed Convection Validation for NGNP

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Barton [Utah State Univ., Logan, UT (United States); Schultz, Richard [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-10-19

    The results of this project are best described by the papers and dissertations that resulted from the work. They are included in their entirety in this document. They are: (1) Jeff Harris PhD dissertation (focused mainly on forced convection); (2) Blake Lance PhD dissertation (focused mainly on mixed and transient convection). This dissertation is in multi-paper format and includes the article currently submitted and one to be submitted shortly; and, (3) JFE paper on CFD Validation Benchmark for Forced Convection.

  12. The Behavior of Surface Wind and Thermodynamic Fields in the Presence of Deep Convection.

    Science.gov (United States)

    1981-05-01

    c’xc.: t :’" r 9 , ’ rp" -200- 0 100 6r 0 0 oo w0 -201- 0 30 July 1979 0 Confours Every t 30 x 16 see:’ 2000 CDT 0 0 0 ), km * Light Rain * Heav Rain0...of thunder- storms and squall lines. Ann. Rev. Earth Planet . Sci., 7, 117-161. Malkus, J., 1949: Effects of wind shear on some aspects of convection

  13. Inferring convective responses to El Niño with atmospheric electricity measurements at Shetland

    OpenAIRE

    Harrison, Giles; Joshi, Manoj; Pascoe, Kimberly

    2011-01-01

    Pacific ocean temperature anomalies associated with the El Niño–Southern Oscillation (ENSO) modulate atmospheric convection and hence thunderstorm electrification. The generated current flows globally via the atmospheric electric circuit, which can be monitored anywhere on Earth. Atmospheric electricity measurements made at Shetland (in Scotland) display a mean global circuit response to ENSO that is characterized by strengthening during 'El Niño' conditions, and weakening during 'La Niña' co...

  14. Magnetic reconnection during steady magnetospheric convection and other magnetospheric modes

    Directory of Open Access Journals (Sweden)

    B. Hubert

    2017-03-01

    Full Text Available We use remote sensing of the proton aurora with the IMAGE-FUV SI12 (Imager for Magnetopause to Aurora Global Exploration–Far Ultraviolet–Spectrographic Imaging at 121.8 nm instrument and radar measurements of the ionospheric convection from the SuperDARN (Super Dual Aurora Radar Network facility to estimate the open magnetic flux in the Earth's magnetosphere and the reconnection rates at the dayside magnetopause and in the magnetotail during intervals of steady magnetospheric convection (SMC. We find that SMC intervals occur with relatively high open magnetic flux (average  ∼  0.745 GWb, standard deviation  ∼  0.16 GWb, which is often found to be nearly steady, when the magnetic flux opening and closure rates approximately balance around 55 kV on average, with a standard deviation of 21 kV. We find that the residence timescale of open magnetic flux, defined as the ratio between the open magnetospheric flux and the flux closure rate, is roughly 4 h during SMCs. Interestingly, this number is approximately what can be deduced from the discussion of the length of the tail published by Dungey (1965, assuming a solar wind speed of  ∼  450 km s−1. We also infer an enhanced convection velocity in the tail, driving open magnetic flux to the nightside reconnection site. We compare our results with previously published studies in order to identify different magnetospheric modes. These are ordered by increasing open magnetic flux and reconnection rate as quiet conditions, SMCs, substorms (with an important overlap between these last two and sawtooth intervals.

  15. Is composition a critical dynamical element of mantle convection?

    Science.gov (United States)

    Davies, J. H.; Davies, D. R.; Wolstencroft, M. W.

    2009-04-01

    It is clear from observations of differentiation producing oceanic crust and depleted residue, and its ultimate subduction that compositional heterogeneity does exist in the mantle. An important question for mantle dynamics however, is how important is this composition? Compositional variations have been attributed to be critical for explaining many dynamical aspects of mantle upwellings as evidenced in hot-spots, such as their relative fixity (Jellinek and Manga, 2004) and non-steady upwelling velocity (Lin and van Keken, 2005). They have also been attributed to causing peaks in magma production. Our modeling work in spherical geometry shows that a wide variety of upwelling behaviour can be produced in models that have NO compositional variations and are only driven by thermal anomalies. The critical component of this family of models is a high, Earth-like Rayleigh number. Our models have also reproduced time varying magma production on a long time-scale in thermal convection models. The critical element is again a very high Rayleigh number, but this time combined with a realistic Clapeyron slope at the 660km discontinuity. Schuberth et al., 2009, have also shown that composition is not required to explain some of the seismic signatures of mantle convection models either, including at the base of the mantle. While, as stated initially, composition must play a role, we would argue that given that much of the supposedly ‘non-thermal' behaviour can be explained by thermal models that the simplest current paradigm is to assume thermally driven convection. A further advantage of this class of model is that there are fewer degrees of freedom in comparing the geodynamics models with seismology, and therefore tighter tests will be possible. While there are other arguments for compositional variations close to the core-mantle boundary and in the upper boundary / lithosphere; tests from simpler models could help to refine and bound the degree of compositional variation

  16. Electromagnetic weather in the near-earth space in dependence on solar wind parameters

    International Nuclear Information System (INIS)

    Belov, B.A.; Burtsev, Yu.A.; Dremukhina, L.A.; Papitashvili, V.O.

    1995-01-01

    Analysis of modern models of electrical and magnetic fields, electrical current and plasma convection is carried out with the purpose of quantitative description of the near-earth electrodynamic parameters. Possibility of utilizing such models simultaneously with radar and geomagnetic observations for continuous real time control of electromagnetic weather in the earth magnetosphere is considered. Refs. 24, refs. 3

  17. Convection in complex shaped vessel; Convection dans des enceintes de forme complexe

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-07-01

    The 8 november 2000, the SFT (Societe Francaise de Thermique) organized a technical day on the convection in complex shaped vessels. Nine papers have been presented in the domains of the heat transfers, the natural convection, the fluid distribution, the thermosyphon effect, the steam flow in a sterilization cycle and the transformers cooling. Eight papers are analyzed in ETDE and one paper dealing with the natural convection in spent fuels depository is analyzed in INIS. (A.L.B.)

  18. MODELING OF CONVECTIVE FLOWS IN PNEUMOBASED OBJECTS. Part 1

    Directory of Open Access Journals (Sweden)

    B. M. Khrustalyov

    2014-01-01

    Full Text Available A computer modeling process of three-dimensional forced convection proceeding from computation of thermodynamic parameters of pneumo basic buildings (pneumo supported structures is presented. The mathematical model of numerical computation method of temperature and velocity fields, pressure profile in the object is developed using the package Solid works and is provided by grid methods on specified software. Special Navier–Stokes, Clapeyron–Mendeleev, continuity and thermal-conductivity equations are used to calculate parameters in the building with four supply and exhaust channels. Differential equations are presented by algebraic equation systems, initial-boundary conditions are changed by differential conditions for mesh functions and their solutions are performed by algebraic operations. In this article the following is demonstrated: in pneumo basic buildings convective and heat flows are identical structures near the surfaces in unlimited space, but in single-multiply shells (envelopescirculation lines take place, geometrical sizes of which depend on thermal-physical characteristics of gas(airin envelopes, radiation reaction with heated surfaces of envelopes with  sphere, earth surface, neighboring buildings. Natural surveys of pneumo-basic buildings of different purposes were carried out in Minsk, in different cities of Belarus and Russia, including temperature fields of external and internal surfaces of air envelopes, relative humidity, thermal (heatflows, radiation characteristics and others.The results of research work are illustrated with diagrams of temperature, velocity, density and pressure dependent on coordinates and time.

  19. Convective Radio Occultations Final Campaign Summary

    Energy Technology Data Exchange (ETDEWEB)

    Biondi, R. [Atmospheric Radiation Measurement, Washington, DC (United States)

    2016-03-01

    Deep convective systems are destructive weather phenomena that annually cause many deaths and injuries as well as much damage, thereby accounting for major economic losses in several countries. The number and intensity of such phenomena have increased over the last decades in some areas of the globe. Damage is mostly caused by strong winds and heavy rain parameters that are strongly connected to the structure of the particular storm. Convection over land is usually stronger and deeper than over the ocean and some convective systems, known as supercells, also develop tornadoes through processes that remain mostly unclear. The intensity forecast and monitoring of convective systems is one of the major challenges for meteorology because in situ measurements during extreme events are too sparse or unreliable and most ongoing satellite missions do not provide suitable time/space coverage.

  20. Dynamics of acoustic-convective drying of sunflower cake

    Science.gov (United States)

    Zhilin, A. A.

    2017-10-01

    The dynamics of drying sunflower cake by a new acoustic-convective method has been studied. Unlike the conventional (thermal-convective) method, the proposed method allows moisture to be extracted from porous materials without applying heat to the sample to be dried. Kinetic curves of drying by the thermal-convective and acoustic-convective methods were obtained and analyzed. The advantages of the acoustic-convective extraction of moisture over the thermal-convective method are discussed. The relaxation times of drying were determined for both drying methods. An intermittent drying mode which improves the efficiency of acoustic-convective extraction of moisture is considered.

  1. Dynamics of a Snowball Earth ocean.

    Science.gov (United States)

    Ashkenazy, Yosef; Gildor, Hezi; Losch, Martin; Macdonald, Francis A; Schrag, Daniel P; Tziperman, Eli

    2013-03-07

    Geological evidence suggests that marine ice extended to the Equator at least twice during the Neoproterozoic era (about 750 to 635 million years ago), inspiring the Snowball Earth hypothesis that the Earth was globally ice-covered. In a possible Snowball Earth climate, ocean circulation and mixing processes would have set the melting and freezing rates that determine ice thickness, would have influenced the survival of photosynthetic life, and may provide important constraints for the interpretation of geochemical and sedimentological observations. Here we show that in a Snowball Earth, the ocean would have been well mixed and characterized by a dynamic circulation, with vigorous equatorial meridional overturning circulation, zonal equatorial jets, a well developed eddy field, strong coastal upwelling and convective mixing. This is in contrast to the sluggish ocean often expected in a Snowball Earth scenario owing to the insulation of the ocean from atmospheric forcing by the thick ice cover. As a result of vigorous convective mixing, the ocean temperature, salinity and density were either uniform in the vertical direction or weakly stratified in a few locations. Our results are based on a model that couples ice flow and ocean circulation, and is driven by a weak geothermal heat flux under a global ice cover about a kilometre thick. Compared with the modern ocean, the Snowball Earth ocean had far larger vertical mixing rates, and comparable horizontal mixing by ocean eddies. The strong circulation and coastal upwelling resulted in melting rates near continents as much as ten times larger than previously estimated. Although we cannot resolve the debate over the existence of global ice cover, we discuss the implications for the nutrient supply of photosynthetic activity and for banded iron formations. Our insights and constraints on ocean dynamics may help resolve the Snowball Earth controversy when combined with future geochemical and geological observations.

  2. Natural convection type BWR reactor

    International Nuclear Information System (INIS)

    Tobimatsu, Toshimi.

    1990-01-01

    In a natural convection type BWR reactor, a mixed stream of steams and water undergo a great flow resistance. In particular, pressure loss upon passing from an upper plenum to a stand pipe and pressure loss upon passing through rotational blades are great. Then, a steam dryer comprising laminated dome-like perforated plates and a drain pipe for flowing down separated water to a downcomer are disposed above a riser. The coolants heated in the reactor core are boiled, uprise in the riser as a gas-liquid two phase flow containing voids, release steams containing droplets from the surface of the gas-liquid two phase, flow into the steam dryer comprising the perforated plates and are separated into a gas and a liquid. The dried steams flow to a turbine passing through a main steam pipe and the condensated droplets flow down through the drain pipe and the downcomer to the lower portion of the reactor core. In this way, the conventional gas-liquid separator can be saved without lowering the quality of steam drying to reduce the pressure loss and to improve the operation performance. (N.H.)

  3. Controlling arbitrary humidity without convection.

    Science.gov (United States)

    Wasnik, Priyanka S; N'guessan, Hartmann E; Tadmor, Rafael

    2015-10-01

    In this paper we show a way that allows for the first time to induce arbitrary humidity of desired value for systems without convective flow. To enable this novelty we utilize a semi-closed environment in which evaporation is not completely suppressed. In this case, the evaporation rate is determined both by the outer (open) humidity and by the inner (semi-closed) geometry including the size/shape of the evaporating medium and the size/shape of the semi-closure. We show how such systems can be used to induce desired humidity conditions. We consider water droplet placed on a solid surface and study its evaporation when it is surrounded by other drops, hereon "satellite" drops and covered by a semi-closed hemisphere. The main drop's evaporation rate is proportional to its height, in agreement with theory. Surprisingly, however, the influence of the satellite drops on the main drop's evaporation suppression is not proportional to the sum of heights of the satellite drops. Instead, it shows proportionality close to the satellite drops' total surface area. The resultant humidity conditions in the semi-closed system can be effectively and accurately induced using different satellite drops combinations. Copyright © 2015 Elsevier Inc. All rights reserved.

  4. The structure and dynamics of patterns of Benard convection cells

    International Nuclear Information System (INIS)

    Rivier, N.; Imperial Coll. of Science and Technology, London; Lausanne Univ.

    1990-08-01

    Benard-Marangoni convection, in containers with large aspect ratio, exhibits space-filling cellular structures, highly deformable, but crystallized. They contain dislocations and grain boundaries generated and moved by elementary topological transformations, and are subjected to a weak shear stress due to the earth's rotation. The cellular structure and its fluctuations are analyzed from a crystallographic viewpoint, by using two complementary approaches. One is a global analysis of cellular structures in cylindrical symmetry. Their structural stability and defect pattern are obtained as topological mode-locking of a continuous structural parameter. The other, a local, molecular dynamics of the cells, gives a realistic parametrization of the forces and the transformations by generalizing the Voronoi cell construction in one extra dimension. 23 refs., 8 figs

  5. Added value of convection-permitting reanalyses

    Science.gov (United States)

    Wahl, S.; Keller, J. D.; Ohlwein, C.; Hense, A.; Friederichs, P.; Crewell, S.

    2016-12-01

    Atmospheric reanalyses are a state-of-the-art tool to generate consistent and realistic state estimates of the atmospheric system. They are used for validation of meteorological and hydrological models, climate monitoring, and renewable energy applications, amongst others. Current reanalyses are mainly global, while regional reanalyses are emerging for North America, the polar region, and most recently for Europe. Due to the horizontal resolution used, deep convection is still parameterized even in the regional reanalyses. However, convective parameterization is a major source of errors and uncertainties in atmospheric models. Therefore, it is expected that convection permitting reanalysis systems are able to adequately simulate the mechanisms leading to high-impact weather, notably heavy precipitation and winds related to deep moist convection. A novel convective-scale regional reanalysis system for Central Europe (COSMO-REA2) has been developed by the Hans-Ertel Center for Weather Research - Climate Monitoring Branch. The system is based on the COSMO model and uses a nudging scheme for the assimilation of observational data. In addition, radar-derived rain rates are assimilated through a latent heat nudging scheme. With a horizontal grid-spacing of 2 km, the model parameterization for deep moist convective processes is turned off. As we expect the largest benefit of the convection-permitting system for precipitation, the evaluation focuses on this essential climate variable (ECV). Furthermore, precipitation is crucial for climate monitoring purposes, e.g., in the form of extreme precipitation which is an major cause of severe damages and societal costs in Europe. This study illustrates the added value of the convective-scale reanalysis compared to coarser gridded regional European and global reanalyses.

  6. Combined convective heat transfer from short cylinders

    International Nuclear Information System (INIS)

    Oosthuizen, P.H.; Paul, J.T.

    1985-01-01

    Considerable experimental evidence has been produced recently showing that the free convective heat transfer rate from horizontal circular cylinders becomes influenced by the length to diameter ratio L/D. The major aim of the present study was to determine the influence of the L/D ratio on the conditions under which buoyancy forces cause the heat transfer rate to start to deviate significantly from that existing in purely forced convection

  7. Numerical Study of a Convective Turbulence Encounter

    Science.gov (United States)

    Proctor, Fred H.; Hamilton, David W.; Bowles, Roland L.

    2002-01-01

    A numerical simulation of a convective turbulence event is investigated and compared with observational data. The specific case was encountered during one of NASA's flight tests and was characterized by severe turbulence. The event was associated with overshooting convective turrets that contained low to moderate radar reflectivity. Model comparisons with observations are quite favorable. Turbulence hazard metrics are proposed and applied to the numerical data set. Issues such as adequate grid size are examined.

  8. A comparison of perinatal outcomes in singletons and multiples born after in vitro fertilization or intracytoplasmic sperm injection stratified for neonatal risk criteria

    NARCIS (Netherlands)

    van Heesch, M.M.J.; Evers, J.L.H.; Dumoulin, J.C.M.; van der Hoeven, M.A.H.B.; van Beijsterveldt, C.E.M.; Bonsel, G.J.; Dykgraaf, R.H.M.; van Goudoever, J.B.; Koopman-Esseboom, C.; Nelen, W.L.D.M.; Steiner, K.; Tamminga, P.; Tonch, N.; van Zonneveld, P.; Dirksen, C.D.

    2014-01-01

    Objective To compare perinatal singleton and multiple outcomes in a large Dutch in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) population and within risk subgroups. Newborns were assigned to a risk category based on gestational age, birthweight, Apgar score and congenital

  9. A comparison of perinatal outcomes in singletons and multiples born after in vitro fertilization or intracytoplasmic sperm injection stratified for neonatal risk criteria

    NARCIS (Netherlands)

    Heesch, M.M. van; Evers, J.L.H.; Dumoulin, J.C.; Hoeven, M.A. van der; Beijsterveldt, C.E. van; Bonsel, G.J.; Dykgraaf, R.H.; Goudoever, J.B. van; Koopman-Esseboom, C.; Nelen, W.L.D.M.; Steiner, K.; Tamminga, P.; Tonch, N.; Zonneveld, P. van; Dirksen, C.D.

    2014-01-01

    OBJECTIVE: To compare perinatal singleton and multiple outcomes in a large Dutch in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) population and within risk subgroups. Newborns were assigned to a risk category based on gestational age, birthweight, Apgar score and congenital

  10. Clinical Significance of Preterm Singleton Pregnancies Complicated by Placental Abruption following Preterm Premature Rupture of Membranes Compared with Those without p-PROM

    Science.gov (United States)

    Suzuki, Shunji

    2012-01-01

    The purpose of this paper was to examine the obstetric and neonatal outcomes of preterm singleton pregnancies complicated by placental abruption following preterm premature rupture of membranes (p-PROM) compared with those without p-PROM. We reviewed the obstetric records of 95 singleton deliveries complicated by placental abruption at 22–36 weeks' gestation. The incidence of placental abruption in singleton pregnancies with p-PROM was 4.7%, and the crude odds ratio of placental abruption for women following p-PROM was 6.50 (P < 0.01). Of the 95 cases of placental abruption in preterm singleton deliveries, 64 cases (67.4%) occurred without p-PROM and 31 cases (32.6%) occurred following p-PROM. The incidence of histological chorioamnionitis stage III in the patients following p-PROM was significantly higher than that in the patients without p-PROM (P = 0.02). The rate of emergency Cesarean deliveries associated with nonreassuring fetal status (NRFS) in the patients following p-PROM was significantly lower than that in the patients without p-PROM. However, there were no significant differences in the maternal and neonatal outcomes between the patients with and without p-PROM. Although p-PROM may be one of important risk factors for placental abruption associated with chorioamnionitis, it may not influence the perinatal outcomes in preterm placental abruption. PMID:22690341

  11. Neonatal and maternal outcomes comparing women undergoing two in vitro fertilization (IVF) singleton pregnancies and women undergoing one IVF twin pregnancy.

    Science.gov (United States)

    Sazonova, Antonina; Källen, Karin; Thurin-Kjellberg, Ann; Wennerholm, Ulla-Britt; Bergh, Christina

    2013-03-01

    To compare outcomes for women undergoing two in vitro fertilization (IVF) pregnancies with singletons and women undergoing one IVF twin pregnancy. The concept of single-embryo transfer in IVF has reduced the risks of both maternal and neonatal complications, but there is still a discussion of whether or not twins are a desired outcome of IVF. Registry study. Not applicable. All reported twins after IVF with double-embryo transfer (n = 1,982) and their mothers (n = 991) and all mothers (n = 921) who gave birth to two IVF singletons (n = 1,842). None. Maternal and neonatal outcomes including severe neonatal morbidity. Preterm birth, very preterm birth, low birth weight, very low birth weight, and small for gestational age were dramatically increased for IVF twins compared with two IVF singletons with the same mother, with adjusted odds ratios from 4 to 16. Significantly higher rates of respiratory complications, sepsis, and jaundice were detected among the IVF twins. Significantly higher rates of preeclampsia, preterm premature rupture of the membranes, and cesarean section were observed for IVF twin pregnancies. The neonatal and maternal outcomes were dramatically better for women undergoing two IVF singleton pregnancies compared with one IVF twin pregnancy after double-embryo transfer. These results support single-embryo transfer to minimize the risks associated with twin pregnancies. Copyright © 2013 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

  12. Outcome of Multifetal Pregnancy Reduction in Women with a Dichorionic Triamniotic Triplet Pregnancy to a Singleton Pregnancy : A Retrospective Nationwide Cohort Study

    NARCIS (Netherlands)

    Van De Mheen, L.; Everwijn, S. M P; Haak, M. C.; Manten, G. T R; Zondervan, H. A.; Knapen, M. F C M; Engels, M. A J; Erwich, J. J H M; Coumans, A. B.; Van Vugt, J. M G; Bilardo, C. M.; Van Pampus, M. G.; De Groot, C. J M; Mol, B. W J; Pajkrt, E.

    2016-01-01

    Objective: To study the pregnancy outcomes of women with a dichorionic triamniotic triplet pregnancy that was reduced to a singleton pregnancy and to review the literature. Methods: We performed a nationwide retrospective cohort study. We compared time to delivery and perinatal mortality in

  13. Outcome of Multifetal Pregnancy Reduction in Women with a Dichorionic Triamniotic Triplet Pregnancy to a Singleton Pregnancy: A Retrospective Nationwide Cohort Study

    NARCIS (Netherlands)

    van de Mheen, L.; Everwijn, S. M. P.; Haak, M. C.; Manten, G. T. R.; Zondervan, H. A.; Knapen, M. F. C. M.; Engels, M. A. J.; Erwich, J. J. H. M.; Coumans, A. B.; van Vugt, J. M. G.; Bilardo, C. M.; van Pampus, M. G.; de Groot, C. J. M.; Mol, B. W. J.; Pajkrt, E.

    2016-01-01

    To study the pregnancy outcomes of women with a dichorionic triamniotic triplet pregnancy that was reduced to a singleton pregnancy and to review the literature. We performed a nationwide retrospective cohort study. We compared time to delivery and perinatal mortality in dichorionic triplet

  14. Outcome of Multifetal Pregnancy Reduction in Women with a Dichorionic Triamniotic Triplet Pregnancy to a Singleton Pregnancy : A Retrospective Nationwide Cohort Study

    NARCIS (Netherlands)

    van de Mheen, L.; Everwijn, S. M. P.; Haak, M. C.; Manten, G. T. R.; Zondervan, H. A.; Knapen, M. F. C. M.; Engels, M. A. J.; Erwich, J. J. H. M.; Coumans, A. B.; van Vugt, J. M. G.; Bilardo, C. M.; van Pampus, M. G.; de Groot, C. J. M.; Mol, B. W. J.; Pajkrt, E.

    2016-01-01

    Objective:To study the pregnancy outcomes of women with a dichorionic triamniotic triplet pregnancy that was reduced to a singleton pregnancy and to review the literature. Methods: We performed a nationwide retrospective cohort study. We compared time to delivery and perinatal mortality in

  15. Increased time to pregnancy is associated with less optimal neurological condition in 4-year-old singletons, in vitro fertilization itself is not

    NARCIS (Netherlands)

    Schendelaar, P.; van den Heuvel, Edwin; Heineman, M. J.; La Bastide-Van Gemert, S.; Middelburg, K. J.; Seggers, Jorien; Hadders-Algra, M.

    2014-01-01

    STUDY QUESTION: Does ovarian hyperstimulation, the in vitro procedures required for in vitro fertilization (IVF)/intracytoplasmic sperm injection or the combination of both, affect the neurological outcome of 4-year-old singletons? SUMMARY ANSWER: Ovarian hyperstimulation, the in vitro procedure and

  16. Increased time to pregnancy is associated with less optimal neurological condition in 4-year-old singletons, in vitro fertilization itself is not

    NARCIS (Netherlands)

    Schendelaar, P.; van den Heuvel, E. R.; Heineman, M. J.; La Bastide-van Gemert, S.; Middelburg, K. J.; Seggers, J.; Hadders-Algra, M.

    2014-01-01

    Does ovarian hyperstimulation, the in vitro procedures required for in vitro fertilization (IVF)/ intracytoplasmic sperm injection or the combination of both, affect the neurological outcome of 4-year-old singletons? Ovarian hyperstimulation, the in vitro procedure and the combination of both, were

  17. Loop electrosurgical excision of the cervix and subsequent risk for spontaneous preterm delivery: a population-based study of singleton deliveries during a 9-year period

    DEFF Research Database (Denmark)

    Noehr, Bugge; Jensen, Allan; Frederiksen, Kirsten

    2009-01-01

    OBJECTIVE: Our aim was to assess the association between loop electrosurgical excision procedure (LEEP) and the subsequent risk for spontaneous preterm delivery, with the use of population-based data from various nationwide registries. STUDY DESIGN: The study population consisted of all singleton...

  18. CONVECTION IN CONDENSIBLE-RICH ATMOSPHERES

    Energy Technology Data Exchange (ETDEWEB)

    Ding, F. [Department of the Geophysical Sciences, University of Chicago, Chicago, IL 60637 (United States); Pierrehumbert, R. T., E-mail: fding@uchicago.edu [Department of Physics, University of Oxford, Oxford OX1 3PU (United Kingdom)

    2016-05-01

    Condensible substances are nearly ubiquitous in planetary atmospheres. For the most familiar case—water vapor in Earth’s present climate—the condensible gas is dilute, in the sense that its concentration is everywhere small relative to the noncondensible background gases. A wide variety of important planetary climate problems involve nondilute condensible substances. These include planets near or undergoing a water vapor runaway and planets near the outer edge of the conventional habitable zone, for which CO{sub 2} is the condensible. Standard representations of convection in climate models rely on several approximations appropriate only to the dilute limit, while nondilute convection differs in fundamental ways from dilute convection. In this paper, a simple parameterization of convection valid in the nondilute as well as dilute limits is derived and used to discuss the basic character of nondilute convection. The energy conservation properties of the scheme are discussed in detail and are verified in radiative-convective simulations. As a further illustration of the behavior of the scheme, results for a runaway greenhouse atmosphere for both steady instellation and seasonally varying instellation corresponding to a highly eccentric orbit are presented. The latter case illustrates that the high thermal inertia associated with latent heat in nondilute atmospheres can damp out the effects of even extreme seasonal forcing.

  19. Mortality among twins and singletons in sub-Saharan Africa between 1995 and 2014: a pooled analysis of data from 90 Demographic and Health Surveys in 30 countries.

    Science.gov (United States)

    Monden, Christiaan W S; Smits, Jeroen

    2017-07-01

    Sub-Saharan Africa has the world's highest under-5 and neonatal mortality rates as well as the highest naturally occurring twin rates. Twin pregnancies carry high risk for children and mothers. Under-5 mortality has declined in sub-Saharan Africa over the last decades. It is unknown whether twins have shared in this reduction. We pooled data from 90 Demographic and Health Surveys for 30 sub-Saharan Africa countries on births reported between 1995 and 2014. We used information on 1 685 110 singleton and 56 597 twin livebirths to compute trends in mortality rates for singletons and twins. We examined whether the twin-singleton rate ratio can be attributed to biological, socioeconomic, care-related factors, or birth size, and estimated the mortality burden among sub-Saharan African twins. Under-5 mortality among twins has declined from 327·7 (95% CI 312·0-343·5) per 1000 livebirths in 1995-2001 to 213·0 (196·7-229·2) in 2009-14. This decline of 35·0% was much less steep than the 50·6% reduction among singletons (from 128·6 [95% CI 126·4-130·8] per 1000 livebirths in 1995-2001 to 63·5 [61·6-65·3] in 2009-14). Twins account for an increasing share of under-5 deaths in sub-Saharan Africa: currently 10·7% of under-5 mortality and 15·1% of neonatal mortality. We estimated that about 315 000 twins (uncertainty interval 289 000-343 000) die in sub-Saharan African each year. Excess twin mortality cannot be explained by common risk factors for under-5 mortality, including birthweight. The difference with singletons was especially stark for neonatal mortality (rate ratio 5·0, 95% CI 4·5-5·6). 51·7% of women pregnant with twins reported receiving medical assistance at birth. The fate of twins in sub-Saharan Africa is lagging behind that of singletons. An alarming one-fifth of twins in the region dies before age 5 years, three times the mortality rate among singletons. Twins account for a substantial and growing share of under-5 and neonatal

  20. Stirring up a storm: convective climate variability on tidally locked exoplanets

    Science.gov (United States)

    Koll, D. D. B.; Cronin, T.

    2017-12-01

    Earth-sized exoplanets are extremely common in the galaxy and many of them are likely tidally locked, such that they have permanent day- and nightsides. Astronomers have started to probe the atmospheres of such planets, which raises the question: can tidally locked planets support habitable climates and life?Several studies have explored this question using global circulation models (GCMs). Not only did these studies find that tidally locked Earth analogs can indeed sustain habitable climates, their large day-night contrast should also create a distinct cloud structure that could help astronomers identify such planets. These studies, however, relied on GCMs which do not explicitly resolve convection, raising the question of how robust their results are.Here we consider the dynamics of clouds and convection on a tidally locked planet using the System for Atmospheric Modeling (SAM) cloud-resolving model. We simulate a 3d `channel', representing an equatorial strip that covers both day- and nightside of a tidally locked planet. We use interactive radiation and an interactive slab ocean surface and investigate the response to changes in the stellar constant. We find mean climates that are broadly comparable to those produced by a GCM. However, when the slab ocean is shallow, we also find internal variability that is far bigger than in a GCM. Convection in a tidally locked domain can self-organize in a dramatic fashion, with large outbursts of convection followed by periods of relative calm. We show that one of the timescales for this behavior is set by the time it takes for a dry gravity wave to travel between day- and nightside. The quasi-periodic self-organization of clouds can vary the planetary albedo by up to 50%. Changes this large are potentially detectable with future space telescopes, which raises the prospect of using convectively driven variability to identify high priority targets in the search for life around other stars.

  1. Entropy Production in Convective Hydrothermal Systems

    Science.gov (United States)

    Boersing, Nele; Wellmann, Florian; Niederau, Jan

    2016-04-01

    Exploring hydrothermal reservoirs requires reliable estimates of subsurface temperatures to delineate favorable locations of boreholes. It is therefore of fundamental and practical importance to understand the thermodynamic behavior of the system in order to predict its performance with numerical studies. To this end, the thermodynamic measure of entropy production is considered as a useful abstraction tool to characterize the convective state of a system since it accounts for dissipative heat processes and gives insight into the system's average behavior in a statistical sense. Solving the underlying conservation principles of a convective hydrothermal system is sensitive to initial conditions and boundary conditions which in turn are prone to uncertain knowledge in subsurface parameters. There exist multiple numerical solutions to the mathematical description of a convective system and the prediction becomes even more challenging as the vigor of convection increases. Thus, the variety of possible modes contained in such highly non-linear problems needs to be quantified. A synthetic study is carried out to simulate fluid flow and heat transfer in a finite porous layer heated from below. Various two-dimensional models are created such that their corresponding Rayleigh numbers lie in a range from the sub-critical linear to the supercritical non-linear regime, that is purely conductive to convection-dominated systems. Entropy production is found to describe the transient evolution of convective processes fairly well and can be used to identify thermodynamic equilibrium. Additionally, varying the aspect ratio for each Rayleigh number shows that the variety of realized convection modes increases with both larger aspect ratio and higher Rayleigh number. This phenomenon is also reflected by an enlarged spread of entropy production for the realized modes. Consequently, the Rayleigh number can be correlated to the magnitude of entropy production. In cases of moderate

  2. Hydrogen in the Deep Earth

    Science.gov (United States)

    Mookherjee, M.; Hermann, A.; Bajgain, S.; Shukla, G.

    2017-12-01

    Water is crucial for the sustenance of planetary activities. For instance, water reduces melting temperatures and affects the density and elasticity of minerals and melts. It also influences the transport properties of minerals and melts, including their diffusion, electrical conductivity, and rheology. The solid-state mantle convection for the water-free, dry silicate mantle is likely to be extremely sluggish and may not be sustainable over geological timescales. Therefore, it is important to identify the potential hosts for water and estimate the size of the hidden reservoir of water in the deep Earth. Also, it is important to correlate how the deep Earth water reservoir, i.e., the degree of mantle hydration, influences the global sea level over geological time scales. Constraining the degree of mantle hydration is not straightforward. It requires understanding and linking atomistic scale behavior of minerals and melts to large-scale geophysical and geochemical observations. High-pressure experiments and first-principles simulations based on density functional theory (DFT) have been crucial in enhancing our understanding of hydrogen bearing mineral phases that are likely to be present in the Earth's mantle and subduction zone settings. In this study we present DFT results on hydrous phases and provide constraints on the crystal structure, thermodynamic stability, elasticity, and transport properties of proton bearing mineral phases. Acknowledgements: MM acknowledges US NSF awards EAR-1639552 and EAR-1634422.

  3. Experimental observation of the influence of furnace temperature profile on convection and segregation in the vertical Bridgman crystal growth technique

    Science.gov (United States)

    Neugebauer, G. T.; Wilcox, William R.

