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Sample records for convectively stabilised background

  1. Stabilised dG-FEM for incompressible natural convection flows with boundary and moving interior layers on non-adapted meshes

    NASA Astrophysics Data System (ADS)

    Schroeder, Philipp W.; Lube, Gert

    2017-04-01

    This paper presents heavily grad-div and pressure jump stabilised, equal- and mixed-order discontinuous Galerkin finite element methods for non-isothermal incompressible flows based on the Oberbeck-Boussinesq approximation. In this framework, the enthalpy-porosity model for multiphase flow in melting and solidification problems can be employed. By considering the differentially heated cavity and the melting of pure gallium in a rectangular enclosure, it is shown that both boundary layers and sharp moving interior layers can be handled naturally by the proposed class of non-conforming methods. Due to the stabilising effect of the grad-div term and the robustness of discontinuous Galerkin methods, it is possible to solve the underlying problems accurately on coarse, non-adapted meshes. The interaction of heavy grad-div stabilisation and discontinuous Galerkin methods significantly improves the mass conservation properties and the overall accuracy of the numerical scheme which is observed for the first time. Hence, it is inferred that stabilised discontinuous Galerkin methods are highly robust as well as computationally efficient numerical methods to deal with natural convection problems arising in incompressible computational thermo-fluid dynamics.

  2. Background error covariance modelling for convective-scale variational data assimilation

    NASA Astrophysics Data System (ADS)

    Petrie, R. E.

    An essential component in data assimilation is the background error covariance matrix (B). This matrix regularizes the ill-posed data assimilation problem, describes the confidence of the background state and spreads information. Since the B-matrix is too large to represent explicitly it must be modelled. In variational data assimilation it is essentially a climatological approximation of the true covariances. Such a conventional covariance model additionally relies on the imposition of balance conditions. A toy model which is derived from the Euler equations (by making appropriate simplifications and introducing tuneable parameters) is used as a convective-scale system to investigate these issues. Its behaviour is shown to exhibit large-scale geostrophic and hydrostatic balance while permitting small-scale imbalance. A control variable transform (CVT) approach to modelling the B-matrix where the control variables are taken to be the normal modes (NM) of the linearized model is investigated. This approach is attractive for convective-scale covariance modelling as it allows for unbalanced as well as appropriately balanced relationships. Although the NM-CVT is not applied to a data assimilation problem directly, it is shown to be a viable approach to convective-scale covariance modelling. A new mathematically rigorous method to incorporate flow-dependent error covariances with the otherwise static B-matrix estimate is also proposed. This is an extension to the reduced rank Kalman filter (RRKF) where its Hessian singular vector calculation is replaced by an ensemble estimate of the covariances, and is known as the ensemble RRKF (EnRRKF). Ultimately it is hoped that together the NM-CVT and the EnRRKF would improve the predictability of small-scale features in convective-scale weather forecasting through the relaxation of inappropriate balance and the inclusion of flow-dependent covariances.

  3. Effects of Convective Transport on the Budget of Amazonian Aerosol under Background Conditions

    NASA Astrophysics Data System (ADS)

    Wang, J.; Krejci, R.; Giangrande, S. E.; Kuang, C.; Barbosa, H. M.; Brito, J.; Carbone, S.; Chi, X.; Comstock, J. M.; Ditas, F.; Lavric, J. V.; Manninen, H. E.; Mei, F.; Moran, D.; Pöhlker, C.; Pöhlker, M. L.; Saturno, J.; Schmid, B.; Souza, R. A. F. D.; Springston, S. R.; Tomlinson, J. M.; Toto, T.; Walter, D.; Wimmer, D.; Smith, J. N.; Machado, L.; Artaxo, P.; Andreae, M. O.; Martin, S. T.

    2016-12-01

    Aerosol particles can strongly influence the radiative properties of clouds, and they represent one of the largest uncertainties in computer simulations of climate change. The large uncertainty is in large part due to a poor understanding of processes under natural conditions, which serves as the baseline to measure change against. Understanding the processes under natural conditions is critical for a reliable assessment and quantification of ongoing and future climate change. The Amazon rainforest is one of the few continental regions where aerosol particles and their precursors can be studied under near-natural conditions. Here we examine the aerosol number and CCN budget under background conditions in the Amazon basin using data collected during the Observations and Modeling of the Green Ocean Amazon (GoAmazon 2014/5) campaign, which took place from January 2014 to December 2015 near Manaus, Brazil. The aerosol size spectrum was observed at the Amazon Tall Tower Observatory (ATTO), 150 km upwind of Manaus, and its variation with convection and precipitation during the wet season is presented. Air masses arriving at the ATTO during the wet season are typically brought by the northeasterly trade winds and travel across at least 1000 km of undeveloped tropical rainforest, therefore are generally clean. Also shown are vertical profiles of aerosol observed onboard the DOE Gulfstream-1 research aircraft. The impact of convective transport on the budget of boundary layer aerosol and CCN under the background conditions is discussed.

  4. Background Noises Versus Intraseasonal Variation Signals: Small vs. Large Convective Cloud Objects From CERES Aqua Observations

    NASA Technical Reports Server (NTRS)

    Xu, Kuan-Man

    2015-01-01

    During inactive phases of Madden-Julian Oscillation (MJO), there are plenty of deep but small convective systems and far fewer deep and large ones. During active phases of MJO, a manifestation of an increase in the occurrence of large and deep cloud clusters results from an amplification of large-scale motions by stronger convective heating. This study is designed to quantitatively examine the roles of small and large cloud clusters during the MJO life cycle. We analyze the cloud object data from Aqua CERES (Clouds and the Earth's Radiant Energy System) observations between July 2006 and June 2010 for tropical deep convective (DC) and cirrostratus (CS) cloud object types according to the real-time multivariate MJO index, which assigns the tropics to one of the eight MJO phases each day. The cloud object is a contiguous region of the earth with a single dominant cloud-system type. The criteria for defining these cloud types are overcast footprints and cloud top pressures less than 400 hPa, but DC has higher cloud optical depths (=10) than those of CS (<10). The size distributions, defined as the footprint numbers as a function of cloud object diameters, for particular MJO phases depart greatly from the combined (8-phase) distribution at large cloud-object diameters due to the reduced/increased numbers of cloud objects related to changes in the large-scale environments. The medium diameter corresponding to the combined distribution is determined and used to partition all cloud objects into "small" and "large" groups of a particular phase. The two groups corresponding to the combined distribution have nearly equal numbers of footprints. The medium diameters are 502 km for DC and 310 km for cirrostratus. The range of the variation between two extreme phases (typically, the most active and depressed phases) for the small group is 6-11% in terms of the numbers of cloud objects and the total footprint numbers. The corresponding range for the large group is 19-44%. In

  5. Variations in Convectively Coupled Wave Activity and their Relationship with the Background Environment

    NASA Astrophysics Data System (ADS)

    Leroux, S.; Kiladis, G. N.

    2010-12-01

    Different types of convectively coupled equatorial waves are isolated through space-time filtering techniques applied to the NCAR/NCEP Outgoing Long-wave Radiation (OLR) global daily dataset. For each type of wave, a wavelet analysis is applied on the filtered OLR time-series at each grid-point in the Tropics, and the wavelet power is averaged over the range of scale corresponding to the wave type. The resulting daily quantity can be used as an index of the evolution of wave activity with time. The variations of these envelopes of wave activity, and the main time-scales involved, are studied in the context of the waves’ background environment through Empirical Orthogonal Function (EOF) and lag-regression analyses. The evolution of the waves’ envelope of activity onto an index of the Madden Julian Oscillation for the winter and summer seasons suggest that part of the Kelvin wave and Equatorial Rossby (ER) wave activity signals are modulated by MJO phases. Interestingly, the first spatial EOF mode of the Kelvin wave activity envelope does not correspond directly to an MJO signal. This suggests that other modulating factors are likely to be involved. The potential influence of the background flow and of the extra-tropical transient activity in the mid-latitude storm-tracks are also explored. It is found that Pacific Kelvin wave activity is favored during periods of westerly shear with height on the equator in that basin. Strong co-dependence of Kelvin wave activity on the extratropical storm track activity is seen, suggesting that at least some periods of Kelvin activity is excited by extratropical forcing.

  6. Ozone tendencies in the free troposphere: A comparison of net ozone production for background conditions and convectively processed air in the tropics and extratropics

    NASA Astrophysics Data System (ADS)

    Bozem, H.

    2009-04-01

    Ozone is an important oxidant and a greenhouse gas. While the highest mixing ratios are found in the stratosphere, significant changes of ozone at tropopause levels can have significant climate effects. Furthermore ozone is the main precursor of the hydroxyl radical OH, thus strongly affecting the oxidation power of the atmosphere. Convective transport of ozone and its precursors between low altitudes near the surface and the middle and upper troposphere influences ozone in the tropopause region. Data from the airborne measurement campaigns, GABRIEL 2005 (Suriname, South America) and HOOVER 2006 and 2007 (Europe) are presented. We investigate the ozone budget in the free troposphere in cases of deep convection and in background conditions. Steady state model calculations, based on in-situ measurements of O3, NO, OH, HO2 and actinic radiation are used to calculate the net O3 tendency for background and convectively processed air. In the extratropics the net ozone production rate (OPR) in convective outflow amounts to 1.85 ppbv/h (Range: 0.26 to 8.21 ppbv/h, depending on the mixing ratio of NO and HO2), while the background atmosphere shows no clear tendency. In the tropics an OPR of 0.23 ppbv/h (0.01 to 1.13 ppbv/h) in the outflow and 0.08 ppbv/h (-0.01 to 0.47 ppbv/h) for the background atmosphere was calculated. Convective outflow in both regimes is able to produce ozone in high amounts. For background conditions no clear tendency for the extratropics compared to the tropics is found.

  7. Stabilising springs for fixed lingual retainer.

    PubMed

    Karthikeyan, M K; Ramachandraprabhakar; Saravanan, R; Rajvikram, N; Kuppuchamy

    2013-11-01

    Most treated malocclusion needs fixed lingual retention. To stabilise fixed lingual retainer in the exact location needs proper stabilisation. Proper stabilization requires a holding spring. This Stabilising Spring should be easy to fabricate and help the clinician to stabilise the retainer quickly and save the chair side time. More over it should not irritate the mucosa and should be easy to insert and remove.

  8. Cyclodextrin stabilised emulsions and cyclodextrinosomes.

    PubMed

    Mathapa, Baghali G; Paunov, Vesselin N

    2013-11-07

    We report the preparation of o/w emulsions stabilised by microcrystals of cyclodextrin-oil inclusion complexes. The inclusion complexes are formed by threading cyclodextrins from the aqueous phase on n-tetradecane or silicone oil molecules from the emulsion drop surface which grow further into microrods and microplatelets depending on the type of cyclodextrin (CD) used. These microcrystals remain attached on the surface of the emulsion drops and form densely packed layers which resemble Pickering emulsions. The novelty of this emulsion stabilisation mechanism is that molecularly dissolved cyclodextrin from the continuous aqueous phase is assembled into colloid particles directly onto the emulsion drop surface, i.e. molecular adsorption leads to effective Pickering stabilisation. The β-CD stabilised tetradecane-in-water emulsions were so stable that we used this system as a template for preparation of cyclodextrinosomes. These structures were produced solely through formation of cyclodextrin-oil inclusion complexes and their assembly into a crystalline phase on the drop surface retained its stability after the removal of the core oil. The structures of CD-stabilised tetradecane-in-water emulsions were characterised using optical microscopy, fluorescence microscopy, cross-polarised light microscopy and WETSEM while the cyclodextrinosomes were characterised by SEM. We also report the preparation of CD-stabilised emulsions with a range of other oils, including tricaprylin, silicone oil, isopropyl myristate and sunflower oil. We studied the effect of the salt concentration in the aqueous phase, the type of CD and the oil volume fraction on the type of emulsion formed. The CD-stabilised emulsions can be applied in a range of surfactant-free formulations with possible applications in cosmetics, home and personal care. Cyclodextrinosomes could find applications in pharmaceutical formulations as microencapsulation and drug delivery vehicles.

  9. Spatial Variability of the Background Diurnal Cycle of Deep Convection around the GoAmazon2014/5 Field Campaign Sites

    SciTech Connect

    Burleyson, Casey D.; Feng, Zhe; Hagos, Samson M.; Fast, Jerome; Machado, Luiz A. T.; Martin, Scot T.

    2016-07-01

    The Amazon rainforest is one of a few regions of the world where continental tropical deep convection occurs. The Amazon’s isolation makes it challenging to observe, but also creates a unique natural laboratory to study anthropogenic impacts on clouds and precipitation in an otherwise pristine environment. Extensive measurements were made upwind and downwind of the large city of Manaus, Brazil during the Observations and Modeling of the Green Ocean Amazon 2014-2015 (GoAmazon2014/5) field campaign. In this study, 15 years of high-resolution satellite data are analyzed to examine the spatial and diurnal variability of convection occurring around the GoAmazon2014/5 sites. Interpretation of anthropogenic differences between the upwind (T0) and downwind (T1-T3) sites is complicated by naturally-occurring spatial variability between the sites. During the rainy season, the inland propagation of the previous day’s sea-breeze front happens to be in phase with the background diurnal cycle near Manaus, but is out of phase elsewhere. Enhanced convergence between the river-breezes and the easterly trade winds generates up to 10% more frequent deep convection at the GoAmazon2014/5 sites east of the river (T0a, T0t/k, and T1) compared to the T3 site which was located near the western bank. In general, the annual and diurnal cycles during 2014 were representative of the 2000-2013 distributions. The only exceptions were in March when the monthly mean rainrate was above the 95th percentile and September when both rain frequency and intensity were suppressed. The natural spatial variability must be accounted for before interpreting anthropogenically-induced differences among the GoAmazon2014/5 sites.

  10. Stabilising Springs for Fixed Lingual Retainer

    PubMed Central

    Karthikeyan, M.K.; Ramachandraprabhakar; Saravanan, R.; Rajvikram, N.; Kuppuchamy

    2013-01-01

    Most treated malocclusion needs fixed lingual retention. To stabilise fixed lingual retainer in the exact location needs proper stabilisation. Proper stabilization requires a holding spring. This Stabilising Spring should be easy to fabricate and help the clinician to stabilise the retainer quickly and save the chair side time. More over it should not irritate the mucosa and should be easy to insert and remove. PMID:24392431

  11. Mesoscale Convective Vortices in Multiscale, Idealized Simulations: Dependence on Background State, Interdependency with Moist Baroclinic Cyclones, and Comparison with BAMEX Observations

    DTIC Science & Technology

    2010-04-01

    The most rapid potential vorticity ( PV ) development occurred in and just behind the leading convective line. The entire system grew upscale with time...as the newly created PV rotated cyclonically around a common center as the leading convective line continued to expand outward. Ten hours after the...Using potential vorticity ( PV ) concepts, the intensification can be explained by the vertical gra- dient of diabatic heating within the convective system

  12. Global asymptotic stabilisation for switched planar systems

    NASA Astrophysics Data System (ADS)

    Zhang, Junfeng; Han, Zhengzhi; Huang, Jun

    2015-04-01

    This paper studies the stabilisation problem of a class of switched planar systems. The present method is different from the existing one designing directly controllers for the underlying systems. The controllers are constructed through two steps. Firstly, by means of the backstepping approach, homogeneous controllers stabilising the nominal systems are obtained. Secondly, the controllers stabilising the planar subsystems are attained by modifying the obtained homogeneous controllers. The controllers depend on perturbations of the switched systems. Finally, by using the multiple Lyapunov functions approach, a sufficient condition of the stabilisation for switched planar systems is given. The conclusions are extended to multiple dimensional switched systems. An illustrative example verifies the validity of the design.

  13. Mycorrhizal aspects in slope stabilisation

    NASA Astrophysics Data System (ADS)

    Graf, Frank

    2016-04-01

    In order to re-colonise and stabilise slopes affected by superficial soil failure with plants essential requirements have to be met: the plants must grow the plants must survive sustainably plant succession must start and continuously develop These requirements, however, are anything but easy given, particularly under the often hostile environmental conditions dominating on bare and steep slopes. Mycorrhizal fungi, the symbiotic partners of almost all plants used in eco-engineering, are said to improve the plants' ability to overcome periods governed by strongly (growth) limiting factors. Subsequently, results of investigations are presented of mycorrhizal effects on different plant and soil functions related to eco-engineering in general and soil and slope stabilisation in particular. Generally, inoculation yielded higher biomass of the host plants above as well as below ground. Furthermore, the survival rate was higher for mycorrhized compared to non-mycorrhized plants, particularly under extreme environmental conditions. However, the scale of the mycorrhizal impact may be species specific of both the plant host as well as the fungal partner(s) and often becomes evident only after a certain time lag. Depending on the plant-fungus combination the root length per soil volume was found to be between 0 and 2.5 times higher for inoculated compared to non-inoculated specimens. On an alpine graded ski slope the survival of inoculated compared to non-treated Salix herbacea cuttings was significant after one vegetation period only for one of the three added mycorrhizal fungus species. However, after three years all of the inoculated plantlets performed significantly better than the non-inoculated controls. The analysis of the potential for producing and stabilising soil aggregates of five different ectomycorrhizal fungi showed high variation and, for the species Inocybe lacera, no significant difference compared to untreated soil. Furthermore, inoculation of Salix

  14. Antipsychotics, mood stabilisers, and risk of violent crime

    PubMed Central

    Fazel, Seena; Zetterqvist, Johan; Larsson, Henrik; Långström, Niklas; Lichtenstein, Paul

    2014-01-01

    Summary Background Antipsychotics and mood stabilisers are prescribed widely to patients with psychiatric disorders worldwide. Despite clear evidence for their efficacy in relapse prevention and symptom relief, their effect on some adverse outcomes, including the perpetration of violent crime, is unclear. We aimed to establish the effect of antipsychotics and mood stabilisers on the rate of violent crime committed by patients with psychiatric disorders in Sweden. Methods We used linked Swedish national registers to study 82 647 patients who were prescribed antipsychotics or mood stabilisers, their psychiatric diagnoses, and subsequent criminal convictions in 2006–09. We did within-individual analyses to compare the rate of violent criminality during the time that patients were prescribed these medications versus the rate for the same patients while they were not receiving the drugs to adjust for all confounders that remained constant within each participant during follow-up. The primary outcome was the occurrence of violent crime, according to Sweden's national crime register. Findings In 2006–09, 40 937 men in Sweden were prescribed antipsychotics or mood stabilisers, of whom 2657 (6·5%) were convicted of a violent crime during the study period. In the same period, 41 710 women were prescribed these drugs, of whom 604 (1·4 %) had convictions for violent crime. Compared with periods when participants were not on medication, violent crime fell by 45% in patients receiving antipsychotics (hazard ratio [HR] 0·55, 95% CI 0·47–0·64) and by 24% in patients prescribed mood stabilisers (0·76, 0·62–0·93). However, we identified potentially important differences by diagnosis—mood stabilisers were associated with a reduced rate of violent crime only in patients with bipolar disorder. The rate of violence reduction for antipsychotics remained between 22% and 29% in sensitivity analyses that used different outcomes (any crime, drug-related crime, less

  15. Assessment: Monitoring & Evaluation in a Stabilisation Context

    DTIC Science & Technology

    2010-09-15

    promote political processes and governance structures. This should enable a political settlement that institutionalises non-violent contests for power...of a political settlement , amenable to UK interests, between this triumvirate of actors. The Stabilisation Unit perspective is similar stating that...peaceful political settlement to produce a legitimate indigenous government, which can better serve its people. 102. Stabilisation will invariably sit

  16. Plasma vertical stabilisation in ITER

    NASA Astrophysics Data System (ADS)

    Gribov, Y.; Kavin, A.; Lukash, V.; Khayrutdinov, R.; Huijsmans, G. T. A.; Loarte, A.; Snipes, J. A.; Zabeo, L.

    2015-07-01

    This paper describes the progress in analysis of the ITER plasma vertical stabilisation (VS) system since its design review in 2007-2008. Two indices characterising plasma VS were studied. These are (1) the maximum value of plasma vertical displacement due to free drift that can be stopped by the VS system and (2) the maximum root mean square value of low frequency noise in the dZ/dt measurement signal used in the VS feedback loop. The first VS index was calculated using the PET code for 15 MA plasmas with the nominal position and shape. The second VS index was studied with the DINA code in the most demanding simulations for plasma magnetic control of 15 MA scenarios with the fastest plasma current ramp-up and early X-point formation, the fastest plasma current ramp-down in a divertor configuration, and an H to L mode transition at the current flattop. The studies performed demonstrate that the VS in-vessel coils, adopted recently in the baseline design, significantly increase the range of plasma controllability in comparison with the stabilising systems VS1 and VS2, providing operating margins sufficient to achieve ITER's goals specified in the project requirements. Additionally two sets of the DINA code simulations were performed with the goal of assessment of the capability of the PF system with the VS in-vessel coils: (i) to control the position of runaway electrons generated during disruptions in 15 MA scenarios and (ii) to trigger ELMs in H-mode plasmas of 7.5 MA/2.65 T scenarios planned for the early phase of ITER operation. It was also shown that ferromagnetic structures of the vacuum vessel (ferromagnetic inserts) and test blanket modules insignificantly affect the plasma VS.

  17. Bioconjugation and stabilisation of biomolecules in biosensors

    PubMed Central

    Drago, Guido A.

    2016-01-01

    Suitable bioconjugation strategies and stabilisation of biomolecules on electrodes is essential for the development of novel and commercially viable biosensors. In the present review, the functional groups that comprise the selectable targets for practical bioconjugation methods are discussed. We focus on describing the most common immobilisation techniques used in biosensor construction, which are classified into irreversible and reversible methods. Concerning the stability of proteins, the two main types of stability may be defined as (i) storage or shelf stability, and (ii) operational stability. Both types of stability are explained, as well as the introduction of an electrophoretic technique for predicting protein–polymer interactions. In addition, solution and dry stabilisation as well as stabilisation using the covalent immobilisation of proteins are discussed including possible factors that influence stability. Finally, the integration of nanomaterials, such as magnetic particles, with protein immobilisation is discussed in relation to protein stability studies. PMID:27365036

  18. Partial stability and stabilisation of Boolean networks

    NASA Astrophysics Data System (ADS)

    Chen, Hong-Wei; Sun, Liang-Jie; Liu, Yang

    2016-07-01

    In this paper, we investigate the stability of Boolean networks and the stabilisation of Boolean control networks with respect to part of the system's states. First, an algebraic expression of the Boolean (control) network is derived by the semi-tensor product of matrices. Then, some necessary and sufficient conditions for partial stability of Boolean networks are given. Finally, the stabilisation of Boolean control networks by a free control sequence and a state-feedback control is investigated and the respective necessary and sufficient conditions are obtained. Examples are provided to illustrate the efficiency of the obtained results.

  19. Local string models and moduli stabilisation

    NASA Astrophysics Data System (ADS)

    Quevedo, Fernando

    2015-03-01

    A brief overview is presented of the progress made during the past few years on the general structure of local models of particle physics from string theory including: moduli stabilisation, supersymmetry breaking, global embedding in compact Calabi-Yau compactifications and potential cosmological implications. Type IIB D-brane constructions and the Large Volume Scenario (LVS) are discussed in some detail emphasising the recent achievements and the main open questions.

  20. Local String Models and Moduli Stabilisation

    NASA Astrophysics Data System (ADS)

    Quevedo, Fernando

    2014-12-01

    A brief overview is presented of the progress made during the past few years on the general structure of local models of particle physics from string theory including: moduli stabilisation, supersymmetry breaking, global embedding in compact Calabi-Yau compactifications and potential cosmological implications. Type IIB D-brane constructions and the Large Volume Scenario (LVS) are discussed in some detail emphasising the recent achievements and the main open questions.

  1. In situ stabilisation/solidification: project lifecycle.

    PubMed

    Fleri, Mark A; Whetstone, Greg T

    2007-03-15

    The successful application of any remedial technology, including stabilisation/solidification, begins with the site investigation. Following a review of the data collected during the site investigation, a treatability study (TS) and pilot study (PS) are prerequisites to full-scale implementation as they show the effects and delivery of binders to the soils, the geochemistry of the soils, and binder dosages necessary for the existing geology. Further, evaluating the data gathered during the TS and PS can help in accurately estimating and executing full-scale operations. Invariably, deviations from the TS and PS regarding soil characteristics and soil chemistry may exist, but the experience gained via the TS and PS aids in making decisions when faced with new and unexpected conditions in the field. This paper will discuss the execution of typical TS and PS applications and their implementation for full-scale treatment. Because the long-term performance durability of design mixes and technology applications are not generally addressed in remediation, post-remediation monitoring and sampling data must be made available to the public to advance the science and art of stabilisation/solidification. As a first step in advancing this technology, this paper follows the lifecycle of stabilisation/ solidification projects from the site investigation through the completion of full-scale work. A 10-year post-remediation sampling event also evidences the long-term viability of the technology.

  2. On stabilisability of nonlinear systems on time scales

    NASA Astrophysics Data System (ADS)

    Bartosiewicz, Zbigniew; Piotrowska, Ewa

    2013-01-01

    In this article, stabilisability of nonlinear finite-dimensional control systems on arbitrary time scales is studied. The classical results on stabilisation of nonlinear continuous-time and discrete-time systems are extended to systems on arbitrary time scales with bounded graininess function. It is shown that uniform exponential stability of the linear approximation of a nonlinear system implies uniform exponential stability of the nonlinear system. Then this result is used to show a similar implication for uniform exponential stabilisability.

  3. Supergranular Convection

    NASA Astrophysics Data System (ADS)

    Udayashankar, Paniveni

    2015-12-01

    Observation of the Solar photosphere through high resolution instruments have long indicated that the surface of the Sun is not a tranquil, featureless surface but is beset with a granular appearance. These cellular velocity patterns are a visible manifestation of sub- photospheric convection currents which contribute substantially to the outward transport of energy from the deeper layers, thus maintaining the energy balance of the Sun as a whole.Convection is the chief mode of transport in the outer layers of all cool stars such as the Sun (Noyes,1982). Convection zone of thickness 30% of the Solar radius lies in the sub-photospheric layers of the Sun. Here the opacity is so large that heat flux transport is mainly by convection rather than by photon diffusion. Convection is revealed on four scales. On the scale of 1000 km, it is granulation and on the scale of 8-10 arcsec, it is Mesogranulation. The next hierarchial scale of convection , Supergranules are in the range of 30-40 arcsec. The largest reported manifestation of convection in the Sun are ‘Giant Cells’or ‘Giant Granules’, on a typical length scale of about 108 m.'Supergranules' is caused by the turbulence that extends deep into the convection zone. They have a typical lifetime of about 20hr with spicules marking their boundaries. Gas rises in the centre of the supergranules and then spreads out towards the boundary and descends.Broadly speaking supergranules are characterized by the three parameters namely the length L, the lifetime T and the horizontal flow velocity vh . The interrelationships amongst these parameters can shed light on the underlying convective processes and are in agreement with the Kolmogorov theory of turbulence as applied to large scale solar convection (Krishan et al .2002 ; Paniveni et. al. 2004, 2005, 2010).References:1) Noyes, R.W., The Sun, Our Star (Harvard University Press, 1982)2) Krishan, V., Paniveni U., Singh , J., Srikanth R., 2002, MNRAS, 334/1,2303) Paniveni

  4. Stabilisation of refraction following cataract surgery.

    PubMed Central

    Baranyovits, P R

    1988-01-01

    Refraction was performed at frequent, regular intervals for six months following routine intracapsular cataract extraction. Patients were divided into two groups, those whose limbal sections were closed with 8-0 virgin silk or with 9-0 nylon. The stabilisation of refraction was observed, and the most suitable time to prescribe 'first glasses' was estimated retrospectively. In the silk group this was found to be at three months in the nylon group at four months. However, results in the latter were less predictable with greater variation. PMID:3061448

  5. Convection towers

    DOEpatents

    Prueitt, Melvin L.

    1994-01-01

    Convection towers which are capable of cleaning the pollution from large quantities of air and of generating electricity utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity. Other embodiments may also provide fresh water, and operate in an updraft mode.

  6. Convection towers

    DOEpatents

    Prueitt, M.L.

    1996-01-16

    Convection towers which are capable of cleaning the pollution from large quantities of air, of generating electricity, and of producing fresh water utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity, and condensers produce fresh water. 6 figs.

  7. Convection towers

    DOEpatents

    Prueitt, Melvin L.

    1995-01-01

    Convection towers which are capable of cleaning the pollution from large quantities of air, of generating electricity, and of producing fresh water utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity, and condensers produce fresh water.

  8. Convection towers

    DOEpatents

    Prueitt, Melvin L.

    1996-01-01

    Convection towers which are capable of cleaning the pollution from large quantities of air, of generating electricity, and of producing fresh water utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity, and condensers produce fresh water.

  9. Modeling Convection

    ERIC Educational Resources Information Center

    Ebert, James R.; Elliott, Nancy A.; Hurteau, Laura; Schulz, Amanda

    2004-01-01

    Students must understand the fundamental process of convection before they can grasp a wide variety of Earth processes, many of which may seem abstract because of the scales on which they operate. Presentation of a very visual, concrete model prior to instruction on these topics may facilitate students' understanding of processes that are largely…

  10. Modeling Convection

    ERIC Educational Resources Information Center

    Ebert, James R.; Elliott, Nancy A.; Hurteau, Laura; Schulz, Amanda

    2004-01-01

    Students must understand the fundamental process of convection before they can grasp a wide variety of Earth processes, many of which may seem abstract because of the scales on which they operate. Presentation of a very visual, concrete model prior to instruction on these topics may facilitate students' understanding of processes that are largely…

  11. Aqueous foams stabilised solely by nanoparticles

    NASA Astrophysics Data System (ADS)

    Langevin, Dominique

    2011-03-01

    Particles are being increasingly used to stabilise foams and emulsions, the corresponding emulsions being known as ``Pickering'' emulsions. One of the peculiarities of these systems is the absence of Ostwald ripening: since the bubbles or drops do not grow (coalescence seems also suppressed) both foams and emulsions are stable over extremely long periods of time (months). These features make particles very interesting surface active agents as compared to standard surfactants or polymers/proteins. The origin of the suppression of ripening can be traced to the unusual behaviour of the interfacial layers made by these particles. The layers are solid-like and the usual characterisation methods (surface tension, surface rheology) are not straightforward to use. In this presentation, we will illustrate these difficulties with experiments made with partially hydrophobic silica nanoparticles. We will also discuss the relevance of foam characterisations methods such as multiple light scattering and X-ray tomography.

  12. Postural sway during retinal image stabilisation.

    PubMed

    Rushton, D N; Brandt, T; Paulus, W; Krafczyk, S

    1989-03-01

    Posturographic measurements using a piezoelectric platform were made in normal subjects while wearing a combination of spectacle and contact lens providing partial stabilisation of the retinal image (RIS). The amount of postural sway seen while wearing the device at rest is intermediate between the "normal vision" and "eyes closed" conditions, and increases with increasing amounts of RIS. However, when large active head-and-eye movements are performed, postural sway is dramatically increased when using RIS, and is then worse than while performing the same task in the "eyes closed" condition. It is concluded that patients who use the partial-RIS device for the treatment of severe oscillopsia may benefit only when performing tasks in which the head is relatively still, such as reading, writing or watching TV. It is also proposed that the partial-RIS device can serve as a model in normal free-standing subjects for the postural effects of oculomotor disorders.

  13. Convection towers

    DOEpatents

    Prueitt, M.L.

    1994-02-08

    Convection towers which are capable of cleaning the pollution from large quantities of air and of generating electricity utilize the evaporation of water sprayed into the towers to create strong airflows and to remove pollution from the air. Turbines in tunnels at the skirt section of the towers generate electricity. Other embodiments may also provide fresh water, and operate in an updraft mode. 5 figures.

  14. CONVECTION REACTOR

    DOEpatents

    Hammond, R.P.; King, L.D.P.

    1960-03-22

    An homogeneous nuclear power reactor utilizing convection circulation of the liquid fuel is proposed. The reactor has an internal heat exchanger looated in the same pressure vessel as the critical assembly, thereby eliminating necessity for handling the hot liquid fuel outside the reactor pressure vessel during normal operation. The liquid fuel used in this reactor eliminates the necessity for extensive radiolytic gas rocombination apparatus, and the reactor is resiliently pressurized and, without any movable mechanical apparatus, automatically regulates itself to the condition of criticality during moderate variations in temperature snd pressure and shuts itself down as the pressure exceeds a predetermined safe operating value.

  15. Stabilisation of second-order nonlinear equations with variable delay

    NASA Astrophysics Data System (ADS)

    Berezansky, Leonid; Braverman, Elena; Idels, Lev

    2015-08-01

    For a wide class of second-order nonlinear non-autonomous models, we illustrate that combining proportional state control with the feedback that is proportional to the derivative of the chaotic signal allows to stabilise unstable motions of the system. The delays are variable, which leads to more flexible controls permitting delay perturbations; only delay bounds are significant for stabilisation by a delayed control. The results are applied to the sunflower equation which has an infinite number of equilibrium points.

  16. Interference stabilisation of Rydberg atoms in a strong laser field

    SciTech Connect

    Fedorov, Mikhail V

    1999-07-31

    A review is given of the published theoretical and experimental investigations of the interference stabilisation of Rydberg atoms by a strong optical field. The physical nature of the effect, the models used to describe it, the alternative stabilisation mechanisms, and the extent to which the theoretical results match the published experimental data are discussed. (this issue is dedicated to the memory of s a akhmanov)

  17. Globally uniformly asymptotical stabilisation of time-delay nonlinear systems

    NASA Astrophysics Data System (ADS)

    Cai, Xiushan; Han, Zhengzhi; Zhang, Wei

    2011-07-01

    Globally uniformly asymptotical stabilisation of nonlinear systems in feedback form with a delay arbitrarily large in the input is dealt with based on the backstepping approach in this article. The design strategy depends on the construction of a Lyapunov-Krasovskii functional. A continuously differentiable control law is obtained to globally uniformly asymptotically stabilise the closed-loop system. The simulation shows the effectiveness of the method.

  18. Finding a stabilising switching law for switching nonlinear models

    NASA Astrophysics Data System (ADS)

    Lendek, Zs.; Raica, P.; Lauber, J.; Guerra, T. M.

    2016-09-01

    This paper considers the stabilisation of switching nonlinear models by switching between the subsystems. We assume that arbitrary switching between two subsystems is possible once a subsystem has been active for a predefined number of samples. We use a Takagi-Sugeno representation of the models and a switching Lyapunov function is employed to develop sufficient stability conditions. If the conditions are satisfied, we construct a switching law that stabilises the system. The application of the conditions is illustrated in several examples.

  19. Convective heater

    DOEpatents

    Thorogood, R.M.

    1983-12-27

    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. 14 figs.

  20. Convective heater

    DOEpatents

    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.

  1. Convective heater

    DOEpatents

    Thorogood, Robert M.

    1986-01-01

    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.

  2. Stabilisation of microalgae: Iodine mobilisation under aerobic and anaerobic conditions.

    PubMed

    Han, Wei; Clarke, William; Pratt, Steven

    2015-10-01

    Mobilisation of iodine during microalgae stabilisation was investigated, with the view of assessing the potential of stabilised microalgae as an iodine-rich fertiliser. An iodine-rich waste microalgae (0.35 ± 0.05 mg I g(-1) VS(added)) was stabilised under aerobic and anaerobic conditions. Iodine mobilisation was linearly correlated with carbon emission, indicating iodine was in the form of organoiodine. Comparison between iodine and nitrogen mobilisation relative to carbon emission indicated that these elements were, at least in part, housed separately within the cells. After stabilisation, there were 0.22 ± 0.05 and 0.19 ± 0.01 mg g(-1) VS(added) iodine remaining in the solid in the aerobic and anaerobic processed material respectively, meaning 38 ± 5.0% (aerobic) and 50 ± 8.6% (anaerobic) of the iodine were mobilised, and consequently lost from the material. The iodine content of the stabilised material is comparable to the iodine content of some seaweed fertilisers, and potentially satisfies an efficient I-fertilisation dose.

  3. Image stabilisation of the beating heart by local linear interpolation

    NASA Astrophysics Data System (ADS)

    Gröger, Martin; Hirzinger, Gerd

    2006-03-01

    The stabilisation of motion on the beating heart is investigated in the context of minimally invasive robotic surgery. Although reduced by mechanical stabilisers, residual tissue motion makes safe surgery still difficult and time consuming. Compensation for this movement is therefore highly desirable. Motion can be captured by tracking natural landmarks on the heart surface recorded by a video endoscope. Stabilisation is achieved by transforming the images using a motion field calculated from captured local motion. Since the surface of the beating heart is distorted nonlinearly, compensating the occurring motion with a constant image correction factor is not sufficient. Therefore, heart motion is captured by several landmarks, the motion between which is interpolated such that locally appropriate motion correction values are obtained. To estimate the motion between the landmark positions, a triangulation is built and motion information in each triangle is approximated by linear interpolation. Motion compensation is evaluated by calculating the optical flow remaining in the stabilised images. The proposed linear interpolation model is able to reduce motion significantly and can also be implemented efficiently to stabilise images of the beating heart in realtime.

  4. Southwick Osteotomy Stabilised with External Fixator

    PubMed Central

    Grubor, Predrag; Mitkovic, Milorad; Grubor, Milan

    2014-01-01

    ABSTRACT Introduction: Epiphysiolysis of the femoral head is the most common accident occurring towards the end of pre-puberty and puberty growth. Case report: The author describes the experience in the treatment of chronic epiphysiolysis in two patients treated by Southwick osteotomy. The site is accessed by way of a 15-cm long lateral skin incision and the trochanteric region is reached through the layers. The osteotomy angles prepared beforehand on a thin aluminium model are used to mark the Southwick osteotomy site on the anterior and lateral sides at the level of the lesser trochanter. Before performing the trochanteric osteotomy, two Mitković convergent pins type M20 are applied distally and proximally, above the planned osteotomy site. A tenotomy of the iliopsas muscle is performed, and then the previously marked bone triangle is redissected up to three quarters of the width of the femur. The distal part of the femur is rotated inwards, so that the patella is turned towards the ceiling. The osteotomised fragments of the femur are adapted, repositioned and fixated by installing an external fixator on the previously placed pins. Two more pins are placed, one proximally and one distally, with a view to adequately stabilising the femur. The patient was mobile from day two after the surgery. If, after the surgery, the lead surgeon realises that there is a requirement to make a correction of 5, 10 and 15 degrees of the valgus, varus, anteversion or retroversion deformity, the correction shall be performed without surgically opening the patient, using the fixator pins. Conclusion: After performing a Southwick osteotomy it is easier to adapt, reposition and fixate the osteotomised fragments of the femur using a fixator type M20. Adequate stability allows regaining mobility quickly, which in turn is the best prevention of chondrolysis of the hip. It is possible to make post-operative valgus, varus, anteversion and retroversion corrections of 5, 10 and 15 degrees

  5. Security for whom? Stabilisation and civilian protection in Colombia.

    PubMed

    Elhawary, Samir

    2010-10-01

    This paper focuses on three periods of stabilisation in Colombia: the Alliance for Progress (1961-73) that sought to stem the threat of communist revolution in Latin America; Plan Colombia and President Alvaro Uribe's 'democratic security' policy (2000-07) aimed at defeating the guerrillas and negotiating a settlement with the paramilitaries; and the current 'integrated approach', adopted from 2007, to consolidate more effectively the state's control of its territory.(1) The paper assesses the extent to which these stabilisation efforts have enhanced the protection of civilians and ultimately finds that in all three periods there has been a disconnect between the discourse and the practice of stabilisation. While they have all sought to enhance security, in actual fact, they have privileged the security of the state and its allies at the expense of the effective protection of the civilian population. This has not only led to widespread human rights abuses but also has undermined the long-term stability being pursued.

  6. Early metal bis(phosphorus-stabilised)carbene chemistry.

    PubMed

    Liddle, Stephen T; Mills, David P; Wooles, Ashley J

    2011-05-01

    Since the discovery of covalently-bound mid- and late-transition metal carbenes there has been a spectacular explosion of interest in their chemistry, but their early metal counterparts have lagged behind. In recent years, bis(phosphorus-stabilised)carbenes have emerged as valuable ligands for metals across the periodic table, and their use has in particular greatly expanded covalently-bound early metal carbene chemistry. In this tutorial review we introduce the reader to bis(phosphorus-stabilised)carbenes, and cover general preparative methods, structure and bonding features, and emerging reactivity studies of early metal derivatives (groups 1-4 and the f-elements).

  7. Bounded stabilisation of stochastic port-Hamiltonian systems

    NASA Astrophysics Data System (ADS)

    Satoh, Satoshi; Saeki, Masami

    2014-08-01

    This paper proposes a stochastic bounded stabilisation method for a class of stochastic port-Hamiltonian systems. Both full-actuated and underactuated mechanical systems in the presence of noise are considered in this class. The proposed method gives conditions for the controller gain and design parameters under which the state remains bounded in probability. The bounded region and achieving probability are both assignable, and a stochastic Lyapunov function is explicitly provided based on a Hamiltonian structure. Although many conventional stabilisation methods assume that the noise vanishes at the origin, the proposed method is applicable to systems under persistent disturbances.

  8. Organised convection embedded in a large-scale flow

    NASA Astrophysics Data System (ADS)

    Naumann, Ann Kristin; Stevens, Bjorn; Hohenegger, Cathy

    2017-04-01

    In idealised simulations of radiative convective equilibrium, convection aggregates spontaneously from randomly distributed convective cells into organized mesoscale convection despite homogeneous boundary conditions. Although these simulations apply very idealised setups, the process of self-aggregation is thought to be relevant for the development of tropical convective systems. One feature that idealised simulations usually neglect is the occurrence of a large-scale background flow. In the tropics, organised convection is embedded in a large-scale circulation system, which advects convection in along-wind direction and alters near surface convergence in the convective areas. A large-scale flow also modifies the surface fluxes, which are expected to be enhanced upwind of the convective area if a large-scale flow is applied. Convective clusters that are embedded in a large-scale flow therefore experience an asymmetric component of the surface fluxes, which influences the development and the pathway of a convective cluster. In this study, we use numerical simulations with explicit convection and add a large-scale flow to the established setup of radiative convective equilibrium. We then analyse how aggregated convection evolves when being exposed to wind forcing. The simulations suggest that convective line structures are more prevalent if a large-scale flow is present and that convective clusters move considerably slower than advection by the large-scale flow would suggest. We also study the asymmetric component of convective aggregation due to enhanced surface fluxes, and discuss the pathway and speed of convective clusters as a function of the large-scale wind speed.

  9. Microtubule stabilising peptides rescue tau phenotypes in-vivo

    PubMed Central

    Quraishe, Shmma; Sealey, Megan; Cranfield, Louise; Mudher, Amritpal

    2016-01-01

    The microtubule cytoskeleton is a highly dynamic, filamentous network underpinning cellular structure and function. In Alzheimer’s disease, the microtubule cytoskeleton is compromised, leading to neuronal dysfunction and eventually cell death. There are currently no disease-modifying therapies to slow down or halt disease progression. However, microtubule stabilisation is a promising therapeutic strategy that is being explored. We previously investigated the disease-modifying potential of a microtubule-stabilising peptide NAP (NAPVSIPQ) in a well-established Drosophila model of tauopathy characterised by microtubule breakdown and axonal transport deficits. NAP prevented as well as reversed these phenotypes even after they had become established. In this study, we investigate the neuroprotective capabilities of an analogous peptide SAL (SALLRSIPA). We found that SAL mimicked NAP’s protective effects, by preventing axonal transport disruption and improving behavioural deficits, suggesting both NAP and SAL may act via a common mechanism. Both peptides contain a putative ‘SIP’ (Ser-Ile-Pro) domain that is important for interactions with microtubule end-binding proteins. Our data suggests this domain may be central to the microtubule stabilising function of both peptides and the mechanism by which they rescue phenotypes in this model of tauopathy. Our observations support microtubule stabilisation as a promising disease-modifying therapeutic strategy for tauopathies like Alzheimer’s disease. PMID:27910888

  10. Transpatellar access for intramedullary stabilisation of the tibia.

    PubMed

    Gerich, T; Backes, F; Pape, D; Seil, R

    2012-01-01

    Postoperative deformities of the knee and sequaelae after intraarticular surgery can interfere with a standard parapetallar approach for intramedullary stabilisation of the tibia. Even the suprapatellar approach can be rendered impossible. For these rare indications we describe the patella osteotomy and transpatellar approach.

  11. Strong stabilisation and decay estimate for unbounded bilinear systems

    NASA Astrophysics Data System (ADS)

    El Ayadi, R.; Ouzahra, M.; Boutoulout, A.

    2012-10-01

    In this article, we deal with distributed bilinear systems, where the operator of control is supposed to be unbounded in the sense that it is bounded from the state space into some extension. Then we give sufficient conditions for strong stabilisation. Also the rate of convergence of the state is estimated. An illustrating example is given.

  12. Frequency-stabilised external-cavity semiconductor laser

    SciTech Connect

    Permyakova, O I; Yakovlev, A V; Chapovskii, Pavel L

    2005-05-31

    The design and characteristics of a semiconductor laser with the modified external Littrow resonator are described. The additional output mirror of the V-shaped resonator made the system more efficient and convenient. The laser radiation frequency is stabilised with the help of magnetooptical Faraday and circular dichroism effects in rubidium vapour. (diode lasers)

  13. Feedback-bounded stabilisation of certain discrete Volterra systems

    NASA Astrophysics Data System (ADS)

    Kotsios, Stelios

    2016-06-01

    Throughout this paper, we present a method for designing feedback-laws which stabilise nonlinear discrete Volterra systems. Our method is based on a factorisation algorithm which decomposes the original system as a composition of a δ-polynomial and a linear series.

  14. Exponential passivity for output feedback stabilisation of nonlinear uncertain systems

    NASA Astrophysics Data System (ADS)

    Benabdallah, Amel

    2010-11-01

    In this article, we address the problem of stabilisation by output feedback for a class of uncertain systems. We consider uncertain systems with a nominal part which is affine in the control and an uncertain part which is norm bounded by a known function. We propose an output feedback such that the closed loop system is globally exponentially stable.

  15. Food-grade Pickering emulsions stabilised with solid lipid particles.

    PubMed

    Pawlik, Aleksandra; Kurukji, Daniel; Norton, Ian; Spyropoulos, Fotis

    2016-06-15

    Aqueous dispersions of tripalmitin particles (with a minimum size of 130 nm) were produced, via a hot sonication method, with and without the addition of food-grade emulsifiers. Depending on their relative size and chemistry, the emulsifiers altered the properties of the fat particles (e.g. crystal form, dispersion state and surface properties) by two proposed mechanisms. Firstly, emulsifiers modify the rate and/or extent of polymorphic transitions, resulting in the formation of fat crystals with a range of polarities. Secondly, the adsorption of emulsifiers at the particle interface modifies crystal surface properties. Such emulsifier-modified fat particles were then used to stabilise emulsions. As the behaviour of these particles was predisposed by the kind of emulsifier employed for their manufacture, the resulting particles showed different preferences to which of the emulsion phases (oil or water) became the continuous one. The polarity of the fat particles decreased as follows: Whey Protein Isolate > Soy Lecithin > Soy Lecithin + Tween 20 > Tween 20 > Polyglycerol Polyricinoleate > no emulsifier. Consequently, particles stabilised with WPI formed oil-in-water emulsions (O/W); particles stabilised solely with lecithin produced a highly unstable W/O emulsion; and particles stabilised with a mixture of lecithin and Tween 20 gave a stable W/O emulsion with drop size up to 30 μm. Coalescence stable, oil-continuous emulsions (W/O) with drop sizes between 5 and 15 μm were produced when the tripalmitin particles were stabilised with solely with Tween 20, solely with polyglycerol polyricinoleate, or with no emulsifier at all. It is proposed that the stability of the latter three emulsions was additionally enhanced by sintering of fat particles at the oil-water interface, providing a mechanical barrier against coalescence.

  16. Effect of addition of GGBS and lime in soil stabilisation for stabilising local village roads in Thanjavur region

    NASA Astrophysics Data System (ADS)

    Saravanan, R.; Udhayakumar, T.; Dinesh, S.; Venkatasubramanian, C.; Muthu, D.

    2017-07-01

    Construction of pavements uses various filling materials and due to the cost factor, the local soil is used for pavement construction. The strength of the soil is improved by stabilisation. This stabilisation increases the load bearing capacities of soil for heavy wheeled vehicle traffic. GGBS, silica fume, rice husk are the basic waste materials used as a waste material, which improves the quality of soil and reduces the cost of pavements. In this study, a detailed investigation is made on the Ground Granulated Blast-furnace Slag (GGBS), activated by lime, in the stabilisation of low bearing capacity sand and clay soils collected from Thanjavur district (Budalur, Sengipatti, Vallam and Palliahgraharam villages). The tests are carried out as per Indian Standards. The test procedures separated into two phases, namely Stage-I and Stage-II. In Stage-I the soil tests include soil type, particle size distribution, soil index properties, standard proctor tests, shear tests and CBR test. In Stage-II the soil tests include shear tests and CBR test for the suitable required proportions of GGBS along with lime in the collected soil samples. The test results from stage-I and stage-II are compared and from the study, it is inferred that the application of GGBS is a useful material for soil stabilisation.

  17. Mimicking semi-convection by convective overshooting

    NASA Astrophysics Data System (ADS)

    Caloi, V.; Mazzitelli, I.

    1990-12-01

    This paper investigates the behavior of so called 'semiconvection' (described by Schwarzschild, 1970; Castellani et al., 1971), of stars burning He in a convective core but exibiting an apparent spontaneous capability to partially mix into the core the matter from outside the formal boundaries of the convective region. A simple numerical algorithm based on a small and ad hoc amount of convective overshooting is presented which, if properly tuned, can mimick the effect of semiconvection in the computation of those stellar evolutionary phases in which a convective helium burning core is present. Using this algorithm, the time-consuming numerical procedures involved in the evaluation of the correct chemical profiles at the boundaries of the formally convective He core can be avoided.

  18. 1991 LANL Mantle Convection Workshop

    NASA Astrophysics Data System (ADS)

    Gable, Carl W.; Kincaid, Chris

    1992-04-01

    Since 1985, Los Alamos National Laboratory's (LANL) Institute of Geophysics and Planetary Physics (IGPP) has hosted a mantle convection workshop. Each year, senior scientists and graduate students meet for 2 weeks of formal and informal presentations and hands-on working groups. The workshop format has been to define focus topics and activities which are discussed in small subgroups. Focus group reports are then made to summarize previous work and define avenues of future research on specific topics. From July 8 to 19, 1991, the primary focus of discussion was mantle plumes. Mantle discontinuities and the effect of tectonic plates upon mantle convection were focus topics in previous workshops. Additional focus topics for this workshop included the differences between 2D and 3D convection and a discussion of benchmark problems for the European convection workshop, held in August 1991 in Weilburg, Germany. In addition to presentations, focus group reports, and the exchange of ideas by geodynamics researchers, a number of guest speakers from related fields helped provide background on relevant model constraints, motivate discussion, and promote communication between fields.

  19. Soret and Dufour effects on thermohaline convection in rotating fluids

    NASA Astrophysics Data System (ADS)

    Duba, C. T.; Shekar, M.; Narayana, M.; Sibanda, P.

    2016-07-01

    Using linear and weakly nonlinear stability theory, the effects of Soret and Dufour parameters are investigated on thermohaline convection in a horizontal layer of rotating fluid, specifically the ocean. Thermohaline circulation is important in mixing processes and contributes to heat and mass transports and hence the earth's climate. A general conception is that due to the smallness of the Soret and Dufour parameters their effect is negligible. However, it is shown here that the Soret parameter, salinity and rotation stabilise the system, whereas temperature destabilises it and the Dufour parameter has minimal effect on stationary convection. For oscillatory convection, the analysis is difficult as it shows that the Rayleigh number depends on six parameters, the Soret and Dufour parameters, the salinity Rayleigh number, the Lewis number, the Prandtl number, and the Taylor number. We demonstrate the interplay between these parameters and their effects on oscillatory convection in a graphical manner. Furthermore, we find that the Soret parameter enhances oscillatory convection whereas the Dufour parameter, salinity Rayleigh number, the Lewis number, and rotation delay instability. We believe that these results have not been elucidated in this way before for large-scale fluids. Furthermore, we investigate weakly nonlinear stability and the effect of cross diffusive terms on heat and mass transports. We show the existence of new solution bifurcations not previously identified in literature.

  20. Deoxycholate-Based Glycosides (DCGs) for Membrane Protein Stabilisation.

    PubMed

    Bae, Hyoung Eun; Gotfryd, Kamil; Thomas, Jennifer; Hussain, Hazrat; Ehsan, Muhammad; Go, Juyeon; Loland, Claus J; Byrne, Bernadette; Chae, Pil Seok

    2015-07-06

    Detergents are an absolute requirement for studying the structure of membrane proteins. However, many conventional detergents fail to stabilise denaturation-sensitive membrane proteins, such as eukaryotic proteins and membrane protein complexes. New amphipathic agents with enhanced efficacy in stabilising membrane proteins will be helpful in overcoming the barriers to studying membrane protein structures. We have prepared a number of deoxycholate-based amphiphiles with carbohydrate head groups, designated deoxycholate-based glycosides (DCGs). These DCGs are the hydrophilic variants of previously reported deoxycholate-based N-oxides (DCAOs). Membrane proteins in these agents, particularly the branched diglucoside-bearing amphiphiles DCG-1 and DCG-2, displayed favourable behaviour compared to previously reported parent compounds (DCAOs) and conventional detergents (LDAO and DDM). Given their excellent properties, these agents should have significant potential for membrane protein studies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Gas gain stabilisation in the ATLAS TRT detector

    NASA Astrophysics Data System (ADS)

    Mindur, B.; Åkesson, T. P. A.; Anghinolfi, F.; Antonov, A.; Arslan, O.; Baker, O. K.; Banas, E.; Bault, C.; Beddall, A. J.; Bendotti, J.; Benjamin, D. P.; Bertelsen, H.; Bingul, A.; Bocci, A.; Boldyrev, A. S.; Brock, I.; Capeáns Garrido, M.; Catinaccio, A.; Celebi, E.; Cetin, S. A.; Choi, K.; Dam, M.; Danielsson, H.; Davis, D.; Degeorge, C.; Derendarz, D.; Desch, K.; Di Girolamo, B.; Dittus, F.; Dixon, N.; Dressnandt, N.; Dubinin, F. A.; Evans, H.; Farthouat, P.; Fedin, O. L.; Froidevaux, D.; Gavrilenko, I. L.; Gay, C.; Gecse, Z.; Godlewski, J.; Grefe, C.; Gurbuz, S.; Hajduk, Z.; Hance, M.; Haney, B.; Hansen, J. B.; Hansen, P. H.; Hawkins, A. D.; Heim, S.; Holway, K.; Kantserov, V. A.; Katounine, S.; Kayumov, F.; Keener, P. T.; Kisielewski, B.; Klopov, N. V.; Konovalov, S. P.; Koperny, S.; Korotkova, N. A.; Kowalski, T. Z.; Kramarenko, V.; Krasnopevtsev, D.; Kruse, M.; Kudin, L. G.; Lichard, P.; Loginov, A.; Martinez, N. Lorenzo; Lucotte, A.; Luehring, F.; Lytken, E.; Maleev, V. P.; Maevskiy, A. S.; Manjarres Ramos, J.; Mashinistov, R. Y.; Meyer, C.; Mialkovski, V.; Mistry, K.; Mitsou, V. A.; Nadtochi, A. V.; Newcomer, F. M.; Novodvorski, E. G.; Ogren, H.; Oh, S. H.; Oleshko, S. B.; Olszowska, J.; Ostrowicz, W.; Palacino, G.; Patrichev, S.; Penwell, J.; Perez-Gomez, F.; Peshekhonov, V. D.; RØhne, O.; Reilly, M. B.; Rembser, C.; Ricken, O.; Romaniouk, A.; Rousseau, D.; Ryjov, V.; Sasmaz, U.; Schaepe, S.; Schegelsky, V. A.; Shmeleva, A. P.; Shulga, E.; Sivoklokov, S.; Smirnov, S.; Smirnov, Yu.; Smirnova, L. N.; Soldatov, E.; Sulin, V. V.; Tartarelli, G.; Taylor, W.; Thomson, E.; Tikhomirov, V. O.; Tipton, P.; Valls Ferrer, J. A.; Van Berg, R.; Vasquez, J.; Vasilyeva, L. F.; Vlazlo, O.; Weinert, B.; Williams, H. H.; Wong, V.; Zhukov, K. I.; Zieminska, D.

    2016-04-01

    The ATLAS (one of two general purpose detectors at the LHC) Transition Radiation Tracker (TRT) is the outermost of the three tracking subsystems of the ATLAS Inner Detector. It is a large straw-based detector and contains about 350,000 electronics channels. The performance of the TRT as tracking and particularly particle identification detector strongly depends on stability of the operation parameters with most important parameter being the gas gain which must be kept constant across the detector volume. The gas gain in the straws can vary significantly with atmospheric pressure, temperature, and gas mixture composition changes. This paper presents a concept of the gas gain stabilisation in the TRT and describes in detail the Gas Gain Stabilisation System (GGSS) integrated into the Detector Control System (DCS). Operation stability of the GGSS during Run-1 is demonstrated.

  2. Use of Reinforced Lightweight Clay Aggregates for Landslide Stabilisation

    SciTech Connect

    Herle, Vitezslav

    2008-07-08

    In spring 2006 a large landslide combined with rock fall closed a highway tunnel near Svitavy in NE part of Czech Republic and cut the main highway connecting Bohemia with Moravia regions. Stabilisation work was complicated by steep mountainous terrain and large inflow of surface and underground water. The solution was based on formation of a stabilisation fill made of reinforced free draining aggregates at the toe of the slope with overlying lightweight fill up to 10 m high reinforced with PET geogrid and steel mesh protecting soft easily degrading sandstone against weathering. Extensive monitoring made possible to compare the FEM analysis with real values. The finished work fits very well in the environment and was awarded a special prize in the 2007 transport structures contest.

  3. [A difficult stabilisation. Chlorpromazine in the fifties in Belgium].

    PubMed

    Majerus, Benoît

    2010-01-01

    Through a Belgian case study the article tries to trace the gradual stabilisation of chlorpromazine as an antipsychotic in the 1950s. By varying ranges and angles of approach it shows the heterogeneity of actors involved and the semantic bricolage that accompany the marketing of the first antipsychotic. Far from being a revolution, the presence of Largactil in psychiatric practice is rather characterised by integration into a wider range of medicines and sinuous searching to give sense to this new drug.

  4. Stabilisation of scoliosis in two koi (Cyprinus carpio).

    PubMed

    Govett, P D; Olby, N J; Marcellin-Little, D J; Rotstein, D S; Reynolds, T L; Lewbart, G A

    2004-07-24

    Two koi (Cyprinus carpio) from the same pond developed similar lesions of scoliosis. Radiographic examinations showed that their spines had become malaligned as a result of vertebral compression fractures involving T14 to T16. The vertebrae in both fish were stabilised with screws, k-wire and polymethylmethacrylate. They both appeared to improve after surgery, but they began to decline and died within three months. A postmortem examination revealed multi-organ inflammation that was not associated with the surgical implants.

  5. Preliminary stabilisation of stormwater biofilters and loss of filter material.

    PubMed

    Subramaniam, D N; Mather, P B

    Stabilisation affects performance of stormwater biofilters operating under intermittent wetting and drying, mainly due to wash-off of filter material. Understanding the dynamics of solids wash-off is crucial in designing stormwater biofilters. The current study analysed the dynamics of solids wash-off in stormwater biofilters and quantified the loss of solids from the filter. Four Perspex™ bioretention columns (94 mm internal diameter) were fabricated with a filter layer that contained 8% organic material and were fed with tap water with different numbers of antecedent dry days (0-40 day) at 100 mL/min. Samples were collected from the outflow and tested for particle size distribution and total solids and turbidity. Solids of particle size less than 50 microns were washed off from the filter during the stabilisation period, indicating that no sand particles were washed off. The very first event after commissioning the filter resulted in the highest wash-off of solids (approximately 75 g of fines) while a significant drop in wash-off followed from the second event. An empirical model fitted to the data showed that preliminary stabilisation of a filter occurs in the first three events, during which almost 25% of fines are lost from the filter.

  6. Non-overshooting stabilisation via state and output feedback

    NASA Astrophysics Data System (ADS)

    Halikias, G.; Papageorgiou, A.; Karcanias, N.

    2010-06-01

    The concept of 'strong stability' of linear time-invariant (LTI) systems has been introduced in a recent paper (Karcanias, N., Halikias, G., and Papageorgiou, A. (2010), 'Strong Stability of Internal System Descriptions', International Journal of Control, 83, 182-205). This is a stronger notion of stability compared to alternative definitions (e.g. stability in the sense of Lyapunov, asymptotic stability), which allows the analysis and design of control systems with non-overshooting response in the state-space for arbitrary initial conditions. This article reviews the notion of 'strong stability' (Karcanias et al. 2010) and introduces the problem of non-overshooting stabilisation. It is shown that non-overshooting stabilisation under dynamic and static output feedback are, in a certain sense, equivalent problems. Thus, we turn our attention to static non-overshooting stabilisation problems under state-feedback, output injection and output feedback. After developing a number of preliminary results, we give a geometric interpretation to the problem in terms of the intersection of an affine hyperplane and the interior of an open convex cone. A solution to the problem is finally obtained via linear matrix inequalities, along with the complete parameterisation of the optimal solution set.

  7. Oxidation behaviour of uranium and neptunium in stabilised zirconia

    NASA Astrophysics Data System (ADS)

    Walter, Marcus; Somers, Joseph; Bouëxière, Daniel; Gaczyński, Piotr; Brendebach, Boris

    2009-12-01

    Yttria stabilised zirconia (YSZ) based (Zr,Y,U)O 2-x and (Zr,Y,Np)O 2-x solid solutions with 6 and 20 mol% actinide were prepared with Y/Zr ratios ranging from 0.2 to 2.0 to investigate uranium and neptunium oxidation behaviour depending on the oxygen vacancies in the defect fluorite lattice. Sintering at 1600 °C in Ar/H 2 yields a cubic, fluorite-type structure with U(IV) and Np(IV). Annealing (Zr,Y,U)O 2-x with Y/Zr=0.2 at 800 °C in air results in a tetragonal phase, whereas (Zr,Y,U)O 2-x with higher Y/Zr ratios and (Zr,Y,Np)O 2-x retain the cubic structure. XANES and O/ M measurements indicate mixed U(V)-U(VI) and Np(IV)-Np(V) oxidation states after oxidation. Based on X-ray diffraction, O/ M and EXAFS measurements, different oxidation mechanisms are identified for U- and Np-doped stabilised zirconia. In contrast to U, excess oxygen vacancies are needed to oxidise Np in (Zr,Y,Np)O 2-x as the oxidation process competes with Zr for oxygen vacancies. As a consequence, U(VI) and Np(V) can only be obtained in stabilised zirconia with Y/Zr=1 but not in YSZ with Y/Zr=0.2.

  8. Antipsychotics, mood stabilisers, and risk of violent crime.

    PubMed

    Fazel, Seena; Zetterqvist, Johan; Larsson, Henrik; Långström, Niklas; Lichtenstein, Paul

    2014-09-27

    Antipsychotics and mood stabilisers are prescribed widely to patients with psychiatric disorders worldwide. Despite clear evidence for their efficacy in relapse prevention and symptom relief, their effect on some adverse outcomes, including the perpetration of violent crime, is unclear. We aimed to establish the effect of antipsychotics and mood stabilisers on the rate of violent crime committed by patients with psychiatric disorders in Sweden. We used linked Swedish national registers to study 82,647 patients who were prescribed antipsychotics or mood stabilisers, their psychiatric diagnoses, and subsequent criminal convictions in 2006-09. We did within-individual analyses to compare the rate of violent criminality during the time that patients were prescribed these medications versus the rate for the same patients while they were not receiving the drugs to adjust for all confounders that remained constant within each participant during follow-up. The primary outcome was the occurrence of violent crime, according to Sweden's national crime register. In 2006-09, 40,937 men in Sweden were prescribed antipsychotics or mood stabilisers, of whom 2657 (6·5%) were convicted of a violent crime during the study period. In the same period, 41,710 women were prescribed these drugs, of whom 604 (1·4 %) had convictions for violent crime. Compared with periods when participants were not on medication, violent crime fell by 45% in patients receiving antipsychotics (hazard ratio [HR] 0·55, 95% CI 0·47-0·64) and by 24% in patients prescribed mood stabilisers (0·76, 0·62-0·93). However, we identified potentially important differences by diagnosis-mood stabilisers were associated with a reduced rate of violent crime only in patients with bipolar disorder. The rate of violence reduction for antipsychotics remained between 22% and 29% in sensitivity analyses that used different outcomes (any crime, drug-related crime, less severe crime, and violent arrest), and was stronger in

  9. Convective Available Potential Energy of World Ocean

    NASA Astrophysics Data System (ADS)

    Su, Z.; Ingersoll, A. P.; Thompson, A. F.

    2012-12-01

    Here, for the first time, we propose the concept of Ocean Convective Available Potential Energy (OCAPE), which is the maximum kinetic energy (KE) per unit seawater mass achievable by ocean convection. OCAPE occurs through a different mechanism from atmospheric CAPE, and involves the interplay of temperature and salinity on the equation of state of seawater. The thermobaric effect, which arises because the thermal coefficient of expansion increases with depth, is an important ingredient of OCAPE. We develop an accurate algorithm to calculate the OCAPE for a given temperature and salinity profile. We then validate our calculation of OCAPE by comparing it with the conversion of OCAPE to KE in a 2-D numerical model. We propose that OCAPE is an important energy source of ocean deep convection and contributes to deep water formation. OCAPE, like Atmospheric CAPE, can help predict deep convection and may also provide a useful constraint for modelling deep convection in ocean GCMs. We plot the global distribution of OCAPE using data from the World Ocean Atlas 2009 (WOA09) and see many important features. These include large values of OCAPE in the Labrador, Greenland, Weddell and Mediterranean Seas, which are consistent with our present observations and understanding, but also identify some new features like the OCAPE pattern in the Antarctic Circumpolar Current (ACC). We propose that the diagnosis of OCAPE can improve our understanding of global patterns of ocean convection and deep water formation as well as ocean stratification, the meridional overturning circulation and mixed layer processes. The background of this work is briefly introduced as below. Open-ocean deep convection can significantly modify water properties both at the ocean surface and throughout the water column (Gordon 1982). Open-ocean convection is also an important mechanism for Ocean Deep Water formation and the transport of heat, freshwater and nutrient (Marshall and Schott 1999). Open

  10. Modeling ocean deep convection

    NASA Astrophysics Data System (ADS)

    Canuto, V. M.; Howard, A.; Hogan, P.; Cheng, Y.; Dubovikov, M. S.; Montenegro, L. M.