    1992-01-01

    Azulene-doped naphthalene was directionally solidified during the vertical Bridgman-Stockbarger technique. Doping homogeneity and convection were determined as a function of the temperature profile in the furnace and the freezing rate. Convection velocities were two orders of magnitude lower when the temperature increased with height. Rarely was the convection pattern axisymmetric, even though the temperature varied less than 0.1 K around the circumference of the growth ampoule. Correspondingly the cross sectional variation in azulene concentration tended to be asymmetric, especially when the temperature increased with height. This cross sectional variation changed dramatically along the ingot, reflecting changes in convection presumably due to the decreasing height of the melt. Although there was large scatter and irreproducibility in the cross sectional variation in doping, this variation tended to be least when the growth rate was low and the convection was vigorous. It is expected that compositional variations would also be small at high growth rates with weak convection and flat interfaces, although this was not investigated in the present experiments. Neither rotation of the ampoule nor deliberate introduction of thermal asymmetries during solidification had a significant influence on cross sectional variations in doping. It is predicted that slow directional solidification under microgravity conditions could produce greater inhomogeneities than on Earth. Combined use of microgravity and magnetic fields would be required to achieve homogeneity when it is necessary to freeze slowly in order to avoid constitutional supercooling.

  4. Preliminary three-dimensional model of mantle convection with deformable, mobile continental lithosphere

    Science.gov (United States)

    Yoshida, Masaki

    2010-06-01

    Characteristic tectonic structures such as young orogenic belts and suture zones in a continent are expected to be mechanically weaker than the stable part of the continental lithosphere with the cratonic root (or cratonic lithosphere) and yield lateral viscosity variations in the continental lithosphere. In the present-day Earth's lithosphere, the pre-existing, mechanically weak zones emerge as a diffuse plate boundary. However, the dynamic role of a weak (low-viscosity) continental margin (WCM) in the stability of continental lithosphere has not been understood in terms of geophysics. Here, a new numerical simulation model of mantle convection with a compositionally and rheologically heterogeneous, deformable, mobile continental lithosphere is presented for the first time by using three-dimensional regional spherical-shell geometry. A compositionally buoyant and highly viscous continental assemblage with pre-existing WCMs, analogous to the past supercontinent, is modeled and imposed on well-developed mantle convection whose vigor of convection, internal heating rate, and rheological parameters are appropriate for the Earth's mantle. The visco-plastic oceanic lithosphere and the associated subduction of oceanic plates are incorporated. The time integration of the advection of continental materials with zero chemical diffusion is performed by a tracer particle method. The time evolution of mantle convection after setting the model supercontinent is followed over 800 Myr. Earth-like continental drift is successfully reproduced, and the characteristic thermal interaction between the mantle and the continent/supercontinent is observed in my new numerical model. Results reveal that the WCM protects the cratonic lithosphere from being stretched by the convecting mantle and may play a significant role in the stability of the cratonic lithosphere during the geological timescale because it acts as a buffer that prevents the cratonic lithosphere from undergoing global

  5. Sensitivity of Coupled Tropical Pacific Model Biases to Convective Parameterization in CESM1

    Science.gov (United States)

    Woelfle, M. D.; Yu, S.; Bretherton, C. S.; Pritchard, M. S.

    2018-01-01

    Six month coupled hindcasts show the central equatorial Pacific cold tongue bias development in a GCM to be sensitive to the atmospheric convective parameterization employed. Simulations using the standard configuration of the Community Earth System Model version 1 (CESM1) develop a cold bias in equatorial Pacific sea surface temperatures (SSTs) within the first two months of integration due to anomalous ocean advection driven by overly strong easterly surface wind stress along the equator. Disabling the deep convection parameterization enhances the zonal pressure gradient leading to stronger zonal wind stress and a stronger equatorial SST bias, highlighting the role of pressure gradients in determining the strength of the cold bias. Superparameterized hindcasts show reduced SST bias in the cold tongue region due to a reduction in surface easterlies despite simulating an excessively strong low-level jet at 1-1.5 km elevation. This reflects inadequate vertical mixing of zonal momentum from the absence of convective momentum transport in the superparameterized model. Standard CESM1simulations modified to omit shallow convective momentum transport reproduce the superparameterized low-level wind bias and associated equatorial SST pattern. Further superparameterized simulations using a three-dimensional cloud resolving model capable of producing realistic momentum transport simulate a cold tongue similar to the default CESM1. These findings imply convective momentum fluxes may be an underappreciated mechanism for controlling the strength of the equatorial cold tongue. Despite the sensitivity of equatorial SST to these changes in convective parameterization, the east Pacific double-Intertropical Convergence Zone rainfall bias persists in all simulations presented in this study.

  6. Convection and exchangers in variable regime; Convection et echangeurs en regime variable

    Energy Technology Data Exchange (ETDEWEB)

    Bagui, F.; Abdelghani-Idrissi, M.A. [Rouen Univ. IUT, Centre de Developpement Durable, 76 - Mont Saint Aignan (France); Bagui, F. [Ecole d' Ingenieurs CESI, 76 - Mont Saint Aignan (France); Desmet, B.; Lalot, S.; Harmand, S. [Valenciennes et du Hainaut-Cambresis Univ., Lab. de Mecanique et Energetique, 59 - Valenciennes (France); Maillet, D. [Institut National Polytechnique, INPL-UHP Nancy-1, LEMTA-CNRS UMR 7563, 54 - Vandoeuvre les Nancy (France)

    2005-07-01

    This session about convection and exchangers in variable regime gathers three articles dealing with: the transient regimes of tubular heat exchangers; heat exchangers and convection in non-permanent regime; and the limitations of the H coefficient: two short-time and short-scale examples. (J.S.)

  7. Delivery of double singleton pregnancies in a woman with a double uterus, double cervix, and complete septate vagina.

    Science.gov (United States)

    Yang, Ming-Jie; Tseng, Jen-Yu; Chen, Chih-Yao; Li, Hsin-Yang

    2015-12-01

    Uterine anomalies involving a double uterus, double cervix, also known as didelphys uterus, and complete septate vagina are rarely seen and have an associated fertility problem. However, artificial reproductive technology with embryo transfers can help solve this fertility challenge. Conception in the uterus in just one side is commonly seen for embryos, which are always transferred through the usually used (dilated) vagina. We here present a patient with the above uterine anomaly who conceived with the aid of in vitro fertilization and embryo transfer to both uterine cavities under general anesthesia, which resulted in successful double singleton pregnancies with one fetus in each uterus. With intensive prenatal care, the pregnancy course for each fetus was rather uneventful. Although both fetuses were in cephalic presentation, cesarean section was performed at the 39(th) week of gestation with good outcomes in order to preclude anticipated difficulties if the baby had been delivered through the rarely dilated vagina. However, order of birth between the two fetuses was a crucial decision during the operation. Copyright © 2015. Published by Elsevier Taiwan.

  8. Maternal and fetal arterial blood gas data in normotensive, singleton, isoflurane anesthetized sheep at 124-126 days of gestation.

    Science.gov (United States)

    Loughran, Claire M; Kemp, Matthew W; Musk, Gabrielle C

    2017-07-01

    The aim of this case series was to describe the differences between maternal and fetal blood-gas results during anesthesia. Sixteen singleton adult merino ewes weighing 60.1 ± 5.1 kg at 125.7 d (124 to 126 d) gestation were anesthetized. Maternal (radial) and fetal (umbilical) arterial blood gas samples were collected 79 ± 6 min after the start of anesthesia if maternal mean arterial pressure (MAP) was stable and > 65 mmHg. Fetal pH, partial arterial pressure of oxygen ( P aO 2 ), glucose, arterial hemoglobin oxygen saturation (SaO 2 ), sodium, and chloride were significantly lower and fetal partial arterial pressure of carbon dioxide ( P aCO 2 ), lactate, hematocrit, total hemoglobin, potassium, and calcium were significantly higher than maternal blood-gas values. Fetal pH, P aO 2 , and BE were lower and fetal lactate was higher than fetal umbilical arterial samples previously reported, which may indicate a non-reassuring fetal status. Further refinement of the ovine experimental model is warranted with fetal monitoring during maternal anesthesia.

  9. References of birth weights for gestational age and sex from a large cohort of singleton births in cameroon.

    Science.gov (United States)

    Kemfang Ngowa, Jean Dupont; Domkam, Irénée; Ngassam, Anny; Nguefack-Tsague, Georges; Dobgima Pisoh, Walter; Noa, Cyrille; Kasia, Jean Marie

    2014-01-01

    Objective. To establish the percentile charts of birth weights for gestational age and sex within the Cameroonian population. Methods. A review of medical records of infants born between January 2007 and December 2011 at the maternities of two hospitals in Cameroon, Central Africa. Multiple pregnancies, births of HIV infected women, stillbirths, and births with major fetal malformations were excluded. The smooth curves of birth weight for gestational age and sex were created using the Gamlss package under R.3.0.1 software. Results. The birth weights of 12837 live birth singleton infants born to HIV negative women between 28 and 42 weeks of gestation were analyzed to construct the birth weight curves for gestational age and sex. The smoothed percentile curves of birth weights for gestational age and sex of Cameroonian infants have demonstrated an increasing slope until 40 weeks and then a plateau. There was a varied difference of distribution in birth weights for gestational age between Cameroonian, Botswanan, American, and French infants. Conclusion. We established the reference curves of birth weights for gestational age and sex for Cameroonians. The difference in birth weight curves noted between Cameroonian, Botswanan, American, and French infants suggests the importance of establishing the regional birth weight norms.

  10. References of Birth Weights for Gestational Age and Sex from a Large Cohort of Singleton Births in Cameroon

    Directory of Open Access Journals (Sweden)

    Jean Dupont Kemfang Ngowa

    2014-01-01

    Full Text Available Objective. To establish the percentile charts of birth weights for gestational age and sex within the Cameroonian population. Methods. A review of medical records of infants born between January 2007 and December 2011 at the maternities of two hospitals in Cameroon, Central Africa. Multiple pregnancies, births of HIV infected women, stillbirths, and births with major fetal malformations were excluded. The smooth curves of birth weight for gestational age and sex were created using the Gamlss package under R.3.0.1 software. Results. The birth weights of 12837 live birth singleton infants born to HIV negative women between 28 and 42 weeks of gestation were analyzed to construct the birth weight curves for gestational age and sex. The smoothed percentile curves of birth weights for gestational age and sex of Cameroonian infants have demonstrated an increasing slope until 40 weeks and then a plateau. There was a varied difference of distribution in birth weights for gestational age between Cameroonian, Botswanan, American, and French infants. Conclusion. We established the reference curves of birth weights for gestational age and sex for Cameroonians. The difference in birth weight curves noted between Cameroonian, Botswanan, American, and French infants suggests the importance of establishing the regional birth weight norms.

  11. Perinatal outcome of singleton siblings born after assisted reproductive technology and spontaneous conception: Danish national sibling-cohort study.

    Science.gov (United States)

    Henningsen, Anna-Karina Aaris; Pinborg, Anja; Lidegaard, Øjvind; Vestergaard, Christina; Forman, Julie Lyng; Andersen, Anders Nyboe

    2011-03-01

    To compare the perinatal outcome of singleton siblings conceived differently. National population-based registry study. Denmark, from 1994 to 2008. Pairs of siblings (13,692 pairs; n = 27,384 children) conceived after IVF, intracytoplasmatic sperm injection (ICSI), frozen embryo replacement (FER), or spontaneous conception subcategorized into five groups according to succession: [1] IVF-ICSI vs. spontaneous conception (n = 7,758), [2] IVF-ICSI vs. FER (n = 716), [3] FER vs. FER (n = 34), [4] IVF-ICSI vs. IVF-ICSI (n = 2,876), and [5] spontaneous conception vs. spontaneous conception (n = 16,000). Observations were obtained from national registries. Birth weight, gestational age, low birth weight (conception method. Higher risk of low birth weight with (odds ratio [OR], 1.4; 95%CI, 1.1-1.7] and preterm birth (OR, 1.3; 95% CI, 1.1-1.6] was observed in IVF/ICSI compared with spontaneous conception. When differentiating between order and mode of conception, it seems that assisted reproductive technology plays a role in mean birth weight and risk of low birth weight and preterm birth. Birth weight was higher in siblings born after FER compared with fresh embryos replacement. Copyright © 2011 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

  12. Amnioinfusion for women with a singleton breech presentation and a previous failed external cephalic version: a randomized controlled trial.

    Science.gov (United States)

    Diguisto, Caroline; Winer, Norbert; Descriaud, Celine; Tavernier, Elsa; Weymuller, Victoire; Giraudeau, Bruno; Perrotin, Franck

    2018-04-01

    Our trial aimed to assess the effectiveness of amnioinfusion for a second attempt at external cephalic version (ECV). This open randomized controlled trial was planned with a sequential design. Women at a term ≥36 weeks of gestation with a singleton fetus in breech presentation and a first unsuccessful ECV were recruited in two level-3 maternity units. They were randomly allocated to transabdominal amnioinfusion with a 500-mL saline solution under ultrasound surveillance or no amnioinfusion before the second ECV attempt. Trained senior obstetricians performed all procedures. The primary outcome was the cephalic presentation rate at delivery. Analyses were conducted according to intention to treat (NCT00465712). Recruitment difficulties led to stopping the trial after a 57-month period, 119 women were randomized: 59 allocated to amnioinfusion + ECV and 60 to ECV only. Data were analyzed without applying the sequential feature of the design. The rate of cephalic presentation at delivery did not differ significantly according to whether the second version attempt was or was not preceded by amnioinfusion (20 versus 12%, p = .20). Premature rupture of the membranes occurred for 15% of the women in the amnioinfusion group. Amnioinfusion before a second attempt to external version does not significantly increase the rate of cephalic presentation at delivery.

  13. Limitations of the equivalence between spatial and ensemble estimators in the case of a single-tone excitation.

    Science.gov (United States)

    Monsef, Florian; Cozza, Andrea

    2011-10-01

    The ensemble-average value of the mean-square pressure is often assessed by using the spatial-average technique, underlying an equivalence principle between spatial and ensemble estimators. Using the ideal-diffuse-field model, the accuracy of the spatial-average method has been studied theoretically forty years ago in the case of a single-tone excitation. This study is revisited in the present work on the basis of a more realistic description of the sound field accounting for a finite number of plane waves. The analysis of the spatial-average estimator is based on the study of its convergence rate. Using experimental data from practical examples, it is shown that the classical expression underestimates the estimator uncertainty even for frequencies greater than Schroeder's frequency, and that the number of plane waves may act as lower bound on the spatial-average estimator accuracy. The comparison of the convergence rate with an ensemble-estimator shows that the two statistics cannot be regarded as equivalent in a general case. © 2011 Acoustical Society of America

  14. Total and differential leukocyte count percentiles in healthy singleton term women during the first stage of labor.

    Science.gov (United States)

    Lurie, Samuel; Weiner, Eran; Golan, Abraham; Sadan, Oscar

    2014-01-01

    To establish leukocyte count and differential percentiles in healthy singleton term laboring women during spontaneous normal vaginal labor following an uncomplicated pregnancy. An analysis of the records of all women (n = 762) who delivered at our delivery ward during a 2-month period was performed. After exclusion for cesarean delivery, induction of labor, pregnancy complications, preterm labor, multiple pregnancy, fever on admission, and lack of full blood count on admission, 365 parturient women during the 1st stage of labor were included in the final analysis. The total and differential leukocyte counts were determined by standard procedure by an automated cell counter. The leukocyte count range on admission to the delivery ward during the 1st stage of labor in healthy parturient women was between 4.4 × and 21.7 × 10(3)/µl and the 99th percentile limit was 20.06 × 10(3)/µl. The total leukocyte count was not influenced by cervical dilatation, ruptured membranes, or the presence and regularity of uterine contractions. An observed leukocyte count within the 99th percentile limit (20.06 × 10(3)/µl) in an otherwise normal parturient woman is reassuring in the absence of other clinical evidence. © 2014 S. Karger AG, Basel.

  15. Costs and effects of screening and treating low risk women with a singleton pregnancy for asymptomatic bacteriuria, the ASB study

    Directory of Open Access Journals (Sweden)

    Kazemier Brenda M

    2012-06-01

    Full Text Available Abstract Background The prevalence of asymptomatic bacteriuria (ASB in pregnancy is 2-10% and is associated with both maternal and neonatal adverse outcomes as pyelonephritis and preterm delivery. Antibiotic treatment is reported to decrease these adverse outcomes although the existing evidence is of poor quality. Methods/Design We plan a combined screen and treat study in women with a singleton pregnancy. We will screen women between 16 and 22 weeks of gestation for ASB using the urine dipslide technique. The dipslide is considered positive when colony concentration ≥105 colony forming units (CFU/mL of a single microorganism or two different colonies but one ≥105 CFU/mL is found, or when Group B Streptococcus bacteriuria is found in any colony concentration. Women with a positive dipslide will be randomly allocated to receive nitrofurantoin or placebo 100 mg twice a day for 5 consecutive days (double blind. Primary outcomes of this trial are maternal pyelonephritis and/or preterm delivery before 34 weeks. Secondary outcomes are neonatal and maternal morbidity, neonatal weight, time to delivery, preterm delivery rate before 32 and 37 weeks, days of admission in neonatal intensive care unit, maternal admission days and costs. Discussion This trial will provide evidence for the benefit and cost-effectiveness of dipslide screening for ASB among low risk women at 16–22 weeks of pregnancy and subsequent nitrofurantoin treatment. Trial registration Dutch trial registry: NTR-3068

  16. Properties of convective motions in facular regions

    Science.gov (United States)

    Kostik, R.; Khomenko, E. V.

    2012-09-01

    Aims: We study the properties of solar granulation in a facular region from the photosphere up to the lower chromosphere. Our aim is to investigate the dependence of granular structure on magnetic field strength. Methods: We used observations obtained at the German Vacuum Tower Telescope (Observatorio del Teide, Tenerife) using two different instruments: the Triple Etalon SOlar Spectrometer (TESOS) to measure velocity and intensity variations along the photosphere in the Ba ii 4554 Å line; and, simultaneously, the Tenerife Infrared Polarimeter (TIP-II) to the measure Stokes parameters and the magnetic field strength at the lower photosphere in the Fe i 1.56 μm lines. Results: We find that the convective velocities of granules in the facular area decrease with magnetic field while the convective velocities of intergranular lanes increase with the field strength. Similar to the quiet areas, there is a contrast and velocity sign reversal taking place in the middle photosphere. The reversal heights depend on the magnetic field strength and are, on average, about 100 km higher than in the quiet regions. The correlation between convective velocity and intensity decreases with magnetic field at the bottom photosphere, but increases in the upper photosphere. The contrast of intergranular lanes observed close to the disk center is almost independent of the magnetic field strength. Conclusions: The strong magnetic field of the facular area seems to stabilize the convection and to promote more effective energy transfer in the upper layers of the solar atmosphere, since the convective elements reach greater heights.

  17. Convective transport resistance in the vitreous humor

    Science.gov (United States)

    Penkova, Anita; Sadhal, Satwindar; Ratanakijsuntorn, Komsan; Moats, Rex; Tang, Yang; Hughes, Patrick; Robinson, Michael; Lee, Susan

    2012-11-01

    It has been established by MRI visualization experiments that the convection of nanoparticles and large molecules with high rate of water flow in the vitreous humor will experience resistance, depending on the respective permeabilities of the injected solute. A set of experiments conducted with Gd-DTPA (Magnevist, Bayer AG, Leverkusen, Germany) and 30 nm gadolinium-based particles (Gado CELLTrackTM, Biopal, Worcester, MA) as MRI contrast agents showed that the degree of convective transport in this Darcy-type porous medium varies between the two solutes. These experiments consisted of injecting a mixture of the two (a 30 μl solution of 2% Magnevist and 1% nanoparticles) at the middle of the vitreous of an ex vivo whole bovine eye and subjecting the vitreous to water flow rate of 100 μl/min. The water (0.9% saline solution) was injected at the top of the eye, and was allowed to drain through small slits cut at the bottom of the eyeball. After 50 minutes of pumping, MRI images showed that the water flow carried the Gd-DTPA farther than the nanoparticles, even though the two solutes, being mixed, were subjected to the same convective flow conditions. We find that the convected solute lags the water flow, depending on the solute permeability. The usual convection term needs to be adjusted to allow for the filtration effect on the larger particles in the form (1- σ) u . ∇ c with important implications for the modeling of such systems.

  18. Topology Optimisation for Coupled Convection Problems

    DEFF Research Database (Denmark)

    Alexandersen, Joe

    This thesis deals with topology optimisation for coupled convection problems. The aim is to extend and apply topology optimisation to steady-state conjugate heat transfer problems, where the heat conduction equation governs the heat transfer in a solid and is coupled to thermal transport in a sur......This thesis deals with topology optimisation for coupled convection problems. The aim is to extend and apply topology optimisation to steady-state conjugate heat transfer problems, where the heat conduction equation governs the heat transfer in a solid and is coupled to thermal transport...... in a surrounding uid, governed by a convection-diffusion equation, where the convective velocity field is found from solving the isothermal incompressible steady-state Navier-Stokes equations. Topology optimisation is also applied to steady-state natural convection problems. The modelling is done using stabilised...... finite element formulation is implemented in an object-oriented parallel finite element framework programmed in the C++ programming language, developed by the Top-Opt research group of the Department of Mechanical Engineering at The Technical University of Denmark. The presented work is seen...

  19. A community benchmark for viscoplastic thermal convection in a 2-D square box

    Science.gov (United States)

    Tosi, N.; Stein, C.; Noack, L.; Hüttig, C.; Maierová, P.; Samuel, H.; Davies, D. R.; Wilson, C. R.; Kramer, S. C.; Thieulot, C.; Glerum, A.; Fraters, M.; Spakman, W.; Rozel, A.; Tackley, P. J.

    2015-07-01

    Numerical simulations of thermal convection in the Earth's mantle often employ a pseudoplastic rheology in order to mimic the plate-like behavior of the lithosphere. Yet the benchmark tests available in the literature are largely based on simple linear rheologies in which the viscosity is either assumed to be constant or weakly dependent on temperature. Here we present a suite of simple tests based on nonlinear rheologies featuring temperature, pressure, and strain rate-dependent viscosity. Eleven different codes based on the finite volume, finite element, or spectral methods have been used to run five benchmark cases leading to stagnant lid, mobile lid, and periodic convection in a 2-D square box. For two of these cases, we also show resolution tests from all contributing codes. In addition, we present a bifurcation analysis, describing the transition from a mobile lid regime to a periodic regime, and from a periodic regime to a stagnant lid regime, as a function of the yield stress. At a resolution of around 100 cells or elements in both vertical and horizontal directions, all codes reproduce the required diagnostic quantities with a discrepancy of at most ˜3% in the presence of both linear and nonlinear rheologies. Furthermore, they consistently predict the critical value of the yield stress at which the transition between different regimes occurs. As the most recent mantle convection codes can handle a number of different geometries within a single solution framework, this benchmark will also prove useful when validating viscoplastic thermal convection simulations in such geometries.

  20. Sulfur Earth

    Science.gov (United States)

    de Jong, B. H.

    2007-12-01

    Variations in surface tension affect the buoyancy of objects floating in a liquid. Thus an object floating in water will sink deeper in the presence of dishwater fluid. This is a very minor but measurable effect. It causes for instance ducks to drown in aqueous solutions with added surfactant. The surface tension of liquid iron is very strongly affected by the presence of sulfur which acts as a surfactant in this system varying between 1.9 and 0.4 N/m at 10 mass percent Sulfur (Lee & Morita (2002), This last value is inferred to be the maximum value for Sulfur inferred to be present in the liquid outer core. Venting of Sulfur from the liquid core manifests itself on the Earth surface by the 105 to 106 ton of sulfur vented into the atmosphere annually (Wedepohl, 1984). Inspection of surface Sulfur emission indicates that venting is non-homogeneously distributed over the Earth's surface. The implication of such large variation in surface tension in the liquid outer core are that at locally low Sulfur concentration, the liquid outer core does not wet the predominantly MgSiO3 matrix with which it is in contact. However at a local high in Sulfur, the liquid outer core wets this matrix which in the fluid state has a surface tension of 0.4 N/m (Bansal & Doremus, 1986), couples with it, and causes it to sink. This differential and diapiric movement is transmitted through the essentially brittle mantle (1024 Pa.s, Lambeck & Johnson, 1998; the maximum value for ice being about 1030 Pa.s at 0 K, in all likely hood representing an upper bound of viscosity for all materials) and manifests itself on the surface by the roughly 20 km differentiation, about 0.1 % of the total mantle thickness, between topographical heights and lows with concomitant lateral movement in the crust and upper mantle resulting in thin skin tectonics. The brittle nature of the medium though which this movement is transmitted suggests that the extremes in topography of the D" layer are similar in range to

  1. Comparison of the Mercury and earth magnetospheres - electron measurements and substorm time scales

    International Nuclear Information System (INIS)

    Christon, S.P.

    1987-01-01

    The present search for similarities between earth and Mercury plasma electron distribution and large-scale dynamics notes that both spectral shapes are similar to a kappa-distribution. A model distribution of this type which incorporates convective flow is used to simulate the observed plasma electron spectral variations near the Mariner 10-Mercury 1 A event; convection appears to be stronger before, rather than during, the A event, in contradiction to the Baker (1986) convective injection model for Mercury's two relativistic electron flux enhancements. Mercury's postmidnight energetic electron B and B-prime events seem to be multiple onsets in the course of a substorm. 65 references

  2. Topology of convection beneath the solar surface

    International Nuclear Information System (INIS)

    Stein, R.F.; Nordlund, A.

    1989-01-01

    It is shown that the topology of convection beneath the solar surface is dominated by effects of stratification. Convection in a strongly stratified medium has: (1) gentle expanding structureless warm upflows and (2) strong converging filamentary cool downdrafts. The horizontal flow topology is cellular, with a hierarchy of cell sizes. The small density scale height in the surface layers forces the formation of the solar granulation, which is a shallow surface phenomenon. Deeper layers support successively larger cells. The downflows of small cells close to the surface merge into filamentary downdrafts of larger cells at greater depths, and this process is likely to continue through most of the convection zone. Radiative cooling at the surface provides the entropy-deficient material which drives the circulation. 13 refs

  3. Boundary layer control of rotating convection systems.

    Science.gov (United States)

    King, Eric M; Stellmach, Stephan; Noir, Jerome; Hansen, Ulrich; Aurnou, Jonathan M

    2009-01-15

    Turbulent rotating convection controls many observed features of stars and planets, such as magnetic fields, atmospheric jets and emitted heat flux patterns. It has long been argued that the influence of rotation on turbulent convection dynamics is governed by the ratio of the relevant global-scale forces: the Coriolis force and the buoyancy force. Here, however, we present results from laboratory and numerical experiments which exhibit transitions between rotationally dominated and non-rotating behaviour that are not determined by this global force balance. Instead, the transition is controlled by the relative thicknesses of the thermal (non-rotating) and Ekman (rotating) boundary layers. We formulate a predictive description of the transition between the two regimes on the basis of the competition between these two boundary layers. This transition scaling theory unifies the disparate results of an extensive array of previous experiments, and is broadly applicable to natural convection systems.

  4. Convective mixing in helium white dwarfs

    International Nuclear Information System (INIS)

    Vauclair, G.; Fontaine, G.

    1979-01-01

    The conditions under which convective mixing episodes take place between the helium envelopes and the underlying carbon layers in helium-rich white dwarfs are investigated. It is found that, for essentially any value of the initial helium content less than the maximum mass a helium convection zone can have, mixing does occur, and leads, in the vast majority of cases, to an almost pure carbon superficial composition. Mixing products that show only traces of carbon while retaining helium-dominated envelopes are possible only if the initial helium content is quite close to the maximum possible mass of the helium convection zone. In the presence of turbulence, this restriction could be relaxed, however, and the helium-rich lambda4670 stars may possibly be explained in this fashion

  5. Plate Like Convection with Viscous Strain Weakening and Corresponding Surface Deformation Pattern

    Science.gov (United States)

    Fuchs, L.; Becker, T. W.

    2017-12-01

    How plate tectonic surface motions are generated by mantle convection on Earth and possibly other terrestrial type planets has recently become more readily accessible with fully dynamic convection computations. However, it remains debated how plate-like the behavior in such models truly is, and in particular how the well plate boundary dynamics are captured in models which typically exclude the effects of deformation history and memory. Here, we analyze some of the effects of viscous strain weakening on plate behavior and the interactions between interior convection dynamics and surface deformation patterns. We use the finite element code CitcomCU to model convection in a 3D Cartesian model setup. The models are internally heated, with an Arrhenius-type temperature dependent viscosity including plastic yielding and viscous strain weakening (VSW) and healing (VSWH). VSW can mimic first order features of more complex damage mechanisms such as grain-size dependent rheology. Besides plate diagnostic parameters (Plateness, Mobility, and Toroidal: Poloidal ratio) to analyze the tectonic behavior our models, we also explore how "plate boundaries" link to convective patterns. In a first model series, we analyze general surface deformation patterns without VSW. In the early stages, deformation patterns are clearly co-located with up- and downwelling limbs of convection. Along downwellings strain-rates are high and localized, whereas upwellings tend to lead to broad zones of high deformation. At a more advanced stage, however, the plates' interior is highly deformed due to continuous strain accumulation and resurfaced inherited strain. Including only VSW leads to more localized deformation along downwellings. However, at a more advanced stage plate-like convection fails due an overall weakening of the material. This is prevented including strain healing. Deformation pattern at the surface more closely coincide with the internal convection patterns. The average surface

  6. Solutal convection induced by dissolution. Influence on erosion dynamics and interface shaping.

    Science.gov (United States)

    Berhanu, Michael; Philippi, Julien; Cohen, Caroline; Derr, Julien; Courrech du Pont, Sylvain

    2017-04-01

    dissolution patterns can be related to the characteristic of the convective flow. C. Oltéan, F. Golfier and M.A. Buès, Numerical and experimental investigation of buoyancy-driven dissolution in vertical fracture, J. Geophys. Res. Solid Earth, 118(5), 2038-2048 (2013) C. Cohen, M. Berhanu, J. Derr and S. Courrech du Pont, Erosion patterns on dissolving and melting bodies (2015 Gallery of Fluid motion), Phys. Rev. Fluids, 1, 050508 (2016) T. S. Sullivan, Y. Liu, and R. E. Ecke, Turbulent solutal convection and surface patterning in solid dissolution, Phys. Rev. E 54, 486 (1996)

  7. Where does subduction initiate and die? Insights from global convection models with continental drift

    Science.gov (United States)

    Ulvrova, Martina; Williams, Simon; Coltice, Nicolas; Tackley, Paul

    2017-04-01

    Plate tectonics is a prominent feature on Earth. Together with the underlying convecting mantle, plates form a self-organized system. In order to understand the dynamics of the coupled system, subduction of the lithospheric plates plays the key role since it links the exterior with the interior of the planet. In this work we study subduction initiation and death with respect to the position of the continental rafts. Using thermo-mechanical numerical calculations we investigate global convection models featuring self-consistent plate tectonics and continental drifting employing a pseudo-plastic rheology and testing the effect of a free surface. We consider uncompressible mantle convection in Boussinesq approximation that is basaly and internaly heated. Our calculations indicate that the presence of the continents alterns stress distribution within a certain distance from the margins. Intra-oceanic subudction initiation is favorable during super-continent cycles while the initiation at passive continental margin prevails when continents are dispersed. The location of subduction initiation is additionally controlled by the lithospheric strength. Very weak lithosphere results in domination of intra-oceanic subduction initiation. The subduction zones die more easily in the vicinity of the continent due to the strong rheological contrast between the oceanic and continental lithosphere. In order to compare our findings with subduction positions through time recorded on Earth, we analyse subduction birth in global plate reconstruction back to 410 My.

  8. Convection and magnetic field generation in the interior of planets (August Love Medal Lecture)

    Science.gov (United States)

    Christensen, U. R.

    2009-04-01

    Thermal convection driven by internal energy plays a role of paramount importance in planetary bodies. Its numerical modeling has been an essential tool for understanding how the internal engine of a planet works. Solid state convection in the silicate or icy mantles is the cause of endogenic tectonic activity, volcanism and, in the case of Earth, of plate motion. It also regulates the energy budget of the entire planet, including that of its core, and controls the presence or absence of a dynamo. The complex rheology of solid minerals, effects of phase transitions, and chemical heterogeneity are important issues in mantle convection. Examples discussed here are the convection pattern in Mars and the complex morphology of subducted slabs that are observed by seismic tomography in the Earth's mantle. Internally driven convection in the deep gas envelopes of the giant planets is possibly the cause for the strong jet streams at the surfaces that give rise to their banded appearance. Modeling of the magnetohydrodynamic flow in the conducting liquid core of the Earth has been remarkably successful in reproducing the primary properties of the geomagnetic field. As an examplefor attempts to explain also secondary properties, I will discuss dynamo models that account for the thermal coupling to the mantle. The understanding of the somewhat enigmatic magnetic fields of some other planets is less advanced. Here I will show that dynamos that operate below a stable conducting layer in the upper part of the planetary core can explain the unusual magnetic field properties of Mercury and Saturn. The question what determines the strength of a dynamo-generated magnetic field has been a matter of debate. From a large set of numerical dynamo simulations that cover a fair range of control parameters, we find a rule that relates magnetic field strength to the part of the energy flux that is thermodynamically available to be transformed into other forms of energy. This rules predicts

  9. The driving force for magnetospheric convection

    Science.gov (United States)

    Johnson, F. S.

    1978-01-01

    Viscously driven magnetospheric models, as well as a model involving interconnection between the geomagnetic field and the magnetic field in the solar wind, have been proposed to describe the driving force for magnetospheric convection. Lack of a satisfactory theory for the interconnection in the latter model and, in the case of the viscous interaction models, inadequacies in predicting the quantity of the driving force, make these two classes of models less than successful. Accordingly, a mechanically driven magnetospheric model is proposed: solar wind plasma enters the magnetosphere around the neutral points, covers the inner surface of the magnetopause and subsequently expands, driving convection as it escapes from the open tail.

  10. Basic theory behind parameterizing atmospheric convection

    OpenAIRE

    Plant, R. S.; Fuchs, Z.; Yano, J. I.

    2014-01-01

    Last fall, a network of the European Cooperation in Science and Technology (COST), called “Basic Concepts for Convection Parameterization in Weather Forecast and Climate Models” (COST Action ES0905; see http://w3.cost.esf.org/index.php?id=205&action_number=ES0905), organized a 10-day training course on atmospheric convection and its parameterization. The aim of the workshop, held on the island of Brac, Croatia, was to help young scientists develop an in-depth understanding of the core theory ...

  11. Topology Optimisation for Coupled Convection Problems

    DEFF Research Database (Denmark)

    Alexandersen, Joe; Andreasen, Casper Schousboe; Aage, Niels

    stabilised finite elements implemented in a parallel multiphysics analysis and optimisation framework DFEM [1], developed and maintained in house. Focus is put on control of the temperature field within the solid structure and the problems can therefore be seen as conjugate heat transfer problems, where heat...... conduction governs in the solid parts of the design domain and couples to convection-dominated heat transfer to a surrounding fluid. Both loosely coupled and tightly coupled problems are considered. The loosely coupled problems are convection-diffusion problems, based on an advective velocity field from...

  12. Convection: the likely source of the medium-scale gravity waves observed in the OH airglow layer near Brasilia, Brazil, during the SpreadFEx campaign

    Directory of Open Access Journals (Sweden)

    S. L. Vadas

    2009-01-01

    Full Text Available Six medium-scale gravity waves (GWs with horizontal wavelengths of λH=60–160 km were detected on four nights by Taylor et al. (2009 in the OH airglow layer near Brasilia, at 15° S, 47° W, during the Spread F Experiment (SpreadFEx in Brazil in 2005. We reverse and forward ray trace these GWs to the tropopause and into the thermosphere using a ray trace model which includes thermospheric dissipation. We identify the convective plumes, convective clusters, and convective regions which may have generated these GWs. We find that deep convection is the highly likely source of four of these GWs. We pinpoint the specific deep convective plumes which likely excited two of these GWs on the nights of 30 September and 1 October. On these nights, the source location/time uncertainties were small and deep convection was sporadic near the modeled source locations. We locate the regions containing deep convective plumes and clusters which likely excited the other two GWs. The last 2 GWs were probably also excited from deep convection; however, they must have been ducted ~500–700 km if so. Two of the GWs were likely downwards-propagating initially (after which they reflected upwards from the Earth's surface, while one of the GWs was likely upwards-propagating initially from the convective plume/cluster. We also estimate the amplitudes and vertical scales of these waves at the tropopause, and compare their scales with those from a simple, linear convection model. Finally, we calculate each GW's dissipation altitude, location, and amplitude. We find that the dissipation altitude depends sensitively on the winds at and above the OH layer. We also find that several of these GWs may have penetrated to high enough altitudes to potentially seed equatorial spread F (ESF if located somewhat farther from the magnetic equator.

  13. Effect of frozen/thawed embryo transfer on birthweight, macrosomia, and low birthweight rates in US singleton infants.

    Science.gov (United States)

    Litzky, Julia F; Boulet, Sheree L; Esfandiari, Navid; Zhang, Yujia; Kissin, Dmitry M; Theiler, Regan N; Marsit, Carmen J

    2017-12-29

    Singleton infants conceived using assisted reproductive technology have lower average birthweights than naturally conceived infants and are more likely to be born low birthweight (macrosomia (>4000 g) and low birthweight (macrosomia and low birthweight were evaluated using multivariable predicted marginal proportions from logistic regression models. In total, 180,184 singleton, term infants were included, with 55,898 (31.02%) having been conceived from frozen/thawed embryos. Frozen/thawed embryo transfer was associated with, on average, a 142 g increase in birthweight compared with infants born after fresh embryo transfer (P macrosomia following frozen/thawed embryo transfer was greater than that following fresh embryo transfer, but the risk of low birthweight among frozen/thawed embryo transfer infants was significantly decreased in comparison with fresh embryo transfer infants. Copyright © 2018 Elsevier Inc. All rights reserved.

  14. Use of multiple linear regression and logistic regression models to investigate changes in birthweight for term singleton infants in Scotland.

    Science.gov (United States)

    Bonellie, Sandra R

    2012-10-01

    To illustrate the use of regression and logistic regression models to investigate changes over time in size of babies particularly in relation to social deprivation, age of the mother and smoking. Mean birthweight has been found to be increasing in many countries in recent years, but there are still a group of babies who are born with low birthweights. Population-based retrospective cohort study. Multiple linear regression and logistic regression models are used to analyse data on term 'singleton births' from Scottish hospitals between 1994-2003. Mothers who smoke are shown to give birth to lighter babies on average, a difference of approximately 0.57 Standard deviations lower (95% confidence interval. 0.55-0.58) when adjusted for sex and parity. These mothers are also more likely to have babies that are low birthweight (odds ratio 3.46, 95% confidence interval 3.30-3.63) compared with non-smokers. Low birthweight is 30% more likely where the mother lives in the most deprived areas compared with the least deprived, (odds ratio 1.30, 95% confidence interval 1.21-1.40). Smoking during pregnancy is shown to have a detrimental effect on the size of infants at birth. This effect explains some, though not all, of the observed socioeconomic birthweight. It also explains much of the observed birthweight differences by the age of the mother.   Identifying mothers at greater risk of having a low birthweight baby as important implications for the care and advice this group receives. © 2012 Blackwell Publishing Ltd.

  15. The impact of gestational diabetes mellitus on postpartum urinary incontinence: a longitudinal cohort study on singleton pregnancies.

    Science.gov (United States)

    Chuang, C-M; Lin, I-F; Horng, H-C; Hsiao, Y-H; Shyu, I-L; Chou, P

    2012-10-01

    To determine whether gestational diabetes mellitus (GDM) is an independent risk factor for postpartum urinary incontinence in singleton pregnancies. A longitudinal cohort study. A single tertiary-care hospital in Taiwan. Pregnant women with term deliveries between 2002 and 2007 (n = 6653) were consecutively recruited. Logistic regression models were fitted based on generalised estimating equation methods to derive odds ratios for occurrences of type-specific urinary incontinence in the third trimester and at four time-points over 2 years during the postpartum period. Evaluation of whether GDM is an independent risk factor for postpartum urinary incontinence. The full model analysis revealed that GDM was an independent risk factor for all type-specific urinary incontinence (odds ratio [95% confidence interval]: 1.97 [1.56-2.51], 3.11 [2.18-4.43] and 2.73 [1.70-4.40] for stress, urge and mixed incontinence, respectively]. Compared with women without GDM, women with GDM tended to exhibit more severe symptoms of stress incontinence for up to 2 years postpartum, whereas for urge or mixed incontinence, more severe symptoms were found only for 6 months postpartum. Evaluation of quality of life using the Incontinence Impact Questionnaire 7 suggested that women with GDM requiring insulin treatment had a higher likelihood of functional impairment than women with GDM requiring conservative treatment only or women without GDM (P risk factor for postpartum urinary incontinence and had a significant impact on quality of life. Women with GDM should be provided with timely consultation and support once urinary incontinence occurs. © 2012 The Authors BJOG An International Journal of Obstetrics and Gynaecology © 2012 RCOG.

  16. Fear of childbirth predicts postpartum depression: a population-based analysis of 511 422 singleton births in Finland.

    Science.gov (United States)

    Räisänen, Sari; Lehto, Soili M; Nielsen, Henriette Svarre; Gissler, Mika; Kramer, Michael R; Heinonen, Seppo

    2013-11-28

    To study how reproductive risks and perinatal outcomes are associated with postpartum depression treated in specialised healthcare defined according to the International Classification of Diseases (ICD)-10 codes, separately among women with and without a history of depression. A retrospective population-based case-control study. Data gathered from three national health registers for the years 2002-2010. All singleton births (n=511 422) in Finland. Prevalence of postpartum depression and the risk factors associated with it. In total, 0.3% (1438 of 511 422) of women experienced postpartum depression, the prevalence being 0.1% (431 of 511 422) in women without and 5.3% (1007 of 18 888) in women with a history of depression. After adjustment for possible covariates, a history of depression was found to be the strongest risk factor for postpartum depression. Other strong predisposing factors for postpartum depression were fear of childbirth, caesarean birth, nulliparity and major congenital anomaly. Specifically, among the 30% of women with postpartum depression but without a history of depression, postpartum depression was shown to be associated with fear of childbirth (adjusted OR (aOR 2.71, 95% CI 1.98 to 3.71), caesarean birth (aOR 1.38, 95% CI 1.08 to 1.77), preterm birth (aOR 1.65, 95% CI 1.08 to 2.56) and major congenital anomaly (aOR 1.67, 95% CI 1.15 to 2.42), compared with women with no postpartum depression and no history of depression. A history of depression was found to be the most important predisposing factor of postpartum depression. Women without previous episodes of depression were at an increased risk of postpartum depression if adverse events occurred during the course of pregnancy, especially if they showed physician-diagnosed fear of childbirth.

  17. Singleton Sequence Type 382, an Emerging Clonal Group of Listeria monocytogenes Associated with Three Multistate Outbreaks Linked to Contaminated Stone Fruit, Caramel Apples, and Leafy Green Salad

    OpenAIRE

    Chen, Yi; Luo, Yan; Pettengill, James; Timme, Ruth; Melka, David; Doyle, Matthew; Jackson, Alikeh; Parish, Mickey; Hammack, Thomas S.; Allard, Marc W.; Brown, Eric W.; Strain, Errol A.

    2017-01-01

    ABSTRACT Three multistate outbreaks between 2014 and 2016, involving case patients in and outside the United States, were linked to stone fruit, caramel apples, and packaged leafy green salad contaminated with Listeria monocytogenes singleton sequence type 382 (ST382), a serotype IVb-v1 clone with limited genomic divergence. Isolates from these outbreaks and other ST382 isolates not associated with these outbreaks were analyzed by whole-genome sequencing (WGS) analysis. The primary difference...

  18. Periconceptional undernutrition programs changes in insulin-signaling molecules and microRNAs in skeletal muscle in singleton and twin fetal sheep.

    Science.gov (United States)

    Lie, Shervi; Morrison, Janna L; Williams-Wyss, Olivia; Suter, Catherine M; Humphreys, David T; Ozanne, Susan E; Zhang, Song; Maclaughlin, Severence M; Kleemann, David O; Walker, Simon K; Roberts, Claire T; McMillen, I Caroline

    2014-01-01

    Maternal undernutrition around the time of conception is associated with an increased risk of insulin resistance in adulthood. We determined the effect of maternal undernutrition in the periconceptional period (PCUN, i.e., 60 days prior to 6 days after conception) and the preimplantation period (PIUN, i.e., 0-6 days after conception) on mRNA expression and protein abundance of key insulin-signaling molecules as well as the global microRNA expression in quadriceps muscle of singleton and twin fetal sheep in late gestation. In singleton fetuses, exposure to PCUN resulted in lower protein abundance of PIK3CB (P < 0.01), PRKCZ (P < 0.05), and pPRKCZ (Thr410) (P < 0.05) in skeletal muscle compared to controls. In PIUN singletons, there was a higher protein abundance of IRS1 (P < 0.05), PDPK1 (P < 0.05), and SLC2A4 (P < 0.05) compared to controls. In twins, PCUN resulted in higher protein abundance of IRS1 (P < 0.05), AKT2 (P < 0.05), PDPK1 (P < 0.05), and PRKCZ (P < 0.001), while PIUN also resulted in higher protein abundance of IRS1 (P < 0.05), PRKCZ (P < 0.001), and SLC2A4 (P < 0.05) in fetal muscle compared to controls. There were specific patterns of the types and direction of changes in the expression of 22 microRNAs in skeletal muscle after exposure to PCUN or PIUN and clear differences in these patterns between singleton and twin pregnancies. These findings provide evidence that maternal undernutrition around the time of conception induces changes in the expression of microRNAs, which may play a role in altering the abundance of the key insulin-signaling molecules in skeletal muscle and in the association between PCUN undernutrition and insulin resistance in adult life.

  19. Biodigester Feasibility and Design for Space & Earth

    Science.gov (United States)

    Shutts, Stacy; Ewert, Mike; Bacon, Jack

    2016-01-01

    Anaerobic digestion converts organic waste into methane gas and fertilizer effluent. The ICA-developed prototype system is designed for planetary surface operation. It uses passive hydrostatic control for reliability, and is modular and redundant. The serpentine configuration accommodates tight geometric constraints similar to the ISS ECLSS rack architectures. Its shallow, low-tilt design enables (variable) lower-g convection than standard Earth (1 g) digesters. This technology will reuse and recycle materials including human waste, excess food, as well as packaging (if biodegradable bags are used).

  20. High Ra, high Pr convection with viscosity gradients

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. High Ra, high Pr convection with viscosity gradients. Weak upward flow through mesh. Top fluid more viscous. Unstable layer Instability Convection.

  1. Annual review of earth and planetary sciences. Volume 16

    Science.gov (United States)

    Wetherill, George W.; Albee, Arden L.; Stehli, Francis G.

    Various papers on earth and planetary science topics are presented. The subjects addressed include: role and status of earth science field work; phase relations of prealuminous granitic rocks and their petrogenetic implications; chondritic meteorites and the solar nebula; volcanic winters; mass wasting on continental margins; earthquake ground motions; ore deposits as guides to geologic history of the earth; geology of high-level nuclear waste disposal; and tectonic evolution of the Caribbean. Also discussed are: the earth's rotation; the geophysics of a restless caldera (Long Valley, California); observations of cometary nuclei; geology of Venus; seismic stratigraphy; in situ-produced cosmogenic isotopes in terrestrial rocks; time variations of the earth's magnetic field; deep slabs, geochemical heterogeneity, and the large-scale structure of mantle convection; early proterozoic assembly and growth of Laurentia; concepts and methods of high-resolution event stratigraphy.

  2. Inferring convective responses to El Niño with atmospheric electricity measurements at Shetland

    International Nuclear Information System (INIS)

    Harrison, R G; Pascoe, K; Joshi, M

    2011-01-01

    Pacific ocean temperature anomalies associated with the El Niño–Southern Oscillation (ENSO) modulate atmospheric convection and hence thunderstorm electrification. The generated current flows globally via the atmospheric electric circuit, which can be monitored anywhere on Earth. Atmospheric electricity measurements made at Shetland (in Scotland) display a mean global circuit response to ENSO that is characterized by strengthening during ‘El Niño’ conditions, and weakening during ‘La Niña’ conditions. Examining the hourly varying response indicates that a potential gradient (PG) increase around noon UT is likely to be associated with a change in atmospheric convection and resultant lightning activity over equatorial Africa and Eastern Asia. A secondary increase in PG just after midnight UT can be attributed to more shower clouds in the central Pacific ocean during an ‘El Niño’.

  3. Role of deep cloud convection in the ozone budget of the troposphere.

    Science.gov (United States)

    Lelieveld, J; Crutzen, P J

    1994-06-17

    Convective updrafts in thunderstorms prolong the lifetime of ozone (O(3)) and its anthropogenic precursor NOx [nitric oxide (NO) + nitrogen dioxide (NO(2))] by carrying these gases rapidly upward from the boundary layer into a regime where the O(3) production efficiency is higher, chemical destruction is slower, and surface deposition is absent. On the other hand, the upper troposphere is relatively rich in O(3) and NOx from natural sources such as downward transport from the stratosphere and lightning; convective overturning conveys the O(3) and NOx toward the Earth's surface where these components are more efficiently removed from the atmosphere. Simulations with a three-dimensional global model suggest that the net result of these counteractive processes is a 20 percent overall reduction in total tropospheric O(3). However, the net atmospheric oxidation efficiency is enhanced by 10 to 20 percent.

  4. Effects of convective ice evaporation on interannual variability of tropical tropopause layer water vapor

    Science.gov (United States)

    Ye, Hao; Dessler, Andrew E.; Yu, Wandi

    2018-04-01

    Water vapor interannual variability in the tropical tropopause layer (TTL) is investigated using satellite observations and model simulations. We break down the influences of the Brewer-Dobson circulation (BDC), the quasi-biennial oscillation (QBO), and the tropospheric temperature (ΔT) on TTL water vapor as a function of latitude and longitude using a two-dimensional multivariate linear regression. This allows us to examine the spatial distribution of the impact of each process on TTL water vapor. In agreement with expectations, we find that the impacts from the BDC and QBO act on TTL water vapor by changing TTL temperature. For ΔT, we find that TTL temperatures alone cannot explain the influence. We hypothesize a moistening role for the evaporation of convective ice from increased deep convection as the troposphere warms. Tests using a chemistry-climate model, the Goddard Earth Observing System Chemistry Climate Model (GEOSCCM), support this hypothesis.

  5. Thermal convection driven by acoustic field under microgravity

    OpenAIRE

    Tanabe, Mitsuaki; 田辺 光昭

    2007-01-01

    Natural convection is suppressed in space environment due to the weightlessness. Only centrifugal force is utilized currently to drive gas-phase thermal convection in space. This paper presents an alternative way to drive thermal convection. From the investigation of combustion oscillation in rocket motors, a new thermal convection had been found in stationary acoustic fields. Analyzing the phenomena, acoustic radiation force is found to be the candidate driving force. With a simplified syste...

  6. Natural convection flow between moving boundaries | Chepkwony ...

    African Journals Online (AJOL)

    The laminar steady natural convection flow of viscous, incompressible fluid between two moving vertical plates is considered. It is assumed that the plates are moving in opposite direction with equal velocity. The two-point boundary value problem governing the flow is characterized by a non-dimensional parameter K. It is ...

  7. Oscillatory Convection in Rotating Liquid Metals

    Science.gov (United States)

    Bertin, Vincent; Grannan, Alex; Aurnou, Jonathan

    2016-11-01

    We have performed laboratory experiments in a aspect ratio Γ = 2 cylinder using liquid gallium (Pr = 0 . 023) as the working fluid. The Ekman number varies from E = 4 ×10-5 to 4 ×10-6 and the Rayleigh number varies from Ra = 3 ×105 to 2 ×107 . Using heat transfer and temperature measurements within the fluid, we characterize the different styles of low Pr rotating convective flow. The convection threshold is first overcome in the form of a container scale inertial oscillatory mode. At stronger forcing, wall-localized modes develop, coexisting with the inertial oscillatory modes in the bulk. When the strength of the buoyancy increases further, the bulk flow becomes turbulent while the wall modes remain. Our results imply that rotating convective flows in liquid metals do not develop in the form of quasi-steady columns, as in Pr = 1 planetary and stellar dynamo models, but in the form of oscillatory motions. Therefore, convection driven dynamo action in low Pr fluids can differ substantively than that occurring in typical Pr = 1 numerical models. Our results also suggest that low wavenumber, wall modes may be dynamically and observationally important in liquid metal dynamo systems. We thank the NSF Geophysics Program for support of this project.

  8. An Observational Investigation of Penetrative Convection

    DEFF Research Database (Denmark)

    Jensen, Niels Otto; Lenschow, D. H.

    1978-01-01

    Data taken during the Air Mass Transformation Experiment (AMTEX) by the NCAR Electra aircraft have proven useful for investigating the structure of thermals penetrating into the turbulent inversion layer which caps the convective mixed layer. Variances, covariances, spectra and cospectra of poten...

  9. Salinity transfer in bounded double diffusive convection

    NARCIS (Netherlands)

    Yang, Yantao; van der Poel, Erwin; Ostilla Monico, Rodolfo; Sun, Chao; Verzicco, Roberto; Grossmann, Siegfried; Lohse, Detlef

    2015-01-01

    The double diffusive convection between two parallel plates is numerically studied for a series of parameters. The flow is driven by the salinity difference and stabilised by the thermal field. Our simulations are directly compared with experiments by Hage & Tilgner (Phys. Fluids, vol. 22, 2010,

  10. Mixed convection in a baffled grooved channel

    Indian Academy of Sciences (India)

    A remarkable enhancement of heat transfer is observed in presence of baffle. The study has also pointed out that for optimal performance, the position and height of the baffle need to be adjusted depending on the direction of external flow. Keywords. Heat transfer; grooved channel; mixed convection; Richardson number;.

  11. Radiative-convective equilibrium model intercomparison project

    Science.gov (United States)

    Wing, Allison A.; Reed, Kevin A.; Satoh, Masaki; Stevens, Bjorn; Bony, Sandrine; Ohno, Tomoki

    2018-03-01

    RCEMIP, an intercomparison of multiple types of models configured in radiative-convective equilibrium (RCE), is proposed. RCE is an idealization of the climate system in which there is a balance between radiative cooling of the atmosphere and heating by convection. The scientific objectives of RCEMIP are three-fold. First, clouds and climate sensitivity will be investigated in the RCE setting. This includes determining how cloud fraction changes with warming and the role of self-aggregation of convection in climate sensitivity. Second, RCEMIP will quantify the dependence of the degree of convective aggregation and tropical circulation regimes on temperature. Finally, by providing a common baseline, RCEMIP will allow the robustness of the RCE state across the spectrum of models to be assessed, which is essential for interpreting the results found regarding clouds, climate sensitivity, and aggregation, and more generally, determining which features of tropical climate a RCE framework is useful for. A novel aspect and major advantage of RCEMIP is the accessibility of the RCE framework to a variety of models, including cloud-resolving models, general circulation models, global cloud-resolving models, single-column models, and large-eddy simulation models.

  12. Free convection film flows and heat transfer

    CERN Document Server

    Shang, Deyi

    2010-01-01

    Presents development of systematic studies for hydrodynamics and heat and mass transfer in laminar free convection, accelerating film boiling and condensation of Newtonian fluids, and accelerating film flow of non-Newtonian power-law fluids. This book provides a system of analysis models with a developed velocity component method.

  13. MARANGONI CONVECTION IN V-SHAPED CONTAINERS

    NARCIS (Netherlands)

    HOOGSTRATEN, HW; HOEFSLOOT, HCJ; JANSSEN, LPBM

    This paper presents a numerical study of the time evolution of Marangoni convection in two V-shaped containers involved in the microgravity experiments reported in Hoefsloot et al.[7]. First the case of the triangular container with a plane gas/liquid interface is considered, next the container

  14. Terminal project heat convection in thin cylinders

    International Nuclear Information System (INIS)

    Morales Corona, J.

    1992-01-01

    Heat convection in thin cylinders and analysis about natural convection for straight vertical plates, and straight vertical cylinders submersed in a fluid are presented some works carry out by different authors in the field of heat transfer. In the part of conduction, deduction of the equation of heat conduction in cylindrical coordinates by means of energy balance in a control volume is presented. Enthalpy and internal energy are used for the outlining of the equation and finally the equation in its vectorial form is obtained. In the convection part development to calculate the Nusselt number for a straight vertical plate by a forces analysis, an energy balance and mass conservation over a control volume is outlined. Several empiric correlations to calculate the Nusselt number and its relations with other dimensionless numbers are presented. In the experimental part the way in which a prototype rode is assembled is presented measurements of temperatures attained in steady state and in free convection for working fluids as air and water are showed in tables. Also graphs of Nusselt numbers obtained in the experimental way through some empiric correlations are showed (Author)

  15. Turbulent Convection and Pulsation Stability of Stars

    Science.gov (United States)

    Xiong, Da-run

    2017-10-01

    The controversies about the excitation mechanism for low-temperature variables are reviewed: (1) Most people believe that γ Doradus variables are excited by the so-called convective blocking mechanism. Our researches show that the excitation of γ Doradus has no substantial difference from that of δ Scuti. They are two subgroups of a broader type of δ Stuti-γ Doradus stars: δ Scuti is the p-mode subgroup, while γ Doradus is the g-mode subgroup. (2) Most people believe that the solar and stellar solar-like oscillations are damped by convection, and they are driven by the so-called turbulent random excitation mechanism. Our researches show that convection is not solely a damping mechanism for stellar oscillations, otherwise it is unable to explain the Mira and Mira-like variables. By using our non-local and time-dependent theory of convection, we can reproduce not only the pulsationally unstable strip of δ Scuti and γ Doradus variables, but also the solar-like oscillation features of low-luminosity red giants and the Mira-like oscillation features of high-luminosity red giants.

  16. Theories for convection in stellar atmospheres

    International Nuclear Information System (INIS)

    Nordlund, Aa.

    1976-02-01

    A discussion of the fundamental differences between laboratory convection in a stellar atmosphere is presented. The shortcomings of laterally homogeneous model atmospheres are analysed, and the extent to which these shortcoming are avoided in the two-component representation is discussed. Finally a qualitative discussion on the scaling properties of stellar granulation is presented. (Auth.)

  17. Natural convection in horizontal fluid layers

    International Nuclear Information System (INIS)

    Suo-Antilla, A.J.

    1977-02-01

    The experimental work includes developing and using a thermal convection cell to obtain measurements of the heat flux and turbulent core temperature of a horizontal layer of fluid heated internally and subject to both stabilizing and destabilizing temperature differences. The ranges of Rayleigh numbers tested were 10 7 equal to or less than R/sub I/ equal to or less than 10 13 and -10 10 equal to or less than R/sub E/ equal to or less than 10 10 . Power integral methods were found to be adequate for interpolating and extrapolating the data. The theoretical work consists of the derivation, solution and use of the mean field equations for study of thermally driven convection in horizontal layers of infinite extent. The equations were derived by a separation of variables technique where the horizontal directions were described by periodic structures and the vertical being some function of z. The derivation resulted in a coupled set of momentum and energy equations. The equations were simplified by using the infinite Prandtl number limit and neglecting direct intermodal interaction. Solutions to these equations are used to predict the existence of multi-wavenumber flows at all supercritical Rayleigh numbers. Subsequent inspection of existing experimental photographs of convecting fluids confirms their existence. The onset of time dependence is found to coincide with the onset of the second convective mode. Each mode is found to consist of two wavenumbers and typically the velocity and temperature fields of the right modal branch are found to be out of phase

  18. Vortex convection in nonuniform compressible flow

    Science.gov (United States)

    Szumowski, A. P.; Meier, G. E. A.

    1988-03-01

    Vortex convection in longitudinally nonuniform transonic flow fields was studied. Vortices moving in moderately accelerated flow are distinct in the subsonic and supersonic range. Due to the acceleration, the vortices of the Karman street separate continuously one from another. They form a series of periodically shedding individual vortices. The density distribution of the accelerated vortices stays circular. Vortices in subsonic stream (behind the shock wave in the divergent part of the Laval nozzle) impinging on an obstacle (in this case on the regulating valve) cause shock fronts which move upstream. In a subsonic stream flowing out from the convergent nozzle, the primary vortices inside the stream significantly perturb its boundaries and induce secondary vortices (at the boundaries). Flow patterns in a duct with a sudden enlargement of cross section are influenced by the vortices convected in the flow too. However, the observed perturbations of these patterns are relatively weak. The unsteady behaviour of the free stream is not only the effect of the vortex convection but also of the unsteady interactions with the boundaries, i.e., the adjusting valve and the test-section walls. However, the effect of the vortex convection is the stronger.

  19. Presentation on Tropical Mesoscale convective Systems and ...

    Indian Academy of Sciences (India)

    IAS Admin

    Microphysics of deep convection. Fountain. (Water Vapor). Intrusion. (Ozone). Circulation. Mass and Energy. Budget. Thermal, Radiation and. Chemistry. Hydrological Cycle. Global ... 厂 Represented as time of overpass. 厂 Shallow: Short lived ... NEW Definition of WET & DRY Spell Introduced. Wind Shear. Temperature ...

  20. Crystal-Growing Crucible To Suppress Convection

    Science.gov (United States)

    Richter, R.

    1986-01-01

    Platform under growth region stabilizes melt for more uniform crystal growth. In new crucible, platform just below growth interface so melt is too shallow to support convection. Critical depth for onset of pertinent instability calculated from heat flux through surface of melt, volume coefficient of thermal expansion, thermal conductivity, thermal diffusivity, and kinematic viscosity.

  1. Natural convection inside an irregular porous cavity

    International Nuclear Information System (INIS)

    Beltran, Jorge I. LLagostera; Trevisan, Osvair Vidal

    1990-01-01

    Natural convection flow induced by heating from below in a irregular porous cavity is investigated numerically. The influence of the modified Rayleigh number and geometric ratios on heat transfer and fluid flow is studied. Global and local Nusselt for Rayleigh numbers covering the range 0 - 1600 and for several geometric ratios. The fluid flow and the temperature field are illustrated by contour maps. (author)

  2. Determination of the convective heat transfer coefficient

    NARCIS (Netherlands)

    Spierings, D.; Bosman, F.; Peters, T.; Plasschaert, F.

    The value of the convective heat transfer coefficient (htc) is determined under different loading conditions by using a computer aided method. The thermal load has been applied mathematically as well as experimentally to the coronal surface of an axisymmetric tooth model. To verify the assumptions

  3. Influence of convective conditions on three dimensional mixed convective hydromagnetic boundary layer flow of Casson nanofluid

    Energy Technology Data Exchange (ETDEWEB)

    Rauf, A., E-mail: raufamar@ciitsahiwal.edu.pk [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Siddiq, M.K. [Centre for Advanced Studies in Pure and Applied Mathematics, Department of Mathematics, Bahauddin Zakariya University, Multan 63000 (Pakistan); Abbasi, F.M. [Department of Mathematics, Comsats Institute of Information Technology, Islamabad 44000 (Pakistan); Meraj, M.A. [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan); Ashraf, M. [Centre for Advanced Studies in Pure and Applied Mathematics, Department of Mathematics, Bahauddin Zakariya University, Multan 63000 (Pakistan); Shehzad, S.A. [Department of Mathematics, Comsats Institute of Information Technology, Sahiwal 57000 (Pakistan)

    2016-10-15

    The present work deals with the steady laminar three-dimensional mixed convective magnetohydrodynamic (MHD) boundary layer flow of Casson nanofluid over a bidirectional stretching surface. A uniform magnetic field is applied normal to the flow direction. Similarity variables are implemented to convert the non-linear partial differential equations into ordinary ones. Convective boundary conditions are utilized at surface of the sheet. A numerical technique of Runge–Kutta–Fehlberg (RFK45) is used to obtain the results of velocity, temperature and concentration fields. The physical dimensionless parameters are discussed through tables and graphs. - Highlights: • Mixed convective boundary layer flow of Casson nanofluid is taken into account. • Impact of magnetic field is examined. • Convective heat and mass conditions are imposed. • Numerical solutions are presented and discussed.

  4. Testing particle filters on convective scale dynamics

    Science.gov (United States)

    Haslehner, Mylene; Craig, George. C.; Janjic, Tijana

    2014-05-01

    Particle filters have been developed in recent years to deal with highly nonlinear dynamics and non Gaussian error statistics that also characterize data assimilation on convective scales. In this work we explore the use of the efficient particle filter (P.v. Leeuwen, 2011) for convective scale data assimilation application. The method is tested in idealized setting, on two stochastic models. The models were designed to reproduce some of the properties of convection, for example the rapid development and decay of convective clouds. The first model is a simple one-dimensional, discrete state birth-death model of clouds (Craig and Würsch, 2012). For this model, the efficient particle filter that includes nudging the variables shows significant improvement compared to Ensemble Kalman Filter and Sequential Importance Resampling (SIR) particle filter. The success of the combination of nudging and resampling, measured as RMS error with respect to the 'true state', is proportional to the nudging intensity. Significantly, even a very weak nudging intensity brings notable improvement over SIR. The second model is a modified version of a stochastic shallow water model (Würsch and Craig 2013), which contains more realistic dynamical characteristics of convective scale phenomena. Using the efficient particle filter and different combination of observations of the three field variables (wind, water 'height' and rain) allows the particle filter to be evaluated in comparison to a regime where only nudging is used. Sensitivity to the properties of the model error covariance is also considered. Finally, criteria are identified under which the efficient particle filter outperforms nudging alone. References: Craig, G. C. and M. Würsch, 2012: The impact of localization and observation averaging for convective-scale data assimilation in a simple stochastic model. Q. J. R. Meteorol. Soc.,139, 515-523. Van Leeuwen, P. J., 2011: Efficient non-linear data assimilation in geophysical

  5. International symposium on transient convective heat transfer: book of abstracts

    International Nuclear Information System (INIS)

    1996-01-01

    The international symposium on convective heat transfer was held on 19-23 August 1996, in Cesme, Izmir, Turkey. The spesialists discussed forced convection, heat exchangers, free convection and multiphase media and phase change at the meeting. Almost 53 papers were presented in the meeting

  6. Probing the transition from shallow to deep convection

    Energy Technology Data Exchange (ETDEWEB)

    Kuang, Zhiming [Harvard Univ., Cambridge, MA (United States); Gentine, Pierre [Columbia Univ., New York, NY (United States)

    2016-05-01

    In this funded project we highlighted the components necessary for the transition from shallow to deep convection. In particular we defined a prototype of shallow to deep convection, which is currently being implemented in the NASA GISS model. We also tried to highlight differences between land and oceanic convection.

  7. Anomalously weak Labrador Sea convection and Atlantic overturning during the past 150 years.

    Science.gov (United States)

    Thornalley, David J R; Oppo, Delia W; Ortega, Pablo; Robson, Jon I; Brierley, Chris M; Davis, Renee; Hall, Ian R; Moffa-Sanchez, Paola; Rose, Neil L; Spooner, Peter T; Yashayaev, Igor; Keigwin, Lloyd D

    2018-04-01

    The Atlantic meridional overturning circulation (AMOC) is a system of ocean currents that has an essential role in Earth's climate, redistributing heat and influencing the carbon cycle 1, 2 . The AMOC has been shown to be weakening in recent years 1 ; this decline may reflect decadal-scale variability in convection in the Labrador Sea, but short observational datasets preclude a longer-term perspective on the modern state and variability of Labrador Sea convection and the AMOC 1, 3-5 . Here we provide several lines of palaeo-oceanographic evidence that Labrador Sea deep convection and the AMOC have been anomalously weak over the past 150 years or so (since the end of the Little Ice Age, LIA, approximately AD 1850) compared with the preceding 1,500 years. Our palaeoclimate reconstructions indicate that the transition occurred either as a predominantly abrupt shift towards the end of the LIA, or as a more gradual, continued decline over the past 150 years; this ambiguity probably arises from non-AMOC influences on the various proxies or from the different sensitivities of these proxies to individual components of the AMOC. We suggest that enhanced freshwater fluxes from the Arctic and Nordic seas towards the end of the LIA-sourced from melting glaciers and thickened sea ice that developed earlier in the LIA-weakened Labrador Sea convection and the AMOC. The lack of a subsequent recovery may have resulted from hysteresis or from twentieth-century melting of the Greenland Ice Sheet 6 . Our results suggest that recent decadal variability in Labrador Sea convection and the AMOC has occurred during an atypical, weak background state. Future work should aim to constrain the roles of internal climate variability and early anthropogenic forcing in the AMOC weakening described here.