    The goal of this study is to assess models for Deep Convection with special emphasis on their use in coarse resolution ocean general circulation models. A model for deep convection must contain both vertical transport and lateral advection by mesoscale eddies generated by baroclinic instabilities. The first process operates mostly in the initial phases while the second dominates the final stages. Here, the emphasis is on models for vertical mixing. When mesoscales are not resolved, they are treated with the Gent and McWilliams parameterization. The model results are tested against the measurements of Lavender, Davis and Owens, 2002 (LDO) in the Labrador Sea. Specifically, we shall inquire whether the models are able to reproduce the region of " deepest convection," which we shall refer to as DC (mixed layer depths 800-1300 m). The region where it was measured by Lavender et al. (2002) will be referred to as the LDO region. The main results of this study can be summarized as follows. 3° × 3° resolution. A GFDL-type OGCM with the GISS vertical mixing model predicts DC in the LDO region where the vertical heat diffusivity is found to be 10 m 2 s -1, a value that is quite close to the one suggested by heuristic studies. No parameter was changed from the original GISS model. However, the GISS model also predicts some DC in a region to the east of the LDO region. 3° × 3° resolution. A GFDL-type OGCM with the KPP model (everything else being the same) does not predict DC in the LDO region where the vertical heat diffusivity is found to be 0.5 × 10 -4 m 2 s -1 which is the background value. The KPP model yields DC only to the east of the LDO region. 1° × 1° resolution. In this case, a MY2.5 mixing scheme predicts DC in the LDO region. However, it also predicts DC to the west, north and south of it, where it is not observed. The behavior of the KPP and MY models are somewhat anti-symmetric. The MY models yield too low a mixing in stably stratified flows since they

  11. Oscillatory thermocapillary convection

    NASA Technical Reports Server (NTRS)

    Mundrane, Michael R.; Zebib, Abdelfattah

    1994-01-01

    We study thermocapillary and buoyant thermocapillary convection in rectangular cavities with aspect ratio A = 4 and Pr = 0.015. Two separate problems are considered. The first is combined buoyant thermocapillary convection with a nondeforming interface. We establish neutral curves for transition to oscillatory convection in the Re-Gr plane. It is shown that while pure buoyant convection exhibits oscillatory behavior for Gr is greater than Gr(sub cr) (where Gr(sub cr) is defined for the pure buoyant problem), pure thermocapillary convection is steady within the range of parameters tested. In the second problem, we consider the influence of surface deformation on the pure thermocapillary problem. For the range of parameters considered, thermocapillary convection remained steady.

  12. Mechanisms of flame stabilisation at low lifted height in a turbulent lifted slot-jet flame

    DOE PAGES

    Karami, Shahram; Hawkes, Evatt R.; Talei, Mohsen; ...

    2015-07-23

    A turbulent lifted slot-jet flame is studied using direct numerical simulation (DNS). A one-step chemistry model is employed with a mixture-fraction-dependent activation energy which can reproduce qualitatively the dependence of the laminar burning rate on the equivalence ratio that is typical of hydrocarbon fuels. The basic structure of the flame base is first examined and discussed in the context of earlier experimental studies of lifted flames. Several features previously observed in experiments are noted and clarified. Some other unobserved features are also noted. Comparison with previous DNS modelling of hydrogen flames reveals significant structural differences. The statistics of flow andmore » relative edge-flame propagation velocity components conditioned on the leading edge locations are then examined. The results show that, on average, the streamwise flame propagation and streamwise flow balance, thus demonstrating that edge-flame propagation is the basic stabilisation mechanism. Fluctuations of the edge locations and net edge velocities are, however, significant. It is demonstrated that the edges tend to move in an essentially two-dimensional (2D) elliptical pattern (laterally outwards towards the oxidiser, then upstream, then inwards towards the fuel, then downstream again). It is proposed that this is due to the passage of large eddies, as outlined in Suet al.(Combust. Flame, vol. 144 (3), 2006, pp. 494–512). However, the mechanism is not entirely 2D, and out-of-plane motion is needed to explain how flames escape the high-velocity inner region of the jet. Finally, the time-averaged structure is examined. A budget of terms in the transport equation for the product mass fraction is used to understand the stabilisation from a time-averaged perspective. The result of this analysis is found to be consistent with the instantaneous perspective. The budget reveals a fundamentally 2D structure, involving transport in both the streamwise and transverse

  13. Mechanisms of flame stabilisation at low lifted height in a turbulent lifted slot-jet flame

    SciTech Connect

    Karami, Shahram; Hawkes, Evatt R.; Talei, Mohsen; Chen, Jacqueline H.

    2015-07-23

    A turbulent lifted slot-jet flame is studied using direct numerical simulation (DNS). A one-step chemistry model is employed with a mixture-fraction-dependent activation energy which can reproduce qualitatively the dependence of the laminar burning rate on the equivalence ratio that is typical of hydrocarbon fuels. The basic structure of the flame base is first examined and discussed in the context of earlier experimental studies of lifted flames. Several features previously observed in experiments are noted and clarified. Some other unobserved features are also noted. Comparison with previous DNS modelling of hydrogen flames reveals significant structural differences. The statistics of flow and relative edge-flame propagation velocity components conditioned on the leading edge locations are then examined. The results show that, on average, the streamwise flame propagation and streamwise flow balance, thus demonstrating that edge-flame propagation is the basic stabilisation mechanism. Fluctuations of the edge locations and net edge velocities are, however, significant. It is demonstrated that the edges tend to move in an essentially two-dimensional (2D) elliptical pattern (laterally outwards towards the oxidiser, then upstream, then inwards towards the fuel, then downstream again). It is proposed that this is due to the passage of large eddies, as outlined in Suet al.(Combust. Flame, vol. 144 (3), 2006, pp. 494–512). However, the mechanism is not entirely 2D, and out-of-plane motion is needed to explain how flames escape the high-velocity inner region of the jet. Finally, the time-averaged structure is examined. A budget of terms in the transport equation for the product mass fraction is used to understand the stabilisation from a time-averaged perspective. The result of this analysis is found to be consistent with the instantaneous perspective. The budget reveals a fundamentally 2D structure, involving transport in both

  14. Stability and stabilisation of linear multidimensional discrete systems in the frequency domain

    NASA Astrophysics Data System (ADS)

    Li, Lizhen; Xu, Li; Lin, Zhiping

    2013-11-01

    This paper gives a reasonably detailed review of advances in stability and stabilisation of linear multidimensional (N-D) discrete systems in the frequency domain. The emphasis is on the recent progress, especially in the past decade. The discussion will focus on two topics: (i) stability test. Determination of whether a given N-D (N ≥ 2) system is stable; (ii) stabilisation. Parameterisation of all stabilising compensators for a stabilisable N-D system. After reviewing the progress and several state of the art methods in these two topics with illustrative examples, some related issues are also briefly mentioned at the end.

  15. Interplay between body stabilisation and quadriceps muscle activation capacity.

    PubMed

    Bampouras, Theodoros M; Reeves, Neil D; Baltzopoulos, Vasilios; Maganaris, Constantinos N

    2017-03-22

    The study aimed to distinguish the effect of stabilisation and muscle activation on quadriceps maximal isometric voluntary contraction (MVC) torque generation. Nine subjects performed (a) an MVC with restrained leg and pelvis (Typical MVC), (b) a Typical MVC with handgrip (Handgrip MVC), (c) an MVC focusing on contracting the knee extensors only (Isolated knee extension MVC), and (d) an MVC with unrestrained leg and pelvis (Unrestrained MVC). Torque and activation capacity between conditions were compared with repeated measures ANOVA and dependent t-tests. EMG (from eleven remote muscles) was compared using Friedman's and Wilcoxon. Typical MVC (277.2±49.6Nm) and Handgrip MVC (261.0±55.4Nm) were higher than Isolated knee extension MVC (210.2±48.3Nm, p<0.05) and Unrestrained MVC (195.2±49.7Nm, p<0.05) torque. Typical MVC (83.1±15.9%) activation was higher than Isolated knee extension MVC (68.9±24.3%, p<0.05), and both Typical MVC and Handgrip MVC (81.8±17.4%) were higher than Unrestrained MVC (64.9±16.2%, p<0.05). Only flexor carpi radialis, biceps brachii, triceps brachii and external oblique muscles showed EMG differences, with Isolated knee extension MVC consistently lower than Typical MVC or Handgrip MVC. Stabilisation of the involved segments is the prime concern allowing fuller activation of the muscle, reinforcing the need for close attention to stabilisation during dynamometry-based knee joint functional assessment.

  16. Viscoelastic properties of sterically stabilised emulsions and their stability.

    PubMed

    Tadros, Tharwat

    2015-08-01

    The interaction forces between emulsion droplets containing adsorbed polymeric surfactants and the theory of steric stabilisation are briefly described. The results for the viscoelastic properties of O/W emulsions that are stabilised with partially hydrolysed poly(vinyl acetate) that is commonly referred to as poly(vinyl alcohol) (PVA) with 4% vinyl acetate are given. The effect of the oil volume fraction, addition of electrolytes and increasing temperature is described. This allows one to obtain various parameters such as the adsorbed layer thickness, the critical flocculation concentration of electrolyte (CFC) and critical flocculation temperature (CFT) at constant electrolyte concentration. The viscoelastic properties of O/W emulsions stabilised with an A-B-A block copolymer of polyethylene oxide (A) and polypropylene oxide (B) are described. These emulsions behave as viscoelastic liquids showing a cross-over-point between G' (the elastic component of the complex modulus) and G″ (the viscous component of the complex modulus) at a characteristic frequency. Plots of G' and G″ versus oil volume fraction ϕ show the transition from predominantly viscous to predominantly elastic response at a critical volume fraction ϕ(c). The latter can be used to estimate the adsorbed layer thickness of the polymeric surfactants. Results are also shown for W/O emulsions stabilised with an A-B-A block copolymer of polyhydroxystearic acid (PHS, A) and polyethylene oxide (PEO, B). The viscosity volume fraction curves could be fitted to the Dougherty-Krieger equation for hard-spheres. The results could be applied to give an estimate of the adsorbed layer thickness Δ which shows a decrease with increase of the water volume fraction. This is due to the interpenetration and/or compression of the PHS layers on close approach of the water droplets on increasing the water volume fraction. The last section of the review gives an example of O/W emulsion stability using an AB(n) graft

  17. Stabilised electromagnetic levitation at 2-13 MHz

    NASA Technical Reports Server (NTRS)

    Danley, T. J.; Schiffman, R. A.; Weber, J. K. R.; Krishnan, S.; Rey, C. A.; Bruno, P. A.; Nordine, P. C.

    1991-01-01

    SEL, the Stabilised Electromagnetic Levitator, has been developed to exploit the unique design opportunities available in containerless microgravity experiments. Efficiency and versatility are obtained with multiple coils driven by individual broadband amplifiers whose phase and frequency are controlled. The heating and positioning fields are decoupled. Specimen translation, spin, and for liquids, shape may be adjusted. An open coil structure provides access for optical and diagnostic probes. Results of experiments with a prototype device are discussed. Levitating and heating materials on earth were demonstrated at frequencies up to 13 MHz.

  18. Thermal Decomposition and Stabilisation of Poly(vinyl Chloride)

    NASA Astrophysics Data System (ADS)

    Troitskii, B. B.; Troitskaya, L. S.

    1985-08-01

    The kinetics and mechanism of the thermal dehydrochlorination of poly(vinyl chloride) and low-molecular-weight chlorohydrocarbons which model various fragments of the polymer molecule, are discussed. Studies designed to determine the qualitative and quantitative compositions of the unstable fragments in poly(vinyl chloride) macromolecules by 13C NMR are examined. Attention is concentrated on the consideration of the mechanism of the action of the most effective thermostabilisers for the polymer - organotin compounds. The principal features of synergism in the stabilisation of poly(vinyl chloride) and the mechanism of the action of synergistic mixtures are analysed. The bibliography includes 107 references.

  19. Convection and downbursts

    Treesearch

    Joseph J. Charney; Brian E. Potter

    2017-01-01

    Convection and downbursts are connected meteorological phenomena with the potential to affect fire behavior and thereby alter the evolution of a wildland fire. Meteorological phenomena related to convection and downbursts are often discussed in the context of fire behavior and smoke. The physical mechanisms that contribute to these phenomena are interrelated, but the...

  20. Stochastic Convection Parameterizations

    NASA Technical Reports Server (NTRS)

    Teixeira, Joao; Reynolds, Carolyn; Suselj, Kay; Matheou, Georgios

    2012-01-01

    computational fluid dynamics, radiation, clouds, turbulence, convection, gravity waves, surface interaction, radiation interaction, cloud and aerosol microphysics, complexity (vegetation, biogeochemistry, radiation versus turbulence/convection stochastic approach, non-linearities, Monte Carlo, high resolutions, large-Eddy Simulations, cloud structure, plumes, saturation in tropics, forecasting, parameterizations, stochastic, radiation-clod interaction, hurricane forecasts

  1. Convection in Condensible-rich Atmospheres

    NASA Astrophysics Data System (ADS)

    Ding, F.; Pierrehumbert, R. T.

    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 CO2 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.

  2. On the reliable decentralised stabilisation of n MIMO systems

    NASA Astrophysics Data System (ADS)

    Befekadu, Getachew K.; Gupta, Vijay; Antsaklis, Panos J.

    2014-08-01

    In this paper, we consider the problem of reliable decentralised stabilisation for n multi-input multi-output (MIMO) systems when some of the shared controllers among these systems are faulty, in the sense that they fail to operate properly due to subsystem (module) failures that may occur in actuators, sensors or controllers. Specifically, we present a design framework using a dilated linear matrix inequalities (LMIs) technique for deriving reliable stabilising state-feedback gains for all n MIMO systems; while a set of decentralised unknown disturbance observers (UDOs) that are shared by all n MIMO systems is used for extending the result to the output-feedback case. Moreover, a sufficient condition for the solvability of the set of decentralised UDOs is given in terms of a minimum-phase condition of each subsystem and a lower-bounding condition on the number of outputs of each channel. We also present a numerical example that illustrates the applicability of the proposed technique.

  3. Stabilising emulsion-based colloidal structures with mixed food ingredients.

    PubMed

    Dickinson, Eric

    2013-03-15

    The physical scientist views food as a complex form of soft matter. The complexity has its origin in the numerous ingredients that are typically mixed together and the subtle variations in microstructure and texture induced by thermal and mechanical processing. The colloid science approach to food product formulation is based on the assumption that the major product attributes such as appearance, rheology and physical stability are determined by the spatial distribution and interactions of a small number of generic structural entities (biopolymers, particles, droplets, bubbles, crystals) organised in various kinds of structural arrangements (layers, complexes, aggregates, networks). This review describes some recent advances in this field with reference to three discrete classes of dispersed systems: particle-stabilised emulsions, emulsion gels and aerated emulsions. Particular attention is directed towards explaining the crucial role of the macromolecular ingredients (proteins and polysaccharides) in controlling the formation and stabilisation of the colloidal structures. The ultimate objective of this research is to provide the basic physicochemical insight required for the reliable manufacture of novel structured foods with an appealing taste and texture, whilst incorporating a more healthy set of ingredients than those found in many existing traditional products.

  4. Compact atomic clocks and stabilised laser for space applications

    NASA Astrophysics Data System (ADS)

    Mileti, Gaetano; Affolderbach, Christoph; Matthey-de-l'Endroit, Renaud

    2016-07-01

    We present our developments towards next generation compact vapour-cell based atomic frequency standards using a tunable laser diode instead of a traditional discharge lamp. The realisation of two types of Rubidium clocks addressing specific applications is in progress: high performance frequency standards for demanding applications such as satellite navigation, and chip-scale atomic clocks, allowing further miniaturisation of the system. The stabilised laser source constitutes the main technological novelty of these new standards, allowing a more efficient preparation and interrogation of the atoms and hence an improvement of the clock performances. However, before this key component may be employed in a commercial and ultimately in a space-qualified instrument, further studies are necessary to demonstrate their suitability, in particular concerning their reliability and long-term operation. The talk will present our preliminary investigations on this subject. The stabilised laser diode technology developed for our atomic clocks has several other applications on ground and in space. We will conclude our talk by illustrating this for the example of a recently completed ESA project on a 1.6 microns wavelength reference for a future space-borne Lidar. This source is based on a Rubidium vapour cell providing the necessary stability and accuracy, while a second harmonic generator and a compact optical comb generated from an electro-optic modulator allow to transfer these properties from the Rubidium wavelength (780nm) to the desired spectral range.

  5. Characterising the stabilisability for second-order linear switched systems

    NASA Astrophysics Data System (ADS)

    Cong, Shen

    2013-03-01

    The stabilisability of second-order linear switched systems is the topic focused on in a number of papers, however, some of its fundamental characteristics are still unrevealed. In this article, regarding a pair of subsystems, we are interested in characterising this problem from both the state-triggering and time-domain viewpoints and in revealing the inherent connection between them. To this end, we first use polar coordinates to represent the geometric property of switching and the dynamical behaviours caused by it, and then put the geometrised switching control into correspondence with the implicit stabilisation mechanism behind it. Doing this in a strong way relies on classifying switching control into two types intuitively, namely, chattering switching and spinning switching, and then clarifying their distinction and properties rigorously. Furthermore, the uniform convergence of the forced trajectory is shown by presenting estimation on its decay rate; and the limit cycles and sliding motions generated by switching are also accounted for. The results are illustrated by elaborate examples.

  6. Magneto-convection.

    PubMed

    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.

  7. Observing Convective Aggregation

    NASA Astrophysics Data System (ADS)

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

    2017-06-01

    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.

  8. Stabilisation of liquid-air surfaces by particles of low surface energy.

    PubMed

    Binks, Bernard P; Rocher, Anaïs

    2010-08-28

    We describe the stabilisation of liquid-air surfaces by microparticles of a low surface energy solid. By varying the surface tension of the liquid, various particle-stabilised materials from oil dispersions to air-in-oil foams to dry water can be prepared.

  9. Determination of Stabiliser Contents in Advanced Gun Propellants by Reverse Phase High Performance Liquid Chromatography

    DTIC Science & Technology

    1994-03-01

    HIGH PERFORMANCE LIQUID CHROMATOGRAPHY N"m A.R. TURNER AND A. WHITE...TO biEPROOU.; AND SELL THIS REPORT Determination of Stabiliser Contents in Advanced Gun Propellants by Reverse Phase High Performance Liquid Chromatography A.R...8217/......... .. Availability Cooes Dist Avaiardlo A-i Determination of Stabiliser Contents in Advanced Gun Propellants by Reverse Phase High Performance Liquid Chromatography

  10. Quantifying lingual coarticulation using ultrasound imaging data collected with and without head stabilisation.

    PubMed

    Zharkova, Natalia; Gibbon, Fiona E; Hardcastle, William J

    2015-04-01

    Previous studies reporting the use of ultrasound tongue imaging with clinical populations have generally provided qualitative information on tongue movement. Meaningful quantitative measures for use in the clinic typically require the speaker's head to be stabilised in relation to a transducer, which may be uncomfortable, and unsuitable for young children. The objective of this study was to explore the applicability of quantitative measurements of stabilisation-free tongue movement data, by comparing ultrasound data collected from 10 adolescents, with and without head stabilisation. Several measures of tongue shape were used to quantify coarticulatory influence from two contrasting vowels on four different consonants. Only one of the measures was completely unaffected by the stabilisation condition for all the consonants. The study also reported cross-consonant differences in vowel-related coarticulatory effects. The implications of the findings for the theory of coarticulation and for potential applications of stabilisation-free tongue curve measurements in clinical studies are discussed.

  11. Pcr by Thermal Convection

    NASA Astrophysics Data System (ADS)

    Braun, Dieter

    The Polymerase Chain Reaction (PCR) allows for highly sensitive and specific amplification of DNA. It is the backbone of many genetic experiments and tests. Recently, three labs independently uncovered a novel and simple way to perform a PCR reaction. Instead of repetitive heating and cooling, a temperature gradient across the reaction vessel drives thermal convection. By convection, the reaction liquid circulates between hot and cold regions of the chamber. The convection triggers DNA amplification as the DNA melts into two single strands in the hot region and replicates into twice the amount in the cold region. The amplification progresses exponentially as the convection moves on. We review the characteristics of the different approaches and show the benefits and prospects of the method.

  12. Complex spatiotemporal convection patterns

    NASA Astrophysics Data System (ADS)

    Pesch, W.

    1996-09-01

    This paper reviews recent efforts to describe complex patterns in isotropic fluids (Rayleigh-Bénard convection) as well as in anisotropic liquid crystals (electro-hydrodynamic convection) when driven away from equilibrium. A numerical scheme for solving the full hydrodynamic equations is presented that allows surprisingly well for a detailed comparison with experiments. The approach can also be useful for a systematic construction of models (order parameter equations).

  13. Mesoscale/convective interaction

    NASA Technical Reports Server (NTRS)

    Haines, P. A.; Sun, W. Y.

    1988-01-01

    A novel cumulus parameterization scheme (CPS) has been developed in order to account for mesoscale/convective-scale interaction which considers both the mesoscale and convective scale mass and moisture budgets, under the assumption that the heating rate is a maximum for given environmental conditions. The basis of the CPS is a detailed, quasi-one-dimensional cloud model that calculates mass and moisture fluxes similar to those calculated by the Schlesinger (1978) three-dimensional model.

  14. Characterizing convective cold pools

    NASA Astrophysics Data System (ADS)

    Drager, Aryeh J.; van den Heever, Susan C.

    2017-06-01

    Cold pools produced by convective storms play an important role in Earth's climate system. However, a common framework does not exist for objectively identifying convective cold pools in observations and models. The present study investigates convective cold pools within a simulation of tropical continental convection that uses a cloud-resolving model with a coupled land-surface model. Multiple variables are assessed for their potential in identifying convective cold pool boundaries, and a novel technique is developed and tested for identifying and tracking cold pools in numerical model simulations. This algorithm is based on surface rainfall rates and radial gradients in the density potential temperature field. The algorithm successfully identifies near-surface cold pool boundaries and is able to distinguish between connected cold pools. Once cold pools have been identified and tracked, composites of cold pool evolution are then constructed, and average cold pool properties are investigated. Wet patches are found to develop within the centers of cold pools where the ground has been soaked with rainwater. These wet patches help to maintain cool surface temperatures and reduce cold pool dissipation, which has implications for the development of subsequent convection.

  15. Production and validation of model iron-tannate dyed textiles for use as historic textile substitutes in stabilisation treatment studies

    PubMed Central

    2012-01-01

    Background For millennia, iron-tannate dyes have been used to colour ceremonial and domestic objects shades of black, grey, or brown. Surviving iron-tannate dyed objects are part of our cultural heritage but their existence is threatened by the dye itself which can accelerate oxidation and acid hydrolysis of the substrate. This causes many iron-tannate dyed textiles to discolour and decrease in tensile strength and flexibility at a faster rate than equivalent undyed textiles. The current lack of suitable stabilisation treatments means that many historic iron-tannate dyed objects are rapidly crumbling to dust with the knowledge and value they hold being lost forever. This paper describes the production, characterisation, and validation of model iron-tannate dyed textiles as substitutes for historic iron-tannate dyed textiles in the development of stabilisation treatments. Spectrophotometry, surface pH, tensile testing, SEM-EDX, and XRF have been used to characterise the model textiles. Results On application to textiles, the model dyes imparted mid to dark blue-grey colouration, an immediate tensile strength loss of the textiles and an increase in surface acidity. The dyes introduced significant quantities of iron into the textiles which was distributed in the exterior and interior of the cotton, abaca, and silk fibres but only in the exterior of the wool fibres. As seen with historic iron-tannate dyed objects, the dyed cotton, abaca, and silk textiles lost tensile strength faster and more significantly than undyed equivalents during accelerated thermal ageing and all of the dyed model textiles, most notably the cotton, discoloured more than the undyed equivalents on ageing. Conclusions The abaca, cotton, and silk model textiles are judged to be suitable for use as substitutes for cultural heritage materials in the testing of stabilisation treatments. PMID:22616934

  16. Finite settling time stabilisation: the robust SISO case

    NASA Astrophysics Data System (ADS)

    Milonidis, E.; Kostarigka, A.; Karcanias, N.

    2011-09-01

    This article deals with the problem of robustness to multiplicative plant perturbations for the case of finite settling time stabilisation (FSTS) of single input single output (SISO), linear, discrete-time systems. FSTS is a generalisation of the deadbeat control and as in the case of deadbeat control the main feature of FSTS is the placement of all closed-loop poles at the origin of the z-plane. This makes FSTS sensitive to plant perturbations hence, the need of robust design. An efficient robustness index is introduced and the problem is reduced to a finite linear programme where all the benefits of the simplex method, such as effectiveness, efficiency and ability to provide complete solution to the optimisation problem, can be exploited.

  17. Helium damage and helium effusion in fully stabilised zirconia

    NASA Astrophysics Data System (ADS)

    Damen, P. M. G.; Matzke, Hj.; Ronchi, C.; Hiernaut, J.-P.; Wiss, T.; Fromknecht, R.; van Veen, A.; Labohm, F.

    2002-05-01

    Fully stabilised zirconia (FSZ) samples have been implanted with helium-ions of different energies (200 keV and 1 MeV) and with different fluences (1.4×10 13-1.4×10 16 He +/cm 2). Neutron depth profiling (NDP) for different annealing temperatures and effusion experiments in two different experimental systems with different thermal annealings have been performed on these samples. The samples were analysed by electron microscopy during the various annealing stages. For the low-fluence samples, the diffusion of helium is probably caused by vacancy assisted interstitial diffusion with an activation energy of 1.6 eV. In the highest fluence samples probably high pressure bubbles are formed during thermal annealing.

  18. Stabilising compensators for linear time-varying differential systems

    NASA Astrophysics Data System (ADS)

    Oberst, Ulrich

    2016-04-01

    In this paper, we describe a constructive test to decide whether a given linear time-varying (LTV) differential system admits a stabilising compensator for the control tasks of tracking, disturbance rejection or model matching and construct and parametrise all of them if at least one exists. In analogy to the linear time-invariant (LTI) case, the ring of stable rational functions, noncommutative in the LTV situation, and the Kučera-Youla parametrisation play prominent parts in the theory. We transfer Blumthaler's thesis from the LTI to the LTV case and sharpen, complete and simplify the corresponding results in the book 'Linear Time-Varying Systems' by Bourlès and Marinescu.

  19. Formation and stabilisation of triclosan colloidal suspensions using supersaturated systems.

    PubMed

    Raghavan, S L; Schuessel, K; Davis, A; Hadgraft, J

    2003-08-11

    The aim of this paper is to prepare and stabilise, in situ, colloidal microsuspensions of triclosan using the polymer, hydroxypropyl methylcellulose (HPMC). The suspensions were prepared from supersaturated solutions of triclosan. The cosolvent technique was used to create supersaturation. Propylene glycol and water were used as the cosolvents. The triclosan particles had a large needle-shaped morphology, when grown in the absence of the polymer. Moreover, the particles grew rapidly to sizes greater than 5 micrometer over a period of 7h. When HPMC was added, the particle sizes were in the range 90-250 nm depending on the amount of polymer present in the solutions. The stability of the solutions was evaluated over a period of 40 days during which the particle sizes did not vary. The results were consistent with the mechanism proposed by Raghavan et al. [Int. J. Pharm. 212 (2001b) 213].

  20. Ammonia volatilisation in waste stabilisation ponds: a cascade of misinterpretations?

    PubMed

    Camargo Valero, M A; Mara, D D

    2010-01-01

    Ammonia volatilisation has generally been reported as, or assumed to be, the main nitrogen removal mechanism in waste stabilisation ponds (WSP). Nitrogen removal via ammonia volatilisation is based on two observations: (a) in-pond pH values can reach high values (>9, even >10), so increasing the proportion of the total ammonia present as the un-ionized form or free ammonia (NH(3)); and (b) in-pond temperatures can also be high, so improving the mass transfer rate of free ammonia to the atmosphere. Consequently, one of the most widely accepted models for ammonia removal in WSP is that reported by Pano & Middlebrooks in 1982, which was developed to reflect the occurrence of these two observations. This work reports how simple mathematical models for ammonia volatilisation in WSP, in spite of the possibility of their giving good predictions, may not accurately describe the main pathways and mechanisms involved in ammonia removal in WSP.

  1. An Investigation into the Effect of Stabiliser Content on the Minimum Characteristic Chamber Length for Homogeneously-Catalysed Hydrogen Peroxide

    DTIC Science & Technology

    2007-11-02

    packs to achieve a heterogeneous catalytic reaction to decompose the propellant into steam and oxygen. The decomposition of highly stabilised ...England, Private Communication. May 2004. [3] Musker, A. J. "Highly Stabilised Hydrogen Peroxide as a Rocket Propellant ", Proceedings of the...Investigation into the Effect of Stabiliser Content on the Minimum Characteristic Chamber Length for Homogeneously-Catalysed Hydrogen Peroxide 5c

  2. Comparison of simulated and observed convective gravity waves

    NASA Astrophysics Data System (ADS)

    Kalisch, S.; Chun, H.-Y.; Ern, M.; Preusse, P.; Trinh, Q. T.; Eckermann, S. D.; Riese, M.

    2016-11-01

    Gravity waves (GWs) from convection have horizontal wavelengths typically shorter than 100 km. Resolving these waves in state-of-the-art atmospheric models still remains challenging. Also, their time-dependent excitation process cannot be represented by a common GW drag parametrization with static launch distribution. Thus, the aim of this paper is to investigate the excitation and three-dimensional propagation of GWs forced by deep convection in the troposphere and estimate their influence on the middle atmosphere. For that purpose, the GW ray tracer Gravity-wave Regional Or Global Ray Tracer (GROGRAT) has been coupled to the Yonsei convective GW source model. The remaining free model parameters have been constrained by measurements. This work led to a coupled convective GW model representing convective GWs forced from small cells of deep convection up to large-scale convective clusters. In order to compare our simulation results with observed global distributions of momentum flux, limitations of satellite instruments were taken into account: The observational filter of a limb-viewing satellite instrument restricts measurements of GWs to waves with horizontal wavelengths longer than 100 km. Convective GWs, however, often have shorter wavelengths. This effect is taken into account when comparing simulated and observable GW spectra. We find good overall agreement between simulated and observed GW global distributions, if superimposed with a nonorographic background spectrum for higher-latitude coverage. Our findings indicate that parts of the convective GW spectrum can indeed be observed by limb-sounding satellites.

  3. Supergranulation, a convective phenomenon

    NASA Astrophysics Data System (ADS)

    Udayashankar, Paniveni

    2015-08-01

    Observation of the Solar photosphere through high resolution instruments have long indicated that the surface of the Sun is not a tranquil, featureless surface but is beset with a granular appearance. These cellular velocity patterns are a visible manifestation of sub- photospheric convection currents which contribute substantially to the outward transport of energy from the deeper layers, thus maintaining the energy balance of the Sun as a whole.Convection is the chief mode of transport in the outer layers of all cool stars such as the Sun (Noyes,1982). Convection zone of thickness 30% of the Solar radius lies in the sub-photospheric layers of the Sun. Convection is revealed on four scales. On the scale of 1000 km, it is granulation and on the scale of 8-10 arcsec, it is Mesogranulation. The next hierarchial scale of convection ,Supergranules are in the range of 30-40 arcsec. The largest reported manifestation of convection in the Sun are ‘Giant Cells’or ‘Giant Granules’, on a typical length scale of about 108 m.'Supergranules' is caused by the turbulence that extends deep into the convection zone. They have a typical lifetime of about 20hr with spicules marking their boundaries. Gas rises in the centre of the supergranules and then spreads out towards the boundary and descends.Broadly speaking supergranules are characterized by the three parameters namely the length L, the lifetime T and the horizontal flow velocity vh . The interrelationships amongst these parameters can shed light on the underlying convective processes and are in agreement with the Kolmogorov theory of turbulence as applied to large scale solar convection (Krishan et al .2002 ; Paniveni et. al. 2004, 2005, 2010).References:1) Noyes, R.W., The Sun, Our Star (Harvard University Press, 1982)2) Krishan, V., Paniveni U., Singh , J., Srikanth R., 2002, MNRAS, 334/1,2303) Paniveni , U., Krishan, V., Singh, J., Srikanth, R., 2004, MNRAS, 347, 1279-12814) Paniveni , U., Krishan, V., Singh, J

  4. Anomalously weak solar convection.

    PubMed

    Hanasoge, Shravan M; Duvall, Thomas L; Sreenivasan, Katepalli R

    2012-07-24

    Convection in the solar interior is thought to comprise structures on a spectrum of scales. This conclusion emerges from phenomenological studies and numerical simulations, though neither covers the proper range of dynamical parameters of solar convection. Here, we analyze observations of the wavefield in the solar photosphere using techniques of time-distance helioseismology to image flows in the solar interior. We downsample and synthesize 900 billion wavefield observations to produce 3 billion cross-correlations, which we average and fit, measuring 5 million wave travel times. Using these travel times, we deduce the underlying flow systems and study their statistics to bound convective velocity magnitudes in the solar interior, as a function of depth and spherical-harmonic degree ℓ. Within the wavenumber band ℓ < 60, convective velocities are 20-100 times weaker than current theoretical estimates. This constraint suggests the prevalence of a different paradigm of turbulence from that predicted by existing models, prompting the question: what mechanism transports the heat flux of a solar luminosity outwards? Advection is dominated by Coriolis forces for wavenumbers ℓ < 60, with Rossby numbers smaller than approximately 10(-2) at r/R([symbol: see text]) = 0.96, suggesting that the Sun may be a much faster rotator than previously thought, and that large-scale convection may be quasi-geostrophic. The fact that isorotation contours in the Sun are not coaligned with the axis of rotation suggests the presence of a latitudinal entropy gradient.

  5. Anomalously Weak Solar Convection

    NASA Technical Reports Server (NTRS)

    Hanasoge, Shravan M.; Duvall, Thomas L.; Sreenivasan, Katepalli R.

    2012-01-01

    Convection in the solar interior is thought to comprise structures on a spectrum of scales. This conclusion emerges from phenomenological studies and numerical simulations, though neither covers the proper range of dynamical parameters of solar convection. Here, we analyze observations of the wavefield in the solar photosphere using techniques of time-distance helioseismology to image flows in the solar interior. We downsample and synthesize 900 billion wavefield observations to produce 3 billion cross-correlations, which we average and fit, measuring 5 million wave travel times. Using these travel times, we deduce the underlying flow systems and study their statistics to bound convective velocity magnitudes in the solar interior, as a function of depth and spherical- harmonic degree l..Within the wavenumber band l < 60, convective velocities are 20-100 times weaker than current theoretical estimates. This constraint suggests the prevalence of a different paradigm of turbulence from that predicted by existing models, prompting the question: what mechanism transports the heat flux of a solar luminosity outwards? Advection is dominated by Coriolis forces for wavenumbers l < 60, with Rossby numbers smaller than approximately 10(exp -2) at r/R-solar = 0.96, suggesting that the Sun may be a much faster rotator than previously thought, and that large-scale convection may be quasi-geostrophic. The fact that isorotation contours in the Sun are not coaligned with the axis of rotation suggests the presence of a latitudinal entropy gradient.

  6. Phenomenology of turbulent convection

    NASA Astrophysics Data System (ADS)

    Verma, Mahendra; Chatterjee, Anando; Kumar, Abhishek; Samtaney, Ravi

    2016-11-01

    We simulate Rayleigh-Bénard convection (RBC) in which a fluid is confined between two thermally conducting plates. We report results from direct numerical simulation (DNS) of RBC turbulence on 40963 grid, the highest resolution hitherto reported, on 65536 cores of Cray XC40, Shaheen II, at KAUST. The non-dimensional parameters of our simulation are: the Rayleigh number Ra = 1 . 1 ×1011 (the highest ever for a pseudo-spectral simulation) and Prandtl number of unity. We present energy flux diagnostics of shell-to-shell (in wave number space) transfer. Furthermore, noting that convective flows are anisotropic due to buoyancy, we quantify anisotropy by subdividing each wavenumber shell into rings and quantify ring energy spectrum. An outstanding question in convective turbulence is the wavenumber scaling of the energy spectrum. Our pseudo-spectral simulations of turbulent thermal convection coupled with novel energy transfer diagnostics have provided a definitive answer to this question. We conclude that convective turbulence exhibits behavior similar to fluid turbulence, that is, Kolmogorov's k - 5 / 3 spectrum with forward and local energy transfers, along with a nearly isotropic energy distribution. The supercomputer Shaheen at KAUST was utilized for the simulations.

  7. Convective quasi-equilibrium

    NASA Astrophysics Data System (ADS)

    Yano, J.-I.; Plant, R. S.

    2012-12-01

    The concept of convective quasi-equilibrium (CQE) is a key ingredient in order to understand the role of deep moist convection in the atmosphere. It has been used as a guiding principle to develop almost all convective parameterizations and provides a basic theoretical framework for large-scale tropical dynamics. The CQE concept as originally proposed by Arakawa and Schubert (1974) is systematically reviewed from wider perspectives. Various interpretations and extensions of Arakawa and Schubert's CQE are considered both in terms of a thermodynamic analogy and as a dynamical balance. The thermodynamic interpretations can be more emphatically embraced as a homeostasis. The dynamic balance interpretations can be best understood by analogy with the slow manifold. Various criticisms of CQE can be avoided by taking the dynamic balance interpretation. Possible limits of CQE are also discussed, including the importance of triggering in many convective situations, as well as the possible self-organized criticality of tropical convection. However, the most intriguing aspect of the CQE concept is that in spite of many observational tests supporting and interpreting it in many different senses, it has never been established in a robust manner based on a systematic analysis of the cloud work function budget by observations as was originally defined.

  8. Observing convective aggregation

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    Convective self-aggregation 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 a 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.

  9. Convection in White Dwarfs

    NASA Astrophysics Data System (ADS)

    Provencal, Judith L.; Shipman, H.; Dalessio, J.; M, M.

    2012-01-01

    Convection is one of the largest sources of theoretical uncertainty in our understanding of stellar physics. Current studies of convective energy transport are based on the mixing length theory. Originally intended to depict turbulent flows in engineering situations, MLT enjoys moderate success in describing stellar convection. However, problems arising from MLT's incompleteness are apparent in studies ranging from determinations of the ages of massive stars, to understanding the structure F and early A stars, to predicting the pulsation periods of solar stars, to understanding the atmosphere of Titan. As an example for white dwarfs, Bergeron et al. (1995) show that model parameters such as flux, line profiles, energy distribution, color indices, and equivalent widths are extremely sensitive to the assumed MLT parameterization. The authors find systematic uncertainties ranging from 25% for effective temperatures to 11% for mass and radius. The WET is engaged in a long term project to empirically determine the physical properties of convection in the atmospheres of pulsating white dwarfs. The technique, outlined by Montgomery et al. (2010), uses information from nonlinear (non-sinusoidal) pulse shapes of the target star to empirically probe the physical properties of its convection zone. Approximately two thirds of all white dwarfs show nonlinear characteristics in their light curves. We present current results from WET targets in 2008-2011.

  10. Convection in containerless processing.

    PubMed

    Hyers, Robert W; Matson, Douglas M; Kelton, Kenneth F; Rogers, Jan R

    2004-11-01

    Different containerless processing techniques have different strengths and weaknesses. Applying more than one technique allows various parts of a problem to be solved separately. For two research projects, one on phase selection in steels and the other on nucleation and growth of quasicrystals, a combination of experiments using electrostatic levitation (ESL) and electromagnetic levitation (EML) is appropriate. In both experiments, convection is an important variable. The convective conditions achievable with each method are compared for two very different materials: a low-viscosity, high-temperature stainless steel, and a high-viscosity, low-temperature quasicrystal-forming alloy. It is clear that the techniques are complementary when convection is a parameter to be explored in the experiments. For a number of reasons, including the sample size, temperature, and reactivity, direct measurement of the convective velocity is not feasible. Therefore, we must rely on computation techniques to estimate convection in these experiments. These models are an essential part of almost any microgravity investigation. The methods employed and results obtained for the projects levitation observation of dendrite evolution in steel ternary alloy rapid solidification (LODESTARS) and quasicrystalline undercooled alloys for space investigation (QUASI) are explained.

  11. A full spectral cumulus cloud parameterisation including aerosol effects: The Convective Cloud Field Model (CCFM)

    NASA Astrophysics Data System (ADS)

    Wagner, T. M.; Graf, H. F.; Yano, J. I.

    2009-04-01

    The convective cloud field model is a convection parameterisation based on the representation of a full cumulus cloud spectrum using a dynamical quasi-equilibrium closure. It employs a one dimensional entraining parcel model whose properties are simulated on a refined vertical resolution (~100 m) in order to capture the complex cloud microphysical processes in convective clouds. We introduced an enhanced microphysics compared to those currently used in convection parameterisations, containing warm and mixed phase cloud microphysics processes and incorporates aerosol effects by linking the cloud droplet number concentration to the aerosol amount. Similar to the Arakawa and Schubert (1974) quasi-equilibrium closure we allow for the mutual influence of clouds via the environment. Instead of assuming instantaneous stabilisation of the environment though, the clouds are dynamically interacting for the length of the large scale model time step without necessarily adopting an equilibrium situation. The model is evaluated in single column mode (SCM) for continental and tropical convection using the ARM SGP and TWP-ICE cases. Moreover it is evaluated in global mode using the global atmospheric circulation model ECHAM5. For the SCM cases the precipitation, heating and moistening rates for the simulated period is better represented than with the Tiedtke massflux scheme which is the usual convection parameterisation within ECHAM5. Moreover, we find a clear response to an enhanced aerosol loading which generally leads to a reduction of convective precipitation. Globally, the CCFM produces slightly higher convective precipitation rates and especially responds better to convective instability over lower latitudes and the storm track regions.

  12. Strong stabilisation of a wind turbine tower model in the plane of the turbine blades

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaowei; Weiss, George

    2014-10-01

    We investigate the strong stabilisation of a wind turbine tower model in the plane of the turbine blades, which comprises a nonuniform NASA Spacecraft Control Laboratory Experiment (SCOLE) system and a two-mass drive-train model (with gearbox). The control input is the torque created by the electrical generator. Using a strong stabilisation theorem for a class of impedance passive linear systems with bounded control and observation operators, we show that the wind turbine tower model can be strongly stabilised. The control is by static output feedback from the angular velocities of the nacelle and the generator rotor.

  13. Numerical Simulations of Turbulent Convection with Background Rotation and Stratification

    NASA Astrophysics Data System (ADS)

    Chan, Daniel

    1997-11-01

    Direct numerical simulation using a Fourier-Legendre spectral element method and about six million points have been performed. Bouyancy flux, with a flux Rayleigh number of about 10^9, is introduced at a localized region along the top boundary of a three-dimensional computational box. The ambient fluid is in a solid body rotation with linear stable stratification. Vortices have been observed in the horizontal plane. The possible mechanism for the formation of these vortices is by either barotropic or baroclinic stability. Using numerical data and experimental correlation, we identify the latter being the more likely scenario.

  14. Natural convection: Fundamentals and applications

    NASA Astrophysics Data System (ADS)

    Kakac, S.; Aung, W.; Viskanta, R.

    Among the topics discussed are: stability solutions for laminar external boundary region flows; natural convection in plane layers and cavities with volumetric energy sources; and turbulence modelling equations. Consideration is also given to: natural convection in enclosures containing tube bundles; natural limiting behaviors in porous media cavity flows; numerical solutions in laminar and turbulent natural convection; and heat transfer in the critical region of binary mixtures. Additional topics discussed include: natural convective cooling of electronic equipment; natural convection suppression in solar collectors; and laser induced buoyancy and forced convection in vertical tubes.

  15. Groundwater convection model for Rio Grande rift geothermal resources

    SciTech Connect

    Morgan, P.; Harder, V.; Swanberg, C.A.; Daggett, P.H.; Ruscetta, C.A.; Foley, D.

    1981-05-01

    It has been proposed that forced convection, driven by normal groundwater flow through the interconnected basins of the Rio Grande rift is the primary source mechanism for the numerous geothermal anomalies along the rift. A test of this concept using an analytical model indicates that significant forced convection must occur in the basins even if permeabilities are as low as 50-200 millidarcies at a depth of 2 km. Where groundwater flow is constricted at the discharge areas of the basins forced convection can locally increase the gradient to a level where free convection also occurs, generating surface heat flow anomalies 5-15 times background. A compilation of groundwater data for the rift basins shows a strong correlation between constrictions in groundwater flow and hot springs and geothermal anomalies, giving strong circumstantial support to the convection model.

  16. A groundwater convection model for Rio Grande rift geothermal resources

    NASA Technical Reports Server (NTRS)

    Morgan, P.; Harder, V.; Daggett, P. H.; Swanberg, C. A.

    1981-01-01

    It has been proposed that forced convection, driven by normal groundwater flow through the interconnected basins of the Rio Grande rift is the primary source mechanism for the numerous geothermal anomalies along the rift. A test of this concept using an analytical model indicates that significant forced convection must occur in the basins even if permeabilities are as low as 50-200 millidarcies at a depth of 2 km. Where groundwater flow is constricted at the discharge areas of the basins forced convection can locally increase the gradient to a level where free convection also occurs, generating surface heat flow anomalies 5-15 times background. A compilation of groundwater data for the rift basins shows a strong correlation between constrictions in groundwater flow and hot springs and geothermal anomalies, giving strong circumstantial support to the convection model.

  17. A groundwater convection model for Rio Grande rift geothermal resources

    NASA Technical Reports Server (NTRS)

    Morgan, P.; Harder, V.; Daggett, P. H.; Swanberg, C. A.

    1981-01-01

    It has been proposed that forced convection, driven by normal groundwater flow through the interconnected basins of the Rio Grande rift is the primary source mechanism for the numerous geothermal anomalies along the rift. A test of this concept using an analytical model indicates that significant forced convection must occur in the basins even if permeabilities are as low as 50-200 millidarcies at a depth of 2 km. Where groundwater flow is constricted at the discharge areas of the basins forced convection can locally increase the gradient to a level where free convection also occurs, generating surface heat flow anomalies 5-15 times background. A compilation of groundwater data for the rift basins shows a strong correlation between constrictions in groundwater flow and hot springs and geothermal anomalies, giving strong circumstantial support to the convection model.

  18. Gravity wave initiated convection

    NASA Technical Reports Server (NTRS)

    Hung, R. J.

    1990-01-01

    The vertical velocity of convection initiated by gravity waves was investigated. In one particular case, the convective motion-initiated and supported by the gravity wave-induced activity (excluding contributions made by other mechanisms) reached its maximum value about one hour before the production of the funnel clouds. In another case, both rawinsonde and geosynchronous satellite imagery were used to study the life cycles of severe convective storms. Cloud modelling with input sounding data and rapid-scan imagery from GOES were used to investigate storm cloud formation, development and dissipation in terms of growth and collapse of cloud tops, as well as, the life cycles of the penetration of overshooting turrets above the tropopause. The results based on these two approaches are presented and discussed.

  19. Active control of convection

    SciTech Connect

    Bau, H.H.

    1995-12-31

    Using stability theory, numerical simulations, and in some instances experiments, it is demonstrated that the critical Rayleigh number for the bifurcation (1) from the no-motion (conduction) state to the motion state and (2) from time-independent convection to time-dependent, oscillatory convection in the thermal convection loop and Rayleigh-Benard problems can be significantly increased or decreased. This is accomplished through the use of a feedback controller effectuating small perturbations in the boundary data. The controller consists of sensors which detect deviations in the fluid`s temperature from the motionless, conductive values and then direct actuators to respond to these deviations in such a way as to suppress the naturally occurring flow instabilities. Actuators which modify the boundary`s temperature/heat flux are considered. The feedback controller can also be used to control flow patterns and generate complex dynamic behavior at relatively low Rayleigh numbers.

  20. Magnetospheric convection at Uranus

    NASA Technical Reports Server (NTRS)

    Selesnick, R. S.

    1987-01-01

    The unusual configuration of the Uranian magnetosphere leads to differences in the relative effects of solar wind induced magnetospheric convection and plasma corotation from those at the other planets. At the present epoch the orientation of the rotation axis of Uranus with respect to the solar wind flow direction leads to a decoupling of the convective and corotational flows, allowing plasma from the tail to move unimpeded through the inner magnetosphere. As Uranus progresses in its orbit around the sun, corotation plays a gradually more important role and the plasma residence times within the magnetosphere increase. When the rotation axis finally becomes perpendicular to the solar wind flow, corotation is dominant.

  1. In situ clinical evaluation of a stabilised, stannous fluoride dentifrice.

    PubMed

    Bellamy, Philip G; Harris, Robin; Date, Robert F; Mussett, Andrew J S; Manley, Andrew; Manly, Andrew; Barker, Matthew L; Hellin, Nicola; West, Nicola X

    2014-03-01

    To compare the erosion protection efficacy of a stabilised, stannous fluoride (SnF2 ) dentifrice versus a sodium fluoride (NaF) dentifrice using a modified in situ clinical model. This study, a randomised parallel group in situ design with in vivo product use and ex vivo acid challenge, compared: A, a dentifrice containing 1,450 ppm F as NaF; B, a dentifrice containing 1,450 ppm F (1,100 ppm F as SnF2 + 350 ppm F as NaF); and T, tap water. Sample size was n = 4 per group (total of 12 subjects) and within each subject appliances were placed on each side of the mouth (left and right). Enamel specimens were placed in different positions of the mouth (front, mid-front, mid-rear, rear) in each appliance (total = 8 specimens per subject). Product treatment was twice per day (lingual brushing for 30 seconds followed by swishing for 90 seconds with the resultant product/saliva slurry) in vivo for 15 days, and ex vivo acid treatment (0.02 m citric acid 5 minutes four times per day; total exposure time = 300 minutes). Data were analysed using a general linear repeated measures model with treatment, side and position as fixed effects. Within subjects, correlations were modelled assuming a different correlation and variance for treatment B relative to the other groups. Pairwise treatment differences were performed using a 5% two-sided significance level. Enamel loss (in μm) was significantly lower (P < 0.005) for treatment B versus treatments A and T. Treatment B reduced enamel surface loss by 86.9% relative to treatment A. There was no statistical difference in mean enamel loss (P = 0.51) between treatments A and T. Enamel loss was not statistically different for side (left vs. right; P = 0.44) or position (front, mid-front, mid-rear, rear; P = 0.36). This modified in situ erosion model confirmed the enhanced erosion protection benefits of a stabilised SnF2 dentifrice versus a conventional NaF dentifrice, validating the ability of the model to safely and effectively

  2. Event-triggered control for semi-global stabilisation of systems with actuator saturation

    NASA Astrophysics Data System (ADS)

    Zhang, Liangyin; Chen, Michael Z. Q.

    2016-05-01

    This paper investigates the problem of event-triggered control for semi-global stabilisation of null controllable systems subject to actuator saturation. First, for a continuous-time system, novel event-triggered low-gain control algorithms based on Riccati equations are proposed to achieve semi-global stabilisation. The algebraic Riccati equation with a low-gain parameter is utilised to design both the event-triggering condition and the linear controller; a minimum inter-event time based on the Riccati ordinary differential equation is set a priori to exclude the Zeno behaviour. In addition, the high-low gain techniques are utilised to extend the semi-global results to event-based global stabilisation. Furthermore, for a discrete-time system, novel low-gain and high-low-gain control algorithms are proposed to achieve event-triggered stabilisation. Numerical examples are provided to illustrate the theoretical results.

  3. Mean square stabilisation of complex oscillatory regimes in nonlinear stochastic systems

    NASA Astrophysics Data System (ADS)

    Bashkirtseva, Irina; Ryashko, Lev

    2016-04-01

    A problem of stabilisation of the randomly forced periodic and quasiperiodic modes for nonlinear dynamic systems is considered. For this problem solution, we propose a new theoretical approach to consider these modes as invariant manifolds of the stochastic differential equations with control. The aim of the control is to provide the exponential mean square (EMS) stability for these manifolds. A general method of the stabilisation based on the algebraic criterion of the EMS-stability is elaborated. A constructive technique for the design of the feedback regulators stabilising various types of oscillatory regimes is proposed. A detailed parametric analysis of the problem of the stabilisation for stochastically forced periodic and quasiperiodic modes is given. An illustrative example of stochastic Hopf system is included to demonstrate the effectiveness of the proposed technique.

  4. Dynamic quantised feedback stabilisation of discrete-time linear system with white noise input

    NASA Astrophysics Data System (ADS)

    Ji, Mingming; He, Xing; Zhang, Weidong

    2015-09-01

    In this paper, we mainly focus on the problem of quantised feedback stabilisation of a stochastic discrete-time linear system with white noise input. The dynamic quantiser is used here. The stability of the system under state quantisation and input quantisation is analysed in detail, respectively. Both the convergence of the state's mean and the boundedness of the state's covariance matrix norm should be considered when analysing its stability. It is shown that for the two situations of the state quantisation and the input quantisation, if the system without noise input can be stabilised by a linear feedback law, it must be stabilised by the dynamic quantised feedback control policy. The sufficient conditions that the dynamic quantiser should satisfy are given. Using the results obtained in this paper, one can test whether the stochastic system is stabilisable or not. Numerical examples are given to show the effectiveness of the results.

  5. Combined buoyancy-thermocapillary convection

    NASA Technical Reports Server (NTRS)

    Homsy, G. M.

    1990-01-01

    Combined buoyancy-thermocapillary convection was studied in 2D and 3D. Fluid motion caused by thermally induced tension gradients on the free surface of a fluid is termed thermocapillary convection. It is well-known that in containerless processing of materials in space, thermocapillary convection is a dominant mechanism of fluid flow. Welding and crystal growth processes are terrestrial applications where thermocapillary convection has direct relevance.

  6. Moduli stabilisation with nilpotent goldstino: vacuum structure and SUSY breaking

    NASA Astrophysics Data System (ADS)

    Aparicio, Luis; Quevedo, Fernando; Valandro, Roberto

    2016-03-01

    We study the effective field theory of KKLT and LVS moduli stabilisation scenarios coupled to an anti-D3-brane at the tip of a warped throat. We describe the presence of the anti-brane in terms of a nilpotent goldstino superfield in a supersymmetric effective field theory. The introduction of this superfield produces a term that can lead to a de Sitter minimum. We fix the Kähler moduli dependence of the nilpotent field couplings by matching this term with the anti-D3-brane uplifting contribution. The main result of this paper is the computation, within this EFT, of the soft supersymmetry breaking terms in both KKLT and LVS for matter living on D3-brane (leaving the D7-brane analysis to an appendix). A handful of distinct phenomenological scenarios emerge that could have low energy implications, most of them having a split spectrum of soft masses. Some cosmological and phenomenological properties of these models are discussed. We also check that the attraction between the D3-brane and the anti-D3-brane does not affect the leading contribution to the soft masses and does not destabilise the system.

  7. CO2 dissociation in vortex-stabilised microwave plasmas

    NASA Astrophysics Data System (ADS)

    Welzel, S.; Bongers, W. A.; Graswinckel, M. F.; van de Sanden, M. C. M.

    2014-10-01

    Plasma-assisted gas conversion techniques are widely considered as efficient building blocks in a future energy infrastructure which will be based on intermittent, renewable electricity sources. CO2 dissociation in high-frequency plasmas is of particular interest in carbon capture and utilisation process chains for the production of CO2-neutral fuels. In order to achieve efficient plasma processes of high throughput specifically designed gas flow and power injection regimes are required. In this contribution vortex-stabilised microwave plasmas in undiluted CO2 were studied in a pressure range from 170 to 1000 mbar at up to 1 kW (forward) injected power, respectively. The CO2 depletion was measured downstream, e.g. by means of mass spectrometry. Although the system configuration was entirely not optimised, energy efficiencies of nearly 40%, i.e. close to the thermal dissociation limit, and conversion efficiencies of up to 23% were achieved. Additionally, spatially-resolved emission spectroscopy was applied to map the axial and radial distribution of excited atomic (C, O) and molecular (CO, C2) species along with their rotational temperatures. Eindhoven University of Technology, Postbox 513, 5600 MB Eindhoven.

  8. Deformations, moduli stabilisation and gauge couplings at one-loop

    NASA Astrophysics Data System (ADS)

    Honecker, Gabriele; Koltermann, Isabel; Staessens, Wieland

    2017-04-01

    We investigate deformations of Z_2 orbifold singularities on the toroidal orbifold {T}^6/(Z_2× Z_6) with discrete torsion in the framework of Type IIA orientifold model building with intersecting D6-branes wrapping special Lagrangian cycles. To this aim, we employ the hypersurface formalism developed previously for the orbifold {T}^6/(Z_2× Z_6) with discrete torsion and adapt it to the (Z_2× Z_6× Ω R) point group by modding out the remaining Z_3 subsymmetry and the orientifold projection Ω R. We first study the local behaviour of the Z_3× Ω R invariant deformation orbits under non-zero deformation and then develop methods to assess the deformation effects on the fractional three-cycle volumes globally. We confirm that D6-branes supporting USp(2 N) or SO(2 N) gauge groups do not constrain any deformation, while deformation parameters associated to cycles wrapped by D6-branes with U( N) gauge groups are constrained by D-term supersymmetry breaking. These features are exposed in global prototype MSSM, Left-Right symmetric and Pati-Salam models first constructed in [1, 2], for which we here count the number of stabilised moduli and study flat directions changing the values of some gauge couplings.

  9. TDP-43 stabilises the processing intermediates of mitochondrial transcripts.

    PubMed

    Izumikawa, Keiichi; Nobe, Yuko; Yoshikawa, Harunori; Ishikawa, Hideaki; Miura, Yutaka; Nakayama, Hiroshi; Nonaka, Takashi; Hasegawa, Masato; Egawa, Naohiro; Inoue, Haruhisa; Nishikawa, Kouki; Yamano, Koji; Simpson, Richard J; Taoka, Masato; Yamauchi, Yoshio; Isobe, Toshiaki; Takahashi, Nobuhiro

    2017-08-09

    The 43-kDa trans-activating response region DNA-binding protein 43 (TDP-43) is a product of a causative gene for amyotrophic lateral sclerosis (ALS). Despite of accumulating evidence that mitochondrial dysfunction underlies the pathogenesis of TDP-43-related ALS, the roles of wild-type TDP-43 in mitochondria are unknown. Here, we show that the small TDP-43 population present in mitochondria binds directly to a subset of mitochondrial tRNAs and precursor RNA encoded in L-strand mtDNA. Upregulated expression of TDP-43 stabilised the processing intermediates of mitochondrial polycistronic transcripts and their products including the components of electron transport and 16S mt-rRNA, similar to the phenotype observed in cells deficient for mitochondrial RNase P. Conversely, TDP-43 deficiency reduced the population of processing intermediates and impaired mitochondrial function. We propose that TDP-43 has a novel role in maintaining mitochondrial homeostasis by regulating the processing of mitochondrial transcripts.

  10. Enhancement of free tropospheric ozone production by deep convection

    NASA Technical Reports Server (NTRS)

    Pickering, Kenneth E.; Thompson, Anne M.; Scala, John R.; Tao, Wei-Kuo; Simpson, Joanne

    1994-01-01

    It is found from model simulations of trace gas and meteorological data from aircraft campaigns that deep convection may enhance the potential for photochemical ozone production in the middle and upper troposphere by up to a factor of 60. Examination of half a dozen individual convective episodes show that the degree of enhancement is highly variable. Factors affecting enhancement include boundary layer NO(x) mixing ratios, differences in the strength and structure of convective cells, as well as variation in the amount of background pollution already in the free troposphere.

  11. Convection dominated problems

    NASA Technical Reports Server (NTRS)

    Peraire, J.; Morgan, K.; Zienkiewicz, O. C.

    1986-01-01

    The paper surveys the last ten years of activity of the INME Swansea, dealing with problems of convection dominated flow. The basic explicit/implicit characteristic Galerkin process and its application to adaptive mesh refinement used in the solution of realistic problems is focused on.

  12. Feedback control and output feedback control for the stabilisation of switched Boolean networks

    NASA Astrophysics Data System (ADS)

    Li, Fangfei; Yu, Zhaoxu

    2016-02-01

    This paper presents the feedback control and output feedback control for the stabilisation of switched Boolean network. A necessary condition for the existence of a state feedback controller for the stabilisation of switched Boolean networks under arbitrary switching signal is derived first, and constructive procedures for feedback control and output feedback control design are provided. An example is introduced to show the effectiveness of this paper.

  13. Convection and diffusion of cosmic rays in the heliosheath

    NASA Astrophysics Data System (ADS)

    Grzedzielski, S.; Czechowski, A.; Mostafa, I.

    1993-06-01

    Diffusion and convection of both anomalous (ACR) and galactic (GCR) cosmic rays in the heliosheath and adjacent local interstellar plasma flow is calculated by solving the appropriate CR transport equation in the test particle approximation (background plasma flow unaffected). Upon creation at the termination shock the ACR are convected towards the tail region and form there a huge particle reservoir. Ion transcharging on neutral galactic gases leads to apex/antiapex heliosphere asymmetries in the fluxes of energetic neutral atoms.

  14. Anomalously weak solar convection

    PubMed Central

    Hanasoge, Shravan M.; Duvall, Thomas L.

    2012-01-01

    Convection in the solar interior is thought to comprise structures on a spectrum of scales. This conclusion emerges from phenomenological studies and numerical simulations, though neither covers the proper range of dynamical parameters of solar convection. Here, we analyze observations of the wavefield in the solar photosphere using techniques of time-distance helioseismology to image flows in the solar interior. We downsample and synthesize 900 billion wavefield observations to produce 3 billion cross-correlations, which we average and fit, measuring 5 million wave travel times. Using these travel times, we deduce the underlying flow systems and study their statistics to bound convective velocity magnitudes in the solar interior, as a function of depth and spherical-harmonic degree ℓ. Within the wavenumber band ℓ < 60, convective velocities are 20–100 times weaker than current theoretical estimates. This constraint suggests the prevalence of a different paradigm of turbulence from that predicted by existing models, prompting the question: what mechanism transports the heat flux of a solar luminosity outwards? Advection is dominated by Coriolis forces for wavenumbers ℓ < 60, with Rossby numbers smaller than approximately 10-2 at r/R⊙ = 0.96, suggesting that the Sun may be a much faster rotator than previously thought, and that large-scale convection may be quasi-geostrophic. The fact that isorotation contours in the Sun are not coaligned with the axis of rotation suggests the presence of a latitudinal entropy gradient. PMID:22665774

  15. Thermocapillary Convection in Liquid Droplets

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The purpose of this video is to understand the effects of surface tension on fluid convection. The fluid system chosen is the liquid sessile droplet to show the importance in single crystal growth, the spray drying and cooling of metal, and the advance droplet radiators of the space stations radiators. A cross sectional representation of a hemispherical liquid droplet under ideal conditions is used to show internal fluid motion. A direct simulation of buoyancy-dominant convection and surface tension-dominant convection is graphically displayed. The clear differences between two mechanisms of fluid transport, thermocapillary convection, and bouncy dominant convection is illustrated.

  16. Stability Analysis and the Stabilisation of Flexural Toppling Failure

    NASA Astrophysics Data System (ADS)

    Amini, Mehdi; Majdi, Abbas; Aydan, Ömer

    2009-10-01

    Flexural toppling is a mode of failure that may occur in a wide range of layered rock strata in both rock slopes and large underground excavations. Whenever rock mass is composed of a set of parallel discontinuities dipping steeply against the excavated face plane, the rock mass will have the potential of flexural toppling failure as well. In such cases, the rock mass behaves like inclined superimposed cantilever beams that bend under their own weight while transferring the load to the underlying strata. If the bending stress exceeds the rock column’s tensile strength, flexural toppling failure will be initiated. Since the rock columns are “statically indeterminate,” thus, their factors of safety may not be determined solely by equations of equilibrium. The paper describes an analytical model with a sequence of inclined superimposed cantilever rock columns with a potential of flexural topping failure. The model is based on the principle of compatibility equations and leads to a new method by which the magnitudes and points of application of intercolumn forces are determined. On the basis of the proposed model, a safety factor for each rock column can be computed independently. Hence, every rock column will have a unique factor of safety. The least factor of safety that exists in any rock column is selected as the rock mass representative safety factor based on which simple equations are proposed for a conservative rock mass stability analysis and design. As a result, some new relations are established in order to design the length, cross-sectional area and pattern of fully grouted rock bolts for the stabilisation of such rock mass. Finally, the newly proposed equations are compared with the results of existing experimental flexural toppling failure models (base friction and centrifuge tests) for further verification.

  17. The activation energy of stabilised/solidified contaminated soils.

    PubMed

    Chitambira, B; Al-Tabbaa, A; Perera, A S R; Yu, X D

    2007-03-15

    Developing an understanding of the time-related performance of cement-treated materials is essential in understanding their durability and long-term effectiveness. A number of models have been developed to predict this time-related performance. One such model is the maturity concept which involves use of the 'global' activation energy which derives from the Arrhenius equation. The accurate assessment of the activation energy is essential in the realistic modelling of the accelerated ageing of cement-treated soils. Experimentally, this model is applied to a series of tests performed at different elevated temperatures. Experimental work, related to the results of a time-related performance on a contaminated site in the UK treated with in situ stabilisation/solidification was carried out. Three different cement-based grouts were used on two model site soils which were both contaminated with a number of heavy metals and a hydrocarbon. Uncontaminated soils were also tested. Elevated temperatures up to 60 degrees C and curing periods up to 90 days were used. The resulting global activation energies for the uncontaminated and contaminated soils were compared. Lower values were obtained for the contaminated soils reflecting the effect of the contaminants. The resulting equivalent ages for the uncontaminated and contaminated mixes tested were 5.1-7.4 and 0.8-4.1 years, respectively. This work shows how a specific set of contaminants affect the E(a) values for particular cementitious systems and how the maturity concept can be applied to cement-treated contaminated soils.