  8. Sensitivity of Tropical Cyclones to Parameterized Convection in the NASA GEOS5 Model

    Science.gov (United States)

    Lim, Young-Kwon; Schubert, Siegfried D.; Reale, Oreste; Lee, Myong-In; Molod, Andrea M.; Suarez, Max J.

    2014-01-01

    The sensitivity of tropical cyclones (TCs) to changes in parameterized convection is investigated to improve the simulation of TCs in the North Atlantic. Specifically, the impact of reducing the influence of the Relaxed Arakawa-Schubert (RAS) scheme-based parameterized convection is explored using the Goddard Earth Observing System version5 (GEOS5) model at 0.25 horizontal resolution. The years 2005 and 2006 characterized by very active and inactive hurricane seasons, respectively, are selected for simulation. A reduction in parameterized deep convection results in an increase in TC activity (e.g., TC number and longer life cycle) to more realistic levels compared to the baseline control configuration. The vertical and horizontal structure of the strongest simulated hurricane shows the maximum lower-level (850-950hPa) wind speed greater than 60 ms and the minimum sea level pressure reaching 940mb, corresponding to a category 4 hurricane - a category never achieved by the control configuration. The radius of the maximum wind of 50km, the location of the warm core exceeding 10 C, and the horizontal compactness of the hurricane center are all quite realistic without any negatively affecting the atmospheric mean state. This study reveals that an increase in the threshold of minimum entrainment suppresses parameterized deep convection by entraining more dry air into the typical plume. This leads to cooling and drying at the mid- to upper-troposphere, along with the positive latent heat flux and moistening in the lower-troposphere. The resulting increase in conditional instability provides an environment that is more conducive to TC vortex development and upward moisture flux convergence by dynamically resolved moist convection, thereby increasing TC activity.

  9. Identification of dominant flow structures in rapidly rotating convection of liquid metals using Dynamic Mode Decomposition

    Science.gov (United States)

    Horn, S.; Schmid, P. J.; Aurnou, J. M.

    2016-12-01

    The Earth's metal core acts as a dynamo whose efficiency in generating and maintaining the magnetic field is essentially determined by the rotation rate and the convective motions occurring in its outer liquid part. For the description of the primary physics in the outer core the idealized system of rotating Rayleigh-Bénard convection is often invoked, with the majority of studies considering only working fluids with Prandtl numbers of Pr ≳ 1. However, liquid metals are characterized by distinctly smaller Prandtl numbers which in turn result in an inherently different type of convection. Here, we will present results from direct numerical simulations of rapidly rotating convection in a fluid with Pr ≈ 0.025 in cylindrical containers and Ekman numbers as low as 5 × 10-6. In this system, the Coriolis force is the source of two types of inertial modes, the so-called wall modes, that also exist at moderate Prandtl numbers, and cylinder-filling oscillatory modes, that are a unique feature of small Prandtl number convection. The obtained flow fields were analyzed using the Dynamic Mode Decomposition (DMD). This technique allows to extract and identify the structures that govern the dynamics of the system as well as their corresponding frequencies. We have investigated both the regime where the flow is purely oscillatory and the regime where wall modes and oscillatory modes co-exist. In the purely oscillatory regime, high and low frequency oscillatory modes characterize the flow. When both types of modes are present, the DMD reveals that the wall-attached modes dominate the flow dynamics. They precess with a relatively low frequency in retrograde direction. Nonetheless, also in this case, high frequency oscillations have a significant contribution.

  10. A test of sensitivity to convective transport in a global atmospheric CO{sub 2} simulation

    Energy Technology Data Exchange (ETDEWEB)

    Bian, H. [NASA Goddard Space Flight Center, Greenbelt, MD (United States). UMBC Goddard Earth Science and Technology Center; Kawa, S.R.; Chin, M.; Pawson, S.; Zhu, Z. [NASA Goddard Space Flight Center, Greenbelt, MD (United States); Rasch, P. [National Center for Atmospheric Research, Boulder, CO (United States); Wu, S. [Harvard Univ., Cambridge, MA (United States)

    2006-11-15

    Two approximations to convective transport have been implemented in an offline chemistry transport model (CTM) to explore the impact on calculated atmospheric CO{sub 2} distributions. Global CO{sub 2} in the year 2000 is simulated using the CTM driven by assimilated meteorological fields from the NASA's Goddard Earth Observation System Data Assimilation System, Version 4 (GEOS-4). The model simulates atmospheric CO{sub 2} by adopting the same CO{sub 2} emission inventory and dynamical modules as described in Kawa et al. (convective transport scheme denoted as Conv1). Conv1 approximates the convective transport by using the bulk convective mass fluxes to redistribute trace gases. The alternate approximation, Conv2, partitions fluxes into updraft and downdraft, as well as into entrainment and detrainment, and has potential to yield a more realistic simulation of vertical redistribution through deep convection.Replacing Conv1 by Conv2 results in an overestimate of CO{sub 2} over biospheric sink regions. The largest discrepancies result in a CO{sub 2} difference of about 7.8 ppm in the July NH boreal forest, which is about 30% of the CO{sub 2} seasonality for that area. These differences are compared to those produced by emission scenario variations constrained by the framework of Intergovernmental Panel on Climate Change (IPCC) to account for possible land use change and residual terrestrial CO{sub 2} sink. It is shown that the overestimated CO{sub 2} driven by Conv2 can be offset by introducing these supplemental emissions.

  11. The influence of deep convection on HCHO and HO in the upper troposphere over Europe

    Science.gov (United States)

    Bozem, Heiko; Pozzer, Andrea; Harder, Hartwig; Martinez, Monica; Williams, Jonathan; Lelieveld, Jos; Fischer, Horst

    2017-10-01

    Deep convection is an efficient mechanism for vertical trace gas transport from Earth's surface to the upper troposphere (UT). The convective redistribution of short-lived trace gases emitted at the surface typically results in a C-shaped profile. This redistribution mechanism can impact photochemical processes, e.g. ozone and radical production in the UT on a large scale due to the generally longer lifetimes of species like formaldehyde (HCHO) and hydrogen peroxide (H2O2), which are important HOx precursors (HOx = OH + HO2 radicals). Due to the solubility of HCHO and H2O2 their transport may be suppressed as they are efficiently removed by wet deposition. Here we present a case study of deep convection over Germany in the summer of 2007 within the framework of the HOOVER II project. Airborne in situ measurements within the in- and outflow regions of an isolated thunderstorm provide a unique data set to study the influence of deep convection on the transport efficiency of soluble and insoluble trace gases. Comparing the in- and outflow indicates an almost undiluted transport of insoluble trace gases from the boundary layer to the UT. The ratios of out : inflow of CO and CH4 are 0.94 ± 0.04 and 0.99 ± 0.01, respectively. For the soluble species HCHO and H2O2 these ratios are 0.55 ± 0.09 and 0.61 ± 0.08, respectively, indicating partial scavenging and washout. Chemical box model simulations show that post-convection secondary formation of HCHO and H2O2 cannot explain their enhancement in the UT. A plausible explanation, in particular for the enhancement of the highly soluble H2O2, is degassing from cloud droplets during freezing, which reduces the retention coefficient.

  12. Physical balances in subseafloor hydrothermal convection cells

    Science.gov (United States)

    Jupp, Tim E.; Schultz, Adam

    2004-05-01

    We use a simplified model of convection in a porous medium to investigate the balances of mass and energy within a subseafloor hydrothermal convection cell. These balances control the steady state structure of the system and allow scalings for the height, permeability, and residence time of the "reaction zone" at the base of the cell to be calculated. The scalings are presented as functions of (1) the temperature TD of the heat source driving the convection and (2) the total power output ΦU. The model is then used to illustrate how the nonlinear thermodynamic properties of water may impose the observed upper limit of ˜400°C on vent temperatures. The properties of water at hydrothermal conditions are contrasted with those of a hypothetical "Boussinesq fluid" for which temperature variations in fluid properties are either linearized or ignored. At hydrothermal pressures, water transports a maximum amount of energy by buoyancy-driven advection at ˜400°C. This maximum is a consequence of the nonlinear thermodynamic properties of water and does not arise for a simple Boussinesq fluid. Inspired by the "Malkus hypothesis" and by recent work on dissipative systems, we speculate that convection cells in porous media attain a steady state in which the upwelling temperature TU maximizes the total power output of the cell. If true, this principle would explain our observation (in previous numerical simulations) that water in hydrothermal convection cells upwells at TU ˜ 400°C when driven by a heat source above ˜500°C.

  13. Convective mass transfer around a dissolving bubble

    Science.gov (United States)

    Duplat, Jerome; Grandemange, Mathieu; Poulain, Cedric

    2017-11-01

    Heat or mass transfer around an evaporating drop or condensing vapor bubble is a complex issue due to the interplay between the substrate properties, diffusion- and convection-driven mass transfer, and Marangoni effects, to mention but a few. In order to disentangle these mechanisms, we focus here mainly on the convective mass transfer contribution in an isothermal mass transfer problem. For this, we study the case of a millimetric carbon dioxide bubble which is suspended under a substrate and dissolved into pure liquid water. The high solubility of CO2 in water makes the liquid denser and promotes a buoyant-driven flow at a high (solutal) Rayleigh number (Ra˜104 ). The alteration of p H allows the concentration field in the liquid to be imaged by laser fluorescence enabling us to measure both the global mass flux (bubble volume, contact angle) and local mass flux around the bubble along time. After a short period of mass diffusion, where the boundary layer thickens like the square root of time, convection starts and the CO2 is carried by a plume falling at constant velocity. The boundary layer thickness then reaches a plateau which depends on the bubble cross section. Meanwhile the plume velocity scales like (dV /d t )1 /2 with V being the volume of the bubble. As for the rate of volume loss, we recover a constant mass flux in the diffusion-driven regime followed by a decrease in the volume V like V2 /3 after convection has started. We present a model which agrees well with the bubble dynamics and discuss our results in the context of droplet evaporation, as well as high Rayleigh convection.

  14. Risk factors associated with preterm birth among singletons following assisted reproductive technology in Australia 2007-2009--a population-based retrospective study.

    Science.gov (United States)

    Xu, Xu K; Wang, Yueping A; Li, Zhuoyang; Lui, Kei; Sullivan, Elizabeth A

    2014-12-07

    Preterm birth, a leading cause of neonatal death, is more common in multiple births and thus there has being an increasing call for reducing multiple births in ART. However, few studies have compared risk factors for preterm births amongst ART and non-ART singleton birth mothers. A population-based study of 393,450 mothers, including 12,105 (3.1%) ART mothers, with singleton gestations born between 2007 and 2009 in 5 of the 8 jurisdictions in Australia. Univariable and multivariable logistic regression models were conducted to evaluate socio-demographic, medical and pregnancy factors associated with preterm births in contrasting ART and non-ART mothers. Ten percent of singleton births to ART mothers were preterm compared to 6.8% for non-ART mothers (P disadvantaged (12.4% in the lowest quintile vs 20.7%), less likely to be smokers (3.8% vs 19.4%), more likely to be first time mothers (primiparous 62.4% vs 40.5%), had more preexisting hypertension and complications during pregnancy. Irrespective of the mode of conception, preexisting medical and pregnancy complications of hypertension, diabetes and antepartum hemorrhages were consistently associated with preterm birth. In contrast, socio-demographic variables, namely young and old maternal age (34), socioeconomic disadvantage (most disadvantaged quintile Odds Ratio (OR) 0.95, 95% Confidence Interval (CI): 0.77-1.17), smoking (OR 1.12, 95%CI: 0.79-1.61) and priminarity (OR 1.19, 95% CI: 1.05-1.35, AOR not significant) shown to be associated with elevated risk of preterm birth for non-ART mothers were not demonstrated for ART mothers, even after adjusting for potential confounders. Nonetheless, in multivariable analysis, the association between ART and the elevated risk for singleton preterm birth persisted after controlling for all included confounding medical, pregnancy and socio-economic factors (AOR 1.51, 95% CI: 1.42-1.61). Preterm birth rate is approximately one-and-a-half-fold higher in ART mothers than non

  15. Seismic Wave Velocity in Earth's Shallow Core

    Science.gov (United States)

    Alexandrakis, C.; Eaton, D. W.

    2008-12-01

    Studies of the outer core indicate that it is composed of liquid Fe and Ni alloyed with a ~10% fraction of light elements such as O, S or Si. Recently, unusual features, such as sediment accumulation, immiscible fluid layers or stagnant convection, have been predicted in the shallow core region. Secular cooling and compositional buoyancy drive vigorous convection that sustains the geodynamo, although critical details of light-element composition and thermal regime remain uncertain. Seismic velocity models can provide important constraints on the light element composition, however global reference models, such as Preliminary Reference Earth Model (PREM), IASP91 and AK135 vary significantly in the 200 km below the core-mantle boundary. Past studies of the outermost core velocity structure have been hampered by traveltime uncertainties due to lowermost mantle heterogeneities. The recently published Empirical Transfer Function (ETF) method has been shown to reduce the uncertainty using a waveform stacking approach to improve global observations of SmKS teleseismic waves. Here, we apply the ETF method to achieve a precise top-of-core velocity measurement of 8.05 ± 0.03 km/s. This new model accords well with PREM. Since PREM is based on the adiabatic form of the Adams-Williamson equation, it assumes a well mixed (i.e. homogeneous) composition. This result suggests a lack of heterogeneity in the outermost core due to layering or stagnant convection.

  16. Whole-mantle convection with tectonic plates preserves long-term global patterns of upper mantle geochemistry.

    Science.gov (United States)

    Barry, T L; Davies, J H; Wolstencroft, M; Millar, I L; Zhao, Z; Jian, P; Safonova, I; Price, M

    2017-05-12

    The evolution of the planetary interior during plate tectonics is controlled by slow convection within the mantle. Global-scale geochemical differences across the upper mantle are known, but how they are preserved during convection has not been adequately explained. We demonstrate that the geographic patterns of chemical variations around the Earth's mantle endure as a direct result of whole-mantle convection within largely isolated cells defined by subducting plates. New 3D spherical numerical models embedded with the latest geological paleo-tectonic reconstructions and ground-truthed with new Hf-Nd isotope data, suggest that uppermost mantle at one location (e.g. under Indian Ocean) circulates down to the core-mantle boundary (CMB), but returns within ≥100 Myrs via large-scale convection to its approximate starting location. Modelled tracers pool at the CMB but do not disperse ubiquitously around it. Similarly, mantle beneath the Pacific does not spread to surrounding regions of the planet. The models fit global patterns of isotope data and may explain features such as the DUPAL anomaly and long-standing differences between Indian and Pacific Ocean crust. Indeed, the geochemical data suggests this mode of convection could have influenced the evolution of mantle composition since 550 Ma and potentially since the onset of plate tectonics.

  17. A continuous and prognostic convection scheme based on buoyancy, PCMT

    Science.gov (United States)

    Guérémy, Jean-François; Piriou, Jean-Marcel

    2016-04-01

    A new and consistent convection scheme (PCMT: Prognostic Condensates Microphysics and Transport), providing a continuous and prognostic treatment of this atmospheric process, is described. The main concept ensuring the consistency of the whole system is the buoyancy, key element of any vertical motion. The buoyancy constitutes the forcing term of the convective vertical velocity, which is then used to define the triggering condition, the mass flux, and the rates of entrainment-detrainment. The buoyancy is also used in its vertically integrated form (CAPE) to determine the closure condition. The continuous treatment of convection, from dry thermals to deep precipitating convection, is achieved with the help of a continuous formulation of the entrainment-detrainment rates (depending on the convective vertical velocity) and of the CAPE relaxation time (depending on the convective over-turning time). The convective tendencies are directly expressed in terms of condensation and transport. Finally, the convective vertical velocity and condensates are fully prognostic, the latter being treated using the same microphysics scheme as for the resolved condensates but considering the convective environment. A Single Column Model (SCM) validation of this scheme is shown, allowing detailed comparisons with observed and explicitly simulated data. Four cases covering the convective spectrum are considered: over ocean, sensitivity to environmental moisture (S. Derbyshire) non precipitating shallow convection to deep precipitating convection, trade wind shallow convection (BOMEX) and strato-cumulus (FIRE), together with an entire continental diurnal cycle of convection (ARM). The emphasis is put on the characteristics of the scheme which enable a continuous treatment of convection. Then, a 3D LAM validation is presented considering an AMMA case with both observations and a CRM simulation using the same initial and lateral conditions as for the parameterized one. Finally, global

  18. Hydrothermal, multiphase convection of H2O-NaCl fluids from ambient to magmatic temperatures : A new numerical scheme and benchmarks for code comparison

    NARCIS (Netherlands)

    Weis, P.; Driesner, T.; Coumou, D.; Geiger, S.

    2014-01-01

    Thermohaline convection of subsurface fluids strongly influences heat and mass fluxes within the Earth's crust. The most effective hydrothermal systems develop in the vicinity of magmatic activity and can be important for geothermal energy production and ore formation. As most parts of these systems

  19. Fertility treatment and child intelligence, attention, and executive functions in 5-year-old singletons: a cohort study.

    Science.gov (United States)

    Bay, B; Mortensen, E L; Kesmodel, U S

    2014-12-01

    To assess the association of fertility treatment and subfertility with offspring intelligence, attention, and executive functions in 5-year-old singletons. Follow-up study. Denmark 2003-2008. A cohort of 1782 children sampled from the Danish National Birth Cohort. The children were tested with a neuropsychological battery at age five. In addition to tests of intelligence, attention and executive functions, the follow up included extensive information on important covariates. The analyses were conducted using multiple linear regression and adjusted for parental educational level, maternal intelligence, age, parity, body mass index, smoking in pregnancy, alcohol consumption in pregnancy and child gender, child age, and examiner. Wechsler Preschool and Primary Scale of Intelligence-Revised, the Test of Everyday Attention for Children at Five, and the Behavior Rating Inventory of Executive Functions scores. A consistent pattern of nonsignificantly lower scores were only observed for intelligence and executive functions in children born after fertility treatment or by subfertile parents when the results were unadjusted for maternal intelligence and parental educational level. When adjusted for these and other covariates, there were no significant mean differences in intelligence (mean difference -2.8, 95% CI -7.8, 2.2), overall attention (-0.1, 95% CI -0.6, 0.3), or parent-rated executive functions (-0.1, 95% CI -3.0, 2.9) between children born after spontaneous conception and children born to parents conceiving after fertility treatment. Similarly, there were no significant mean differences in intelligence (mean difference 0.6, 95% CI -2.2, 3.4), overall attention (0.1, 95% CI -0.2, 0.4), or parent-rated executive functions (1.0, 95% CI -1.8, 3.7) between children born after spontaneous conception and children born to subfertile parents waiting more than 12 months before conceiving naturally. This study suggests that parental subfertility and fertility treatment are

  20. EFFECT OF EARLY PREGNANCY BODY MASS INDEX ON PREGNANCY OUTCOMES IN WOMEN DELIVERING SINGLETON BABIES- AN OBSERVATIONAL STUDY

    Directory of Open Access Journals (Sweden)

    Divya Vishnu

    2017-02-01

    Full Text Available BACKGROUND Maternal overweight/obesity causes many complications during pregnancy and delivery. It can also increase neonatal and infant morbidity and mortality. BMI is an important measure of under/overweight. This observational study examines the correlation between maternal Body Mass Index (BMI with maternal outcome in women. MATERIALS AND METHODS This study was conducted at Department of Obstetrics and Gynaecology, Government Medical College, Kottayam, Kerala, for a period of one year. A sample of 300 pregnant women with intrauterine pregnancy of gestational age <12 weeks at first visit was taken for this study with an age between 18 and 35 years with singleton pregnancy. BMI of these women were calculated and they were classified into two categories (BMI <23 kg/m2 and BMI ≥23 kg/m2 . The Chi-square test was done to find the association of BMI and various maternal outcomes. RESULTS In the sample of 300 pregnant women, 39% were having BMI <23 kg/m2 and 61% were having BMI ≥23 kg/m2 . Pregnant women with BMI ≥23 kg/m2 were found to have significantly increased risk of developing gestational hypertension, gestational diabetes and macrosomia. We found that a significantly increased need of induction and increased risk of developing intrapartum and postpartum complications in those with BMI ≥23 kg/m2 . Our study also found out that an increased incidence of elective as well as emergency caesareans and increased risk of neonatal complications in women whose BMI ≥23 kg/m2 . CONCLUSION Adverse maternal and perinatal outcomes are significantly related to extremes of BMI categories and least complications were seen in normal BMI group. Therefore, it is ideal to reduce the body weight to an optimal level so that the complications, which are attributed to overweight and obesity can be reduced. We recommended future research on the association of BMI and maternal outcomes involving large samples comparable to those done in developed countries.

  1. Little Earth Experiment: An instrument to model planetary cores.

    Science.gov (United States)

    Aujogue, Kélig; Pothérat, Alban; Bates, Ian; Debray, François; Sreenivasan, Binod

    2016-08-01

    In this paper, we present a new experimental facility, Little Earth Experiment, designed to study the hydrodynamics of liquid planetary cores. The main novelty of this apparatus is that a transparent electrically conducting electrolyte is subject to extremely high magnetic fields (up to 10 T) to produce electromagnetic effects comparable to those produced by moderate magnetic fields in planetary cores. This technique makes it possible to visualise for the first time the coupling between the principal forces in a convection-driven dynamo by means of Particle Image Velocimetry (PIV) in a geometry relevant to planets. We first present the technology that enables us to generate these forces and implement PIV in a high magnetic field environment. We then show that the magnetic field drastically changes the structure of convective plumes in a configuration relevant to the tangent cylinder region of the Earth's core.

  2. Using Jupiter's gravitational field to probe the Jovian convective dynamo.

    Science.gov (United States)

    Kong, Dali; Zhang, Keke; Schubert, Gerald

    2016-03-23

    Convective motion in the deep metallic hydrogen region of Jupiter is believed to generate its magnetic field, the strongest in the solar system. The amplitude, structure and depth of the convective motion are unknown. A promising way of probing the Jovian convective dynamo is to measure its effect on the external gravitational field, a task to be soon undertaken by the Juno spacecraft. We calculate the gravitational signature of non-axisymmetric convective motion in the Jovian metallic hydrogen region and show that with sufficiently accurate measurements it can reveal the nature of the deep convection.

  3. Gregarious convection and radiative feedbacks in idealized worlds

    Science.gov (United States)

    Mapes, B. E.

    2016-06-01

    What role does convection play in cloud feedbacks? What role does convective aggregation play in climate? A flurry of recent studies explores "self-aggregation" of moist convection in diverse simulations using explicit convection and interactive radiation. The implications involve upper level dry areas acting as infrared windows—the climate system's "radiator fins." A positive feedback maintains these: dry columns undergo radiative cooling which drives descent and further drying. If the resulting clumpiness of vapor and cloud fields depends systematically on global temperature, then convective organization could be a climate system feedback. How reconcilable and how relevant are these interesting but idealized studies?

  4. Edible Earth and Space Science Activities

    Science.gov (United States)

    Lubowich, D.; Shupla, C.

    2014-07-01

    In this workshop we describe using Earth and Space Science demonstrations with edible ingredients to increase student interest. We show how to use chocolate, candy, cookies, popcorn, bagels, pastries, Pringles, marshmallows, whipped cream, and Starburst candy for activities such as: plate tectonics, the interior structure of the Earth and Mars, radioactivity/radioactive dating of rocks and stars, formation of the planets, lunar phases, convection, comets, black holes, curvature of space, dark energy, and the expansion of the Universe. In addition to creating an experience that will help students remember specific concepts, edible activities can be used as a formative assessment, providing students with the opportunity to create something that demonstrates their understanding of the model. The students often eat the demonstrations. These demonstrations are an effective teaching tool for all ages, and can be adapted for cultural, culinary, and ethnic differences among the students.

  5. Magnetic Control of Convection during Protein Crystallization

    Science.gov (United States)

    Ramachandran, N.; Leslie, F. W.

    2004-01-01

    An important component in biotechnology, particularly in the area of protein engineering and rational drug design is the knowledge of the precise three-dimensional molecular structure of proteins. The quality of structural information obtained from X-ray diffraction methods is directly dependent on the degree of perfection of the protein crystals. As a consequence, the growth of high quality macromolecular Crystals for diffraction analyses has been the central focus for bio-chemists, biologists, and bioengineers. Macromolecular crystals are obtained from solutions that contain the crystallizing species in equilibrium with higher aggregates, ions, precipitants, other possible phases of the protein, foreign particles, the walls of container, and a likely host of other impurities. By changing transport modes in general, i.e., reduction of convection and Sedimentation as is achieved in "microgravity", we have been able to dramatically affect the movement and distribution of macromolecules in the fluid, and thus their transport, f o d o n of crystal nuclei, and adsorption to the crystal surface. While a limited number of high quality crystals from space flights have been obtained, as the recent National Research Council (NRC) review of the NASA microgravity crystallization program pointed out, the scientific approach and research in crystallization of proteins has been mainly empirical yielding inconclusive results. We postulate that we can reduce convection in ground-based experiments and we can understand the different aspects of convection control through the use of strong magnetic fields and field gradients. We postulate that limited convection in a magnetic field will provide the environment for the growth of high quality crystals. The approach exploits the variation of fluid magnetic susceptibility with counteracts on for this purpose and the convective damping is realized by appropriately positioning the crystal growth cell so that the magnetic susceptibility

  6. Convective equilibrium and mixing-length theory for stellarator reactors

    Energy Technology Data Exchange (ETDEWEB)

    Ho, D.D.M.; Kulsrud, R.M.

    1985-09-01

    In high ..beta.. stellarator and tokamak reactors, the plasma pressure gradient in some regions of the plasma may exceed the critical pressure gradient set by ballooning instabilities. In these regions, convective cells break out to enhance the transport. As a result, the pressure gradient can rise only slightly above the critical gradient and the plasma is in another state of equilibrium - ''convective equilibrium'' - in these regions. Although the convective transport cannot be calculated precisely, it is shown that the density and temperature profiles in the convective region can still be estimated. A simple mixing-length theory, similar to that used for convection in stellar interiors, is introduced in this paper to provide a qualitative description of the convective cells and to show that the convective transport is highly efficient. A numerical example for obtaining the density and temperature profiles in a stellarator reactor is given.

  7. Behaviors and transitions along the path to magnetostrophic convection

    Science.gov (United States)

    Grannan, A. M.; Vogt, T.; Horn, S.; Hawkins, E. K.; Aggarwal, A.; Aurnou, J. M.

    2017-12-01

    The generation of magnetic fields in planetary and stellar interiors are believed to be controlled primarily by turbulent convection constrained by Coriolis and Lorentz forces in their electrically conducting fluid layers. Yet relatively few laboratory experiments are capable of investigating the different regimes of turbulent magnetohydrodynamic convection. In this work, we perform one laboratory experiment in a cylinder at a fixed heat flux using the liquid metal gallium in order to investigate, sequentially: Rayleigh-Bènard convection without any imposed constraints, magnetoconvection with a Lorentz constraint imposed by vertical magnetic field, rotating convection with a Coriolis constraint imposed by rotation, and finally the magnetostrophic convective regime where both Coriolis and Lorentz are imposed and equal. Using an array of internal and external temperature probes, we show that each regime along the path to magnetostrophic convection is unique. The behaviors and transitions in the dominant modes of convection as well as their fundamental frequencies and wavenumbers are investigated.

  8. Convective equilibrium and mixing-length theory for stellarator reactors

    International Nuclear Information System (INIS)

    Ho, D.D.M.; Kulsrud, R.M.

    1985-09-01

    In high β stellarator and tokamak reactors, the plasma pressure gradient in some regions of the plasma may exceed the critical pressure gradient set by ballooning instabilities. In these regions, convective cells break out to enhance the transport. As a result, the pressure gradient can rise only slightly above the critical gradient and the plasma is in another state of equilibrium - ''convective equilibrium'' - in these regions. Although the convective transport cannot be calculated precisely, it is shown that the density and temperature profiles in the convective region can still be estimated. A simple mixing-length theory, similar to that used for convection in stellar interiors, is introduced in this paper to provide a qualitative description of the convective cells and to show that the convective transport is highly efficient. A numerical example for obtaining the density and temperature profiles in a stellarator reactor is given

  9. A numerical model of mantle convection with deformable, mobile continental lithosphere within three-dimensional spherical geometry

    Science.gov (United States)

    Yoshida, M.

    2010-12-01

    A new numerical simulation model of mantle convection with a compositionally and rheologically heterogeneous, deformable, mobile continental lithosphere is presented for the first time by using three-dimensional regional spherical-shell geometry (Yoshida, 2010, Earth Planet. Sci. Lett.). The numerical results revealed that one of major factor that realizes the supercontinental breakup and subsequent continental drift is a pre-existing, weak (low-viscosity) continental margin (WCM) in the supercontinent. Characteristic tectonic structures such as young orogenic belts and suture zones in a continent are expected to be mechanically weaker than the stable part of the continental lithosphere with the cratonic root (or cratonic lithosphere) and yield lateral viscosity variations in the continental lithosphere. In the present-day Earth's lithosphere, the pre-existing, mechanically weak zones emerge as a diffuse plate boundary. However, the dynamic role of the WCM in the stability of continental lithosphere has not been understood in terms of geophysics. In my numerical model, a compositionally buoyant and highly viscous continental assemblage with pre-existing WCMs, analogous to the past supercontinent, is modeled and imposed on well-developed mantle convection whose vigor of convection, internal heating rate, and rheological parameters are appropriate for the Earth's mantle. The visco-plastic oceanic lithosphere and the associated subduction of oceanic plates are incorporated. The time integration of the advection of continental materials with zero chemical diffusion is performed by a tracer particle method. The time evolution of mantle convection after setting the model supercontinent is followed over 800 Myr. Earth-like continental drift is successfully reproduced, and the characteristic thermal interaction between the mantle and the continent/supercontinent is observed in my new numerical model. Results reveal that the WCM protects the cratonic lithosphere from being

  10. Convective Flow in an Aquifer Layer

    Directory of Open Access Journals (Sweden)

    Dambaru Bhatta

    2017-10-01

    Full Text Available Here, we investigate weakly nonlinear hydrothermal two-dimensional convective flow in a horizontal aquifer layer with horizontal isothermal and rigid boundaries. We treat such a layer as a porous medium, where Darcy’s law holds, subjected to the conditions that the porous layer’s permeability and the thermal conductivity are variable in the vertical direction. This analysis is restricted to the case that the subsequent hydraulic resistivity and diffusivity have a small rate of change with respect to the vertical variable. Applying the weakly nonlinear approach, we derive various order systems and express their solutions. The solutions for convective flow quantities such as vertical velocity and the temperature that arise as the Rayleigh number exceeds its critical value are computed and presented in graphical form.

  11. Numerical Simulation of a Convective Turbulence Encounter

    Science.gov (United States)

    Proctor, Fred H.; Hamilton, David W.; Bowles, Roland L.

    2002-01-01

    A numerical simulation of a convective turbulence event is investigated and compared with observational data. The numerical results show severe turbulence of similar scale and intensity to that encountered during the test flight. This turbulence is associated with buoyant plumes that penetrate the upper-level thunderstorm outflow. The simulated radar reflectivity compares well with that obtained from the aircraft's onboard radar. Resolved scales of motion as small as 50 m are needed in order to accurately diagnose aircraft normal load accelerations. Given this requirement, realistic turbulence fields may be created by merging subgrid-scales of turbulence to a convective-cloud simulation. A hazard algorithm for use with model data sets is demonstrated. The algorithm diagnoses the RMS normal loads from second moments of the vertical velocity field and is independent of aircraft motion.

  12. Equilibrium Transport in Double-Diffusive Convection

    Science.gov (United States)

    2011-06-01

    convection changes in other environments. External planetary systems, such as the atmospheric makeup of planets within our solar system, are...21) where ( fx ,fy) are the Floquet factors in x and y. Substituting Equation (21) in the linearized governing equations and collecting...the individual Fourier components reduces the stability problem to matrix form Equation (13). Maximizing the growth rates with respect to ( fx ,fy,m

  13. Natural convection cooling of spent fuels depository

    International Nuclear Information System (INIS)

    Menant, B.

    2000-01-01

    The operating CASCAD Facility was commissioned at Cadarache since 1990. Spent fuels are being storage for a 50 years period. The heat giving by the wastes is evacuated essentially by natural convection. The Trio U software is applied to the thermohydraulic operating of the system. The results allow to illustrate the installation and show system instabilities effects which appear at many scales. (A.L.B.)

  14. An experimental study of mixed convection

    International Nuclear Information System (INIS)

    Saez, Manuel

    1998-01-01

    The aim of our study is to establish a reliable data base for improving thermal-hydraulic codes, in the field of turbulent flows with buoyancy forces. The flow considered is mixed convection in the Reynolds and Richardson number range: Re=10 3 to 6*10 4 and Ri=10 -4 to 1. Experiments are carried out in an upward turbulent flow between vertical parallel plates at different wall temperatures. Part 1 gives a detailed data base of turbulent mixed flow of free and forced convection. Part II presents the installation and the calibration system intended for probes calibration. Part III describes the measurement technique (constant-temperature probe and cold-wire probe) and the method for measuring the position of the hot-wire anemometer from the wall surface. The measurement accuracy is within 0.001 mm in the present system. Part IV relates the development of a method for near wall measurements. This correction procedure for hot-wire anemometer close to wall has been derived on the basis of a two-dimensional numerical study. The method permits to obtain a quantitative correction of the wall influence on hot-wires and takes into account the velocity profile and the effects the wall material has on the heat loss. Part V presents the experimental data obtained in the channel in forced and mixed convection. Results obtained in the forced convection regime serve as a verification of the measurement technique close to the wall and give the conditions at the entrance of the test section. The effects of the buoyancy force on the mean velocity and temperature profiles are confirmed. The buoyancy strongly affects the flow structure and deforms the distribution of mean velocity. The velocity profiles are asymmetric. The second section of part V gives an approach of analytical wall functions with buoyancy forces, on the basis of the experimental data obtained in the test section. (author) [fr

  15. Simulating North American mesoscale convective systems with a convection-permitting climate model

    Science.gov (United States)

    Prein, Andreas F.; Liu, Changhai; Ikeda, Kyoko; Bullock, Randy; Rasmussen, Roy M.; Holland, Greg J.; Clark, Martyn

    2017-10-01

    Deep convection is a key process in the climate system and the main source of precipitation in the tropics, subtropics, and mid-latitudes during summer. Furthermore, it is related to high impact weather causing floods, hail, tornadoes, landslides, and other hazards. State-of-the-art climate models have to parameterize deep convection due to their coarse grid spacing. These parameterizations are a major source of uncertainty and long-standing model biases. We present a North American scale convection-permitting climate simulation that is able to explicitly simulate deep convection due to its 4-km grid spacing. We apply a feature-tracking algorithm to detect hourly precipitation from Mesoscale Convective Systems (MCSs) in the model and compare it with radar-based precipitation estimates east of the US Continental Divide. The simulation is able to capture the main characteristics of the observed MCSs such as their size, precipitation rate, propagation speed, and lifetime within observational uncertainties. In particular, the model is able to produce realistically propagating MCSs, which was a long-standing challenge in climate modeling. However, the MCS frequency is significantly underestimated in the central US during late summer. We discuss the origin of this frequency biases and suggest strategies for model improvements.

  16. Natural convection of nanofluids over a convectively heated vertical plate embedded in a porous medium

    Energy Technology Data Exchange (ETDEWEB)

    Ghalambaz, M.; Noghrehabadi, A.; Ghanbarzadeh, A., E-mail: m.ghalambaz@gmail.com, E-mail: ghanbarzadeh.a@scu.ac.ir [Department of Mechanical Engineering, Shahid Chamran University of Ahvaz, Ahvaz (Iran, Islamic Republic of)

    2014-04-15

    In this paper, the natural convective flow of nanofluids over a convectively heated vertical plate in a saturated Darcy porous medium is studied numerically. The governing equations are transformed into a set of ordinary differential equations by using appropriate similarity variables, and they are numerically solved using the fourth-order Runge-Kutta method associated with the Gauss-Newton method. The effects of parametric variation of the Brownian motion parameter (Nb), thermophoresis parameter (Nt) and the convective heating parameter (Nc) on the boundary layer profiles are investigated. Furthermore, the variation of the reduced Nusselt number and reduced Sherwood number, as important parameters of heat and mass transfer, as a function of the Brownian motion, thermophoresis and convective heating parameters is discussed in detail. The results show that the thickness of the concentration profiles is much lower than the temperature and velocity profiles. For low values of the convective heating parameter (Nc), as the Brownian motion parameter increases, the non-dimensional wall temperature increases. However, for high values of Nc, the effect of the Brownian motion parameter on the non-dimensional wall temperature is not significant. As the Brownian motion parameter increases, the reduced Sherwood number increases and the reduced Nusselt number decreases. (author)

  17. Earth mortars and earth-lime renders

    Directory of Open Access Journals (Sweden)

    Maria Fernandes

    2008-01-01

    Full Text Available Earth surface coatings play a decorative architectural role, apart from their function as wall protection. In Portuguese vernacular architecture, earth mortars were usually applied on stone masonry, while earth renders and plasters were used on indoors surface coatings. Limestone exists only in certain areas of the country and consequently lime was not easily available everywhere, especially on granite and schist regions where stone masonry was a current building technique. In the central west coast of Portugal, the lime slaking procedure entailed slaking the quicklime mixed with earth (sandy soil, in a pit; the resulting mixture would then be combined in a mortar or plaster. This was also the procedure for manufactured adobes stabilized with lime. Adobe buildings with earth-lime renderings and plasters were also traditional in the same region, using lime putty and lime wash for final coat and decoration. Classic decoration on earth architecture from the 18th-19th century was in many countries a consequence of the François Cointeraux (1740-1830 manuals - Les Cahiers d'Architecture Rurale" (1793 - a French guide for earth architecture and building construction. This manual arrived to Portugal in the beginning of XIX century, but was never translated to Portuguese. References about decoration for earth houses were explained on this manual, as well as procedures about earth-lime renders and ornamentation of earth walls; in fact, these procedures are exactly the same as the ones used in adobe buildings in this Portuguese region. The specific purpose of the present paper is to show some cases of earth mortars, renders and plasters on stone buildings in Portugal and to explain the methods of producing earth-lime renders, and also to show some examples of rendering and coating with earth-lime in Portuguese adobe vernacular architecture.

  18. Near Earth Objects

    DEFF Research Database (Denmark)

    Wolff, Stefan

    2006-01-01

    , Near Earth Objects: Asteroids and comets following paths that bring them near the Earth. NEOs have collided with the Earth since its formation, some causing local devastation, some causing global climate changes, yet the threat from a collision with a near Earth object has only recently been recognised...

  19. Contribution of risk factors to extremely, very and moderately preterm births - register-based analysis of 1,390,742 singleton births.

    Directory of Open Access Journals (Sweden)

    Sari Räisänen

    Full Text Available Preterm birth, defined as birth occurring before 37 weeks gestation, is one of the most significant contributors to neonatal mortality and morbidity, with long-term adverse consequences for health, and cognitive outcome.The aim of the present study was to identify risk factors of preterm birth (≤36+6 weeks gestation among singleton births and to quantify the contribution of risk factors to socioeconomic disparities in preterm birth.A retrospective population-based case-control study using data derived from the Finnish Medical Birth Register. A total population of singleton births in Finland from 1987-2010 (n = 1,390,742 was reviewed.Among all singleton births (n = 1,390,742, 4.6% (n = 63,340 were preterm (<37 weeks, of which 0.3% (n = 4,452 were classed as extremely preterm, 0.4% (n = 6,213 very preterm and 3.8% (n = 54,177 moderately preterm. Smoking alone explained up to 33% of the variation in extremely, very and moderately preterm birth incidence between high and the low socioeconomic status (SES groups. Reproductive risk factors (placental abruption, placenta previa, major congenital anomaly, amniocentesis, chorionic villus biopsy, anemia, stillbirth, small for gestational age (SGA and fetal sex altogether explained 7.7-25.0% of the variation in preterm birth between SES groups.Smoking explained about one third of the variation in preterm birth groups between SES groups whereas the contribution of reproductive risk factors including placental abruption, placenta previa, major congenital anomaly, amniocentesis, chorionic villus biopsy, anemia, stillbirth, SGA and fetal sex was up to one fourth.

  20. Transport Properties of Earth's Core

    Science.gov (United States)

    Cohen, R. E.; Zhang, P.; Xu, J.

    2016-12-01

    One of the most important parameters governing the original heat that drives all processes in the Earth is the thermal conductivity of Earth's core. Heat is transferred through the core by convection and conduction, and the convective component provides energy to drive the geodynamo. Sha and Cohen (2011) found that the electrical conductivity of solid hcp-iron was much higher than had been assumed by geophysicists, based on electronic structure computations for electron-phonon scattering (e-p) within density functional theory [1]. Thermal conductivity is related to electrical conductivity through the empirical Wiedmann-Franz law of 1853 [2]. Pozzo et al. [3] found that the high electrical conductivity of liquid iron alloys was too high for conventional dynamo models to work—there simply is not enough energy, so O'Rourke and Stevenson proposed a model driven by participation of Mg from the core [4], supported by recent experients [5]. Recent measurements by Ohta et al. show even lower resistivities than predicted by DFT e-p, and invoked a saturation model to account for this, [6] whereas, Konopkova et al. found thermal conductivities consistent with earlier geophysical estimates. [7] We are using first-principles methods, including dynamical mean field theory for electron-electron scattering, and highly converged e-p computations, and find evidence for strong anisotropy in solid hcp-Fe that may help explain some experimental results. The current status of the field will be discussed along with our recent results. This work is supported by the ERC Advanced grant ToMCaT, the NSF, and the Carnegie Institution for Science.[1] X. Sha and R. E. Cohen, J.Phys.: Condens.Matter 23, 075401 (2011).[2] R. Franz and G. Wiedemann, Annalen Physik 165, 497 (1853).[3] M. Pozzo, C. Davies, D. Gubbins, and D. Alfe, Nature 485, 355 (2012).[4] J. G. O'Rourke and D. J. Stevenson, Nature 529, 387 (2016).[5] J. Badro, J. Siebert, and F. Nimmo, Nature (2016).[6] K. Ohta, Y. Kuwayama, K

  1. Association of Maternal Obesity With Longitudinal Ultrasonographic Measures of Fetal Growth: Findings From the NICHD Fetal Growth Studies-Singletons.

    Science.gov (United States)

    Zhang, Cuilin; Hediger, Mary L; Albert, Paul S; Grewal, Jagteshwar; Sciscione, Anthony; Grobman, William A; Wing, Deborah A; Newman, Roger B; Wapner, Ronald; D'Alton, Mary E; Skupski, Daniel; Nageotte, Michael P; Ranzini, Angela C; Owen, John; Chien, Edward K; Craigo, Sabrina; Kim, Sungduk; Grantz, Katherine L; Louis, Germaine M Buck

    2018-01-01

    Despite the increasing prevalence of pregravid obesity, systematic evaluation of the association of maternal obesity with fetal growth trajectories is lacking. To characterize differences in fetal growth trajectories between obese and nonobese pregnant women, and to identify the timing of any observed differences. The Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Studies-Singletons study enrolled cohorts of pregnant women at 12 US health care institutions. Obese women (with prepregnancy body mass index > 30) and nonobese women (prepregnancy body mass indexes, 19-29.9) without major chronic diseases were recruited between 8 weeks and 0 days' gestation and 13 weeks and 6 days' gestation. A mixed longitudinal randomization scheme randomized participants into 1 of 4 schedules for 2-dimensional and 3-dimensional ultrasonograms to capture weekly fetal growth data throughout the remainder of their pregnancies. On each ultrasonogram, fetal humerus length, femur length, biparietal diameter, head circumference, and abdominal circumference were measured. Fetal growth curves were estimated using linear mixed models with cubic splines. Median differences in the fetal measures at each gestational week of the obese and nonobese participants were examined using the likelihood ratio and Wald tests after adjustment for maternal characteristics. The study enrolled 468 obese and 2334 nonobese women between 8 weeks and 0 days' gestation and 13 weeks and 6 days' gestation. After a priori exclusion criteria, 443 obese and 2320 nonobese women composed the final cohort. Commencing at 21 weeks' gestation, femur length and humerus length were significantly longer for fetuses of obese woman than those of nonobese women. Differences persisted in obese and nonobese groups through 38 weeks' gestation (median femur length, 71.0 vs 70.2 mm; P = .01; median humerus length, 62.2 vs 61.6 mm; P = .03). Averaged across gestation, head circumference

  2. Early Results of the NASA Convection and Moisture Experiment (CAMEX)

    Science.gov (United States)

    Hood, Robbie; Kakar, Ramesh

    2004-01-01

    As reported at previous sessions of the Interdepartmental Hurricane Conference, the Office of Earth Science within the National Aeronautics and Space Administration (NASA) has been sponsoring the Convection And Moisture Experiment (CAMEX) since 1993. Although originally designed to support satellite calibration and validation activities and to demonstrate new remote sensing technology pertinent to the global water cycle, the CAMEX research objectives have evolved to include a strong emphasis on hurricane observational studies. A hallmark of CAMEX success has been fruitful research collaborations with the Hurricane Research Division (HRD) of the National Oceanic and Atmospheric Administration (NOAA) and the Hurricanes At Landfall Initiative of the United States Weather Research Program. Satellite, aircraft, and ground-based observations collected during the 1998 and 200 1 field phases of CAMEX represent a wealth of information describing the three dimensional structure of tropical cyclones. Early research results gleaned from these observations have been submitted to a special issue of the American Meteorological Society Journal of Atmospheric Sciences. An overview of these early findings and their expected significance to the operational community will be presented during this talk.

  3. Magnetism, planetary rotation and convection in the solar system

    CERN Document Server

    1985-01-01

    On the 6th, 7th' and 8th April 1983, a conference entitled "Magnetism, planetary rotation and convection in the Solar System" was held in the School of Physics at the University of Newcastle upon Tyne. The purpose of the meeting was to celebrate the 60th birthday of Prof. Stanley Keith Runcorn and his, and his students' and associates', several decades of scientific achievement. The social programme, which consisted of excursions in Northumberland and Durham with visits to ancient castles and churches, to Hexham Abbey and Durham Cathedral, and dinners in Newcastle and Durham, was greatly enjoyed by those attending the meeting and by their guests. The success ofthe scientific programme can be judged by this special edition of Geophysical Surveys which is derived mainly from the papers given at the meeting. The story starts in the late 1940s when the question of the origin of the magnetic field of the Earth and such other heavenly bodies as had at that time been discovered as having a magnetic field, was exerci...

  4. Fetal fibronectin testing for prevention of preterm birth in singleton pregnancies with threatened preterm labor: a systematic review and metaanalysis of randomized controlled trials.

    Science.gov (United States)

    Berghella, Vincenzo; Saccone, Gabriele

    2016-10-01

    Fetal fibronectin is an extracellular matrix glycoprotein that is produced by amniocytes and cytotrophoblasts and has been shown to predict spontaneous preterm birth. The aim of this systematic review and metaanalysis of randomized clinical trials was to evaluate the effect of the use of fetal fibronectin in the prevention of preterm birth in singleton pregnancies with threatened preterm labor. The research was conducted with the use of MEDLINE, EMBASE, Web of Sciences, Scopus, ClinicalTrial.gov, OVID, and Cochrane Library as electronic databases from the inception of each database to February 2016. Selection criteria included randomized clinical trials of singleton gestations with threatened preterm labor that were assigned randomly to management based on fetal fibronectin results (ie, intervention group) or not (ie, comparison group). Types of participants included women with singleton gestations at 23 0/7 to 34 6/7 weeks with threatened preterm labor. Studies that included management that was also based on the use of sonographic cervical length were excluded. The primary outcome was preterm birth at birth at control group. No differences were found in the number of women who delivered within 7 days (12.8% vs 14.5%; relative risk, 0.76; 95% confidence interval, 0.47-1.21), in the mean of gestational age at delivery (mean difference, 0.20 week; 95% confidence interval, -0.26 to 0.67), in the rate of maternal hospitalization (27.4% vs 26.9%; relative risk, 1.07; 95% confidence interval, 0.80-1.44), in the use of tocolysis (25.3% vs 28.2%; relative risk, 0.97; 95% confidence interval, 0.75-1.24), antenatal steroids (29.2% vs 29.2%; relative risk, 1.05; 95% confidence interval, 0.79-1.39), in the mean time in the triage unit (mean difference, 0.60 hour; 95% confidence interval, -0.03 to 1.23) and in neonatal outcomes that included respiratory distress syndrome (1.3% vs 1.5%; relative risk, 0.91; 95% confidence interval, 0.06-14.06), and admission to the neonatal

  5. Convective initiation algorithm of Geo-KOMPSAT-2A (GK-2A) Advanced Meteorological Imager (AMI)

    Science.gov (United States)

    Park, Eun-Bin; Kim, Hye-Sil; Chung, Sung-Rae; Woo, Sun-Hee

    2017-10-01

    Geo-KOMPSAT-2A (GK-2A), which is scheduled to be launched in 2018, is a next geostationary satellite of South Korea, following on the Communication, Ocean and Meteorological Satellite (COMS). Advanced Meteorological Imager (AMI) on the GK-2A can scan the Earth with high resolution of both time and space. Furthermore, imageprocessing system of the GK-2A ground system will produce the level 1B images in 2 minutes. Convective Initiation (CI) algorithm can get more accurate weather forecast for heavy rainfall, thunderstorm and lightning through the high resolution of time and spatial data of the GK-2A AMI. Since the convective clouds are usually caused by rapidly developing clouds in unstable atmosphere, they can be detected by the temperature differences between two consecutive images. The CI algorithm of GK-2A AMI has four steps. Convective cloud masking is the first step in the CI algorithm, which extract mature cloud area using infrared channels. The next step is grouping cloud pixels using region growing method for immature cloud area. Then the clustered area (the immature cloud area) will be tested in overlapping detection step in sequential images. The last step of the CI algorithm is "Interest field tests" for each cloud object which can cause severe weather. The CI algorithm was tested by Himawari-8 Advanced Himawari Imager (AHI) data similar to the GK-2A AMI and validated with lightning data and radar observed in ground.

  6. EUREC4A: A Field Campaign to Elucidate the Couplings Between Clouds, Convection and Circulation

    Science.gov (United States)

    Bony, Sandrine; Stevens, Bjorn; Ament, Felix; Bigorre, Sebastien; Chazette, Patrick; Crewell, Susanne; Delanoë, Julien; Emanuel, Kerry; Farrell, David; Flamant, Cyrille; Gross, Silke; Hirsch, Lutz; Karstensen, Johannes; Mayer, Bernhard; Nuijens, Louise; Ruppert, James H.; Sandu, Irina; Siebesma, Pier; Speich, Sabrina; Szczap, Frédéric; Totems, Julien; Vogel, Raphaela; Wendisch, Manfred; Wirth, Martin

    2017-11-01

    Trade-wind cumuli constitute the cloud type with the highest frequency of occurrence on Earth, and it has been shown that their sensitivity to changing environmental conditions will critically influence the magnitude and pace of future global warming. Research over the last decade has pointed out the importance of the interplay between clouds, convection and circulation in controling this sensitivity. Numerical models represent this interplay in diverse ways, which translates into different responses of trade-cumuli to climate perturbations. Climate models predict that the area covered by shallow cumuli at cloud base is very sensitive to changes in environmental conditions, while process models suggest the opposite. To understand and resolve this contradiction, we propose to organize a field campaign aimed at quantifying the physical properties of trade-cumuli (e.g., cloud fraction and water content) as a function of the large-scale environment. Beyond a better understanding of clouds-circulation coupling processes, the campaign will provide a reference data set that may be used as a benchmark for advancing the modelling and the satellite remote sensing of clouds and circulation. It will also be an opportunity for complementary investigations such as evaluating model convective parameterizations or studying the role of ocean mesoscale eddies in air-sea interactions and convective organization.

  7. Spontaneous generation and reversals of mean flows in a convectively-generated internal gravity wave field

    Science.gov (United States)

    Couston, Louis-Alexandre; Lecoanet, Daniel; Favier, Benjamin; Le Bars, Michael

    2017-11-01

    We investigate via direct numerical simulations the spontaneous generation and reversals of mean zonal flows in a stably-stratified fluid layer lying above a turbulent convective fluid. Contrary to the leading idealized theories of mean flow generation by self-interacting internal waves, the emergence of a mean flow in a convectively-generated internal gravity wave field is not always possible because nonlinear interactions of waves of different frequencies can disrupt the mean flow generation mechanism. Strong mean flows thus emerge when the divergence of the Reynolds stress resulting from the nonlinear interactions of internal waves produces a strong enough anti-diffusive acceleration for the mean flow, which, as we will demonstrate, is the case when the Prandtl number is sufficiently low, or when the energy input into the internal wavefield by the convection and density stratification are sufficiently large. Implications for mean zonal flow production as observed in the equatorial stratospheres of the Earth, Saturn and Jupiter, and possibly occurring in other geophysical systems such as planetary and stellar interiors will be briefly discussed. Funding provided by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program through Grant Agreement No. 681835-FLUDYCO-ERC-2015-CoG.

  8. Convective Weather Avoidance with Uncertain Weather Forecasts

    Science.gov (United States)

    Karahan, Sinan; Windhorst, Robert D.

    2009-01-01

    Convective weather events have a disruptive impact on air traffic both in terminal area and in en-route airspaces. In order to make sure that the national air transportation system is safe and efficient, it is essential to respond to convective weather events effectively. Traffic flow control initiatives in response to convective weather include ground delay, airborne delay, miles-in-trail restrictions as well as tactical and strategic rerouting. The rerouting initiatives can potentially increase traffic density and complexity in regions neighboring the convective weather activity. There is a need to perform rerouting in an intelligent and efficient way such that the disruptive effects of rerouting are minimized. An important area of research is to study the interaction of in-flight rerouting with traffic congestion or complexity and developing methods that quantitatively measure this interaction. Furthermore, it is necessary to find rerouting solutions that account for uncertainties in weather forecasts. These are important steps toward managing complexity during rerouting operations, and the paper is motivated by these research questions. An automated system is developed for rerouting air traffic in order to avoid convective weather regions during the 20- minute - 2-hour time horizon. Such a system is envisioned to work in concert with separation assurance (0 - 20-minute time horizon), and longer term air traffic management (2-hours and beyond) to provide a more comprehensive solution to complexity and safety management. In this study, weather is dynamic and uncertain; it is represented as regions of airspace that pilots are likely to avoid. Algorithms are implemented in an air traffic simulation environment to support the research study. The algorithms used are deterministic but periodically revise reroutes to account for weather forecast updates. In contrast to previous studies, in this study convective weather is represented as regions of airspace that pilots

  9. The MJO Transition from Shallow to Deep Convection in CloudSat/CALIPSO Data and GISS GCM Simulations

    Science.gov (United States)

    DelGenio, Anthony G.; Chen, Yonghua; Kim, Daehyun; Yao, Mao-Sung

    2013-01-01

    The relationship between convective penetration depth and tropospheric humidity is central to recent theories of the Madden-Julian oscillation (MJO). It has been suggested that general circulation models (GCMs) poorly simulate the MJO because they fail to gradually moisten the troposphere by shallow convection and simulate a slow transition to deep convection. CloudSat and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) data are analyzed to document the variability of convection depth and its relation to water vapor during the MJO transition from shallow to deep convection and to constrain GCM cumulus parameterizations. Composites of cloud occurrence for 10MJO events show the following anticipatedMJO cloud structure: shallow and congestus clouds in advance of the peak, deep clouds near the peak, and upper-level anvils after the peak. Cirrus clouds are also frequent in advance of the peak. The Advanced Microwave Scanning Radiometer for EarthObserving System (EOS) (AMSR-E) columnwater vapor (CWV) increases by;5 mmduring the shallow- deep transition phase, consistent with the idea of moisture preconditioning. Echo-top height of clouds rooted in the boundary layer increases sharply with CWV, with large variability in depth when CWV is between;46 and 68 mm. International Satellite Cloud Climatology Project cloud classifications reproduce these climatological relationships but correctly identify congestus-dominated scenes only about half the time. A version of the Goddard Institute for Space Studies Model E2 (GISS-E2) GCM with strengthened entrainment and rain evaporation that produces MJO-like variability also reproduces the shallow-deep convection transition, including the large variability of cloud-top height at intermediate CWV values. The variability is due to small grid-scale relative humidity and lapse rate anomalies for similar values of CWV. 1.

  10. Global imaging of the Earth's deep interior: seismic constraints on (an)isotropy, density and attenuation

    NARCIS (Netherlands)

    Trampert, J.; Fichtner, A.

    2013-01-01

    Seismic tomography is the principal tool to probe the deep interior of the Earth. Models of seismic anisotropy induced by crystal alignment provide insight into the underlying convective motion, and variations of density allow us to discriminate between thermal and compositional heterogeneities.

  11. Strategic Repositioning for Convection Business Case Study: AR Vendor

    OpenAIRE

    Anindita, Pratisara Satwika; Toha, Mohamad

    2013-01-01

    The study aims to determine suitable position and strategy in order to reach superiority in convection business based on the company strengths and weaknesses. A study conducted in late 2012 at AR Vendor, a home-based convection company which focus on the t-shirt screen printing service. In response to the issue of the below average profit margin, the company has to rethink their position and strategy in handling the convection business environment. While AR Vendor business may growth in accor...

  12. Forced convection in nanoparticles doped nematics without reorientation

    International Nuclear Information System (INIS)

    Hakobyan, M.R.; Hakobyan, R.S.

    2016-01-01

    The problem of forced convection in the cell of nanoparticles doped nematic liquid crystal with both boundaries being free, plane and isotherm is discussed. These boundary conditions (offered by Rayleigh) allow to get simple and exact solution for boundary-value problem, from which its most important peculiarities can be clearly seen. Particularly, there appears a possibility to induce convection without reorientation of liquid crystal director. It was shown that nanoparticles could have significant influence on the convection

  13. Primary Issues of Mixed Convection Heat Transfer Phenomena

    International Nuclear Information System (INIS)

    Chae, Myeong-Seon; Chung, Bum-Jin

    2015-01-01

    The computer code analyzing the system operating and transient behavior must distinguish flow conditions involved with convective heat transfer flow regimes. And the proper correlations must be supplied to those flow regimes. However the existing safety analysis codes are focused on the Light Water Reactor and they are skeptical to be applied to the GCRs (Gas Cooled Reactors). One of the technical issues raise by the development of the VHTR is the mixed convection, which occur when the driving forces of both forced and natural convection are of comparable magnitudes. It can be encountered as in channel of the stacked with fuel elements and a decay heat removal system and in VHTR. The mixed convection is not intermediate phenomena with natural convection and forced convection but independent complicated phenomena. Therefore, many researchers have been studied and some primary issues were propounded for phenomena mixed convection. This paper is to discuss some problems identified through reviewing the papers for mixed convection phenomena. And primary issues of mixed convection heat transfer were proposed respect to thermal hydraulic problems for VHTR. The VHTR thermal hydraulic study requires an indepth study of the mixed convection phenomena. In this study we reviewed the classical flow regime map of Metais and Eckert and derived further issues to be considered. The following issues were raised: (1) Buoyancy aided an opposed flows were not differentiated and plotted in a map. (2) Experimental results for UWT and UHF condition were also plotted in the same map without differentiation. (3) The buoyancy coefficient was not generalized for correlating with buoyancy coefficient. (4) The phenomenon analysis for laminarization and returbulization as buoyancy effects in turbulent mixed convection was not established. (5) The defining to transition in mixed convection regime was difficult

  14. Forced and free convection turbulent boundary layers in gas lasers

    International Nuclear Information System (INIS)

    Woodroffe, J.A.

    1975-01-01

    Approximate expressions for the effect on optical path length through a turbulent vertical boundary layer caused by the combined presence of forced and free convection were obtained to first order in the asymptotic cases of dominant forced convection and dominant free convection. The effect in both cases is a reduction of the boundary-layer thickness. Characteristic scaling lengths are presented which aid in the optical analysis of the flowfield

  15. Hyperthyroidism is associated with work disability and loss of labour market income. A Danish register-based study in singletons and disease-discordant twin pairs.

    Science.gov (United States)

    Brandt, Frans; Thvilum, Marianne; Hegedüs, Laszlo; Brix, Thomas Heiberg

    2015-11-01

    To examine the risk of disability pension and changes in labour market income in patients with hyperthyroidism. From a 5% random sample of the Danish population and twins from the Danish Twin Registry we identified 1942 hyperthyroid singletons and 7768 non-hyperthyroid (matched 1:4) controls as well as 584 same-sex twin pairs discordant for hyperthyroidism. Singletons and twins were followed for a mean of 9 years (range 1-20). Cox regression analysis was used to examine the risk of disability pension and a difference-in-differences model was used to evaluate changes in labour market income. Hyperthyroid individuals had an increased risk of receiving disability pension: hazard ratio (HR) was 1.88, (95% CI: 1.57-2.24). Subdividing as to the cause of hyperthyroidism did not change this finding: Graves' disease (GD) HR was 1.51 (95% CI: 0.87-2.63) and toxic nodular goitre (TNG) HR was 2.10 (95% CI: 1.02-4.36). With respect to labour market income, the income of hyperthyroid individuals increased on average 1189 € less than their controls (Pmarket income, were seen within monozygotic twin pairs discordant for hyperthyroidism. Hyperthyroidism is associated with severe work disability as reflected by an 88% increased risk of receiving disability pension and a significant loss of labour market income. Similar results in monozygotic twins discordant for hyperthyroidism suggest that genetic confounding is unlikely. © 2015 European Society of Endocrinology.

  16. Outcome of singleton preterm small for gestational age infants born to mothers with pregnancy-induced hypertension. A population-based study.

    Science.gov (United States)

    Regev, Rivka H; Arnon, Shmuel; Litmanovitz, Ita; Bauer-Rusek, Sofia; Boyko, Valentina; Lerner-Geva, Liat; Reichman, Brian

    2015-04-01

    Pregnancy-induced hypertension (PIH) has been associated with a decreased risk of infant mortality in small for gestational age (SGA) preterm infants. To evaluate the influence of PIH on mortality and major neonatal morbidities in singleton preterm SGA infants, in the presence and absence of acute pregnancy complications. Population-based observational study of singleton SGA infants, born at 24 to 32 weeks gestation in the period 1995-2010 (n = 2139). Multivariable logistic regression analyses were used to assess the independent effect of PIH on mortality and neonatal morbidities. Acute pregnancy complications comprised premature labor, premature rupture of membranes >6 h, antepartum hemorrhage and clinical chorioamnionitis. In the absence of pregnancy complications, the odds ratio (95% confidence interval) for mortality (0.77; 0.50-1.16), survival without severe neurological morbidity (1.14; 0.79-1.65) and survival without bronchopulmonary dysplasia (BPD) (0.85; 0.59-1.21) were similar in the PIH versus no-PIH groups. In the presence of pregnancy complications, mortality (0.76; 0.40-1.44), survival without severe neurological morbidity (1.16; 0.64-2.12) and survival without BPD (1.04; 0.58-1.86) were also similar in the PIH versus no-PIH groups. PIH was not associated with improved outcome in preterm SGA infants, both in the presence and absence of acute pregnancy complications.

  17. Medical outcome of 8-year-old singleton ICSI children (born >or=32 weeks' gestation) and a spontaneously conceived comparison group.

    Science.gov (United States)

    Belva, F; Henriet, S; Liebaers, I; Van Steirteghem, A; Celestin-Westreich, S; Bonduelle, M

    2007-02-01

    There is little information about the long-term outcome of children born after ICSI. In this study, the eldest cohort of ICSI children worldwide, reaching the age of 8 years, was investigated at the prepubertal stage to monitor subsequent puberty and future fertility. To investigate possible health problems, a thorough medical and neurological examination was performed. Medical outcome of 8-year-old singletons (n=150) born through ICSI (>or=32 weeks) was compared with that of 147 singletons of the same age born after spontaneous conception (SC). Information about their general health was obtained from the parents by means of a questionnaire. Fifteen of 150 ICSI children experienced a major congenital malformation compared with 5/147 SC children (P Neurological examination did not show important differences between ICSI and SC children. ICSI children did not require more remedial therapy or surgery or hospitalization than SC children. Physical examination including a thorough neurological examination did not reveal important differences between the two groups. Major congenital malformations were significantly more frequent in the ICSI group. However, most of them were corrected by minor surgery. Further monitoring of these children at an older age is recommended.

  18. The Lifeworld Earth and a Modelled Earth

    Science.gov (United States)

    Juuti, Kalle

    2014-01-01

    The goal of this paper is to study the question of whether a phenomenological view of the Earth could be empirically endorsed. The phenomenological way of thinking considers the Earth as a material entity, but not as an object as viewed in science. In the learning science tradition, tracking the process of the conceptual change of the shape of the…

  19. A CloudSat cloud object partitioning technique and assessment and integration of deep convective anvil sensitivities to sea surface temperature

    Science.gov (United States)

    Igel, Matthew R.; Drager, Aryeh J.; van den Heever, Susan C.

    2014-09-01

    A cloud object partitioning algorithm is developed to provide a widely useful database of deep convective clouds. It takes contiguous CloudSat cloudy regions and identifies various length scales of clouds from a tropical, oceanic subset of data. The methodology identifies a level above which anvil characteristics become important by analyzing the cloud object shape. Below this level in what is termed the pedestal region, convective cores are identified based on reflectivity maxima. Identifying these regions allows for the assessment of length scales of the anvil and pedestal of deep convective clouds. Cloud objects are also appended with certain environmental quantities from European Centre for Medium-Range Weather Forecasts. Simple geospatial and temporal assessments show that the cloud object technique agrees with standard observations of local frequency of deep convective cloudiness. Deep convective clouds over tropical oceans play important roles in Earth's climate system. The newly developed data set is used to evaluate the response of tropical, deep convective clouds to sea surface temperature (SST). Several previously proposed responses are examined: the Fixed Anvil Temperature Hypothesis, the Iris Hypothesis, and the Thermostat Hypothesis. When the data are analyzed per cloud object, increasing SST is found to be associated with increased anvil thickness, decreased anvil width, and cooler cloud top temperatures. Implications for the corresponding hypotheses are discussed. A new response suggesting that the base temperature of deep convective anvils remains approximately constant with increasing SSTs is introduced. These cloud dependencies on SST are integrated to form a more comprehensive theory for deep convective anvil responses to SST.

  20. Assisted reproductive technology and the risk of pregnancy-related complications and adverse pregnancy outcomes in singleton pregnancies: a meta-analysis of cohort studies.