  18. Stabilisation/solidification of synthetic petroleum drill cuttings.

    PubMed

    Al-Ansary, Marwa S; Al-Tabbaa, Abir

    2007-03-15

    This paper presents the results of an experimental investigation into the use of stabilisation/solidification (S/S) to treat synthetic drill cuttings as a pre-treatment to landfilling or for potential re-use as construction products. Two synthetic mixes were used based on average concentrations of specific contaminates present in typical drill cuttings from the North Sea and the Red Sea areas. The two synthetic drill cuttings contained similar chloride content of 2.03% and 2.13% by weight but different hydrocarbon content of 4.20% and 10.95% by weight, respectively; hence the mixes were denoted as low and high oil content mixes, respectively. A number of conventional S/S binders were tested including Portland cement (PC), lime and blast-furnace slag (BFS), in addition to novel binders such as microsilica and magnesium oxide cement. Physical, chemical and microstructural analyses were used to compare the relative performance of the different binder mixes. The unconfined compressive strength (UCS) values were observed to cover a wide range depending on the binder used. Despite the significant difference in the hydrocarbon content in the two synthetic cuttings, the measured UCS values of the mixes with the same binder type and content were similar. The leachability results showed the reduction of the synthetic drill cuttings to a stable non-reactive hazardous waste, compliant with the UK acceptance criteria for non-hazardous landfills: (a) by most of the binders for chloride concentrations, and (b) by the 20% BFS-PC and 30% PC binders for the low oil content mix. The 30% BFS-PC binder successfully reduced the leached oil concentration of the low oil content mix to inert levels. Finally, the microstructural analysis offered valuable information on the morphology and general behaviour of the mixes that were not depicted by the other tests.

  19. Quantum gate generation by T-sampling stabilisation

    NASA Astrophysics Data System (ADS)

    Silveira, H. B.; Pereira da Silva, P. S.; Rouchon, P.

    2014-06-01

    This paper considers right-invariant and controllable driftless quantum systems with state X(t) evolving on the unitary group U(n) and m inputs u = (u1, …, um). The T-sampling stabilisation problem is introduced and solved: given any initial condition X0 and any goal state ?, find a control law u = u(X, t) such that ? for the closed-loop system. The purpose is to generate arbitrary quantum gates corresponding to ?. This is achieved by the tracking of T-periodic reference trajectories ? of the quantum system that pass by ? using the framework of Coron's return method. The T-periodic reference trajectories ? are generated by applying controls ? that are a sum of a finite number M of harmonics of sin (2πt/T), whose amplitudes are parameterised by a vector a. The main result establishes that, for M big enough, X(jT) exponentially converges towards ? for almost all fixed a, with explicit and completely constructive control laws. This paper also establishes a stochastic version of this deterministic control law. The key idea is to randomly choose a different parameter vector of control amplitudes a = aj at each t = jT, and keeping it fixed for t ∈ [jT, (j + 1)T). It is shown in the paper that X(jT) exponentially converges towards ? almost surely. Simulation results have indicated that the convergence speed of X(jT) may be significantly improved with such stochastic technique. This is illustrated in the generation of the C-NOT quantum logic gate on U(4).

  20. Natural convective mixing flows

    NASA Astrophysics Data System (ADS)

    Ramos, Eduardo; de La Cruz, Luis; del Castillo, Luis

    1998-11-01

    Natural convective mixing flows. Eduardo Ramos and Luis M. de La Cruz, National University of Mexico and Luis Del Castillo San Luis Potosi University. The possibility of mixing a fluid with a natural convective flow is analysed by solving numerically the mass, momentum and energy equations in a cubic container. Two opposite vertical walls of the container are assumed to have temperatures that oscillate as functions of time. The phase of the oscillations is chosen in such a way that alternating corrotating vortices are formed in the cavity. The mixing efficiency of this kind of flow is examined with a Lagrangian tracking technique. This work was partially financed by CONACyT-Mexico project number GE0044

  1. Oxygen abundance and convection

    NASA Astrophysics Data System (ADS)

    Van't Veer, C.; Cayrel, R.

    The triplet IR lines of O I near 777 nm are computed with the Kurucz's code, modified to accept several convection models. The program has been run with the MLT algorithm, with l/H = 1.25 and 0.5, and with the Canuto-Mazzitelli and Canuto-Goldman-Mazzitelli approaches, on a metal-poor turnoff-star model atmosphere with Teff=6200 K, log g = 4.3, [Fe/H]= -1.5. The results show that the differences in equivalent widths for the 4 cases do not exceed 2 per cent (0.3 mA). The convection treatment is therefore not an issue for the oxygen abundance derived from the permitted lines.

  2. On the use of the stabilised Q1P0 element for geodynamical simulations and why this is a bad choice for buyoancy-driven flows.

    NASA Astrophysics Data System (ADS)

    Thieulot, Cedric

    2016-04-01

    Many Finite Element geodynamical codes (Fullsack,1995; Zhong et al., 2000; Thieulot, 2011) are based on bi/tri­-linear velocity constant pressure element (commonly called Q1P0), because of its ease of programming and rather low memory footprint, despite the presence of (pressure) checker­board modes. However, it is long known that the Q1P0 is not inf­-sup stable and does not lend itself to the use of iterative solvers, which makes it a less­ than­ ideal candidate for high resolution 3D models. Other attempts were made more recently (Burstedde et al., 2013; Le Pourhiet et al., 2012) with the use of the stabilised Q1Q1 element (bi/tri­-linear velocity and pressure). This element, while also attractive from an implementation and memory standpoint, suffers a major drawback due to the artificial compressibility introduced by the polynomial projection stabilization. These observations have shifted part of the community towards the Finite Difference Method while the remaining part is now embracing inf­sup stable second­ order elements [May et al., 2015; Kronbichler,2012). Rather surprinsingly, a third option exists when it comes to first ­order elements in the form of the stabilised Q1P0 element, but virtually no literature exists concerning its use for geodynamical applications. I will then recall the specificity of the stabilisation and will carry out a series of benchmark experiments and geodynamical tests to assess its performance. While being shown to work as expected in benchmark experiments, the stabilised Q1P0 element turns out to introduce first-order numerical artefacts in the velocity and pressure solutions in the case of buoyancy-driven flows. Burstedde, C., Stadler, G., Alisic, L., Wilcox, L. C., Tan, E., Gurnis, M., & Ghattas, O. (2013). Large­scale adaptive mantle convection simulation. Geophysical Journal International, 192(3), 889­906. Fullsack, P. (1995). An arbitrary Lagrangian­Eulerian formulation for creeping flows and its application in

  3. Convective injection and photochemical decay of peroxides in the tropical upper troposphere: Methyl iodide as a tracer of marine convection

    NASA Astrophysics Data System (ADS)

    Cohan, Daniel S.; Schultz, Martin G.; Jacob, Daniel J.; Heikes, Brian G.; Blake, Donald R.

    1999-03-01

    The convective injection and subsequent fate of the peroxides H2O2 and CH3OOH in the upper troposphere is investigated using aircraft observations from the NASA Pacific Exploratory Mission-Tropics A (PEM-Tropics A) over the South Pacific up to 12 km altitude. Fresh convective outflow is identified by high CH3I concentrations; CH3I is an excellent tracer of marine convection because of its relatively uniform marine boundary layer concentration, relatively well-defined atmospheric lifetime against photolysis, and high sensitivity of measurement. We find that mixing ratios of CH3OOH in convective outflow at 8-12 km altitude are enhanced on average by a factor of 6 relative to background, while mixing ratios of H2O2 are enhanced by less than a factor of 2. The scavenging efficiency of H2O2 in the precipitation associated with deep convection is estimated to be 55-70%. Scavenging of CH3OOH is negligible. Photolysis of convected peroxides is a major source of the HOx radical family (OH + peroxy radicals) in convective outflow. The timescale for decay of the convective enhancement of peroxides in the upper troposphere is determined using CH3I as a chemical clock and is interpreted using photochemical model calculations. Decline of CH3OOH takes place on a timescale of a 1-2 days, but the resulting HOx converts to H2O2, so H2O2 mixing ratios show no decline for ˜5 days following a convective event. The perturbation to HOx at 8-12 km altitude from deep convective injection of peroxides decays on a timescale of 2-3 days for the PEM-Tropics A conditions.

  4. The Solar Convection Spectrum

    NASA Technical Reports Server (NTRS)

    Bachmann, Kurt T.

    2000-01-01

    I helped to complete a research project with NASA scientists Dr. David Hathaway (my mentor), Rick Bogart, and John Beck from the SOHO/SOI collaboration. Our published paper in 'Solar Physics' was titled 'The Solar Convection Spectrum' (April 2000). Two of my undergraduate students were named on the paper--Gavrav Khutri and Josh Petitto. Gavrav also wrote a short paper for the National Conference of Undergraduate Research Proceedings in 1998 using a preliminary result. Our main result was that we show no evidence of a scale of convection named 'mesogranulation'. Instead, we see only direct evidence for the well-known scales of convection known as graduation and supergranulation. We are also completing work on vertical versus horizontal flow fluxes at the solar surface. I continue to work on phase relationships of solar activity indicators, but I have not yet written a paper with my students on this topic. Along with my research results, I have developed and augmented undergraduate courses at Birmingham-Southern College by myself and with other faculty. We have included new labs and observations, speakers from NASA and elsewhere, new subject material related to NASA and space science. I have done a great deal of work in outreach, mostly as President and other offices in the Birmingham Astronomical Society. My work includes speaking, attracting speakers, giving workshops, and governing.

  5. The Solar Convection Spectrum

    NASA Technical Reports Server (NTRS)

    Bachmann, Kurt T.

    2000-01-01

    I helped to complete a research project with NASA scientists Dr. David Hathaway (my mentor), Rick Bogart, and John Beck from the SOHO/SOI collaboration. Our published paper in 'Solar Physics' was titled 'The Solar Convection Spectrum' (April 2000). Two of my undergraduate students were named on the paper--Gavrav Khutri and Josh Petitto. Gavrav also wrote a short paper for the National Conference of Undergraduate Research Proceedings in 1998 using a preliminary result. Our main result was that we show no evidence of a scale of convection named 'mesogranulation'. Instead, we see only direct evidence for the well-known scales of convection known as graduation and supergranulation. We are also completing work on vertical versus horizontal flow fluxes at the solar surface. I continue to work on phase relationships of solar activity indicators, but I have not yet written a paper with my students on this topic. Along with my research results, I have developed and augmented undergraduate courses at Birmingham-Southern College by myself and with other faculty. We have included new labs and observations, speakers from NASA and elsewhere, new subject material related to NASA and space science. I have done a great deal of work in outreach, mostly as President and other offices in the Birmingham Astronomical Society. My work includes speaking, attracting speakers, giving workshops, and governing.

  6. Thermal Vibrational Convection

    NASA Astrophysics Data System (ADS)

    Gershuni, G. Z.; Lyubimov, D. V.

    1998-08-01

    Recent increasing awareness of the ways in which vibrational effects can affect low-gravity experiments have renewed interest in the study of thermal vibrational convection across a wide range of fields. For example, in applications where vibrational effects are used to provide active control of heat and mass transfer, such as in heat exchangers, stirrers, mineral separators and crystal growth, a sound understanding of the fundamental theory is required. In Thermal Vibrational Convection, the authors present the theory of vibrational effects caused by a static gravity field, and of fluid flows which appear under vibration in fluid-filled cavities. The first part of the book discusses fluid-filled cavities where the fluid motion only appears in the presence of temperature non-uniformities, while the second considers those situations where the vibrational effects are caused by a non-uniform field. Throughout, the authors concentrate on consideration of high frequency vibrations, where averaging methods can be successfully applied in the study of the phenomena. Written by two of the pioneers in this field, Thermal Vibrational Convection will be of great interest to scientists and engineers working in the many areas that are concerned with vibration, and its effect on heat and mass transfer. These include hydrodynamics, hydro-mechanics, low gravity physics and mechanics, and geophysics. The rigorous approach adopted in presenting the theory of this fascinating and highly topical area will facilitate a greater understanding of the phenomena involved, and will lead to the development of more and better-designed experiments.

  7. Rossby numbers of fully convective and partially convective stars

    NASA Astrophysics Data System (ADS)

    Landin, Natália R.; Mendes, Luiz T. S.

    2017-10-01

    In this work, we investigate the stellar magnetic activity in the theoretical point of view, through the use of stellar structure and evolution models. We present theoretical values of convective turnover times and Rossby numbers for low-mass stars, calculated with the ATON stellar structure and evolution code. We concentrate our analysis on fully convective and partially convective stars motivated by recent observations of X-ray emission of slowly rotating fully convective stars, which suggest that the presence of a tachocline is not a central key for magnetic fields generation. We investigate the behavior of the convective turnover time evolution, as well as its radial profile inside the star. A discussion about the location where the convective turnover time is calculated in the stellar interior is also addressed. Our theoretical results are compared to observational data from low-mass stars.

  8. Convection surrounding mesoscale ionospheric flow channels

    NASA Astrophysics Data System (ADS)

    Rinne, Y.; Moen, J.; Baker, J. B. H.; Carlson, H. C.

    2011-05-01

    We evaluate data from the European Incoherent Scatter (EISCAT) Svalbard radar (ESR) and Defense Meteorological Satellite Program (DMSP) spacecraft coupled with data from the Super Dual Auroral Radar Network (SuperDARN) polar cap convection patterns in order to study how the ionospheric convection evolves around a sequence of transient, mesoscale flow channel events in the duskside of the cusp inflow region. On a northwestward convection background for the interplanetary magnetic field (IMF) BY positive and BZ negative, a sequence of three eastward flow channels formed over the course of 1 hour in response to three sharp IMF rotations to IMF BY negative and IMF BZ positive. The first and third channels, due to IMF BY negative periods of ˜13 min and >30 min, respectively, develop in a similar manner: they span the entire ESR field of view and widen poleward with increasing time elapsed since their first appearance until the IMF rotates back. The convection patterns are consistent with the line-of-sight data from the ESR and DMSP within a 10 min adaption time. The flow lines form a twin-vortex flow, with the observed channel being the twin vortices' center flow. The fitting algorithm was pushed to its limits in terms of spatial resolution in this study. During portions of the channel events, the suggested twin-cell flow is not in agreement with our physical interpretation of the flow channels being reconnection events because cell closure is suggested across an anticipated nonreconnecting open-closed boundary. For these segments, we present simulated patterns which have been arrived at by a combination of looking at the raw data and examining the fitted convection patterns.

  9. Global stabilisation for a class of uncertain nonlinear time-delay systems by dynamic state and output feedback

    NASA Astrophysics Data System (ADS)

    Chai, Lin; Qian, Chunjiang

    2015-06-01

    This paper investigates the design problem of constructing the state and output feedback stabilisation controller for a class of uncertain nonlinear systems subject to time-delay. First, a dynamic linear state feedback control law with an adaptive strategy is developed to globally stabilise the uncertain nonlinear time-delay system under a lower-triangular higher-order growth condition. Then, one more challenging problem of the adaptive output feedback stabilisation is addressed, which can globally stabilise the time-delay system when the unmeasurable states linearly grow with rate functions consisting of higher-order output.

  10. Enhanced stabilisation of trapped electron modes by collisional energy scattering in tokamaks

    SciTech Connect

    Manas, P.; Camenen, Y.; Benkadda, S.; Hornsby, W. A.; Peeters, A. G.

    2015-06-15

    The collisional stabilisation via energy scattering and pitch-angle scattering of micro-instabilities in tokamak plasmas is investigated by means of gyrokinetic simulations with a special emphasis on the often neglected energy scattering operator. It is shown that in the linear regime energy scattering has a negligible effect on Ion Temperature Gradient (ITG) modes but enhances the stabilisation of Trapped Electron Modes (TEM) in presence of nonzero ion temperature and density gradients. This stabilisation is sensitive to the model used for the energy restoring term in the collision operator. The contributions of parallel and drift motion to the total growth rate in velocity space are used to characterize the complex stabilisation mechanisms behind pitch-angle and energy scattering for a range of relevant parameters such as the magnetic shear, the collisionality, the logarithmic density gradient, and the logarithmic ion temperature gradient. It is shown that depending on these parameters, energy scattering stabilisation of TEM can be either due to a decrease of the contribution from drifting trapped electrons or to an increase of the contribution from the parallel motion of passing electrons. Finally, for a standard ITG/TEM case, the effect of energy scattering on the nonlinear heat and particle fluxes is investigated.

  11. Effect of particle adsorption rates on the disproportionation process in pickering stabilised bubbles

    NASA Astrophysics Data System (ADS)

    Ettelaie, Rammile; Murray, Brent

    2014-05-01

    The degree of shrinkage of particle stabilised bubbles of various sizes, in a polydisperse bubble dispersion, has been investigated in the light of the finite adsorption times for the particles and the disproportionation kinetics of the bubbles. For the case where the system contains an abundance of particles we find a threshold radius, above which bubbles are stabilised without any significant reduction in their size. Bubbles with an initial radius below this threshold on the other hand undergo a large degree of shrinkage prior to stabilisation. As the ratio of the available particles to the bubbles is reduced, it is shown that the final bubble size, for the larger bubbles in the distribution, becomes increasingly governed by the number of particles, rather than their adsorption time per se. For systems with "adsorption controlled" shrinkage ratio, the final bubble distribution is found to be wider than the initial one, while for a "particle number controlled" case it is actually narrower. Starting from a unimodal bubble size distribution, we predict that at intermediate times, prior to the full stabilisation of all bubbles, the distribution breaks up into a bimodal one. However, the effect is transient and a unimodal final bubble size distribution is recovered, when all the bubbles are stabilised by the particles.

  12. Mesoscale characteristics of monsoonal convection and associated stratiform precipitation

    NASA Technical Reports Server (NTRS)

    Keenan, Thomas D.; Rutledge, Steven A.

    1993-01-01

    Observations undertaken on 12 January 1990 at Darwin (Australia) are used to document the structure of a monsoonal rainband in a low convective available potential energy low-shear tropical environment. Dual-Doppler radar analyses are employed to investigate the structure and kinematics of the convective and stratiform regions. A system with the characteristics of a relatively short-lived squall line in which warm rain processes play a significant role in the production of precipitation is evident. Planetary boundary layer cold-pool production is important in the organization and motion of the system. A trailing stratiform region is evident with a mean updraft-downdraft circulation, but is composed of in situ decaying convective cells. A storm-relative mesoscale cyclonic circulation is also observed within the stratiform cloud. This vortex was maintained by thermodynamically induced midlevel convergence, convectively generated storm-scale circulations, and their interaction with the background monsoon flow.

  13. Semi-convective layer formation

    NASA Astrophysics Data System (ADS)

    Zaussinger, F.; Kupka, F.; Egbers, Ch.; Neben, M.; Hücker, S.; Bahr, C.; Schmitt, M.

    2017-05-01

    Semi-convective mixing, as an example of double-diffusive convection, is of general importance in multi-component fluid mixing processes. In astrophysics it occurs when the mean molecular weight gradient caused by a mixture of light material on top of heavier one counteracts the convective instability caused by a temperature gradient. Direct numerical simulations of double-diffusive fluid flows in a realistic stellar or planetary parameter space are currently non-feasible. Hence, a model describing incompressible semi-convection was developed, which allows to investigate semi-convective layer formation. A detailed parameter study with varying Rayleigh number and stability parameter has been performed for the giant planet case. We conclude that semi-convective layering may not play that important role as suggested in earlier works for the planetary case.

  14. Acetabular Fractures in the Elderly: Midterm Outcomes of Column Stabilisation and Primary Arthroplasty

    PubMed Central

    Ortega-Briones, A.; Smith, S.

    2017-01-01

    Background. Interest in arthroplasty techniques for periarticular or intra-articular fractures in the elderly/osteoporotic patient continues to rise, including for geriatric acetabular fractures. In line with this, many acetabular fracture surgeons are now undertaking acute total hip arthroplasty in elderly/osteoporotic patients. Little is known however of the outcomes of this procedure, beyond the first year after surgery. Questions/Purposes. We determined the clinical outcomes of a series of elderly osteoporotic patients (mean age at surgery 77.4 years) treated for acetabular fractures with column fixation and simultaneous total hip arthroplasty, at a mean of 49 months after surgery. Methods. 24 patients (25 hips) were reviewed at a mean of 49 months after surgery. The surgical technique employed has previously been described. Radiographs were obtained, and clinical outcomes were assessed using Harris Hip Scores and the Merle d'Aubigné score. Results. 14 hips were available for assessment (9 deceased, 2 lost to follow-up). No patient suffered any complications beyond the perioperative period, no acetabular components were loose clinically or on latest radiographs, and the mean Harris Hip Score was 92. All but one patient scored good or excellent on the Merle d'Aubigné score. Conclusions. Column fixation and simultaneous total hip arthroplasty are a viable option for complex geriatric acetabular fractures, with encouraging midterm results. We conclude that THR is a viable long-term solution in this situation provided that the acetabular columns are stabilised prior to implantation, but more research is needed to aid in overall management decision making. PMID:28194414

  15. Zinc carnosine, a health food supplement that stabilises small bowel integrity and stimulates gut repair processes

    PubMed Central

    Mahmood, A; FitzGerald, A J; Marchbank, T; Ntatsaki, E; Murray, D; Ghosh, S; Playford, R J

    2007-01-01

    Background Zinc carnosine (ZnC) is a health food product claimed to possess health‐promoting and gastrointestinal supportive activity. Scientific evidence underlying these claims is, however, limited. Aim To examine the effect of ZnC on various models of gut injury and repair, and in a clinical trial. Methods In vitro studies used pro‐migratory (wounded monolayer) and proliferation ([3H]‐thymidine incorporation) assays of human colonic (HT29), rat intestinal epithelial (RIE) and canine kidney (MDCK) epithelial cells. In vivo studies used a rat model of gastric damage (indomethacin/restraint) and a mouse model of small‐intestinal (indomethacin) damage. Healthy volunteers (n = 10) undertook a randomised crossover trial comparing changes in gut permeability (lactulose:rhamnose ratios) before and after 5 days of indomethacin treatment (50 mg three times a day) with ZnC (37.5 mg twice daily) or placebo coadministration. Results ZnC stimulated migration and proliferation of cells in a dose‐dependent manner (maximum effects in both assays at 100 µmol/l using HT29 cells), causing an approximate threefold increase in migration and proliferation (both p<0.01). Oral ZnC decreased gastric (75% reduction at 5 mg/ml) and small‐intestinal injury (50% reduction in villus shortening at 40 mg/ml; both p<0.01). In volunteers, indomethacin caused a threefold increase in gut permeability in the control arm; lactulose:rhamnose ratios were (mean (standard error of mean)) 0.35 (0.035) before indomethacin treatment and 0.88 (0.11) after 5 days of indomethacin treatment (p<0.01), whereas no significant increase in permeability was seen when ZnC was coadministered. Conclusion ZnC, at concentrations likely to be found in the gut lumen, stabilises gut mucosa. Further studies are warranted. PMID:16777920

  16. Plasma convection in Neptune's magnetosphere

    NASA Technical Reports Server (NTRS)

    Selesnick, R. S.

    1990-01-01

    The magnetosphere of Neptune changes its magnetic configuration continuously as the planet rotates, leading to a strong modulation of the convection electric field. Even though the corotation speed is considerably larger, the modulation causes the small convection speed to have a cumulative effect, much like the acceleration of particles in a cyclotron. A model calculation shows that plasma on one side of the planet convects out of the magnetosphere in a few planetary rotations, while on the other side it convects slowly planetward. The observation of nitrogen ions from a Triton plasma torus may provide a critical test of the model.

  17. Modelling of stellar convection

    NASA Astrophysics Data System (ADS)

    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.

  18. Zoned mantle convection.

    PubMed

    Albarède, Francis; Van Der Hilst, Rob D

    2002-11-15

    We review the present state of our understanding of mantle convection with respect to geochemical and geophysical evidence and we suggest a model for mantle convection and its evolution over the Earth's history that can reconcile this evidence. Whole-mantle convection, even with material segregated within the D" region just above the core-mantle boundary, is incompatible with the budget of argon and helium and with the inventory of heat sources required by the thermal evolution of the Earth. We show that the deep-mantle composition in lithophilic incompatible elements is inconsistent with the storage of old plates of ordinary oceanic lithosphere, i.e. with the concept of a plate graveyard. Isotopic inventories indicate that the deep-mantle composition is not correctly accounted for by continental debris, primitive material or subducted slabs containing normal oceanic crust. Seismological observations have begun to hint at compositional heterogeneity in the bottom 1000 km or so of the mantle, but there is no compelling evidence in support of an interface between deep and shallow mantle at mid-depth. We suggest that in a system of thermochemical convection, lithospheric plates subduct to a depth that depends - in a complicated fashion - on their composition and thermal structure. The thermal structure of the sinking plates is primarily determined by the direction and rate of convergence, the age of the lithosphere at the trench, the sinking rate and the variation of these parameters over time (i.e. plate-tectonic history) and is not the same for all subduction systems. The sinking rate in the mantle is determined by a combination of thermal (negative) and compositional buoyancy and as regards the latter we consider in particular the effect of the loading of plates with basaltic plateaux produced by plume heads. Barren oceanic plates are relatively buoyant and may be recycled preferentially in the shallow mantle. Oceanic plateau-laden plates have a more pronounced

  19. Bidispersive-inclined convection

    PubMed Central

    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

  20. Bidispersive-inclined convection

    NASA Astrophysics Data System (ADS)

    Falsaperla, Paolo; Mulone, Giuseppe; Straughan, Brian

    2016-08-01

    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.

  1. The effect of environmentally relevant conditions on PVP stabilised gold nanoparticles.

    PubMed

    Hitchman, Adam; Smith, Gregory H Sambrook; Ju-Nam, Yon; Sterling, Mark; Lead, Jamie R

    2013-01-01

    Nanoparticles are a major product from the nanotechnology industry and have been shown to have a potentially large environmental exposure and hazard. In this study, sterically stabilised polyvinyl pyrrolidone (PVP) 7 nm gold nanoparticles (NPs) were produced and characterised as prepared by surface plasmon resonance (SPR), size and aggregation, morphology and surface charge. Changes in these properties with changes in environmentally relevant conditions (pH, ionic strength, Ca concentration and fulvic acid presence) were quantified. These sterically stabilised NPs showed no aggregation with changes in pH or inorganic ions, even under high (0.1 M) Ca concentrations. In addition, the presence of fulvic acid resulted in no observable changes in SPR, size, aggregation or surface chemistry, suggesting limited interaction between the PVP stabilised nanoparticles and fulvic acid. Due to the lack of aggregation and interaction, these NPs are expected to be highly mobile and potentially bioavailable in the environment.

  2. Global asymptotic stabilisation in probability of nonlinear stochastic systems via passivity

    NASA Astrophysics Data System (ADS)

    Florchinger, Patrick

    2016-07-01

    The purpose of this paper is to develop a systematic method for global asymptotic stabilisation in probability of nonlinear control stochastic systems with stable in probability unforced dynamics. The method is based on the theory of passivity for nonaffine stochastic differential systems combined with the technique of Lyapunov asymptotic stability in probability for stochastic differential equations. In particular, we prove that a nonlinear stochastic differential system whose unforced dynamics are Lyapunov stable in probability is globally asymptotically stabilisable in probability provided some rank conditions involving the affine part of the system coefficients are satisfied. In this framework, we show that a stabilising smooth state feedback law can be designed explicitly. A dynamic output feedback compensator for a class of nonaffine stochastic systems is constructed as an application of our analysis.

  3. Discrete-time reservoir engineering with entangled bath and stabilising squeezed states

    NASA Astrophysics Data System (ADS)

    Miao, Zibo; Sarlette, Alain

    2017-09-01

    This theoretical proposal investigates how resonant interactions occurring when a harmonic oscillator is fed with a stream of entangled qubits allow us to stabilise squeezed states of the harmonic oscillator. We show that the properties of the squeezed state stabilised by this engineered reservoir, including the squeezing strength, can be tuned at will through the parameters of the ‘input’ qubits, albeit in tradeoff with the convergence rate. We also discuss the influence of the type of entanglement in the input from a pairwise case to a more widely distributed case. This paper can be read either as a proposal to stabilise squeezed states or as a step toward treating quantum systems with time-entangled reservoir inputs.

  4. Observers and output feedback stabilising controllers for nonlinear strict-feedback systems with sampled observation

    NASA Astrophysics Data System (ADS)

    Katayama, Hitoshi

    2016-02-01

    The design of observers and output feedback stabilising controllers for continuous-time strict-feedback systems with sampled observation is considered. First two types of observers are designed. One is a discrete-time semiglobal and practical reduced-order observer for the exact model and the other is a continuous-time semiglobal and practical full-order observer for continuous-time strict feedback systems with sampled observation. Then by combining the designed continuous-time observers and continuous-time state feedback laws that are continuous, zero at the origin, and uniformly globally asymptotically stabilise continuous-time systems, output feedback semiglobally practically uniformly asymptotically stabilising controllers are constructed. Numerical examples are given to illustrate the proposed design of observers and output feedback controllers.

  5. Solidification/stabilisation of liquid oil waste in metakaolin-based geopolymer

    NASA Astrophysics Data System (ADS)

    Cantarel, V.; Nouaille, F.; Rooses, A.; Lambertin, D.; Poulesquen, A.; Frizon, F.

    2015-09-01

    The solidification/stabilisation of liquid oil waste in metakaolin based geopolymer was studied in the present work. The process consists of obtaining a stabilised emulsion of oil in a water-glass solution and then adding metakaolin to engage the setting of a geopolymer block with an oil emulsion stabilised in the material. Geopolymer/oil composites have been made with various oil fraction (7, 14 and 20 vol.%). The rigidity and the good mechanical properties have been demonstrated with compressive strength tests. Leaching tests evidenced the release of oil from the composite material is very limited whereas the constitutive components of the geopolymer (Na, Si and OH-) are involved into diffusion process.

  6. Early Spin-Stabilised Rockets - the Rockets of Bergrat Heinrich Gottlob Kuhn

    NASA Astrophysics Data System (ADS)

    Fricke, H.-D.

    19th century's war rockets were at first stabilised by sticks, but these sticks produced a very uncertain flight path and it often happened that rockets changed their direction and even flew back to their firing position. So very many early inventors in Europe, America, and British-India tried to stabilise the rocket's flight in a better way. They tried fins and even rotation but they did not succeed. It is said in history that William Hale was the first who succeeded in constructing a spin stabilised (i.e. rotating) rocket which worked. But before him, in the thirties of that century, a German amateur rocket inventor succeeded as well and secretly proved his stickless rotating rockets in trials for Prussian officers and some years later officially for Saxon artillery officers. His invention was then bought by the kingdom of Saxony, but these were never use in the field because of lack of money.

  7. Effective solidification/stabilisation of mercury-contaminated wastes using zeolites and chemically bonded phosphate ceramics.

    PubMed

    Zhang, Shaoqing; Zhang, Xinyan; Xiong, Ya; Wang, Guoping; Zheng, Na

    2015-02-01

    In this study, two kinds of zeolites materials (natural zeolite and thiol-functionalised zeolite) were added to the chemically bonded phosphate ceramic processes to treat mercury-contaminated wastes. Strong promotion effects of zeolites (natural zeolite and thiol-functionalised zeolite) on the stability of mercury in the wastes were obtained and these technologies showed promising advantages toward the traditional Portland cement process, i.e. using Portland cement as a solidification agent and natural or thiol-functionalised zeolite as a stabilisation agent. Not only is a high stabilisation efficiency (lowered the Toxicity Characteristic Leaching Procedure Hg by above 10%) obtained, but also a lower dosage of solidification (for thiol-functionalised zeolite as stabilisation agent, 0.5 g g(-1) and 0.7 g g(-1) for chemically bonded phosphate ceramic and Portland cement, respectively) and stabilisation agents (for natural zeolite as stabilisation agent, 0.35 g g(-1) and 0.4 g g(-1) for chemically bonded phosphate ceramic and Portland cement, respectively) were used compared with the Portland cement process. Treated by thiol-functionalised zeolite and chemically bonded phosphate ceramic under optimum parameters, the waste containing 1500 mg Hg kg(-1) passed the Toxicity Characteristic Leaching Procedure test. Moreover, stabilisation/solidification technology using natural zeolite and chemically bonded phosphate ceramic also passed the Toxicity Characteristic Leaching Procedure test (the mercury waste containing 625 mg Hg kg(-1)). Moreover, the presence of chloride and phosphate did not have a negative effect on the chemically bonded phosphate ceramic/thiol-functionalised zeolite treatment process; thus, showing potential for future application in treatment of 'difficult-to-manage' mercury-contaminated wastes or landfill disposal with high phosphate and chloride content. © The Author(s) 2015.

  8. Parameterization of convective clouds, mesoscale convective systems, and convective-generated cirrus

    SciTech Connect

    Cotton, W.R.

    1992-03-03

    A level 2.5w deep convection updraft/downdraft parameterization scheme has been refined and tested against 3D simulations of sea-breeze generated convection over S. Florida. Cases for explicit simulation of MCSs in mid-latitudes and tropics have been encouraging. After a few refinements in those cases, fine resolution explicit simualtions of deep convection and mesoscale, stratiform clouds will be begun.

  9. Active control of convection

    NASA Astrophysics Data System (ADS)

    Singer, Jonathan; Bau, Haim H.

    1991-12-01

    It is demonstrated theoretically that active (feedback) control can be used to alter the characteristics of thermal convection in a toroidal, vertical loop heated from below and cooled from above. As the temperature difference between the heated and cooled sections of the loop increases, the flow in the uncontrolled loop changes from no motion to steady, time-independent motion to temporally oscillatory, chaotic motion. With the use of a feedback controller effecting small perturbations in the boundary conditions, one can maintain the no-motion state at significantly higher temperature differences than the critical one corresponding to the onset of convection in the uncontrolled system. Alternatively, one can maintain steady, time-independent flow under conditions in which the flow would otherwise be chaotic. That is, the controller can be used to suppress chaos. Likewise, it is possible to stabilize periodic nonstable orbits that exist in the chaotic regime of the uncontrolled system. Finally, the controller also can be used to induce chaos in otherwise laminar (fully predictable), nonchaotic flow.

  10. H ∞ output feedback stabilisation of linear discrete-time systems with impulses

    NASA Astrophysics Data System (ADS)

    Zhao, Shouwei; Sun, Jitao; Pan, Shengtao

    2010-10-01

    This article addresses the issue of designing an H ∞ output feedback controller for linear discrete-time systems with impulses. First, a new concept of H ∞ output feedback stabilisation for general linear discrete-time systems with impulses is introduced. Then sufficient linear matrix inequality conditions for the stabilisation and H ∞ performance of general discrete systems with impulses are proposed. In addition, the result is applied to resolve typical output feedback control problems for systems with impulses, such as the decentralised H ∞ output feedback control and the simultaneous H ∞ output feedback control. Finally, a numerical simulation is also presented to illustrate the effectiveness of the proposed results.

  11. Global finite-time output feedback stabilisation for a class of uncertain nontriangular nonlinear systems

    NASA Astrophysics Data System (ADS)

    Zhai, Jun-Yong

    2014-03-01

    This article addresses the problem of global finite-time output feedback stabilisation for a class of nonlinear systems in nontriangular form with an unknown output function. Since the output function is not precisely known, traditional observers based on the output is not implementable. We first design a state observer and use the observer states to construct a controller to globally stabilise the nominal system without the perturbing nonlinearities. Then, we apply the homogeneous domination approach to design a scaled homogeneous observer and controller with an appropriate choice of gain to render the nonlinear system globally finite-time stable.

  12. Robust stabilisation and L2 -gain analysis for switched systems with actuator saturation under asynchronous switching

    NASA Astrophysics Data System (ADS)

    Wang, Juan; Zhao, Jun

    2016-09-01

    Robust stabilisation and L2-gain analysis for a class of switched systems with actuator saturation are studied in this paper. The switching signal of the controllers lags behind that of the system modes, which leads to the asynchronous switching between the candidate controllers and the subsystems. By combining the piecewise Lyapunov function method with the convex hull technique, sufficient conditions in terms of LMIs for the solvability of the robust stabilisation and weighted L2-gain problems are presented respectively under the dwell time scheme. Finally, a numerical example is given to demonstrate the feasibility and effectiveness of the proposed results.

  13. The direct Lyapunov method for the stabilisation of the Furuta pendulum

    NASA Astrophysics Data System (ADS)

    Aguilar-Ibañez, Carlos; Suárez-Castañón, Miguel S.; Gutiérres-Frias, Oscar O.

    2010-11-01

    A nonlinear controller for the stabilisation of the Furuta pendulum is presented. The control strategy is based on a partial feedback linearisation. In a first stage only the actuated coordinate of the Furuta pendulum is linearised. Then, the stabilising feedback controller is obtained by applying the Lyapunov direct method. That is, using this method we prove local asymptotic stability and demonstrate that the closed-loop system has a large region of attraction. The stability analysis is carried out by means of LaSalle's invariance principle. To assess the controller effectiveness, the results of the corresponding numerical simulations are presented.

  14. Frequency stabilisation of multimode helium-neon lasers in laser Doppler flowmetry.

    PubMed

    Deblén, H; Oberg, P A

    1991-09-01

    Low-frequency noise in laser Doppler recordings can be generated because of thermal instabilities in the gas laser cavity. Mode partition noise can be eliminated by thermal stabilisation of the laser cavity. The paper describes a method for closed loop temperature control of the laser cavity. The method uses orthogonal properties of longitudinal laser modes for the temperature control. The signal-to-noise ratio is considerably improved by the procedure. It is recommended that all gas laser equipped Doppler instruments used for precision blood flow studies should be equipped with stabilised laser sources.

  15. Global output feedback stabilisation of nonlinear systems with a unifying linear controller structure

    NASA Astrophysics Data System (ADS)

    Zhang, Xu; Lin, Yan

    2014-02-01

    We investigate the problem of global stabilisation by linear output feedback for a class of uncertain nonlinear systems with zero-dynamics. Compared with the previous works, new dilation-based assumptions are introduced that allow the system nonlinearities and its bounding functions to be coupled with all the states. The nonlinear systems of this paper can be considered as an extended form of some low triangular and feedforward systems. Dynamic gain scaling technique is applied to the controller design and stability analysis. It is proved that with a unifying linear controller structure and flexible adaptive laws for the observer gain, global stabilisation of the nonlinear systems can be achieved.

  16. Stabilisation for switched linear systems with time-varying delay and input saturation

    NASA Astrophysics Data System (ADS)

    Chen, Yonggang; Fei, Shumin; Zhang, Kanjian

    2014-03-01

    This article investigates the stabilisation problems for continuous-time and discrete-time switched systems with time-varying delay and saturated control input. Based on dwell time switching signals and multiple Lyapunov functional method, stabilisation conditions are well obtained in the context of linear matrix inequalities. To estimate attractive regions as large as possible, the feasibility problems are translated into optimisation problems. In addition, the corresponding results are presented for linear time-delay systems and switched delay-free systems, which improve and supplement some existing ones in the literature. Finally, numerical examples and simulations are given to illustrate the effectiveness and values of the proposed results.

  17. Stabilisation analysis for switched neutral systems based on sampled-data control

    NASA Astrophysics Data System (ADS)

    Krishnasamy, R.; Balasubramaniam, P.

    2015-10-01

    In this paper, the problem of stabilisation analysis for switched neutral systems based on sampled-data control and average dwell time approach is investigated. Delay-dependent stabilisation results are derived in terms of linear matrix inequalities by constructing piecewise Lyapunov-Krasovskii functional based on the Wirtinger's inequality. Also, the controller gain matrix is designed by applying an input-delay approach. Further convex combination technique and some integral inequalities are used to derive less conservative results. The effectiveness of the derived results is validated through numerical examples.

  18. Convective dynamos for rotating stars

    NASA Technical Reports Server (NTRS)

    Gilman, P. A.

    1981-01-01

    Global dynamo theory is applied to the problem of why some stars have field reversing dynamos, and others do not. It is argued that convectively driven dynamos are the most likely source of magnetic fields in stars that have convection zones.

  19. Convection and lunar thermal history

    NASA Technical Reports Server (NTRS)

    Cassen, P.; Reynolds, R. T.; Graziani, F.; Summers, A.; Mcnellis, J.; Blalock, L.

    1979-01-01

    The effects of solid interior convection on the thermal history of the moon are examined. Convective models of lunar evolution are calculated to demonstrate the influence of various viscosities, radioactive heat source distributions and initial temperature profiles and tested by means of a thermal history simulation code. Results indicate that solid convection does not necessarily produce a quasi-steady thermal balance between heat sources and surface losses. The state of the lithosphere is found to be sensitive to the efficiency of heat source redistribution, while that of the convecting interior depends primarily on rheology. Interior viscosities of 10 to the 21st to 10 to the 22nd cm/sec are obtained, along with a central temperature above 1100 C. It is suggested that mare flooding could have been the result of magma production by pressure release melting in the upwelling region of convection cells.

  20. Multicloud parametrization of mesoscale convective systems for the ITCZ

    NASA Astrophysics Data System (ADS)

    Khouider, B.; Moncrieff, M. W.

    2014-12-01

    Mesoscale convective systems (MCS), aligned approximately parallel to the background low-level wind shear, are ubiquitous in the Eastern Pacific intertropical convergence zone (ITCZ). They are believed to control the local Hadley circulation and have a nontrivial momentum feedback on the ambient shear. They also play a central role in the two-way interactions between convection and the synoptic and planetary scale waves. They do so by serving as both the building block for organized convection, which involves congestus cloud decks that moisten and precondition the environment for deep convection which in turn is lagged by stratiform anvils, and as a conveyer belt for convective momentum transport (CMT). Here, we propose an extension of the multicloud model of Khouider and Majda (2006) to make the stratiform anvils more sensitive to the background wind shear profile. We do so by invoking two layers of moisture in the free troposphere instead of one, in addition to the boundary layer. Linear stability, in a wind shear background consisting of both mid-level and low-level easterly jets, representing, simultaneously, the Tropical Easterly and African Easterly jets, features the usual synoptic scale instability of the multicloud model plus two new instability bands at the meso-alpha and meso-beta scales, respectively. The meso-alpha and meso-beta modes constitute a paradigm for the dynamics of shear parallel convective systems with the meso-alpha waves being the quasi-stationary systems. In this talk we will present limited domain 3D simulations, without rotation, of realistic shear parallel lines of convection with parallel stratifrom anvils moving eastward, with a steering level in the upper troposphere, as a mesoscale envelope of the individual convective cells moving inwards, with a steering level in the lower troposphere. This provides, among other things, an excellent example of nontrivial CMT effect on the background low-level wind. It results in a narrow channel

  1. Dynamics of Compressible Convection and Thermochemical Mantle Convection

    NASA Astrophysics Data System (ADS)

    Liu, Xi

    The Earth's long-wavelength geoid anomalies have long been used to constrain the dynamics and viscosity structure of the mantle in an isochemical, whole-mantle convection model. However, there is strong evidence that the seismically observed large low shear velocity provinces (LLSVPs) in the lowermost mantle are chemically distinct and denser than the ambient mantle. In this thesis, I investigated how chemically distinct and dense piles influence the geoid. I formulated dynamically self-consistent 3D spherical convection models with realistic mantle viscosity structure which reproduce Earth's dominantly spherical harmonic degree-2 convection. The models revealed a compensation effect of the chemically dense LLSVPs. Next, I formulated instantaneous flow models based on seismic tomography to compute the geoid and constrain mantle viscosity assuming thermochemical convection with the compensation effect. Thermochemical models reconcile the geoid observations. The viscosity structure inverted for thermochemical models is nearly identical to that of whole-mantle models, and both prefer weak transition zone. Our results have implications for mineral physics, seismic tomographic studies, and mantle convection modelling. Another part of this thesis describes analyses of the influence of mantle compressibility on thermal convection in an isoviscous and compressible fluid with infinite Prandtl number. A new formulation of the propagator matrix method is implemented to compute the critical Rayleigh number and the corresponding eigenfunctions for compressible convection. Heat flux and thermal boundary layer properties are quantified in numerical models and scaling laws are developed.

  2. Temperature-Driven Convection

    NASA Astrophysics Data System (ADS)

    Bohan, Richard J.; Vandegrift, Guy

    2003-02-01

    Warm air aloft is stable. This explains the lack of strong winds in a warm front and how nighttime radiative cooling can lead to motionless air that can trap smog. The stability of stratospheric air can be attributed to the fact that it is heated from above as ultraviolet radiation strikes the ozone layer. On the other hand, fluid heated from below is unstable and can lead to Bernard convection cells. This explains the generally turbulent nature of the troposphere, which receives a significant fraction of its heat directly from the Earth's warmer surface. The instability of cold fluid aloft explains the violent nature of a cold front, as well as the motion of Earth's magma, which is driven by radioactive heating deep within the Earth's mantle. This paper describes how both effects can be demonstrated using four standard beakers, ice, and a bit of food coloring.

  3. Geothermal Heating, Convective Flow and Ice Thickness on Mars

    NASA Technical Reports Server (NTRS)

    Rosenberg, N. D.; Travis, B. J.; Cuzzi, J.

    2001-01-01

    Our 3D calculations suggest that hydrothermal circulation may occur in the martian regolith and may significantly thin the surface ice layer on Mars at some locations due to the upwelling of warm convecting fluids driven solely by background geothermal heating. Additional information is contained in the original extended abstract.

  4. Scale-free convection theory

    NASA Astrophysics Data System (ADS)

    Pasetto, Stefano; Chiosi, Cesare; Cropper, Mark; Grebel, Eva K.

    2015-08-01

    Convection is one of the fundamental mechanism to transport energy, e.g., in planetology, oceanography as well as in astrophysics where stellar structure customarily described by the mixing-length theory, which makes use of the mixing-length scale parameter to express the convective flux, velocity, and temperature gradients of the convective elements and stellar medium. The mixing-length scale is taken to be proportional to the local pressure scale height of the star, and the proportionality factor (the mixing-length parameter) must be determined by comparing the stellar models to some calibrator, usually the Sun.No strong arguments exist to claim that the mixing-length parameter is the same in all stars and all evolutionary phases. Because of this, all stellar models in literature are hampered by this basic uncertainty.In a recent paper (Pasetto et al 2014) we presented the first fully analytical scale-free theory of convection that does not require the mixing-length parameter. Our self-consistent analytical formulation of convection determines all the properties of convection as a function of the physical behaviour of the convective elements themselves and the surrounding medium (being it a either a star, an ocean, a primordial planet). The new theory of convection is formulated starting from a conventional solution of the Navier-Stokes/Euler equations, i.e. the Bernoulli equation for a perfect fluid, but expressed in a non-inertial reference frame co-moving with the convective elements. In our formalism, the motion of convective cells inside convective-unstable layers is fully determined by a new system of equations for convection in a non-local and time dependent formalism.We obtained an analytical, non-local, time-dependent solution for the convective energy transport that does not depend on any free parameter. The predictions of the new theory in astrophysical environment are compared with those from the standard mixing-length paradigm in stars with

  5. Scale-free convection theory

    NASA Astrophysics Data System (ADS)

    Pasetto, Stefano; Chiosi, Cesare; Cropper, Mark; Grebel, Eva K.

    Convection is one of the fundamental mechanisms to transport energy, e.g., in planetology, oceanography, as well as in astrophysics where stellar structure is customarily described by the mixing-length theory, which makes use of the mixing-length scale parameter to express the convective flux, velocity, and temperature gradients of the convective elements and stellar medium. The mixing-length scale is taken to be proportional to the local pressure scale height of the star, and the proportionality factor (the mixing-length parameter) must be determined by comparing the stellar models to some calibrator, usually the Sun. No strong arguments exist to claim that the mixing-length parameter is the same in all stars and all evolutionary phases. Because of this, all stellar models in the literature are hampered by this basic uncertainty. In a recent paper (Pasetto et al. 2014) we presented the first fully analytical scale-free theory of convection that does not require the mixing-length parameter. Our self-consistent analytical formulation of convection determines all the properties of convection as a function of the physical behaviour of the convective elements themselves and the surrounding medium (be it a star, an ocean, or a primordial planet). The new theory of convection is formulated starting from a conventional solution of the Navier-Stokes/Euler equations, i.e. the Bernoulli equation for a perfect fluid, but expressed in a non-inertial reference frame co-moving with the convective elements. In our formalism, the motion of convective cells inside convective-unstable layers is fully determined by a new system of equations for convection in a non-local and time dependent formalism. We obtained an analytical, non-local, time-dependent solution for the convective energy transport that does not depend on any free parameter. The predictions of the new theory in astrophysical environment are compared with those from the standard mixing-length paradigm in stars with

  6. Arsenic and copper stabilisation in a contaminated soil by coal fly ash and green waste compost.

    PubMed

    Tsang, Daniel C W; Yip, Alex C K; Olds, William E; Weber, Paul A

    2014-09-01

    In situ metal stabilisation by amendments has been demonstrated as an appealing low-cost remediation strategy for contaminated soil. This study investigated the short-term leaching behaviour and long-term stability of As and Cu in soil amended with coal fly ash and/or green waste compost. Locally abundant inorganic (limestone and bentonite) and carbonaceous (lignite) resources were also studied for comparison. Column leaching experiments revealed that coal fly ash outperformed limestone and bentonite amendments for As stabilisation. It also maintained the As stability under continuous leaching of acidic solution, which was potentially attributed to high-affinity adsorption, co-precipitation, and pozzolanic reaction of coal fly ash. However, Cu leaching in the column experiments could not be mitigated by any of these inorganic amendments, suggesting the need for co-addition of carbonaceous materials that provides strong chelation with oxygen-containing functional groups for Cu stabilisation. Green waste compost suppressed the Cu leaching more effectively than lignite due to the difference in chemical composition and dissolved organic matter. After 9-month soil incubation, coal fly ash was able to minimise the concentrations of As and Cu in the soil solution without the addition of carbonaceous materials. Nevertheless, leachability tests suggested that the provision of green waste compost and lignite augmented the simultaneous reduction of As and Cu leachability in a fairly aggressive leaching environment. These results highlight the importance of assessing stability and remobilisation of sequestered metals under varying environmental conditions for ensuring a plausible and enduring soil stabilisation.

  7. 'A tradition of forgetting': stabilisation and humanitarian action in historical perspective.

    PubMed

    Barakat, Sultan; Deely, Seán; Zyck, Steven A

    2010-10-01

    While subject to increasing articulation and institutionalisation, stabilisation is a long-standing concept and practice that has consistently engaged with and, at times, conflicted with varied understandings of humanitarianism and humanitarian action. Reviewing selected historical experiences, including the Philippines (1898-1902), Algeria (1956-62), Vietnam (1967-75) and El Salvador (1980-92), this paper argues that contemporary models of stabilisation build on and repeat mistakes of the past, particularly the overt securitisation of aid and the perception that humanitarian and development actors are able to purchase security effectively. Where current stabilisation differs from its earlier incarnations, as in the introduction of the private sector and incorporation of humanitarian action into war-fighting strategies, the implications are shown to be troubling if not outright disastrous. T his examination of historical experience, which includes many failures and few, if any, successes, raises the likelihood that it is not solely the design or implementation of individual stability operations that require modification but perhaps the entire concept of stabilisation itself.

  8. A numerical procedure to compute the stabilising solution of game theoretic Riccati equations of stochastic control

    NASA Astrophysics Data System (ADS)

    Dragan, Vasile; Ivanov, Ivan

    2011-04-01

    In this article, the problem of the numerical computation of the stabilising solution of the game theoretic algebraic Riccati equation is investigated. The Riccati equation under consideration occurs in connection with the solution of the H ∞ control problem for a class of stochastic systems affected by state-dependent and control-dependent white noise and subjected to Markovian jumping. The stabilising solution of the considered game theoretic Riccati equation is obtained as a limit of a sequence of approximations constructed based on stabilising solutions of a sequence of algebraic Riccati equations of stochastic control with definite sign of the quadratic part. The proposed algorithm extends to this general framework the method proposed in Lanzon, Feng, Anderson, and Rotkowitz (Lanzon, A., Feng, Y., Anderson, B.D.O., and Rotkowitz, M. (2008), 'Computing the Positive Stabilizing Solution to Algebraic Riccati Equations with an Indefinite Quadratic Term Viaa Recursive Method,' IEEE Transactions on Automatic Control, 53, pp. 2280-2291). In the proof of the convergence of the proposed algorithm different concepts associated the generalised Lyapunov operators as stability, stabilisability and detectability are widely involved. The efficiency of the proposed algorithm is demonstrated by several numerical experiments.

  9. Towards a General Understanding of Carbonyl‐Stabilised Ammonium Ylide‐Mediated Epoxidation Reactions

    PubMed Central

    Novacek, Johanna; Roiser, Lukas; Zielke, Katharina

    2016-01-01

    Abstract The key factors for carbonyl‐stabilised ammonium ylide‐mediated epoxidation reactions were systematically investigated by experimental and computational means and the hereby obtained energy profiles provide explanations for the observed experimental results. In addition, we were able to identify the first tertiary amine‐based chiral auxiliary that allows for high enantioselectivities and high yields for such epoxidation reactions. PMID:27381752

  10. The United Kingdom's stabilisation model and Afghanistan: the impact on humanitarian actors.

    PubMed

    Gordon, Stuart

    2010-10-01

    'Stabilisation' has emerged as a powerful policy framework since 2004. The United Kingdom has been at the forefront of states adopting and developing a 'stabilisation' model and has adapted government policy, processes and structures in its efforts to deliver 'stability' in Afghanistan's Helmand Province and Iraq--as well as elsewhere, such as in Nepal and Sudan. The experience acquired in Helmand in particular is likely to shape both future UK approaches and those of other donor states. The paper argues that the UK's model has evolved significantly since 2006, from a reconstruction strategy towards one that is based on supporting host-nation governance arrangements. Consequently, this paper addresses three principal themes: the origins and conceptualisation of the stabilisation discourse (and its relationship with state-building and early recovery concepts); the role of the UK's experience in Helmand in shaping the British approach; and the impact of the stabilisation model on the humanitarian community. © 2010 The Author(s). Journal compilation © Overseas Development Institute, 2010.

  11. Leaching characteristics of residual lateritic soils stabilised with fly ash and lime for geotechnical applications.

    PubMed

    Goswami, R K; Mahanta, C

    2007-01-01

    The effective use of residual lateritic soils as fill material for various construction activities is often limited by the difficulty in handling them. Attempt to improve their workability with fly ash and lime has shown promising results, although accompanied by risk of release of heavy metal leachates to the groundwater. In the present work, the leaching properties from residual lateritic soils from a part of Northeast India stabilised with fly ash and lime (CaO) was investigated with the help of single batch leaching test and column leaching test for different soil-fly ash-lime mixes. Test results show that the high pH induced by lime treatment of the mixes helps in keeping most of the metals within the stabilised soil matrix. Although the heavy metal concentrations in the leachates were generally within permissible limits, the release response for different metals was different suggesting implications for permeate solutions having metal pre-concentrations, such as those emanating from hazardous landfill sites. The observed characteristics provide insights towards the potential and realistic estimates of leaching of metals and its variation due to change in fly ash and lime content in the stabilised mix. Many of these constituents found in the stabilised soil had a first-flush phenomenon. But, as they occur only for short duration (about 5 pore volumes over 5 days) and at low concentration, dilution effect may eliminate them. The effect of continuous permeation on the flow parameters and the leaching pattern of the mixes have also been highlighted.

  12. Measurement of wind profiles by motion-stabilised ship-borne Doppler lidar

    NASA Astrophysics Data System (ADS)

    Achtert, P.; Brooks, I. M.; Brooks, B. J.; Moat, B. I.; Prytherch, J.; Persson, P. O. G.; Tjernström, M.

    2015-11-01

    Three months of Doppler lidar wind measurements were obtained during the Arctic Cloud Summer Experiment on the icebreaker Oden during the summer of 2014. Such ship-borne Doppler measurements require active stabilisation to remove the effects of ship motion. We demonstrate that the combination of a commercial Doppler lidar with a custom-made motion-stabilisation platform enables the retrieval of wind profiles in the Arctic atmospheric boundary layer during both cruising and ice-breaking with statistical uncertainties comparable to land-based measurements. This held true particularly within the atmospheric boundary layer even though the overall aerosol load was very low. Motion stabilisation was successful for high wind speeds in open water and the resulting wave conditions. It allows for the retrieval of vertical winds with a random error below 0.2 m s-1. The comparison of lidar-measured wind and radio soundings gives a mean bias of 0.3 m s-1 (2°) and a mean standard deviation of 1.1 m s-1 (12°) for wind speed (wind direction). The agreement for wind direction degrades with height. The combination of a motion-stabilised platform with a low-maintenance autonomous Doppler lidar has the potential to enable continuous long-term high-resolution ship-based wind profile measurements over the oceans.

  13. Stabilisation of proteins via mixtures of amino acids during spray drying.

    PubMed

    Ajmera, Ankur; Scherließ, Regina

    2014-03-10

    Biologicals are often formulated as solids in an effort to preserve stability which generally requires stabilising excipients for proper drying. The purpose of this study was to screen amino acids and their combinations for their stabilising effect on proteins during spray drying. Catalase, as model protein, was spray dried in 1+1 or 1+2 ratios with amino acids. Some amino acids namely arginine, glycine and histidine showed good retention of catalase functionality after spray drying and subsequent storage stress. A 1+1 combination of arginine and glycine in a 1+2 ratio with catalase resulted in a tremendously good stabilising effect. Storage at high temperature/humidity also showed beneficial effects of this combination. To evaluate whether this was a general principle, these findings were transferred to an antigenic protein of comparable size and supramolecular structure (haemagglutinin) as well as to a smaller enzyme (lysozyme). Upon spray drying with the combination of amino acids it could be shown that both proteins remain more stable especially after storage compared to the unprotected protein. The combination of arginine and glycine is tailored to the needs of protein stabilisation during spray drying and may hence be utilised in dry powder formulation of biomolecules with superior stability characteristics.

  14. Measurement of wind profiles by motion-stabilised ship-borne Doppler lidar

    NASA Astrophysics Data System (ADS)

    Achtert, P.; Brooks, I. M.; Brooks, B. J.; Moat, B. I.; Prytherch, J.; Persson, P. O. G.; Tjernström, M.

    2015-09-01

    Three months of Doppler lidar wind measurements were obtained during the Arctic Cloud Summer Experiment on the icebreaker Oden during the summer of 2014. Such ship-borne measurements require active stabilisation to remove the effects of ship motion. We demonstrate that the combination of a commercial Doppler lidar with a custom-made motion-stabilisation platform enables the retrieval of wind profiles in the Arctic boundary layer during both cruising and ice-breaking with statistical uncertainties comparable to land-based measurements. This holds particularly within the planetary boundary layer even though the overall aerosol load was very low. Motion stabilisation was successful for high wind speeds in open water and the resulting wave conditions. It allows for the retrieval of winds with a random error below 0.2 m s-1, comparable to the measurement error of standard radiosondes. The combination of a motion-stabilised platform with a low-maintenance autonomous Doppler lidar has the potential to enable continuous long-term high-resolution ship-based wind profile measurements over the oceans.

  15. CONTROL OF LASER RADIATION PARAMETERS: Stabilisation of a laser by the calculated quantum transition frequency

    NASA Astrophysics Data System (ADS)

    Bagaev, S. N.; Dmitriev, A. K.; Lugovoy, A. A.

    2008-01-01

    A method is proposed to stabilise the frequency of a He—Ne laser with an intracavity nonlinear absorption cell by the calculated frequency of the 7→6 transition of F2(2)P(7)ν3 in methane. The long-term frequency stability and reproducibility are measured for a He—Ne/CH4 laser with a telescopic cavity.

  16. The Stabilisation of Enzymes — a Key Factor in the Practical Application of Biocatalysis

    NASA Astrophysics Data System (ADS)

    Martinek, K.; Berezin, I. B.

    1980-05-01

    The present state of the problem of the practical application of biocatalysis is examined and physicochemical approaches whereby the denaturation of enzymes under the influence of elevated temperatures, extreme pH values, and organic solvents can be suppressed are analysed. The general principles of the stabilisation of enzymes are formulated. The bibliography includes 225 references.

  17. Starch nanocrystals as particle stabilisers of oil-in-water emulsions.

    PubMed

    Li, Chen; Li, Yunxing; Sun, Peidong; Yang, Cheng

    2014-07-01

    As an environmentally benign particle emulsifier, starch nanocrystal (SNC) has attracted considerable attention. By submitting waxy maize starch to acid below the gelatinisation temperature of starch, nanoscale crystalline residues, which are SNCs, were separated from starch granules by hydrolysing amorphous regions. The SNC could be used as a particle emulsifier to stabilise emulsions. The SNC could adsorb at the oil-water interface to stabilise oil-in-water emulsions with high stability to coalescence. The creaming of emulsions occurred after homogenisation but decreased with increasing SNC content, which was mainly due to the formation of an inter-particle network in the emulsions. Because of the amount of sulfuric groups at the surface, the SNC was negatively charged. Therefore, at low pH values or high salt content the electrostatic repulsion of the SNC was reduced, which further caused droplet aggregation and an increase in size of the particles in the emulsions stabilised by the SNC. The SNC was an efficient particle emulsifier for preparing Pickering emulsions. The size of emulsions stabilised by the SNC could be tailored by changing the pH value or salt concentration. © 2013 Society of Chemical Industry.

  18. Convection in Type 2 supernovae

    SciTech Connect

    Miller, Douglas Scott

    1993-10-15

    Results are presented here from several two dimensional numerical calculations of events in Type II supernovae. A new 2-D hydrodynamics and neutrino transport code has been used to compute the effect on the supernova explosion mechanism of convection between the neutrinosphere and the shock. This convection is referred to as exterior convection to distinguish it from convection beneath the neutrinosphere. The model equations and initial and boundary conditions are presented along with the simulation results. The 2-D code was used to compute an exterior convective velocity to compare with the convective model of the Mayle and Wilson 1-D code. Results are presented from several runs with varying sizes of initial perturbation, as well as a case with no initial perturbation but including the effects of rotation. The M&W code does not produce an explosion using the 2-D convective velocity. Exterior convection enhances the outward propagation of the shock, but not enough to ensure a successful explosion. Analytic estimates of the growth rate of the neutron finger instability axe presented. It is shown that this instability can occur beneath the neutrinosphere of the proto-neutron star in a supernova explosion with a growth time of ~ 3 microseconds. The behavior of the high entropy bubble that forms between the shock and the neutrinosphere in one dimensional calculations of supernova is investigated. It has been speculated that this bubble is a site for γ-process generation of heavy elements. Two dimensional calculations are presented of the time evolution of the hot bubble and the surrounding stellar material. Unlike one dimensional calculations, the 2D code fails to achieve high entropies in the bubble. When run in a spherically symmetric mode the 2-D code reaches entropies of ~ 200. When convection is allowed, the bubble reaches ~60 then the bubble begins to move upward into the cooler, denser material above it.

  19. Towards 12% stabilised efficiency in single junction polymorphous silicon solar cells: experimental developments and model predictions

    NASA Astrophysics Data System (ADS)

    Abolmasov, Sergey; Cabarrocas, Pere Roca i.; Chatterjee, Parsathi

    2016-01-01

    We have combined recent experimental developments in our laboratory with modelling to devise ways of maximising the stabilised efficiency of hydrogenated amorphous silicon (a-Si:H) PIN solar cells. The cells were fabricated using the conventional plasma enhanced chemical vapour deposition (PECVD) technique at various temperatures, pressures and gas flow ratios. A detailed electrical-optical simulator was used to examine the effect of using wide band gap P-and N-doped μc-SiOx:H layers, as well as a MgF2 anti-reflection coating (ARC) on cell performance. We find that with the best quality a-Si:H so far produced in our laboratory and optimised deposition parameters for the corresponding solar cell, we could not attain a 10% stabilised efficiency due to the high stabilised defect density of a-Si:H, although this landmark has been achieved in some laboratories. On the other hand, a close cousin of a-Si:H, hydrogenated polymorphous silicon (pm-Si:H), a nano-structured silicon thin film produced by PECVD under conditions close to powder formation, has been developed in our laboratory. This material has been shown to have a lower initial and stabilised defect density as well as higher hole mobility than a-Si:H. Modelling indicates that it is possible to attain stabilised efficiencies of 12% when pm-Si:H is incorporated in a solar cell, deposited in a NIP configuration to reduce the P/I interface defects and combined with P- and N-doped μc-SiOx:H layers and a MgF2 ARC.

  20. The Distribution and Stabilisation of Dissolved Fe in Deep-sea Hydrothermal Plumes

    NASA Astrophysics Data System (ADS)

    Bennett, S. A.; Achterberg, E. P.; Connelly, D. P.; Statham, P. J.; Fones, G. R.; German, C. R.

    2007-12-01

    Iron (Fe) is an essential micronutrient for oceanic phytoplankton, yet the debate over its sources and sinks persists. Dissolved Fe(II) in hydrothermal vent fluids is enriched ca. 106-fold over open ocean values, but as vent-fluids enter the base of the water column, abundant polymetallic particulate phases are formed: predominantly Fe-rich sulfides and Fe oxyhydroxides. More recently in hydrothermal plumes, deviation from first order Fe oxidation kinetics has suggested the occurrence of organically stabilised dissolved Fe. Such stabilisation could have implications on the hydrothermal Fe flux to the deep-ocean. To study Fe stabilisation in non-buoyant hydrothermal plumes, we have investigated the plume system at 5°S, Southern Mid-Atlantic Ridge, for dissolved Fe concentrations and Fe-complexing ligands. Six CTD stations were occupied for this study that intercepted non-buoyant plumes. Along-axis flow dominated the dispersion of plume material within the ridge segment and, 2.5 km down-plume from the nearest vent-site, high concentrations of dissolved Fe (20 nM) were still present. These high levels of "dissolved" Fe could be due to the presence of Fe colloids and/or organic Fe complexes. With the use of Competitive Ligand Exchange- Cathodic Stripping Voltammetry (CLE-CSV), we have detected stabilised dissolved Fe complexes within this "dissolved" Fe fraction, on the edges of a plume. We calculate that such a stabilised Fe fraction in hydrothermal plumes, 2.9 to 5.6 times greater than deep-ocean dissolved Fe concentrations (0.7 nM), could be sufficient to provide 10-20% of the global deep-ocean dissolved Fe budget.

  1. [Stabilisation of post-acute stage schizophrenics: from the hospital to the city].