    Science.gov (United States)

    Qin, Jiabi; Liu, Xiaoying; Sheng, Xiaoqi; Wang, Hua; Gao, Shiyou

    2016-01-01

    To determine whether there are any increases in pregnancy-related complications and adverse pregnancy outcomes in singleton pregnancies after assisted reproductive technology (ART) compared with those conceived naturally. Meta-analysis. University-affiliated teaching hospital. Singleton pregnancies conceived with ART and naturally. PubMed, Google Scholar, Cochrane Libraries and Chinese database were searched through March 2015 to identify studies that met pre-stated inclusion criteria. Either a fixed- or a random-effects model was used to calculate the overall combined risk estimates. Subgroup analysis was performed to explore potential heterogeneity moderators. Pregnancy-related complications and adverse pregnancy outcomes. Fifty cohort studies comprising 161,370 ART and 2,280,241 spontaneously conceived singleton pregnancies were identified. The ART singleton pregnancies had a significantly increased risk of pregnancy-induced hypertension (relative risk [RR] 1.30, 95% confidence interval [CI] 1.04-1.62; I(2) = 79%), gestational diabetes mellitus (RR 1.31, 95% CI 1.13-1.53; I(2) = 6%), placenta previa (RR 3.71, 95% CI 2.67-5.16; I(2) = 72%), placental abruption (RR 1.83, 95% CI 1.49-2.24; I(2) = 22%), antepartum hemorrhage (RR 2.11, 95% CI 1.86-2.38; I(2) = 47%), postpartum hemorrhage (RR 1.29, 95% CI 1.06-1.57; I(2) = 65%), polyhydramnios (RR 1.74, 95% CI 1.24-2.45; I(2) = 0%), oligohydramnios (RR 2.14, 95% CI 1.53-3.01; I(2) = 0%), cesarean sections (RR 1.58, 95% CI 1.48-1.70; I(2) = 92%), preterm birth (RR 1.71, 95% CI 1.59-1.83; I(2)=80%), very preterm birth (RR 2.12, 95% CI 1.73-2.59; I(2) = 90%), low birth weight (RR 1.61, 95% CI 1.49-1.75; I(2) = 80%), very low birth weight (RR 2.12, 95% CI 1.84-2.43; I(2) = 67%), small for gestational age (RR 1.35, 95% CI 1.20-1.52; I(2) = 82%), perinatal mortality (RR 1.64, 95% CI 1.41-1.90; I(2)=45%), and congenital malformation (RR 1.37, 95% CI 1.29-1.45; I(2)=41%). Relevant heterogeneity moderators have been identified

  1. Rare earth sulfates

    International Nuclear Information System (INIS)

    Komissarova, L.N.; Shatskij, V.M.; Pokrovskij, A.N.; Chizhov, S.M.; Bal'kina, T.I.; Suponitskij, Yu.L.

    1986-01-01

    Results of experimental works on the study of synthesis conditions, structure and physico-chemical properties of rare earth, scandium and yttrium sulfates, have been generalized. Phase diagrams of solubility and fusibility, thermodynamic and crystallochemical characteristics, thermal stability of hydrates and anhydrous sulfates of rare earths, including normal, double (with cations of alkali and alkaline-earth metals), ternary and anion-mixed sulfates of rare earths, as well as their adducts, are considered. The state of ions of rare earths, scandium and yttrium in aqueous sulfuric acid solutions is discussed. Data on the use of rare earth sulfates are given

  2. Numerical simulation of two-dimensional Rayleigh-Benard convection

    Science.gov (United States)

    Grigoriev, Vasiliy V.; Zakharov, Petr E.

    2017-11-01

    This paper considered Rayleigh-Benard convection (natural convection). This is a flow, which is formed in a viscous medium when heated from below and cooled from above. As a result, are formed vortices (convective cells). This process is described by a system of nonlinear differential equations in Oberbeck-Boussinesq approximation. As the governing parameters characterizing convection states Rayleigh number, Prandtl number are picked. The problem is solved by using finite element method with computational package FEniCS. Numerical results for different Rayleigh numbers are obtained. Studied integral characteristic (Nusselt number) depending on the Rayleigh number.

  3. Cumulus convection and the terrestrial water-vapor distribution

    Science.gov (United States)

    Donner, Leo J.

    1988-01-01

    Cumulus convection plays a significant role in determining the structure of the terrestrial water vapor field. Cumulus convection acts directly on the moisture field by condensing and precipitating water vapor and by redistributing water vapor through cumulus induced eddy circulations. The mechanisms by which cumulus convection influences the terrestrial water vapor distribution is outlined. Calculations using a theory due to Kuo is used to illustrate the mechanisms by which cumulus convection works. Understanding of these processes greatly aids the ability of researchers to interpret the seasonal and spatial distribution of atmospheric water vapor by providing information on the nature of sources and sinks and the global circulation.

  4. Urban Influences on Convection and Lightning Over Houston

    National Research Council Canada - National Science Library

    Gauthier, Michael L

    2006-01-01

    The research presented in this dissertation addresses a fundamental question regarding urban, ultimately anthropogenic, influences on convection as it relates to lightning production and precipitation structure...

  5. Fourth Convection and Moisture Experiment ER2 MODIS Airborne Simulator

    Data.gov (United States)

    National Aeronautics and Space Administration — The Convection And Moisture EXperiment (CAMEX) 4 focused on the study of tropical cyclone (hurricane) development, tracking, intensification, and landfalling impacts...

  6. Natural convection in superposed fluid-porous layers

    CERN Document Server

    Bagchi, Aniruddha

    2013-01-01

    Natural Convection in Composite Fluid-Porous Domains provides a timely overview of the current state of understanding on the phenomenon of convection in composite fluid-porous layers. Natural convection in horizontal fluid-porous layers has received renewed attention because of engineering problems such as post-accident cooling of nuclear reactors, contaminant transport in groundwater, and convection in fibrous insulation systems. Because applications of the problem span many scientific domains, the book serves as a valuable resource for a wide audience.

  7. Thermal convection thresholds in a Oldroyd magnetic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Perez, L.M. [Departamento de Ingenieria Metalurgica, Universidad de Santiago de Chile, Av. Bernardo OHiggins 3363, Santiago (Chile); Bragard, J. [Departamento de Fisica y Matematica Aplicada, Universidad de Navarra, 31080 Pamplona (Spain); Laroze, D., E-mail: david.laroze@gmail.co [Max Planck Institute for Polymer Research, D 55021 Mainz (Germany); Instituto de Alta Investigacion, Universidad de Tarapaca, Casilla 7D, Arica (Chile); Martinez-Mardones, J. [Instituto de Fisica, Pontificia Universidad Catolica de Valparaiso, Casilla 4059, Valparaiso (Chile); Pleiner, H. [Max Planck Institute for Polymer Research, D 55021 Mainz (Germany)

    2011-03-15

    We report theoretical and numerical results on convection for a magnetic fluid in a viscoelastic carrier liquid. The viscoelastic properties is given by the Oldroyd model. We obtain explicit expressions for the convective thresholds in terms of the parameters of the system in the case of idealized boundary conditions. We also calculate numerically the convective thresholds for the case of realistic boundary conditions. The effect of the Kelvin force and of the rheology on instability thresholds for a diluted suspensions are emphasized. - Research highlights: > We study the linear analysis of the convection in magnetic fluids. > The Rheological properties are given by the Oldroyd model. > The numerical results are performed by the Spectral method.

  8. Inside the supernova: A powerful convective engine

    Science.gov (United States)

    Herant, Marc; Benz, Willy; Hix, W. Raphael; Fryer, Chris L.; Colgate, Stirling A.

    1994-01-01

    We present an extensive study of the inception of supernova explosions by following the evolution of the cores of two massive stars (15 and 25 Solar mass) in multidimension. Our calculations begin at the onset of core collapse and stop several hundred milliseconds after the bounce, at which time successful explosions of the appropriate magnitude have been obtained. Similar to the classical delayed explosion mechanism of Wilson, the explosion is powered by the heating of the envelope due to neutrinos emitted by the protoneutron star as it radiates the gravitational energy liberated by the collapse. However, as was shown by Herant, Benz, & Colgate, this heating generates strong convection outside the neutrinosphere, which we demonstrate to be critical to the explosion. By breaking a purely stratified hydrostatic equilibrium, convection moves the nascent supernova away from a delicate radiative equilibrium between neutrino emission and absorption, Thus, unlike what has been observed in one-dimensional calculations, explosions are rendered quite insensitive to the details of the physical input parameters such as neutrino cross sections or nuclear equation of state parameters. As a confirmation, our comparative one-dimensional calculations with identical microphysics, but in which convection cannot occur, lead to dramatic failures. Guided by our numerical results, we have developed a paradigm for the supernova explosion mechanism. We view a supernova as an open cycle thermodynamic engine in which a reservoir of low-entropy matter (the envelope) is thermally coupled and physically connected to a hot bath (the protoneutron star) by a neutrino flux, and by hydrodynamic instabilities. This paradigm does not invoke new or modified physics over previous treatments, but relies on compellingly straightforward thermodynamic arguments. It provides a robust and self-regulated explosion mechanism to power supernovae that is effective under a wide range of physical parameters.

  9. Effect of rotation on ferro thermohaline convection

    CERN Document Server

    Sekar, R; Ramanathan, A

    2000-01-01

    The ferro thermohaline convection in a rotating medium heated from below and salted from above has been analysed. The solute is magnetic oxide, which modifies the magnetic field established as a perturbation. The effect of salinity has been included in magnetisation and in the density of the ferrofluid. The conditions for both stationary and oscillatory modes have been obtained using linear stability analysis and it has been found that stationary mode is favoured in comparison with oscillatory mode. The numerical and graphical results are presented. It has been observed that rotation stabilises the system.

  10. Measurement of natural convection by speckle photography

    International Nuclear Information System (INIS)

    Wernekinck, U.; Merzkirch, W.

    1986-01-01

    The principle of speckle photography can be applied to the measurement of density variations in fluids. A modification of existing experimental arrangements allows for the measurement of large values of the light deflection angles as they may occur in heat and mass transfer situations. The method is demonstrated for the case of a helium jet exhausting into still air and the natural convective flow along a heated plate. The obtained data are compared with results measured with classical optical interferometers, and good agreement is found. The advantages of the new technique over the classical optical methods are briefly discussed. 11 references

  11. Coupled Michigan MHD - Rice Convection Model Results

    Science.gov (United States)

    de Zeeuw, D.; Sazykin, S.; Wolf, D.; Gombosi, T.; Powell, K.

    2002-12-01

    A new high performance Rice Convection Model (RCM) has been coupled to the adaptive-grid Michigan MHD model (BATSRUS). This fully coupled code allows us to self-consistently simulate the physics in the inner and middle magnetosphere. A study will be presented of the basic characteristics of the inner and middle magnetosphere in the context of a single coupled-code run for idealized storm inputs. The analysis will include region-2 currents, shielding of the inner magnetosphere, partial ring currents, pressure distribution, magnetic field inflation, and distribution of pV^gamma.

  12. Natural convection between two concentric spheres

    International Nuclear Information System (INIS)

    Blondel-Roux, Marie

    1983-01-01

    After an overview of researches on natural convection in a confined or semi-confined environment, this research thesis reports the use of the Caltagirone and Mojtabi numerical model and the study of its validity for different values of the Rayleigh and Prandtl numbers. Results obtained with this model are compared with experimental ones. Thermal transfer curves are presented and discussed, as well as the different temperature fields numerically obtained, flow function fields, velocities in the fluid layer, and temperature profiles with respect to the Rayleigh number [fr

  13. Hamiltonian Description of Convective-cell Generation

    International Nuclear Information System (INIS)

    Krommes, J.A.; Kolesnikov, R.A.

    2004-01-01

    The nonlinear statistical growth rate eq for convective cells driven by drift-wave (DW) interactions is studied with the aid of a covariant Hamiltonian formalism for the gyrofluid nonlinearities. A statistical energy theorem is proven that relates eq to a second functional tensor derivative of the DW energy. This generalizes to a wide class of systems of coupled partial differential equations a previous result for scalar dynamics. Applications to (i) electrostatic ion-temperature-gradient-driven modes at small ion temperature, and (ii) weakly electromagnetic collisional DW's are noted

  14. Three-dimensional mixed convection flow of viscoelastic fluid with thermal radiation and convective conditions.

    Science.gov (United States)

    Hayat, Tasawar; Ashraf, Muhammad Bilal; Alsulami, Hamed H; Alhuthali, Muhammad Shahab

    2014-01-01

    The objective of present research is to examine the thermal radiation effect in three-dimensional mixed convection flow of viscoelastic fluid. The boundary layer analysis has been discussed for flow by an exponentially stretching surface with convective conditions. The resulting partial differential equations are reduced into a system of nonlinear ordinary differential equations using appropriate transformations. The series solutions are developed through a modern technique known as the homotopy analysis method. The convergent expressions of velocity components and temperature are derived. The solutions obtained are dependent on seven sundry parameters including the viscoelastic parameter, mixed convection parameter, ratio parameter, temperature exponent, Prandtl number, Biot number and radiation parameter. A systematic study is performed to analyze the impacts of these influential parameters on the velocity and temperature, the skin friction coefficients and the local Nusselt number. It is observed that mixed convection parameter in momentum and thermal boundary layers has opposite role. Thermal boundary layer is found to decrease when ratio parameter, Prandtl number and temperature exponent are increased. Local Nusselt number is increasing function of viscoelastic parameter and Biot number. Radiation parameter on the Nusselt number has opposite effects when compared with viscoelastic parameter.

  15. THE EFFECT OF SOLAR RADIATION ON AUTOMOBILE ENVIRONMENT THROUGH NATURAL CONVECTION AND MIXED CONVECTION

    Directory of Open Access Journals (Sweden)

    MD. FAISAL KADER

    2012-10-01

    Full Text Available In the present paper, the effect of solar radiation on automobiles has been studied by both experimentally and numerically. The numerical solution is done by an operation friendly and fast CFD code – SC/Tetra with a full scale model of a SM3 car and turbulence is modeled by the standard k-ε equation. Numerical analysis of the three-dimensional model predicts a detailed description of fluid flow and temperature distribution in the passenger compartment during both the natural convection due to the incoming solar radiation and mixed convection due to the flow from defrost nozzle and radiation. It can be seen that solar radiation is an important parameter to raise the compartment temperature above the ambient temperature during summer. During natural convection, the rate of heat transfer is fast at the initial period. In the mixed convection analyses, it is found that the temperature drops down to a comfortable range almost linearly at the initial stage. Experimental investigations are performed to determine the temperature contour on the windshield and the local temperature at a particular point for further validation of the numerical results.

  16. DYNAMICS OF TURBULENT CONVECTION AND CONVECTIVE OVERSHOOT IN A MODERATE-MASS STAR

    Energy Technology Data Exchange (ETDEWEB)

    Kitiashvili, I. N.; Mansour, N. N.; Wray, A. A. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Kosovichev, A. G., E-mail: irina.n.kitiashvili@nasa.gov [New Jersey Institute of Technology, Newark, NJ 07102 (United States)

    2016-04-10

    We present results of realistic three-dimensional (3D) radiative hydrodynamic simulations of the outer layers of a moderate-mass star (1.47 M {sub ⊙}), including the full convection zone, the overshoot region, and the top layers of the radiative zone. The simulation results show that the surface granulation has a broad range of scales, from 2 to 12 Mm, and that large granules are organized in well-defined clusters, consisting of several granules. Comparison of the mean structure profiles from 3D simulations with the corresponding one-dimensional (1D) standard stellar model shows an increase of the stellar radius by ∼800 km, as well as significant changes in the thermodynamic structure and turbulent properties of the ionization zones. Convective downdrafts in the intergranular lanes between granulation clusters reach speeds of more than 20 km s{sup −1}, penetrate through the whole convection zone, hit the radiative zone, and form an 8 Mm thick overshoot layer. Contrary to semi-empirical overshooting models, our results show that the 3D dynamic overshoot region consists of two layers: a nearly adiabatic extension of the convection zone and a deeper layer of enhanced subadiabatic stratification. This layer is formed because of heating caused by the braking of the overshooting convective plumes. This effect has to be taken into account in stellar modeling and the interpretation of asteroseismology data. In particular, we demonstrate that the deviations of the mean structure of the 3D model from the 1D standard model of the same mass and composition are qualitatively similar to the deviations for the Sun found by helioseismology.

  17. NASA Earth Exchange (NEX)

    Data.gov (United States)

    National Aeronautics and Space Administration — The NASA Earth Exchange (NEX) represents a new platform for the Earth science community that provides a mechanism for scientific collaboration and knowledge sharing....

  18. EarthKAM

    Data.gov (United States)

    National Aeronautics and Space Administration — Sponsored by NASA, EarthKAM (Earth Knowledge Acquired by Middle School Students) is an educational outreach program allowing middle school students to take pictures...

  19. Mechanisms initiating deep convection over complex terrain during COPS

    Directory of Open Access Journals (Sweden)

    Christoph Kottmeier

    2008-12-01

    Full Text Available Precipitating convection in a mountain region of moderate topography is investigated, with particular emphasis on its initiation in response to boundary-layer and mid- and upper-tropospheric forcing mechanisms. The data used in the study are from COPS (Convective and Orographically-induced Precipitation Study that took place in southwestern Germany and eastern France in the summer of 2007. It is found that the initiation of precipitating convection can be roughly classified as being due to either: (i surface heating and low-level flow convergence; (ii surface heating and moisture supply overcoming convective inhibition during latent and/or potential instability; or (iii mid-tropospheric dynamical processes due to mesoscale convergence lines and forced mean vertical motion. These phenomena have to be adequately represented in models in order to improve quantitative precipitation forecast. Selected COPS cases are analysed and classified into these initiation categories. Although only a subset of COPS data (mainly radiosondes, surface weather stations, radar and satellite data are used here, it is shown that convective systems are captured in considerable detail by sensor synergy. Convergence lines were observed by Doppler radar in the location where deep convection is triggered several hours later. The results suggest that in many situations, observations of the location and timing of convergence lines will facilitate the nowcasting of convection. Further on, forecasting of the initiation of convection is significantly complicated if advection of potentially convective air masses over changing terrain features plays a major role. The passage of a frontal structure over the Vosges - Rhine valley - Black Forest orography was accompanied by an intermediate suppression of convection over the wide Rhine valley. Further downstream, an intensification of convection was observed over the Black Forest due to differential surface heating, a convergence line

  20. Convective initiation in the vicinity of the subtropical Andes

    Science.gov (United States)

    Rasmussen, K. L.; Houze, R.

    2014-12-01

    Extreme convection tends to form in the vicinity of mountain ranges, and the Andes in subtropical South America help spawn some of the most intense convection in the world. An investigation of the most intense storms for 11 years of TRMM Precipitation Radar (PR) data shows a tendency for squall lines to initiate and develop in this region with the canonical leading convective line/trailing stratiform structure. The synoptic environment and structures of the extreme convection and MCSs in subtropical South America are similar to those found in other regions of the world, especially the United States. In subtropical South America, however, the topographical influence on the convective initiation and maintenance of the MCSs is unique. A capping inversion in the lee of the Andes is important in preventing premature triggering. The Andes and other mountainous terrain of Argentina focus deep convective initiation in a narrow region. Subsequent to initiation, the convection often evolves into propagating mesoscale convective systems similar to those seen over the Great Plains of the U. S. and produces damaging tornadoes, hail, and floods across a wide agricultural region. Numerical simulations conducted with the NCAR Weather Research and Forecasting (WRF) Model extend the observational analysis and provide an objective evaluation of storm initiation, terrain effects, and development mechanisms. The simulated mesoscale systems closely resemble the storm structures seen by the TRMM Precipitation Radar as well as the overall shape and character of the storms shown in GOES satellite data. A sensitivity experiment with different configurations of topography, including both decreasing and increasing the height of the Andes Mountains, provides insight into the significant influence of orography in focusing convective initiation in this region. Lee cyclogenesis and a strong low-level jet are modulated by the height of the Andes Mountains and directly affect the character

  1. Venusian Applications of 3D Convection Modeling

    Science.gov (United States)

    Bonaccorso, Timary Annie

    2011-01-01

    This study models mantle convection on Venus using the 'cubed sphere' code OEDIPUS, which models one-sixth of the planet in spherical geometry. We are attempting to balance internal heating, bottom mantle viscosity, and temperature difference across Venus' mantle, in order to create a realistic model that matches with current planetary observations. We also have begun to run both lower and upper mantle simulations to determine whether layered (as opposed to whole-mantle) convection might produce more efficient heat transfer, as well as to model coronae formation in the upper mantle. Upper mantle simulations are completed using OEDIPUS' Cartesian counterpart, JOCASTA. This summer's central question has been how to define a mantle plume. Traditionally, we have defined a hot plume the region with temperature at or above 40% of the difference between the maximum and horizontally averaged temperature, and a cold plume as the region with 40% of the difference between the minimum and average temperature. For less viscous cases (1020 Pa?s), the plumes generated by that definition lacked vigor, displaying buoyancies 1/100th of those found in previous, higher viscosity simulations (1021 Pa?s). As the mantle plumes with large buoyancy flux are most likely to produce topographic uplift and volcanism, the low viscosity cases' plumes may not produce observable deformation. In an effort to eliminate the smallest plumes, we experimented with different lower bound parameters and temperature percentages.

  2. Forced convection heat transfer in He II

    International Nuclear Information System (INIS)

    Kashani, A.

    1986-01-01

    An investigation of forced convection heat transfer in He II is conducted. The study includes both experimental and theoretical treatments of the problem. The experiment consists of a hydraulic pump and a copper flow tube, 3 mm in ID and 2m long. The system allows measurements of one-dimensional heat and mass transfer in He II. The heat transfer experiments are performed by applying heat at the midpoint along the length of the flow tube. Two modes of heat input are employed, i.e., step function heat input and square pulse heat input. The heat transfer results are discussed in terms of temperature distribution in the tube. The experimental temperature profiles are compared with numerical solutions of an analytical model developed from the He II energy equation. The bath temperature is set at three different values of 1.65, 1.80, and 1.95 K. The He II flow velocity is varied up to 90 cm/s. Pressure is monitored at each end of the flow tube, and the He II pressure drop is obtained for different flow velocities. Results indicate that He II heat transfer by forced convention is considerably higher than that by internal convection. The theoretical model is in close agreement with the experiment. He II pressure drop and friction factor are very similar to those of an ordinary fluid

  3. Thermal Convection on an Ablating Target

    Science.gov (United States)

    Mehmedagic, Igbal; Thangam, Siva

    2015-11-01

    Modeling and analysis of thermal convection of a metallic targets subject to radiative flux is of relevance to various manufacturing processes as well as for the development of protective shields. The present work involves the computational modeling of metallic targets subject to high heat fluxes that are both steady and pulsed. Modeling of the ablation and associated fluid dynamics when metallic surfaces are exposed to high intensity pulsed laser fluence at normal atmospheric conditions is considered. The incident energy from the laser is partly absorbed and partly reflected by the surface during ablation and subsequent vaporization of the convecting melt also participates in the radiative exchange. The energy distribution during the process between the bulk and vapor phase strongly depends on optical and thermodynamic properties of the irradiated material, radiation wavelength, and laser pulse intensity and duration. Computational findings based on effective representation and prediction of the heat transfer, melting and vaporization of the targeting material as well as plume formation and expansion are presented and discussed in the context of various ablation mechanisms, variable thermo-physical and optical properties, plume expansion and surface geometry. Funded in part by U. S. Army ARDEC, Picatinny Arsenal, NJ.

  4. Effect of Cervical Pessary on Spontaneous Preterm Birth in Women With Singleton Pregnancies and Short Cervical Length: A Randomized Clinical Trial.

    Science.gov (United States)

    Saccone, Gabriele; Maruotti, Giuseppe Maria; Giudicepietro, Antonia; Martinelli, Pasquale

    2017-12-19

    Spontaneous preterm birth is a major cause of perinatal morbidity and mortality. It is unclear if a cervical pessary can reduce the risk of spontaneous preterm delivery. To test whether in asymptomatic women with singleton pregnancies and no prior spontaneous preterm birth but with short cervical length on transvaginal ultrasound, use of a cervical pessary would reduce the rate of spontaneous preterm birth at less than 34 weeks of gestation. Parallel-group, nonblinded, randomized clinical trial conducted from March 1, 2016, to May 25, 2017, at a single center in Italy. Asymptomatic women with singleton gestations, no previous spontaneous preterm births, and cervical lengths of 25 mm or less at 18 weeks 0 days to 23 weeks 6 days of gestation were eligible. Patients were randomized 1:1 to receive either cervical pessary (n = 150) or no pessary (n = 150). The pessary was removed between 37 weeks 0 days and 37 weeks 6 days of gestation or earlier if clinically indicated. The control group received standard care. For cervical length of 20 mm or shorter, women in both groups were prescribed vaginal progesterone, 200 mg/d, until 36 weeks 6 days of gestation. No bed rest or activity restriction was recommended. The primary end point was spontaneous preterm birth at less than 34 weeks of gestation. Secondary outcomes were adverse events. Among 300 women who were randomized (mean age, 29 [SD, 6.3] years; mean gestational age, 22 [SD, 1.3] weeks), 100% completed the trial. The primary end point occurred in 11 women (7.3%) in the pessary group and 23 women (15.3%) in the control group (between-group difference, -8.0% [95% CI, -15.7% to -0.4]; relative risk, 0.48 [95% CI, 0.24-0.95]). During follow-up, the pessary group had a higher rate of increased or new vaginal discharge (86.7% vs 46.0%; between-group difference, +40.7% [95% CI, +30.1%-+50.3%]; relative risk, 1.88 [95% CI, 1.57-2.27]). Among women without prior spontaneous preterm birth who had asymptomatic

  5. The Earth’s mantle before convection: Effects of magma oceans and the Moon (Invited)

    Science.gov (United States)

    Elkins-Tanton, L. T.; Smrekar, S. E.; Tobie, G.

    2009-12-01

    Studies of magma oceans indicate that planets obtain a gravitationally stable, compositionally differentiated mantle following solidification. This stable mantle results primarily from iron-magnesium partitioning during solidification, producing progressively iron-enriched mantle phases as solidification proceeds. Near the end of solidification, the dense solids will overturn to a stable configuration. The resulting differentiated mantle is stable from compositional density gradients that are significant enough to suppress thermal convection for up to hundreds of millions of years or longer, a scenario that proceeds self-consistently from physical and chemical principals, but is in contradiction with a previous image of a hot, turbulently convecting earliest terrestrial mantle. The isotopic range found in Martian meteorites indicates that its mantle differentiated in the first tens of millions of years of the solar system and has not been thoroughly remixed since. The specific isotopic range found on Mars is consistent with formation in a magma ocean. Based on the isotopic compositions of magmas, the Earth’s mantle is well mixed in comparison with the mantle of Mars. If the terrestrial planets experienced partial or whole magma oceans and thus began with stable mantles, resisting the onset of thermal convection and subsequent remixing, then why is Earth’s mantle well mixed? Two processes predicted to occur on the Earth, but not on the smaller Mars, may explain the divergent evolutions of these bodies. Here we will present model calculations for these two processes. First, we hypothesize that in the brief period that the Moon was very close to the Earth, it may have tidally heated Earth’s interior sufficiently to overcome its initial compositionally stable mantle, initiate active convection, and set the stage for the well-mixed mantle sampled today. Mars, conversely, may have cooled significantly before thermal convection began, allowing the formation of a

  6. Exploiting the Temperature Dependence of Magnetic Susceptibility to Control Convection in Fundamental Studies of Solidification Phenomena

    Science.gov (United States)

    Seybert, C. D.; Evans, J. W.; Leslie, Fred; Jones, W. K., Jr.

    2000-01-01

    It is well known that convection is a dominant mass transport mechanism when materials are solidified on Earth's surface. This convection is caused by gradients in density (and therefore gravitational force) that are brought about by gradients in temperature, composition or both. Diffusion of solute is therefore dwarfed by convection and the study of fundamental parameters, such as dendrite tip shape and growth velocity in the absence of convection is nearly impossible. Significant experimental work has therefore been carried out in orbiting laboratories with the intent of minimizing convection by minimizing gravity. One of the best known experiments of this kind is the Isothermal Dendritic Growth Experiment (IDGE), supported by NASA. Naturally such experiments are costly and one objective of the present investigation is to develop an experimental method whereby convection can be- halted, in solidification and other experiments, on the surface. A second objective is to use the method to minimize convection resulting from the residual accelerations suffered by experiments in microgravity. The method to be used to minimize convection relies on the dependence of the magnetic susceptibility of a fluid on temperature or composition (whichever is driving convection). All materials experience a force when placed in a magnetic field gradient. The direction and magnitude of that force depend on the magnetic susceptibility of the material. Consequently the force will vary if the susceptibility varies with temperature or composition. With a magnetic field gradient in the right direction (typically upward) and of the right magnitude, this variation in the magnetic force can be made to exactly cancel the variation in the gravitational force. Expressed another way, normal buoyancy is exactly countered by a "magnetic buoyancy". To demonstrate the principle, a solution of MnC12 in water has been used. First the variation of the susceptibility of this paramagnetic solution with

  7. Solar wind effects on ionospheric convection: a review

    DEFF Research Database (Denmark)

    Lu, G.; Cowley, S.W.H.; Milan, S.E.

    2002-01-01

    ), and travelling convection vortices (TCVs). Furthermore, the large-scale ionospheric convection configuration has also demonstrated a strong correspondence to variations in the interplanetary medium and substorm activity. This report briefly discusses the progress made over the past decade in studies...

  8. Modelling of convection during solidification of metal and alloys

    Indian Academy of Sciences (India)

    The role of convection during solidification is studied with the help of a mathematical model. The effect of various mush models on convection and consequent macrosegregation is examined with the help of numerical simulations. The predicted macrosegregation profiles are compared with published experimental data.

  9. Plains Elevated Convection at Night (PECAN) Experiment Science Plan

    Energy Technology Data Exchange (ETDEWEB)

    Turner, D [National Oceanic and Atmospheric Administration; Parsons, D [NCAR; Geerts, B [Department of Atmospheric Science, University of Wyoming

    2015-03-01

    The Plains Elevated Convection at Night (PECAN) experiment is a large field campaign that is being supported by the National Science Foundation (NSF) with contributions from the National Oceanic and Atmospheric Administration (NOAA), the National Atmospheric and Space Administration (NASA), and the U.S. Department of Energy (DOE). The overarching goal of the PECAN experiment is to improve the understanding and simulation of the processes that initiate and maintain convection and convective precipitation at night over the central portion of the Great Plains region of the United States (Parsons et al. 2013). These goals are important because (1) a large fraction of the yearly precipitation in the Great Plains comes from nocturnal convection, (2) nocturnal convection in the Great Plains is most often decoupled from the ground and, thus, is forced by other phenomena aloft (e.g., propagating bores, frontal boundaries, low-level jets [LLJ], etc.), (3) there is a relative lack of understanding how these disturbances initiate and maintain nocturnal convection, and (4) this lack of understanding greatly hampers the ability of numerical weather and climate models to simulate nocturnal convection well. This leads to significant uncertainties in predicting the onset, location, frequency, and intensity of convective cloud systems and associated weather hazards over the Great Plains.

  10. Transition to geostrophic convection: the role of the boundary conditions

    NARCIS (Netherlands)

    Kunnen, R.P.J.; Ostilla-Monico, Rodolfo; van der Poel, Erwin; Verzicco, Roberto; Lohse, Detlef

    2016-01-01

    Rotating Rayleigh–Bénard convection, the flow in a rotating fluid layer heated from below and cooled from above, is used to analyse the transition to the geostrophic regime of thermal convection. In the geostrophic regime, which is of direct relevance to most geo- and astrophysical flows, the system

  11. Using naive Bayes classifier for classification of convective rainfall ...

    Indian Academy of Sciences (India)

    convective clouds using SEVIRI data. 1. Introduction ... needed to sup- port convective rain generation with the so-called ... Data and methods. 2.1 Satellite and radar data. The dataset used in this study is MSG/SEVIRI data and corresponding ground-based radar data. Aiming to achieve comparability of these types of data ...

  12. Temperature-dependent viscosity effects on free convection flow ...

    African Journals Online (AJOL)

    Temperature-dependent viscosity effects on free convection flow over a vertical moving cylinder with constant axial velocity under consideration of radial ... Prandtl number, viscosity-variation parameter, thermal conductivity-variation parameter and magnetic parameter on free convection flow and heat transfer is discussed.

  13. Free Convective Flow of a Reacting Fluid between Vertical Porous ...

    African Journals Online (AJOL)

    Free Convective Flow of a Reacting Fluid between Vertical Porous Plates. ... written in dimensionless forms. The resulting second order equations are solved to obtain expressions for the velocity, temperature, mass transfer skin friction, and rate of heat transfer. Keywords: Convective flow, reacting fluid, vertical porous plates ...

  14. Link between convection and meridional gradient of sea surface ...

    Indian Academy of Sciences (India)

    A sensitivity analysis showed that the corresponding threshold for was 29°C. We hypothesise that the excess heating (∼1° C above the threshold for deep convection)required in the northern bay to trigger convection is because this excess in SST is what is required to establish the critical SST gradient.

  15. Dielectrophoretic Rayleigh-Bénard convection under microgravity conditions.

    Science.gov (United States)

    Yoshikawa, H N; Tadie Fogaing, M; Crumeyrolle, O; Mutabazi, I

    2013-04-01

    Thermal convection in a dielectric fluid layer between two parallel plates subjected to an alternating electric field and a temperature gradient is investigated under microgravity conditions. A thermoelectric coupling resulting from the thermal variation of the electric permittivity of the fluid produces the dielectrophoretic (DEP) body force, which can be regarded as thermal buoyancy due to an effective gravity. This electric gravity can destabilize a stationary conductive state of the fluid to develop convection. The similarity of the DEP thermal convection with the Rayleigh-Bénard (RB) convection is examined by considering its behavior in detail by a linear stability theory and a two-dimensional direct numerical simulation. The results are analyzed from an energetic viewpoint and in the framework of the Ginzburg-Landau (GL) equation. The stabilizing effects of a thermoelectric feedback make the critical parameters different from those in the RB instability. The nonuniformity of the electric gravity arising from the finite variation of permittivity also affects the critical parameters. The characteristic constants of the GL equation are comparable with those for the RB convection. The heat transfer in the DEP convection is weaker than in the RB convection as a consequence of the feedback that impedes the convection.