    PubMed

    Dammak, A; Stiti, M; Vacheron, M N

    2014-10-01

    Schizophrenia is a debilitating disease that usually begins in young adulthood, at a time when a person would usually make the transition to independent living, but it can occur at any age. The symptoms and behaviour associated with psychosis and schizophrenia have a distressing impact on the individual, and the family. The course of schizophrenia varies considerably. Although most patients will recover, some will have persisting difficulties or remain vulnerable to future episodes. Therefore, stabilisation of patients in acute phases and avoidance of relapse are major objectives of management throughout the course of this disease. The purpose of this article is to clarify the stabilisation, to study the contributing factors and strategies to implement to achieve stability, through a literature review and key guidelines. Thus, the patient is stabilised when productive symptoms and behavioural problems have decreased. So, the stable phase represents a prolonged period of treatment and rehabilitation during which symptoms are under adequate control and the focus is on improving functioning and recovery. Important predictive criteria of stabilisation include: positive symptoms, the number of previous relapses, cooperation with the patient and family, good adherence to treatment and the use of long acting injectable second-generation antipsychotics. After an acute relapse, the careful organization of the discharge and the development of a proposed ambulatory care in tailored care structures will help consolidate stabilisation and obtain remission. Accepting the idea of continuing treatment is a complex decision in which the psychiatrist plays a central role beside patients and their families. The course of integrated actions on modifiable risk factors such as psychosocial support, addictive comorbidities, identification of prodromes, active information for the therapeutic education of patients and families and access to care will also be supported. This would improve

  2. Nonlinear Convection in Mushy Layers

    NASA Technical Reports Server (NTRS)

    Worster, M. Grae; Anderson, Daniel M.; Schulze, T. P.

    1996-01-01

    When alloys solidify in a gravitational field there are complex interactions between solidification and natural, buoyancy-driven convection that can alter the composition and impair the structure of the solid product. The particular focus of this project has been the compositional convection within mushy layers that occurs in situations where the lighter component of the alloy is rejected into the melt during solidification by cooling from below. The linear stability of such a situation was previously described and has been further elucidated in a number of published articles. Here we describe some recent developments in the study of nonlinear evolution of convection in mushy layers.

  3. Dynamics of convective scale interaction

    NASA Technical Reports Server (NTRS)

    Purdom, James F. W.; Sinclair, Peter C.

    1988-01-01

    Several of the mesoscale dynamic and thermodynamic aspects of convective scale interaction are examined. An explanation of how sounding data can be coupled with satellite observed cumulus development in the warm sector and the arc cloud line's time evolution to develop a short range forecast of expected convective intensity along an arc cloud line. The formative, mature and dissipating stages of the arc cloud line life cycle are discussed. Specific properties of convective scale interaction are presented and the relationship between arc cloud lines and tornado producing thunderstorms is considered.

  4. Dynamics of convective scale interaction

    NASA Technical Reports Server (NTRS)

    Purdom, James F. W.; Sinclair, Peter C.

    1988-01-01

    Several of the mesoscale dynamic and thermodynamic aspects of convective scale interaction are examined. An explanation of how sounding data can be coupled with satellite observed cumulus development in the warm sector and the arc cloud line's time evolution to develop a short range forecast of expected convective intensity along an arc cloud line. The formative, mature and dissipating stages of the arc cloud line life cycle are discussed. Specific properties of convective scale interaction are presented and the relationship between arc cloud lines and tornado producing thunderstorms is considered.

  5. Coupled radiative convective equilibrium simulations with explicit and parameterized convection

    NASA Astrophysics Data System (ADS)

    Hohenegger, Cathy; Stevens, Bjorn

    2016-09-01

    Radiative convective equilibrium has been applied in past studies to various models given its simplicity and analogy to the tropical climate. At convection-permitting resolution, the focus has been on the organization of convection that appears when using fixed sea surface temperature (SST). Here the SST is allowed to freely respond to the surface energy. The goals are to examine and understand the resulting transient behavior, equilibrium state, and perturbations thereof, as well as to compare these results to a simulation integrated with parameterized cloud and convection. Analysis shows that the coupling between the SST and the net surface energy acts to delay the onset of self-aggregation and may prevent it, in our case, for a slab ocean of less than 1 m. This is so because SST gradients tend to oppose the shallow low-level circulation that is associated with the self-aggregation of convection. Furthermore, the occurrence of self-aggregation is found to be necessary for reaching an equilibrium state and avoiding a greenhouse-like climate. In analogy to the present climate, the self-aggregation generates the dry and clear subtropics that allow the system to efficiently cool. In contrast, strong shortwave cloud radiative effects, much stronger than at convection-permitting resolution, prevent the simulation with parameterized cloud and convection to fall into a greenhouse state. The convection-permitting simulations also suggest that cloud feedbacks, as arising when perturbing the equilibrium state, may be very different, and in our case less negative, than what emerges from general circulation models.

  6. Characterizing convective cold pools: Characterizing Convective Cold Pools

    DOE PAGES

    Drager, Aryeh J.; van den Heever, Susan C.

    2017-05-09

    Cold pools produced by convective storms play an important role in Earth's climate system. However, a common framework does not exist for objectively identifying convective cold pools in observations and models. The present study investigates convective cold pools within a simulation of tropical continental convection that uses a cloud-resolving model with a coupled land-surface model. Multiple variables are assessed for their potential in identifying convective cold pool boundaries, and a novel technique is developed and tested for identifying and tracking cold pools in numerical model simulations. This algorithm is based on surface rainfall rates and radial gradients in the densitymore » potential temperature field. The algorithm successfully identifies near-surface cold pool boundaries and is able to distinguish between connected cold pools. Once cold pools have been identified and tracked, composites of cold pool evolution are then constructed, and average cold pool properties are investigated. Wet patches are found to develop within the centers of cold pools where the ground has been soaked with rainwater. These wet patches help to maintain cool surface temperatures and reduce cold pool dissipation, which has implications for the development of subsequent convection.« less

  7. The use of muscle dynamometer for correction of muscle imbalances in the area of deep stabilising spine system.

    PubMed

    Malátová, Renata; Rokytová, Jitka; Stumbauer, Jan

    2013-08-01

    Dorsal pain caused by spine dysfunctions belongs to most frequent chronic illnesses. The muscles of the deep stabilising spine system work as a single functional unit where a dysfunction of only one muscle causes dysfunction of the whole system. Non-invasive, objective and statistically measurable evaluation of the condition of deep stabilising spine system has been made possible by the construction of muscular dynamometer. The aim of our work has been the assessment of deep stabilising spine system by diaphragm test and muscular dynamometer measurements. Based on an initial examination, a 6-week intervention programme was established including instructions on physiological body posture and correct basic body stabilisation for the given exercises and muscle strengthening. Consecutive measurements are then compared with the initial ones. It was presumed that a smaller number of the tested subjects would be able to correctly activate the deep stabilising spine system muscles before the intervention programme when compared to those after the intervention programme. A positive change of 87% has been found. It is clear that if a person actively approaches the programme, then positive adaptation changes on the deep stabilising spine system are seen only after 6 weeks. With the muscular dynamometer, activation of deep stabilising spine system can be objectively measured. Changes between the initial condition of a subject and the difference after some exercise or rehabilitation are especially noticeable. Also, the effect of given therapy or correct performance of the exercise can be followed and observed.

  8. Instrumentation for posterior stabilisation of cervical traumatic and degenerative disorders: bullet-shaped implant and titanium cable.

    PubMed

    Arslantas, A; Cosan, E; Durmaz, R; Ert Lav, K; Atasoy, M; Tel, E

    2001-12-01

    Numerous implants for posterior stabilisation of cervical spine have been described so far. The aims of all these implants and techniques are rigid spinal stabilisation without neurologic damage, restoration of neuroanatomy and excellent radiological studies in postoperative period. The objective of this study was to determine the effectively and clinical safety of this system. We conducted a retrospective analysis of patients treated with posterior stabilisation system for the stabilisation of traumatic and osteodegerative disorders of lower cervical spine in our department. This posterior cervical stabilisation system consist of titanium bullet-shaped implant (Ti-Frame) and titanium cables (sof' wire). All patients underwent only posterior fixation except 2 (anterior decompression and posterior stabilisation in 2 stages) and postoperative early immobilisation was allowed with Philadelphia collar in all patients. At the follow-up period 15.2 months (9-25 months), none of the patients had superficial or deep infection, implant resection or failure. In conclusion, this system (Ti-frame and titanium cables) is a simple, safe and effective system for posterior cervical stabilisation in patients with traumatic and osteodegenerative disorders due to provide rigid fixation and allow CT and MR imaging without the significant artifact.

  9. The time taken for the regional distribution of ventilation to stabilise: an investigation using electrical impedance tomography.

    PubMed

    Caruana, L; Paratz, J D; Chang, A; Barnett, A G; Fraser, J F

    2015-01-01

    Electrical impedance tomography is a novel technology capable of quantifying ventilation distribution in the lung in real time during various therapeutic manoeuvres. The technique requires changes to the patient's position to place the electrical impedance tomography electrodes circumferentially around the thorax. The impact of these position changes on the time taken to stabilise the regional distribution of ventilation determined by electrical impedance tomography is unknown. This study aimed to determine the time taken for the regional distribution of ventilation determined by electrical impedance tomography to stabilise after changing position. Eight healthy, male volunteers were connected to electrical impedance tomography and a pneumotachometer. After 30 minutes stabilisation supine, participants were moved into 60 degrees Fowler's position and then returned to supine. Thirty minutes was spent in each position. Concurrent readings of ventilation distribution and tidal volumes were taken every five minutes. A mixed regression model with a random intercept was used to compare the positions and changes over time. The anterior-posterior distribution stabilised after ten minutes in Fowler's position and ten minutes after returning to supine. Left-right stabilisation was achieved after 15 minutes in Fowler's position and supine. A minimum of 15 minutes of stabilisation should be allowed for spontaneously breathing individuals when assessing ventilation distribution. This time allows stabilisation to occur in the anterior-posterior direction as well as the left-right direction.

  10. Bistability Controlled by Convection in a Pattern-Forming System

    NASA Astrophysics Data System (ADS)

    Marsal, Nicolas; Weicker, Lionel; Wolfersberger, Delphine; Sciamanna, Marc

    2017-01-01

    We analyze the transition from convective to absolute dynamical instabilities in a nonlinear optical system forming patterns, i.e., a photorefractive crystal in a single feedback configuration. We demonstrate that the convective regime is directly related to the bistability area in which the homogeneous steady state coexists with a pattern solution. Outside this domain, the system exhibits either a homogeneous steady state or an absolute dynamical regime. We evidence that the bistability area can be greatly increased by adjusting the mirror tilt angle and/or by applying an external background illumination on the photorefractive crystal.

  11. Stochastic Microhertz Gravitational Radiation from Stellar Convection

    NASA Astrophysics Data System (ADS)

    Bennett, M. F.; Melatos, A.

    2014-09-01

    High Reynolds-number turbulence driven by stellar convection in main-sequence stars generates stochastic gravitational radiation. We calculate the wave-strain power spectral density as a function of the zero-age main-sequence mass for an individual star and for an isotropic, universal stellar population described by the Salpeter initial mass function and redshift-dependent Hopkins-Beacom star formation rate. The spectrum is a broken power law, which peaks near the turnover frequency of the largest turbulent eddies. The signal from the Sun dominates the universal background. For the Sun, the far-zone power spectral density peaks at S(f peak) = 5.2 × 10-52 Hz-1 at frequency f peak = 2.3 × 10-7 Hz. However, at low observing frequencies f < 3 × 10-4 Hz, the Earth lies inside the Sun's near zone and the signal is amplified to S near(f peak) = 4.1 × 10-27 Hz-1 because the wave strain scales more steeply with distance (vpropd -5) in the near zone than in the far zone (vpropd -1). Hence the Solar signal may prove relevant for pulsar timing arrays. Other individual sources and the universal background fall well below the projected sensitivities of the Laser Interferometer Space Antenna and next-generation pulsar timing arrays. Stellar convection sets a fundamental noise floor for more sensitive stochastic gravitational-wave experiments in the more distant future.

  12. Convection, nucleosynthesis, and core collapse

    NASA Technical Reports Server (NTRS)

    Bazan, Grant; Arnett, David

    1994-01-01

    We use a piecewise parabolic method hydrodynamics code (PROMETHEUS) to study convective burning in two dimensions in an oxygen shell prior to core collapse. Significant mixing beyond convective boundaries determined by mixing-length theory brings fuel (C-12) into the convective regon, causing hot spots of nuclear burning. Plumes dominate the velocity structure. Finite perturbations arise in a region in which O-16 will be explosively burned to Ni-56 when the star explodes; the resulting instabilities and mixing are likely to distribute Ni-56 throughout the supernova envelope. Inhomogeneities in Y(sub e) may be large enough to affect core collapse and will affect explosive nucleosynthesis. The nature of convective burning is dramatically different from that assumed in one-dimensional simulations; quantitative estimates of nucleosynthetic yields, core masses, and the approach to core collapse will be affected.

  13. Realistic Solar Surface Convection Simulations

    NASA Technical Reports Server (NTRS)

    Stein, Robert F.; Nordlund, Ake

    2000-01-01

    We perform essentially parameter free simulations with realistic physics of convection near the solar surface. We summarize the physics that is included and compare the simulation results with observations. Excellent agreement is obtained for the depth of the convection zone, the p-mode frequencies, the p-mode excitation rate, the distribution of the emergent continuum intensity, and the profiles of weak photospheric lines. We describe how solar convection is nonlocal. It is driven from a thin surface thermal boundary layer where radiative cooling produces low entropy gas which forms the cores of the downdrafts in which most of the buoyancy work occurs. We show that turbulence and vorticity are mostly confined to the intergranular lanes and underlying downdrafts. Finally, we illustrate our current work on magneto-convection.

  14. Convection and chaos in fluids

    SciTech Connect

    Bhattacharjee, J.

    1987-01-01

    This book describes some of the progress made in understanding the phenomena of various hydrodynamic instabilities for the past 30 years. Among them the exact results for the onset of Rayleigh-Benard convection are discussed. Approximate techniques like the amplitude equations and few-mode truncations are treated at length. The reviews of the routes to chaos in dynamical systems and the characteristics of the chaotic state are also discussed here. Finally, certain features of the Taylor Couette instability and the effect of parametric modulation on hydrodynamic instabilities are also included. This book also discusses the results at all stages of experiments. Contents: Onset of Convection: Rayleigh-Benard Geometry for Simple Fluids; Amplitude Equations; Few-Mode Truncation: Lorentz Model; Characteristics of Chaotic Behavior, Routes to Chaos; On Experiments; Thermohaline Systems; Onset of Convection; Binary Liquids; Nonlinear Effects; Taylor-Couette flow; Magnetohydrodynamic Convection; Modulated Systems.

  15. Parameterization of precipitating shallow convection

    NASA Astrophysics Data System (ADS)

    Seifert, Axel

    2015-04-01

    Shallow convective clouds play a decisive role in many regimes of the atmosphere. They are abundant in the trade wind regions and essential for the radiation budget in the sub-tropics. They are also an integral part of the diurnal cycle of convection over land leading to the formation of deeper modes of convection later on. Errors in the representation of these small and seemingly unimportant clouds can lead to misforecasts in many situations. Especially for high-resolution NWP models at 1-3 km grid spacing which explicitly simulate deeper modes of convection, the parameterization of the sub-grid shallow convection is an important issue. Large-eddy simulations (LES) can provide the data to study shallow convective clouds and their interaction with the boundary layer in great detail. In contrast to observation, simulations provide a complete and consistent dataset, which may not be perfectly realistic due to the necessary simplifications, but nevertheless enables us to study many aspects of those clouds in a self-consistent way. Today's supercomputing capabilities make it possible to use domain sizes that not only span several NWP grid boxes, but also allow for mesoscale self-organization of the cloud field, which is an essential behavior of precipitating shallow convection. By coarse-graining the LES data to the grid of an NWP model, the sub-grid fluctuations caused by shallow convective clouds can be analyzed explicitly. These fluctuations can then be parameterized in terms of a PDF-based closure. The necessary choices for such schemes like the shape of the PDF, the number of predicted moments, etc., will be discussed. For example, it is shown that a universal three-parameter distribution of total water may exist at scales of O(1 km) but not at O(10 km). In a next step the variance budgets of moisture and temperature in the cloud-topped boundary layer are studied. What is the role and magnitude of the microphysical correlation terms in these equations, which

  16. Convective heat flow probe

    DOEpatents

    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.

  17. Convective heat flow probe

    DOEpatents

    Dunn, J.C.; Hardee, H.C.; Striker, R.P.

    1984-01-09

    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 packet-type seals are provided along the probe above and below the heater pads.

  18. Influence of convection on microstructure

    NASA Technical Reports Server (NTRS)

    Wilcox, William R.; Regel, Liya L.

    1994-01-01

    The primary motivation for this research was to determine the cause for space processing altering the microstructure of some eutectics, especially the MnBi-Bi eutectic. Four primary hypotheses were to be tested under this current grant: (1) A fibrous microstructure is much more sensitive to convection than a lamellar microstructure, which was assumed in our prior theoretical treatment. (2) An interface with one phase projecting out into the melt is much more sensitive to convection than a planar interface, which was assumed in our prior theoretical treatment. (3) The Soret effect is much more important in the absence of convection and has a sufficiently large influence on microstructure that its action can explain the flight results. (4) The microstructure is much more sensitive to convection when the composition of the bulk melt is off eutectic. These hypotheses were tested. It was concluded that none of these can explain the Grumman flight results. Experiments also were performed on the influence of current pulses on MnBi-Bi microstructure. A thorough review was made of all experimental results on the influence of convection on the fiber spacing in rod eutectics, including results from solidification in space or at high gravity, and use of mechanical stirring or a magnetic field. Contradictory results were noted. The predictions of models for convective influences were compared with the experimental results. Vigorous mechanical stirring appears to coarsen the microstructure by altering the concentration field in front of the freezing interface. Gentle convection is believed to alter the microstructure of a fibrous eutectic only when it causes a fluctuating freezing rate with a system for which the kinetics of fiber branching differs from that for fiber termination. These fluctuations may cause the microstructure to coarsen or to become finer, depending on the relative kinetics of these processes. The microstructure of lamellar eutectics is less sensitive to

  19. Convection coefficients at building surfaces

    NASA Astrophysics Data System (ADS)

    Kammerud, R. C.; Altmayer, E.; Bauman, F. S.; Gadgil, A.; Bohn, M.

    1982-09-01

    Correlations relating the rate of heat transfer from the surfaces of rooms to the enclosed air are being developed, based on empirical and analytic examinations of convection in enclosures. The correlations express the heat transfer rate in terms of boundary conditions relating to room geometry and surface temperatures. Work to date indicates that simple convection coefficient calculation techniques can be developed, which significantly improve accuracy of heat transfer predictions in comparison with the standard calculations recommended by ASHRAE.

  20. Delay-dependent stabilisation of systems with time-delayed state and control: application to a quadruple-tank process

    NASA Astrophysics Data System (ADS)

    El Haoussi, F.; Tissir, E. H.; Tadeo, F.; Hmamed, A.

    2011-01-01

    This work presents a study on the stabilisation of linear systems with delays in the control and states, motivated by a benchmark problem from the literature (a quadruple-tank system). A methodology for the stabilisation of this kind of systems is presented, expressing the conditions as LMIs. Using several examples from the literature, it is shown that the proposed stabilisation theorem is less conservative than previous results. Finally, the technique is applied to the benchmark problem, showing how it is possible to derive efficient controllers for realistic problems, using the proposed technique.

  1. Isentropic Analysis of Convective Motions

    NASA Technical Reports Server (NTRS)

    Pauluis, Olivier M.; Mrowiec, Agnieszka A.

    2013-01-01

    This paper analyzes the convective mass transport by sorting air parcels in terms of their equivalent potential temperature to determine an isentropic streamfunction. By averaging the vertical mass flux at a constant value of the equivalent potential temperature, one can compute an isentropic mass transport that filters out reversible oscillatory motions such as gravity waves. This novel approach emphasizes the fact that the vertical energy and entropy transports by convection are due to the combination of ascending air parcels with high energy and entropy and subsiding air parcels with lower energy and entropy. Such conditional averaging can be extended to other dynamic and thermodynamic variables such as vertical velocity, temperature, or relative humidity to obtain a comprehensive description of convective motions. It is also shown how this approach can be used to determine the mean diabatic tendencies from the three-dimensional dynamic and thermodynamic fields. A two-stream approximation that partitions the isentropic circulation into a mean updraft and a mean downdraft is also introduced. This offers a straightforward way to identify the mean properties of rising and subsiding air parcels. The results from the two-stream approximation are compared with two other definitions of the cloud mass flux. It is argued that the isentropic analysis offers a robust definition of the convective mass transport that is not tainted by the need to arbitrarily distinguish between convection and its environment, and that separates the irreversible convective overturning fromoscillations associated with gravity waves.

  2. Convection wave studies over land and sea

    NASA Technical Reports Server (NTRS)

    Kuettner, Joachim; Grossmann, Robert

    1991-01-01

    Preliminary results of recent case studies conducted over land and sea are given. Two dimensional convection (roll vortex/cloudstreet) and three dimensional convection in the underlying boundary layer are dealt with. Vertical momentum flux profiles and time series of important parameters and vertical soundings taken in the experiment area are shown. The three cases described show that convection waves occur over land and over ocean, over three dimensional convection and over two dimensional convection.

  3. Observation of deep convection initiation from shallow convection environment

    NASA Astrophysics Data System (ADS)

    Lothon, Marie; Couvreux, Fleur; Guichard, Françoise; Campistron, Bernard; Chong, Michel; Rio, Catherine; Williams, Earle

    2010-05-01

    In the afternoon of 10 July 2006, deep convective cells initiated right in the field of view of the Massachusetts Institute Technology (MIT) C-band Doppler radar. This radar, with its 3D exploration at 10 min temporal resolution and 250 m radial resolution, allows us to track the deep convective cells and also provides clear air observations of the boundary layer structure prior to deep convection initiation. Several other observational platforms were operating then which allow us to thoroughly analyse this case: Vertically pointing aerosol lidar, W-band radar and ceilometer from the ARM Mobile Facility, along with radiosoundings and surface measurements enable us to describe the environment, from before their initiation to after the propagation of of one propagating cell that generated a circular gust front very nicely caught by the MIT radar. The systems considered here differ from the mesoscale convective systems which are often associated with African Easterly Waves, increasing CAPE and decreasing CIN. The former have smaller size, and initiate more locally, but there are numerous and still play a large role in the atmospheric circulation and scalar transport. Though, they remain a challenge to model. (See the presentation by Guichard et al. in the same session, for a model set up based on the same case, with joint single-column model and Large Eddy Simulation, which aims at better understanding and improving the parametrisation of deep convection initiation.) Based on the analysis of the observations mentioned above, we consider here the possible sources of deep convection initiation that day, which showed a typical boundary-layer growth in semi-arid environment, with isolated deep convective events.

  4. FLUX EMERGENCE IN A MAGNETIZED CONVECTION ZONE

    SciTech Connect

    Pinto, R. F.; Brun, A. S.

    2013-07-20

    We study the influence of a dynamo magnetic field on the buoyant rise and emergence of twisted magnetic flux ropes and their influence on the global external magnetic field. We ran three-dimensional MHD numerical simulations using the ASH code (anelastic spherical harmonics) and analyzed the dynamical evolution of such buoyant flux ropes from the bottom of the convection zone until the post-emergence phases. The global nature of this model can only very crudely and inaccurately represent the local dynamics of the buoyant rise of the implanted magnetic structure, but nonetheless allows us to study the influence of global effects, such as self-consistently generated differential rotation and meridional circulation, and of Coriolis forces. Although motivated by the solar context, this model cannot be thought of as a realistic model of the rise of magnetic structures and their emergence in the Sun, where the local dynamics are completely different. The properties of initial phases of the buoyant rise are determined essentially by the flux-rope's properties and the convective flows and consequently are in good agreement with previous studies. However, the effects of the interaction of the background dynamo field become increasingly strong as the flux ropes evolve. During the buoyant rise across the convection zone, the flux-rope's magnetic field strength scales as B{proportional_to}{rho}{sup {alpha}}, with {alpha} {approx}< 1. An increase of radial velocity, density, and current density is observed to precede flux emergence at all longitudes. The geometry, latitude, and relative orientation of the flux ropes with respect to the background magnetic field influences the resulting rise speeds, zonal flow amplitudes (which develop within the flux ropes), and the corresponding surface signatures. This influences the morphology, duration and amplitude of the surface shearing, and the Poynting flux associated with magnetic flux-rope emergence. The emerged magnetic flux

  5. Radiative-convective instability

    NASA Astrophysics Data System (ADS)

    Emanuel, Kerry; Wing, Allison A.; Vincent, Emmanuel M.

    2014-03-01

    equilibrium (RCE) is a simple paradigm for the statistical equilibrium the earth's climate would exhibit in the absence of lateral energy transport. It has generally been assumed that for a given solar forcing and long-lived greenhouse gas concentration, such a state would be unique, but recent work suggests that more than one stable equilibrium may be possible. Here we show that above a critical specified sea surface temperature, the ordinary RCE state becomes linearly unstable to large-scale overturning circulations. The instability migrates the RCE state toward one of the two stable equilibria first found by Raymond and Zeng (2000). It occurs when the clear-sky infrared opacity of the lower troposphere becomes so large, owing to high water vapor concentration, that variations of the radiative cooling of the lower troposphere are governed principally by variations in upper tropospheric water vapor. We show that the instability represents a subcritical bifurcation of the ordinary RCE state, leading to either a dry state with large-scale descent, or to a moist state with mean ascent; these states may be accessed by finite amplitude perturbations to ordinary RCE in the subcritical state, or spontaneously in the supercritical state. As first suggested by Raymond (2000) and Sobel et al. (2007), the latter corresponds to the phenomenon of self-aggregation of moist convection, taking the form of cloud clusters or tropical cyclones. We argue that the nonrobustness of self-aggregation in cloud system resolving models may be an artifact of running such models close to the critical temperature for instability.

  6. The effect of external heat transfer on thermal explosion in a spherical vessel with natural convection.

    PubMed

    Campbell, A N

    2015-07-14

    When any exothermic reaction proceeds in an unstirred vessel, natural convection may develop. This flow can significantly alter the heat transfer from the reacting fluid to the environment and hence alter the balance between heat generation and heat loss, which determines whether or not the system will explode. Previous studies of the effects of natural convection on thermal explosion have considered reactors where the temperature of the wall of the reactor is held constant. This implies that there is infinitely fast heat transfer between the wall of the vessel and the surrounding environment. In reality, there will be heat transfer resistances associated with conduction through the wall of the reactor and from the wall to the environment. The existence of these additional heat transfer resistances may alter the rate of heat transfer from the hot region of the reactor to the environment and hence the stability of the reaction. This work presents an initial numerical study of thermal explosion in a spherical reactor under the influence of natural convection and external heat transfer, which neglects the effects of consumption of reactant. Simulations were performed to examine the changing behaviour of the system as the intensity of convection and the importance of external heat transfer were varied. It was shown that the temporal development of the maximum temperature in the reactor was qualitatively similar as the Rayleigh and Biot numbers were varied. Importantly, the maximum temperature in a stable system was shown to vary with Biot number. This has important consequences for the definitions used for thermal explosion in systems with significant reactant consumption. Additionally, regions of parameter space where explosions occurred were identified. It was shown that reducing the Biot number increases the likelihood of explosion and reduces the stabilising effect of natural convection. Finally, the results of the simulations were shown to compare favourably with

  7. A Generalized Simple Formulation of Convective Adjustment Timescale for Cumulus Convection Parameterizations

    EPA Science Inventory

    Convective adjustment timescale (τ) for cumulus clouds is one of the most influential parameters controlling parameterized convective precipitation in climate and weather simulation models at global and regional scales. Due to the complex nature of deep convection, a pres...

  8. Solar Surface Magneto-Convection

    NASA Astrophysics Data System (ADS)

    Stein, Robert F.

    2012-12-01

    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 nonlocal 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 the atmosphere. Narrow

  9. Femtosecond fibre laser stabilisation to an optical frequency standard using a KTP electro-optic crystal

    SciTech Connect

    Nyushkov, B N; Pivtsov, V S; Koliada, N A; Kaplun, A B; Meshalkin, A B

    2015-05-31

    A miniature intracavity KTP-based electro-optic phase modulator has been developed which can be used for effective stabilisation of an optical frequency comb of a femtosecond erbiumdoped fibre laser to an optical frequency standard. The use of such an electro-optic modulator (EOM) has made it possible to extend the working frequency band of a phase-locked loop system for laser stabilisation to several hundred kilohertz. We demonstrate that the KTP-based EOM is sufficiently sensitive even at a small optical length, which allows it to be readily integrated into cavities of femtosecond fibre lasers with high mode frequency spacings (over 100 MHz). (extreme light fields and their applications)

  10. A simplified Galveston technique for the stabilisation of pathological fractures of the sacrum.

    PubMed

    McGee, A M; Bache, C E; Spilsbury, J; Marks, D S; Stirling, A J; Thompson, A G

    2000-10-01

    Mechanical stabilisation of pathological fractures of the sacrum is technically challenging. There is often inadequate purchase in the sacrum, and stabilisation has to be achieved between the lumbar vertebrae and ilium. We present a simplification of the Galveston technique. We treated a total of six patients with this technique, four for metastatic disease and two for primary tumours. Our technique consists of the formation of a proximal stable construct using ISOLA pedicle screws linked distally using a modular system of connectors to threaded iliac bolts with cross linkages. Neurological decompression and fusion was performed as appropriate. The benefits of this method are: ease of access to the ilium, a solid purchase to the ilium, less rod contouring and shorter operating time. We have had no operative complications from this procedure. All patients were discharged home mobile, with a reduced opiate requirement.

  11. Robust stabilisation of time-varying delay systems with probabilistic uncertainties

    NASA Astrophysics Data System (ADS)

    Jiang, Ning; Xiong, Junlin; Lam, James

    2016-09-01

    For robust stabilisation of time-varying delay systems, only sufficient conditions are available to date. A natural question is as follows: if the existing sufficient conditions are not satisfied, and hence no controllers can be found, what can one do to improve the stability performance of time-varying delay systems? This question is addressed in this paper when there is a probabilistic structure on the parameter uncertainty set. A randomised algorithm is proposed to design a state-feedback controller, which stabilises the system over the uncertainty domain in a probabilistic sense. The capability of the designed controller is quantified by the probability of stability of the resulting closed-loop system. The accuracy of the solution obtained from the randomised algorithm is also analysed. Finally, numerical examples are used to illustrate the effectiveness and advantages of the developed controller design approach.

  12. Novel Xylene-linked Maltoside Amphiphiles (XMAs) for Membrane Protein Stabilisation

    PubMed Central

    Cho, Kyung Ho; Du, Yang; Scull, Nicola J; Hariharan, Parameswaran; Gotfryd, Kamil; Loland, Claus J; Guan, Lan; Byrne, Bernadette; Kobilka, Brian K; Chae, Pil Seok

    2015-01-01

    Membrane proteins are key functional players in biological systems. These bio-macromolecules contain both hydrophilic and hydrophobic regions and thus amphipathic molecules are necessary to extract membrane proteins from their native lipid environments and stabilise them in aqueous solutions. Conventional detergents are commonly used for membrane protein manipulation, but membrane proteins surrounded by these agents often undergo denaturation and aggregation. In this study, we developed a novel class of maltoside-bearing amphiphiles, with a xylene linker in the central region, designated xylene-linked maltoside amphiphiles (XMAs). When these novel agents were evaluated with a number of membrane proteins, we found that XMA-4 and XMA-5 have particularly favorable efficacy with respect to membrane protein stabilisation, indicating that these agents hold significant potential for membrane protein structural study. PMID:26013293

  13. Global stabilisation of the PVTOL aircraft with lateral force coupling and bounded inputs

    NASA Astrophysics Data System (ADS)

    López-Araujo, D. J.; Zavala-Río, A.; Fantoni, I.; Salazar, S.; Lozano, R.

    2010-07-01

    This work is devoted to prove that the nonlinear control scheme previously proposed by Zavala-Río, Fantoni and Lozano for the global stabilisation of the planar vertical take-off and landing (PVTOL) aircraft with bounded inputs neglecting the lateral force coupling is robust with respect to the parameter characterising such a lateral force coupling, ɛ, as long as such a parameter takes small enough values. In other words, global stabilisation is achieved even if ɛ > 0, provided that such a parameter be sufficiently small. As far as the authors are aware, such a property has not been proved in other existing control schemes when the value of ɛ is not known. The presented methodology is based on the use of embedded saturation functions. Furthermore, experimental results of the control algorithm implemented on a real prototype are presented.

  14. Observer-based stabilisation of a class of nonlinear systems in the presence of measurement delay

    NASA Astrophysics Data System (ADS)

    He, Qing; Liu, Jinkun

    2016-06-01

    In this paper, the stabilising control problem for a class of nonlinear system in the presence of measurement delay is addressed. A full-order observer is designed to eliminate the effect of variable output time delay, which is bounded and known. Then, the estimated states are utilised for the state feedback control law to stabilise the considered control system. Lyapunov-Razumikhin approach is employed to analyse the stability of the closed-loop system. Unlike the previous work, the exponential convergence of the estimation error is ensured, rather than asymptotic convergence, by designing a delay-dependent gain of the observer. Moreover, comparison with similar work is also made in simulation to illustrate the effectiveness of the proposed strategy.

  15. Output-feedback stabilisation for a class of switched nonlinear systems with unknown control coefficients

    NASA Astrophysics Data System (ADS)

    Long, Lijun; Zhao, Jun

    2013-03-01

    This article investigates the problem of global stabilisation for a class of switched nonlinear systems with unknown control coefficients by output feedback. Full state measurements are unavailable. We first show that via a coordinate transformation, the unknown control coefficients are lumped together and the original switched nonlinear system is transformed into a new switched nonlinear system for which control design becomes feasible. Second, for the new switched nonlinear system, based on backstepping, we design output-feedback controllers for subsystems and construct a common Lyapunov function, which rely on the designed state observer, to guarantee asymptotic stability of the closed-loop system under arbitrary switchings. Finally, as an application of the proposed design method, global stabilisation of a mass-spring-damper system is achieved by output feedback.

  16. Identification of a Lead Candidate in the Search for Carbene-Stabilised Homoaromatics.

    PubMed

    Mattock, James D; Vargas, Alfredo; Dewhurst, Rian D

    2015-11-16

    The effect of carbenes as Lewis donor groups on the homoaromaticity of mono- and bicyclic organic molecules is surveyed. The search for viable carbene-stabilised homoaromatics resulted in a large amount of rejected candidates as well as nine promising candidates that are further analysed for their homoaromaticity by using a number of metrics. Of these, five appeared to show modest homoaromaticity, whereas another compound showed a level of homoaromaticity comparable with the homotropylium cation benchmark compound. Isoelectronic analogues and constitutional isomers of the lead compound were investigated, however, none of these showed comparable homoaromaticity. The implications of these calculations on the design of donor-stabilised homoaromatics are discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Vibration-displacement measurements with a highly stabilised optical fiber Michelson interferometer system

    NASA Astrophysics Data System (ADS)

    Xie, Fang; Ren, Junyu; Chen, Zhimin; Feng, Qibo

    2010-02-01

    A highly stabilised vibration-displacement measurement system, which employs fiber Bragg gratings (FBGs) to interleave two fiber Michelson interferometers that share the common-interferometric-optical path, is presented. The phase change in the interferometric signals of the two fiber Michelson interferometers have been tracked, respectively, with two electronic feedback loops. One of the fiber interferometers is used to stabilise the system by the use of an electronic feedback loop to compensate the environmental disturbances. The second fiber interferometer is used to perform the measurement task and employs another electronic feedback loop to track the phase change in the interferometric signal. The measurement system is able to measure vibration-displacement and provide the sense of direction of the displacement. The frequency range of the measured vibration-displacement is from 0.1 to 200 Hz and the measurement resolution is 10 nm.

  18. Green synthesis of highly concentrated aqueous colloidal solutions of large starch-stabilised silver nanoplatelets.

    PubMed

    Cheng, Fei; Betts, Jonathan W; Kelly, Stephen M; Hector, Andrew L

    2015-01-01

    A simple, environmentally friendly and cost-effective method has been developed to prepare a range of aqueous silver colloidal solutions, using ascorbic acid as a reducing agent, water-soluble starch as a combined crystallising, stabilising and solubilising agent, and water as the solvent. The diameter of silver nanoplatelets increases with higher concentrations of AgNO3 and starch. The silver nanoparticles are also more uniform in shape the greater the diameter of the nanoparticles. Colloidal solutions with a very high concentration of large, flat, hexagonal silver nanoplatelets (~230 nm in breadth) have been used to deposit and fix an antibacterial coating of these large starch-stabilised silver nanoplates on commercial cotton fibres, using a simple dip-coating process using water as the solvent, in order to study the dependence of the antibacterial properties of these nanoplatelets on their size.

  19. Finite-time boundedness and stabilisation of networked control systems with bounded packet dropout

    NASA Astrophysics Data System (ADS)

    Sun, Yeguo

    2014-09-01

    In this paper, the finite-time boundedness and stabilisation problems of a class of networked control systems (NCSs) with bounded packet dropout are investigated. The main results provided in the paper are sufficient conditions for finite-time boundedness and stability via state feedback. An iterative approach is proposed to model NCSs with bounded packet dropout as jump linear systems (JLSs). Based on Lyapunov stability theory and JLSs theory, the sufficient conditions for finite-time boundedness and stabilisation of the underlying systems are derived via linear matrix inequalities (LMIs) formulation. Moreover, both sensor-to-controller and controller-to-actuator packet dropouts are considered simultaneously. Lastly, an illustrative example is given to demonstrate the effectiveness of the proposed results.

  20. Preconditioning of Nonlinear Mixed Effects Models for Stabilisation of Variance-Covariance Matrix Computations.

    PubMed

    Aoki, Yasunori; Nordgren, Rikard; Hooker, Andrew C

    2016-03-01

    As the importance of pharmacometric analysis increases, more and more complex mathematical models are introduced and computational error resulting from computational instability starts to become a bottleneck in the analysis. We propose a preconditioning method for non-linear mixed effects models used in pharmacometric analyses to stabilise the computation of the variance-covariance matrix. Roughly speaking, the method reparameterises the model with a linear combination of the original model parameters so that the Hessian matrix of the likelihood of the reparameterised model becomes close to an identity matrix. This approach will reduce the influence of computational error, for example rounding error, to the final computational result. We present numerical experiments demonstrating that the stabilisation of the computation using the proposed method can recover failed variance-covariance matrix computations, and reveal non-identifiability of the model parameters.

  1. A sol-powder coating technique for fabrication of yttria stabilised zirconia

    SciTech Connect

    Wattanasiriwech, Darunee . E-mail: darunee@mfu.ac.th; Wattanasiriwech, Suthee; Stevens, Ron

    2006-08-10

    Yttria stabilised zirconia has been prepared using a simple sol-powder coating technique. The polymeric yttria sol, which was prepared using 1,3 propanediol as a network modifier, was homogeneously mixed with nanocrystalline zirconia powder and it showed a dual function: as a binder which promoted densification and a phase modifier which stabilised zirconia in the tetragonal and cubic phases. Thermal analysis and X-ray diffraction revealed that the polymeric yttria sol which decomposed at low temperature into yttrium oxide could change the m {sup {yields}} t phase transformation behaviour of the zirconia, possibly due to the small particle size and very high surface area of both yttria and zirconia particles allowing rapid alloying. The sintered samples exhibited three crystalline phases: monoclinic, tetragonal and cubic, in which cubic and tetragonal are the major phases. The weight fractions of the individual phases present in the selected specimens were determined using quantitative Rietveld analysis.

  2. Tropical deep convective cloud morphology

    NASA Astrophysics Data System (ADS)

    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

  3. Double interface formulation for improved α-tocopherol stabilisation in dehydration of emulsions.

    PubMed

    Zhou, Yankun; Roos, Yrjö H

    2013-08-30

    Encapsulation of hydrophobic nutrients can be achieved by freezing and freeze-drying of oil-in-water emulsions containing glass-forming materials. The addition of a polyelectrolyte layer on the protein-stabilised oil droplets may provide better protection to the oil phase against external stresses. Soy protein-trehalose and whey protein-trehalose emulsions with (layer-by-layer, LBL) and without (single-layer, SL) ι-carrageenan were used as the delivery systems for olive oil with dissolved α-tocopherol. Emulsions containing 0.125 g kg(-1) protein, 0.42 g kg(-1) oil and 150 g kg(-1) trehalose with (LBL) or without (SL) 0.25 g kg(-1) ι-carrageenan at pH 3 were frozen and freeze-dried and their state transitions were studied. The stability of α-tocopherol in freeze-dried systems at 0 and 0.33 water activity (aw ) during storage at 55 °C was followed. Loss of α-tocopherol was found in soy protein-stabilised SL systems at 0.33 aw , and this loss coincided with trehalose crystallisation. The stability of α-tocopherol was retained in soy protein-stabilised LBL and whey protein-stabilised LBL and SL systems at all conditions. Trehalose crystallisation-induced loss of structure was confirmed from changes in emulsion properties and visual appearance. Component sugar crystallisation contributed to the loss of sensitive compounds, but the stability of these compounds can be improved by the use of LBL formulations. © 2013 Society of Chemical Industry.

  4. Rapid analysis of polyolefin antioxidants and light stabilisers by supercritical fluid chromatography.

    PubMed

    Kithinji, J P; Bartle, K D; Raynor, M W; Clifford, A A

    1990-02-01

    Nineteen commercial antioxidants and light stabilisers, with a wide range of relative molecular masses and boiling-points, present in polyolefins were analysed by packed column supercritical fluid chromatography on four different phases with CO2 or 10% MeOH-CO2 as the mobile phase and with UV detection. The technique is shown to yield short analysis times and sufficient resolution for a number of additives present in a given polyolefin.

  5. Global output feedback stabilisation of high-order nonlinear systems with multiple time-varying delays

    NASA Astrophysics Data System (ADS)

    Gao, Fangzheng; Wu, Yuqiang; Yuan, Fushun

    2016-07-01

    This paper investigates the problem of global output feedback stabilisation for a class of high-order nonlinear systems with multiple time-varying delays. By using backstepping recursive technique and the homogeneous domination approach, a continuous output feedback controller is successfully designed, and the global asymptotic stability of the resulting closed-loop system is proven with the help of an appropriate Lyapunov- Krasovskii functional. Two simulation examples are given to illustrate the effectiveness of the proposed approach.

  6. The Stabilisation Potential of Individual and Mixed Assemblages of Natural Bacteria and Microalgae

    PubMed Central

    Lubarsky, Helen V.; Hubas, Cédric; Chocholek, Melanie; Larson, Fredrik; Manz, Werner; Paterson, David M.; Gerbersdorf, Sabine U.

    2010-01-01

    It is recognized that microorganisms inhabiting natural sediments significantly mediate the erosive response of the bed (“ecosystem engineers”) through the secretion of naturally adhesive organic material (EPS: extracellular polymeric substances). However, little is known about the individual engineering capability of the main biofilm components (heterotrophic bacteria and autotrophic microalgae) in terms of their individual contribution to the EPS pool and their relative functional contribution to substratum stabilisation. This paper investigates the engineering effects on a non-cohesive test bed as the surface was colonised by natural benthic assemblages (prokaryotic, eukaryotic and mixed cultures) of bacteria and microalgae. MagPI (Magnetic Particle Induction) and CSM (Cohesive Strength Meter) respectively determined the adhesive capacity and the cohesive strength of the culture surface. Stabilisation was significantly higher for the bacterial assemblages (up to a factor of 2) than for axenic microalgal assemblages. The EPS concentration and the EPS composition (carbohydrates and proteins) were both important in determining stabilisation. The peak of engineering effect was significantly greater in the mixed assemblage as compared to the bacterial (x 1.2) and axenic diatom (x 1.7) cultures. The possibility of synergistic effects between the bacterial and algal cultures in terms of stability was examined and rejected although the concentration of EPS did show a synergistic elevation in mixed culture. The rapid development and overall stabilisation potential of the various assemblages was impressive (x 7.5 and ×9.5, for MagPI and CSM, respectively, as compared to controls). We confirmed the important role of heterotrophic bacteria in “biostabilisation” and highlighted the interactions between autotrophic and heterotrophic biofilm consortia. This information contributes to the conceptual understanding of the microbial sediment engineering that represents an

  7. Finite-time state feedback stabilisation of stochastic high-order nonlinear feedforward systems

    NASA Astrophysics Data System (ADS)

    Xie, Xue-Jun; Zhang, Xing-Hui; Zhang, Kemei

    2016-07-01

    This paper studies the finite-time state feedback stabilisation of stochastic high-order nonlinear feedforward systems. Based on the stochastic Lyapunov theorem on finite-time stability, by using the homogeneous domination method, the adding one power integrator and sign function method, constructing a ? Lyapunov function and verifying the existence and uniqueness of solution, a continuous state feedback controller is designed to guarantee the closed-loop system finite-time stable in probability.

  8. Cooling and thermal stabilisation of Faraday rotators in the temperature range 300 — 200 K using Peltier elements

    NASA Astrophysics Data System (ADS)

    Palashov, O. V.; Ievlev, Ivan V.; Perevezentsev, E. A.; Katin, E. V.; Khazanov, Efim A.

    2011-09-01

    A new method for cooling and thermal stabilisation of Faraday rotators using Peltier elements is proposed and experimentally demonstrated. The scheme of thermal stabilisation of the magnetooptical elements ensures reliable operation of the device at the absorbed power ~2 W, which corresponds to the transmitted laser radiation power 1.5 kW. The results of the work make it possible to predict high efficiency of this method at the laser power of tens of kilowatts.

  9. Cold laser machining of nickel-yttrium stabilised zirconia cermets: Composition dependence

    SciTech Connect

    Sola, D.

    2009-09-15

    Cold laser micromachining efficiency in nickel-yttrium stabilised zirconia cermets was studied as a function of cermet composition. Nickel oxide-yttrium stabilised zirconia ceramic plates obtained via tape casting technique were machined using 8-25 ns pulses of a Nd: YAG laser at the fixed wavelength of 1.064 {mu}m and a frequency of 1 kHz. The morphology of the holes, etched volume, drill diameter, shape and depth were evaluated as a function of the processing parameters such as pulse irradiance and of the initial composition. The laser drilling mechanism was evaluated in terms of laser-material interaction parameters such as beam absorptivity, material spallation and the impact on the overall process discussed. By varying the nickel oxide content of the composite the optical absorption (-value is greatly modified and significantly affected the drilling efficiency of the green state ceramic substrates and the morphology of the holes. Higher depth values and improved drilled volume upto 0.2 mm{sup 3} per pulse were obtained for substrates with higher optical transparency (lower optical absorption value). In addition, a laser beam self-focussing effect is observed for the compositions with less nickel oxide content. Holes with average diameter from 60 {mu}m to 110 {mu}m and upto 1 mm in depth were drilled with a high rate of 40 ms per hole while the final microstructure of the cermet obtained by reduction of the nickel oxide-yttrium stabilised zirconia composites remained unchanged.

  10. Pavement thickness and stabilised foundation layer assessment using ground-coupled GPR

    NASA Astrophysics Data System (ADS)

    Hu, Jinhui; Vennapusa, Pavana K. R.; White, David J.; Beresnev, Igor

    2016-07-01

    Experimental results from field and laboratory investigations using a ground-coupled ground penetrating radar (GPR), dielectric measurement, magnetic imaging tomography (MIT) and dynamic cone penetrometer (DCP) tests are presented. Dielectric properties of asphalt pavement and stabilised and unstabilised pavement foundation materials were evaluated in the laboratory in frozen and unfrozen conditions. Laboratory test results showed that dielectric properties of materials back-calculated from GPR in comparison to dielectric gauge measurements are strongly correlated and repeatable. For chemically stabilised materials, curing time affected the dielectric properties of the materials. Field tests were conducted on asphalt pavement test sections with different foundation materials (stabilised and unstabilised layers), drainage conditions and layer thicknesses. GPR and MIT results were used to determine asphalt layer thicknesses and were compared with measured core thicknesses, while GPR and DCP were used to assess foundation layer profiles. Asphalt thicknesses estimated from GPR showed an average error of about 11% using the dielectric gauge values as input. The average error reduced to about 4% when calibrated with cores thicknesses. MIT results showed thicknesses that are about 9% higher than estimated using GPR. Foundation layer thicknesses could not be measured using GPR due to variations in moisture conditions between the test sections, which is partly attributed to variations in gradation and drainage characteristics of the subbase layer.

  11. Integrated waste management as a climate change stabilisation wedge for the Maltese islands.

    PubMed

    Falzon, Clyde; Fabri, Simon G; Frysinger, Steven

    2013-01-01

    The continuous increase in anthropogenic greenhouse gas emissions occurring since the Industrial Revolution is offering significant ecological challenges to Earth. These emissions are leading to climate changes which bring about extensive damage to communities, ecosystems and resources. The analysis in this article is focussed on the waste sector within the Maltese islands, which is the largest greenhouse gas emitter in the archipelago following the energy and transportation sectors. This work shows how integrated waste management, based on a life cycle assessment methodology, acts as an effective stabilisation wedge strategy for climate change. Ten different scenarios applicable to the Maltese municipal solid waste management sector are analysed. It is shown that the scenario that is most coherent with the stabilisation wedges strategy for the Maltese islands consists of 50% landfilling, 30% mechanical biological treatment and 20% recyclable waste export for recycling. It is calculated that 16.6 Mt less CO2-e gases would be emitted over 50 years by means of this integrated waste management stabilisation wedge when compared to the business-as-usual scenario. These scientific results provide evidence in support of policy development in Malta that is implemented through legislation, economic instruments and other applicable tools.

  12. High-performance electronic image stabilisation for shift and rotation correction

    NASA Astrophysics Data System (ADS)

    Parker, Steve C. J.; Hickman, D. L.; Wu, F.

    2014-06-01

    A novel low size, weight and power (SWaP) video stabiliser called HALO™ is presented that uses a SoC to combine the high processing bandwidth of an FPGA, with the signal processing flexibility of a CPU. An image based architecture is presented that can adapt the tiling of frames to cope with changing scene dynamics. A real-time implementation is then discussed that can generate several hundred optical flow vectors per video frame, to accurately calculate the unwanted rigid body translation and rotation of camera shake. The performance of the HALO™ stabiliser is comprehensively benchmarked against the respected Deshaker 3.0 off-line stabiliser plugin to VirtualDub. Eight different videos are used for benchmarking, simulating: battlefield, surveillance, security and low-level flight applications in both visible and IR wavebands. The results show that HALO™ rivals the performance of Deshaker within its operating envelope. Furthermore, HALO™ may be easily reconfigured to adapt to changing operating conditions or requirements; and can be used to host other video processing functionality like image distortion correction, fusion and contrast enhancement.

  13. The stabilisation and transportation of dissolved iron from high temperature hydrothermal vent systems

    NASA Astrophysics Data System (ADS)

    Hawkes, J. A.; Connelly, D. P.; Gledhill, M.; Achterberg, E. P.

    2013-08-01

    Iron (Fe) binding phases in two hydrothermal plumes in the Southern Ocean were studied using a novel voltammetric technique. This approach, reverse titration-competitive ligand exchange-adsorptive cathodic stripping voltammetry, showed that on average 30±21% of dissolved Fe in the hydrothermal plumes was stabilised by chemically labile binding to ligands. The conditional stability constant (log K‧FeL) of the observed complexes was 20.61±0.54 (mean±1 SD) for the two vent sites, intermediate between previous measurements of deep ocean ligands (21.4-23; Kondo et al., 2012) and dissolved weak estuarine ligands (<20; Gerringa et al., 2007). Our results indicate that approximately 7.5% of all hydrothermal Fe was stabilised by complexation with ligands. Furthermore, 47±26% of the dissolved Fe in the plume existed in the colloidal size range (0.02-0.2 μm). Our data suggests that a portion (∼7.5%) of hydrothermal Fe is sufficiently stabilised in the dissolved size fraction (<0.2 μm) to make an important impact on deep ocean Fe distributions. Lateral deep ocean currents transport this hydrothermal Fe as lenses of enhanced Fe concentrations away from mid ocean ridge spreading centres and back arc basins.

  14. The distribution and stabilisation of dissolved Fe in deep-sea hydrothermal plumes

    NASA Astrophysics Data System (ADS)

    Bennett, Sarah A.; Achterberg, Eric P.; Connelly, Douglas P.; Statham, Peter J.; Fones, Gary R.; German, Christopher R.

    2008-06-01

    We have conducted a study of hydrothermal plumes overlying the Mid-Atlantic Ridge near 5° S to investigate whether there is a significant export flux of dissolved Fe from hydrothermal venting to the oceans. Our study combined measurements of plume-height Fe concentrations from a series of 6 CTD stations together with studies of dissolved Fe speciation in a subset of those samples. At 2.5 km down plume from the nearest known vent site dissolved Fe concentrations were ˜ 20 nM. This is much higher than would be predicted from a combination of plume dilution and dissolved Fe(II) oxidation rates, but consistent with stabilisation due to the presence of organic Fe complexes and Fe colloids. Using Competitive Ligand Exchange-Cathodic Stripping Voltammetry (CLE-CSV), stabilised dissolved Fe complexes were detected within the dissolved Fe fraction on the edges of one non-buoyant hydrothermal plume with observed ligand concentrations high enough to account for stabilisation of ˜ 4% of the total Fe emitted from the 5° S vent sites. If these results were representative of all hydrothermal systems, submarine venting could provide 12-22% of the global deep-ocean dissolved Fe budget.

  15. Moduli stabilisation and de Sitter string vacua from magnetised D7 branes

    NASA Astrophysics Data System (ADS)

    Cremades, Daniel; Moral, Maria-Pilar García Del; Quevedo, Fernando; Suruliz, Kerim

    2007-05-01

    Anomalous U(1)'s are ubiquitous in 4D chiral string models. Their presence crucially affects the process of moduli stabilisation and cannot be neglected in realistic set-ups. Their net effect in the 4D effective action is to induce a matter field dependence in the non-perturbative superpotential and a Fayet-Iliopoulos D-term. We study flux compactifications of IIB string theory in the presence of magnetised D7 branes. These give rise to anomalous U(1)'s that modify the standard moduli stabilisation procedure. We consider simple orientifold models to determine the matter field spectrum and the form of the effective field theory. We apply our results to one-modulus KKLT and multi-moduli large volume scenarios, in particular to the Calabi-Yau Bbb P4[1,1,1,6,9]. After stabilising the matter fields, the effective action for the Kähler moduli can acquire an extra positive term that can be used for de Sitter lifting with non-vanishing F- and D-terms. This provides an explicit realization of the D-term lifting proposal of [1].

  16. Stabilisation and control design by partial output feedback and by partial interconnection

    NASA Astrophysics Data System (ADS)

    Blumthaler, Ingrid

    2012-11-01

    We study stabilisation and control design by partial output feedback on the one hand and by partial interconnection according to Willems on the other hand. This article is based on the paper Design, parametrization, and pole placement of stabilizing output feedback compensators via injective cogenerator quotient signal modules by I. Blumthaler and U. Oberst, and the same technique is used. Both discrete and continuous behaviours and various notions of stability are treated simultaneously. In the case of partial output feedback, we require that both the compensator and the feedback behaviour have proper transfer matrices without presuming properness of the plant. We obtain conditions ensuring the existence of such stabilising compensators which perform additional control tasks like, for instance, tracking, and an algorithm for constructing a large class of such compensators. In the case of stabilisation by interconnection no input-output structures of plant or compensator are assumed, but the controlled behaviour is endowed with a canonical input-output structure. Again we demand this input-output behaviour to have proper transfer matrix. For this situation we obtain necessary and sufficient conditions for the existence of compensators solving the given control task, and a constructive parametrisation of all of them.

  17. Stabilisation of Na,K-ATPase structure by the cardiotonic steroid ouabain

    SciTech Connect

    Miles, Andrew J.; Fedosova, Natalya U.; Hoffmann, Søren V.; Wallace, B.A.; Esmann, Mikael

    2013-05-31

    Highlights: •Ouabain binding to pig and shark Na,K-ATPase enhances thermal stability. •Ouabain stabilises both membrane-bound and solubilised Na,K-ATPase. •Synchrotron radiation circular dichroism is used for structure determination. •Secondary structure in general is not affected by ouabain binding. •Stabilisation is due to re-arrangement of tertiary structure. -- Abstract: Cardiotonic steroids such as ouabain bind with high affinity to the membrane-bound cation-transporting P-type Na,K-ATPase, leading to complete inhibition of the enzyme. Using synchrotron radiation circular dichroism spectroscopy we show that the enzyme-ouabain complex is less susceptible to thermal denaturation (unfolding) than the ouabain-free enzyme, and this protection is observed with Na,K-ATPase purified from pig kidney as well as from shark rectal glands. It is also shown that detergent-solubilised preparations of Na,K-ATPase are stabilised by ouabain, which could account for the successful crystallisation of Na,K-ATPase in the ouabain-bound form. The secondary structure is not significantly affected by the binding of ouabain. Ouabain appears however, to induce a reorganization of the tertiary structure towards a more compact protein structure which is less prone to unfolding; recent crystal structures of the two enzymes are consistent with this interpretation. These circular dichroism spectroscopic studies in solution therefore provide complementary information to that provided by crystallography.

  18. Role of phyto-stabilised silver nanoparticles in suppressing adjuvant induced arthritis in rats.

    PubMed

    Mani, Aparna; Vasanthi, C; Gopal, V; Chellathai, Darling

    2016-12-01

    The present study was aimed to evaluate the anti-arthritic effects of silver nanoparticles synthesised using Piper nigrum extract and to further establish its mechanism of action in a rat model of adjuvant induced arthritis (AA). Adjuvant arthritis was induced by injecting complete Freund's adjuvant (0.1mL) into the left hind paw of 36 albino Wistar rats (n=6). Silver nanoparticles stabilised with Piper nigrum extract (25 and 50mg/kg). Commercial silver nanoparticles (50mg/kg) and methotrexate (0.1mg/kg) were administered by intraperitoneal route from day 11 to day 22 on alternate days. It was found that treatment with silver nanoparticles stabilised with Piper nigrum (S-AgNPs) significantly reduced the paw edema and alleviated the histopathological changes of cell infiltration, synovial hyperplasia, bone and cartilage destruction. Furthermore, the phytostabilised silver nanoparticles (S-AgNPs) inhibited the protein expression of NF-kβ p65 and TNF-α as evidenced by immunohistochemistry analysis. Our current findings suggest that silver nanoparticles stabilised with Piper nigrum extract (S-AgNPs) have potent anti-arthritic activity which is mediated by inhibition of TNF-α and suppression of pro-inflammatory cytokines that are secreted in response to activated transcription factors of NF-kβ. Copyright © 2016 Elsevier B.V. All rights reserved.

  19. Leachability and heavy metal speciation of 17-year old stabilised/solidified contaminated site soils.

    PubMed

    Wang, Fei; Wang, Hailing; Al-Tabbaa, Abir

    2014-08-15

    The long-term leachability, heavy metal speciation transformation and binding mechanisms in a field stabilised/solidified contaminated soil (made ground) from West Drayton site were recently investigated following in situ auger mixing treatment with a number of cement-based binders back in 1996. Two batch leaching tests (TCLP and BS EN 12457) and a modified five step sequential extraction procedure along with X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were employed for the testing of the 17-year-old field soil. The results of batch leaching tests show that the treatment employed remained effective at 17 years of service time, with all BS EN 12457 test samples and most of TCLP test samples satisfied drinking water standards. Sequential extraction results illustrate that the leaching of Cu, Ni, Zn, Pb and Cd in all mixes mainly occurred at the Fe/Mn phase, ranging from 43% to 83%. Amongst the five metals tested, Ni was the most stable with around 40% remained in the residual phase for all the different cement-based binder stabilised/solidified samples. XRD and SEM analyses show that the hydration process has been fully completed and further carbonation took place. In summary, this study confirms that such cement-based stabilisation/solidification (S/S) treatment can achieve satisfactory durability and thus is a reliable technique for long-term remediation of heavy metal contaminated soil. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. Stabilisation of silver and copper nanoparticles in a chemically modified chitosan matrix.

    PubMed

    Tiwari, Anand D; Mishra, Ajay K; Mishra, Shivani B; Kuvarega, Alex T; Mamba, Bhekie B

    2013-02-15

    This work describes the stabilisation of silver and copper nanoparticles in chemically modified chitosan colloidal solution. Chitosan-N-2-methylidene-hydroxy-pyridine-6-methylidene hydroxy thiocarbohydrazide (CSPTH) was used as a stabilising and reducing agent for silver and copper nanoparticles. The modified chitosan derivatives and the synthesised nanoparticles were characterised by Fourier transform infrared (FT-IR) spectroscopy, Ultraviolet-visible (UV-Vis) spectroscopy and X-ray diffraction (XRD). Particle size, morphology and segregation of the nanoparticles were determined by transmission electron microscopy (TEM). The size of the nanoparticles was found to be less than 20 nm and 50 nm for silver and copper nanoparticles, respectively. These nanoparticles were stabilised in a chemically modified chitosan solution and their properties were studied using fluorescence spectroscopy, photoluminescence spectroscopy and surface-enhanced Raman scattering (SERS). The optical properties of silver nanoparticles in surface plasmon band (SPB) were enhanced at 407 nm compared to those of copper nanoparticles. Fluorescence (400 nm and 756 nm), photoluminescence (450 and 504 nm) and Raman scattering (1382 and 1581 cm(-1)) properties for the copper nanoparticles were superior to those of the silver nanoparticles.

  1. Avalanches of coalescence events and local extensional flows--stabilisation or destabilisation due to surfactant.

    PubMed

    Gunes, Deniz Z; Clain, Xavier; Breton, Olivier; Mayor, Guy; Burbidge, Adam S

    2010-03-01

    From two-drop collision experiments, it is known that local extensional flow favors coalescence. Recently, Bremond et al. used microfluidic methods to evidence this point. Similarly, we used specific microfluidic geometries to impose sudden extensional flow, following drop collision under controlled conditions, and coalescence events were recorded with a high-speed camera. In this study we focus on the effect of surfactant on the coalescence, or stabilisation against it, between drops flowing apart due to either imposed external flow or capillary forces related to drop shape relaxation. Coalescence can be induced even when drops are initially separated by an intersticial lubricating film by far thicker than the critical thickness for rupturing under the action of Van der Waals forces. This is particularly relevant to avalanches of coalescence events, in flowing or even quiescent emulsions or foams. When non-ionic surfactant was used, it was observed that small concentrations apparently enhance coalescence in extension. But at higher concentrations it provides stabilisation through a specific mechanism of thread formation and rupture; the stabilisation mechanism can be complex.

  2. Nitrogen removal in a two-stage, re-circulating waste stabilisation pond system.

    PubMed

    Baskaran, K; Farago, L

    2007-01-01

    Waste stabilisation ponds are used widely in Australia and other parts of the world for treating wastewater from domestic and a wide range of industrial sources. It remains a popular form of treatment for wastewater for many small rural towns. The development of a two-stage, re-circulating waste stabilisation pond incorporating algal-bacterial biofilm represents a new approach to increasing the functioning biomass within the water column to improve treatment efficiency. This new approach will be a more viable and economical option for most of the existing waste stabilisation ponds to achieve significant nitrogen removal than converting them to another form of biological nutrient removal processes. A laboratory-scale, two-stage, re-circulating system incorporating "Bio-Tube" plastic modules as attached growth medium has been tested using synthetic wastewater. It has been proven that nitrification-denitrification was the primary mechanism for nitrogen removal in such a system operated under complete mix conditions. During the experimental period, average removal efficiencies of 90-95% of ammonia nitrogen and 65-85% of total nitrogen removal were achieved with influent COD of 600 mg/L and total nitrogen of 70 mg/L.

  3. Correlation between inter-vertebral disc morphology and the results in patients undergoing Graf ligament stabilisation.

    PubMed

    Askar, Zahid; Wardlaw, Douglas; Muthukumar, Thillainayagamike; Smith, Frank; Kader, Deiary; Gibson, Suzy

    2004-12-01

    Previous studies have shown Graf ligament stabilisation procedure to give mixed results in the short to medium term. The aim of this study was to correlate the pre-operative state of the disc, multifidus muscles, age of the patient, levels operated and the clinical outcome after a mean follow-up of 47 months. Graf ligament stabilisation procedure was carried out in 38 patients between 1996 and 1999. Their post-operative status was assessed using MacNab criteria. The post-operative follow-up was by postal questionnaires and review of the clinical notes. Disc morphology and multifidus muscle wasting was graded blindly and independently. The intra- and interobserver reliability was measured with kappa score and classified using the kappa classification of Landis and Koch. Correlation was measured with the help of Spearman correlation coefficient. Thirty-eight patients (100%) returned the questionnaires. Mean follow-up time was 47.55 months. Fifty-nine levels were operated on. Mean age was 39.68 years. The overall re-operation rate was 15.8%. The intra- and interobserver reliability was graded as good to substantial. Twenty-two patients (57.89%) were satisfied with the procedure. There was no statistically significant correlation between disc morphology, multifidus muscle wasting, sex, age, number of levels operated, the levels operated, and the satisfaction rate. The indications of Graf ligament stabilisation procedure are not clear. Further work is necessary to clearly identify the indication for the procedure.

  4. Global stabilisation of a class of generalised cascaded systems by homogeneous method

    NASA Astrophysics Data System (ADS)

    Ding, Shihong; Zheng, Wei Xing

    2016-04-01

    This paper considers the problem of global stabilisation of a class of generalised cascaded systems. By using the extended adding a power integrator technique, a global controller is first constructed for the driving subsystem. Then based on the homogeneous properties and polynomial assumption, it is shown that the stabilisation of the driving subsystem implies the stabilisation of the overall cascaded system. Meanwhile, by properly choosing some control parameters, the global finite-time stability of the closed-loop cascaded system is also established. The proposed control method has several new features. First, the nonlinear cascaded systems considered in the paper are more general than the conventional ones, since the powers in the nominal part of the driving subsystem are not required to be restricted to ratios of positive odd numbers. Second, the proposed method has some flexible parameters which provide the possibility for designing continuously differentiable controllers for cascaded systems, while the existing designed controllers for such kind of cascaded systems are only continuous. Third, the homogenous and polynomial conditions adopted for the driven subsystem are easier to verify when compared with the matching conditions that are widely used previously. Furthermore, the efficiency of the proposed control method is validated by its application to finite-time tracking control of non-holonomic wheeled mobile robot.