  16. Heat removal by natural convection in a RPR reactor

    International Nuclear Information System (INIS)

    Sampaio, P.A.B. de

    1987-01-01

    In this paper natural convection in RPR reactor is analysed. The effect of natural convection valves size on cladding temperature is studied. The reactor channel heat transfer problem is solved using finite elements in a two-dimensional analysis. Results show that two valves with Φ = 0.16 m are suited to keep coolant and cladding temperatures below 73 0 C. (author) [pt

  17. Convection diagnosis and nowcasting for oceanic aviation applications

    Science.gov (United States)

    Kessinger, Cathy; Donovan, Michael; Bankert, Richard; Williams, Earle; Hawkins, Jeffrey; Cai, Huaqing; Rehak, Nancy; Megenhardt, Daniel; Steiner, Matthias

    2008-08-01

    An oceanic convection diagnosis and nowcasting system is described whose domain of interest is the region between the southern continental United States and the northern extent of South America. In this system, geostationary satellite imagery are used to define the locations of deep convective clouds through the weighted combination of three independent algorithms. The resultant output, called the Convective Diagnosis Oceanic (CDO) product, is independently validated against space-borne radar and lighting products from the Tropical Rainfall Measuring Mission (TRMM) satellite to ascertain the ability of the CDO to discriminate hazardous convection. The CDO performed well in this preliminary investigation with some limitations noted. Short-term, 1-hr and 2-hr nowcasts of convection location are performed within the Convective Nowcasting Oceanic (CNO) system using a storm tracker. The CNO was found to have good statistical performance at extrapolating existing storm positions. Current work includes the development and implementation of additional atmospheric features for nowcasting convection initiation and to improve nowcasting of mature convection evolution.

  18. Efficiency of Heat Transfer in Turbulent Rayleigh-Benard Convection

    Czech Academy of Sciences Publication Activity Database

    Urban, Pavel; Musilová, Věra; Skrbek, L.

    2011-01-01

    Roč. 107, č. 1 (2011), 014302:1-4 ISSN 0031-9007 R&D Projects: GA AV ČR KJB200650902 Institutional research plan: CEZ:AV0Z20650511 Keywords : natural convection * thermal convection Subject RIV: BK - Fluid Dynamics Impact factor: 7.370, year: 2011

  19. The Role of Fingering Convection in Accreting Hydrogen-rich White Dwarfs: the Case of GD 133 and G 29-38

    Science.gov (United States)

    Wachlin, F. C.; Vauclair, S.; Vauclair, G.; Althaus, L. G.

    2017-03-01

    The accretion of heavy material from debris disk on the surface of hydrogen-rich white dwarfs induces a double-diffusivity instability known as the fingering (thermohaline) convection. It leads to an efficient extra mixing which brings the accreted material deeper in the star than by considering only mixing in the surface dynamical convection zone, in a time scale much shorter than that of gravitational settling. We performed numerical simulations of a continuous accretion of heavy material having a bulk Earth composition on the two well studied DAZ and ZZ Ceti pulsators GD 133 and G 29-38. We find that the existence of fingering convection implies much larger accretion rates to explain the observed abundances than previous estimates based on the standard mixing length theory and gravitational settling only.

  20. Mission to Planet Earth

    Science.gov (United States)

    Tilford, Shelby G.; Asrar, Ghassem; Backlund, Peter W.

    1994-01-01

    Mission to Planet Earth (MTPE) is NASA's concept for an international science program to produce the understanding needed to predict changes in the Earth's environment. NASA and its interagency and international partners will place satellites carrying advanced sensors in strategic Earth orbits to gather multidisciplinary data. A sophisticated data system will process and archive an unprecedented amount of information about the Earth and how it works as a system. Increased understanding of the Earth system is a basic human responsibility, a prerequisite to informed management of the planet's resources and to the preservation of the global environment.

  1. Mission to Planet Earth

    International Nuclear Information System (INIS)

    Wilson, G.S.; Backlund, P.W.

    1992-01-01

    Mission to Planet Earth (MTPE) is NASA's concept for an international science program to produce the understanding needed to predict changes in the earth's environment. NASA and its interagency and international partners will place satellites carrying advanced sensors in strategic earth orbits to gather multidisciplinary data. A sophisticated data system will process and archive an unprecedented amount of information about the earth and how it works as a system. Increased understanding of the earth system is a basic human responsibility, a prerequisite to informed management of the planet's resources and to the preservation of the global environment. 8 refs

  2. Stratiform Precipitation in Regions of Convection: A Meteorological Paradox?.

    Science.gov (United States)

    Houze, Robert A., Jr.

    1997-10-01

    It was once generally thought that stratiform precipitation was something occurring primarily, if not exclusively, in middle latitudes-in baroclinic cyclones and fronts. Early radar observations in the Tropics, however, showed large radar echoes composed of convective rain alongside stratiform precipitation, with the stratiform echoes covering great areas and accounting for a large portion of the tropical rainfall. These observations seemed paradoxical, since stratiform precipitation should not have been occurring in the Tropics, where baroclinic cyclones do not occur. Instead it was falling from convection-generated clouds, generally thought to be too violent to be compatible with the layered, gently settling behavior of stratiform precipitation.In meteorology, convection is a dynamic concept; specifically, it is the rapid, efficient, vigorous overturning of the atmosphere required to neutralize an unstable vertical distribution of moist static energy. Most clouds in the Tropics are convection-generated cumulonimbus. These cumulonimbus clouds contain an evolving pattern of newer and older precipitation. The young portions of the cumulonimbus are too violent to produce stratiform precipitation. In young, vigorous convective regions of the cumulonimbus, precipitation particles increase their mass by collection of cloud water, and the particles fall out in heavy showers, which appear on radar as vertically oriented convective "cells." In regions of older convection, however, the vertical air motions are generally weaker, and the precipitation particles drift downward, with the particles increasing their mass by vapor diffusion. In these regions the radar echoes are stratiform, and typically these echoes occur adjacent to regions of younger convective showers. Thus, the stratiform and convective precipitation both occur within the same complex of convection-generated cumulonimbus cloud.The feedbacks of the apparent heat source and moisture sink of tropical

  3. Numerical Modeling of Deep Mantle Flow: Thermochemical Convection and Entrainment

    Science.gov (United States)

    Mulyukova, Elvira; Steinberger, Bernhard; Dabrowski, Marcin; Sobolev, Stephan

    2013-04-01

    One of the most robust results from tomographic studies is the existence of two antipodally located Large Low Shear Velocity Provinces (LLSVPs) at the base of the mantle, which appear to be chemically denser than the ambient mantle. Results from reconstruction studies (Torsvik et al., 2006) infer that the LLSVPs are stable, long-lived, and are sampled by deep mantle plumes that rise predominantly from their margins. The origin of the dense material is debated, but generally falls within three categories: (i) a primitive layer that formed during magma ocean crystallization, (ii) accumulation of a dense eclogitic component from the recycled oceanic crust, and (iii) outer core material leaking into the lower mantle. A dense layer underlying a less dense ambient mantle is gravitationally stable. However, the flow due to thermal density variations, i.e. hot rising plumes and cold downwelling slabs, may deform the layer into piles with higher topography. Further deformation may lead to entrainment of the dense layer, its mixing with the ambient material, and even complete homogenisation with the rest of the mantle. The amount of the anomalous LLSVP-material that gets entrained into the rising plumes poses a constraint on the survival time of the LLSVPs, as well as on the plume buoyancy, on the lithospheric uplift associated with plume interaction and geochemical signature of the erupted lavas observed at the Earth's surface. Recent estimates for the plume responsible for the formation of the Siberian Flood Basalts give about 15% of entrained dense recycled oceanic crust, which made the hot mantle plume almost neutrally buoyant (Sobolev et al., 2011). In this numerical study we investigate the mechanics of entrainment of a dense basal layer by convective mantle flow. We observe that the types of flow that promote entrainment of the dense layer are (i) upwelling of the dense layer when it gets heated enough to overcome its stabilizing chemical density anomaly, (ii

  4. Heat transfer of laminar mixed convection of liquid

    CERN Document Server

    Shang, De-Yi

    2016-01-01

    This book presents a new algorithm to calculate fluid flow and heat transfer of laminar mixed convection. It provides step-by-step tutorial help to learn quickly how to set up the theoretical and numerical models of laminar mixed convection, to consider the variable physical properties of fluids, to obtain the system of numerical solutions, to create a series of formalization equations for the convection heat transfer by using a curve-fitting approach combined with theoretical analysis and derivation. It presents the governing ordinary differential equations of laminar mixed convection, equivalently transformed by an innovative similarity transformation with the description of the related transformation process. A system of numerical calculations of the governing ordinary differential equations is presented for the water laminar mixed convection. A polynomial model is induced for convenient and reliable treatment of variable physical properties of liquids. The developed formalization equations of mixed convec...

  5. Estimating Bulk Entrainment With Unaggregated and Aggregated Convection

    Science.gov (United States)

    Becker, Tobias; Bretherton, Christopher S.; Hohenegger, Cathy; Stevens, Bjorn

    2018-01-01

    To investigate how entrainment is influenced by convective organization, we use the ICON (ICOsahedral Nonhydrostatic) model in a radiative-convective equilibrium framework, with a 1 km spatial grid mesh covering a 600 by 520 km2 domain. We analyze two simulations, with unaggregated and aggregated convection, and find that, in the lower free troposphere, the bulk entrainment rate increases when convection aggregates. The increase of entrainment rate with aggregation is caused by a strong increase of turbulence in the close environment of updrafts, masking other effects like the increase of updraft size and of static stability with aggregation. Even though entrainment rate increases with aggregation, updraft buoyancy reduction through entrainment decreases because aggregated updrafts are protected by a moist shell. Parameterizations that wish to represent mesoscale convective organization would need to model this moist shell.

  6. Neutral beam injection and plasma convection in a magnetic field

    International Nuclear Information System (INIS)

    Okuda, H.; Hiroe, S.

    1988-06-01

    Injection of a neutral beam into a plasma in a magnetic field has been studied by means of numerical plasma simulations. It is found that, in the absence of a rotational transform, the convection electric field arising from the polarization charges at the edges of the beam is dissipated by turbulent plasma convection, leading to anomalous plasma diffusion across the magnetic field. The convection electric field increases with the beam density and beam energy. In the presence of a rotational transform, polarization charges can be neutralized by the electron motion along the magnetic field. Even in the presence of a rotational transform, a steady-state convection electric field and, hence, anomalous plasma diffusion can develop when a neutral beam is constantly injected into a plasma. Theoretical investigations on the convection electric field are described for a plasma in the presence of rotational transform. 11 refs., 19 figs

  7. The influence of convective current generator on the global current

    Directory of Open Access Journals (Sweden)

    V. N. Morozov

    2006-01-01

    Full Text Available The mathematical generalization of classical model of the global circuit with taking into account the convective current generator, working in the planetary boundary layer was considered. Convective current generator may be interpreted as generator, in which the electromotive force is generated by processes, of the turbulent transport of electrical charge. It is shown that the average potential of ionosphere is defined not only by the thunderstorm current generators, working at the present moment, but by the convective current generator also. The influence of the convective processes in the boundary layer on the electrical parameters of the atmosphere is not only local, but has global character as well. The numerical estimations, made for the case of the convective-unstable boundary layer demonstrate that the increase of the average potential of ionosphere may be of the order of 10% to 40%.

  8. Convection and segregation in a flat rotating sandbox

    Science.gov (United States)

    Rietz, Frank; Stannarius, Ralf

    2012-01-01

    A flat box, almost completely filled with a mixture of granulate, is rotated slowly about its horizontal central axis. In this experiment, a regular vortex flow of the granular material is observed in the cell plane. These vortex structures have a superficial analogy to convection rolls in dissipative structures of ordinary liquids. Whereas in the latter, the origin of the convection can often be attributed to gradients e.g. of densities or surface tensions, there is no trivial explanation at present for the convection of the granulate in the rotating container. Despite the simplicity of the experiment, the underlying mechanisms for convection and segregation are difficult to extract. Here, we present a comprehensive experimental study of the patterns under various experimental conditions and propose a mechanism for the convection.

  9. Patterns of granular convection and separation in narrow vibration bed

    Science.gov (United States)

    Liu, Chuanping; Wu, Ping; Wang, Li; Tong, Lige; Yin, Shaowu

    2017-06-01

    Granular convection/separation of single and binary component particles are studied in a narrow vibration bed, respectively. With filling the single light particles (molecular sieve beads), the bed exhibits five different states successively by increasing the vibration frequency f from 15Hz to 70 Hz (vibration strength Γ>3), as the global convection, symmetrical heap, unsymmetrical heap, local convection and pseudo solid. Comparatively, the granular bed of the single heavy particles (steel beads) is only in pseudo solid state at the above vibration condition. By filling binary component particles (molecular sieve and same size steel beads) instead of the single component, the bed shows similar convection state with that of the single molecular sieve beads, and the heavy steel beads are aggregated in the centre of convention roll as a core. Varying the initial distribution of binary component particles, the final convection and separation are not influenced, although the aggregation process of steel beads changes.

  10. [Impact of prepregnancy body mass index on pregnancy outcome in women with a singleton conceived by assisted reproductive technology and spontaneously conceived pregnancy: a case-control study].

    Science.gov (United States)

    Kim, Ju Hee; Shin, Hye Sook; Park, Bo Kyung; Yang, Kwang Moon; Lee, Young Ho; Ryu, Hyun Mee

    2012-08-01

    To compare and confirm the impact of prepregnancy body mass index on pregnancy outcome in women with a singleton conceived by assisted reproductive technology and spontaneously conceived pregnancy. A sample of 165 and 247 pregnant women with and without assisted reproductive technology were retrospectively recruited from electronic medical charts of C hospital. There were significant differences between the two groups for maternal age, paternal age, length of marriage, prepregnancy body mass index, parity, spontaneous abortion experience, and preterm delivery. A prepregnancy body mass index of ≥25 was associated with higher risk for maternal and neonatal complication in the assisted reproductive technology group. The results indicate that a higher prepregnancy body mass index is associated with increased risks for adverse pregnancy outcomes for women using assisted reproductive technology. So these women need appropriate care to compensate for the risk.

  11. A Study of Nucleate Boiling with Forced Convection in Microgravity

    Science.gov (United States)

    Merte, Herman, Jr.

    1999-01-01

    The ultimate objective of basic studies of flow boiling in microgravity is to improve the understanding of the processes involved, as manifested by the ability to predict its behavior. This is not yet the case for boiling heat transfer even in earth gravity, despite the considerable research activity over the past 30 years. The elements that constitute the nucleate boiling process - nucleation, growth, motion, and collapse of the vapor bubbles (if the bulk liquid is subcooled) - are common to both pool and flow boiling. It is well known that the imposition of bulk liquid motion affects the vapor bubble behavior relative to pool boiling, but does not appear to significantly influence the heat transfer. Indeed, it has been recommended in the past that empirical correlations or experimental data of pool boiling be used for design purposes with forced convection nucleate boiling. It is anticipated that such will most certainly not be possible for boiling in microgravity, based on observations made with pool boiling in microgravity. In earth gravity buoyancy will act to remove the vapor bubbles from the vicinity of the heater surface regardless of how much the imposed bulk velocity is reduced, depending, of course, on the geometry of the system. Vapor bubbles have been observed to dramatically increase in size in pool boiling in microgravity, and the heat flux at which dryout took place was reduced considerably below what is generally termed the critical heat flux (CHF) in earth gravity, depending on the bulk liquid subcooling. However, at heat flux levels below dryout, the nucleate pool boiling process was enhanced considerably over that in earth gravity, in spite of the large vapor bubbles formed in microgravity and perhaps as a consequence. These large vapor bubbles tended to remain in the vicinity of the heater surface, and the enhanced heat transfer appeared to be associated with the presence of what variously has been referred to as a liquid microlayer between the

  12. Dynamics of mixed convective-stably-stratified fluids

    Science.gov (United States)

    Couston, L.-A.; Lecoanet, D.; Favier, B.; Le Bars, M.

    2017-09-01

    We study the dynamical regimes of a density-stratified fluid confined between isothermal no-slip top and bottom boundaries (at temperatures Tt and Tb) via direct numerical simulation. The thermal expansion coefficient of the fluid is temperature dependent and chosen such that the fluid density is maximum at the inversion temperature Tb>Ti>Tt . Thus, the lower layer of the fluid is convectively unstable while the upper layer is stably stratified. We show that the characteristics of the convection change significantly depending on the degree of stratification of the stable layer. For strong stable stratification, the convection zone coincides with the fraction of the fluid that is convectively unstable (i.e., where T >Ti ), and convective motions consist of rising and sinking plumes of large density anomaly, as is the case in canonical Rayleigh-Bénard convection; internal gravity waves are generated by turbulent fluctuations in the convective layer and propagate in the upper layer. For weak stable stratification, we demonstrate that a large fraction of the stable fluid (i.e., with temperature T phenomenological description of the transition between the regimes of plume-dominated and entrainment-dominated convection through analysis of the differences in the heat transfer mechanisms, kinetic energy density spectra, and probability density functions for different stratification strengths. Importantly, we find that the effect of the stable layer on the convection decreases only weakly with increasing stratification strength, meaning that the dynamics of the stable layer and convection should be studied self-consistently in a wide range of applications.

  13. High resolution geodynamo simulations with strongly-driven convection and low viscosity

    Science.gov (United States)

    Schaeffer, Nathanael; Fournier, Alexandre; Jault, Dominique; Aubert, Julien

    2015-04-01

    Numerical simulations have been successful at explaining the magnetic field of the Earth for 20 years. However, the regime in which these simulations operate is in many respect very far from what is expected in the Earth's core. By reviewing previous work, we find that it appears difficult to have both low viscosity (low magnetic Prandtl number) and strong magnetic fields in numerical models (large ratio of magnetic over kinetic energy, a.k.a inverse squared Alfvén number). In order to understand better the dynamics and turbulence of the core, we have run a series of 3 simulations, with increasingly demanding parameters. The last simulation is at the limit of what nowadays codes can do on current super computers, with a resolution of 2688 grid points in longitude, 1344 in latitude, and 1024 radial levels. We will show various features of these numerical simulations, including what appears as trends when pushing the parameters toward the one of the Earth. The dynamics is very rich. From short time scales to large time scales, we observe at large scales: Inertial Waves, Torsional Alfvén Waves, columnar convective overturn dynamics and long-term thermal winds. In addition, the dynamics inside and outside the tangent cylinder seem to follow different routes. We find that the ohmic dissipation largely dominates the viscous one and that the magnetic energy dominates the kinetic energy. The magnetic field seems to play an ambiguous role. Despite the large magnetic field, which has an important impact on the flow, we find that the force balance for the mean flow is a thermal wind balance, and that the scale of convective cells is still dominated by viscous effects.

  14. Variable Azimuthal Anisotropy in Earth's Lowermost Mantle

    Science.gov (United States)

    Garnero, Edward J.; Maupin, Valérie; Lay, Thorne; Fouch, Matthew J.

    2004-10-01

    A persistent reversal in the expected polarity of the initiation of vertically polarized shear waves that graze the D'' layer (the layer at the boundary between the outer core and the lower mantle of Earth) in some regions starts at the arrival time of horizontally polarized shear waves. Full waveform modeling of the split shear waves for paths beneath the Caribbean requires azimuthal anisotropy at the base of the mantle. Models with laterally coherent patterns of transverse isotropy with the hexagonal symmetry axis of the mineral phases tilted from the vertical by as much as 20° are consistent with the data. Small-scale convection cells within the mantle above the D'' layer may cause the observed variations by inducing laterally variable crystallographic or shape-preferred orientation in minerals in the D'' layer.

  15. Stable isotope evidence for the Bottom Convective Layer homogeneity in the Black Sea.

    Science.gov (United States)

    Dubinin, Alexander V; Dubinina, Elena O; Demidova, Tatyana P; Kokryatskaya, Nataliya M; Rimskaya-Korsakova, Maria N; Kosova, Sofia A; Yakushev, Evgeniy V

    2014-01-01

    The Black Sea is the largest euxinic basin on the Earth. The anoxic zone consists of the upper part water mass stratified by density, and the lower water mass homogenized relative to density (depth >1750 m), named the Bottom Convective Layer. To assess homogeneity and possible exchange of matter across the upper and lower boundaries of the Bottom Convective Layer, new data on stable isotope composition of S, O and H were obtained. Samples were collected in August 2008 and March 2009 from two stations located in the eastern central part of the Black Sea. Distribution of δ(18)O and δD values of water for the entire water column did not vary seasonally. Appreciable differences were marked for δD value variation in the picnocline area (water depth 200-400 m) and in the BCL 5 m above the bottom that might be caused by penetration of intrusions with elevated portion of shelf modified Mediterranean Water. Observed linear relationship between δ(18)O (or δD) and salinity indicates that mixing water and salt occurs at the same time, and the deep water of the Black Sea has two end members: the high-salinity Mediterranean seawater and freshwater input. In the Bottom Convective Layer, the average δ(34)S (H2S) was -40.6 ± 0.5‰ and did not vary seasonally. At the bottom (depth > 2000 m), (34)S depletion down to -41.0‰ was observed. Our δ(34)S (SO4) data are by 2-3‰ higher than those measured previously for the Bottom Convective Layer. Sulfate from the aerobic zone with δ(34)S (SO4) = +21‰ corresponds to ocean water sulfate and that has not been subjected to sulfate reduction. Average δ(34)S (SO4) values for depths > 1250 m were found to be +23.0 ± 0.2‰ (1σ). Sulfur isotope composition of sulfate does not change in the Bottom Convective Layer and on its upper and lower boundaries, and does not depend on the season of observation.

  16. Mixed Convective Peristaltic Flow of Water Based Nanofluids with Joule Heating and Convective Boundary Conditions.

    Directory of Open Access Journals (Sweden)

    Tasawar Hayat

    Full Text Available Main objective of present study is to analyze the mixed convective peristaltic transport of water based nanofluids using five different nanoparticles i.e. (Al2O3, CuO, Cu, Ag and TiO2. Two thermal conductivity models namely the Maxwell's and Hamilton-Crosser's are used in this study. Hall and Joule heating effects are also given consideration. Convection boundary conditions are employed. Furthermore, viscous dissipation and heat generation/absorption are used to model the energy equation. Problem is simplified by employing lubrication approach. System of equations are solved numerically. Influence of pertinent parameters on the velocity and temperature are discussed. Also the heat transfer rate at the wall is observed for considered five nanofluids using the two phase models via graphs.

  17. MHD Natural Convection with Convective Surface Boundary Condition over a Flat Plate

    Directory of Open Access Journals (Sweden)

    Mohammad M. Rashidi

    2014-01-01

    Full Text Available We apply the one parameter continuous group method to investigate similarity solutions of magnetohydrodynamic (MHD heat and mass transfer flow of a steady viscous incompressible fluid over a flat plate. By using the one parameter group method, similarity transformations and corresponding similarity representations are presented. A convective boundary condition is applied instead of the usual boundary conditions of constant surface temperature or constant heat flux. In addition it is assumed that viscosity, thermal conductivity, and concentration diffusivity vary linearly. Our study indicates that a similarity solution is possible if the convective heat transfer related to the hot fluid on the lower surface of the plate is directly proportional to (x--1/2 where x- is the distance from the leading edge of the solid surface. Numerical solutions of the ordinary differential equations are obtained by the Keller Box method for different values of the controlling parameters associated with the problem.

  18. Convective towers detection using GPS radio occultations

    DEFF Research Database (Denmark)

    Biondi, Riccardo; Neubert, Torsten; Syndergaard, S.

    an important role since they lead to deep convective activity. With this work we want to investigate if severe storms leave a significant signature in radio occultation profiles in the tropical tropopause layer. The GPS radio occultation (RO) technique is useful for studying severe weather phenomena because...... the GPS signals penetrate through clouds and allow measurements of atmospheric profiles related to temperature, pressure, and water vapour with high vertical resolution. Using tropical cyclone best track database and data from different GPS RO missions (COSMIC, GRACE, CHAMP, SACC and GPSMET), we selected...... 1194 profiles in a time window of 3 hours and a space window of 300 km from the eye of the cyclone. We show that the bending angle anomaly of a GPS RO signal is typically larger than the climatology above the tropopause. Comparisons with co-located radiosondes, climatology of tropopause altitudes...

  19. Imaging convection and magnetism in the sun

    CERN Document Server

    Hanasoge, Shravan

    2015-01-01

    This book reviews the field of helioseismology and its outstanding challenges and also offers a detailed discussion of the latest computational methodologies. The focus is on the development and implementation of techniques to create 3-D images of convection and magnetism in the solar interior and to introduce the latest computational and theoretical methods to the interested reader. With the increasing availability of computational resources, demand for greater accuracy in the interpretation of helioseismic measurements and the advent of billion-dollar instruments taking high-quality observations, computational methods of helioseismology that enable probing the 3-D structure of the Sun have increasingly become central. This book will benefit students and researchers with proficiency in basic numerical methods, differential equations and linear algebra who are interested in helioseismology.

  20. Convection patterns in a spherical fluid shell

    Science.gov (United States)

    Feudel, F.; Bergemann, K.; Tuckerman, L. S.; Egbers, C.; Futterer, B.; Gellert, M.; Hollerbach, R.

    2011-04-01

    Symmetry-breaking bifurcations have been studied for convection in a nonrotating spherical shell whose outer radius is twice the inner radius, under the influence of an externally applied central force field with a radial dependence proportional to 1/r5. This work is motivated by the GeoFlow experiment, which is performed under microgravity condition at the International Space Station where this particular central force can be generated. In order to predict the observable patterns, simulations together with path-following techniques and stability computations have been applied. Branches of axisymmetric, octahedral, and seven-cell solutions have been traced. The bifurcations producing them have been identified and their stability ranges determined. At higher Rayleigh numbers, time-periodic states with a complex spatiotemporal symmetry are found, which we call breathing patterns.

  1. Design Aspects of the Rayleigh Convection Code

    Science.gov (United States)

    Featherstone, N. A.

    2017-12-01

    Understanding the long-term generation of planetary or stellar magnetic field requires complementary knowledge of the large-scale fluid dynamics pervading large fractions of the object's interior. Such large-scale motions are sensitive to the system's geometry which, in planets and stars, is spherical to a good approximation. As a result, computational models designed to study such systems often solve the MHD equations in spherical geometry, frequently employing a spectral approach involving spherical harmonics. We present computational and user-interface design aspects of one such modeling tool, the Rayleigh convection code, which is suitable for deployment on desktop and petascale-hpc architectures alike. In this poster, we will present an overview of this code's parallel design and its built-in diagnostics-output package. Rayleigh has been developed with NSF support through the Computational Infrastructure for Geodynamics and is expected to be released as open-source software in winter 2017/2018.

  2. Convection naturelle dans un milieu poreux multicouche

    OpenAIRE

    Ould-Amer, Yacine; Slama, Saoussène

    2007-01-01

    International audience; Dans la présente étude, nous nous sommes intéressés à la convection naturelle dans une cavité carrée poreuse multicouche. Chaque couche de milieu poreux (trois dans la présente étude) est considérée homogène, isotrope et saturée par un seul fluide. Cette enceinte est supposée être chauffée à des températures différentes le long des parois latérales, les deux autres sont isolés. Dans le but de généraliser les résultats, les équations gouvernantes sont mises sous forme a...

  3. Mixed convection in fluid superposed porous layers

    CERN Document Server

    Dixon, John M

    2017-01-01

    This Brief describes and analyzes flow and heat transport over a liquid-saturated porous bed. The porous bed is saturated by a liquid layer and heating takes place from a section of the bottom. The effect on flow patterns of heating from the bottom is shown by calculation, and when the heating is sufficiently strong, the flow is affected through the porous and upper liquid layers. Measurements of the heat transfer rate from the heated section confirm calculations. General heat transfer laws are developed for varying porous bed depths for applications to process industry needs, environmental sciences, and materials processing. Addressing a topic of considerable interest to the research community, the brief features an up-to-date literature review of mixed convection energy transport in fluid superposed porous layers.

  4. Prediction of flow instability during natural convection

    International Nuclear Information System (INIS)

    Farhadi, Kazem

    2005-01-01

    The occurrence of flow excursion instability during passive heat removal for Tehran Research Reactor (TRR) has been analyzed at low-pressure and low-mass rate of flow conditions without boiling taking place. Pressure drop-flow rate characteristics in the general case are determined upon a developed code for this purpose. The code takes into account variations of different pressure drop components caused by different powers as well as different core inlet temperatures. The analysis revealed the fact that the instability can actually occur in the natural convection mode for a range of powers per fuel plates at a predetermined inlet temperature with fixed geometry of the core. Low mass rate of flow and high sub-cooling are the two important conditions for the occurrence of static instability in the TRR. The calculated results are compared with the existing data in the literature. (author)

  5. The sensitivity of convective aggregation to diabatic processes in idealized radiative-convective equilibrium simulations

    Science.gov (United States)

    Holloway, C. E.; Woolnough, S. J.

    2016-03-01

    Idealized explicit convection simulations of the Met Office Unified Model exhibit spontaneous self-aggregation in radiative-convective equilibrium, as seen in other models in previous studies. This self-aggregation is linked to feedbacks between radiation, surface fluxes, and convection, and the organization is intimately related to the evolution of the column water vapor field. Analysis of the budget of the spatial variance of column-integrated frozen moist static energy (MSE), following Wing and Emanuel (2014), reveals that the direct radiative feedback (including significant cloud longwave effects) is dominant in both the initial development of self-aggregation and the maintenance of an aggregated state. A low-level circulation at intermediate stages of aggregation does appear to transport MSE from drier to moister regions, but this circulation is mostly balanced by other advective effects of opposite sign and is forced by horizontal anomalies of convective heating (not radiation). Sensitivity studies with either fixed prescribed radiative cooling, fixed prescribed surface fluxes, or both do not show full self-aggregation from homogeneous initial conditions, though fixed surface fluxes do not disaggregate an initialized aggregated state. A sensitivity study in which rain evaporation is turned off shows more rapid self-aggregation, while a run with this change plus fixed radiative cooling still shows strong self-aggregation, supporting a "moisture-memory" effect found in Muller and Bony (2015). Interestingly, self-aggregation occurs even in simulations with sea surface temperatures (SSTs) of 295 and 290 K, with direct radiative feedbacks dominating the budget of MSE variance, in contrast to results in some previous studies.

  6. Engineering photochemical smog through convection towers

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, S.; Prueitt, M.L.; Bossert, J.E.; Mroz, E.J.; Krakowski, R.A.; Miller, R.L. [Los Alamos National Lab., NM (United States); Jacobson, M.Z.; Turco, R.P. [Los Alamos National Lab., NM (United States)]|[Univ. of California, Los Angeles, CA (United States). Atmospheric Sciences Dept.

    1995-02-01

    Reverse convection towers have attracted attention as a medium for cleansing modern cities. Evaporation of an aqueous mist injected at the tower opening could generate electrical power by creating descent, and simultaneously scavenge unsightly and unhealthful particulates. The study offered here assesses the influence to tower water droplets on the photochemical component of Los Angeles type smog. The primary radical chain initiator OH is likely removed into aqueous phases well within the residence time of air in the tower, and then reacts away rapidly. Organics do not dissolve, but nighttime hydrolysis of N{sub 2}O{sub 5} depletes the nitrogen oxides. A lack of HOx would slow hydrocarbon oxidation and so also ozone production. Lowering of NOx would also alter ozone production rates, but the direction is uncertain. SO{sub 2} is available in sufficient quantities in some urban areas to react with stable oxidants, and if seawater were the source of the mist, the high pH would lead to fast sulfur oxidation kinetics. With an accommodation coefficient of 10{sup {minus}3}, however, ozone may not enter the aqueous phase efficiently. Even if ozone is destroyed or its production suppressed, photochemical recovery times are on the order of hours, so that tower processing must be centered on a narrow midday time window. The cost of building the number of structures necessary for this brief turnover could be prohibitive. The increase in humidity accompanying mist evaporation could be controlled with condensers, but might otherwise counteract visibility enhancements by recreating aqueous aerosols. Quantification of the divergent forcings convection towers must exert upon the cityscape would call for coupled three dimensional modeling of transport, microphysics, and photochemistry. 112 refs.

  7. Characteristics of Extreme Summer Convection over equatorial America and Africa

    Science.gov (United States)

    Zuluaga, M. D.; Houze, R.