  5. Topical antihistamines and mast cell stabilisers for treating seasonal and perennial allergic conjunctivitis.

    PubMed

    Castillo, Mayret; Scott, Neil W; Mustafa, Mohammad Z; Mustafa, Mohammed S; Azuara-Blanco, Augusto

    2015-06-01

    Seasonal/perennial allergic conjunctivitis is the most common allergic conjunctivitis, usually with acute manifestations when a person is exposed to allergens and with typical signs and symptoms including itching, redness, and tearing. The clinical signs and symptoms of allergic conjunctivitis are mediated by the release of histamine by mast cells. Histamine antagonists (also called antihistamines) inhibit the action of histamine by blocking histamine H1 receptors, antagonising the vasoconstrictor, and to a lesser extent, the vasodilator effects of histamine. Mast cell stabilisers inhibit degranulation and consequently the release of histamine by interrupting the normal chain of intracellular signals. Topical treatments include eye drops with antihistamines, mast cell stabilisers, non-steroidal anti-inflammatory drugs, combinations of the previous treatments, and corticosteroids. Standard treatment is based on topical antihistamines alone or topical mast cell stabilisers alone or a combination of treatments. There is clinical uncertainty about the relative efficacy and safety of topical treatment. The objective of this review was to assess the effects of topical antihistamines and mast cell stabilisers, alone or in combination, for use in treating seasonal and perennial allergic conjunctivitis. We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2014, Issue 7), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to July 2014), EMBASE (January 1980 to July 2014), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 17 July 2014. We also searched the

  6. Interfacial behaviour of sodium stearoyllactylate (SSL) as an oil-in-water pickering emulsion stabiliser.

    PubMed

    Kurukji, D; Pichot, R; Spyropoulos, F; Norton, I T

    2013-11-01

    The ability of a food ingredient, sodium stearoyllactylate (SSL), to stabilise oil-in-water (O/W) emulsions against coalescence was investigated, and closely linked to its capacity to act as a Pickering stabiliser. Results showed that emulsion stability could be achieved with a relatively low SSL concentration (≥0.1 wt%), and cryogenic-scanning electron microscopy (cryo-SEM) visualisation of emulsion structure revealed the presence of colloidal SSL aggregates adsorbed at the oil-water interface. Surface properties of SSL could be modified by altering the size of these aggregates in water; a faster decrease in surface tension was observed when SSL dispersions were subjected to high pressure homogenisation (HPH). The rate of SSL adsorption at the sunflower oil-water interface also increased after HPH, and a higher interfacial tension (IFT) was observed with increasing SSL concentration. Differential scanning calorimetry (DSC) enabled a comparison of the thermal behaviour of SSL in aqueous dispersions with SSL-stabilised O/W emulsions. SSL melting enthalpy depended on emulsion interfacial area and the corresponding DSC data was used to determine the amount of SSL adsorbed at the oil-water interface. An idealised theoretical interfacial coverage calculation based on Pickering emulsion theory was in general agreement with the mass of SSL adsorbed as predicted by DSC. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

  7. Emulsions stabilised by food colloid particles: role of particle adsorption and wettability at the liquid interface.

    PubMed

    Paunov, Vesselin N; Cayre, Olivier J; Noble, Paul F; Stoyanov, Simeon D; Velikov, Krassimir P; Golding, Matt

    2007-08-15

    We study the effect of the particle wettability on the preferred type of emulsion stabilised solely by food colloid particles. We present results obtained with the recently developed gel trapping technique (GTT) for characterisation of wettability and surface structuring of individual food colloid particles adsorbed at air-water and oil-water interfaces. This method allows us to replicate a particle monolayer onto the surface of polydimethylsiloxane (PDMS) without altering the position of the particles. By observing the polymer surface with scanning electron microscopy (SEM), we are able to determine the contact angle of the individual particles at the initial liquid interface. We demonstrate that the GTT can be applied to fat crystal particles, calcium carbonate particles coated with stearic acid and spray-dried soy protein/calcium phosphate particles at air-water and oil-water interfaces. Subsequently, we prepare emulsions of decane and water stabilised by the same food colloid particles and correlate the wettability data obtained for these particles to the preferred type of emulsions they stabilise.

  8. Dynamos in rotating compressible convection

    NASA Astrophysics Data System (ADS)

    Favier, B.; Bushby, P. J.

    2011-12-01

    Motivated by open questions in fundamental dynamo theory, the overall aim of this paper is to investigate some of the properties of dynamo action in rotating compressible convection. We study dynamo action in a convective layer of electrically-conducting, compressible fluid, rotating about the vertical axis. In order to identify the effects of rotation, we also carry out an equivalent set of calculations of convectively-driven dynamo action in a non-rotating layer. Whether or not the layer is rotating, the convection acts as a small-scale dynamo provided that the magnetic diffusivity is small enough. Defining the magnetic Reynolds number in terms of the horizontal scales of motion, we find that rotation reduces the critical value of this parameter above which dynamo action is observed. In the nonlinear regime, a rotating dynamo calculation and a separate non-rotating simulation are found to saturate at a similar level, even though the mid-layer value of the local magnetic Reynolds number is smaller in the rotating case. We compute the Lyapunov exponents of the flow to show that the stretching properties of the convection are modified by rotation. Furthermore, rotation significantly reduces the magnetic energy dissipation in the lower part of the layer.

  9. Mantle convection on modern supercomputers

    NASA Astrophysics Data System (ADS)

    Weismüller, Jens; Gmeiner, Björn; Mohr, Marcus; Waluga, Christian; Wohlmuth, Barbara; Rüde, Ulrich; Bunge, Hans-Peter

    2015-04-01

    Mantle convection is the cause for plate tectonics, the formation of mountains and oceans, and the main driving mechanism behind earthquakes. The convection process is modeled by a system of partial differential equations describing the conservation of mass, momentum and energy. Characteristic to mantle flow is the vast disparity of length scales from global to microscopic, turning mantle convection simulations into a challenging application for high-performance computing. As system size and technical complexity of the simulations continue to increase, design and implementation of simulation models for next generation large-scale architectures demand an interdisciplinary co-design. Here we report about recent advances of the TERRA-NEO project, which is part of the high visibility SPPEXA program, and a joint effort of four research groups in computer sciences, mathematics and geophysical application under the leadership of FAU Erlangen. TERRA-NEO develops algorithms for future HPC infrastructures, focusing on high computational efficiency and resilience in next generation mantle convection models. We present software that can resolve the Earth's mantle with up to 1012 grid points and scales efficiently to massively parallel hardware with more than 50,000 processors. We use our simulations to explore the dynamic regime of mantle convection assessing the impact of small scale processes on global mantle flow.

  10. Mantle Convection on Modern Supercomputers

    NASA Astrophysics Data System (ADS)

    Weismüller, J.; Gmeiner, B.; Huber, M.; John, L.; Mohr, M.; Rüde, U.; Wohlmuth, B.; Bunge, H. P.

    2015-12-01

    Mantle convection is the cause for plate tectonics, the formation of mountains and oceans, and the main driving mechanism behind earthquakes. The convection process is modeled by a system of partial differential equations describing the conservation of mass, momentum and energy. Characteristic to mantle flow is the vast disparity of length scales from global to microscopic, turning mantle convection simulations into a challenging application for high-performance computing. As system size and technical complexity of the simulations continue to increase, design and implementation of simulation models for next generation large-scale architectures is handled successfully only in an interdisciplinary context. A new priority program - named SPPEXA - by the German Research Foundation (DFG) addresses this issue, and brings together computer scientists, mathematicians and application scientists around grand challenges in HPC. Here we report from the TERRA-NEO project, which is part of the high visibility SPPEXA program, and a joint effort of four research groups. TERRA-NEO develops algorithms for future HPC infrastructures, focusing on high computational efficiency and resilience in next generation mantle convection models. We present software that can resolve the Earth's mantle with up to 1012 grid points and scales efficiently to massively parallel hardware with more than 50,000 processors. We use our simulations to explore the dynamic regime of mantle convection and assess the impact of small scale processes on global mantle flow.

  11. Influence of convection on microstructure

    NASA Technical Reports Server (NTRS)

    Wilcox, William R.; Eisa, Gaber Faheem; Chandrasekhar, S.; Larrousse, Mark; Banan, Mohsen

    1988-01-01

    The influence was studied of convection during directional solidification on the resulting microstructure of eutectics, specifically lead/tin and manganese/bismuth. A theory was developed for the influence of convection on the microstructure of lamellar and fibrous eutectics, through the effect of convection on the concentration field in the melt in front of the growing eutectic. While the theory agrees with the experimental spin-up spin-down results, it predicts that the weak convection expected due to buoyancy will not produce a measurable change in eutectic microstructure. Thus, this theory does not explain the two fold decrease in MnBi fiber size and spacing observed when MnBi-Bi is solidified in space or on Earth with a magnetic field applied. Attention was turned to the morphology of the MnBi-Bi interface and to the generation of freezing rate fluctuations by convection. Decanting the melt during solidification of MnBi-Bi eutectic showed that the MnBi phase projects into the melt ahead of the Bi matrix. Temperature measurements in a Bi melt in the vertical Bridgman-Stockbarger configuration showed temperature variations of up to 25 C. Conclusions are drawn and discussed.

  12. Effects of electron beam irradiation on the property behaviour of poly(ether-block-amide) blended with various stabilisers

    NASA Astrophysics Data System (ADS)

    Murray, Kieran A.; Kennedy, James E.; Barron, Valerie; McEvoy, Brian; Vrain, Olivier; Ryan, Damien; Cowman, Richard; Higginbotham, Clement L.

    2015-05-01

    Radiosterilisation can induce modifications and/or degradation to transpire in poly(ether-block-amide) (PEBA) following irradiation. The current investigation utilises combined synergistic mixtures of stabilisers to minimise these effects, by melt blending them with the PEBA material. Hindered amine stabilisers (HAS), primary antioxidants and secondary antioxidants were the stabilisers incorporate to reduce/eliminate the effects of 50 kGy electron beam irradiation dose on the material. Results were discussed by comparing the stabilising efficiency of mixtures on the PEBA material in contrast to the control sample. Dynamic frequency sweeps demonstrated the formation of crosslinks, where the degree of crosslinking was dependent on the combination of stabilisers mixed in the base material (PEBA). The storage modulus displayed that PEBA blended with Irganox 565 had very slight changes in contrast to all other samples following irradiation. However, since this sample is a phenol containing system, severe discolouration was observed in comparison to other samples due to the oxidation of the hindered phenol. Overall, this study provides compelling evidence that a combined synergistic mixture of Irganox 565 (multifunctional phenolic antioxidant) and Tinuvin 783 (hindered amide light stabiliser) with PEBA, resulted in the best radiation stability.

  13. A comparative study for the stabilisation of heavy metal contaminated sediment by limestone, MnO2 and natural zeolite.

    PubMed

    Yi, Yuanjie; Wen, Jia; Zeng, Guangming; Zhang, Taotao; Huang, Fenghu; Qin, Haiyan; Tian, Shiyu

    2017-01-01

    Three amendments including limestone, MnO2 and natural zeolite were assessed for their stabilisation effects on Zn, Cu, Pb and Cd in sediment of east Dongting Lake, mid-south China. The metals were first subject to pollution status and potential ecological risk assessment to identify the current and potential hazards to ecology. Speciation of the metals in the sediment treated with amendments was then carried out by BCR sequential extraction procedure in order to evaluate metal contents and their potential mobility. The total concentrations of Zn, Cu, Pb and Cd in the east Dongting Lake were all above the means of national stream sediment and soil guidelines. The sediments were currently unpolluted to moderately pollute with Zn, Cu and Pb and strongly polluted with Cd. Zinc, Cu and Pb posed low risks to the lake ecosystem, and Cd had the highest potential risk that caused the overall risk of the sediment to be high or very high. Limestone stabilised Cu and Zn effectively, yet mobilisation of Cd and Pb by such amendment was also observed. MnO2 effectively reduced the extractable Cd and Pb. The effect of natural zeolite on metal stabilisation in the sediment was least notable. Limestone and MnO2 showed higher metal stabilisation efficiencies than zeolite. However, a single amendment is unable to achieve the goal of stabilisation for all metals. A combination use of the advantageous amendments or a search of a stronger stabiliser should be the interest of our future study.

  14. Polycarboxylate ethers: The key towards non-toxic TiO2 nanoparticle stabilisation in physiological solutions.

    PubMed

    Koch, S; Kessler, M; Mandel, K; Dembski, S; Heuzé, K; Hackenberg, S

    2016-07-01

    Stable, non-agglomerated TiO2 nanoparticle (NP) dispersions are a crucial requirement for an accurate NP dosing in in vitro and in vivo experiments. In this study self-synthesised TiO2 NPs were stabilised in three different cell culture media (DMEM, RPMI, BEGM) with the help of stabilising agents. Cell culture tested stabilisers (bovine serum albumin, fetal bovine serum) were compared to non-tested commercial products which are commonly utilized in the cement industry (Melflux(®) 4930 F, Melpers(®) 4343, Sika(®) ViscoCrete(®)-10110178). For a quantitative evaluation and comparison of the degree of stabilisation, a sedimentation study using UV absorbance spectroscopy was carried out and the agglomerate size was measured via dynamic light scattering. The cytotoxicity of the novel surfactants and stabilised NPs was examined in a head and neck squamous cell carcinoma-derived FaDu cell line and in human mesenchymal stem cells. We successfully stabilised TiO2 NPs with Melflux(®) 4930 F in each cell culture medium, achieving perfect stability over at least one day and agglomerate sizes of less than 100nm, while the cytotoxicity of the NPs was not affected. Copyright © 2016. Published by Elsevier B.V.

  15. Evolution of Soil Moisture-Convection Interactions against the Backdrop of Global Oscillations

    NASA Astrophysics Data System (ADS)

    Tawfik, A. B.; Dirmeyer, P.

    2014-12-01

    Interannual changes in how soil moisture can trigger convection are explored within the context of known global-scale oscillations, such as ENSO. Because soil moisture-convection interactions are a local phenomenon that require a sufficiently moist and unstable atmosphere to initiate convection, any systematic changes to water vapor produced by these global circulation changes may manifest in disrupting or promoting the soil moisture-precipitation feedback chain. Using a new framework, the Heated Condensation Framework (HCF; Tawfik and Dirmeyer 2014), local land-atmosphere coupling can be examined by separating the atmospheric background state from the land surface state in terms of convective initiation. The current work explores how the soil moisture-convection relationship changes from year-to-year and during influential El Nino and La Nina events. This is done using several global and regional reanalysis products, as well as observations where available.

  16. Internal Wave Generation by Convection

    NASA Astrophysics Data System (ADS)

    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

  17. Steady dissolution rate due to convective mixing in anisotropic porous media

    NASA Astrophysics Data System (ADS)

    Green, Christopher P.; Ennis-King, Jonathan

    2014-11-01

    Enhanced dissolution of CO2 into a saline aquifer due to convective mixing is an important physical process for the secure long-term storage of significant quantities of CO2. Numerical simulations have previously shown that the dissolution rate of CO2 into reservoir brine will stabilise after a certain time period, with only small oscillations about a long-term average. A theoretical estimate for this average long-term mass flux in an isotropic homogeneous reservoir has previously appeared in the literature. In this paper, an estimate for the steady dissolution rate in anisotropic homogenous porous media is developed using a simple theoretical argument. Detailed numerical simulations confirm that the steady dissolution rate scales as (kvkh) 1 / 2 in an anisotropic homogeneous porous media, where kv and kh are the vertical and horizontal permeabilities, respectively. The scaling is also shown to be appropriate for heterogeneous models where vertical heterogeneity is introduced by including a random distribution of impermeable barriers.

  18. ARM - Midlatitude Continental Convective Clouds

    DOE Data Explorer

    Jensen, Mike; Bartholomew, Mary Jane; Genio, Anthony Del; Giangrande, Scott; Kollias, Pavlos

    2012-01-19

    Convective processes play a critical role in the Earth's energy balance through the redistribution of heat and moisture in the atmosphere and their link to the hydrological cycle. Accurate representation of convective processes in numerical models is vital towards improving current and future simulations of Earths climate system. Despite improvements in computing power, current operational weather and global climate models are unable to resolve the natural temporal and spatial scales important to convective processes and therefore must turn to parameterization schemes to represent these processes. In turn, parameterization schemes in cloud-resolving models need to be evaluated for their generality and application to a variety of atmospheric conditions. Data from field campaigns with appropriate forcing descriptors have been traditionally used by modelers for evaluating and improving parameterization schemes.

  19. Modal equations for cellular convection

    NASA Technical Reports Server (NTRS)

    Gough, D. O.; Spiegel, E. A.; Toomre, J.

    1975-01-01

    We expand the fluctuating flow variables of Boussinesq convection in the planform functions of linear theory. Our proposal is to consider a drastic truncation of this expansion as a possible useful approximation scheme for studying cellular convection. With just one term included, we obtain a fairly simple set of equations which reproduces some of the qualitative properties of cellular convection and whose steady-state form has already been derived by Roberts (1966). This set of 'modal equations' is analyzed at slightly supercritical and at very high Rayleigh numbers. In the latter regime the Nusselt number varies with Rayleigh number just as in the mean-field approximation with one horizontal scale when the boundaries are rigid. However, the Nusselt number now depends also on the Prandtl number in a way that seems compatible with experiment. The chief difficulty with the approach is the absence of a deductive scheme for deciding which planforms should be retained in the truncated expansion.

  20. The Role of the Velocity Gradient in Laminar Convective Heat Transfer through a Tube with a Uniform Wall Heat Flux

    ERIC Educational Resources Information Center

    Wang, Liang-Bi; Zhang, Qiang; Li, Xiao-Xia

    2009-01-01

    This paper aims to contribute to a better understanding of convective heat transfer. For this purpose, the reason why thermal diffusivity should be placed before the Laplacian operator of the heat flux, and the role of the velocity gradient in convective heat transfer are analysed. The background to these analyses is that, when the energy…

  1. The Role of the Velocity Gradient in Laminar Convective Heat Transfer through a Tube with a Uniform Wall Heat Flux

    ERIC Educational Resources Information Center

    Wang, Liang-Bi; Zhang, Qiang; Li, Xiao-Xia

    2009-01-01

    This paper aims to contribute to a better understanding of convective heat transfer. For this purpose, the reason why thermal diffusivity should be placed before the Laplacian operator of the heat flux, and the role of the velocity gradient in convective heat transfer are analysed. The background to these analyses is that, when the energy…

  2. Effectiveness of arthroscopic versus open surgical stabilisation for the management of traumatic anterior glenohumeral instability.

    PubMed

    Ng, Choong; Bialocerkowski, Andrea; Hinman, Rana

    2007-06-01

    Background  Anterior instability is a frequent complication following a traumatic glenohumeral dislocation. Frequently the underlying pathology associated with recurrent instability is a Bankart lesion. Surgical correction of Bankart lesions and other associated pathology is the key to successful treatment. Open surgical glenohumeral stabilisation has been advocated as the gold standard because of consistently low postoperative recurrent instability rates. However, arthroscopic glenohumeral stabilisation could challenge open surgical repair as the gold standard treatment for traumatic anterior glenohumeral instability. Objectives  Primary evidence that compared the effectiveness of arthroscopic versus open surgical glenohumeral stabilisation was systematically collated regarding best-practice management for adults with traumatic anterior glenohumeral instability. Search strategy  A systematic search was performed using 14 databases: MEDLINE, Cumulative Index of Nursing and Allied Health (CINAHL), Allied and Complementary Medicine Database (AMED), ISI Web of Science, Expanded Academic ASAP, Proquest Medical Library, Evidence Based Medicine Reviews, Physiotherapy Evidence Database, TRIP Database, PubMed, ISI Current Contents Connect, Proquest Digital Dissertations, Open Archives Initiative Search Engine, Australian Digital Thesis Program. Studies published between January 1984 and December 2004 were included in this review. No language restrictions were applied. Selection criteria  Eligible studies were those that compared the effectiveness of arthroscopic versus open surgical stabilisation for the management of traumatic anterior glenohumeral instability, which had more than 2 years of follow up and used recurrent instability and a functional shoulder questionnaire as primary outcomes. Studies that used non-anatomical open repair techniques, patient groups that were specifically 40 years or older, or had multidirectional instability or other concomitant

  3. Coherent structures in compressible convection

    NASA Astrophysics Data System (ADS)

    Xie, Xin

    An issue of some debate in numerical simulations of compressible convection is concerned with whether the flows break up into multiple cells in the vertical, or whether coherent flow structures exist which span much of the depth range. We have carried out a series of two-dimensional simulations to determine whether vertically coherent flow patterns found in some of the earlier studies persist as the convective motions are required to carry an ever greater fraction of the total energy flux upward (in the limit of very 'efficient' convection), or when the density contrast across the convective layer is high (factor of approximately 100), or when an eddy viscosity is employed instead of a constant dynamic viscosity. Such circumstances were thought by some to be responsible for the compressible convection breaking up into multiple cells, in a manner favored by mixing-length models. In all the cases that we have studied, the convection consists of flows coherent over the entire depth of the computational domain, with no tendency to form a series of cells in the vertical, contrary to the basic assumption of mixing-length approaches. The convective flows are often supersonic near the upper boundary. In some cases fluttering shocks form on the sides of the downflows, and significant modulation of the enthalpy and kinetic fluxes by vertical acoustic pulsations is observed. It appears that sufficient thermal diffusion and a high density contrast create a situation that favors the formation of supersonic regions near the upper boundary. Yet substantial thermal diffusion may also broaden the shocks into smooth transition regions, and large pressure fluctuations found near the top of downflows serve to decelerate the fast horizontal flows. Pressure fluctuations often can result in positive density fluctuations and thus cause buoyancy braking throughout the upflows, even though the fluid there is warmer than its surroundings. Since vigorous (and often supersonic) motions were

  4. Wavenumber selection in Benard convection

    SciTech Connect

    Catton, I.

    1988-11-01

    The results of three related studies dealing with wavenumber selection in Rayleigh--Benard convection are reported. The first, an extension of the power integral method, is used to argue for the existence of multi-wavenumbers at all supercritical wavenumbers. Most existing closure schemes are shown to be inadequate. A thermodynamic stability criterion is shown to give reasonable results but requires empirical measurement of one parameter for closure. The third study uses an asymptotic approach based in part on geometric considerations and requires no empiricism to obtain good predictions of the wavenumber. These predictions, however, can only be used for certain planforms of convection.

  5. Mesoscale aspects of convective storms

    NASA Technical Reports Server (NTRS)

    Fujita, T. T.

    1981-01-01

    The structure, evolution and mechanisms of mesoscale convective disturbances are reviewed and observation techniques for "nowcasting" their nature are discussed. A generalized mesometeorological scale is given, classifying both low and high pressure systems. Mesoscale storms are shown often to induce strong winds, but their wind speeds are significantly less than those accompanied by submesoscale disturbances, such as tornadoes, downbursts, and microbursts. Mesoscale convective complexes, severe storm wakes, and flash floods are considered. The understanding of the evolution of supercells is essential for improving nowcasting capabilities and a very accurate combination of radar and satellite measurements is required.

  6. Convection induced by radiative cooling of a layer of participating medium

    SciTech Connect

    Prasanna, Swaminathan; Venkateshan, S. P.

    2014-05-15

    Simulations and experiments have been conducted to study the effect of radiative cooling on natural convection in a horizontal layer of a participating medium enclosed between isothermal opaque wall and radiatively transparent wall and exposed to a cold background. The study is of relevance to a nocturnal boundary layer under clear and calm conditions. The focus of the study is to capture the onset of convection caused by radiative cooling. The experiments have been designed to mimic the atmospheric radiative boundary conditions, and hence decoupling convection and radiation boundary conditions. Planck number Pl and optical thickness of the layer τ{sub H} are the two important parameters that govern the interaction between radiation and convection. The radiation-convection coupling is a strong function of length scale. Convection sets up within first few seconds for all the experiments. Strong plume like convection is observed for the experimental conditions used in the present study. Both simulations and experiments confirm that radiative cooling increases substantially with decrease in emissivity of the bottom wall. Radiative cooling is strongly influenced by the nongray nature of the participating medium, especially when strong emission from the medium escapes to space, in the window region of the atmosphere. Accurate representation of radiative properties is critical. Linear stability analysis of onset of convection indicates that radiation stabilizes convection as Pl decreases. The observations are similar to the case of Rayleigh Bénard convection in a radiating gas. However, for both experimental and numerical conditions, the observed Rayleigh numbers are much greater than the critical Rayleigh number. To conclude, the role of radiation is to drive and sustain convection in the unstable layer.

  7. Convective Overshoot in Stellar Interior

    NASA Astrophysics Data System (ADS)

    Zhang, Q. S.

    2015-07-01

    In stellar interiors, the turbulent thermal convection transports matters and energy, and dominates the structure and evolution of stars. The convective overshoot, which results from the non-local convective transport from the convection zone to the radiative zone, is one of the most uncertain and difficult factors in stellar physics at present. The classical method for studying the convective overshoot is the non-local mixing-length theory (NMLT). However, the NMLT bases on phenomenological assumptions, and leads to contradictions, thus the NMLT was criticized in literature. At present, the helioseismic studies have shown that the NMLT cannot satisfy the helioseismic requirements, and have pointed out that only the turbulent convection models (TCMs) can be accepted. In the first part of this thesis, models and derivations of both the NMLT and the TCM were introduced. In the second part, i.e., the work part, the studies on the TCM (theoretical analysis and applications), and the development of a new model of the convective overshoot mixing were described in detail. In the work of theoretical analysis on the TCM, the approximate solution and the asymptotic solution were obtained based on some assumptions. The structure of the overshoot region was discussed. In a large space of the free parameters, the approximate/asymptotic solutions are in good agreement with the numerical results. We found an important result that the scale of the overshoot region in which the thermal energy transport is effective is 1 HK (HK is the scale height of turbulence kinetic energy), which does not depend on the free parameters of the TCM. We applied the TCM and a simple overshoot mixing model in three cases. In the solar case, it was found that the temperature gradient in the overshoot region is in agreement with the helioseismic requirements, and the profiles of the solar lithium abundance, sound speed, and density of the solar models are also improved. In the low-mass stars of open

  8. Ray-tracing simulation and SABER satellite observations of convective gravity waves

    NASA Astrophysics Data System (ADS)

    Kalisch, Silvio; Eckermann, Stephen; Ern, Manfred; Preusse, Peter; Riese, Martin; Trinh, Quang Thai; Kim, Young-Ha; Chun, Hye-Yeong

    Gravity waves (GWs) are known as a coupling mechanism between different atmospheric layers. They contribute to the wave-driving of the QBO and are also responsible for driving large scale circulations like the Brewer-Dobson circulation. One major and highly variable source of GWs is convection. Deep convection in the tropics excites GWs with prominent amplitudes and horizontal phase speeds of up to 90 m/s. These GWs propagate upward and, when breaking, release the wave's momentum, thus accelerate the background flow. Direction and magnitude of the acceleration strongly depends on wind filtering between the convective GW source and the considered altitude. Both, the generation mechanism of GWs close to the top of deep convective towers and the wind filtering process during GW propagation largely influence the GW spectrum found in the tropical middle atmosphere and therefore magnitude and direction of the acceleration. We present the results of GW ray-tracing calculations from tropospheric (convective) sources up to the mesosphere. The Gravity wave Regional Or Global RAy-Tracer (GROGRAT) was used to perform the GW trajectory calculations. The convective GW source scheme from Yonsei University (South Korea) served as the lower boundary condition to quantify the GW excitation from convection. Heating rates, cloud top data, and atmospheric background data were provided by the MERRA dataset for the calculation of convective forcing from deep convection and for the atmospheric background of the ray-tracing calculations afterwards. In order to validate our ray-tracing simulation results, we compare them to satellite measurements of temperature amplitudes and momentum fluxes from the SABER instrument. Therefore, observational constrains from limb-sounding instruments have been quantified. Influences of orbit geometry, the instrument's observational filter, and the wavelength shift in the observed GW spectrum are discussed. Geographic structures in the observed global

  9. Turbulent thermal convection in a rotating stratified fluid

    NASA Astrophysics Data System (ADS)

    Levy, M. A.; Fernando, H. J. S.

    2002-09-01

    Turbulent convection induced by heating the bottom boundary of a horizontally homogeneous, linearly (temperature) stratified, rotating fluid layer is studied using a series of laboratory experiments. It is shown that the growth of the convective mixed layer is dynamically affected by background rotation (or Coriolis forces) when the parameter R = (h2[Omega]3/q0)2/3 exceeds a critical value of Rc [approximate] 275. Here h is the depth of the convective layer, [Omega] is the rate of rotation, and q0 is the buoyancy flux at the bottom boundary. At larger R, the buoyancy gradient in the mixed layer appears to scale as (db/dz)ml = C[Omega]2, where C [approximate] 0.02. Conversely, when R < Rc, the buoyancy gradient is independent of [Omega] and approaches that of the non-rotating case. The entrainment velocity, ue, for R > Rc was found to be dependent on [Omega] according to E = [Ri(1 + C[Omega]2/N2)][minus sign]1, where E is the entrainment coefficient based on the convective velocity w[low asterisk] = (q0h)1/3, E = ue/w[low asterisk], Ri is the Richardson number Ri = N2h2/w2[low asterisk], and N is the buoyancy frequency of the overlying stratified layer. The results indicate that entrainment in this case is dominated by non-penetrative convection, although the convective plumes can penetrate the interface in the form of lenticular protrusions.

  10. Increasing vertical mixing to reduce Southern Ocean deep convection in NEMO

    NASA Astrophysics Data System (ADS)

    Heuzé, C.; Ridley, J. K.; Calvert, D.; Stevens, D. P.; Heywood, K. J.

    2015-03-01

    Most CMIP5 models unrealistically form Antarctic Bottom Water by open ocean deep convection in the Weddell and Ross Seas. To identify the triggering mechanisms leading to Southern Ocean deep convection in models, we perform sensitivity experiments on the ocean model NEMO forced by prescribed atmospheric fluxes. We vary the vertical velocity scale of the Langmuir turbulence, the fraction of turbulent kinetic energy transferred below the mixed layer, and the background diffusivity and run short simulations from 1980. All experiments exhibit deep convection in the Riiser-Larsen Sea in 1987; the origin is a positive sea ice anomaly in 1985, causing a shallow anomaly in mixed layer depth, hence anomalously warm surface waters and subsequent polynya opening. Modifying the vertical mixing impacts both the climatological state and the associated surface anomalies. The experiments with enhanced mixing exhibit colder surface waters and reduced deep convection. The experiments with decreased mixing are warmer, open larger polynyas and have deep convection across the Weddell Sea until the simulations end. Extended experiments reveal an increase in the Drake Passage transport of 4 Sv each year deep convection occurs, leading to an unrealistically large transport at the end of the simulation. North Atlantic deep convection is not significantly affected by the changes in mixing parameters. As new climate model overflow parameterisations are developed to form Antarctic Bottom Water more realistically, we argue that models would benefit from stopping Southern Ocean deep convection, for example by increasing their vertical mixing.

  11. Three-dimensional spherical models of layered and whole mantle convection

    NASA Technical Reports Server (NTRS)

    Glatzmaier, Gary A.; Schubert, Gerald

    1993-01-01

    We present numerical calculations of three-dimensional spherical shell thermal convection for constant viscosity and stratified viscosity models of whole-layer and two-layer mantle convection. These four examples are intended to provide theoretical guidance for determining the style of convection that is occurring in Earth's mantle. An impermeable interface between the upper and lower convecting shells in the two-layer solutions is placed at a depth of 670 km to coincide with the mantle seismic discontinuity that divides the upper and lower mantle. The interface results in an internal thermal boundary layer that raises the mean temperature in the lower shell by about 1400 K compared to the whole-layer solutions. The patterns of convection in the upper part of the whole-layer solutions are dominated by narrow arcuate sheetlike downflows in a background of weak upflow. In contrast, the upper shells of the two-layer solutions have complicated networks of convective rolls with the upflows and downflows having very similar structure. The structure of convection in the lower shells is similar to that in the lower part of the whole-layer solutions. Based on the horizontal structure of subduction zones on Earth's surface and on tomographic images of temperature variations in Earth's mantle, we conclude that the style of convection in Earth's mantle is more like that of the whole-mantle models.

  12. Three-dimensional spherical models of layered and whole mantle convection

    NASA Technical Reports Server (NTRS)

    Glatzmaier, Gary A.; Schubert, Gerald

    1993-01-01

    We present numerical calculations of three-dimensional spherical shell thermal convection for constant viscosity and stratified viscosity models of whole-layer and two-layer mantle convection. These four examples are intended to provide theoretical guidance for determining the style of convection that is occurring in Earth's mantle. An impermeable interface between the upper and lower convecting shells in the two-layer solutions is placed at a depth of 670 km to coincide with the mantle seismic discontinuity that divides the upper and lower mantle. The interface results in an internal thermal boundary layer that raises the mean temperature in the lower shell by about 1400 K compared to the whole-layer solutions. The patterns of convection in the upper part of the whole-layer solutions are dominated by narrow arcuate sheetlike downflows in a background of weak upflow. In contrast, the upper shells of the two-layer solutions have complicated networks of convective rolls with the upflows and downflows having very similar structure. The structure of convection in the lower shells is similar to that in the lower part of the whole-layer solutions. Based on the horizontal structure of subduction zones on Earth's surface and on tomographic images of temperature variations in Earth's mantle, we conclude that the style of convection in Earth's mantle is more like that of the whole-mantle models.

  13. Convective organization in the super-parameterized community atmosphere model with constant surface temperature

    NASA Astrophysics Data System (ADS)

    Kuang, Z.

    2015-12-01

    Organization in a moist convecting atmosphere is investigated using the super-parameterized community atmosphere model (SPCAM) in aquaplanet setting with constant surface temperature, with and without planetary rotation. Without radiative and surface feedbacks, convective organization is dominated by convectively coupled gravity waves without planetary rotation and convectively coupled equatorial waves when there is planetary rotation. This behavior is well captured when the cloud resolving model (CRM) in SPCAM is replaced by its linear response function, computed following Kuang (2010), for the state of radiative convective equilibrium (RCE). With radiative feedback, however, convection self-aggregates, and with planetary rotation, the tropical zonal wavenumber-frequency spectrum features a red noise background. These behaviors in the presence of the radiative feedback are not captured when the CRM is replaced by its linear response function around the RCE state with radiative feedback included in the construction. Implications to organization in a moist convecting atmosphere will be discussed. Kuang, Z., Linear response functions of a cumulus ensemble to temperature and moisture perturbations and implication to the dynamics of convectively coupled waves, J. Atmos. Sci., 67, 941-962, (2010)

  14. Stochastic microhertz gravitational radiation from stellar convection

    SciTech Connect

    Bennett, M. F.; Melatos, A.

    2014-09-01

    High Reynolds-number turbulence driven by stellar convection in main-sequence stars generates stochastic gravitational radiation. We calculate the wave-strain power spectral density as a function of the zero-age main-sequence mass for an individual star and for an isotropic, universal stellar population described by the Salpeter initial mass function and redshift-dependent Hopkins-Beacom star formation rate. The spectrum is a broken power law, which peaks near the turnover frequency of the largest turbulent eddies. The signal from the Sun dominates the universal background. For the Sun, the far-zone power spectral density peaks at S(f {sub peak}) = 5.2 × 10{sup –52} Hz{sup –1} at frequency f {sub peak} = 2.3 × 10{sup –7} Hz. However, at low observing frequencies f < 3 × 10{sup –4} Hz, the Earth lies inside the Sun's near zone and the signal is amplified to S {sub near}(f {sub peak}) = 4.1 × 10{sup –27} Hz{sup –1} because the wave strain scales more steeply with distance (∝d {sup –5}) in the near zone than in the far zone (∝d {sup –1}). Hence the Solar signal may prove relevant for pulsar timing arrays. Other individual sources and the universal background fall well below the projected sensitivities of the Laser Interferometer Space Antenna and next-generation pulsar timing arrays. Stellar convection sets a fundamental noise floor for more sensitive stochastic gravitational-wave experiments in the more distant future.

  15. Control of oscillatory thermocapillary convection in microgravity

    NASA Technical Reports Server (NTRS)

    Neitzel, G. Paul

    1994-01-01

    Laboratory and numerical experiments are underway to generate, and subsequently suppress, oscillatory thermocapillary convection in thin layer of silicone oil. The laboratory experiments have succeeded in characterizing the flow state in a limited range of Bond number-Marangoni number space of interest, identifying states of: (1) steady, unicellular, thermocapillary convection; (2) steady, multicellular, thermocapillary convection; and (3) oscillatory thermocapillary convection. Comparisons between experimental results and stability computations for a related basic state will be made.

  16. Compositional convection in viscous melts

    NASA Astrophysics Data System (ADS)

    Tait, Stephen; Jaupart, Claude

    1989-04-01

    DURING solidification of multi-component melts, gradients in temperature and composition develop on different scales because of the large difference between their respective molecular diffusivities. Two consequences are the development of double-diffusive convection1 and the creation of mushy zones in which solid and liquid intimately coexist with a complex small-scale geometry2,3. Theoretical analysis requires simplifying assumptions that must be verified by laboratory experiments. Hitherto, experiments have been carried out with aqueous solutions which do not accurately represent the dynamics of melts with high Prandtl numbers, such as magmas. Here we describe the characteristics of compositional convection using a new experimental technique which allows the viscosity of the solution to be varied independently of chemical composition and liquidus temperature. A supereutectic melt was cooled from below, causing the growth of a horizontal layer of crystals. Convective instability occurred when the local solutal Rayleigh number of the compositional boundary layer ahead of the advancing crystallization front attained a value of ~3 on average. We observed a novel regime of convection in which the thermal boundary layer above the crystallization front was essentially unmodified by the motion of the plumes. The plumes carried a small heat flux and did not mix the fluid to a uniform temperature.

  17. Severe convective environments in Reanalyses

    NASA Astrophysics Data System (ADS)

    Gutierrez, G.; Kennedy, A. D.

    2014-12-01

    Climate change implies an altering of weather patterns that may change the frequency of high impact events such as severe thunderstorms and their associated dangers (damaging winds, torrential rains, hail, and tornadoes). Presently, very little is known about how climate change will impact these events. Since these phenomenon are not resolved by climate models, proxies are required to understand how these events may change in the future.Prior to investigating how convective environments change in the future, a reference must be obtained to understand the current climatology of convective environments. Studies such as Kennedy et al. (2011) have shown there are significant differences in reanalyses for regions prone to severe weather.Severe weather parameters such as Convective Available Potential Energy (CAPE), Lifted Index, K Index, Total Totals, 0-1 km shear, 0-3 km shear and 0-6 km shear are calculated using soundings from reanalyses for known severe convective environments. Reanalyses included in this study are the North American Regional Reanalysis (NARR), Modern-Era Retrospective Analysis for Research and Applications (MERRA), 20th Century Reanalysis (20CR), Climate Forecast System Reanalysis (CFSR), Japanese 25-year Reanalysis (JRA25), and Japanese 55-year Reanalysis (JRA55). Preliminary findings are presented. If time allows, multi-parameter indices such as Energy Helicity Index, Bunkers storm motion, Significant Tornado Parameter, and Supercell Composite Parameter will also be compared.

  18. Test method selection, validation against field data, and predictive modelling for impact evaluation of stabilised waste disposal.

    PubMed

    van der Sloot, Hans A; van Zomeren, Andre; Meeussen, Johannes C L; Seignette, Paul; Bleijerveld, Rob

    2007-03-15

    In setting criteria for landfill classes in Annex II of the EU Landfill Directive, it proved to be impossible to derive criteria for stabilised monolithic waste due to the lack of information on release and release controlling factors in stabilised waste monofills. In this study, we present a scientific basis, which enables a realistic description of the environmental impact of stabilised waste landfills. The work in progress involves laboratory testing of different stabilisation recipes, pilot scale studies on site and evaluation of field leachate from a full-scale stabilisation landfill. We found that the pHs in run-off and in percolate water from the pilot experiment are both around neutral. The neutral pH in run-off is apparently caused by the rapid atmospheric carbonation of those alkaline constituents that are released. The soil, used as a liner protection layer, controls the release to the subsurface below the landfill. This soil layer buffers pH and binds metals. The modelling results show that the chemistry is understood rather well. Differences between predicted and actual leaching might then be attributed to discrepancies in the description of sorption processes, complexation to organic matter and/or kinetic effects in the leaching tests. We conclude that this approach resulted in a new scientific basis for environmental impact assessment of stabilised waste landfills. The integrated approach has already resulted in a number of very valuable observations, which can be used to develop a sustainable landfill for monolithic waste and to provide guidance for the management of waste to be stabilised (e.g. improved waste mix design).

  19. An optimised small-molecule stabiliser of the 14-3-3-PMA2 protein-protein interaction.

    PubMed

    Richter, Anja; Rose, Rolf; Hedberg, Christian; Waldmann, Herbert; Ottmann, Christian

    2012-05-21

    Modulation of protein-protein interactions (PPIs) is a highly demanding, but also a very promising approach in chemical biology and targeted drug discovery. In contrast to inhibiting PPIs with small, chemically tractable molecules, stabilisation of these interactions can only be achieved with complex natural products, like rapamycin, FK506, taxol, forskolin, brefeldin and fusicoccin. Fusicoccin stabilises the activatory complex of the plant H(+)-ATPase PMA2 and 14-3-3 proteins. Recently, we have shown that the stabilising effect of fusicoccin could be mimicked by a trisubstituted pyrrolinone (pyrrolidone1, 1). Here, we report the synthesis, functional activity and crystal structure of derivatives of 1 that stabilise the 14-3-3-PMA2 complex. With a limited compound collection three modifications that are important for activity enhancement could be determined: 1) conversion of the pyrrolinone scaffold into a pyrazole, 2) introduction of a tetrazole moiety to the phenyl ring that contacts PMA2, and 3) addition of a bromine to the phenyl ring that exclusively contacts the 14-3-3 protein. The crystal structure of a pyrazole derivative of 1 in complex with 14-3-3 and PMA2 revealed that the more rigid core of this molecule positions the stabiliser deeper into the rim of the interface, enlarging especially the contact surface to PMA2. Combination of the aforementioned features gave rise to a molecule (37) that displays a threefold increase in stabilising the 14-3-3-PMA2 complex over 1. Compound 37 and the other active derivatives show no effect on two other important 14-3-3 protein-protein interactions, that is, with CRaf and p53. This is the first study that describes the successful optimisation of a PPI stabiliser identified by screening. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. How stratified is mantle convection?

    NASA Astrophysics Data System (ADS)

    Puster, Peter; Jordan, Thomas H.

    1997-04-01

    We quantify the flow stratification in the Earth's mid-mantle (600-1500 km) in terms of a stratification index for the vertical mass flux, Sƒ (z) = 1 - ƒ(z) / ƒref (z), in which the reference value ƒref(z) approximates the local flux at depth z expected for unstratified convection (Sƒ=0). Although this flux stratification index cannot be directly constrained by observations, we show from a series of two-dimensional convection simulations that its value can be related to a thermal stratification index ST(Z) defined in terms of the radial correlation length of the temperature-perturbation field δT(z, Ω). ST is a good proxy for Sƒ at low stratifications (Sƒ<0.2), where it rises with stratification strength much more rapidly than Sƒ. Assuming that the shear-speed variations δβ(z, Ω) imaged by seismic tomography are primarily due to convective temperature fluctuations, we can approximate ST by Sβ, the analogous index for the radial correlation length of δβ, and thereby construct bounds on Sƒ. We discuss several key issues regarding the implementation of this strategy, including finite resolution of the seismic data, biases due to the parameterization of the tomographic models, and the bias and variance due to noise. From the comparison of the numerical simulations with recent tomographic structures, we conclude that it is unlikely that convection in the Earth's mantle has Sƒ≳0.15. We consider the possibility that this estimate is biased because mantle convection is intermittent and therefore that the present-day tomographic snapshot may differ from its time average. Although this possibility cannot be dismissed completely, we argue that values of Sƒ≳0.2 can be discounted under a weak version of the Uniformitarian Principle. The bound obtained here from global tomography is consistent with local seismological evidence for slab flux into the lower mantle; however, the total material flux has to be significantly greater (by a factor of 2-3) than that

  1. Influence of convection on microstructure

    NASA Technical Reports Server (NTRS)

    Wilcox, William R.; Regel, Liya L.

    1992-01-01

    The primary motivation for this research has been to determine the cause for space processing altering the microstructure of some eutectics, especially the MnBi-Bi eutectic. Prior experimental research at Grumman and here showed that the microstructure of MnBi-Bi eutectic is twice as fine when solidified in space or in a magnetic field, is uninfluenced by interfacial temperature gradient, adjusts very quickly to changes in freezing rate, and becomes coarser when spin-up/spin-down (accelerated crucible rotation technique) is used during solidification. Theoretical work at Clarkson predicted that buoyancy driven convection on earth could not account for the two fold change in fiber spacing caused by solidification in space. However, a lamellar structure with a planar interface was assumed, and the Soret effect was not included in the analysis. Experimental work at Clarkson showed that the interface is not planar, and that MnBi fibers project out in front of the Bi matrix on the order of one fiber diameter. Originally four primary hypotheses were to be tested under this current grant: (1) a fibrous microstructure is much more sensitive to convection than a lamellar microstructure, which was assumed in our prior theoretical treatment; (2) an interface with one phase projecting out into the melt is much more sensitive to convection than a planar interface, which was assumed in our prior theoretical treatment; (3) the Soret effect is much more important in the absence of convection and has a sufficiently large influence on microstructure that its action can explain the flight results; and (4) the microstructure is much more sensitive to convection when the composition of the bulk melt is off eutectic. As reported previously, we have learned that while a fibrous microstructure and a non-planar interface are more sensitive to convection than a lamellar microstructure with a planar interface, the influence of convection remains too small to explain the flight and magnetic

  2. Subcritical convection in an internally heated layer

    NASA Astrophysics Data System (ADS)

    Xiang, Linyan; Zikanov, Oleg

    2017-06-01

    Thermal convection in a horizontal layer with uniform internal heating and stress-free constant-temperature boundaries is analyzed numerically. The work is motivated by the questions arising in the development of liquid metal batteries, in which convection is induced by the Joule heating of electrolyte. It is demonstrated that three-dimensional convection cells exist at subcritical Rayleigh numbers.

  3. Stabilisation of strawberry (Fragaria x ananassa Duch.) anthocyanins by different pectins.

    PubMed

    Buchweitz, M; Speth, M; Kammerer, D R; Carle, R

    2013-12-01

    The objective of the present study was to evaluate the effects of different pectins on strawberry anthocyanins in viscous model solutions at pH 3.0. For this purpose, low esterified amidated, low and high methyl esterified citrus and apple pectins, and a sugar beet pectin (SBP), respectively, were added to strawberry extracts. The latter were predominantly composed of pelargonidin-glycosides, containing either reduced (E-1) or original amounts of non-anthocyanin phenolics (E-2). Model systems were stored for 18 weeks at 20±0.5 °C protected from light, and anthocyanins were quantitated in regular intervals by HPLC-DAD analyses. Half-life (t1/2) and destruction (D) values were calculated based on first-order kinetics. Generally, significant differences in pigment retention could be ascribed to differing pectin sources, while variation in the degree of esterification and amidation, respectively, had negligible effects. Compared to systems without added pectin, apple pectins and SPB enhanced anthocyanin stability moderately, while stabilising effects of citrus pectins were poor or even imperceptible. Generally, the amount of non-anthocyanin phenolics and the addition of citrate did not markedly affect anthocyanin stability. However, pectins had no influence on total phenolic contents (Folin-Ciocalteu assay) and antioxidant capacities (FRAP and TEAC assay) of strawberry phenolics over time. For pelargonidin-3-glucoside and -rutinoside largely consistent stabilities were found in all model systems. In contrast, pelargonidin-3-malonylglucoside was less stable in the blank, and stabilisation by pectins was always negligible. The findings of the present study are contrary to results reported previously for the stabilisation of cyanidin- and delphinidin-glycosides in similar model systems prepared with black currant extracts, indicating a high impact of the number of hydroxyl groups in the anthocyanin B-ring. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. Effect of duckweed cover on greenhouse gas emissions and odour release from waste stabilisation ponds.

    PubMed

    van der Steen, N P; Nakiboneka, P; Mangalika, L; Ferrer, A V M; Gijzen, H J

    2003-01-01

    Treatment of wastewater in stabilisation pond systems prevents the negative environmental impact of uncontrolled disposal of sewage. However, even a natural treatment system may generate secondary negative environmental impacts in terms of energy consumption, emission of greenhouse gases and emission of odorous compounds. Whereas natural systems have an advantage over electro-mechanical systems in that they use less hardware and less energy, it is not yet known whether secondary environmental effects in the form of greenhouse gas emissions are lower for these systems. This research intends to be a first step in the direction of answering this question by assessing gas emissions from two types of natural systems, namely algae-based and duckweed-based stabilisation ponds. The H2S volatilisation from laboratory scale pond-reactors has been determined by drawing the air above the water surface continuously through a solution of 1 M NaOH for absorption of sulphide. The amount of H2S that volatilised from the algae pond-reactor, and was trapped in the NaOH trap, was found to be 2.5-86 mg/m2/day. The H2S volatilisation from the duckweed pond-reactor was found to be negligible, even though the sulphide concentration was 9.7 mg/l S(2-). The duckweed cover was a physical barrier for volatilisation, since bubbles were trapped in the cover. In addition the duckweed layer was found to be afavourable environment for both aerobic sulphide oxidisers (Beggiatoa gigantae) as well as for photosynthetic purple sulphur bacteria belonging to the genus Chromatium. These may also have contributed to the prevention of H2S volatilisation. Results on methane emissions were not conclusive so far, but the same mechanisms that prevent H2S volatilisation may also prevent methane volatilisation. Therefore it was concluded that duckweed covers on stabilisation ponds may reduce the emission of both odorous and greenhouse gases.

  5. Granular convection observed by magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Ehrichs, E. E.; Jaeger, H. M.; Karczmar, Greg S.; Knight, James B.; Kuperman, Vadim Yu.; Nagel, Sidney R.

    1995-03-01

    Vibrations in a granular material can spontaneously produce convection rolls reminiscent of those seen in fluids. Magnetic resonance imaging provides a sensitive and noninvasive probe for the detection of these convection currents, which have otherwise been difficult to observe. A magnetic resonance imaging study of convection in a column of poppy seeds yielded data about the detailed shape of the convection rolls and the depth dependence of the convection velocity. The velocity was found to decrease exponentially with depth; a simple model for this behavior is presented here.

  6. Granular convection observed by magnetic resonance imaging

    SciTech Connect

    Ehrichs, E.E.; Jaeger, H.M.; Knight, J.B.; Nagel, S.R.; Karczmar, G.S.; Kuperman, V.Yu.

    1995-03-17

    Vibrations in a granular material can spontaneously produce convection rolls reminiscent of those seen in fluids. Magnetic resonance imaging provides a sensitive and noninvasive probe for the detection of these convection currents, which have otherwise been difficult to observe. A magnetic resonance imaging study of convection in a column of poppy seeds yielded data about the detailed shape of the convection rolls and the depth dependence of the convection velocity. The velocity was found to decrease exponentially with depth; a simple model for this behavior is presented here. 31 refs., 4 figs.

  7. Tropical Convection's Roles in Tropical Tropopause Cirrus

    NASA Technical Reports Server (NTRS)

    Boehm, Matthew T.; Starr, David OC.; Verlinde, Johannes; Lee, Sukyoung

    2002-01-01

    The results presented here show that tropical convection plays a role in each of the three primary processes involved in the in situ formation of tropopause cirrus. First, tropical convection transports moisture from the surface into the upper troposphere. Second, tropical convection excites Rossby waves that transport zonal momentum toward the ITCZ, thereby generating rising motion near the equator. This rising motion helps transport moisture from where it is detrained from convection to the cold-point tropopause. Finally, tropical convection excites vertically propagating tropical waves (e.g. Kelvin waves) that provide one source of large-scale cooling near the cold-point tropopause, leading to tropopause cirrus formation.

  8. A transilient matrix for moist convection

    SciTech Connect

    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.

  9. Weakly non-Boussinesq convection in a gaseous spherical shell

    NASA Astrophysics Data System (ADS)

    Korre, Lydia; Brummell, Nicholas; Garaud, Pascale

    2017-09-01

    We examine the dynamics associated with weakly compressible convection in a spherical shell by running 3D direct numerical simulations using the Boussinesq formalism [Spiegel and Veronis, Astrophys. J. 131, 442 (1960), 10.1086/146849]. Motivated by problems in astrophysics, we assume the existence of a finite adiabatic temperature gradient ∇ Tad and use mixed boundary conditions for the temperature with fixed flux at the inner boundary and fixed temperature at the outer boundary. This setup is intrinsically more asymmetric than the more standard case of Rayleigh-Bénard convection in liquids between parallel plates with fixed temperature boundary conditions. Conditions where there is substantial asymmetry can cause a dramatic change in the nature of convection and we demonstrate that this is the case here. The flows can become pressure- rather than buoyancy-dominated, leading to anomalous heat transport by upflows. Counterintuitively, the background temperature gradient ∇ T ¯ can develop a subadiabatic layer (where g .∇ T ¯convection remains vigorous at every point across the shell. This indicates a high degree of nonlocality.

  10. A comparison of stabilisation approaches for finite-volume simulation of viscoelastic fluid flow

    NASA Astrophysics Data System (ADS)

    Chen, Xingyuan; Marschall, Holger; Schäfer, Michael; Bothe, Dieter

    2013-07-01

    In this work we compare different stabilisation approaches currently used in the simulation of viscoelastic fluid flow. These approaches are: the both-sides diffusion, the positive definiteness preserving scheme, the log-conformation tensor representation and the symmetry factorisation of the conformation tensor. The evaluation of these approaches is done regarding their implementation complexity, stability, accuracy, efficiency and applicability to complex problems. Their performances are examined for an Oldroyd-B fluid in the test cases of lid-driven cavity, flow past a cylinder and 4:1 contraction flow. We summarise the situations in which the different approaches can be recommended.

  11. Arm-length stabilisation for interferometric gravitational-wave detectors using frequency-doubled auxiliary lasers.

    PubMed

    Mullavey, Adam J; Slagmolen, Bram J J; Miller, John; Evans, Matthew; Fritschel, Peter; Sigg, Daniel; Waldman, Sam J; Shaddock, Daniel A; McClelland, David E

    2012-01-02

    Residual motion of the arm cavity mirrors is expected to prove one of the principal impediments to systematic lock acquisition in advanced gravitational-wave interferometers. We present a technique which overcomes this problem by employing auxiliary lasers at twice the fundamental measurement frequency to pre-stabilise the arm cavities' lengths. Applying this approach, we reduce the apparent length noise of a 1.3 m long, independently suspended Fabry-Perot cavity to 30 pm rms and successfully transfer longitudinal control of the system from the auxiliary laser to the measurement laser.

  12. Spectroscopic properties of erbium-doped yttria-stabilised zirconia crystals

    SciTech Connect

    Ryabochkina, P A; Sidorova, N V; Ushakov, S N; Lomonova, E E

    2014-02-28

    Yttria-stabilised zirconia crystals ZrO{sub 2} – Y{sub 2}O{sub 3} (6 mol %) – Er{sub 2}O{sub 3} (5.85 mol %) are grown by directional crystallisation in a cold container using direct RF melting. The spectral and luminescent properties of these crystals are studied in order to use them as active media of solid state lasers emitting in the wavelength range 1.5 – 1.7 μm. (active media)

  13. Amplifying properties of LiF crystals with stabilised F{sub 2}{sup +} colour centres

    SciTech Connect

    Basiev, Tasoltan T; Ermakov, I V; Konyushkin, V A; Pukhov, K K; Glasbeek, M

    1998-02-28

    A study was made of the amplifying properties of LiF crystals with stabilised F{sub 2}{sup +} colour centres with a view to possible use of these crystals as amplifiers of weak IR radiation pulses. A single-pass system pumped with the second harmonic of a pulsed Nd : YAG laser ({lambda} =532 nm) made it possible to achieve 20-fold optical amplification of broad-band nanosecond IR radiation from a laser diode ({lambda}=900 nm). (laser applications and other topics in quantum electronics)

  14. Marine-based waste stabilisation ponds: an evaluation of the hydraulic viability.

    PubMed

    Burrows, R; Ali, K H; Tickell, R G; Hedges, T S; Pearson, H W; Mara, D D

    2001-01-01

    Marine-Based Waste Stabilisation Ponds, formed by floating boom/skirt curtain enclosures anchored in sheltered waters, have recently been proposed for provision of low-cost effluent treatment facilities where land availability is limited in rapidly expanding coastal cities in the Third World. This paper outlines findings from a viability assessment, which drew on a preliminary site evaluation and baseline environmental survey (for a site in sheltered waters in the Far East), laboratory studies involving scale model tests in wave/wind/current flumes, and a structural and design loading study. It focuses on hydraulic and hydrodynamic considerations and reports the study's conclusions.

  15. An update of stabilisation exercises for low back pain: a systematic review with meta-analysis.

    PubMed

    Smith, Benjamin E; Littlewood, Chris; May, Stephen

    2014-12-09

    Non-specific low back pain (NSLBP) is a large and costly problem. It has a lifetime prevalence of 80% and results in high levels of healthcare cost. It is a major cause for long term sickness amongst the workforce and is associated with high levels of fear avoidance and kinesiophobia. Stabilisation (or 'core stability') exercises have been suggested to reduce symptoms of pain and disability and form an effective treatment. Despite it being the most commonly used form of physiotherapy treatment within the UK there is a lack of positive evidence to support its use. The aims of this systematic review update is to investigate the effectiveness of stabilisation exercises for the treatment of NSLBP, and compare any effectiveness to other forms of exercise. A systematic review published in 2008 was updated with a search of PubMed, CINAHL, AMED, Pedro and The Cochrane Library, October 2006 to October 2013. Two authors independently selected studies, and two authors independently extracted the data. Methodological quality was evaluated using the PEDro scale. Meta-analysis was carried out when appropriate. 29 studies were included: 22 studies (n = 2,258) provided post treatment effect on pain and 24 studies (n = 2,359) provided post treatment effect on disability. Pain and disability scores were transformed to a 0 to 100 scale. Meta-analysis showed significant benefit for stabilisation exercises versus any alternative treatment or control for long term pain and disability with mean difference of -6.39 (95% CI -10.14 to -2.65) and -3.92 (95% CI -7.25 to -0.59) respectively. The difference between groups was clinically insignificant. When compared with alternative forms of exercise, there was no statistical or clinically significant difference. Mean difference for pain was -3.06 (95% CI -6.74 to 0.63) and disability -1.89 (95% CI -5.10 to 1.33). There is strong evidence stabilisation exercises are not more effective than any other form of active exercise in the long

  16. Stabilisation of a class of 2-DOF underactuated mechanical systems via direct Lyapunov approach

    NASA Astrophysics Data System (ADS)

    Turker, Turker; Gorgun, Haluk; Cansever, Galip

    2013-06-01

    This paper represents an alternative stabilisation procedure for a class of two degree-of-freedom underactuated mechanical systems based on a set of transformations and a Lyapunov function. After simplifying dynamic equations of the system via partial feedback linearisation and coordinate changes, the stability of the system is provided with Lyapunov's direct method. Proposed control scheme is used on two different examples and asymptotic convergence for each system is proven by means of La Salle's invariance principle. The designed controller is successfully illustrated through numerical simulations for each example.

  17. Global adaptive exponential stabilisation for nonlinear systems with multiple unknown control directions

    NASA Astrophysics Data System (ADS)

    Sun, Xifang; Chen, Weisheng; Wu, Jian

    2016-12-01

    In this paper, we address the global generalised exponential stabilisation problem for a class of lower-triangular systems with multiple unknown directions. Instead of the well-known Nussbaum-gain adaptive rule, a Lyapunov-based adaptive logic switching rule is proposed to seek the correct control directions for such systems. The main advantage of the proposed controller is that it can guarantee the global generalised exponential stability of closed-loop systems. Simulation examples are given to verify the effectiveness of the developed control approach.

  18. Semi-global decentralised output feedback stabilisation for a class of uncertain nonlinear systems

    NASA Astrophysics Data System (ADS)

    Zhai, Jun-yong; Zha, Wen-ting; Fei, Shu-min

    2013-06-01

    This paper discusses the problem of semi-global decentralised output feedback control for a class of uncertain nonlinear systems. Based on the ideas of the homogeneous systems theory and the adding a power integrator technique, we first design a homogeneous observer and an output feedback control law for each nominal subsystem without the nonlinearities. Then, using the homogeneous domination approach, we relax the linear growth condition to a polynomial one and construct decentralised stabilisers to render the nonlinear system semi-globally asymptotically stable. Two simulation examples are provided to show the effectiveness of the control scheme.

  19. Mathematical modelling of postbuckling in a slender beam column for active stabilisation control with respect to uncertainty

    NASA Astrophysics Data System (ADS)

    Enss, Georg C.; Platz, Roland; Hanselka, Holger

    2012-04-01

    Buckling is an important design constraint in light-weight structures as it may result in the collapse of an entire structure. When a mechanical beam column is loaded above its critical buckling load, it may buckle. In addition, if the actual loading is not fully known, stability becomes highly uncertain. To control uncertainty in buckling, an approach is presented to actively stabilise a slender flat column sensitive to buckling. For this purpose, actively controlled forces applied by piezoelectric actuators located close to the column's clamped base stabilise the column against buckling at critical loading. In order to design a controller to stabilise the column, a mathematical model of the postcritically loaded system is needed. Simulating postbuckling behaviour is important to study the effect of axial loads above the critical axial buckling load within active buckling control. Within this postbuckling model, different kinds of uncertainty may occur: i) error in estimation of model parameters such as mass, damping and stiffness, ii) non-linearities e. g. in the assumption of curvature of the column's deflection shapes and many more. In this paper, numerical simulations based on the mathematical model for the postcritically axially loaded column are compared to a mathematical model based on experiments of the actively stabilised postcritically loaded real column system using closed loop identification. The motivation to develop an experimentally validated mathematical model is to develop of a model based stabilising control algorithm for a real postcritically axially loaded beam column.

  20. Generalized Convective Quasi-Equilibrium Closure

    NASA Astrophysics Data System (ADS)

    Yano, Jun-Ichi; Plant, Robert

    2016-04-01

    Arakawa and Schubert proposed convective quasi-equilibrium as a basic principle for closing their spectrum mass-flux convection parameterization. In deriving this principle, they show that the cloud work function is a key variable that controls the growth of convection. Thus, this closure hypothesis imposes a steadiness of the cloud work function tendency. This presentation shows how this principle can be generalized so that it can also encompasses both the CAPE and the moisture-convergence closures. Note that the majority of the current mass-flux convection parameterization invokes a CAPE closure, whereas the moisture-convergence closure was extremely popular historically. This generalization, in turn, includes both closures as special cases of convective quasi-equilibrium. This generalization further suggests wide range of alternative possibilities for convective closure. In general, a vertical integral of any function depending on both large-scale and convective-scale variables can be adopted as an alternative closure variables, leading to an analogous formulation as Arakawa and Schubert's convective quasi-equilibrium formulation. Among those, probably the most fascinating possibility is to take a vertical integral of the convective-scale moisture for the closure. Use of a convective-scale variable for closure has a particular appeal by not suffering from a loss of predictability of any large-scale variables. That is a main problem with any of the current convective closures, not only for the moisture-convergence based closure as often asserted.

  1. A continuous buoyancy based convection scheme

    NASA Astrophysics Data System (ADS)

    Guérémy, J.-F.

    2009-04-01

    A new and consistent convection scheme, providing a continuous 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). 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, deep convection (TOGA), trade wind shallow convection (BOMEX) and strato-cumulus (FIRE), together with a entire continental diurnal cycle of convection (ARM). The emphasis is put on the characteristics of the scheme which enable a continuous treatment of convection. A General Circulation Model (GCM) 23-year simulation is also presented in order to assess the model climate against the observed one.

  2. Natural convection in low-g environments

    NASA Technical Reports Server (NTRS)

    Grodzka, P. G.; Bannister, T. C.

    1974-01-01

    The present state of knowledge in the area of low-g natural convection is reviewed, taking into account a number of experiments conducted during the Apollo 14, 16, and 17 space flights. Convections due to steady low-g accelerations are considered. Steady g-levels result from spacecraft rotation, gravity gradients, solar wind, and solar pressure. Varying g-levels are produced by engine burns, attitude control maneuvers, and onboard vibrations from machinery or astronaut movement. Thermoacoustic convection in a low-g environment is discussed together with g-jitter convection, surface tension-driven convection, electrohydrodynamics under low-g conditions, phase change convection, and approaches for the control and the utilization of convection in space.

  3. Seismic Constraints on Interior Solar Convection

    NASA Technical Reports Server (NTRS)

    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.

  4. Seismology of Convection in the Sun

    NASA Astrophysics Data System (ADS)

    Hanasoge, Shravan

    2015-08-01

    Solar convection lies in extraordinary regime of dynamical parameters. Convective processes in the Sun drive global fluid circulations and magnetic fields, which in turn affect its visible outer layers (solar activity) and, more broadly, the heliosphere (space weather). The precise determination of the depth of solar convection zone, departures from adiabaticity of the temperature gradient, and the internal rotation rate as a function of latitude and depth are among the seminal contributions of helioseismology towards understanding convection in the Sun. Contemporary helioseismology, which is focused on inferring the properties of three-dimensional convective features, suggests that transport velocities are substantially smaller than theoretical predictions. Furthermore, helioseismology provides important constraints on the anisotropic Reynolds stresses that control the global dynamics of the solar convection zone. In this review, I will discuss the state of our understanding of convection in the Sun, with a focus on helioseismic diagnostics.

  5. The Spectral Signature of Rotating, Stratified Convection

    NASA Astrophysics Data System (ADS)

    Featherstone, N. A.; Hindman, B.

    2016-12-01

    Recent helioseimic measurements of convective amplitudes in the Sun indicate that deep solar convection may be operating in a surprisingly low-Rossby number regime. Solar convection, it seems, might share more in common with convection in Earth's core than is generally assumed. Convection, an indispensable component of the dynamo, occurs in the midst of rotation, and yet we know troublingly little about how the influence of that rotation manifests across the broad range of convective scales present in the Sun. We are nevertheless well aware that the interaction of rotation and convection profoundly impacts many aspects of the solar dynamo. The structure of deep meridional circulation, which may bear on the timing of the solar cycle, is sensitive to the degree of rotational constraint felt by its underlying convective motions. The differential rotation, a vital source of large-scale shear in some dynamo models, results from convective motions that transport not just heat, but angular momentum. Rotation imbues convection with a sense of helicity, supplying a source of turbulent EMF to the dynamo, and it is only in regimes of strong rotational constraint that fully nonlinear models of stellar convection have evinced cyclic dynamo behavior. As we leverage helioseismic analyses in seeking further insight into the operation of the solar dynamo, it is prudent to ask ourselves how rotation shapes the spectral distribution of convective power. A solid understanding of such spectral signatures will only serve to complement helioseismic analyses directed toward understanding the operation of the dynamo. I will present numerical results from a series of nonrotating and rotating convection simulations conducted in full spherical geometry. This presentation will focus on how convective velocity spectra differ between the rotating and non-rotating models and how that behavior changes as simulations are pushed toward rotationally-constrained regimes that are, in many ways, more

  6. Label-free in vitro toxicity and uptake assessment of citrate stabilised gold nanoparticles in three cell lines

    PubMed Central

    2013-01-01

    Background Reliable in vitro toxicity testing is needed prior to the commencement of in vivo testing necessary for hazard identification and risk assessment of nanoparticles. In this study, the cytotoxicity and uptake of 14 nm and 20 nm citrate stabilised gold nanoparticles (AuNPs) in the bronchial epithelial cell line BEAS-2B, the Chinese hamster ovary cell line CHO, and the human embryonic kidney cell line HEK 293 were investigated. Methods Cytotoxicity of the AuNPs was assessed via traditional XTT-, LDH-, and ATP-based assays, followed by cell impedance studies. Dark-field imaging and hyperspectral imaging were used to confirm the uptake of AuNPs into the cells. Results Interference of the AuNPs with the XTT- and ATP-based assays was overcome through the use of cell impedance technology. AuNPs were shown to be relatively non-toxic using this methodology; nevertheless CHO cells were the most sensitive cell type with 20 nm AuNPs having the highest toxicity. Uptake of both 14 nm and 20 nm AuNPs was observed in all cell lines in a time- and cell type-dependent manner. Conclusions Using the cell impedance and dark-field hyperspectral imaging technologies, it was possible to study the toxicity of AuNPs in different cell lines and show that these cells could internalize AuNPs with their subsequent intracellular aggregation. It was also possible to show that this toxicity would not correlate with the level of uptake but it would correlate with cell-type and the size of the AuNPs. Therefore, these two label-free methodologies used in this study are suitable for in vitro studies on the effects of AuNPs, and could present themselves as appropriate and valuable methodologies for future nanoparticle toxicity and uptake studies. PMID:24103467

  7. Aerosol-radiation-cloud interactions in a regional coupled model: the effects of convective parameterisation and resolution

    NASA Astrophysics Data System (ADS)

    Archer-Nicholls, Scott; Lowe, Douglas; Schultz, David M.; McFiggans, Gordon

    2016-05-01

    The Weather Research and Forecasting model with Chemistry (WRF-Chem) has been used to simulate a region of Brazil heavily influenced by biomass burning. Nested simulations were run at 5 and 1 km horizontal grid spacing for three case studies in September 2012. Simulations were run with and without fire emissions, convective parameterisation on the 5 km domain, and aerosol-radiation interactions in order to explore the differences attributable to the parameterisations and to better understand the aerosol direct effects and cloud responses. Direct aerosol-radiation interactions due to biomass burning aerosol resulted in a net cooling, with an average short-wave direct effect of -4.08 ± 1.53 Wm-2. However, around 21.7 Wm-2 is absorbed by aerosol in the atmospheric column, warming the atmosphere at the aerosol layer height, stabilising the column, inhibiting convection, and reducing cloud cover and precipitation. The changes to clouds due to radiatively absorbing aerosol (traditionally known as the semi-direct effects) increase the net short-wave radiation reaching the surface by reducing cloud cover, producing a secondary warming that counters the direct cooling. However, the magnitude of the semi-direct effect was found to be extremely sensitive to the model resolution and the use of convective parameterisation. Precipitation became organised in isolated convective cells when not using a convective parameterisation on the 5 km domain, reducing both total cloud cover and total precipitation. The SW semi-direct effect varied from 6.06 ± 1.46 with convective parameterisation to 3.61 ± 0.86 Wm-2 without. Convective cells within the 1 km domain are typically smaller but with greater updraft velocity than equivalent cells in the 5 km domain, reducing the proportion of the domain covered by cloud in all scenarios and producing a smaller semi-direct effect. Biomass burning (BB) aerosol particles acted as cloud condensation nuclei (CCN), increasing the droplet number

  8. Convective aggregation in realistic convective-scale simulations

    NASA Astrophysics Data System (ADS)