    2013-12-01

    Fourteen years of Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) version 7 data for June-August show the temporal and spatial characteristics of extreme convection over equatorial regions of the American and African continents. We identify three types of extreme systems: storms with deep convective cores (contiguous convective 40 dBZ echoes extending ≥10 km in height), storms with wide convective cores (contiguous convective 40 dBZ echoes with areas >1,000 km2) and storms with broad stratiform regions (stratiform echo >50,000 km2). European Centre for Medium-Range Weather Forecast (ECMWF) reanalysis is used to describe the environmental conditions around these forms of extreme convection. Storms with deep convective cores occur mainly over land: in the equatorial Americas, maximum occurrence is in western Mexico, Northern Colombia and Venezuela; in Africa, the region of maximum occurrence is a broad zone enclosing the central and west Sudanian Savanna, south of the Sahel region. Storms with wide convective radar echoes occur in these same general locations. In the American sector, storms with broad stratiform precipitation regions (typifying robust mesoscale convective systems) occur mainly over the eastern tropical Pacific Ocean and the Colombia-Panama bight. In the African sector, storms with broad stratiform precipitation areas occur primarily over the eastern tropical Atlantic Ocean near the coast of West Africa. ECMWF reanalyses show how the regions of extreme deep convection associated with both continents are located mainly in regions affected by diurnal heating and influenced by atmospheric jets in regions with strong humidity gradients. Composite analysis of the synoptic conditions leading to the three forms of extreme convection provides insights into the forcing mechanisms in which these systems occur. These analyses show how the monsoonal flow directed towards the Andes slopes is mainly what concentrates the occurrence of extreme

  8. Diagnosing the average spatio-temporal impact of convective systems – Part 1: A methodology for evaluating climate models

    Directory of Open Access Journals (Sweden)

    M. S. Johnston

    2013-12-01

    Full Text Available An earlier method to determine the mean response of upper-tropospheric water to localised deep convective systems (DC systems is improved and applied to the EC-Earth climate model. Following Zelinka and Hartmann (2009, several fields related to moist processes and radiation from various satellites are composited with respect to the local maxima in rain rate to determine their spatio-temporal evolution with deep convection in the central Pacific Ocean. Major improvements to the earlier study are the isolation of DC systems in time so as to prevent multiple sampling of the same event, and a revised definition of the mean background state that allows for better characterisation of the DC-system-induced anomalies. The observed DC systems in this study propagate westward at ~4 m s−1. Both the upper-tropospheric relative humidity and the outgoing longwave radiation are substantially perturbed over a broad horizontal extent and for periods >30 h. The cloud fraction anomaly is fairly constant with height but small maximum can be seen around 200 hPa. The cloud ice water content anomaly is mostly confined to pressures greater than 150 hPa and reaches its maximum around 450 hPa, a few hours after the peak convection. Consistent with the large increase in upper-tropospheric cloud ice water content, albedo increases dramatically and persists about 30 h after peak convection. Applying the compositing technique to EC-Earth allows an assessment of the model representation of DC systems. The model captures the large-scale responses, most notably for outgoing longwave radiation, but there are a number of important differences. DC systems appear to propagate eastward in the model, suggesting a strong link to Kelvin waves instead of equatorial Rossby waves. The diurnal cycle in the model is more pronounced and appears to trigger new convection further to the west each time. Finally, the modelled ice water content anomaly peaks at pressures greater than 500 h

  9. Digital Earth – A sustainable Earth

    International Nuclear Information System (INIS)

    Mahavir

    2014-01-01

    All life, particularly human, cannot be sustainable, unless complimented with shelter, poverty reduction, provision of basic infrastructure and services, equal opportunities and social justice. Yet, in the context of cities, it is believed that they can accommodate more and more people, endlessly, regardless to their carrying capacity and increasing ecological footprint. The 'inclusion', for bringing more and more people in the purview of development is often limited to social and economic inclusion rather than spatial and ecological inclusion. Economic investment decisions are also not always supported with spatial planning decisions. Most planning for a sustainable Earth, be at a level of rural settlement, city, region, national or Global, fail on the capacity and capability fronts. In India, for example, out of some 8,000 towns and cities, Master Plans exist for only about 1,800. A chapter on sustainability or environment is neither statutorily compulsory nor a norm for these Master Plans. Geospatial technologies including Remote Sensing, GIS, Indian National Spatial Data Infrastructure (NSDI), Indian National Urban Information Systems (NUIS), Indian Environmental Information System (ENVIS), and Indian National GIS (NGIS), etc. have potential to map, analyse, visualize and take sustainable developmental decisions based on participatory social, economic and social inclusion. Sustainable Earth, at all scales, is a logical and natural outcome of a digitally mapped, conceived and planned Earth. Digital Earth, in fact, itself offers a platform to dovetail the ecological, social and economic considerations in transforming it into a sustainable Earth

  10. Shallow cumulus convection = Ondiepe cumulus convectie

    NARCIS (Netherlands)

    Neggers, R.

    2002-01-01

    Clouds play an important role in the earth's climate. Firstly, they are important in the radiative energy budget of the global atmosphere. Clouds absorb and reflect ultraviolet solar radiation, and emit infrared radiation depending on their temperature. Secondly, an

  11. The dynamic evolution of active-region-scale magnetic flux tubes in the turbulent solar convective envelope

    Science.gov (United States)

    Weber, Maria Ann

    2014-12-01

    The Sun exhibits cyclic properties of its large-scale magnetic field on the order of sigma22 years, with a ˜11 year frequency of sunspot occurrence. These sunspots, or active regions, are the centers of magnetically driven phenomena such as flares and coronal mass ejections. Volatile solar magnetic events directed toward the Earth pose a threat to human activities and our increasingly technological society. As such, the origin and nature of solar magnetic flux emergence is a topic of global concern. Sunspots are observable manifestations of solar magnetic fields, thus providing a photospheric link to the deep-seated dynamo mechanism. However, the manner by which bundles of magnetic field, or flux tubes, traverse the convection zone to eventual emergence at the solar surface is not well understood. To provide a connection between dynamo-generated magnetic fields and sunspots, I have performed simulations of magnetic flux emergence through the bulk of a turbulent, solar convective envelope by employing a thin flux tube model subject to interaction with flows taken from a hydrodynamic convection simulation computed through the Anelastic Spherical Harmonic (ASH) code. The convective velocity field interacts with the flux tube through the drag force it experiences as it traverses through the convecting medium. Through performing these simulations, much insight has been gained about the influence of turbulent solar-like convection on the flux emergence process and resulting active region properties. I find that the dynamic evolution of flux tubes change from convection dominated to magnetic buoyancy dominated as the initial field strength of the flux tubes increases from 15 kG to 100 kG. Additionally, active-region-scale flux tubes of 40 kG and greater exhibit properties similar to those of active regions on the Sun, such as: tilt angles, rotation rates, and morphological asymmetries. The joint effect of the Coriolis force and helical motions present in convective

  12. Nocturnal offshore convection near the island of Corsica

    Science.gov (United States)

    Barthlott, Christian; Adler, Bianca; Kalthoff, Norbert; Handwerker, Jan; Kohler, Martin; Wieser, Andreas

    2014-05-01

    In the region of Corsica, located in the western Mediterranean Sea, the mean daily lightning activity for late summer and autumn as an indicator for deep convection shows a distinct maximum in mid-afternoon and a secondary maximum in the night. During the night, most of the lightning activity is located offshore and near the island's coastline. Currently there are no observational data which could be used to explain this nocturnal offshore convection but understanding its formation mechanism is crucial for accurately forecasting the regional weather. In this work, we explore two possible mechanisms initiating nocturnal offshore convection: (i) convergence with subsequent lifting due to the interaction between drainage winds and the synoptic flow over the sea and (ii) dynamically induced lee-side convergence due to the island barrier effect. To this end, we perform numerical simulations with the Consortium for Small-scale Modeling (COSMO) model at a convection-resolving horizontal grid spacing of 2.8 km. The analysis of two cases with different low-level wind directions reveals that the role of the island's drainage flow can either favour or hinder the development of deep convection. Furthermore, convective initiation is very sensitive to terrain elevation and model initialisation time and small changes of these features can decide whether deep convection occurs or not.

  13. Thermodynamic Environments Supporting Extreme Convection in Subtropical South America

    Science.gov (United States)

    Rasmussen, K. L.; Trier, S. B.

    2015-12-01

    Extreme convection tends to form in the vicinity of mountain ranges, and the Andes in subtropical South America help spawn some of the most intense convection in the world. Subsequent to initiation, the convection often evolves into propagating mesoscale convective systems (MCSs) similar to those seen over the U.S. Great Plains and produces damaging tornadoes, hail, and floods across a wide agricultural region. In recent years, studies on the nature of convection in subtropical South America using spaceborne radar data have elucidated key processes responsible for their extreme characteristics, including a strong relationship between the Andes topography and convective initiation. Building on previous work, an investigation of the thermodynamic environment supporting some of the deepest convection in the world will be presented. In particular, an analysis of the thermodynamic destabilization in subtropical South America, which considers the parcel buoyancy minimum for conditionally unstable air parcels, will be presented. Additional comparisons between the nocturnal nature and related diurnal cycle of MCSs in subtropical South America the U.S. Great Plains will provide insights into the processes controlling MCS initiation and upscale growth.

  14. Convective effects in a regulatory and proposed fire model

    International Nuclear Information System (INIS)

    Wix, S.D.; Hohnstreiter, G.F.

    1995-01-01

    Radiation is the dominant mode of heat transfer in large fires. However, convection can be as much as 10 to 20 percent of the total heat transfer to an object in a large fire. The current radioactive material transportation packaging regulations include convection as a mode of heat transfer in the accident condition scenario. The current International Atomic Energy Agency Safety Series 6 packaging regulation states ''the convection coefficient shall be that value which the designer can justify if the package were exposed to the specified fire''. The current Title 10, Code of Federal Regulations, Part 71 (10CFR71) packaging regulation states ''when significant, convection heat input must be included on the basis of still, ambient air at 800 degrees C (1475 degrees F)''. Two questions that can arise in an analysts mind from an examination of the packaging regulations is whether convection is significant and whether convection should be included in the design analysis of a radioactive materials transportation container. The objective of this study is to examine the convective effects on an actual radioactive materials transportation package using a regulatory and a proposed thermal boundary condition

  15. Improved nowcasting of precipitation based on convective analysis fields

    Directory of Open Access Journals (Sweden)

    T. Haiden

    2007-04-01

    Full Text Available The high-resolution analysis and nowcasting system INCA (Integrated Nowcasting through Comprehensive Analysis developed at the Austrian national weather service provides three-dimensional fields of temperature, humidity, and wind on an hourly basis, and two-dimensional fields of precipitation rate in 15 min intervals. The system operates on a horizontal resolution of 1 km and a vertical resolution of 100–200 m. It combines surface station data, remote sensing data (radar, satellite, forecast fields of the numerical weather prediction model ALADIN, and high-resolution topographic data. An important application of the INCA system is nowcasting of convective precipitation. Based on fine-scale temperature, humidity, and wind analyses a number of convective analysis fields are routinely generated. These fields include convective boundary layer (CBL flow convergence and specific humidity, lifted condensation level (LCL, convective available potential energy (CAPE, convective inhibition (CIN, and various convective stability indices. Based on the verification of areal precipitation nowcasts it is shown that the pure translational forecast of convective cells can be improved by using a decision algorithm which is based on a subset of the above fields, combined with satellite products.

  16. Earth tides of an ellipsoidal, inelastic, and laterally heterogeneous Earth

    Science.gov (United States)

    Kim, T.; Shibuya, K.

    2012-12-01

    We used five stations covering a range of latitudes from 60°N to 70°S: METSÄHOVI, STRASBOURG, SUTHERLAND, CANBERRA, and SYOWA with Superconducting Gravimeter with sufficiently high-resolution data available for durations of at least five years to validate theoretical estimation based on an existing method. For the Earth model, we selected the model of Dehant et al. (1999) to validate the latitude dependency and inelasticity of gravimetric factor. We also used the model of Métivier and Conrad (2008) to validate the lateral heterogeneity of gravity observation. For the correction of ocean loading effect, we tested recent four global ocean tide models (TPXO7-atlas, EOT11a, DTU10, and HAMTIDE11a) as well as old ocean tide models. We estimated the misfit between the observed loading effect and the modeled ocean loading effect for the three main waves (O1, K1, and M2) at each station. Anomalous discrepancies at METSÄHOVI and SYOWA based on old ocean tide models were diminished by the use of recent ocean tide models. Gravimetric factors for K1, corrected using optimum recent ocean tide models, showed the possibility of obtaining parameters conforming to the prediction curve of model of inelastic non-hydrostatic Earth. Gravimetric factors corrected using optimum ocean tide models at METSÄHOVI, STRASBOURG, and CANBERRA showed tendencies towards the theoretical values for latitude dependence. However, at SUTHERLAND and SYOWA, large offsets from theoretical values were observed. These stations show the remaining misfits, 0.0733 and 0.0847 microGal, respectively. We think the portion of the anomaly could not be explained by the perturbation from the mantle convection, because the amplitude of gravity perturbation at these stations is very small. For example, at SUTHERLAND, the final residual for K1 band is 85 nanoGal but gravity perturbation by lateral heterogeneity is just ~0.81 nanoGal: Gravity perturbations up to 120 nanoGal for all bands come from mostly in Indonesia

  17. Numerical simulations of thermo-compositional global convection with generation of proto-continental crust

    Science.gov (United States)

    Rozel, A. B.; Golabek, G.; Gerya, T.; Jain, C.; Tackley, P. J.

    2017-12-01

    We study the creation of primordial continental crust (TTG rocks) employing fully self-consistent numerical models of thermo-chemical convection on a global scale at the Archean. We use realistic rheological parameters [1] in 2D spherical annulus geometry using the convection code StagYY [2] for a one billion years period. Starting from a pyrolytic composition and an initially warm core, our simulations first generate mafic crust and depleted mantle in the upper mantle. The basaltic material can be both erupted (cold) and/or intruded (warm) at the base of the crust following a predefined partitioning. At all times, water concentration is considered fully saturated in the top 10 km of the domain, and it simply advected with the deforming material elsewhere. We track the pressure-temperature conditions of the newly formed hydrated basalt and check if it matches the conditions necessary for the formation of proto-continental crust [3]. We systematically test the influence of volcanism (eruption, also called "heat pipe") and plutonism (intrusive magmatism) on the time-dependent geotherm in the lithosphere. We show that the "heat-pipe" model (assuming 100% eruption) suggested to be the main heat loss mechanism during the Archean epoch [4] is not able to produce continental crust since it forms a too cold lithosphere. We also systematically test various friction coefficients and show that an intrusion fraction higher than 60% (in agreement with [5]) combined with a friction coefficient larger than 0.1 produces the expected amount of the three main petrological TTG compositions previously reported [3]. This result seems robust as the amount of TTG rocks formed vary over orders of magnitude. A large eruption over intrusion ratio can result in up to 100 times less TTG felsic crust production than a case where plutonism dominates. This study represents a major step towards the production of self-consistent convection models able to generate the continental crust of the Earth

  18. Single-mode theory of diffusive layers in thermohaline convection

    Science.gov (United States)

    Gough, D. O.; Toomre, J.

    1982-01-01

    A two-layer configuration of thermohaline convection is studied, with the principal aim of explaining the observed independence of the buoyancy-flux ratio on the stability parameter when the latter is large. Temperature is destabilizing and salinity is stabilizing, so diffusive interfaces separate the convecting layers. The convection is treated in the single-mode approximation, with a prescribed horizontal planform and wavenumber. Surveys of numerical solutions are presented for a selection of Rayleigh numbers R, stability parameters lambda and horizontal wavenumbers. The solutions yield a buoyancy flux ratio chi that is insensitive to lambda, in accord with laboratory experiments. However chi increases with increasing R, in contradiction to laboratory observations.

  19. Analysis of forced convection heat transfer to supercritical carbon dioxide

    International Nuclear Information System (INIS)

    Ko, H.S.; Sakurai, Katsumi; Okamoto, Koji; Madarame, Haruki

    2000-01-01

    The supercritical carbon dioxide flow has been visualized under forced convection by a Mach-Zehnder interferometry system. The forced convection heat transfer has been examined by an one-sided wall heater in the vertical rectangular test section. Temperature and density distributions of the heated carbon dioxide inside the test section have been calculated from the measured interferometry projections for the visible interferograms conditions. The relationship of the temperature distributions with the physical conditions has been analyzed to inspect the forced convection heat transfer of the supercritical carbon dioxide flow. (author)

  20. Confinement and dynamical regulation in two-dimensional convective turbulence

    DEFF Research Database (Denmark)

    Bian, N.H.; Garcia, O.E.

    2003-01-01

    In this work the nature of confinement improvement implied by the self-consistent generation of mean flows in two-dimensional convective turbulence is studied. The confinement variations are linked to two distinct regulation mechanisms which are also shown to be at the origin of low......-frequency bursting in the fluctuation level and the convective heat flux integral, both resulting in a state of large-scale intermittency. The first one involves the control of convective transport by sheared mean flows. This regulation relies on the conservative transfer of kinetic energy from tilted fluctuations...

  1. Convection with local thermal non-equilibrium and microfluidic effects

    CERN Document Server

    Straughan, Brian

    2015-01-01

    This book is one of the first devoted to an account of theories of thermal convection which involve local thermal non-equilibrium effects, including a concentration on microfluidic effects. The text introduces convection with local thermal non-equilibrium effects in extraordinary detail, making it easy for readers newer to the subject area to understand. This book is unique in the fact that it addresses a large number of convection theories and provides many new results which are not available elsewhere. This book will be useful to researchers from engineering, fluid mechanics, and applied mathematics, particularly those interested in microfluidics and porous media.

  2. Capturing near-Earth asteroids around Earth

    Science.gov (United States)

    Hasnain, Zaki; Lamb, Christopher A.; Ross, Shane D.

    2012-12-01

    The list of detected near-Earth asteroids (NEAs) is constantly growing. NEAs are likely targets for resources to support space industrialization, as they may be the least expensive source of certain needed raw materials. The limited supply of precious metals and semiconducting elements on Earth may be supplemented or even replaced by the reserves floating in the form of asteroids around the solar system. Precious metals make up a significant fraction NEAs by mass, and even one metallic asteroid of ˜1km size and fair enrichment in platinum-group metals would contain twice the tonnage of such metals already harvested on Earth. There are ˜1000 NEAs with a diameter of greater than 1 km. Capturing these asteroids around the Earth would expand the mining industry into an entirely new dimension. Having such resources within easy reach in Earth's orbit could provide an off-world environmentally friendly remedy for impending terrestrial shortages, especially given the need for raw materials in developing nations. In this paper, we develop and implement a conceptually simple algorithm to determine trajectory characteristics necessary to move NEAs into capture orbits around the Earth. Altered trajectories of asteroids are calculated using an ephemeris model. Only asteroids of eccentricity less than 0.1 have been studied and the model is restricted to the ecliptic plane for simplicity. We constrain the time of retrieval to be 10 years or less, based on considerations of the time to return on investment. For the heliocentric phase, constant acceleration is assumed. The acceleration required for transporting these asteroids from their undisturbed orbits to the sphere of influence of the Earth is the primary output, along with the impulse or acceleration necessary to effect capture to a bound orbit once the Earth's sphere of influence is reached. The initial guess for the constant acceleration is provided by a new estimation method, similar in spirit to Edelbaum's. Based on the

  3. Seeking deep convective parameter updates that improve tropical Pacific climatology in CESM using Pareto fronts

    Science.gov (United States)

    Langenbrunner, B.; Neelin, J. D.

    2016-12-01

    Despite increasing complexity and process representation in global climate models (GCMs), accurate climate simulation is limited by uncertainties in sub-grid scale model physics, where cloud processes and precipitation occur, and the interaction with large-scale dynamics. Identifying highly sensitive parameters and constraining them against observations is therefore a valuable step in narrowing uncertainty. However, changes in parameterizations often improve some variables or aspects of the simulation while degrading others. This analysis addresses means of improving GCM simulation of present-day tropical Pacific climate in the face of these tradeoffs. Focusing on the deep convection scheme in the fully coupled Community Earth System Model (CESM) version 1, four parameters were systematically sampled, and a metamodel or model emulator was used to reconstruct the parameter space of this perturbed physics ensemble. Using this metamodel, a Pareto front is constructed to visualize multiobjective tradeoffs in model performance, and results highlight the most important aspects of model physics as well as the most sensitive parameter ranges. For example, parameter tradeoffs arise in the tropical Pacific where precipitation cannot improve without sea surface temperature getting worse. Tropical precipitation sensitivity is found to be highly nonlinear for low values of entrainment in convecting plumes, though it is fairly insensitive at the high end of the plausible range. Increasing the adjustment timescale for convective closure causes the centroid of tropical precipitation to vary as much as two degrees latitude, highlighting the effect these physics can have on large-scale features of the hydrological cycle. The optimization procedure suggests that simultaneously increasing the maximum downdraft mass flux fraction and the adjustment timescale can yield improvements to surface temperature and column water vapor without degrading the simulation of precipitation. These

  4. Coupling between lower‐tropospheric convective mixing and low‐level clouds: Physical mechanisms and dependence on convection scheme

    Science.gov (United States)

    Bony, Sandrine; Dufresne, Jean‐Louis; Roehrig, Romain

    2016-01-01

    Abstract Several studies have pointed out the dependence of low‐cloud feedbacks on the strength of the lower‐tropospheric convective mixing. By analyzing a series of single‐column model experiments run by a climate model using two different convective parametrizations, this study elucidates the physical mechanisms through which marine boundary‐layer clouds depend on this mixing in the present‐day climate and under surface warming. An increased lower‐tropospheric convective mixing leads to a reduction of low‐cloud fraction. However, the rate of decrease strongly depends on how the surface latent heat flux couples to the convective mixing and to boundary‐layer cloud radiative effects: (i) on the one hand, the latent heat flux is enhanced by the lower‐tropospheric drying induced by the convective mixing, which damps the reduction of the low‐cloud fraction, (ii) on the other hand, the latent heat flux is reduced as the lower troposphere stabilizes under the effect of reduced low‐cloud radiative cooling, which enhances the reduction of the low‐cloud fraction. The relative importance of these two different processes depends on the closure of the convective parameterization. The convective scheme that favors the coupling between latent heat flux and low‐cloud radiative cooling exhibits a stronger sensitivity of low‐clouds to convective mixing in the present‐day climate, and a stronger low‐cloud feedback in response to surface warming. In this model, the low‐cloud feedback is stronger when the present‐day convective mixing is weaker and when present‐day clouds are shallower and more radiatively active. The implications of these insights for constraining the strength of low‐cloud feedbacks observationally is discussed. PMID:28239438

  5. Anisotropy in the deep Earth

    Science.gov (United States)

    Romanowicz, Barbara; Wenk, Hans-Rudolf

    2017-08-01

    Seismic anisotropy has been found in many regions of the Earth's interior. Its presence in the Earth's crust has been known since the 19th century, and is due in part to the alignment of anisotropic crystals in rocks, and in part to patterns in the distribution of fractures and pores. In the upper mantle, seismic anisotropy was discovered 50 years ago, and can be attributed for the most part, to the alignment of intrinsically anisotropic olivine crystals during large scale deformation associated with convection. There is some indication for anisotropy in the transition zone, particularly in the vicinity of subducted slabs. Here we focus on the deep Earth - the lower mantle and core, where anisotropy is not yet mapped in detail, nor is there consensus on its origin. Most of the lower mantle appears largely isotropic, except in the last 200-300 km, in the D″ region, where evidence for seismic anisotropy has been accumulating since the late 1980s, mostly from shear wave splitting measurements. Recently, a picture has been emerging, where strong anisotropy is associated with high shear velocities at the edges of the large low shear velocity provinces (LLSVPs) in the central Pacific and under Africa. These observations are consistent with being due to the presence of highly anisotropic MgSiO3 post-perovskite crystals, aligned during the deformation of slabs impinging on the core-mantle boundary, and upwelling flow within the LLSVPs. We also discuss mineral physics aspects such as ultrahigh pressure deformation experiments, first principles calculations to obtain information about elastic properties, and derivation of dislocation activity based on bonding characteristics. Polycrystal plasticity simulations can predict anisotropy but models are still highly idealized and neglect the complex microstructure of polyphase aggregates with strong and weak components. A promising direction for future progress in understanding the origin of seismic anisotropy in the deep mantle

  6. On the determination of the neutral drag coefficient in the convective boundary layer

    DEFF Research Database (Denmark)

    Grachev, A.A.; Fairall, C.W.; Larsen, Søren Ejling

    1998-01-01

    Based on the idea that free convection can be considered as a particular case of forced convection, where the gusts driven by the large-scale eddies are scaled with the Deardorff convective velocity scale, a new formulation for the neutral drag coefficient, C-Dn, in the convective boundary layer ...

  7. Convectively coupled Kelvin waves in aquachannel simulations: 1. Propagation speeds, composite structures, and comparison with aquaplanets

    Science.gov (United States)

    Blanco, Joaquín. E.; Nolan, David S.; Tulich, Stefan N.

    2016-10-01

    Convectively coupled Kelvin waves (CCKWs) represent a significant contribution to the total variability of the Intertropical Convergence Zone (ITCZ). This study analyzes the structure and propagation of CCKWs simulated by the Weather Research and Forecasting (WRF) model using two types of idealized domains. These are the "aquachannel," a flat rectangle on a beta plane with zonally periodic boundary conditions and length equal to the Earth's circumference at the equator, and the "aquapatch," a square domain with zonal extent equal to one third of the aquachannel's length. A series of simulations are performed, including a doubly nested aquapatch, in which convection is solved explicitly along the equator. The model intercomparison is carried out throughout the use of several techniques such as power spectra, filtering, wave tracking, and compositing, and it is extended to some simulations from the Aquaplanet Experiment (APE). Results show that despite the equatorial superrotation bias produced by the WRF simulations, the CCKWs simulated with this model propagate with similar phase speeds (relative to the low-level mean flow) as the corresponding waves from the APE simulations. Horizontal and vertical structures of the CCKWs simulated with aquachannels are also in overall good agreement with those from aquaplanet simulations and observations, although there is a distortion of the zonal extent of anomalies when the shorter aquapatch is used.

  8. GEOFLOW: simulation of convection in a spherical shell under central force field

    Directory of Open Access Journals (Sweden)

    P. Beltrame

    2006-01-01

    Full Text Available Time-dependent dynamical simulations related to convective motion in a spherical gap under a central force field due to the dielectrophoretic effect are discussed. This work is part of the preparation of the GEOFLOW-experiment which is planned to run in a microgravity environment. The goal of this experiment is the simulation of large-scale convective motion in a geophysical or astrophysical framework. This problem is new because of, on the one hand, the nature of the force field (dielectrophoretic effect and, on another hand, the high degree of symmetries of the system, e.g. the top-bottom reflection. Thus, the validation of this simulation with well-known results is not possible. The questions concerning the influence of the dielectrophoretic force and the possibility to reproduce the theoretically expected motions in the astrophysical framework, are open. In the first part, we study the system in terrestrial conditions: the unidirectional Earth's force is superimposed on the central dielectrophoretic force field to compare with the laboratory experiments during the development of the equipment. In the second part, the GEOFLOW-experiment simulations in weightless conditions are compared with theoretical studies in the astrophysical framework's, in the first instance a fluid under a self-gravitating force field. We present complex time-dependent dynamics, where the dielectrophoretic force field causes significant differences in the flow compared to the case that does not involve this force field.

  9. Importance of Rain Evaporation and Continental Convection in the Tropical Water Cycle

    Science.gov (United States)

    Worden, John; Noone, David; Bowman, Kevin; Beer, R.; Eldering, A.; Fisher, B.; Gunson, M.; Goldman, Aaron; Kulawik, S. S.; Lampel, Michael; hide

    2007-01-01

    Atmospheric moisture cycling is an important aspect of the Earth's climate system, yet the processes determining atmospheric humidity are poorly understood. For example, direct evaporation of rain contributes significantly to the heat and moisture budgets of clouds, but few observations of these processes are available. Similarly, the relative contributions to atmospheric moisture over land from local evaporation and humidity from oceanic sources are uncertain. Lighter isotopes of water vapour preferentially evaporate whereas heavier isotopes preferentially condense and the isotopic composition of ocean water is known. Here we use this information combined with global measurements of the isotopic composition of tropospheric water vapour from the Tropospheric Emission Spectrometer (TES) aboard the Aura spacecraft, to investigate aspects of the atmospheric hydrological cycle that are not well constrained by observations of precipitation or atmospheric vapour content. Our measurements of the isotopic composition of water vapour near tropical clouds suggest that rainfall evaporation contributes significantly to lower troposphere humidity, with typically 20% and up to 50% of rainfall evaporating near convective clouds. Over the tropical continents the isotopic signature of tropospheric water vapour differs significantly from that of precipitation, suggesting that convection of vapour from both oceanic sources and evapotranspiration are the dominant moisture sources. Our measurements allow an assessment of the intensity of the present hydrological cycle and will help identify any future changes as they occur.

  10. Unsteady free convection from a sphere in a porous medium with variable surface temperature

    International Nuclear Information System (INIS)

    Rahimi, Asghar Baradaran

    2011-01-01

    All works on natural convection around a sphere in porous media, except the transient work of Nakayama and Koyama and Nguyen and Paik which are for body of arbitrary geometric configuration, have been conducted only for constant temperature or constant heat flux on its surface. In this paper a transient free convection flow around a sphere with variable surface temperature and embedded in a porous medium has been considered. The temperature of the sphere is suddenly raised and subsequently maintained at values that vary with position on surface. This situation is specially encountered when nuclear wastes, for example, are buried in earth. The method of asymptotic expansions is applied for small Rayleigh numbers up to the second-order of approximation and then a finite-difference scheme is used to solve the problem numerically for finite values of Rayleigh numbers. Transient and steady-state flow and temperature patterns around the sphere are discussed in details and a comparison between numerical and analytical results has been presented. (author)

  11. Risk of placenta praevia is linked to endometrial thickness in a retrospective cohort study of 4537 singleton assisted reproduction technology births.

    Science.gov (United States)

    Rombauts, L; Motteram, C; Berkowitz, E; Fernando, S

    2014-12-01

    Is endometrial thickness measured prior to embryo transfer associated with placenta praevia? Following IVF, the risk of placenta praevia is increased 4-fold in women with an endometrial thickness of >12 mm compared with women with an endometrial thickness of women who had 4537 singleton assisted reproduction technology (ART) births occurring between January 2006 and June 2012 with no loss to follow-up. The primary outcome measure was the diagnosis of placenta praevia, made by the treating obstetrician on a transvaginal ultrasound in the third trimester. Women who had singleton births following single embryo transfer performed at Monash IVF in Melbourne, Australia were included. Of the 4537 cycles leading to a singleton ART birth, 2951 were stimulated cycles with fresh embryo transfers; 355 were hormone replacement therapy frozen embryo transfers and 1231 were natural cycles with frozen embryo transfers. The dataset was analysed using binary logistic general estimating equations to calculate odds ratios for placenta praevia adjusted (aOR) for known confounders. The study groups did not differ significantly in age, BMI and aetiologies of infertility prior to IVF treatment. When compared with stimulated cycles, placenta praevia was less common in women undergoing natural cycles with frozen embryo transfers (OR 0.44, 95% confidence interval (CI) 0.27-0.70, P women with an endometrial thickness of women with an endometrial thickness of 9-12 mm had an aOR of 2.02 (95% CI 1.12-3.65, P = 0.02) and women with an endometrial thickness >12 mm had an aOR of 3.74 (95% CI 1.90-7.34, P women with no previous births. The study is retrospective in nature, not all confounders may have been accounted for and details on previous intrauterine surgery, a known risk factor, were not available. In addition, ultrasound assessments were carried out by several highly trained operators measuring the endometrial thickness, the main independent variable, in a two-dimensional plane and some

  12. Hands On Earth Science.

    Science.gov (United States)

    Weisgarber, Sherry L.; Van Doren, Lisa; Hackathorn, Merrianne; Hannibal, Joseph T.; Hansgen, Richard

    This publication is a collection of 13 hands-on activities that focus on earth science-related activities and involve students in learning about growing crystals, tectonics, fossils, rock and minerals, modeling Ohio geology, geologic time, determining true north, and constructing scale-models of the Earth-moon system. Each activity contains…

  13. EARTH FROM SPACE

    Indian Academy of Sciences (India)

    Table of contents. EARTH FROM SPACE · Slide 2 · Earth System · Slide 4 · Global water cycle · Slide 6 · Slide 7 · Direct Observations of Recent Climate Change · Slide 9 · Slide 10 · Snow cover and Arctic sea ice are decreasing · Polar Melting & Global Heat Transport · Antarctica: Melting and Thickening · Slide 14 · Slide 15.

  14. Introducing Earth's Orbital Eccentricity

    Science.gov (United States)

    Oostra, Benjamin

    2015-01-01

    Most students know that planetary orbits, including Earth's, are elliptical; that is Kepler's first law, and it is found in many science textbooks. But quite a few are mistaken about the details, thinking that the orbit is very eccentric, or that this effect is somehow responsible for the seasons. In fact, the Earth's orbital eccentricity is…

  15. Earth Flyby Anomalies

    OpenAIRE

    Nieto, Michael Martin; Anderson, John D.

    2009-01-01

    In a reference frame fixed to the solar system's center of mass, a satellite's energy will change as it is deflected by a planet. But a number of satellites flying by Earth have also experienced energy changes in the Earth-centered frame -- and that's a mystery.

  16. Long-distance migration of radon within the earth

    International Nuclear Information System (INIS)

    Fleischer, R.L.; Mogro-Campero, A.

    1976-01-01

    There is need for identification and understanding of methods for locating subsurface uranium. A major hope for definitive recognition of ore at depths of more than a few meters is the measurement of the near surface emanation of 222 Rn, the sole distinctive gaseous product of the decay of uranium. Scattered observations suggest that radon can migrate through the earth for distances of greater than or equal to 100 m. A model is proposed in which convective flow of subsurface air or water through a porous medium is induced by the geothermal gradient. Several of the predictions of the model are consistent with observations at a uranium ore deposit in New Mexico

  17. Convectively driven flow past an infinite moving vertical cylinder with ...

    Indian Academy of Sciences (India)

    , free convective flow over an infinite moving vertical cylinder under combined buoyancy effects of heat and mass transfer with thermal and mass stratifications. Laplace transform technique is adopted for finding solutions for velocity, ...

  18. Convective heat and mass transfer in rotating disk systems

    CERN Document Server

    Shevchuk, Igor V

    2009-01-01

    The book describes results of investigations of a series of convective heat and mass transfer problems in rotating-disk systems. Methodology used included integral methods, self-similar and approximate analytical solutions, as well as CFD.

  19. effect of chemical reaction on unsteady mhd free convective two ...

    African Journals Online (AJOL)

    Joseph et al.

    coefficient of skin friction, Nusselt number and Sherwood number are also tabulated and discussed appropriately. It was observed that the increase in chemical reaction coefficient/parameter suppresses both velocity and concentration profiles. Keywords: Chemical Reaction, MHD, Convective, Immiscible,. Unsteady.

  20. Simultaneous effects of Hall and convective conditions on peristaltic ...

    Indian Academy of Sciences (India)

    stress fluid in an inclined asymmetric channel with convective conditions. Soret and Dufour and Hall effects are taken into account. Analysis has been carried out in a wave frame of reference. Expressions for velocity, pressure gradient, temperature ...