    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</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6698756','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6698756"><span>Combination microwave gas <span class="hlt">convection</span> oven</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Day, W.J. Jr.</p> <p>1984-02-07</p> <p>A combination microwave gas <span class="hlt">convection</span> oven is described having a tubular burner operating in an induced draft environment. A blower system draws air from a combustion chamber forcing it into the heating cavity. The slight pressure created in the combustion chamber draws in air from the heating cavity through perforations communicating therebetween completing the <span class="hlt">convection</span> recirculation. The negative pressure in the combustion chamber also causes secondary combustion air to be drawn up along the sides of the burner which is positioned adjacent to an aperture in the floor of the combustion chamber. A plurality of top ports in the burner provides low port loading. The structure provides good flame characteristics with low noise of combustion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..4310611O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..4310611O"><span>Slantwise <span class="hlt">convection</span> on fluid planets</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>O'Neill, Morgan E.; Kaspi, Yohai</p> <p>2016-10-01</p> <p>Slantwise <span class="hlt">convection</span> should be ubiquitous in the atmospheres of rapidly rotating fluid planets. We argue that <span class="hlt">convectively</span> adjusted lapse rates should be interpreted along constant angular momentum surfaces instead of lines parallel to the local gravity vector. Using Cassini wind observations of Jupiter and different lapse rates to construct toy atmospheres, we explore parcel paths in symmetrically stable and unstable weather layers by the numerically modeled insertion of negatively buoyant bubbles. Low-Richardson number atmospheres are very susceptible to transient symmetric instability upon local diabatic forcing, even outside of the tropics. We explore parcel paths in symmetrically stable and unstable weather layer environments, the latter by adding thermal bubbles to the weather layer. Parcels that cool in Jupiter's belt regions have particularly horizontal paths, with implications for jetward angular momentum fluxes. These considerations may be relevant to the interpretation of Juno's ongoing observations of Jupiter's weather layer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910050107&hterms=China+next+power&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DChina%2Bnext%2Bpower','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910050107&hterms=China+next+power&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3DChina%2Bnext%2Bpower"><span>Power spectra of solar <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Chou, D.-Y.; Labonte, B. J.; Braun, D. C.; Duvall, T. L., Jr.</p> <p>1991-01-01</p> <p>The properties of <span class="hlt">convective</span> motions on the sun are studied using Kitt Peak Doppler images and power spectra of <span class="hlt">convection</span>. The power peaks at a scale of about 29,000 km and drops off smoothly with wavenumber. There is no evidence of apparent energy excess at the scale of the mesogranulation proposed by other authors. The vertical and horizontal power for each wavenumber are obtained and used to calculate the vertical and horizontal velocities of the supergranulation. The amplitude of vertical and horizontal velocities of the supergranulation are 0.034 (+ or - 0.002) km/s and 0.38 (+ or - 0.01) km/s, respectively. The corresponding rms values are 0.024 (+ or - 0.002) km/s and 0.27 (+ or - 0.01) km/s.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1990sfdr.work...76A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1990sfdr.work...76A"><span>Marangoni <span class="hlt">convection</span> under microgravity conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Akiyoshi, Ryo; Enya, Shintaro</p> <p></p> <p>An evaluation is presented of the consequences for crystal growth of the dominant effect exerted by Marangoni <span class="hlt">convection</span> during microgravity crystallization experiments conducted on PbSnTe. During the aircraft experiments in question, 0.02 G was sustained for more than 20 sec. The lessons learned from this experiment will inform the design of Japan's First Material Processing Test, which will be conducted aboard the Space Shuttle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014IJSyS..45.2637C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014IJSyS..45.2637C"><span>On asymptotic <span class="hlt">stabilisation</span> of a chain of integrators with nonlinearity and an uncertain input delay by output feedback</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Choi, Ho-Lim</p> <p>2014-12-01</p> <p>In this paper, we provide an output feedback solution over one given by Choi and Lim [Systems & Control Letters, 59(6), 374-379 (2010)] under more generalised system set-up. More specifically, we consider a <span class="hlt">stabilisation</span> problem of a chain of integrators that has nonlinearity and an uncertain delay in the input by output feedback. The nonlinearity is classified into four types. Then, we propose a memoryless output feedback controller which contains a gain-scaling factor to adjust controller gains depending on the given nonlinearity type. Our stability analysis shows that the controlled system has unique <span class="hlt">stabilisation</span> result associated with each type of nonlinearity. Our result provides a new aspect to the <span class="hlt">stabilisation</span> problem of nonlinear time-delay systems and broadens the existing control results of time-delay systems. Two examples are given for illustration.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013IJC....86..709Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013IJC....86..709Z"><span>L ∞ and L 2 semi-global <span class="hlt">stabilisation</span> of continuous-time periodic linear systems with bounded controls</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Bin; Hou, Ming-Zhe; Duan, Guang-Ren</p> <p>2013-04-01</p> <p>This article is concerned with L ∞ and L 2 semi-global <span class="hlt">stabilisation</span> of continuous-time periodic linear systems with bounded controls. Two problems, namely L ∞ semi-global <span class="hlt">stabilisation</span> with controls having bounded magnitude and L 2 semi-global <span class="hlt">stabilisation</span> with controls having bounded energy, are solved based on solutions to a class of periodic Lyapunov differential equations (PLDEs) resulting from the problem of minimal energy control with guaranteed convergence rate. Under the assumption that the open-loop system is (asymptotically) null controllable with constrained controls, periodic feedback are established to solve the concerned problems. The proposed PLDE-based approaches possess the advantage that the resulting controllers are easy to implement since the designers need only to solve a linear differential equation. A numerical example is worked out to illustrate the effectiveness of the proposed approach.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S53F..03D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S53F..03D"><span>Top Driven Asymmetric Mantle <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Doglioni, C.; Anderson, D. L.</p> <p>2014-12-01</p> <p>The role of the decoupling in the low-velocity zone is crucial for understanding the mechanisms governing plate tectonics and mantle <span class="hlt">convection</span>. Mantle <span class="hlt">convection</span> models fail to integrate plate kinematics and thermodynamics of the mantle. We computed the volume of the plates lost along subduction zones, which is about 306 km3/yr (±15). Mass balance predicts that slabs are compensated by broad passive upwellings beneath oceans, mainly at oceanic ridges and backarc basins. These may correspond to the broad low wavespeed regions found in the upper mantle by tomography. However, W-directed slabs enter the mantle more than 3 times faster (232 km3/yr ±15) than the opposite E- or NE-directed subduction zones (74 km3/yr ±15). This is consistent with the westward drift of the outer shell relative to the underlying mantle, which accounts for the steep dip of W-directed slabs, and the asymmetry between the flanks of oceanic ridges, and the directions of ridge migration. The larger recycling volumes along W-directed subduction zones implies i) asymmetry of the cooling of the underlying mantle and ii) it constrains the "easterly" directed component of the upwelling replacement mantle. In this model, mantle <span class="hlt">convection</span> is tuned by polarized decoupling of the advecting and shearing upper boundary layer. Return mantle flow can be envisaged as a result of passive volume balance rather than as a thermal buoyancy driven upwelling.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20010048416&hterms=Hydrometer&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DHydrometer','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20010048416&hterms=Hydrometer&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DHydrometer"><span>Ice Nucleation in Deep <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Jensen, Eric; Ackerman, Andrew; Stevens, David; Gore, Warren J. (Technical Monitor)</p> <p>2001-01-01</p> <p>The processes controlling production of ice crystals in deep, rapidly ascending <span class="hlt">convective</span> columns are poorly understood due to the difficulties involved with either modeling or in situ sampling of these violent clouds. A large number of ice crystals are no doubt generated when droplets freeze at about -40 C. However, at higher levels, these crystals are likely depleted due to precipitation and detrainment. As the ice surface area decreases, the relative humidity can increase well above ice saturation, resulting in bursts of ice nucleation. We will present simulations of these processes using a large-eddy simulation model with detailed microphysics. Size bins are included for aerosols, liquid droplets, ice crystals, and mixed-phase (ice/liquid) hydrometers. Microphysical processes simulated include droplet activation, freezing, melting, homogeneous freezing of sulfate aerosols, and heterogeneous ice nucleation. We are focusing on the importance of ice nucleation events in the upper part of the cloud at temperatures below -40 C. We will show that the ultimate evolution of the cloud in this region (and the anvil produced by the <span class="hlt">convection</span>) is sensitive to these ice nucleation events, and hence to the composition of upper tropospheric aerosols that get entrained into the <span class="hlt">convective</span> column.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900020154','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900020154"><span>Influence of <span class="hlt">convection</span> on microstructure</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilcox, William R.; Caram, Rubens; Mohanty, A. P.; Seth, Jayshree</p> <p>1990-01-01</p> <p>The mechanism responsible for the difference in microstructure caused by solidifying the MnBi-Bi eutectic in space is sought. The objectives for the three year period are as follows: (1) completion of the following theoretical analyses - determination of the influence of the Soret effect on the average solid composition versus distance of off-eutectic mixtures directionally solidified in the absence of <span class="hlt">convection</span>, determination of the influence of <span class="hlt">convection</span> on the microstructure of off-eutectic mixtures using a linear velocity profile in the adjacent melt, determination of the influence of volumetric changes during solidification on microconvection near the freezing interface and on microstructure, and determination of the influence of <span class="hlt">convection</span> on microstructure when the MnBi fibers project out in front of the bismuth matrix; (2) search for patterns in the effect of microgravity on different eutectics (for example, eutectic composition, eutectic temperature, usual microstructure, densities of pure constituents, and density changes upon solidification); and (3) determination of the Soret coefficient and the diffusion coefficient for Mn-Bi melts near the eutectic composition, both through laboratory experiements to be performed here and from data from Shuttle experiments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008APS..DFD.MS001T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008APS..DFD.MS001T"><span>Bifurcation phenomena in cylindrical <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tuckerman, Laurette; Boronska, K.; Bordja, L.; Martin-Witkowski, L.; Navarro, M. C.</p> <p>2008-11-01</p> <p>We present two bifurcation scenarios occurring in Rayleigh-Benard <span class="hlt">convection</span> in a small-aspect-ratio cylinder. In water (Pr=6.7) with R/H=2, Hof et al. (1999) observed five <span class="hlt">convective</span> patterns at Ra=14200. We have computed 14 stable and unstable steady branches, as well as novel time-dependent branches. The resulting complicated bifurcation diagram, can be partitioned according to azimuthal symmetry. For example, three-roll and dipole states arise from an m=1 bifurcation, four-roll and ``pizza'' branches from m=2, and the ``mercedes'' state from an m=3 bifurcation after successive saddle-node bifurcations via ``marigold'', ``mitsubishi'' and ``cloverleaf'' states. The diagram represents a compromise between the physical tendency towards parallel rolls and the mathematical requirement that primary bifurcations be towards trigonometric states. Our second investigation explores the effect of exact counter-rotation of the upper and lower bounding disks on axisymmetric flows with Pr=1 and R/H=1. The <span class="hlt">convection</span> threshold increases and, for sufficiently high rotation, the instability becomes oscillatory. Limit cycles originating at the Hopf bifurcation are annihilated when their period becomes infinite at saddle-node-on-periodic-orbit (SNOPER) bifurcations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16...88E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16...88E"><span>Instability of spiral <span class="hlt">convective</span> vortex</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Evgrafova, Anna; Andrey, Sukhanovsky; Elena, Popova</p> <p>2014-05-01</p> <p>Formation of large-scale vortices in atmosphere is one of the interesting problems of geophysical fluid dynamics. Tropical cyclones are examples of atmospheric spiral vortices for which <span class="hlt">convection</span> plays an important role in their formation and evolution. Our study is focused on intensive cyclonic vortex produced by heating in the central part of the rotating layer. The previous studies made by Bogatyrev et al, showed that structure of such vortex is very similar to the structure of tropical cyclones. Qualitative observations described in (Bogatyrev, 2009) showed that the evolution of large-scale vortex in extreme regimes can be very complicated. Our main goal is the study of evolution of <span class="hlt">convective</span> cyclonic vortex at high values of Grasshof number by PIV system. Experimental setup is a rotating cylindrical tank of fluid (radius 150 mm, depth 30 mm, free upper surface). Velocity fields for different values of heat flux were obtained and temporal and spatial structure of intensive <span class="hlt">convective</span> vortex were studied in details. With the use of PIV data vorticity fields were reconstructed in different horizontal cross-sections. Physical interpretation of mechanisms that lead to the crucial change in the vortex structure with the growth of heat rate is described. Financial support from program of UD RAS, the International Research Group Program supported by Perm region Government is gratefully acknowledged.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25977064','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25977064"><span>Lipid oxidation in minced beef meat with added Krebs cycle substrates to <span class="hlt">stabilise</span> colour.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yi, G; Grabež, V; Bjelanovic, M; Slinde, E; Olsen, K; Langsrud, O; Phung, V T; Haug, A; Oostindjer, M; Egelandsdal, B</p> <p>2015-11-15</p> <p>Krebs cycle substrates (KCS) can <span class="hlt">stabilise</span> the colour of packaged meat by oxygen reduction. This study tested whether this reduction releases reactive oxygen species that may lead to lipid oxidation in minced meat under two different storage conditions. KCS combinations of succinate and glutamate increased peroxide forming potential (PFP, 1.18-1.32 mmol peroxides/kg mince) and thiobarbituric acid reactive substances (TBARS, 0.30-0.38 mg malondialdehyde (MDA) equivalents/kg mince) under low oxygen storage conditions. Both succinate and glutamate were metabolised. Moreover, under high oxygen (75%) storage conditions, KCS combinations of glutamate, citrate and malate increased PFP (from 1.22 to 1.29 mmol peroxides/kg) and TBARS (from 0.37 to 0.40 mg MDA equivalents/kg mince). Only glutamate was metabolised. The KCS combinations that were added to <span class="hlt">stabilise</span> colour were metabolised during storage, and acted as pro-oxidants that promoted lipid oxidation in both high and low oxygen conditions. Copyright © 2015. Published by Elsevier Ltd.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27072057','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27072057"><span>Accessible Mannitol-Based Amphiphiles (MNAs) for Membrane Protein Solubilisation and <span class="hlt">Stabilisation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hussain, Hazrat; Du, Yang; Scull, Nicola J; Mortensen, Jonas S; Tarrasch, Jeffrey; Bae, Hyoung Eun; Loland, Claus J; Byrne, Bernadette; Kobilka, Brian K; Chae, Pil Seok</p> <p>2016-05-17</p> <p>Integral membrane proteins are amphipathic molecules crucial for all cellular life. The structural study of these macromolecules starts with protein extraction from the native membranes, followed by purification and crystallisation. Detergents are essential tools for these processes, but detergent-solubilised membrane proteins often denature and aggregate, resulting in loss of both structure and function. In this study, a novel class of agents, designated mannitol-based amphiphiles (MNAs), were prepared and characterised for their ability to solubilise and <span class="hlt">stabilise</span> membrane proteins. Some of MNAs conferred enhanced stability to four membrane proteins including a G protein-coupled receptor (GPCR), the β2 adrenergic receptor (β2 AR), compared to both n-dodecyl-d-maltoside (DDM) and the other MNAs. These agents were also better than DDM for electron microscopy analysis of the β2 AR. The ease of preparation together with the enhanced membrane protein <span class="hlt">stabilisation</span> efficacy demonstrates the value of these agents for future membrane protein research. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25168516','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25168516"><span>Chemistry of guanidinate-<span class="hlt">stabilised</span> diboranes: transition-metal-catalysed dehydrocoupling and hydride abstraction.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wagner, Arne; Litters, Sebastian; Elias, Jana; Kaifer, Elisabeth; Himmel, Hans-Jörg</p> <p>2014-09-22</p> <p>Herein, we analyse the catalytic boron-boron dehydrocoupling reaction that leads from the base-<span class="hlt">stabilised</span> diborane(6) [H2 B(hpp)]2 (hpp=1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate) to the base-<span class="hlt">stabilised</span> diborane(4) [H2 B(hpp)]2 . A number of potential transition-metal precatalysts was studied, including transition-metal complexes of the product diborane(4). The synthesis and structural characterisation of two further examples of such complexes is presented. The best results for the dehydrocoupling reactions were obtained with precatalysts of Group 9 metals in the oxidation state of +I. The active catalyst is formed in situ through a multistep process that involves reduction of the precatalyst by the substrate [H2 B(hpp)]2 , and mechanistic investigations indicate that both heterogeneous and (slower) homogeneous reaction pathways play a role in the dehydrocoupling reaction. In addition, hydride abstraction from [H2 B(hpp)]2 and related diboranes is analysed and the possibility for subsequent deprotonation is discussed by probing the protic character of the cationic boron-hydrogen compounds with NMR spectroscopic analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26226165','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26226165"><span>A Scott bench with ergonomic thorax <span class="hlt">stabilisation</span> pad improves body posture during preacher arm curl exercise.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Biscarini, Andrea; Benvenuti, Paolo; Busti, Daniele; Zanuso, Silvano</p> <p>2016-05-01</p> <p>We assessed whether the use of an ergonomic thorax <span class="hlt">stabilisation</span> pad, during the preacher arm curl exercise, could significantly reduce the excessive shoulder protraction and thoracic kyphosis induced by the standard flat pad built into the existing preacher arm curl equipment. A 3D motion capture system and inclinometers were used to measure shoulder protraction and thoracic kyphosis in 15 subjects performing preacher arm curl with a plate-loaded machine provided with the standard flat pad. The same measures were repeated after replacing the flat pad with a new ergonomic pad, specifically designed to accommodate the thorax profile and improve body posture. Pad replacement significantly (p < 0.001) reduced shoulder protraction (from [Formula: see text] to [Formula: see text]) and thoracic kyphosis (from [Formula: see text] to [Formula: see text]), enabling postural and functional improvements within the entire spine, shoulder girdle and rib cage. The ergonomic pad may potentially allow a more effective training, prevent musculoskeletal discomfort and reduce the risk of injury. Practitioner summary: We have designed an ergonomic thorax <span class="hlt">stabilisation</span> pad for the preacher arm curl exercise. The new ergonomic pad improves the poor posture conditions induced by the standard flat pad and may potentially allow a more effective training, prevent musculoskeletal discomfort, improve the breathing function and reduce the risk of injury.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4599138','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4599138"><span>Electrical in-situ characterisation of interface <span class="hlt">stabilised</span> organic thin-film transistors</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Striedinger, Bernd; Fian, Alexander; Petritz, Andreas; Lassnig, Roman; Winkler, Adolf; Stadlober, Barbara</p> <p>2015-01-01</p> <p>We report on the electrical in-situ characterisation of organic thin film transistors under high vacuum conditions. Model devices in a bottom-gate/bottom-contact (coplanar) configuration are electrically characterised in-situ, monolayer by monolayer (ML), while the organic semiconductor (OSC) is evaporated by organic molecular beam epitaxy (OMBE). Thermal SiO2 with an optional polymer interface <span class="hlt">stabilisation</span> layer serves as the gate dielectric and pentacene is chosen as the organic semiconductor. The evolution of transistor parameters is studied on a bi-layer dielectric of a 150 nm of SiO2 and 20 nm of poly((±)endo,exo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid, diphenylester) (PNDPE) and compared to the behaviour on a pure SiO2 dielectric. The thin layer of PNDPE, which is an intrinsically photo-patternable organic dielectric, shows an excellent <span class="hlt">stabilisation</span> performance, significantly reducing the calculated interface trap density at the OSC/dielectric interface up to two orders of magnitude, and thus remarkably improving the transistor performance. PMID:26457122</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26457122','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26457122"><span>Electrical in-situ characterisation of interface <span class="hlt">stabilised</span> organic thin-film transistors.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Striedinger, Bernd; Fian, Alexander; Petritz, Andreas; Lassnig, Roman; Winkler, Adolf; Stadlober, Barbara</p> <p>2015-07-14</p> <p>We report on the electrical in-situ characterisation of organic thin film transistors under high vacuum conditions. Model devices in a bottom-gate/bottom-contact (coplanar) configuration are electrically characterised in-situ, monolayer by monolayer (ML), while the organic semiconductor (OSC) is evaporated by organic molecular beam epitaxy (OMBE). Thermal SiO2 with an optional polymer interface <span class="hlt">stabilisation</span> layer serves as the gate dielectric and pentacene is chosen as the organic semiconductor. The evolution of transistor parameters is studied on a bi-layer dielectric of a 150 nm of SiO2 and 20 nm of poly((±)endo,exo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid, diphenylester) (PNDPE) and compared to the behaviour on a pure SiO2 dielectric. The thin layer of PNDPE, which is an intrinsically photo-patternable organic dielectric, shows an excellent <span class="hlt">stabilisation</span> performance, significantly reducing the calculated interface trap density at the OSC/dielectric interface up to two orders of magnitude, and thus remarkably improving the transistor performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19666093','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19666093"><span>Physiological bicarbonate buffers: <span class="hlt">stabilisation</span> and use as dissolution media for modified release systems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fadda, Hala M; Merchant, Hamid A; Arafat, Basel T; Basit, Abdul W</p> <p>2009-12-01</p> <p>Bicarbonate media are reflective of the ionic composition and buffer capacity of small intestinal luminal fluids. Here we investigate methods to <span class="hlt">stabilise</span> bicarbonate buffers which can be readily applied to USP-II dissolution apparatus. The in vitro drug release behaviour of three enteric coated mesalazine (mesalamine) products is investigated. Asacol 400 mg and Asacol 800 mg (Asacol HD) and the new generation, high dose (1200 mg) delayed and sustained release formulation, Mezavant (Lialda), are compared in pH 7.4 Krebs bicarbonate and phosphate buffers. Bicarbonate <span class="hlt">stabilisation</span> was achieved by: continuous sparging of the medium with 5% CO(2)(g), application of a layer of liquid paraffin above the medium, or a specially designed in-house seal device that prevents CO(2)(g) loss. Each of the products displayed a delayed onset of drug release in physiological bicarbonate media compared to phosphate buffer. Moreover, Mezavant displayed a zero-order, sustained release profile in phosphate buffer; in bicarbonate media, however, this slow drug release was no longer apparent and a profile similar to that of Asacol 400 mg was observed. These similar release patterns of Asacol 400 mg and Mezavant displayed in bicarbonate media are in agreement with their pharmacokinetic profiles in humans. Bicarbonate media provide a better prediction of the in vivo behaviour of the mesalazine preparations investigated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27904359','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27904359"><span>Characterisation of Physicochemical Properties of Propionylated Corn Starch and Its Application as <span class="hlt">Stabiliser</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hong, Lee-Fen; Cheng, Lai-Hoong; Lee, Chong Yew; Peh, Kok Khiang</p> <p>2015-09-01</p> <p>A series of propionylated starches with different degrees of substitution (DS) was synthesised and their physicochemical properties and application as a <span class="hlt">stabiliser</span> were investigated. Starch propionates with moderate DS were prepared by esterification of native corn starch with propionic anhydride. By varying the reaction times of the esterification process, twelve starch propionates with DS of 0.47 to 0.94 were prepared. FTIR and NMR confirmed the introduction of propionyl groups to the starch. X-ray diffraction pattern showed reduced crystallinity in the starch propionates. The contact angle was found to increase proportionately with the increase in DS. Swelling power results showed that starch propionates were able to swell more than native corn starch at low temperature (40 °C). Oil-in- -water (O/W) emulsions prepared using starch propionates (DS of 0.64 to 0.86) showed exceptional stability when challenged by centrifugation stress test. These stable O/W emulsions had viscosities in the range of 1236.7-3330.0 mPa·s. In conclusion, moderately substituted short-chain (propionylated) starches could be a promising cold swelling starch, thickener and O/W emulsion <span class="hlt">stabiliser</span> in food, pharmaceutical and cosmetic industries.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5068383','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5068383"><span>Characterisation of Physicochemical Properties of Propionylated Corn Starch and Its Application as <span class="hlt">Stabiliser</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hong, Lee-Fen; Cheng, Lai-Hoong; Lee, Chong Yew</p> <p>2015-01-01</p> <p>Summary A series of propionylated starches with different degrees of substitution (DS) was synthesised and their physicochemical properties and application as a <span class="hlt">stabiliser</span> were investigated. Starch propionates with moderate DS were prepared by esterification of native corn starch with propionic anhydride. By varying the reaction times of the esterification process, twelve starch propionates with DS of 0.47 to 0.94 were prepared. FTIR and NMR confirmed the introduction of propionyl groups to the starch. X-ray diffraction pattern showed reduced crystallinity in the starch propionates. The contact angle was found to increase proportionately with the increase in DS. Swelling power results showed that starch propionates were able to swell more than native corn starch at low temperature (40 °C). Oil-in- -water (O/W) emulsions prepared using starch propionates (DS of 0.64 to 0.86) showed exceptional stability when challenged by centrifugation stress test. These stable O/W emulsions had viscosities in the range of 1236.7–3330.0 mPa·s. In conclusion, moderately substituted short-chain (propionylated) starches could be a promising cold swelling starch, thickener and O/W emulsion <span class="hlt">stabiliser</span> in food, pharmaceutical and cosmetic industries. PMID:27904359</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27162393','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27162393"><span>Immobilised native plant cysteine proteases: packed-bed reactor for white wine protein <span class="hlt">stabilisation</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Benucci, Ilaria; Lombardelli, Claudio; Liburdi, Katia; Acciaro, Giuseppe; Zappino, Matteo; Esti, Marco</p> <p>2016-02-01</p> <p>This research presents a feasibility study of using a continuous packed-bed reactor (PBR), containing immobilised native plant cysteine proteases, as a specific and mild alternative technique relative to the usual bentonite fining for white wine protein <span class="hlt">stabilisation</span>. The operational parameters for a PBR containing immobilised bromelain (PBR-br) or immobilised papain (PBR-pa) were optimised using model wine fortified with synthetic substrate (Bz-Phe-Val-Arg-pNA). The effectiveness of PBR-br, both in terms of hazing potential and total protein decrease, was significantly higher than PBR-pa, in all the seven unfined, white wines used. Among the wines tested, Sauvignon Blanc, given its total protein content as well as its very high intrinsic instability, was selected as a control wine to evaluate the effect of the treatment on wine as to its soluble protein profile, phenolic composition, mineral component, and sensory properties. The treatment in a PBR containing immobilised bromelain appeared effective in decreasing both wine hazing potential and total protein amount, while it did not significantly affect the phenol compounds, the mineral component nor the sensory quality of wine. The enzymatic treatment in PBR was shown to be a specific and mild technique for use as an alternative to bentonite fining for white wine protein <span class="hlt">stabilisation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24243092','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24243092"><span>Comparisons of operating envelopes for contaminated soil <span class="hlt">stabilised</span>/solidified with different cementitious binders.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kogbara, Reginald B; Al-Tabbaa, Abir; Stegemann, Julia A</p> <p>2014-03-01</p> <p>This work initiated the development of operating envelopes for <span class="hlt">stabilised</span>/solidified contaminated soils. The operating envelopes define the range of operating variables for acceptable performance of the treated soils. The study employed a soil spiked with 3,000 mg/kg each of Cd, Cu, Pb, Ni and Zn, and 10,000 mg/kg of diesel. The binders used for treatment involved Portland cement (CEMI), pulverised fuel ash (PFA), ground granulated blast furnace slag (GGBS) and hydrated lime (hlime). The specific binder formulations were CEMI, CEMI/PFA = 1:4, CEMI/GGBS = 1:9 and hlime/GGBS = 1:4. The water contents employed ranged from 13 % to 21 % (dry weight), while binder dosages ranged from 5 % to 20 % (w/w). We monitored the <span class="hlt">stabilised</span>/solidified soils for up to 84 days using different performance tests. The tests include unconfined compressive strength (UCS), hydraulic conductivity, acid neutralisation capacity (ANC) and pH-dependent leachability of contaminants. The water content range resulted in adequate workability of the mixes but had no significant effect on leachability of contaminants. We produced design charts, representing operating envelopes, from the results generated. The charts establish relationships between water content, binder dosage and UCS; and binder dosage, leachant pH and leachability of contaminants. The work also highlights the strengths and weaknesses of the different binder formulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24473316','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24473316"><span>Sludge digestion instead of aerobic <span class="hlt">stabilisation</span> - a cost benefit analysis based on experiences in Germany.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gretzschel, Oliver; Schmitt, Theo G; Hansen, Joachim; Siekmann, Klaus; Jakob, Jürgen</p> <p>2014-01-01</p> <p>As a consequence of a worldwide increase of energy costs, the efficient use of sewage sludge as a renewable energy resource must be considered, even for smaller wastewater treatment plants (WWTPs) with design capacities between 10,000 and 50,000 population equivalent (PE). To find the lower limit for an economical conversion of an aerobic <span class="hlt">stabilisation</span> plant into an anaerobic <span class="hlt">stabilisation</span> plant, we derived cost functions for specific capital costs and operating cost savings. With these tools, it is possible to evaluate if it would be promising to further investigate refitting aerobic plants into plants that produce biogas. By comparing capital costs with operation cost savings, a break-even point for process conversion could be determined. The break-even point varies depending on project specific constraints and assumptions related to future energy and operation costs and variable interest rates. A 5% increase of energy and operation costs leads to a cost efficient conversion for plants above 7,500 PE. A conversion of WWTPs results in different positive effects on energy generation and plant operations: increased efficiency, energy savings, and on-site renewable power generation by digester gas which can be used in the plant. Also, the optimisation of energy efficiency results in a reduction of primary energy consumption.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20830458','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20830458"><span>Mechanical testing of a modified <span class="hlt">stabilisation</span> method for tibial tuberosity advancement.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Etchepareborde, S; Barthelemy, N; Mills, J; Pascon, F; Ragetly, G R; Balligand, M</p> <p>2010-01-01</p> <p>This in vitro study evaluated three modified techniques of tibial tuberosity advancement (TTA). Loads to failure were calculated for each technique. A 9 mm TTA procedure was performed in the tibiae of dogs weighing between 32 and 38 kg. In group 1 (n = 12), the distal part of the tibial crest was left attached to the tibia by the cranial cortex, and a figure-of-eight wire was added for <span class="hlt">stabilisation</span>. In group 2 (n = 12), the tibial crest was left attached but no additional device was used for <span class="hlt">stabilisation</span>. In group 3 (n = 12), the tibial crest was completely separated from the tibia and fixed by a figure-of-eight wire so that, in this group, only the wire opposed avulsion of the tibial crest. Unidirectional axial force was applied via the patella to determine the maximal load to failure of the model. There was no significant difference between group 1 and group 2. These two groups both had a significantly stronger construct than that of group 3. We described modifications to the TTA procedure without plate fixation that warrant clinical investigation. When the crest is broken during its advancement, the tension sustained by the repair is significantly weaker from a biomechanical point of view and the use of such a repair clinically is not recommended by the authors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20422124','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20422124"><span>Combined intra-extra-articular technique for <span class="hlt">stabilisation</span> of coxofemoral luxation. Preliminary results in two dogs.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Venturini, A; Pinna, S; Tamburro, R</p> <p>2010-01-01</p> <p>To report a new technique for repairing traumatic cranio-dorsal coxofemoral luxation in dogs. <span class="hlt">Stabilisation</span> of hip luxation was carried out in two dogs: a one-year-old male Border Collie and an eight-year-old female American Staffordshire Bull Terrier. A caudal approach was performed to expose the hip joint. Following this, a 2.5 mm hole was drilled through the acetabular wall at the original attachment of the round ligament, followed by a tunnel between the fovea capitis and the proximal third of the femur. Nylon tape was tied in a clove hitch knot around the femoral neck. The tape was placed as a bridge over the ischial spine to create an acetabular roof in order to increase articular <span class="hlt">stabilisation</span>. Follow-up examinations were performed at 10, 40 and 90 days after surgery.The dogs did not show any signs of lameness, pain or reoccurrence of the luxation during any of the follow-up examinations. This tape-technique enabled reinforcement of the acetabular roof which in turn increased the stability of the joint.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014VSD....52.1607A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014VSD....52.1607A"><span>Integration of vehicle yaw <span class="hlt">stabilisation</span> and rollover prevention through nonlinear hierarchical control allocation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Alberding, Matthäus B.; Tjønnås, Johannes; Johansen, Tor A.</p> <p>2014-12-01</p> <p>This work presents an approach to rollover prevention that takes advantage of the modular structure and optimisation properties of the control allocation paradigm. It eliminates the need for a <span class="hlt">stabilising</span> roll controller by introducing rollover prevention as a constraint on the control allocation problem. The major advantage of this approach is the control authority margin that remains with a high-level controller even during interventions for rollover prevention. In this work, the high-level control is assigned to a yaw <span class="hlt">stabilising</span> controller. It could be replaced by any other controller. The constraint for rollover prevention could be replaced by or extended to different control objectives. This work uses differential braking for actuation. The use of additional or different actuators is possible. The developed control algorithm is computationally efficient and suitable for low-cost automotive electronic control units. The predictive design of the rollover prevention constraint does not require any sensor equipment in addition to the yaw controller. The method is validated using an industrial multi-body vehicle simulation environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27821333','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27821333"><span>Double oil-in-oil-in-oil emulsions <span class="hlt">stabilised</span> solely by particles.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tyowua, Andrew T; Yiase, Stephen G; Binks, Bernard P</p> <p>2017-02-15</p> <p>The stability of vegetable oil-in-100cS silicone oil-in-vegetable oil V/S/V emulsions to sedimentation and coalescence has been studied. The emulsions contained two types of silica particle of different surface silanol content, 70% and 20% SiOH, which prefer to <span class="hlt">stabilise</span> 100cS silicone oil-in-vegetable oil S/V and vegetable oil-in-100cS silicone oil V/S emulsions respectively, in systems containing equal proportion of the oils. The emulsions were prepared in a two-step process and were characterised using the drop test and optical microscopy. The emulsions were completely stable to coalescence for over a month. However, they underwent sedimentation which decreases as the concentration of 70% SiOH silica particles <span class="hlt">stabilising</span> the silicone oil globules increases. The gravity-induced sedimentation halted at a relatively high particle concentration (2wt.%) and negligible amount of the vegetable oils was released even after a month. Their average droplet diameter also decreases as the concentration of 70% SiOH silica particles increases. Values of oil-oil-solid particle contact angles θoo, measured on microscope glass slides composed of the particles, are in good agreement with the type of simple emulsions and hence double emulsions formed by the particles. Crown Copyright © 2016. Published by Elsevier Inc. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18204252','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18204252"><span>Enamel subsurface lesion remineralisation with casein phosphopeptide <span class="hlt">stabilised</span> solutions of calcium, phosphate and fluoride.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Cochrane, N J; Saranathan, S; Cai, F; Cross, K J; Reynolds, E C</p> <p>2008-01-01</p> <p>Casein phosphopeptide <span class="hlt">stabilised</span> amorphous calcium phosphate (CPP-ACP) and amorphous calcium fluoride phosphate (CPP-ACFP) solutions have been shown to remineralise enamel subsurface lesions. The aim of this study was to determine the effect of ion composition of CPP-ACP and CPP-ACFP solutions on enamel subsurface lesion remineralisation in vitro. CPP-bound and free calcium, phosphate and fluoride ion concentrations in the solutions were determined after ultrafiltration. The ion activities of the free ion species present were calculated using an iterative computational program. The mineral deposited in the subsurface lesions was analysed using transverse microradiography and electron microprobe. CPP was found to <span class="hlt">stabilise</span> high concentrations of calcium, phosphate and fluoride ions at all pH values (7.0-4.5). Remineralisation of the subsurface lesions was observed at all pH values tested with a maximum at pH 5.5. The CPP-ACFP solutions produced greater remineralisation than the CPP-ACP solutions at pH 5.5 and below. The mineral formed in the subsurface lesions was consistent with hydroxyapatite and fluorapatite for remineralisation with CPP-ACP and CPP-ACFP, respectively. The activity gradient of the neutral ion pair CaHPO(4)(0) into the lesion was significantly correlated with remineralisation and together with HF(0) were identified as important species for diffusion.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6925390','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6925390"><span><span class="hlt">Background</span> sources at PEP</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lynch, H.; Schwitters, R.F.; Toner, W.T.</p> <p>1988-01-01</p> <p>Important sources of <span class="hlt">background</span> for PEP experiments are studied. <span class="hlt">Background</span> particles originate from high-energy electrons and positrons which have been lost from stable orbits, ..gamma..-rays emitted by the primary beams through bremsstrahlung in the residual gas, and synchrotron radiation x-rays. The effect of these processes on the beam lifetime are calculated and estimates of <span class="hlt">background</span> rates at the interaction region are given. Recommendations for the PEP design, aimed at minimizing <span class="hlt">background</span> are presented. 7 figs., 4 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26812009','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26812009"><span>The effect of environmental conditions and soil physicochemistry on phosphate <span class="hlt">stabilisation</span> of Pb in shooting range soils.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sanderson, Peter; Naidu, Ravi; Bolan, Nanthi</p> <p>2016-04-01</p> <p>The <span class="hlt">stabilisation</span> of Pb in the soil by phosphate is influenced by environmental conditions and physicochemical properties of the soils to which it is applied. <span class="hlt">Stabilisation</span> of Pb by phosphate was examined in four soils under different environmental conditions. The effect of soil moisture and temperature on <span class="hlt">stabilisation</span> of Pb by phosphate was examined by measurement of water extractable and bioaccessible Pb, sequential fractionation and X-ray absorption spectroscopy. The addition of humic acid, ammonium nitrate and chloride was also examined for inhibition or improvement of Pb stability with phosphate treatment. The effect of moisture level varied between soils. In soil MB and DA a soil moisture level of 50% water holding capacity was sufficient to maximise <span class="hlt">stabilisation</span> of Pb, but in soil TV and PE reduction in bioaccessible Pb was inhibited at this moisture level. Providing moisture at twice the soil water holding capacity did not enhance the effect of phosphate on Pb <span class="hlt">stabilisation</span>. The difference of Pb stability as a result of incubating phosphate treated soils at 18 °C and 37 °C was relatively small. However wet-dry cycles decreased the effectiveness of phosphate treatment. The reduction in bioaccessible Pb obtained was between 20 and 40% with the most optimal treatment conditions. The reduction in water extractable Pb by phosphate was substantial regardless of incubation conditions and the effect of different temperature and soil moisture regimes was not significant. Selective sequential extraction showed phosphate treatment converted Pb in fraction 1 (exchangeable, acid and water soluble) to fraction 2 (reducible). There were small difference in fraction 4 (residual) Pb and fraction 1 as a result of treatment conditions. X-ray absorption spectroscopy of <span class="hlt">stabilised</span> PE soil revealed small differences in Pb speciation under varying soil moisture and temperature treatments. The addition of humic acid and chloride produced the greatest effect on Pb speciation in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.4546G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.4546G"><span>The use of biogas plant fermentation residue for the <span class="hlt">stabilisation</span> of toxic metals in agricultural soils</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Geršl, Milan; Šotnar, Martin; Mareček, Jan; Vítěz, Tomáš; Koutný, Tomáš; Kleinová, Jana</p> <p>2015-04-01</p> <p>Our department has been paying attention to different methods of soil decontamination, including the in situ <span class="hlt">stabilisation</span>. Possible reagents to control the toxic metals mobility in soils include a fermentation residue (FR) from a biogas plant. Referred to as digestate, it is a product of anaerobic decomposition taking place in such facilities. The fermentation residue is applied to soils as a fertiliser. A new way of its use is the in situ <span class="hlt">stabilisation</span> of toxic metals in soils. Testing the <span class="hlt">stabilisation</span> of toxic metals made use of real soil samples sourced from five agriculturally used areas of the Czech Republic with 3 soil samples taken from sites contaminated with Cu, Pb and Zn and 2 samples collected at sites of natural occurrence of Cu, Pb and Zn ores. All the samples were analysed using the sequential extraction procedure (BCR) (determine the type of Cu, Pb and Zn bonds). <span class="hlt">Stabilisation</span> of toxic metals was tested in five soil samples by adding reagents as follows: dolomite, slaked lime, goethite, compost and fermentation residue. A single reagent was added at three different concentrations. In the wet state with the added reagents, the samples were left for seven days, shaken twice per day. After seven days, metal extraction was carried out: samples of 10 g soil were shaken for 2 h in a solution of 0.1M NH4NO3 at a 1:2.5 (g.ml-1), centrifuged for 15 min at 5,000 rpm and then filtered through PTFE 0.45 μm mesh filters. The extracts were analysed by ICP-OES. Copper The best reduction of Cu concentration in the extract was obtained at each of the tested sites by adding dolomite (10 g soil + 0.3 g dolomite). The concentration of Cu in the leachate decreased to 2.1-18.4% compare with the leachate without addition. Similar results were also shown for the addition of fermentation residue (10 g soil + 1 g FR). The Cu concentration in the leachate decreased to 16.7-26.8% compared with the leachate without addition. Lead The best results were achieved by adding</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1378730','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1378730"><span>Impact of topography on the diurnal cycle of summertime moist <span class="hlt">convection</span> in idealized simulations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Hassanzadeh, Hanieh; Schmidli, Jürg; Langhans, Wolfgang; Schlemmer, Linda; Schär, Christoph</p> <p>2015-08-31</p> <p>The impact of an isolated mesoscale mountain on the diurnal cycle of moist <span class="hlt">convection</span> and its spatial variation is investigated. <span class="hlt">Convection</span>-resolving simulations of flow over 3D Gaussian-shaped mountains are performed for a conditionally unstable atmosphere under diurnal radiative forcing. The results show considerable spatial variability in terms of timing and amount of <span class="hlt">convective</span> precipitation. This variability relates to different physical mechanisms responsible for <span class="hlt">convection</span> initiation in different parts of the domain. During the late morning, the mass convergence from the radiatively driven diurnal upslope flow confronting the large-scale incident <span class="hlt">background</span> flow triggers strong <span class="hlt">convective</span> precipitation over the mountain lee slope. As a consequence, instabilities in the boundary layer are swept out by the emerging cold pool in the vicinity of the mountain, and some parts over the mountain near-field receive less rainfall than the far-field. Over the latter, an unperturbed boundary-layer growth allows for sporadic <span class="hlt">convective</span> initiation. Still, secondary <span class="hlt">convection</span> triggered over the leading edge of the cold pool spreads some precipitation over the downstream near-field. Detailed analysis of our control simulation provides further explanation of this frequently observed precipitation pattern over mountains and adjacent plains. Sensitivity experiments indicate a significant influence of the mountain height on the precipitation pattern over the domain.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1378730-impact-topography-diurnal-cycle-summertime-moist-convection-idealized-simulations','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1378730-impact-topography-diurnal-cycle-summertime-moist-convection-idealized-simulations"><span>Impact of topography on the diurnal cycle of summertime moist <span class="hlt">convection</span> in idealized simulations</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Hassanzadeh, Hanieh; Schmidli, Jürg; Langhans, Wolfgang; ...</p> <p>2015-08-31</p> <p>The impact of an isolated mesoscale mountain on the diurnal cycle of moist <span class="hlt">convection</span> and its spatial variation is investigated. <span class="hlt">Convection</span>-resolving simulations of flow over 3D Gaussian-shaped mountains are performed for a conditionally unstable atmosphere under diurnal radiative forcing. The results show considerable spatial variability in terms of timing and amount of <span class="hlt">convective</span> precipitation. This variability relates to different physical mechanisms responsible for <span class="hlt">convection</span> initiation in different parts of the domain. During the late morning, the mass convergence from the radiatively driven diurnal upslope flow confronting the large-scale incident <span class="hlt">background</span> flow triggers strong <span class="hlt">convective</span> precipitation over the mountain lee slope.more » As a consequence, instabilities in the boundary layer are swept out by the emerging cold pool in the vicinity of the mountain, and some parts over the mountain near-field receive less rainfall than the far-field. Over the latter, an unperturbed boundary-layer growth allows for sporadic <span class="hlt">convective</span> initiation. Still, secondary <span class="hlt">convection</span> triggered over the leading edge of the cold pool spreads some precipitation over the downstream near-field. Detailed analysis of our control simulation provides further explanation of this frequently observed precipitation pattern over mountains and adjacent plains. Sensitivity experiments indicate a significant influence of the mountain height on the precipitation pattern over the domain.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMNG13A..07C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMNG13A..07C"><span>Compressible Quasi-geostrophic <span class="hlt">Convection</span> without the Anelastic Approximation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Calkins, M. A.; Marti, P.; Julien, K. A.</p> <p>2014-12-01</p> <p>Fluid compressibility is known to be an important, non-negligible component of the dynamics of many planetary atmospheres and stellar <span class="hlt">convection</span> zones, yet imposes severe computational constraints on numerical simulations of the compressible Navier-Stokes equations (NSE). An often employed reduced form of the NSE are the anelastic equations, which maintain fluid compressibility in the form of a depth varying, adiabatic <span class="hlt">background</span> state onto which the perturbations cannot feed back. We present the linear theory of compressible rotating <span class="hlt">convection</span> in a local-area, plane layer geometry. An important dimensionless parameter in <span class="hlt">convection</span> is the ratio of kinematic viscosity to thermal diffusivity, or the Prandtl number, Pr. It is shown that the anelastic approximation cannot capture the linear instability of gases with Prandtl numbers less than approximately 0.5 in the limit of rapid rotation; the time derivative of the density fluctuation appearing in the conservation of mass equation remains important for these cases and cannot be neglected. An alternative compressible, geostrophically balanced equation set has been derived and preliminary results utilizing this new equation set are presented. Notably, this new set of equations satisfies the Proudman-Taylor theorem on small axial scales even for strongly compressible flows, does not require the flow to be nearly adiabatic, and thus allows for feedback onto the <span class="hlt">background</span> state.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017MAP...tmp...66U','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017MAP...tmp...66U"><span>Do the stability indices indicate the formation of deep <span class="hlt">convection</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Uma, K. N.; Das, S. K.</p> <p>2017-09-01</p> <p>The present study investigates the relation between the stability indices and different types of precipitating clouds during the active and the suppressed periods of deep <span class="hlt">convection</span> of the Madden-Julian oscillation. This is achieved by utilizing three-hourly radiosonde (RS92) data and merged cloud radar data over the Gan Island (0.69°S, 73.15°E) from October 2011 to January, 2012. The active and the suppressed periods are defined based on the rainfall. Three periods of active (15-27 October, 15-28 November and 15-27 December) and suppressed periods (01-14 November, 0-14 December and 01-14 January) are identified. During the above periods, the stability indices are calculated to distinguish the <span class="hlt">background</span> meteorological conditions. The analysis shows that during both the active and the suppressed periods, the magnitude of the stability indices are not much different. During both the periods, the indices attain their respective threshold corresponding to the occurrence of deep <span class="hlt">convection</span>. However, the third suppressed period shows a dry condition compared to the other two suppressed periods. The relation between the stability indices and the precipitating cloud categories (shallow, congestus and deep) indicate that even though the threshold in the stability indices were attained, deep <span class="hlt">convective</span> clouds were not observed during the suppressed periods. The active period correlates well with the stability indices. Therefore, the stability indices do not clearly and directly determine the state of the atmosphere during deep <span class="hlt">convection</span>. The result shows stability indices need to be substantially improved in the context of deep <span class="hlt">convection</span> prediction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMSA11C3956K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMSA11C3956K"><span>Evidence for Gravity Wave Seeding of <span class="hlt">Convective</span> Ionosphere Storms Initiated by Deep Troposphere <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kelley, M. C.; Pfaff, R. F., Jr.; Dao, E. V.; Holzworth, R. H., II</p> <p>2014-12-01</p> <p>With the increase in solar activity, the Communications/Outage Forecast System satellite (C/NOFS) now goes below the F peak. As such, we now can study the development of <span class="hlt">Convective</span> Ionospheric Storms (CIS) and, most importantly, large-scale seeding of the low growth-rate Rayleigh-Taylor (R-T) instability. Two mechanisms have been suggested for such seeding: the Collisional Kelvin-Helmholtz Instability (CKHI) and internal atmospheric gravity waves. A number of observations have shown that the spectrum of fully developed topside structures peaks at 600 km and extends to over 1000 km. These structures are exceedingly difficult to explain by CKHI. Here we show that sinusoidal plasma oscillations on the bottomside during daytime develop classical R-T structures on the nightside with the <span class="hlt">background</span> 600 km structure still apparent. In two case studies, thunderstorm activity was observed east of the sinusoidal features in the two hours preceding the C/NOFS passes. Thus, we argue that <span class="hlt">convective</span> tropospheric storms are a likely source of these sinusoidal features.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011IJSyS..42.1975T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011IJSyS..42.1975T"><span>An improved stability test and <span class="hlt">stabilisation</span> of linear time-varying systems governed by second-order vector differential equations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tung, Shen-Lung; Juang, Yau-Tarng; Wu, Wei-Ying; Shieh, Wern-Yarng</p> <p>2011-12-01</p> <p>In this article, the problems of exponential stability analysis and <span class="hlt">stabilisation</span> of linear time-varying systems described by a class of second-order vector differential equations are considered. Using bounding techniques on the trajectories of a linear time-varying system, the stability problem of the time-varying system is transformed to that of a time-invariant system and a new sufficient condition for the exponential stability is obtained. Moreover, the new criterion is proven to be superior to a test presented in the recent literature. Finally, the proposed criterion is applied to the exponential <span class="hlt">stabilisation</span> problem via state feedback. The results are illustrated by several numerical examples.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A41F0119I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A41F0119I"><span>On the Sensitivity of the Diurnal Cycle in the Amazon to <span class="hlt">Convective</span> Intensity</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Itterly, K. F.; Taylor, P. C.</p> <p>2015-12-01</p> <p>The sensitivity of the diurnal cycle to <span class="hlt">convective</span> intensity is investigated for the wet season (DJF) and dry season (JJA) in the Amazon region. Model output reveals large water and energy budget errors in tropical rainforests, arising from a misrepresentation of the diurnal cycle of the complex processes inherent to diurnally forced moist <span class="hlt">convection</span>. Daily, 3-hourly satellite observations of CERES Ed3a SYN1DEG TOA fluxes and 3-hourly TRMM 3B42 precipitation rate from 2002-2012 are split into regimes of <span class="hlt">convective</span> intensity using percentile definitions for both daily minimum OLR and daily maximum precipitation rate to define regimes. These satellite-defined regimes are then co-located with <span class="hlt">convective</span> parameters calculated from radiosonde observations. Diurnal statistics from satellite include: phase, amplitude, precipitation onset, precipitation duration and diurnal mean. The diurnal phase of outgoing longwave radiation (OLR) and longwave cloud forcing (LWCF) occurs several hours earlier on <span class="hlt">convective</span> days compared to stable days, however, climatological precipitation phase is less sensitive to <span class="hlt">convective</span> intensity, occurring between 1-4PM local time for all regimes and 1-2 hours later on very <span class="hlt">convective</span> days, which is related to longer duration precipitation events from increased humidity. Diurnal <span class="hlt">convection</span> in the Amazon is strongly related to 8AM values of both dynamic and thermodynamic variables, most of which are related to: the <span class="hlt">background</span> moisture content of the troposphere, the stability of the lower troposphere, <span class="hlt">convective</span> inhibition (CIN) and wind speed and direction in the column. Morning values of CIN, lifted condensation level (LCL), level of free <span class="hlt">convection</span> (LFC) and equilibrium level (EL) are lower in DJF than JJA, and lower on very <span class="hlt">convective</span> days than stable days for all stations. Higher <span class="hlt">background</span> humidity is related to longer duration precipitation events (r-values between 0.4-0.6, depending on station and season), earlier phases and onset times</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvF...1e4301Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvF...1e4301Z"><span>Statistical characterization of thermal plumes in turbulent thermal <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Sheng-Qi; Xie, Yi-Chao; Sun, Chao; Xia, Ke-Qing</p> <p>2016-09-01</p> <p>We report an experimental study on the statistical properties of the thermal plumes in turbulent thermal <span class="hlt">convection</span>. A method has been proposed to extract the basic characteristics of thermal plumes from temporal temperature measurement inside the <span class="hlt">convection</span> cell. It has been found that both plume amplitude A and cap width w , in a time domain, are approximately in the log-normal distribution. In particular, the normalized most probable front width is found to be a characteristic scale of thermal plumes, which is much larger than the thermal boundary layer thickness. Over a wide range of the Rayleigh number, the statistical characterizations of the thermal fluctuations of plumes, and the turbulent <span class="hlt">background</span>, the plume front width and plume spacing have been discussed and compared with the theoretical predictions and morphological observations. For the most part good agreements have been found with the direct observations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800002734','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800002734"><span>Stellar <span class="hlt">convection</span> 3: <span class="hlt">Convection</span> at large Rayleigh numbers</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Marcus, P. S.</p> <p>1979-01-01</p> <p>A three dimensional study of <span class="hlt">convection</span> in a self gravitating sphere of Boussinesq fluid with a Rayleigh number of 10 to the 10th power and a Prandtl of 1 is presented. The velocity and temperature of the fluid are computed at the largest wavelengths using spectral methods. A confirmation that the fluid is anisotropic and that the energy spectra are not smooth functions of wavelength but have a large amount of fine structure is discussed. The parameterization of the transport properties of the unresolvable inertial subrange with eddy viscosities and diffusivities is described. The time dependent fluctuations in the energy spectra and how they cascade from large to small wavelengths is examined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017SPD....4840305B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017SPD....4840305B"><span><span class="hlt">Convective</span> overshoot at the solar tachocline</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, Benjamin; Oishi, Jeffrey S.; Anders, Evan H.; Lecoanet, Daniel; Burns, Keaton; Vasil, Geoffrey M.</p> <p>2017-08-01</p> <p>At the base of the solar <span class="hlt">convection</span> zone lies the solar tachocline. This internal interface is where motions from the unstable <span class="hlt">convection</span> zone above overshoot and penetrate downward into the stiffly stable radiative zone below, driving gravity waves, mixing, and possibly pumping and storing magnetic fields. Here we study the dynamics of <span class="hlt">convective</span> overshoot across very stiff interfaces with some properties similar to the internal boundary layer within the Sun. We use the Dedalus pseudospectral framework and study fully compressible dynamics at moderate to high Peclet number and low Mach number, probing a regime where turbulent transport is important, and where the compressible dynamics are similar to those of <span class="hlt">convective</span> motions in the deep solar interior. We find that the depth of <span class="hlt">convective</span> overshoot is well described by a simple buoyancy equilibration model, and we consider implications for dynamics at the solar tachocline and for the storage of magnetic fields there by overshooting <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJSyS..47.1543Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJSyS..47.1543Z"><span>Finite-time observer-based output-feedback control for the global <span class="hlt">stabilisation</span> of the PVTOL aircraft with bounded inputs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zavala-Río, A.; Fantoni, I.; Sanahuja, G.</p> <p>2016-05-01</p> <p>In this work, an output-feedback scheme for the global <span class="hlt">stabilisation</span> of the planar vertical take-off and landing aircraft with bounded inputs is developed taking into account the positive nature of the thrust. The global <span class="hlt">stabilisation</span> objective is proven to be achieved avoiding input saturation and by exclusively considering the system positions in the feedback. To cope with the lack of velocity measurements, the proposed algorithm involves a finite-time observer. The generalised versions of the involved finite-time <span class="hlt">stabilisers</span> have not only permitted to solve the output-feedback <span class="hlt">stabilisation</span> problem avoiding input saturation, but also provide additional flexibility in the control design that may be used in aid of performance improvements. With respect to previous approaches, the developed finite-time observer-based scheme guarantees the global <span class="hlt">stabilisation</span> objective disregarding velocity measurements in a bounded input context. Simulation tests corroborate the analytical developments. The study includes further experimental results on an actual flying device.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA108095','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA108095"><span><span class="hlt">Convective</span> Heat Transfer for Ship Propulsion.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p>1981-04-01</p> <p>OF RILJORT 6 PelIOO COVERED <span class="hlt">Convective</span> Heat Transfer for Ship Propulsion . Annual gummary Report / (Sixth Annual Sumary Report) //115 Jan 180-30 Mard...DO* IrCOVE) Sixth Annual Summary Report <span class="hlt">CONVECTIVE</span> HEAT TRANSFER FOR SHIP PROPULSION By M. A. Habib and D. M. McEligot Aerospace and Mechanical...permitted for any purpose of the United States Government. ._ _ _ _ _ _ I <span class="hlt">CONVECTIVE</span> HEAT TRANSFER FOR SHIP PROPULSION M. A. Habib* and D. M. McEligot</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19800040133&hterms=conduction+convection&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dconduction%2Bconvection','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19800040133&hterms=conduction+convection&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dconduction%2Bconvection"><span>Application of upwind <span class="hlt">convective</span> finite elements to practical conduction/forced <span class="hlt">convection</span> thermal analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thornton, E. A.</p> <p>1979-01-01</p> <p>Three practical problems in conduction/forced <span class="hlt">convection</span> heat transfer are analyzed using a simplified engineering formulation of <span class="hlt">convective</span> finite elements. Upwind and conventional finite element solutions are compared for steady-state and transient applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017EGUGA..19.7531M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017EGUGA..19.7531M"><span>Organomineral interactions as an important mechanism for <span class="hlt">stabilisation</span> of bacterial residues in soil</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Miltner, Anja; Achtenhagen, Jan; Kästner, Matthias</p> <p>2017-04-01</p> <p>Although plant material is the original input of organic matter to soils, microbial residues have been identified to contribute to a large extent to soil organic matter. However, until now it is unclear how microbial residues are <span class="hlt">stabilised</span> in soil and protected from degradation. We hypothesised that organomineral interactions, in particular encrustation by oxides, may play an important role, which might vary depending on environmental conditions, e.g. redox potential. Therefore we produced 14C-labelled Escherichia coli cells and cell envelope fragments and coprecipitated these materials with Fe oxide or Al oxide. Mineral-free (control) and mineral-encrusted bacterial residues were incubated for 345 days at 20˚ C under either oxic or oxygen-limited conditions, and mineralisation was quantified by scintillation counting of the CO2 produced during incubation. Oxygen limitation was achieved by first exchanging the atmosphere in the incubation vessels with dinitrogen gas. After 100 days of incubation, the anoxic treatments were waterlogged to further decrease the redox potential, and after 290 days, glucose and nutrients were supplied to all treatments in order to foster microbial activity and consumption of electron acceptors. The mineralisation curves were fitted by double-exponential (0-100 days), first-order kinetic (100-290 days) and linear (290-345 days) models. The model parameters were tested for significant differences between the treatments by three-way ANOVA with post-hoc Bonferroni t-test. We found that encrustation by the oxides significantly reduced mineralisation of the bacterial residues. This effect was inversed by reductive dissolution of Fe oxides after substrate and nutrient addition to the oxygen-limited treatments, suggesting a significant role of the encrustation in <span class="hlt">stabilisation</span> of the bacterial residues. We also observed that bacterial cell envelope fragments were generally slightly more resistant to mineralisation than whole cells. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006PhDT........46L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006PhDT........46L"><span><span class="hlt">Stabilisation</span> de poussieres de four a arc electrique dans les matrices cimentaires</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Laforest, Guylaine</p> <p></p> <p>L'etude de la <span class="hlt">stabilisation</span> des poussieres de four a arc electrique (EAFD) par le laitier de haut-fourneau (GGBFS) et le ciment Portland (OPC) a ete realisee en trois parties. D'abord, la problematique de fixation du Cr dans les matrices cimentaires a ete etudiee en soumettant differents liants a des solutions de Cr lors d'essais de lixiviation en vrac et d'essais d'isothermes d'absorption. Ensuite, la caracterisation des EAFD a ete effectuee. Finalement, la <span class="hlt">stabilisation</span> des EAFD dans les matrices cimentaires a ete etudiee en soumettant differents melanges liant-EAFD a des essais de lixiviation en vrac, de competition ionique, de solubilisation a differents pH et de lixiviation sur monolithes. Les resultats ont demontre que le OPC et le GGBFS sont efficaces pour la fixation du Cr. Les silicates de calcium hydrates, la chromatite et l'hydrocalumite ont ete identifiees comme etant des phases jouant un role dans la fixation du Cr. Les EAFD ont montre une mineralogie complexe, heterogene, riche en spinelles et oxydes metalliques. Un important pourcentage des metaux lourds (Cr, Zn, Ni et Pb) des EAFD a ete identifie lixiviable. Les EAFD etablissent un controle de solubilite sur ces metaux, mais ce controle n'est pas suffisant pour diminuer les concentrations en metaux du lixiviat sous les limites permises. Ainsi, les resulats des essais sur la <span class="hlt">stabilisation</span> des EAFD ont demontre qu'il etait possible, avec le OPC et le GGBFS, de diminuer les concentrations en metaux lourds des lixiviats sous les limites acceptees. Les phases incorporant les metaux, ((Ni,Zn)Fe2O4, (Zn,Mo)O, Ni(OH)2 et Pb(OH) 2), ont ete determinees par SEM, XRD et par modelisation geochimique. L'hydrocalumite et le Cr(VI)-ettringite ont ete etablies comme etant des phases potentiellement capables de fixer le Cr. L'etude de la competition ionique a montre que la fixation du Cr par le GGBFS diminue legerement en presence du Pb. L'etude des monolithes, composes de EAFD et de OPC ou GGBFS et soumis a une</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28343049','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28343049"><span><span class="hlt">Stabilisation</span> of spent mushroom substrate for application as a plant growth-promoting organic amendment.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Paula, Fabiana S; Tatti, Enrico; Abram, Florence; Wilson, Jude; O'Flaherty, Vincent</p> <p>2017-07-01</p> <p>Over three million tonnes of spent mushroom substrate (SMS) are produced in Europe every year as a by-product of the cultivation of Agaricus bisporus. The management of SMS has become an increasing challenge for the mushroom production industry, and finding environmentally and economically sustainable solutions for this organic residue is, therefore, highly desirable. Due to its physical properties and nutrient content, SMS has great potential to be employed in agricultural and horticultural sectors, and further contribute to reduce the use of non-renewable resources, such as peat. However, SMS is often regarded as not being stable and/or mature, which hampers its wide use for crop production. Here, we demonstrate the <span class="hlt">stabilisation</span> of SMS and its subsequent use as organic fertiliser and partial peat replacement in horticulture. The <span class="hlt">stabilisation</span> was performed in a laboratory-scale composting system, with controlled temperature and aeration. Physical and chemical parameters were monitored during composting and provided information on the progress of the process. Water soluble carbohydrates (WSC) content was found to be the most reliable parameter to predict SMS stability. In situ oxygen consumption indicated the main composting phases, reflecting major changes in microbial activity. The structure of the bacterial community was also found to be a potential predictor of stability, as the compositional changes followed the composting progress. By contrast, the fungal community did not present clear successional process along the experiment. Maturity and quality of the <span class="hlt">stabilised</span> SMS were assessed in a horticultural growing trial. When used as the sole fertiliser source, SMS was able to support Lolium multiflorum (Italian ryegrass) growth and significantly improved grass yield with a concentration-dependent response, increasing grass biomass up to 300%, when compared to the untreated control. In summary, the results indicated that the method employed was efficient in</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25461062','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25461062"><span>Freshwater dispersion stability of PAA-<span class="hlt">stabilised</span> cerium oxide nanoparticles and toxicity towards Pseudokirchneriella subcapitata.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Booth, Andy; Størseth, Trond; Altin, Dag; Fornara, Andrea; Ahniyaz, Anwar; Jungnickel, Harald; Laux, Peter; Luch, Andreas; Sørensen, Lisbet</p> <p>2015-02-01</p> <p>An aqueous dispersion of poly (acrylic acid)-<span class="hlt">stabilised</span> cerium oxide (CeO₂) nanoparticles (PAA-CeO₂) was evaluated for its stability in a range of freshwater ecotoxicity media (MHRW, TG 201 and M7), with and without natural organic matter (NOM). In a 15 day dispersion stability study, PAA-CeO₂ did not undergo significant aggregation in any media type. Zeta potential varied between media types and was influenced by PAA-CeO₂ concentration, but remained constant over 15 days. NOM had no influence on PAA-CeO₂ aggregation or zeta potential. The ecotoxicity of the PAA-CeO₂ dispersion was investigated in 72 h algal growth inhibition tests using the freshwater microalgae Pseudokirchneriella subcapitata. PAA-CeO₂ EC₅₀ values for growth inhibition (GI; 0.024 mg/L) were 2-3 orders of magnitude lower than pristine CeO₂ EC₅₀ values reported in the literature. The concentration of dissolved cerium (Ce(3+)/Ce(4+)) in PAA-CeO₂ exposure suspensions was very low, ranging between 0.5 and 5.6 μg/L. Free PAA concentration in the exposure solutions (0.0096-0.0384 mg/L) was significantly lower than the EC10 growth inhibition (47.7 mg/L) value of pure PAA, indicating that free PAA did not contribute to the observed toxicity. Elemental analysis indicated that up to 38% of the total Cerium becomes directly associated with the algal cells during the 72 h exposure. TOF-SIMS analysis of algal cell wall compounds indicated three different modes of action, including a significant oxidative stress response to PAA-CeO₂ exposure. In contrast to pristine CeO₂ nanoparticles, which rapidly aggregate in standard ecotoxicity media, PAA-<span class="hlt">stabilised</span> CeO₂ nanoparticles remain dispersed and available to water column species. Interaction of PAA with cell wall components, which could be responsible for the observed biomarker alterations, could not be excluded. This study indicates that the increased dispersion stability of PAA-CeO₂ leads to an increase in toxicity compared to</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950052929&hterms=william+thompson&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dwilliam%2Bthompson','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950052929&hterms=william+thompson&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dwilliam%2Bthompson"><span><span class="hlt">Convective</span> transport over the central United States and its role in regional CO and ozone budgets</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thompson, Anne M.; Pickering, Kenneth E.; Dickerson, Russell R.; Ellis, William G., Jr.; Jacob, Daniel J.; Scala, John R.; Tao, Wei-Kuo; Mcnamara, Donna P.; Simpson, Joanne</p> <p>1994-01-01</p> <p>We have constructed a regional budget for boundary layer carbon monoxide over the central United States (32.5 deg - 50 deg N, 90 deg - 105 deg W), emphasizing a detailed evaluation of deep <span class="hlt">convective</span> vertical fluxes appropriate for the month of June. Deep <span class="hlt">convective</span> venting of the boundary layer (upward) dominates other components of the CO budget, e.g., downward <span class="hlt">convective</span> transport, loss of CO by oxidation, anthropogenic emissions, and CO produced from oxidation of methane, isoprene, and anthropogenic nonmethane hydrocarbons (NMHCs). Calculations of deep <span class="hlt">convective</span> venting are based on the method pf Pickering et al.(1992a) which uses a satellite-derived deep <span class="hlt">convective</span> cloud climatology along with transport statistics from <span class="hlt">convective</span> cloud model simulations of observed prototype squall line events. This study uses analyses of <span class="hlt">convective</span> episodes in 1985 and 1989 and CO measurements taken during several midwestern field campaigns. Deep <span class="hlt">convective</span> venting of the boundary layer over this moderately polluted region provides a net (upward minus downward) flux of 18.1 x 10(exp 8) kg CO/month to the free troposphere during early summer. Shallow cumulus and synoptic-scale weather systems together make a comparable contribution (total net flux 16.2 x 10(exp 8) kg CO/month). Boundary layer venting of CO with other O3 precursors leads to efficient free troposheric O3 formation. We estimate that deep <span class="hlt">convective</span> transport of CO and other precursors over the central United States in early summer leads to a gross production of 0.66 - 1.1 Gmol O3/d in good agreement with estimates of O3 production from boundary layer venting in a continental-scale model (Jacob et al., 1993a, b). On this respect the central U.S. region acts as s `chimney' for the country, and presumably this O3 contributes to high <span class="hlt">background</span> levels of O3 in the eastern United States and O3 export to the North Atlantic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950052929&hterms=polluted+countries&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dpolluted%2Bcountries','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950052929&hterms=polluted+countries&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dpolluted%2Bcountries"><span><span class="hlt">Convective</span> transport over the central United States and its role in regional CO and ozone budgets</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thompson, Anne M.; Pickering, Kenneth E.; Dickerson, Russell R.; Ellis, William G., Jr.; Jacob, Daniel J.; Scala, John R.; Tao, Wei-Kuo; Mcnamara, Donna P.; Simpson, Joanne</p> <p>1994-01-01</p> <p>We have constructed a regional budget for boundary layer carbon monoxide over the central United States (32.5 deg - 50 deg N, 90 deg - 105 deg W), emphasizing a detailed evaluation of deep <span class="hlt">convective</span> vertical fluxes appropriate for the month of June. Deep <span class="hlt">convective</span> venting of the boundary layer (upward) dominates other components of the CO budget, e.g., downward <span class="hlt">convective</span> transport, loss of CO by oxidation, anthropogenic emissions, and CO produced from oxidation of methane, isoprene, and anthropogenic nonmethane hydrocarbons (NMHCs). Calculations of deep <span class="hlt">convective</span> venting are based on the method pf Pickering et al.(1992a) which uses a satellite-derived deep <span class="hlt">convective</span> cloud climatology along with transport statistics from <span class="hlt">convective</span> cloud model simulations of observed prototype squall line events. This study uses analyses of <span class="hlt">convective</span> episodes in 1985 and 1989 and CO measurements taken during several midwestern field campaigns. Deep <span class="hlt">convective</span> venting of the boundary layer over this moderately polluted region provides a net (upward minus downward) flux of 18.1 x 10(exp 8) kg CO/month to the free troposphere during early summer. Shallow cumulus and synoptic-scale weather systems together make a comparable contribution (total net flux 16.2 x 10(exp 8) kg CO/month). Boundary layer venting of CO with other O3 precursors leads to efficient free troposheric O3 formation. We estimate that deep <span class="hlt">convective</span> transport of CO and other precursors over the central United States in early summer leads to a gross production of 0.66 - 1.1 Gmol O3/d in good agreement with estimates of O3 production from boundary layer venting in a continental-scale model (Jacob et al., 1993a, b). On this respect the central U.S. region acts as s `chimney' for the country, and presumably this O3 contributes to high <span class="hlt">background</span> levels of O3 in the eastern United States and O3 export to the North Atlantic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15189054','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15189054"><span>Modeling of heat explosion with <span class="hlt">convection</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Belk, Michael; Volpert, Vitaly</p> <p>2004-06-01</p> <p>The work is devoted to numerical simulations of the interaction of heat explosion with natural <span class="hlt">convection</span>. The model consists of the heat equation with a nonlinear source term describing heat production due to an exothermic chemical reaction coupled with the Navier-Stokes equations under the Boussinesq approximation. We show how complex regimes appear through successive bifurcations leading from a stable stationary temperature distribution without <span class="hlt">convection</span> to a stationary symmetric <span class="hlt">convective</span> solution, stationary asymmetric <span class="hlt">convection</span>, periodic in time oscillations, and finally aperiodic oscillations. A simplified model problem is suggested. It describes the main features of solutions of the complete problem.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012CNSNS..17.1998B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012CNSNS..17.1998B"><span>Internally cooled <span class="hlt">convection</span>: A fillip for Philip</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Berlengiero, M.; Emanuel, K. A.; von Hardenberg, J.; Provenzale, A.; Spiegel, E. A.</p> <p>2012-05-01</p> <p>We discuss a simplified mathematical description of internally cooled <span class="hlt">convection</span> that includes a constant adiabatic lapse rate and an internal energy sink. The latter provides a representation of radiative cooling and, in combination, these two effects break the up-down symmetry of the vertical motions by making the <span class="hlt">convection</span> penetrative in the upper portion of the fluid layer. At large enough turbulent intensity of the motion, the dynamics is dominated by intense <span class="hlt">convective</span> updrafts that generate a strongly skewed distribution of vertical velocities. The numerical exploration of this model system exhibits a qualitatively useful description of atmospheric <span class="hlt">convection</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900054420&hterms=paraffin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dparaffin','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900054420&hterms=paraffin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D70%26Ntt%3Dparaffin"><span>Transient magmatic <span class="hlt">convection</span> prolonged by solidification</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brandeis, Genevieve; Marsh, Bruce D.</p> <p>1990-01-01</p> <p>Fluid dynamic experiments have been conducted on the solidification of a paraffin layer, in order to elucidate the transient stage of <span class="hlt">convection</span> created in cooling magma by the fact that strong changes in viscosity with crystallization lock up within an inwardly propagating crust much buoyancy that would otherwise be available to drive <span class="hlt">convection</span>. The interior of the magma remains isothermal, and the temperature decreases uniformly until it is locked at the <span class="hlt">convective</span> liquidus; the crystals are fine hairlike dendrites without major compositional differentiations. Measurements over time are presented of crust thickness, <span class="hlt">convective</span> velocity, and heat transfer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1330762','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1330762"><span>Forced <span class="hlt">convection</span> around the human head.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Clark, R P; Toy, N</p> <p>1975-01-01</p> <p>1. The parameters determining the forced <span class="hlt">convective</span> heat loss from a heated body in an air stream are outlined. 2. Local forced <span class="hlt">convective</span> heat transfer distributions around the human head and a heated vertical cylinder at various wind speeds in a climatic chamber have been found to be similar and related to the aerodynamic flow patterns. 3. From the local <span class="hlt">convective</span> coefficient distribution, values for the overall <span class="hlt">convective</span> coefficient h-c at various wind speeds have been evaluated. These are seen to agree closely with existing whole body coefficients determined by other methods. PMID:1142119</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A11N..08G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A11N..08G"><span>A Study of Detrainment from Deep <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Glenn, I. B.; Krueger, S. K.</p> <p>2014-12-01</p> <p>Uncertainty in the results of Global Climate Model simulations has been attributed to errors and simplifications in how parameterizations of <span class="hlt">convection</span> coarsely represent the processes of entrainment, detrainment, and mixing between <span class="hlt">convective</span> clouds and their environment. Using simulations of <span class="hlt">convection</span> we studied these processes at a resolution high enough to explicitly resolve them. Two of several recently developed analysis techniques that allow insight into these processes at their appropriate scale are an Eulerian method of directly measuring entrainment and detrainment, and a Lagrangian method that uses particle trajectories to map <span class="hlt">convective</span> mass flux over height and a cloud variable of interest. The authors of the Eulerian technique used it to show that the dynamics of shells of cold, humid air that surround shallow <span class="hlt">convective</span> updrafts have important effects on the properties of air entrained and detrained from the updrafts. There is some evidence for the existence of such shells around deep <span class="hlt">convective</span> updrafts as well, and that detrainment is more important than entrainment in determining the ultimate effect of the deep <span class="hlt">convection</span> on the large scale environment. We present results from analyzing a simulation of deep <span class="hlt">convection</span> through the Eulerian method as well as using Lagrangian particle trajectories to illustrate the role of the shell in the process of detrainment and mixing between deep <span class="hlt">convection</span> and its environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/5861576','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/5861576"><span>Energy transport using natural <span class="hlt">convection</span> boundary layers</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Anderson, R</p> <p>1986-04-01</p> <p>Natural <span class="hlt">convection</span> is one of the major modes of energy transport in passive solar buildings. There are two primary mechanisms for natural <span class="hlt">convection</span> heat transport through an aperture between building zones: (1) bulk density differences created by temperature differences between zones; and (2) thermosyphon pumping created by natural <span class="hlt">convection</span> boundary layers. The primary objective of the present study is to compare the characteristics of bulk density driven and boundary layer driven flow, and discuss some of the advantages associated with the use of natural <span class="hlt">convection</span> boundary layers to transport energy in solar building applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD0721242','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD0721242"><span>A Mesoscale Investigation of <span class="hlt">Convective</span> Activity.</span></a></p> <p><a target="_blank" href="http://www.dtic.mil/">DTIC Science & Technology</a></p> <p></p> <p></p> <p><span class="hlt">CONVECTION</span>(ATMOSPHERIC), MATHEMATICAL MODELS), (* TORNADOES , OKLAHOMA), (*THUNDERSTORMS, *OKLAHOMA), UPPER ATMOSPHERE, ATMOSPHERIC MOTION, HEAT TRANSFER, ENERGY, NETWORKS, WEATHER FORECASTING, COMPUTER PROGRAMS, THESES</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900054420&hterms=physique&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dphysique','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900054420&hterms=physique&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dphysique"><span>Transient magmatic <span class="hlt">convection</span> prolonged by solidification</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Brandeis, Genevieve; Marsh, Bruce D.</p> <p>1990-01-01</p> <p>Fluid dynamic experiments have been conducted on the solidification of a paraffin layer, in order to elucidate the transient stage of <span class="hlt">convection</span> created in cooling magma by the fact that strong changes in viscosity with crystallization lock up within an inwardly propagating crust much buoyancy that would otherwise be available to drive <span class="hlt">convection</span>. The interior of the magma remains isothermal, and the temperature decreases uniformly until it is locked at the <span class="hlt">convective</span> liquidus; the crystals are fine hairlike dendrites without major compositional differentiations. Measurements over time are presented of crust thickness, <span class="hlt">convective</span> velocity, and heat transfer.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900002181','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900002181"><span>A nonoscillatory, characteristically <span class="hlt">convected</span>, finite volume scheme for multidimensional <span class="hlt">convection</span> problems</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yokota, Jeffrey W.; Huynh, Hung T.</p> <p>1989-01-01</p> <p>A new, nonoscillatory upwind scheme is developed for the multidimensional <span class="hlt">convection</span> equation. The scheme consists of an upwind, nonoscillatory interpolation of data to the surfaces of an intermediate finite volume; a characteristic <span class="hlt">convection</span> of surface data to a midpoint time level; and a conservative time integration based on the midpoint rule. This procedure results in a <span class="hlt">convection</span> scheme capable of resolving discontinuities neither aligned with, nor <span class="hlt">convected</span> along, grid lines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=spectrophotometer&pg=3&id=EJ409265','ERIC'); return false;" href="https://eric.ed.gov/?q=spectrophotometer&pg=3&id=EJ409265"><span>The Cosmic <span class="hlt">Background</span> Explorer.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Gulkis, Samuel; And Others</p> <p>1990-01-01</p> <p>Outlines the Cosmic <span class="hlt">Background</span> Explorer (COBE) mission to measure celestial radiation. Describes the instruments used and experiments involving differential microwave radiometers, and a far infrared absolute spectrophotometer. (YP)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=microwave&pg=7&id=EJ409265','ERIC'); return false;" href="http://eric.ed.gov/?q=microwave&pg=7&id=EJ409265"><span>The Cosmic <span class="hlt">Background</span> Explorer.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Gulkis, Samuel; And Others</p> <p>1990-01-01</p> <p>Outlines the Cosmic <span class="hlt">Background</span> Explorer (COBE) mission to measure celestial radiation. Describes the instruments used and experiments involving differential microwave radiometers, and a far infrared absolute spectrophotometer. (YP)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040161205','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040161205"><span><span class="hlt">Convective</span> Instabilities in Liquid Foams</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Veretennikov, Igor; Glazier, James A.</p> <p>2004-01-01</p> <p>The main goal of this work is to better understand foam behavior both on the Earth and in microgravity conditions and to determine the relation between a foam's structure and wetness and its rheological properties. Our experiments focused on the effects of the bubble size distribution (BSD) on the foam behavior under gradual or stepwise in the liquid flow rate and on the onset of the <span class="hlt">convective</span> instability. We were able to show experimentally, that the BSD affects foam rheology very strongly so any theory must take foam texture into account.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12460472','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12460472"><span>Osmium isotopes and mantle <span class="hlt">convection</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hauri, Erik H</p> <p>2002-11-15</p> <p>The decay of (187)Re to (187)Os (with a half-life of 42 billion years) provides a unique isotopic fingerprint for tracing the evolution of crustal materials and mantle residues in the <span class="hlt">convecting</span> mantle. Ancient subcontinental mantle lithosphere has uniquely low Re/Os and (187)Os/(188)Os ratios due to large-degree melt extraction, recording ancient melt-depletion events as old as 3.2 billion years. Partial melts have Re/Os ratios that are orders of magnitude higher than their sources, and the subduction of oceanic or continental crust introduces into the mantle materials that rapidly accumulate radiogenic (187)Os. Eclogites from the subcontinental lithosphere have extremely high (187)Os/(188)Os ratios, and record ages as old as the oldest peridotites. The data show a near-perfect partitioning of Re/Os and (187)Os/(188)Os ratios between peridotites (low) and eclogites (high). The <span class="hlt">convecting</span> mantle retains a degree of Os-isotopic heterogeneity similar to the lithospheric mantle, although its amplitude is modulated by <span class="hlt">convective</span> mixing. Abyssal peridotites from the ocean ridges have low Os isotope ratios, indicating that the upper mantle had undergone episodes of melt depletion prior to the most recent melting events to produce mid-ocean-ridge basalt. The amount of rhenium estimated to be depleted from the upper mantle is 10 times greater than the rhenium budget of the continental crust, requiring a separate reservoir to close the mass balance. A reservoir consisting of 5-10% of the mantle with a rhenium concentration similar to mid-ocean-ridge basalt would balance the rhenium depletion of the upper mantle. This reservoir most likely consists of mafic oceanic crust recycled into the mantle over Earth's history and provides the material that melts at oceanic hotspots to produce ocean-island basalts (OIBs). The ubiquity of high Os isotope ratios in OIB, coupled with other geochemical tracers, indicates that the mantle sources of hotspots contain significant quantities</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900018927','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900018927"><span>Structural analysis of stratocumulus <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Siems, S. T.; Baker, M. B.; Bretherton, C. S.</p> <p>1990-01-01</p> <p>The 1 and 20 Hz data are examined from the Electra flights made on July 5, 1987. The flight legs consisted of seven horizontal turbulent legs at the inversion, midcloud, and below clouds, plus 4 soundings made within the same period. The Rosemont temperature sensor and the top and bottom dewpoint sensors were used to measure temperature and humidity at 1 Hz. Inversion structure and entrainment; local dynamics and large scale forcing; <span class="hlt">convective</span> elements; and decoupling of cloud and subcloud are discussed in relationship to the results of the Electra flight.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2000PhFl...12.2137B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2000PhFl...12.2137B"><span>Bursts in inclined layer <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Busse, F. H.; Clever, R. M.</p> <p>2000-08-01</p> <p>A new instability of longitudinal rolls in an inclined fluid layer heated from below is analyzed in the case of the Prandtl number P=0.71. The instability assumes the form of subharmonic undulations and evolves into a spatially chaotic pattern when the angle of inclination is of the order of 20°. The chaotic state rapidly decays and longitudinal rolls recover until the next burst of chaotic <span class="hlt">convection</span> occurs. The theoretical findings closely correspond to recent experimental observations by Daniels et al. [Phys. Rev. Lett. (to be published)].</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JGRD..122...47X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JGRD..122...47X"><span>Mechanisms of secondary <span class="hlt">convection</span> within a Mei-Yu frontal mesoscale <span class="hlt">convective</span> system in eastern China</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, Xin; Xue, Ming; Wang, Yuan; Huang, Hao</p> <p>2017-01-01</p> <p>The generation of secondary <span class="hlt">convection</span>, following an earlier episode of <span class="hlt">convection</span>, within a heavy-rain-producing mesoscale <span class="hlt">convective</span> system (MCS) along a Mei-Yu front in eastern China on 6-8 July 2013 is studied based on <span class="hlt">convection</span>-permitting Weather Research and Forecasting simulations. The initiation of the secondary <span class="hlt">convection</span> is found to be directly linked to the downward development of a mesoscale <span class="hlt">convective</span> vortex (MCV) spawn by the MCS. In the early and mature stage, the MCV center is located at the middle troposphere; it descends gradually with time as the parent MCS began to decay, with the associated <span class="hlt">convection</span> transitioning from deep to shallow <span class="hlt">convection</span>. The descent of the MCV occurs in response to the lowering of the maximum diabatic heating within the <span class="hlt">convective</span> system, which increases positive potential vorticity down below. When the MCV reaches the lower troposphere, it becomes coupled with the prefrontal southwesterly low-level jet (LLJ). The confluence of the MCV rotational flow with the LLJ notably enhances the convergence on the southern flank of the MCV, where the secondary <span class="hlt">convection</span> is triggered and swapped through the southeastern flank of the MCV. Unlike that found in the MCV of the U.S. Central Plains, the cold pool produced by the Mei-Yu frontal MCS is rather weak and shallow and appears to play only a minor role in promoting <span class="hlt">convection</span>. The balanced isentropic lifting by the MCV circulation is also weak, although the MCV circulation does help localize the secondary <span class="hlt">convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311125&keyword=Thermodynamics&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311125&keyword=Thermodynamics&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50"><span>A Dynamically Computed <span class="hlt">Convective</span> Time Scale for the Kain–Fritsch <span class="hlt">Convective</span> Parameterization Scheme</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Many <span class="hlt">convective</span> parameterization schemes define a <span class="hlt">convective</span> adjustment time scale τ as the time allowed for dissipation of <span class="hlt">convective</span> available potential energy (CAPE). The Kain–Fritsch scheme defines τ based on an estimate of the advective time period for deep con...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311125&keyword=Thermodynamics&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=91040738&CFTOKEN=55703293','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311125&keyword=Thermodynamics&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=91040738&CFTOKEN=55703293"><span>A Dynamically Computed <span class="hlt">Convective</span> Time Scale for the Kain–Fritsch <span class="hlt">Convective</span> Parameterization Scheme</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Many <span class="hlt">convective</span> parameterization schemes define a <span class="hlt">convective</span> adjustment time scale τ as the time allowed for dissipation of <span class="hlt">convective</span> available potential energy (CAPE). The Kain–Fritsch scheme defines τ based on an estimate of the advective time period for deep con...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014MNRAS.438.1137D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014MNRAS.438.1137D"><span>Properties of semi-<span class="hlt">convection</span> and <span class="hlt">convective</span> overshooting for massive stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ding, C. Y.; Li, Y.</p> <p>2014-02-01</p> <p>The properties of semi-<span class="hlt">convection</span> and core <span class="hlt">convective</span> overshooting of stars with masses of 15 and 30 M⊙ are calculated in the present article. New methods are used to deal with semi-<span class="hlt">convection</span>. Different entropy gradients are used when adopting the Schwarzschild and Ledoux methods, which are used to confine the <span class="hlt">convective</span> boundary and calculate the turbulent quantities: {{partial } overline{s}}/{{partial } r}=-({c_p}/{H_P})(nabla -nabla _ad) when the Schwarzschild method is adopted and {{partial } overline{s}}/{{partial } r}=-({c_p}/{H_P})(nabla -nabla _ad-nabla _{μ }) when the Ledoux method is adopted. Core <span class="hlt">convective</span> overshooting and semi-<span class="hlt">convection</span> are treated as a whole and their development is found to present almost opposing tendencies: more intensive core <span class="hlt">convective</span> overshooting leads to weaker semi-<span class="hlt">convection</span>. The influence of different parameters and <span class="hlt">convection</span> processing methods on the turbulent quantities is analysed in this article. Increasing the mixing-length parameter α leads to more turbulent dynamic energy in the <span class="hlt">convective</span> core and prolongs the overshooting distance but depresses the development of semi-<span class="hlt">convection</span>. Adoption of the Ledoux method leads to overshooting extending further and semi-<span class="hlt">convection</span> development being suppressed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26991599','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26991599"><span>Exploitation of hazelnut, maize germ and sesame seed aqueous extraction residues in the <span class="hlt">stabilisation</span> of sesame seed paste (tahini).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Evlogimenou, Anthi; Paraskevopoulou, Adamantini; Kiosseoglou, Vassilios</p> <p>2017-01-01</p> <p>Sesame seed paste is a highly nutritious food product which, upon long-term storage, tends to exhibit undesirable phenomena of oiling-off and particle sedimentation. The ability of rich-in-fibre aqueous extraction powders originating from oleaginous raw materials to enhance the physical stability of sesame paste is investigated in this study. The extraction residues remaining after treating hazelnut, sesame seed or maize germ with aqueous media in order to extract and exploit their oil bodies, were collected, dehydrated and milled into fine powders. The powders were then incorporated at various levels into a commercially available sesame paste product to assess their potential as paste <span class="hlt">stabilisers</span> against oil separation. The solids from maize germ exhibited the highest <span class="hlt">stabilising</span> ability followed by the solids from hazelnut. In contrast, the solids originating from the sesame seed were less effective in <span class="hlt">stabilising</span> the sesame paste. Shear stress-rate of shear measurements of sesame paste incorporating the extraction residue solids were conducted in an attempt to explain the different <span class="hlt">stabilising</span> behaviour of the three powders. The intensity of interactions between the incorporated solids within the sesame paste structure may determine the rheological properties of the blend and hence its stability against oiling-off upon long-term storage. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4851264','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4851264"><span>Changes in Muscarinic M2 Receptor Levels in the Cortex of Subjects with Bipolar Disorder and Major Depressive Disorder and in Rats after Treatment with Mood <span class="hlt">Stabilisers</span> and Antidepressants</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Gibbons, Andrew Stuart; Jeon, Won Je; Scarr, Elizabeth; Dean, Brian</p> <p>2016-01-01</p> <p><span class="hlt">Background</span>: Increasingly, data are implicating muscarinic receptors in the aetiology and treatment of mood disorders. This led us to measure levels of different muscarinic receptor-related parameters in the cortex from people with mood disorders and the CNS of rats treated with mood <span class="hlt">stabilisers</span> and antidepressant drugs. Methods: We measured [3H]AF-DX 384 binding in BA 46 and BA 24 from subjects with bipolar disorders (n = 14), major depressive disorders (n = 19), as well as age- and sex-matched controls (n = 19) and the CNS of rats treated with fluoxetine or imipramine. In addition, we used Western blots to measure levels of CHRM2 protein and oxotremorine-M stimulated [35S]GTPγS binding as a measure of CHRM 2 / 4 signaling. Results: Compared with controls, [3H]AF-DX 384 binding was lower in BA 24 and BA 46 in bipolar disorders and major depressive disorders, while CHRM2 protein and oxotremorine-M stimulated [35S]GTPγS binding was only lower in BA 24. Compared with vehicle, treatment with mood <span class="hlt">stabilisers</span>, antidepressant drugs for 10 days, or imipramine for 28 days resulted in higher levels of in [3H]AF-DX 384 binding select regions of rat CNS. Conclusions: Our data suggest that levels of CHRM2 are lower in BA 24 from subjects with mood disorders, and it is possible that signalling by that receptor is also less in this cortical region. Our data also suggest increasing levels of CHRM2 may be involved in the mechanisms of action of mood <span class="hlt">stabilisers</span> and tricyclic antidepressants. PMID:26475745</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20846348','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20846348"><span><span class="hlt">Stabilisation</span> and humanitarian access in a collapsed state: the Somali case.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Menkhaus, Ken</p> <p>2010-10-01</p> <p>Somalia today is the site of three major threats: the world's worst humanitarian crisis; the longest-running instance of complete state collapse; and a robust jihadist movement with links to Al-Qa'ida. External state-building, counter-terrorism and humanitarian policies responding to these threats have worked at cross-purposes. State-building efforts that insist humanitarian relief be channelled through the nascent state in order to build its legitimacy and capacity undermine humanitarian neutrality when the state is a party to a civil war. Counter-terrorism policies that seek to ensure that no aid benefits terrorist groups have the net effect of criminalising relief operations in countries where poor security precludes effective accountability. This paper argues that tensions between <span class="hlt">stabilisation</span> and humanitarian goals in contemporary Somalia reflect a long history of politicisation of humanitarian operations in the country.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11220180','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11220180"><span><span class="hlt">Stabilisation</span> of bank slopes that are prone to liquefaction in ecologically sensitive areas.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Nestler, P; Stoll, R D</p> <p>2001-01-01</p> <p>A consequence of lignite stripping in the Lusatia mining district (East Germany) is the backfilling of dumps that mainly consist of low-compacted fine and medium-grained sands. When the ground-water table, which had been lowered while stripping the coal, is rising again, these dumps might be affected by a settlement flow due to the liquefaction of soils. Common methods for <span class="hlt">stabilisation</span> as, for instance, blasting or vibrator-jetting deep compaction, are not very useful in ecologically sensitive areas, where dumps have been afforested and embankment areas of residual lakes have developed into highly valuable biotopes. A new so-called air-impulse method in combination with directional horizontal drilling has been developed, which does not have a considerably negative impact on the vegetation during compaction. The experience gained during the first employment of this method at the lake "Katja", a residual lake of lignite stripping, is presented in this paper.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016QuEle..46.1110K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016QuEle..46.1110K"><span><span class="hlt">Stabilisation</span> of a fibre frequency synthesiser using acousto-optical and electro-optical modulators</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Koliada, N. A.; Nyushkov, B. N.; Pivtsov, V. S.; Dychkov, A. S.; Farnosov, S. A.; Denisov, V. I.; Bagayev, S. N.</p> <p>2016-12-01</p> <p>A fibre-optic frequency synthesiser is developed that is <span class="hlt">stabilised</span> to the optical frequency standard based on molecular iodine ({\\text{Nd : YAG/I}}2). The possibility of transferring stability of the optical frequency standard to other optical frequencies in the IR range 1 - 2 \\unicode{956}{\\text{m}} and to the RF range by using synthesiser phase-locked loops (PLLs) with acousto-optical and electro-optical modulators is experimentally demonstrated. The additive instability introduced into the optical frequency comb of the synthesiser (which arises due to PLL residual random errors) is several orders less than the intrinsic instability of the reference optical frequency standard employed (i.e., is noticeably less than 1 × 10-13 for 1 {\\text{s}} and 5 × 10-15 for 1000 {\\text{s}}).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/576596','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/576596"><span>Remediation by in-situ solidification/<span class="hlt">stabilisation</span> of Ardeer landfill, Scotland</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Wyllie, M.; Esnault, A.; Barker, P.</p> <p>1997-12-31</p> <p>The Ardeer Landfill site at ICI Explosives factory on the west coast of Scotland had been a repository for waste from the site for 40 years. In order to safeguard the local environment ICI Explosives, with approval of Local Authorities and the Clyde River Purification Board put into action a programme of investigation and planning which culminated in the in-situ treatment of 10,000 m3 of waste within the landfill by a deep mixing method using the {open_quotes}Colmix{close_quotes} system. The paper describes in varying degrees of detail the remediation from investigation to the execution of the in-situ <span class="hlt">stabilisation</span> and presents the post construction monitoring results.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2007SPIE.6453E..0QJ','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2007SPIE.6453E..0QJ"><span>Characterization and <span class="hlt">stabilising</span> dynamic phase fluctuations in large mode area fibres</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jones, D. C.; Scott, A. M.</p> <p>2007-02-01</p> <p>Fibre amplifiers exhibit rapid time dependent phase fluctuations due to the environment and to thermal and other effects associated with the pumping and lasing processes. We characterise these effects in a large mode area fibre amplifier having an output power of 260W limited only by pump power. The amplifier retains its coherence even at the highest available output power with negligible linewidth broadening. Phase fluctuations are characterised by a low-amplitude power-independent jitter superimposed on a power-dependent drift due to heating. We also measure the phase fluctuations in a COTS fibre preamplifier and find they are predominantly large amplitude periodic oscillations at 110Hz, probably induced by pump power fluctuations. The two amplifiers were combined in series to give a high gain amplifier chain and actively phase <span class="hlt">stabilised</span> to high precision (~λ/37 rms) using a piezo-ceramic fibre stretcher incorporated into a PC-based feedback loop.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014JNuM..454..398T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014JNuM..454..398T"><span>Synthesis of dense yttrium-<span class="hlt">stabilised</span> hafnia pellets for nuclear applications by spark plasma sintering</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tyrpekl, Vaclav; Holzhäuser, Michael; Hein, Herwin; Vigier, Jean-Francois; Somers, Joseph; Svora, Petr</p> <p>2014-11-01</p> <p>Dense yttrium-<span class="hlt">stabilised</span> hafnia pellets (91.35 wt.% HfO2 and 8.65 wt.% Y2O3) were prepared by spark plasma sintering consolidation of micro-beads synthesised by the “external gelation” sol-gel technique. This technique allows a preparation of HfO2-Y2O3 beads with homogenous yttria-hafnia solid solution. A sintering time of 5 min at 1600 °C was sufficient to produce high density pellets (over 90% of the theoretical density) with significant reproducibility. The pellets have been machined in a lathe to the correct dimensions for use as neutron absorbers in an experimental test irradiation in the High Flux Reactor (HFR) in Petten, Holland, in order to investigate the safety of americium based nuclear fuels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20579807','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20579807"><span>Investigation of 4-year-old <span class="hlt">stabilised</span>/solidified and accelerated carbonated contaminated soil.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Antemir, A; Hills, C D; Carey, P J; Magnié, M-C; Polettini, A</p> <p>2010-09-15</p> <p>The investigation of the pilot-scale application of two different <span class="hlt">stabilisation</span>/solidification (S/S) techniques was carried out at a former fireworks and low explosives manufacturing site in SE England. Cores and granular samples were recovered from uncovered accelerated carbonated (ACT) and cement-treated soils (S/S) after 4 years to evaluate field-performance with time. Samples were prepared for microstructural examination and leaching testing. The results indicated that the cement-treated soil was progressively carbonated over time, whereas the mineralogy of the carbonated soil remained essentially unchanged. Distinct microstructures were developed in the two soils. Although Pb, Zn and Cu leached less from the carbonated soil, these metals were adequately immobilised by both treatments. Geochemical modeling of pH-dependent leaching data suggested that the retention of trace metals resulted from different immobilisation mechanisms operating in the two soils examined.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IJC....88.1189K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IJC....88.1189K"><span>Observer-based <span class="hlt">stabilisation</span> of linear systems with parameter uncertainties by using enhanced LMI conditions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kheloufi, Houria; Bedouhene, Fazia; Zemouche, Ali; Alessandri, Angelo</p> <p>2015-06-01</p> <p>This paper deals with the problem of observer-based <span class="hlt">stabilisation</span> for linear systems with structured norm-bounded parameter uncertainties. A new design methodology is established thanks to a judicious use of some mathematical artefacts such as the well-known Young inequality and various matrix decompositions. The proposed method allows one to compute simultaneously the observer and controller gains by solving a single bilinear matrix inequality (BMI), which becomes a linear matrix inequality (LMI) by freezing some scalars. Furthermore, we show that some existing and elegant results reported in the literature can be regarded as particular cases of the stability conditions presented here. Numerical examples and evaluations of the conservatism are provided to show the effectiveness of the proposed design methodology.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014VSD....52.1658M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014VSD....52.1658M"><span>Comparing and validating models of driver steering behaviour in collision avoidance and vehicle <span class="hlt">stabilisation</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Markkula, G.; Benderius, O.; Wahde, M.</p> <p>2014-12-01</p> <p>A number of driver models were fitted to a large data set of human truck driving, from a simulated near-crash, low-friction scenario, yielding two main insights: steering to avoid a collision was best described as an open-loop manoeuvre of predetermined duration, but with situation-adapted amplitude, and subsequent vehicle <span class="hlt">stabilisation</span> could to a large extent be accounted for by a simple yaw rate nulling control law. These two phenomena, which could be hypothesised to generalise to passenger car driving, were found to determine the ability of four driver models adopted from the literature to fit the human data. Based on the obtained results, it is argued that the concept of internal vehicle models may be less valuable when modelling driver behaviour in non-routine situations such as near-crashes, where behaviour may be better described as direct responses to salient perceptual cues. Some methodological issues in comparing and validating driver models are also discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014IJC....87..682B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014IJC....87..682B"><span>The design of suboptimal asymptotic <span class="hlt">stabilising</span> controllers for nonlinear slowly varying systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Binazadeh, T.; Shafiei, M. H.</p> <p>2014-04-01</p> <p>The design of asymptotic <span class="hlt">stabilising</span> controllers for slowly varying nonlinear systems is considered in this paper. The designed control law is based on finding a slowly varying control Lyapunov function. Also, consideration of the Hamilton-Jacobi-Bellman equation showed that the proposed controller is a suboptimal controller and the response of the system may be very close to its optimal solution. The maximum admissible rate of changes of the system dynamic is also evaluated. This technique is first applied to a created example and then to a practical example (optimal autopilot design for an air vehicle). The air vehicle is modelled as a nonlinear slowly varying system and the efficiency of the designed autopilot in terms of transient responses, control signals and the values of cost function are shown by numerical simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJSyS..47.3545S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJSyS..47.3545S"><span>Global ?-exponential <span class="hlt">stabilisation</span> of a class of nonlinear networked control systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shen, Yan-Jun; Zhang, Daoyuan; Huang, Yuehua; Liu, Yungang</p> <p>2016-11-01</p> <p>In this paper, we investigate global ?-exponential <span class="hlt">stabilisation</span> of a class of nonlinear networked control systems. The network-induced delays are assumed to be random and significantly smaller than the sampling period. First, sufficient conditions are presented to ensure global ?-exponential stability for a class of hybrid systems with time delay. Then, the networked control systems are modelled as the hybrid systems with time delay. By the techniques of adding a power integrator and a recursive argument, a sampled-data state feedback control law is presented. Sufficient conditions are given to ensure global ?-exponential stability of the closed-loop system by constructing a Lyapunov-Krasovskii function. Finally, a numerical example is presented to show the validity of the new methods.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24571702','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24571702"><span>Protective benefits of a <span class="hlt">stabilised</span> stannous-containing fluoride dentifrice against erosive acid damage.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Faller, Robert V; Eversole, Sandra L; Saunders-Burkhardt, Kymberly</p> <p>2014-03-01</p> <p>To assess the potential of a <span class="hlt">stabilised</span> stannous (Sn)-containing NaF dentifrice (Oral B/blend-a-Med(®) Pro-Expert), in addition to a number of other marketed European dentifrices formulated with various fluoride actives and two control dentifrices, to protect enamel against erosive acid damage. Cores of human enamel (four per group) were soaked in pooled human saliva, and then treated with a 1:3 slurry (dentifrice:saliva) using a standardised in vitro erosion model (5-day cycling) that includes 10-minute challenges with 1% citric acid applied 60 minutes after each dentifrice treatment. Enamel surface loss was measured using transverse microradiography (TMR). Specimens treated with the Sn-containing NaF dentifrice showed 6.5 μm of surface loss ± 1.2 (SEM), which was not significantly different (P < 0.05, Fisher LSD) from that of a clinically proven, <span class="hlt">stabilised</span> SnF2 positive control [Crest(®) Pro-Health, 1,100 ppm F as SnF2 : 3.0 μm of surface loss ± 1.1 (SEM)]. The Sn-containing NaF dentifrice and the clinically proven positive control both provided significantly greater protection (P < 0.05, Fisher LSD) compared with all of the other products tested. Enamel loss (SEM) values for other European products and the reference control (active agents) were: Meridol(®) : (1,400 ppm F as AmF + SnF2 ) 12.0 μm (1.47); Colgate(®) Cavity Protection: (1,450 ppm F as SMFP + NaF) 12.9 μm (1.66); Odol med 3(®) (1,400 ppm F as NaF) 14.2 μm (1.49); Elmex(®) (1,400 ppm F as AmF) 14.5 μm (1.76); Colgate(®) Enamel Protect: (1,450 ppm F as NaF + KNO3 ) 16.3 μm (2.02); Lacalut(®) aktiv: (1,400 ppm F as AlF3 ) 18.5 μm (1.71); Sensodyne(®) ProNamel(™) : (1,450 ppm F as NaF + KNO3 ) 20.5 μm (1.26); Crest Cavity Protection (1,100 ppm F as NaF, reference control) 22.00 μm (2.04); and Mentadent(®) : (1,450 ppm F as NaF + Zn citrate) 22.3 μm (0.63). These results support the potential for the <span class="hlt">stabilised</span>, Sn-containing NaF dentifrice to provide erosion protection benefits</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009AcAau..64..796S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009AcAau..64..796S"><span>Three-axis active control system for gravity gradient <span class="hlt">stabilised</span> microsatellite</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Si Mohammed, A. M.; Benyettou, M.; Bentoutou, Y.; Boudjemai, A.; Hashida, Y.; Sweeting, M. N.</p> <p>2009-04-01</p> <p>In this paper, the control system of the first Algerian microsatellite in orbit Alsat-1 is presented. Alsat-1 is a 3-axis <span class="hlt">stabilised</span> microsatellite, using a pitch momentum wheel and yaw reaction wheel, with dual redundant 3-axis magnetorquers. A gravity gradient boom is employed to provide a high degree of platform stability. Two vector magnetometers and four dual sun sensors are carried in order to determine the attitude. This paper examines the low Earth orbit (LEO) control system requirements and design in the context of a real system, the Surrey Satellite Technology Limited (SSTL) advanced microsatellite platform and puts forward designs for the control system to match the advanced capability of the enhanced microsatellite platform. Numerical results show the effectiveness of the implementation. Comparison with in orbit results is presented to evaluate the performance of the control system during accurate Nadir pointing control.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26833622','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26833622"><span>Acquired phototrophy <span class="hlt">stabilises</span> coexistence and shapes intrinsic dynamics of an intraguild predator and its prey.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Moeller, Holly V; Peltomaa, Elina; Johnson, Matthew D; Neubert, Michael G</p> <p>2016-04-01</p> <p>In marine ecosystems, acquired phototrophs - organisms that obtain their photosynthetic ability by hosting endosymbionts or stealing plastids from their prey - are omnipresent. Such taxa function as intraguild predators yet depend on their prey to periodically obtain chloroplasts. We present a new theory for the effects of acquired phototrophy on community dynamics by analysing a mathematical model of this predator-prey interaction and experimentally verifying its predictions with a laboratory model system. We show that acquired phototrophy <span class="hlt">stabilises</span> coexistence, but that the nature of this coexistence exhibits a 'paradox of enrichment': as light increases, the coexistence between the acquired phototroph and its prey transitions from a stable equilibrium to boom-bust cycles whose amplitude increases with light availability. In contrast, heterotrophs and mixotrophic acquired phototrophs (that obtain < 30% of their carbon from photosynthesis) do not exhibit such cycles. This prediction matches field observations, in which only strict ( > 95% of carbon from photosynthesis) acquired phototrophs form blooms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1712228H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1712228H"><span>Inacessible Andean sites reveal land-use induced <span class="hlt">stabilisation</span> of soil organic carbon</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heitkamp, Felix; Maqsood, Shafique; Sylvester, Steven; Kessler, Michael; Jungkunst, Hermann</p> <p>2015-04-01</p> <p>Human activity affects properties and development of ecosystems across the globe to such a degree that it is challenging to get baseline values for undisturbed ecosystems. This is especially true for soils, which are affected by land-use history and hold a legacy of past human interventions. Therefore, it is still largely unknown how soil would have developed "naturally" and if processes of organic matter <span class="hlt">stabilisation</span> would be different in comparison to managed soils. Here, we show undisturbed soil development, i.e., the processes of weathering and accumulation of soil organic carbon (SOC), by comparing pristine with grazed sites in the high Andes (4500 m) of southern Peru. We located study plots on a large ledge (0.2 km²) that is only accessible with mountaineering equipment. Plots with pristine vegetation were compared to rangeland plots that were constantly under grazing management for at least four millennia. All "state factors"; climate, potential biota, topography, parent material and time; besides "land-use" were, therefore, identical. Vegetation change, induced by grazing management, led to lower vegetation cover of the soil, thereby increasing soil surface temperatures and soil acidification. Both factors increased weathering in rangeland soils, as indicated by the presence of pedogenic oxides, especially amorphous Al-(oxy)hydroxides (oxalate-extractable Al). Higher losses of base cations (K, Na, Ca) and lower pH-values were related to a low base saturation of exchange sites in rangelands. Therefore, rangeland soils were classified as Umbrisol, whereas soils under pristine vegetation were classified as Phaeozeme. All profiles were rich in SOC (100 to 126 g kg-1) with no significant differences in concentrations or stocks. SOC of rangeland soils was, however, less available for microorganisms (proportion of microbial C on SOC: 1.8 vs. 0.6% in pristine and rangeland soils, respectively) and showed higher stability against thermal degradation. Reasons for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25722104','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25722104"><span>Synthesis, structural studies and ligand influence on the stability of aryl-NHC <span class="hlt">stabilised</span> trimethylaluminium complexes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>M, Melissa Wu; Gill, Arran M; Yunpeng, Lu; Falivene, Laura; Yongxin, Li; Ganguly, Rakesh; Cavallo, Luigi; García, Felipe</p> <p>2015-09-14</p> <p>Treatment of a series of aromatic NHCs (IMes, SIMes, IPr and SIPr) with trimethylaluminium produced their corresponding Lewis acid-base adducts: IMes·AlMe3 (1), SIMes·AlMe3 (2), IPr·AlMe3 (3), and SIPr·AlMe3 (4). These complexes expand the few known examples of saturated NHC <span class="hlt">stabilised</span> Group 13 complexes. Furthermore, compounds 1-4 show differential stability depending on the nature of the NHC ligand. Analyses of topographic steric maps and NHC %V(Bur) were used to explain these differences. All the compounds have been fully characterised by multinuclear NMR spectroscopy, IR and single crystal X-ray analysis together with computational studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3187950','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3187950"><span>Le facteur XII de la coagulation: bien plus qu’un <span class="hlt">stabilisant</span> de la fibrine</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Messaoudi, N.; Lamaalmi, F.; Chakour, M.; Belmekki, A.; Naji, M.</p> <p>2011-01-01</p> <p>Summary Les Auteurs considèrent le rôle du facteur XIII de la coagulation dans la cicatrisation. Identifié depuis 1923, le rôle du facteur XIII ou le facteur <span class="hlt">stabilisant</span> de la fibrine dans la coagulation a été bien élucidé. Son rôle dans la cicatrisation suggéré dès 1960 est méconnu par les hématologistes et les médecins prenant en charge les brûlés. Les Auteurs se proposent de mettre la lumière sur ce rôle, qui reste encore mystérieux et mérite d’être élucidé. PMID:21991236</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJSyS..47..328Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJSyS..47..328Z"><span><span class="hlt">Stabilisation</span> and consensus of linear systems with multiple input delays by truncated pseudo-predictor feedback</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhou, Bin; Cong, Shen</p> <p>2016-01-01</p> <p>This paper provides a new approach referred to as pseudo-predictor feedback (PPF) for <span class="hlt">stabilisation</span> of linear systems with multiple input delays. Differently from the traditional predictor feedback which is from the model reduction appoint of view, the proposed PPF utilises the idea of prediction by generalising the corresponding results for linear systems with a single input delay to the case of multiple input delays. Since the PPF will generally lead to distributed controllers, a truncated pseudo-predictor feedback (TPPF) approach is established instead, which gives finite dimensional controllers. It is shown that the TPPF can compensate arbitrarily large yet bounded delays as long as the open-loop system is only polynomially unstable. The proposed TPPF approach is then used to solve the consensus problems for multi-agent systems characterised by linear systems with multiple input delays. Numerical examples show the effectiveness of the proposed approach.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJSyS..47.2985S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJSyS..47.2985S"><span>Input-output finite-time <span class="hlt">stabilisation</span> of nonlinear stochastic system with missing measurements</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Song, Jun; Niu, Yugang; Jia, Tinggang</p> <p>2016-09-01</p> <p>This paper considers the problem of the input-output finite-time <span class="hlt">stabilisation</span> for a class of nonlinear stochastic system with state-dependent noise. The phenomenon of the missing measurements may occur when state signals are transmitted via communication networks. An estimating method is proposed to compensate the lost state information. And then, a compensator-based controller is designed to ensure the input-output finite-time stochastic stability (IO-FTSS) of the closed-loop system. Some parameters-dependent sufficient conditions are derived and the corresponding solving approach is given. Finally, numerical simulations are provided to demonstrate the feasibility and effectiveness of the developed IO-FTSS scheme.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20641044','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20641044"><span>Interfacing living unicellular algae cells with biocompatible polyelectrolyte-<span class="hlt">stabilised</span> magnetic nanoparticles.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fakhrullin, Rawil F; Shlykova, Lubov V; Zamaleeva, Alsu I; Nurgaliev, Danis K; Osin, Yuri N; García-Alonso, Javier; Paunov, Vesselin N</p> <p>2010-10-08</p> <p>Green algae are a promising platform for the development of biosensors and bioelectronic devices. Here we report a reliable single-step technique for the functionalisation of living unicellular green algae Chlorella pyrenoidosa with biocompatible 15 nm superparamagnetic nanoparticles <span class="hlt">stabilised</span> with poly(allylamine hydrochloride). The magnetised algae cells can be manipulated and immobilised using external permanent magnets. The distribution of the nanoparticles on the cell walls of C. pyrenoidosa was studied by optical and fluorescence microscopy, TEM, SEM and EDX spectroscopy. The viability and the magnetic properties of the magnetised algae are studied in comparison with the native cells. The technique may find a number of potential applications in biotechnology and bioelectronics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28275776','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28275776"><span>Oil-in-water emulsions <span class="hlt">stabilised</span> by cellulose ethers: stability, structure and in vitro digestion.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Borreani, Jennifer; Espert, María; Salvador, Ana; Sanz, Teresa; Quiles, Amparo; Hernando, Isabel</p> <p>2017-04-19</p> <p>The effect of cellulose ethers in oil-in-water emulsions on stability during storage and on texture, microstructure and lipid digestibility during in vitro gastrointestinal digestion was investigated. All the cellulose ether emulsions showed good physical and oxidative stability during storage. In particular, the methylcellulose with high methoxyl substituents (HMC) made it possible to obtain emulsions with high consistency which remained almost unchanged during gastric digestion, and thus could enhance fullness and satiety perceptions at gastric level. Moreover, the HMC emulsion slowed down lipid digestion to a greater extent than a conventional protein emulsion or the emulsions <span class="hlt">stabilised</span> by the other cellulose ethers. Therefore, HMC emulsions could be used in weight management to increase satiation capacity and decrease lipid digestion.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IJSyS..46.2897L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IJSyS..46.2897L"><span>Global finite-time <span class="hlt">stabilisation</span> of a class of switched nonlinear systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Liang, Ying-Jiu; Ma, Ruicheng; Wang, Min; Fu, Jun</p> <p>2015-12-01</p> <p>This paper is concerned with the global finite-time <span class="hlt">stabilisation</span> problem for a class of switched nonlinear systems under arbitrary switchings. All subsystems of the studied switched system under consideration are in lower triangular form. Based on the adding one power integrator technique, both a class of non-Lipschitz continuous state feedback controllers and a common Lyapunov function are simultaneously constructed such that the closed-loop switched system is global finite-time stable under arbitrary switchings. In the controller design process, a common coordinate transformation of all subsystems is exploited to avoid using individual coordinate transformations for subsystems. Finally, two examples are given to show the effectiveness of the proposed method.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24781620','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24781620"><span>Patellar clunk syndrome in fixed-bearing posterior-<span class="hlt">stabilised</span> versus cruciate-substituting prostheses.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Tang, Yan Ho; Wong, Wing Keung; Wong, Hok Leung</p> <p>2014-04-01</p> <p>To compare the outcome of fixed-bearing posterior-<span class="hlt">stabilised</span> versus cruciate-substituting prostheses in 46 patients who underwent primary bilateral total knee replacement (TKR). Records of 35 women and 11 men aged 54 to 78 (mean, 67) years who underwent primary bilateral TKR for osteoarthritis (n=44) and rheumatoid arthritis (n=2) were retrospectively reviewed. A fixed-bearing posterior-<span class="hlt">stabilised</span> prosthesis (Zimmer NexGen Legacy flex [LPS-Flex]) was used in one knee, and a fixed-bearing cruciate-substituting prosthesis (Depuy Press Fit Condylar Sigma CS [PFC CS]) was used in the contralateral knee. The mean time interval between the 2 operations was 34 (range, 4-60) months. All operations were performed by the same group of surgeons using standardised techniques. The medial parapatellar approach was used, and the patella was resurfaced. Rehabilitation was also standardised. Outcome measures included the pre- and post-operative active range of movement and the American Knee Society Score. Postoperative complications were documented. At one year, the mean fixed flexion contracture, maximum flexion, and American Knee Society scores in knees with PFC CS and LPS-Flex prostheses were comparable. Three knees with the PFC CS prosthesis developed the patellar clunk syndrome, compared to none with the LPS-Flex prosthesis (p=0.24). The onset of the patellar clunk syndrome was around one year after surgery. Despite this, the axial alignment and rotation of the femoral and tibial components were good. Both prostheses produce good clinical outcome. The PFC CS prosthesis is more likely to be associated with the patellar clunk syndrome.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28628902','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28628902"><span>Recycling <span class="hlt">stabilised</span>/solidified drill cuttings for forage production in acidic soils.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kogbara, Reginald B; Dumkhana, Bernard B; Ayotamuno, Josiah M; Okparanma, Reuben N</p> <p>2017-10-01</p> <p><span class="hlt">Stabilisation</span>/solidification (S/S), which involves fixation and immobilisation of contaminants using cementitious materials, is one method of treating drill cuttings before final fate. This work considers reuse of <span class="hlt">stabilised</span>/solidified drill cuttings for forage production in acidic soils. It sought to improve the sustainability of S/S technique through supplementation with the phytoremediation potential of plants, eliminate the need for landfill disposal and reduce soil acidity for better plant growth. Drill cuttings with an initial total petroleum hydrocarbon (TPH) concentration of 17,125 mg kg(-1) and low concentrations of metals were treated with 5%, 10%, and 20% cement dosages. The treated drill cuttings were reused in granular form for growing a forage, elephant grass (Pennisetum purpureum), after mixing with uncontaminated soil. The grasses were also grown in uncontaminated soil. The phytoremediation and growth potential of the plants was assessed over a 12-week period. A mix ratio of one part drill cuttings to three parts uncontaminated soil was required for active plant growth. The phytoremediation ability of elephant grass (alongside abiotic losses) reduced the TPH level (up to 8795 mg kg(-1)) in the soil-treated-drill cuttings mixtures below regulatory (1000 mg kg(-1)) levels. There were also decreased concentrations of metals. The grass showed better heights and leaf lengths in soil containing drill cuttings treated with 5% cement dosage than in uncontaminated soil. The results suggest that recycling S/S treated drill cuttings for forage production may be a potential end use of the treated waste. Copyright © 2017 Elsevier Ltd. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23620229','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23620229"><span>Modelling the regulation of telomere length: the effects of telomerase and G-quadruplex <span class="hlt">stabilising</span> drugs.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hirt, Bartholomäus V; Wattis, Jonathan A D; Preston, Simon P</p> <p>2014-05-01</p> <p>Telomeres are guanine-rich sequences at the end of chromosomes which shorten during each replication event and trigger cell cycle arrest and/or controlled death (apoptosis) when reaching a threshold length. The enzyme telomerase replenishes the ends of telomeres and thus prolongs the life span of cells, but also causes cellular immortalisation in human cancer. G-quadruplex (G4) <span class="hlt">stabilising</span> drugs are a potential anticancer treatment which work by changing the molecular structure of telomeres to inhibit the activity of telomerase. We investigate the dynamics of telomere length in different conformational states, namely t-loops, G-quadruplex structures and those being elongated by telomerase. By formulating deterministic differential equation models we study the effects of various levels of both telomerase and concentrations of a G4-<span class="hlt">stabilising</span> drug on the distribution of telomere lengths, and analyse how these effects evolve over large numbers of cell generations. As well as calculating numerical solutions, we use quasicontinuum methods to approximate the behaviour of the system over time, and predict the shape of the telomere length distribution. We find those telomerase and G4-concentrations where telomere length maintenance is successfully regulated. Excessively high levels of telomerase lead to continuous telomere lengthening, whereas large concentrations of the drug lead to progressive telomere erosion. Furthermore, our models predict a positively skewed distribution of telomere lengths, that is, telomeres accumulate over lengths shorter than the mean telomere length at equilibrium. Our model results for telomere length distributions of telomerase-positive cells in drug-free assays are in good agreement with the limited amount of experimental data available.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27235522','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27235522"><span>Dynamic intraligamentary <span class="hlt">stabilisation</span>: initial experience with treatment of acute ACL ruptures.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kohl, S; Evangelopoulos, D S; Schär, M O; Bieri, K; Müller, T; Ahmad, S S</p> <p>2016-06-01</p> <p>The purpose of this study was to report the experience of dynamic intraligamentary <span class="hlt">stabilisation</span> (DIS) using the Ligamys device for the treatment of acute ruptures of the anterior cruciate ligament (ACL). Between March 2011 and April 2012, 50 patients (34 men and 16 women) with an acute rupture of the ACL underwent primary repair using this device. The mean age of the patients was 30 years (18 to 50). Patients were evaluated for laxity, stability, range of movement (ROM), Tegner, Lysholm, International Knee Documentation Committee (IKDC) and visual analogue scale (VAS) scores over a follow-up period of two years. At final follow-up, anteroposterior translation differed from the normal knee by a mean of 0.96 mm (-2 mm to 6 mm). Median (interquartile range) IKDC, Tegner, Lysholm and VAS scores were 98 (95 to 100), 6 (5 to 7), 100 (98 to 100) and 10 (9 to 10), respectively. Pre-injury Tegner activity levels were reached one year post-operatively. A total of nine patients (18%) required a secondary intervention; five developed instability, of whom four underwent secondary hamstring reconstructive surgery, and five required arthroscopic treatment for intra-articular impingement due to scar tissue which caused a fixed flexion deformity. In addition, 30 patients (60%) required removal of the tibial screw. While there was a high rate of secondary interventions, 45 patients (90%) retained their repaired ACL two years post-operatively, with good clinical scores and stability of the knee. Dynamic intraligamentary <span class="hlt">stabilisation</span> presents a promising treatment option for acute ACL ruptures, eliminating the need for ACL reconstruction. Cite this article: Bone Joint J 2016;98-B:793-8. ©2016 The British Editorial Society of Bone & Joint Surgery.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24675994','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24675994"><span>Emulsions <span class="hlt">stabilised</span> by whey protein microgel particles: towards food-grade Pickering emulsions.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Destribats, Mathieu; Rouvet, Martine; Gehin-Delval, Cécile; Schmitt, Christophe; Binks, Bernard P</p> <p>2014-09-28</p> <p>We have investigated a new class of food-grade particles, whey protein microgels, as <span class="hlt">stabilisers</span> of triglyceride-water emulsions. The sub-micron particles stabilized oil-in-water emulsions at all pH with and without salt. All emulsions creamed but exhibited exceptional resistance to coalescence. Clear correlations exist between the properties of the microgels in aqueous dispersion and the resulting emulsion characteristics. For conditions in which the particles were uncharged, fluid emulsions with relatively large drops were <span class="hlt">stabilised</span>, whereas emulsions stabilized by charged particles contained smaller flocculated drops. A combination of optical microscopy of the drops and spectrophotometry of the resolved aqueous phase allowed us to estimate the interfacial adsorption densities of the particles using the phenomenon of limited coalescence. We deduce two classes of particle arrangement. Complete adsorption of the particles was obtained when they were neutral or when their charges were screened by salt resulting in at least one particle monolayer at the interface. By contrast, only around 50% of the particles adsorbed when they were charged with emulsion drops being covered by less than half a monolayer. These findings were supported by direct visualization of drop interfaces using cryo-scanning electron microscopy. Uncharged particles were highly aggregated and formed a continuous 2-D network at the interface. Otherwise particles organized as individual aggregates separated by particle-free regions. In this case, we suggest that some particles spread at the interface leading to the formation of a continuous protein membrane. Charged particles displayed the ability to bridge opposing interfaces of neighbouring drops to form dense particle disks protecting drops against coalescence; this is the main reason for the flocculation and stability of emulsions containing sparsely covered drops.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17591219','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17591219"><span>Biogas production from anaerobic waste <span class="hlt">stabilisation</span> ponds treating dairy and piggery wastewater in New Zealand.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Park, J B K; Craggs, R J</p> <p>2007-01-01</p> <p>New Zealand has over 1000 anaerobic wastewater <span class="hlt">stabilisation</span> ponds used for the treatment of wastewater from farms and industry. Traditional anaerobic ponds were not designed to optimise anaerobic digestion of wastewater biomass to produce biogas and these uncovered ponds allowed biogas to escape to the atmosphere. This release of biogas not only causes odour problems, but contributes to GHG (greenhouse gas) emissions and is wasteful of energy that could be captured and used. Biogas production from anaerobic <span class="hlt">stabilisation</span> ponds treating piggery and dairy wastewater was measured using floating 25 m2 HDPE covers on the pond surface. Biogas composition was analysed monthly and gas production was continually monitored. Mean areal biogas (methane) production rates from piggery and dairy anaerobic ponds were 0.78 (0.53) m3/m2/d and 0.03 (0.023) m3/m2/d respectively. Average CH4 content of the piggery and dairy farm biogas were 72.0% and 80.3% respectively. Conversion of the average volume of methane gas that could be captured from the piggery and dairy farm ponds (393.4 m3/d and 40.7 m3/d) to electricity would reduce CO2 equivalent GHG emissions by 5.6 tonnes/d and 0.6 tonnes/d and generate 1,180 kWh/d and 122 kWh/d. These results suggest that anaerobic ponds in New Zealand release considerable amounts of GHG and that there is great potential for energy recovery.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1729111','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1729111"><span><span class="hlt">Stabilisation</span> of medically refractory ventricular arrhythmia by intra-aortic balloon counterpulsation</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Fotopoulos, G; Mason, M; Walker, S; Jepson, N; Patel, D; Mitchell, A; Ilsley, C; Paul, V</p> <p>1999-01-01</p> <p>OBJECTIVE—To review the efficacy of intra-aortic balloon counterpulsation (IABCP) in medically refractory ventricular arrhythmia.
DESIGN—Retrospective analysis of the outcome of patients with ventricular arrhythmia treated with IABCP after transfer between 1992 and 1997.
SETTING—Tertiary cardiac referral centre.
PATIENTS—21 patients (mean age 58 years) who underwent IABCP for control of ventricular arrhythmia. All had significant left ventricular impairment (mean ejection fraction 28.6%); 18 had coronary artery disease.
RESULTS—Before IABCP, 10 patients had incessant monomorphic ventricular tachycardia and 11 had paroxysmal ventricular tachycardia and/or ventricular fibrillation (VT/VF). IABCP resulted in suppression of ventricular arrhythmia in 18 patients, of whom 13 were weaned from IABCP. After <span class="hlt">stabilisation</span> of ventricular arrhythmia, 10 patients were maintained on medical treatment alone and one underwent endocardial resection. IABCP was maintained until cardiac transplantation in five patients. One patient had a fatal arrest before discharge and one died from progressive heart failure. IABCP failed to control ventricular arrhythmia in three patients and was subsequently discontinued. A cardiac assist device was employed in one of these until cardiac transplantation; the other two were eventually <span class="hlt">stabilised</span> on medical treatment. Nineteen patients were discharged from hospital. Overall survival was 95% at mean follow up of 25.7 months.
CONCLUSIONS—IABCP can be an effective means of controlling refractory ventricular arrhythmia, allowing time for the institution of more definitive treatment.


Keywords: ventricular arrhythmia; intra-aortic balloon counterpulsation PMID:10377318</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27693736','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27693736"><span>Production of nabumetone nanoparticles: Effect of molecular weight, concentration and nature of cellulose ether <span class="hlt">stabiliser</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Goodwin, D J; Martini, L G; Lawrence, M J</p> <p>2016-12-05</p> <p>The ability of a range of hydrophilic nonionic cellulose ethers (CEs) (namely methylhydroxethylcellulose, hydroxypropylmethylcellulose, ethylhydroxyethylcellulose, hydroxyethylcellulose and hydroxypropylcellulose) to prepare stable nabumetone nanoparticles (<1000nm, as measured by laser diffraction) using wet-bead milling has been investigated. Due to the limited range of CE molecular weights commercially available, the CEs were degraded using ultrasonication for varying lengths of time to yield CEs of lower molecular weight. Of the CEs tested, only hydroxyethylcellulose was found not to <span class="hlt">stabilise</span> the production of nabumetone nanoparticles at any of the molecular weights tested, namely viscosity average molecular weights (Mv) in the range of 236-33kg/mol. All other CEs successfully <span class="hlt">stabilised</span> nabumetone nanoparticles, with the lower molecular weight/viscosity polymers within a series being more likely to result in nanoparticle production than their higher molecular weight counterparts. Unfortunately due to the nature of the ultrasonication process, it was not possible to compare the size of nabumetone particles produced using polymers of identical Mv. There was, however, enough similarity in the Mv of the various polymers to draw the general conclusion that there was no strong correlation between the Mv of the various polymers and their ability to produce nanoparticles. For example hydroxypropylcellulose of 112.2kg/mol or less successfully produced nanoparticles while only ethylhydroxyethylcellulose and hydroxypropylmethyl polymers of 52 and 38.8kg/mol or less produced nanoparticles. These results suggest that polymer molecular weight is not the only determinant of nanoparticle production and that structure of the polymer is at least as important as its molecular weight. In particular the hydrophobic nature of the CE was thought to be an important factor in the production of nabumetone nanoparticles: the more hydrophobic the polymer, the stronger its interaction</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014A%26A...561A..59Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014A%26A...561A..59Z"><span>Flat-relative optimal extraction. A quick and efficient algorithm for <span class="hlt">stabilised</span> spectrographs</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zechmeister, M.; Anglada-Escudé, G.; Reiners, A.</p> <p>2014-01-01</p> <p>Context. Optimal extraction is a key step in processing the raw images of spectra as registered by two-dimensional detector arrays to a one-dimensional format. Previously reported algorithms reconstruct models for a mean one-dimensional spatial profile to assist a properly weighted extraction. Aims: We outline a simple optimal extraction algorithm (including error propagation), which is very suitable for <span class="hlt">stabilised</span>, fibre-fed spectrographs and does not model the spatial profile shape. Methods: A high signal-to-noise ratio, master-flat image serves as reference image and is directly used as an extraction profile mask. Each extracted spectral value is the scaling factor relative to the cross-section of the unnormalised master flat that contains all information about the spatial profile, as well as pixel-to-pixel variations, fringing, and blaze. The extracted spectrum is measured relative to the flat spectrum. Results: Using echelle spectra of the HARPS spectrograph we demonstrate a competitive extraction performance in terms of a signal-to-noise ratio and show that extracted spectra can be used for high precision radial velocity measurement. Conclusions: Pre- or post-flat-fielding of the data is not necessary, since all spectrograph inefficiencies inherent to the extraction mask are automatically accounted for. Also the reconstruction of the mean spatial profile by models is not needed, thereby reducing the number of operations to extract spectra. Flat-relative optimal extraction is a simple, efficient, and robust method that can be applied easily to <span class="hlt">stabilised</span>, fibre-fed spectrographs. Based on data obtained from the ESO Science Archive Facility under request number ZECHMEISTER73978. Based on observations made with the HARPS instrument on the ESO 3.6 m telescope under programme ID 074.D-0380.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=558090','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=558090"><span>Randomised controlled trial to compare surgical <span class="hlt">stabilisation</span> of the lumbar spine with an intensive rehabilitation programme for patients with chronic low back pain: the MRC spine <span class="hlt">stabilisation</span> trial</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Fairbank, Jeremy; Frost, Helen; Wilson-MacDonald, James; Yu, Ly-Mee; Barker, Karen; Collins, Rory</p> <p>2005-01-01</p> <p>Objectives To assess the clinical effectiveness of surgical <span class="hlt">stabilisation</span> (spinal fusion) compared with intensive rehabilitation for patients with chronic low back pain. Design Multicentre randomised controlled trial. Setting 15 secondary care orthopaedic and rehabilitation centres across the United Kingdom. Participants 349 participants aged 18-55 with chronic low back pain of at least one year's duration who were considered candidates for spinal fusion. Intervention Lumbar spine fusion or an intensive rehabilitation programme based on principles of cognitive behaviour therapy. Main outcome measure The primary outcomes were the Oswestry disability index and the shuttle walking test measured at baseline and two years after randomisation. The SF-36 instrument was used as a secondary outcome measure. Results 176 participants were assigned to surgery and 173 to rehabilitation. 284 (81%) provided follow-up data at 24 months. The mean Oswestry disability index changed favourably from 46.5 (SD 14.6) to 34.0 (SD 21.1) in the surgery group and from 44.8 (SD14.8) to 36.1 (SD 20.6) in the rehabilitation group. The estimated mean difference between the groups was –4.1 (95% confidence interval –8.1 to –0.1, P = 0.045) in favour of surgery. No significant differences between the treatment groups were observed in the shuttle walking test or any of the other outcome measures. Conclusions Both groups reported reductions in disability during two years of follow-up, possibly unrelated to the interventions. The statistical difference between treatment groups in one of the two primary outcome measures was marginal and only just reached the predefined minimal clinical difference, and the potential risk and additional cost of surgery also need to be considered. No clear evidence emerged that primary spinal fusion surgery was any more beneficial than intensive rehabilitation. PMID:15911537</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015eheu.conf....8P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015eheu.conf....8P"><span>The Athena <span class="hlt">Background</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Piro, Luigi; Lotti, Simone; Macculi, Claudio; Molendi, Silvano; Eraerds, Tanja; Laurent, Philippe</p> <p>2015-09-01</p> <p>Estimating, reducing and controlling the residual particle <span class="hlt">background</span> is fundamental for achieving the objectives of several science topics of Athena, in particular those connected with <span class="hlt">background</span> dominated observations of faint and/or diffuse sources. This requires assessing the particle environment in L2, propagating the various particle components throughout the mirror, spacecraft, and instruments via proper modelling and simulations of various physical processes, implementing design and h/w measures at instrument and mission level to reduce the un-rejected <span class="hlt">background</span> and identifying proper calibration methods to control the <span class="hlt">background</span> variations. Likewise, an adequate knowledge of the XRB, made of components that may vary spatially or temporally, is required as well. Here we will review the present status of the <span class="hlt">background</span> knowledge, and summarize the activities on-going within Athena at various levels.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21259853','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21259853"><span>Correlators in nontrivial <span class="hlt">backgrounds</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mello Koch, Robert de; Ives, Norman; Stephanou, Michael</p> <p>2009-01-15</p> <p>Operators in N=4 super Yang-Mills theory with an R-charge of O(N{sup 2}) are dual to <span class="hlt">backgrounds</span> which are asymtotically AdS{sub 5}xS{sup 5}. In this article we develop efficient techniques that allow the computation of correlation functions in these <span class="hlt">backgrounds</span>. We find that (i) contractions between fields in the string words and fields in the operator creating the <span class="hlt">background</span> are the field theory accounting of the new geometry, (ii) correlation functions of probes in these <span class="hlt">backgrounds</span> are given by the free field theory contractions but with rescaled propagators and (iii) in these <span class="hlt">backgrounds</span> there are no open string excitations with their special end point interactions; we have only closed string excitations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2002AGUFM.A51C0070T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2002AGUFM.A51C0070T"><span>A Generalized <span class="hlt">Convective</span> Inhibition Energy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tailleux, R.</p> <p>2002-12-01</p> <p>The common view about preconvecting soundings is that they possess both CAPE (<span class="hlt">Convective</span> Available Potential Energy) and CINE (<span class="hlt">Convective</span> INhibition Energy), the latter preventing the former to be spontaneously released. The two concepts of CAPE and CINE are ambiguous, however, because they depend upon the parcel used to compute the work of buoyancy forces, as well as upon the thermodynamic transformation (adiabatic, pseudo-adiabatic) assumed in lifting the parcel. To remove the ambiguity intrinsically associated with CAPE, Randall and Wang (1992) introduced the concept of GCAPE (Generalized CAPE), defined as the minimum achievable energy difference between the total nonkinetic energy (NKE) of the column of air considered minus the total NKE of a reference soundings obtained by reorganizing the parcels along the vertical by conserving mass. Because the method focuses on how to achieve a global energy minimum without addressing the issue of whether it is achievable or how to achieve it, the concept of CINE is lost. The present work shows how to remedy to this problem, and how to define a Generalized CINE within the same framework serving to define the GCAPE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1992PhFlA...4.2715B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1992PhFlA...4.2715B"><span>Structure in turbulent thermal <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Balachandar, S.</p> <p>1992-12-01</p> <p>Small-scale features of vorticity, strain rate, and temperature gradients are considered in a Rayleigh-Bénard <span class="hlt">convection</span>. The results reported are from a direct numerical simulation of turbulent <span class="hlt">convection</span> performed in a rectangular box of aspect ratio 2√2 at a Rayleigh number of 6.5×106 and a Prandtl number of 0.72. In agreement with earlier results [Ashurst et al., Phys. Fluids 30, 2343 (1987) and Ruetsch and Maxey, Phys. Fluids A 3, 1587 (1991)], the intermediate strain rate is on an average positive, but the ratio of alpha, beta, and gamma strain rates are measured to be 5.3:1.0:-6.3. This result differs from the earlier result of 3:1:-4 obtained in homogeneous isotropic and shear turbulences. Buoyancy-induced vorticity production makes significant contribution to the overall enstrophy balance, especially close to the boundaries. Vorticity production by buoyancy is exclusively in the horizontal direction and is balanced by preferred production by stretching and tilting in the vertical direction, due to the preferred alignment of extensional alpha strain rate with the vertical direction. Such directional alignment of vorticity, strain rate, and scalar gradient is explained on the basis of preferred spatial orientation of coherent structures in thermal turbulence.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17677562','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17677562"><span>Marangoni <span class="hlt">convection</span> in binary mixtures.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Jie; Behringer, Robert P; Oron, Alexander</p> <p>2007-07-01</p> <p>Marangoni instabilities in binary mixtures in the presence of the Soret effect and evaporation are different from those in pure liquids. In contrast to a large amount of experimental work on Marangoni <span class="hlt">convection</span> in pure liquids, such experiments in binary mixtures are not available in the literature, to our knowledge. Using binary mixtures of NaCl/water in an open system, evaporation of water molecules at the liquid-vapor interface is inevitable. We have systematically investigated the pattern formation for a set of substrate temperatures and solute concentrations in an open system. The flow patterns evolve with time, driven by surface-tension fluctuations due to evaporation and the Soret effect, while the air-liquid interface does not deform. A shadow-graph method is used to follow the pattern formation in time. The patterns are mainly composed of polygons and rolls. The mean pattern size first decreases slightly, and then gradually increases during the evolution. Evaporation affects the pattern formation mainly at the early stages and the local evaporation rate tends to become spatially uniform at the film surface. The Soret effect becomes important at the later stages and affects the mixture for a large mean solute concentration where the Soret number is significantly above zero. The strength of <span class="hlt">convection</span> increases with the initial solute concentration and the substrate temperature. Our findings differ from the theoretical predictions in which evaporation is neglected.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.A51F3098K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.A51F3098K"><span>Shallow <span class="hlt">Convection</span> along the Sea Breeze Front and its Interaction with Horizontal <span class="hlt">Convective</span> Rolls and <span class="hlt">Convective</span> Cells</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Khan, B. A.; Stenchikov, G. L.; Abualnaja, Y.</p> <p>2014-12-01</p> <p>Shallow <span class="hlt">convection</span> has been studied in the sea breeze frontal zone along the Arabian Red Sea coast. This <span class="hlt">convection</span> is forced by thermal and dynamic instabilities and generally is capped below 500 hPa. The thermally induced sea breeze modifies the desert Planetary Boundary Layer (PBL) and propagates inland as a density current. The leading edge of the denser marine air rapidly moves inland undercutting the hot and dry desert air mass. The warm air lifts up along the sea breeze front (SBF). Despite large moisture flux from the sea, the shallow <span class="hlt">convection</span> in SBF does not cause precipitation on the most part of the Arabian coastal plane. The main focus of this research is to study the vertical structure and extent of <span class="hlt">convective</span> activity in SBF and to differentiate flow regimes that lead to dry and wet <span class="hlt">convection</span>. The Weather Research and Forecasting Model (WRF) has been employed at a high spatial resolution of 500 m to investigate the thermodynamic structure of the atmospheric column along the SBF. We found that <span class="hlt">convection</span> occurs during offshore and cross-shore mean wind conditions; precipitation in SBF frequently develops in the southern region of the Red Sea along the high terrain of Al-Sarawat Mountains range, while on most of the days <span class="hlt">convection</span> is dry in the middle region and further north of the Red Sea. The coherent structures in the PBL, horizontal <span class="hlt">convective</span> rolls (HCRs) and open <span class="hlt">convective</span> cells (OCCs), play an important role shaping interaction of SBF with the desert boundary layer. The HCRs develop in the midmorning along the mean wind vector and interact with the SBF. Later in the afternoon HCRs evolve into OCCs. The <span class="hlt">convection</span> is strongest, where the HCR and OCC updrafts overlap with SBF and is weakest in their downdraft regions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000114843','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000114843"><span>A Texture-Polarization Method for Estimating <span class="hlt">Convective</span>/Stratiform Precipitation Area Coverage from Passive Microwave Radiometer Data</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Olson, William S.; Hong, Ye; Kummerow, Christian D.; Turk, Joseph; Einaudi, Franco (Technical Monitor)</p> <p>2000-01-01</p> <p>Observational and modeling studies have described the relationships between <span class="hlt">convective</span>/stratiform rain proportion and the vertical distributions of vertical motion, latent heating, and moistening in mesoscale <span class="hlt">convective</span> systems. Therefore, remote sensing techniques which can quantify the relative areal proportion of <span class="hlt">convective</span> and stratiform, rainfall can provide useful information regarding the dynamic and thermodynamic processes in these systems. In the present study, two methods for deducing the <span class="hlt">convective</span>/stratiform areal extent of precipitation from satellite passive microwave radiometer measurements are combined to yield an improved method. If sufficient microwave scattering by ice-phase precipitating hydrometeors is detected, the method relies mainly on the degree of polarization in oblique-view, 85.5 GHz radiances to estimate the area fraction of <span class="hlt">convective</span> rain within the radiometer footprint. In situations where ice scattering is minimal, the method draws mostly on texture information in radiometer imagery at lower microwave frequencies to estimate the <span class="hlt">convective</span> area fraction. Based upon observations of ten <span class="hlt">convective</span> systems over ocean and nine systems over land, instantaneous 0.5 degree resolution estimates of <span class="hlt">convective</span> area fraction from the Tropical Rainfall Measuring Mission Microwave Imager (TRMM TMI) are compared to nearly coincident estimates from the TRMM Precipitation Radar (TRMM PR). The TMI <span class="hlt">convective</span> area fraction estimates are slightly low-biased with respect to the PR, with TMI-PR correlations of 0.78 and 0.84 over ocean and land <span class="hlt">backgrounds</span>, respectively. TMI monthly-average <span class="hlt">convective</span> area percentages in the tropics and subtropics from February 1998 exhibit the greatest values along the ITCZ and in continental regions of the summer (southern) hemisphere. Although <span class="hlt">convective</span> area percentages. from the TMI are systematically lower than those from the PR, monthly rain patterns derived from the TMI and PR rain algorithms are very similar</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016DyAtO..73...10Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016DyAtO..73...10Y"><span>Generalized <span class="hlt">convective</span> quasi-equilibrium principle</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yano, Jun-Ichi; Plant, Robert S.</p> <p>2016-03-01</p> <p>A generalization of Arakawa and Schubert's <span class="hlt">convective</span> quasi-equilibrium principle is presented for a closure formulation of mass-flux <span class="hlt">convection</span> parameterization. The original principle is based on the budget of the cloud work function. This principle is generalized by considering the budget for a vertical integral of an arbitrary <span class="hlt">convection</span>-related quantity. The closure formulation includes Arakawa and Schubert's quasi-equilibrium, as well as both CAPE and moisture closures as special cases. The formulation also includes new possibilities for considering vertical integrals that are dependent on <span class="hlt">convective</span>-scale variables, such as the moisture within <span class="hlt">convection</span>. The generalized <span class="hlt">convective</span> quasi-equilibrium is defined by a balance between large-scale forcing and <span class="hlt">convective</span> response for a given vertically-integrated quantity. The latter takes the form of a convolution of a kernel matrix and a mass-flux spectrum, as in the original <span class="hlt">convective</span> quasi-equilibrium. The kernel reduces to a scalar when either a bulk formulation is adopted, or only large-scale variables are considered within the vertical integral. Various physical implications of the generalized closure are discussed. These include the possibility that precipitation might be considered as a potentially-significant contribution to the large-scale forcing. Two dicta are proposed as guiding physical principles for the specifying a suitable vertically-integrated quantity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=convection&pg=2&id=EJ829061','ERIC'); return false;" href="http://eric.ed.gov/?q=convection&pg=2&id=EJ829061"><span>Introductory Analysis of Benard-Marangoni <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Maroto, J. A.; Perez-Munuzuri, V.; Romero-Cano, M. S.</p> <p>2007-01-01</p> <p>We describe experiments on Benard-Marangoni <span class="hlt">convection</span> which permit a useful understanding of the main concepts involved in this phenomenon such as, for example, Benard cells, aspect ratio, Rayleigh and Marangoni numbers, Crispation number and critical conditions. In spite of the complexity of <span class="hlt">convection</span> theory, we carry out a simple and…</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6233487','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6233487"><span>Stationary <span class="hlt">convection</span> in a cylindrical plasma</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gomberoff, L.; Hernandez, M.</p> <p>1983-02-01</p> <p>It is shown that viscosity and thermal conductivity leads to large-scale steady <span class="hlt">convection</span> in a cylindrical current-carrying plasma, under the influence of a magnetic field satisfying (B/sub theta//B/sub z/)>>1. This state is the analog in a plasma of stationary <span class="hlt">convection</span> in ordinary hydrodynamics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=Cell+AND+theory&pg=6&id=EJ829061','ERIC'); return false;" href="https://eric.ed.gov/?q=Cell+AND+theory&pg=6&id=EJ829061"><span>Introductory Analysis of Benard-Marangoni <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Maroto, J. A.; Perez-Munuzuri, V.; Romero-Cano, M. S.</p> <p>2007-01-01</p> <p>We describe experiments on Benard-Marangoni <span class="hlt">convection</span> which permit a useful understanding of the main concepts involved in this phenomenon such as, for example, Benard cells, aspect ratio, Rayleigh and Marangoni numbers, Crispation number and critical conditions. In spite of the complexity of <span class="hlt">convection</span> theory, we carry out a simple and…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDL10009G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDL10009G"><span>The parameter space of windy <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goluskin, David</p> <p>2016-11-01</p> <p>In horizontally periodic Rayleigh-Bénard <span class="hlt">convection</span> at large Rayleigh numbers (Ra), wavenumber-zero horizontal winds can arise spontaneously and dramatically alter the flow. The resulting "windy <span class="hlt">convection</span>" has been observed in 2D domains and horizontally anisotropic 3D domains. As Ra is raised, the fraction of total kinetic energy contained in the wind approaches 100%. Vertical heat transport is greatly depressed by the wind and grows very slowly (if at all) as Ra is raised. Two different types of windy <span class="hlt">convection</span> have been observed at different Prandtl numbers (Pr). At smaller Pr, heat is vertically <span class="hlt">convected</span> almost exclusively during discrete bursts that are separated by long quiescent phases. At larger Pr, <span class="hlt">convective</span> transport remains significant at all times. <span class="hlt">Convection</span> can thus be identified as either windy or non-windy, and windy states can be either bursting or non-bursting. The regions of the Ra-Pr parameter plane in which each type of <span class="hlt">convection</span> can occur remain poorly understood, as do transitions between these regions. This talk will summarize the phenomenon of windy <span class="hlt">convection</span> in 2D and 3D and present a preliminary exploration of the Ra-Pr plane in the 2D case. Partially supported by NSF award DMS-1515161.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A41F0117N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A41F0117N"><span>Extremely tall <span class="hlt">convection</span>: characteristics and controls</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Nesbitt, S. W.; Rasmussen, K. L.</p> <p>2015-12-01</p> <p>Tall continental <span class="hlt">convective</span> structures are observed in several climatological regions, and have been shown to be related with severe weather and extreme hydrologic events. Recent work has defined tall <span class="hlt">convection</span> as regions with precipitation structures observed with spaceborne radar echo extending into the upper troposphere/lower stratosphere. While these climatological regions are known for these tall <span class="hlt">convective</span> structures (subtropical South America, equatorial Africa, southcentral USA, South Asia), not all observed <span class="hlt">convective</span> eventsin these regions contain strong structures, and the characteristics of the meteorological environments, including sounding profiles, that dictate the strength of the spectrum of <span class="hlt">convective</span> systems are poorly constrained. In this study, precipitation radar (PR) data from the Tropical Rainfall Measuring Mission (TRMM) and dual-frequency precipitation radar (DPR) from the Global Precipitation Measurement (GPM) satellites will be examined alongside composites of atmospheric reanalysis data to examine the structural and meteorological environments surrounding observed tall <span class="hlt">convective</span> systems. Environments of <span class="hlt">convective</span> systems of various vertical extents will be contrasted with less extreme <span class="hlt">convection</span> to infer physical causal mechanisms and to examine issues of predictability of these events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001APS..APR.B8009E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001APS..APR.B8009E"><span><span class="hlt">Background</span> Underground at WIPP</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Esch, Ernst-Ingo; Hime, A.; Bowles, T. J.</p> <p>2001-04-01</p> <p>Recent interest to establish a dedicated underground laboratory in the United States prompted an experimental program at to quantify the enviromental <span class="hlt">backgrounds</span> underground at the Waste Isolation Pilot Plant (WIPP) in Carlsbad, New Mexico. An outline of this program is provided along with recent experimental data on the cosmic ray muon flux at the 650 meter level of WIPP. The implications of the cosmic ray muon and fast neutron <span class="hlt">background</span> at WIPP will be discussed in the context of new generation, low <span class="hlt">background</span> experiments envisioned in the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930039657&hterms=neutrino&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dneutrino','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930039657&hterms=neutrino&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dneutrino"><span>The cosmic neutrino <span class="hlt">background</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Dar, Arnon</p> <p>1991-01-01</p> <p>The cosmic neutrino <span class="hlt">background</span> is expected to consist of relic neutrinos from the big bang, of neutrinos produced during nuclear burning in stars, of neutrinos released by gravitational stellar collapse, and of neutrinos produced by cosmic ray interactions with matter and radiation in the interstellar and intergalactic medium. Formation of baryonic dark matter in the early universe, matter-antimatter annihilation in a baryonic symmetric universe, and dark matter annihilation could have also contributed significantly to the cosmic neutrino <span class="hlt">background</span>. The purpose of this paper is to review the properties of these cosmic neutrino <span class="hlt">backgrounds</span>, the indirect evidence for their existence, and the prospects for their detection.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016Icar..278..180S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016Icar..278..180S"><span>A year of <span class="hlt">convective</span> vortex activity at Gale crater</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Steakley, Kathryn; Murphy, James</p> <p>2016-11-01</p> <p>Atmospheric <span class="hlt">convective</span> vortices, which become dust devils when they entrain dust from the surface, are prominent features within Mars' atmosphere which are thought to be a primary contributor to the planet's <span class="hlt">background</span> dust opacity. Buoyantly produced in <span class="hlt">convectively</span> unstable layers at a planet's surface, these vertically aligned vortices possess rapidly rotating and ascending near-surface warm air and are readily identified by temporal signatures of reduced atmospheric surface pressure measured within the vortex as it passes by. We investigate such signatures in surface pressure measurements acquired by the Rover Environmental Monitoring Station aboard the Mars Science Laboratory rover located within Gale crater. During the first 707 sols of the mission, 245 <span class="hlt">convective</span> vortices are identified with pressure drops in the range of 0.30-2.86 Pa with a median value of 0.67 Pa. The cumulative distribution of their pressure drops follows a power law of slope -2.77 and we observe seasonal and diurnal trends in their activity. The vast majority of these pressure signatures lack corresponding reductions in REMS-measured UV flux, suggesting that these vortices rarely cast shadows upon the rover and therefore are most often dust-free. The relatively weak-magnitude, dustless vortices at Gale crater are consistent with predictions from mesoscale modeling indicating that the planetary boundary layer is suppressed within the crater and are also consistent with the almost complete absence of both dust devils within Mars Science Laboratory camera images and Gale crater surface dust devil streaks within orbiter images.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JAMES...9.1488B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JAMES...9.1488B"><span>Imprint of the <span class="hlt">convective</span> parameterization and sea-surface temperature on large-scale <span class="hlt">convective</span> self-aggregation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Becker, Tobias; Stevens, Bjorn; Hohenegger, Cathy</p> <p>2017-06-01</p> <p>Radiative-<span class="hlt">convective</span> equilibrium simulations with the general circulation model ECHAM6 are used to explore to what extent the dependence of large-scale <span class="hlt">convective</span> self-aggregation on sea-surface temperature (SST) is driven by the <span class="hlt">convective</span> parameterization. Within the <span class="hlt">convective</span> parameterization, we concentrate on the entrainment parameter and show that large-scale <span class="hlt">convective</span> self-aggregation is independent of SST when the entrainment rate for deep <span class="hlt">convection</span> is set to zero or when the <span class="hlt">convective</span> parameterization is removed from the model. In the former case, <span class="hlt">convection</span> always aggregates very weakly, whereas in the latter case, <span class="hlt">convection</span> always aggregates very strongly. With a nontrivial representation of <span class="hlt">convective</span> entrainment, large-scale <span class="hlt">convective</span> self-aggregation depends nonmonotonically on SST. For SSTs below 295 K, <span class="hlt">convection</span> is more aggregated the smaller the SST because large-scale moisture convergence is relatively small, constraining <span class="hlt">convective</span> activity to regions with high wind-induced surface moisture fluxes. For SSTs above 295 K, <span class="hlt">convection</span> is more aggregated the higher the SST because entrainment is most efficient in decreasing updraft buoyancy at high SSTs, amplifying the moisture-<span class="hlt">convection</span> feedback. When halving the entrainment rate, <span class="hlt">convection</span> is less efficient in reducing updraft buoyancy, and <span class="hlt">convection</span> is less aggregated, in particular at high SSTs. Despite most early work on self-aggregation highlighted the role of nonconvective processes, we conclude that <span class="hlt">convective</span> self-aggregation and the global climate state are sensitive to the <span class="hlt">convective</span> parameterization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22251770','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22251770"><span>Collective phase description of oscillatory <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kawamura, Yoji; Nakao, Hiroya</p> <p>2013-12-15</p> <p>We formulate a theory for the collective phase description of oscillatory <span class="hlt">convection</span> in Hele-Shaw cells. It enables us to describe the dynamics of the oscillatory <span class="hlt">convection</span> by a single degree of freedom which we call the collective phase. The theory can be considered as a phase reduction method for limit-cycle solutions in infinite-dimensional dynamical systems, namely, stable time-periodic solutions to partial differential equations, representing the oscillatory <span class="hlt">convection</span>. We derive the phase sensitivity function, which quantifies the phase response of the oscillatory <span class="hlt">convection</span> to weak perturbations applied at each spatial point, and analyze the phase synchronization between two weakly coupled Hele-Shaw cells exhibiting oscillatory <span class="hlt">convection</span> on the basis of the derived phase equations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1330761','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1330761"><span>Natural <span class="hlt">convection</span> around the human head.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Clark, R P; Toy, N</p> <p>1975-01-01</p> <p>1. Factors determining the <span class="hlt">convective</span> flow patterns around the human head in 'still' conditions are discussed in relation to body posture. 2. The flow patterns have been visualized using a schlieren optical system which reveals that the head has a thicker 'insulating' layer of <span class="hlt">convecting</span> air in the erect posture than in the supine position. 3. Local <span class="hlt">convective</span> and radiative heat transfer measurements from the head have been using surface calorimeters. These results are seen to be closely related to the thickness of the <span class="hlt">convective</span> boundary layer flows. 4. The total <span class="hlt">convective</span> and radiative heat loss from the head of a subject in the erect and supine position has been evaluated from the local measurements. For the head of the supine subject the heat loss was found to be 30% more than when the subject was standing. Images Plate 1 PMID:1142118</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016APS..DFDG10005L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016APS..DFDG10005L"><span>The Turbulent Diffusivity of <span class="hlt">Convective</span> Overshoot</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lecoanet, Daniel; Schwab, Josiah; Quataert, Eliot; Bildsten, Lars; Timmes, Frank; Burns, Keaton; Vasil, Geoffrey; Oishi, Jeffrey; Brown, Benjamin</p> <p>2016-11-01</p> <p>There are many natural systems with <span class="hlt">convectively</span> unstable fluid adjacent to stably stratified fluid; including the Earth's atmosphere, most stars, and perhaps even the Earth's liquid core. The <span class="hlt">convective</span> motions penetrating into the stable region can enhance mixing, leading to changes in transport within the stable region. This work describes <span class="hlt">convective</span> overshoot simulations. To study the extra mixing due to overshoot, we evolve a passive tracer field. The horizontal average of the passive tracer quickly approaches a self-similar state. The self-similar state is the solution to a diffusion equation with a spatially dependent turbulent diffusivity. We find the extra mixing due to <span class="hlt">convection</span> can be accurately modeled as a turbulent diffusivity, and discuss implications of this turbulent diffusivity for the astrophysical problem of mixing in <span class="hlt">convectively</span> bounded carbon flames.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EPJST.223...99K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EPJST.223...99K"><span>Spatial localization in rotating <span class="hlt">convection</span> and magnetoconvection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kao, H.-C.; Knobloch, E.</p> <p>2014-01-01</p> <p>Stationary spatially localized states are present in both rotating <span class="hlt">convection</span> and magnetoconvection. In two-dimensional <span class="hlt">convection</span> with stress-free boundary conditions, the formation of such states is due to the interaction between <span class="hlt">convection</span> and a large scale mode: zonal velocity in rotating <span class="hlt">convection</span> and magnetic potential in magnetoconvection. We develop a higher order theory, a nonlocal fifth order Ginzburg-Landau equation, to describe the effects of spatial modulation near a codimension-two point. Two different bifurcation scenarios are identified. Our results shed light on numerical studies of two-dimensional <span class="hlt">convective</span> systems with stress-free boundary conditions. This paper is dedicated to Professor Helmut Brand on the occasion of his 60th birthday.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950046656&hterms=Fermi+Enrico&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DFermi%252C%2BEnrico','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950046656&hterms=Fermi+Enrico&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DFermi%252C%2BEnrico"><span>Magnetospheric <span class="hlt">convection</span> pattern and its implications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Zhu, Xiaoming</p> <p>1993-01-01</p> <p>When we use 14 months of the Fast Plasma Experiment ion velocity measurements, the mean magnetospheric circulation pattern is constructed. It is shown that the magnetospheric <span class="hlt">convection</span> velocity is of the order tens of kilometers per second. The <span class="hlt">convection</span> is largely restricted to the outer magnetosphere. During magnetically active periods the <span class="hlt">convection</span> velocity increases and the <span class="hlt">convection</span> boundary extends to the region closer to the Earth, indicating more magnetic field flux is being transported to the dayside magnetosphere. It is also shown that the <span class="hlt">convective</span> flows tend to follow contours of constant unit flux volume as they move around the Earth, especially on the duskside of the magnetosphere. This helps to avoid the pressure balance inconsistency often found in two-dimensional magnetotail models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..1713651Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..1713651Z"><span>Nature, theory and modelling of geophysical <span class="hlt">convective</span> planetary boundary layers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zilitinkevich, Sergej</p> <p>2015-04-01</p> <p> horizontal branches of organised structures. This mechanism (Zilitinkevich et al., 2006), was overlooked in conventional local theories, such as the Monin-Obukhov similarity theory, and <span class="hlt">convective</span> heat/mass transfer law: Nu~Ra1/3, where Nu and Ra are the Nusselt number and Raleigh numbers. References Hellsten A., Zilitinkevich S., 2013: Role of <span class="hlt">convective</span> structures and <span class="hlt">background</span> turbulence in the dry <span class="hlt">convective</span> boundary layer. Boundary-Layer Meteorol. 149, 323-353. Zilitinkevich, S.S., 1973: Shear <span class="hlt">convection</span>. Boundary-Layer Meteorol. 3, 416-423. Zilitinkevich, S.S., 1991: Turbulent Penetrative <span class="hlt">Convection</span>, Avebury Technical, Aldershot, 180 pp. Zilitinkevich S.S., 2012: The Height of the Atmospheric Planetary Boundary layer: State of the Art and New Development - Chapter 13 in 'National Security and Human Health Implications of Climate Change', edited by H.J.S. Fernando, Z. Klaić, J.L. McKulley, NATO Science for Peace and Security Series - C: Environmental Security (ISBN 978-94-007-2429-7), Springer, 147-161. Zilitinkevich S.S., 2013: Atmospheric Turbulence and Planetary Boundary Layers. Fizmatlit, Moscow, 248 pp. Zilitinkevich, S.S., Hunt, J.C.R., Grachev, A.A., Esau, I.N., Lalas, D.P., Akylas, E., Tombrou, M., Fairall, C.W., Fernando, H.J.S., Baklanov, and A., Joffre, S.M., 2006: The influence of large <span class="hlt">convective</span> eddies on the surface layer turbulence. Quart. J. Roy. Met. Soc. 132, 1423-1456. Zilitinkevich S.S., Tyuryakov S.A., Troitskaya Yu. I., Mareev E., 2012: Theoretical models of the height of the atmospheric planetary boundary layer and turbulent entrainment at its upper boundary. Izvestija RAN, FAO, 48, No.1, 150-160 Zilitinkevich, S.S., Elperin, T., Kleeorin, N., Rogachevskii, I., Esau, I.N., 2013: A hierarchy of energy- and flux-budget (EFB) turbulence closure models for stably stratified geophysical flows. Boundary-Layer Meteorol. 146, 341-373.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012PhDT.......274G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012PhDT.......274G"><span>Low Mach Number Simulation of Core <span class="hlt">Convection</span> in Massive Stars</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gilet, Candace Elise</p> <p></p> <p>This work presents three-dimensional simulations of core <span class="hlt">convection</span> in a 15 solar mass star halfway through its main sequence lifetime. We examine the effects of two common modeling choices on the resulting <span class="hlt">convective</span> flow: using a reduced domain size and using a monatomic, or single species, approximation. We compare a multi-species simulation on a full sphere (360 degree) domain with a multi-species simulation on an octant domain and also with a single species simulation on a full sphere domain. To perform the long-time calculations, we use the new low Mach number code MAESTRO. The first part of this work deals with numerical aspects of using MAESTRO for the core <span class="hlt">convection</span> system, a new application for MAESTRO. We extend MAESTRO to include two new models, a single species model and a simplified two-dimensional planar model, to aid in the exploration of using MAESTRO for core <span class="hlt">convection</span> in massive stars. We discuss using MAESTRO with a novel spherical geometry domain configuration, namely, with the outer boundary located in the interior of the star, and show how this can create spurious velocities that must be numerically damped using a sponging layer. We describe the preparation of the initial model for the simulation. We find that assuring neutral stratification in the <span class="hlt">convective</span> core and reasonable resolution of the gravity waves in the stable layer are key factors in generating suitable initial conditions for the simulation. Further, we examine a numerical aspect of the velocity constraint that is part of the low Mach number formulation of the Euler equations. In particular, we investigate the numerical procedure for computing beta0, the density-like variable that captures <span class="hlt">background</span> stratification in the velocity constraint, and find that the original method of computation remains a good choice. The three-dimensional simulation results show that using a single species model actually increases the computational cost of the simulation because the single</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21067314','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21067314"><span>The GLAST <span class="hlt">Background</span> Model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ormes, J. F.; Atwood, W.; Burnett, T.; Grove, E.; Longo, F.; McEnery, J.; Ritz, S.; Mizuno, T.</p> <p>2007-07-12</p> <p>In order to estimate the ability of the GLAST/LAT to reject unwanted <span class="hlt">background</span> of charged particles, optimize the on-board processing, size the required telemetry and optimize the GLAST orbit, we developed a detailed model of the <span class="hlt">background</span> particles that would affect the LAT. In addition to the well-known components of the cosmic radiation, we included splash and reentrant components of protons, electrons (e+ and e-) from 10 MeV and beyond as well as the albedo gamma rays produced by cosmic ray interactions with the atmosphere. We made estimates of the irreducible <span class="hlt">background</span> components produced by positrons and hadrons interacting in the multilayered micrometeorite shield and spacecraft surrounding the LAT and note that because the orbital debris has increased, the shielding required and hence the <span class="hlt">background</span> are larger than were present in EGRET. Improvements to the model are currently being made to include the east-west effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/918037','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/918037"><span>The GLAST <span class="hlt">Background</span> Model</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ormes, J.F.; Atwood, W.; Burnett, T.; Grove, E.; Longo, F.; McEnery, J.; Mizuno, T.; Ritz, S.; /NASA, Goddard</p> <p>2007-10-17</p> <p>In order to estimate the ability of the GLAST/LAT to reject unwanted <span class="hlt">background</span> of charged particles, optimize the on-board processing, size the required telemetry and optimize the GLAST orbit, we developed a detailed model of the <span class="hlt">background</span> particles that would affect the LAT. In addition to the well-known components of the cosmic radiation, we included splash and reentrant components of protons, electrons (e+ and e-) from 10 MeV and beyond as well as the albedo gamma rays produced by cosmic ray interactions with the atmosphere. We made estimates of the irreducible <span class="hlt">background</span> components produced by positrons and hadrons interacting in the multilayered micrometeorite shield and spacecraft surrounding the LAT and note that because the orbital debris has increased, the shielding required and hence the <span class="hlt">background</span> are larger than were present in EGRET. Improvements to the model are currently being made to include the east-west effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.epa.gov/office-inspector-general/notification-background-investigation-services-0','PESTICIDES'); return false;" href="https://www.epa.gov/office-inspector-general/notification-background-investigation-services-0"><span>Notification: <span class="hlt">Background</span> Investigation Services</span></a></p> <p><a target="_blank" href="http://www.epa.gov/pesticides/search.htm">EPA Pesticide Factsheets</a></p> <p></p> <p></p> <p>Project #OA-FY15-0029, February 26, 2015. The Office of Inspector General (OIG) for the U.S. Environmental Protection Agency (EPA) plans to begin field work for our audit of <span class="hlt">background</span> investigation services.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AIPC..567..193F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AIPC..567..193F"><span>Bayesian <span class="hlt">background</span> estimation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fischer, R.; Dose, V.; Hanson, K. M.; von der Linden, W.</p> <p>2001-05-01</p> <p>The ubiquitous problem of estimating the <span class="hlt">background</span> of a measured spectrum is solved with Bayesian probability theory. A mixture model is used to capture the defining characteristics of the problem, namely that the <span class="hlt">background</span> is smoother than the signal. The smoothness property is quantified in terms of a cubic spline basis where a variable degree of smoothness is attained by allowing the number of knots and the knot positions to be adaptively chosen on the basis of the data. The fully Bayesian approach taken provides a natural way to handle knot adaptivity, allows uncertainties in the <span class="hlt">background</span> to be estimated and data points to be classified in groups containing only <span class="hlt">background</span> and groups with additional signal contribution. Our technique is demonstrated on a PIXE spectrum from a geological sample and an Auger spectrum from an 10 monolayer iron film on tungsten.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930033080&hterms=production+brazil&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dproduction%2Bbrazil','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930033080&hterms=production+brazil&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dproduction%2Bbrazil"><span>Free tropospheric ozone production following entrainment of urban plumes into deep <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pickering, Kenneth E.; Thompson, Anne M.; Scala, John R.; Tao, Wei-Kuo; Dickerson, Russell R.; Simpson, Joanne</p> <p>1992-01-01</p> <p>It is shown that rapid vertical transport of air from urban plumes through deep <span class="hlt">convective</span> clouds can cause substantial enhancement of the rate of O3 production in the free troposphere. Simulation of <span class="hlt">convective</span> redistribution and subsequent photochemistry of an urban plume from Oklahoma City during the 1985 PRESTORM campaign shows enhancement of O3 production in the free tropospheric cloud outflow layer by a factor of almost 4. In contrast, simulation of <span class="hlt">convective</span> transport of an urban plume from Manaus, Brazil, into a prestine free troposphere during GTE/ABLE 2B (1987), followed by a photochemical simulation, showed enhancement of O3 production by a factor of 35. The reasons for the different enhancements are (1) intensity of cloud vertical motion; (2) initial boundary layer O3 precursor concentrations; and (3) initial amount of <span class="hlt">background</span> free tropospheric NO(x). <span class="hlt">Convective</span> transport of ozone precursors to the middle and upper troposphere allows the resulting O3 to spread over large geographic regions, rather than being confined to the lower troposphere where loss processes are much more rapid. Conversely, as air with lower NO descends and replaces more polluted air, there is greater O3 production efficiency per molecule of NO in the boundary layer following <span class="hlt">convective</span> transport. As a result, over 30 percent more ozone could be produced in the entire tropospheric column in the first 24 hours following <span class="hlt">convective</span> transport of urban plumes.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005AGUFMSA53A1148H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005AGUFMSA53A1148H"><span>Forecasting of <span class="hlt">Convectively</span> Generated Gravity Waves in the Middle and Upper Atmosphere</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hassiotis, A.; Kane, T.; Gerrard, A.</p> <p>2005-12-01</p> <p>Model studies have shown that gravity waves excited by the thermal forcing mechanism in <span class="hlt">convection</span> excite high-frequency waves (10-100 min) with long vertical wavelengths (greater than 20 km). Source spectra for various spatial and temporal scales of thermal forcing are now available above <span class="hlt">convective</span> sources. When these energetic source spectra are propagated through synoptic <span class="hlt">background</span> fields via ray-tracing methods they are able to reach middle and upper atmospheric altitudes before dissipating, and subsequently influencing the momentum budget of the region. Waves that manage to propagate deeper into the thermosphere can potentially seed instabilities such as equatorial spread-F (ESF). ESF causes scintillation in radio communications and GPS signals. The current realism of the <span class="hlt">convective</span> source parameterizations has motivated the use of ray-tracing methods to predict some of the already observed effects of <span class="hlt">convectively</span>-generated gravity waves in the middle and upper atmosphere. For this reason, a unique global gravity wave forecasting model called FOREGRATS (FOREcasting of Gravity waves via Ray-tracing algorithms with prescribed Tropospheric Sources) is being developed. The model will identify <span class="hlt">convective</span> gravity wave sources in the troposphere, prescribe a realistic source spectrum, and then propagate the spectrum of waves up into the middle and upper atmosphere. In conjunction with observations at the Arecibo Observatory, which is located in a tropical <span class="hlt">convection</span> zone, the predictability of these high-frequency/long vertical wavelength waves in the middle and upper atmosphere will be explored with FOREGRATS.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19930033080&hterms=transport+urban&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtransport%2Burban','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19930033080&hterms=transport+urban&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dtransport%2Burban"><span>Free tropospheric ozone production following entrainment of urban plumes into deep <span class="hlt">convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pickering, Kenneth E.; Thompson, Anne M.; Scala, John R.; Tao, Wei-Kuo; Dickerson, Russell R.; Simpson, Joanne</p> <p>1992-01-01</p> <p>It is shown that rapid vertical transport of air from urban plumes through deep <span class="hlt">convective</span> clouds can cause substantial enhancement of the rate of O3 production in the free troposphere. Simulation of <span class="hlt">convective</span> redistribution and subsequent photochemistry of an urban plume from Oklahoma City during the 1985 PRESTORM campaign shows enhancement of O3 production in the free tropospheric cloud outflow layer by a factor of almost 4. In contrast, simulation of <span class="hlt">convective</span> transport of an urban plume from Manaus, Brazil, into a prestine free troposphere during GTE/ABLE 2B (1987), followed by a photochemical simulation, showed enhancement of O3 production by a factor of 35. The reasons for the different enhancements are (1) intensity of cloud vertical motion; (2) initial boundary layer O3 precursor concentrations; and (3) initial amount of <span class="hlt">background</span> free tropospheric NO(x). <span class="hlt">Convective</span> transport of ozone precursors to the middle and upper troposphere allows the resulting O3 to spread over large geographic regions, rather than being confined to the lower troposphere where loss processes are much more rapid. Conversely, as air with lower NO descends and replaces more polluted air, there is greater O3 production efficiency per molecule of NO in the boundary layer following <span class="hlt">convective</span> transport. As a result, over 30 percent more ozone could be produced in the entire tropospheric column in the first 24 hours following <span class="hlt">convective</span> transport of urban plumes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996GeCoA..60.2087H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996GeCoA..60.2087H"><span>A <span class="hlt">convective</span> model of water flow in Mururoa basalts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Henry, P.; Guy, C.; Cattin, R.; Dudoignon, P.; Sornein, J. F.; Caristan, Y.</p> <p>1996-06-01</p> <p>Even long after the end of volcanic activity, the <span class="hlt">background</span> geothermal flux of Mururoa atoll (French Polynesia) maintains fluid <span class="hlt">convection</span>. We present evidences that interstitial water is continuously renewed in the carbonate platform, as well as in the volcanic basement. In the carbonate rocks, the presence of a karst system allows <span class="hlt">convective</span> fluxes high enough for the thermal equilibration of the formation with the ocean around. On the contrary, <span class="hlt">convection</span> in the volcanic basement is, in most places, too slow to cause a measurable disturbance of temperature profiles. Thermal <span class="hlt">convection</span> models indicate that the average permeability of the volcanic basement cannot be more than a few 10 mD (10 -14 m 2), implying a residence time of more than 10,000 years. The concentration of Sr in porewaters is used as an indicator of the rock/water ratio and of the residence time of the fluid. Considering the measured permeabilities and the estimated rates of reaction, residence times of more than 1 My, corresponding to average permeabilities of less than 10 -16 m 2, are unlikely in the studied upper kilometer of the volcano. However, the extrapolation of the rates of dissolution for basaltic glass measured in the laboratory to in situ conditions apparently leads to overestimate the rates of reaction. Chemically reactive surface area per volume of fluid is a critical parameter in this extrapolation and its value is dependent on the method used to measure it. Although it may not be the only explanation, the discrepancies can be caused by the presence of clays in conduits for fluid flow and as a replacement product of glass. Comparing our results with studies of Quaternary basalts in Iceland, the 10 Ma alteration history of the Mururoa basalt results in a decrease of the permeability of the aquifers by several orders of magnitude, but does not cause a large change of the chemically reactive surface area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EPJST.223....9B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EPJST.223....9B"><span>Localized structures in <span class="hlt">convective</span> experiments</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Burguete, J.; Mancini, H.</p> <p>2014-01-01</p> <p>In this work we review localized structures appearing in thermo-<span class="hlt">convective</span> experiments performed in extended (large "aspect ratio") fluid layers. After a brief general review (not exhaustive), we focus on some results obtained in pure fluids in a Bénard-Marangoni system with non-homogeneous heating where some structures of this kind appear. The experimental results are compared in reference to the most classical observed in binary mixtures experiments or simulations. In the Bénard-Marangoni experiment we present the stability diagram where localized structures appear and the typical situations where these local mechanisms have been studied experimentally. Some new experimental results are also included. The authors want to honor Prof. H. Brand in his 60th. birthday and to thank him for helpful discussions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/285412','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/285412"><span>Two-dimensional <span class="hlt">convective</span> turbulence</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gruzinov, A.V.; Kukharkin, N.; Sudan, R.N.</p> <p>1996-02-01</p> <p>We show that 2D {bold E{times}B} ionospheric turbulence of the electron density in the equatorial electrojet is isomorphic to the viscous <span class="hlt">convection</span> of an ordinary fluid in a porous medium due to temperature gradients. Numerical simulations reveal the strong anisotropy in the turbulence, which consists of rising hot bubbles and falling cool bubbles. These bubbles break up into fingers leading to the formation of stable shear flows. After reaching a quasisteady state, the omnidirectional energy spectrum approaches a {ital k}{sup {minus}2} behavior, rather than {ital k}{sup {minus}5/3} as expected from isotropic turbulence. Physical mechanisms that lead to anisotropy are analyzed. {copyright} {ital 1996 The American Physical Society.}</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20010082519','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20010082519"><span>New Approaches to Parameterizing <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Randall, David A.; Lappen, Cara-Lyn</p> <p>1999-01-01</p> <p>Many general circulation models (GCMs) currently use separate schemes for planetary boundary layer (PBL) processes, shallow and deep cumulus (Cu) <span class="hlt">convection</span>, and stratiform clouds. The conventional distinctions. among these processes are somewhat arbitrary. For example, in the stratocumulus-to-cumulus transition region, stratocumulus clouds break up into a combination of shallow cumulus and broken stratocumulus. Shallow cumulus clouds may be considered to reside completely within the PBL, or they may be regarded as starting in the PBL but terminating above it. Deeper cumulus clouds often originate within the PBL with also can originate aloft. To the extent that our models separately parameterize physical processes which interact strongly on small space and time scales, the currently fashionable practice of modularization may be doing more harm than good.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NucFu..54l2002S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NucFu..54l2002S"><span>Actively <span class="hlt">convected</span> liquid metal divertor</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shimada, Michiya; Hirooka, Yoshi</p> <p>2014-12-01</p> <p>The use of actively <span class="hlt">convected</span> 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 <span class="hlt">convected</span> liquid metal divertor is the fast recovery from unmitigated disruptions. Also, the liquid metal divertor concept eliminates the erosion problem.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12953029','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12953029"><span>Thermal balance in <span class="hlt">convective</span> therapies.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Santoro, Antonio; Mancini, Elena; Canova, Cristina; Mambelli, Emanuele</p> <p>2003-08-01</p> <p>Among the factors causing intradialytic haemodynamic instability, dialysate temperature has been shown to play a relevant role. An improved cardiovascular response during isolated ultrafiltration or with cooled dialysate has been described in the past. Cold dialysate may increase the external heat loss compensating for the increase in core temperature, thus avoiding vasodilatation, but it also increases myocardial contractility. However, a better haemodynamic response to dialysis treatment has long been known in <span class="hlt">convective</span> therapies as well, and the hypothesis of a leading role for thermal balance is under discussion. In conventional haemofiltration (HF), venous blood cooling is expected, on the basis of the infusate temperature and the filtration fraction. In on-line HF, the infusate temperature and its volume may have a different impact on thermal balance depending on the site of infusion (pre- or post-dialyser). In an in vitro study comparing haemodialysis (HD) (conventional HD, dialysate 37 degrees C; and cold HD, dialysate 35.5 degrees C) with HF (pre- and post-dilution, 37 degrees C), we observed a more negative thermal balance with cold HD (-130 kJ/h) and with post-dilution HF (-75 kJ/h). The beneficial pressor effects of HF have been confirmed even in on-line HF, which actually has very few differences in the thermal balance compared with conventional HD (dialysate 37 degrees C). In on-line HF, the amount of warm infusion, often exceeding the blood flow, makes the achievement of a negative thermal balance highly unlikely. Thus, there is not sufficient evidence that vascular stability in on-line HF is solely related to different thermal energy balances. Other factors playing a relevant role in the cardiocirculatory response to <span class="hlt">convective</span> dialysis should thus be considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GMD.....8.3119H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GMD.....8.3119H"><span>Increasing vertical mixing to reduce Southern Ocean deep <span class="hlt">convection</span> in NEMO3.4</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Heuzé, C.; Ridley, J. K.; Calvert, D.; Stevens, D. P.; Heywood, K. J.</p> <p>2015-10-01</p> <p>Most CMIP5 (Coupled Model Intercomparison Project Phase 5) models unrealistically form Antarctic Bottom Water by open ocean deep <span class="hlt">convection</span> in the Weddell and Ross seas. To identify the mechanisms triggering Southern Ocean deep <span class="hlt">convection</span> in models, we perform sensitivity experiments on the ocean model NEMO3.4 forced by prescribed atmospheric fluxes. We vary the vertical velocity scale of the Langmuir turbulence, the fraction of turbulent kinetic energy transferred below the mixed layer, and the <span class="hlt">background</span> diffusivity and run short simulations from 1980. All experiments exhibit deep <span class="hlt">convection</span> in the Riiser-Larsen Sea in 1987; the origin is a positive sea ice anomaly in 1985, causing a shallow anomaly in mixed layer depth, hence anomalously warm surface waters and subsequent polynya opening. Modifying the vertical mixing impacts both the climatological state and the associated surface anomalies. The experiments with enhanced mixing exhibit colder surface waters and reduced deep <span class="hlt">convection</span>. The experiments with decreased mixing give warmer surface waters, open larger polynyas causing more saline surface waters and have deep <span class="hlt">convection</span> across the Weddell Sea until the simulations end. Extended experiments reveal an increase in the Drake Passage transport of 4 Sv each year deep <span class="hlt">convection</span> occurs, leading to an unrealistically large transport at the end of the simulation. North Atlantic deep <span class="hlt">convection</span> is not significantly affected by the changes in mixing parameters. As new climate model overflow parameterisations are developed to form Antarctic Bottom Water more realistically, we argue that models would benefit from stopping Southern Ocean deep <span class="hlt">convection</span>, for example by increasing their vertical mixing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFM.A23C0255G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFM.A23C0255G"><span>The Influence of Aerosols and Environmental Moisture on the Characteristics of Supercellular and Multicellular Deep <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Grant, L. D.; van den Heever, S. C.</p> <p>2013-12-01</p> <p>Mechanisms leading to differences between low-precipitation (LP) and classic (CL) supercell storm structure are not well understood, due in part to the small number of observational and modeling studies of LPs that have been reported in the literature. Though LPs and CLs sometimes occur within close proximity, CLs are found under a wider range of environmental conditions. LPs usually form near the dryline or in the high plains of the U.S., and they are typically isolated or upwind relative to surrounding deep <span class="hlt">convection</span>. Since high aerosol concentrations and dry layers are more likely in these environments, the goal of this research is to investigate the sensitivity of deep <span class="hlt">convective</span> characteristics, including LP and classic supercells as well as neighboring <span class="hlt">convection</span>, both to changes in the <span class="hlt">background</span> aerosol concentrations and environmental moisture profile. The Regional Atmospheric Modeling System (RAMS), configured as a high-resolution cloud-resolving model, was used to achieve this goal. Simulated <span class="hlt">convection</span> was initiated with a warm thermal perturbation, and subsequent deep <span class="hlt">convection</span> was simulated under a range of aerosol concentrations and moisture profiles. In the control simulation, which utilized a clean aerosol <span class="hlt">background</span> and a moist profile, the initial <span class="hlt">convection</span> splits into a right-mover that becomes a strong and steady classic supercell, and a left-mover that evolves into a multicellular cluster. Sensitivity tests demonstrate that the right-mover becomes an LP supercell under both clean and polluted aerosol concentrations when elevated dry layers are present in the moisture profile. Precipitation characteristics of the left-moving cluster are sensitive both to the aerosol concentrations and the moisture profile. The relative control of aerosols and dry layers on the precipitation characteristics, microphysical processes, and thermodynamics including cold pool forcing, of different dynamically controlled <span class="hlt">convective</span> storm types within the same</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/20860436','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/20860436"><span>Erosion/redeposition analysis of the ITER first wall with <span class="hlt">convective</span> and non-<span class="hlt">convective</span> plasma transport</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Brooks, J. N.; Allain, J. P.; Rognlien, T. D.</p> <p>2006-12-15</p> <p>Sputtering erosion/redeposition is analyzed for IAEA [Report GA10FDR1-01-07-13 (2001)] plasma facing components, with scrape-off layer (SOL) plasma <span class="hlt">convective</span> radial transport and nonconvective (diffusion-only) transport. The analysis uses the UEDGE code [T .D. Rognlien et al., J. Nucl. Mater. 196, 347 (1992)] and DEGAS code [D. P. Stotler et al., Contrib. Plasma Phys. 40, 221 (2000) ] to compute plasma SOL profiles and ion and neutral fluxes to the wall, TRIM-SP code [J. P. Biersack, W. Eckstein, J. Appl. Phys. A34, 73 (1984)] to compute sputter yields, and the REDEP/WBC code package [J. N. Brooks, Fusion Eng. Des. 60, 515 (2002)] for three-dimensional kinetic modeling of sputtered particle transport. <span class="hlt">Convective</span> transport is modeled for the <span class="hlt">background</span> plasma by a radially varying outward-flow component of the fluid velocity, and for the impurity ions by three models designed to bracket existing models/data. Results are reported here for the first wall with the reference beryllium coating and an alternative tungsten coating. The analysis shows: (1) sputtering erosion for <span class="hlt">convective</span> flow is 20-40 times higher than for diffusion-only but acceptably low ({approx}0.3 nm/s) for beryllium, and very low ({approx}0.002 nm/s) for tungsten; (2) plasma contamination by wall sputtering, with <span class="hlt">convective</span> flow, is of order 1% for beryllium and negligible for tungsten; (3) wall-to-divertor beryllium transport may be significant ({approx}10%-60% of the sputtered Be current); (4) tritium co-deposition in redeposited beryllium may be high ({approx}1-6 gT/400 s pulse)</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030061414&hterms=buoyancy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dbuoyancy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030061414&hterms=buoyancy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dbuoyancy"><span>Magnetic Control of Solutal Buoyancy Driven <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ramachandran, N.; Leslie, F. W.</p> <p>2003-01-01</p> <p>Volumetric forces resulting from local density variations and gravitational acceleration cause buoyancy induced <span class="hlt">convective</span> motion in melts and solutions. Solutal buoyancy is a result of concentration differences in an otherwise isothermal fluid. If the fluid also exhibits variations in magnetic susceptibility with concentration then <span class="hlt">convection</span> control by external magnetic fields can be hypothesized. Magnetic control of thermal buoyancy induced <span class="hlt">convection</span> in ferrofluids (dispersions of ferromagnetic particles in a carrier fluid) and paramagnetic fluids have been demonstrated. Here we show the nature of magnetic control of solutal buoyancy driven <span class="hlt">convection</span> of a paramagnetic fluid, an aqueous solution of Manganese Chloride hydrate. We predict the critical magnetic field required for balancing gravitational solutal buoyancy driven <span class="hlt">convection</span> and validate it through a simple experiment. We demonstrate that gravity driven flow can be completely reversed by a magnetic field but the exact cancellation of the flow is not possible. This is because the phenomenon is unstable. The technique can be applied to crystal growth processes in order to reduce <span class="hlt">convection</span> and to heat exchanger devices for enhancing <span class="hlt">convection</span>. The method can also be applied to impose a desired g-level in reduced gravity applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20030061414&hterms=Buoyancy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DBuoyancy','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20030061414&hterms=Buoyancy&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DBuoyancy"><span>Magnetic Control of Solutal Buoyancy Driven <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ramachandran, N.; Leslie, F. W.</p> <p>2003-01-01</p> <p>Volumetric forces resulting from local density variations and gravitational acceleration cause buoyancy induced <span class="hlt">convective</span> motion in melts and solutions. Solutal buoyancy is a result of concentration differences in an otherwise isothermal fluid. If the fluid also exhibits variations in magnetic susceptibility with concentration then <span class="hlt">convection</span> control by external magnetic fields can be hypothesized. Magnetic control of thermal buoyancy induced <span class="hlt">convection</span> in ferrofluids (dispersions of ferromagnetic particles in a carrier fluid) and paramagnetic fluids have been demonstrated. Here we show the nature of magnetic control of solutal buoyancy driven <span class="hlt">convection</span> of a paramagnetic fluid, an aqueous solution of Manganese Chloride hydrate. We predict the critical magnetic field required for balancing gravitational solutal buoyancy driven <span class="hlt">convection</span> and validate it through a simple experiment. We demonstrate that gravity driven flow can be completely reversed by a magnetic field but the exact cancellation of the flow is not possible. This is because the phenomenon is unstable. The technique can be applied to crystal growth processes in order to reduce <span class="hlt">convection</span> and to heat exchanger devices for enhancing <span class="hlt">convection</span>. The method can also be applied to impose a desired g-level in reduced gravity applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003A%26A...411L.107J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003A%26A...411L.107J"><span>SPI instrumental <span class="hlt">background</span> characteristics</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jean, P.; Vedrenne, G.; Roques, J. P.; Schönfelder, V.; Teegarden, B. J.; von Kienlin, A.; Knödlseder, J.; Wunderer, C.; Skinner, G. K.; Weidenspointner, G.; Attié, D.; Boggs, S.; Caraveo, P.; Cordier, B.; Diehl, R.; Gros, M.; Leleux, P.; Lichti, G. G.; Kalemci, E.; Kiener, J.; Lonjou, V.; Mandrou, P.; Paul, Ph.; Schanne, S.; von Ballmoos, P.</p> <p>2003-11-01</p> <p>In its space environment the INTEGRAL observatory is subject to an intense irradiation by energetic cosmic-ray particles that leads, via nuclear interactions with the telescope and spacecraft materials, to an important <span class="hlt">background</span> of false events. In this paper we present the characteristics of the instrumental <span class="hlt">background</span> that is observed in the spectrometer SPI (SPectrometer of INTEGRAL). We explain the tuning that has been performed on the parameters of the anticoincidence system in order to optimise the telescope sensitivity over the full energy range. Temporal variations of the instrumental <span class="hlt">background</span> are discussed and methods are proposed that allow for their modelling in first order. Based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic and Poland, and with the participation of Russia and the USA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ACP....16..161H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ACP....16..161H"><span>The diurnal cycle of rainfall over New Guinea in <span class="hlt">convection</span>-permitting WRF simulations</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Hassim, M. E. E.; Lane, T. P.; Grabowski, W. W.</p> <p>2016-01-01</p> <p><p class="p">In this study, we examine the diurnal cycle of rainfall over New Guinea using a series of <span class="hlt">convection</span>-permitting numerical simulations with the Weather Research and Forecasting (WRF) model. We focus our simulations on a period of suppressed regional-scale conditions (February 2010) during which local diurnal forcings are maximised. Additionally, we focus our study on the occurrence and dynamics of offshore-propagating <span class="hlt">convective</span> systems that contribute to the observed early-morning rainfall maximum north-east of New Guinea.<p class="p">In general, modelled diurnal precipitation shows good agreement with satellite-observed rainfall, albeit with some timing and intensity differences. The simulations also reproduce the occurrence and variability of overnight <span class="hlt">convection</span> that propagate offshore as organised squall lines north-east of New Guinea. The occurrence of these offshore systems is largely controlled by <span class="hlt">background</span> conditions. Days with offshore-propagating <span class="hlt">convection</span> have more middle tropospheric moisture, larger <span class="hlt">convective</span> available potential energy, and greater low-level moisture convergence. <span class="hlt">Convection</span> has similar characteristics over the terrain on days with and without offshore propagation.<p class="p">The offshore-propagating <span class="hlt">convection</span> manifests via a multi-stage evolutionary process. First, scattered <span class="hlt">convection</span> over land, which is remnant of the daytime maximum, moves towards the coast and becomes reorganised near the region of coastal convergence associated with the land breeze. The <span class="hlt">convection</span> then moves offshore in the form of a squall line at ˜ 5 m<mspace linebreak="nobreak" width="0.125em"/>s<i/>-1. In addition, cool anomalies associated with gravity waves generated by precipitating land <span class="hlt">convection</span> propagate offshore at a dry hydrostatic gravity wave speed (of ˜ 15 m<mspace linebreak="nobreak" width="0.125em"/>s<i/>-1) and act to destabilise the coastal/offshore environment prior to the arrival of the squall line. Although the gravity</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A34C..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A34C..01S"><span>Towards <span class="hlt">convection</span>-resolving climate modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schar, C.; Ban, N.; Fuhrer, O.; Keller, M.; Lapillonne, X.; Leutwyler, D.; Lüthi, D.; Schlemmer, L.; Schmidli, J.; Schulthess, T. C.</p> <p>2015-12-01</p> <p>Moist <span class="hlt">convection</span> is a fundamental process in our climate system, but is usually parameterized in climate models. The underlying approximations introduce significant uncertainties and biases, and there is thus a general thrust towards the explicit representation of <span class="hlt">convection</span>. For climate applications, <span class="hlt">convection</span>-resolving simulations are still very expensive, but are increasingly becoming feasible. Here we present recent results pertaining to the development and exploitation of <span class="hlt">convection</span>-resolving regional climate models. We discuss the potential and challenges of the approach, highlight validation using decade-long simulations, explore <span class="hlt">convection</span>-resolving climate change scenarios, and provide an outlook on the use of next-generation supercomputing architectures. Detailed results will be presented using the COSMO model over two computational domains at a horizontal resolution of 2.2 km. The first covers an extended Alpine region from Northern Italy to Northern Germany. For this domain decade-long simulations have been conducted, driven by both reanalysis as well as CMIP5 model data. Results show that explicit <span class="hlt">convection</span> leads to significant improvements in the representation of summer precipitation, and to substantial differences in climate projections in terms of precipitation statistics. The second domain covers European (with 1536x1536x60 grid points) and the respective simulations exploit heterogeneous many-core hardware architectures. Results demonstrate realistic mesoscale processes embedded in synoptic-scale features, such as line <span class="hlt">convection</span> along cold frontal systems, or the triggering of moist <span class="hlt">convection</span> by propagating cold-air pools. Currently a 10-year simulation using this set up is near completion. To efficiently use GPU-based high-performance computers, the model code underwent significant development, including a rewrite of the dynamical core in C++. It is argued that today's largest supercomputers would in principle be able to support - already</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900032073&hterms=Big+bang+theory&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DBig%2Bbang%2Btheory','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900032073&hterms=Big+bang+theory&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DBig%2Bbang%2Btheory"><span>The Cosmic <span class="hlt">Background</span> Explorer</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gulkis, Samuel; Lubin, Philip M.; Meyer, Stephan S.; Silverberg, Robert F.</p> <p>1990-01-01</p> <p>The Cosmic <span class="hlt">Background</span> Explorer (CBE), NASA's cosmological satellite which will observe a radiative relic of the big bang, is discussed. The major questions connected to the big bang theory which may be clarified using the CBE are reviewed. The satellite instruments and experiments are described, including the Differential Microwave Radiometer, which measures the difference between microwave radiation emitted from two points on the sky, the Far-Infrared Absolute Spectrophotometer, which compares the spectrum of radiation from the sky at wavelengths from 100 microns to one cm with that from an internal blackbody, and the Diffuse Infrared <span class="hlt">Background</span> Experiment, which searches for the radiation from the earliest generation of stars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1999IJMPA..14.4275T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1999IJMPA..14.4275T"><span>Cosmic Tachyon <span class="hlt">Background</span> Radiation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tomaschitz, Roman</p> <p></p> <p>The equilibrium statistical mechanics of a <span class="hlt">background</span> radiation of superluminal particles is investigated, based on a vectorial wave equation for tachyons of the Proca type. The partition function, the spectral energy density, and the various thermodynamic variables of an ideal Bose gas of tachyons in an open Robertson-Walker cosmology are derived. The negative mass square in the wave equation changes the frequency scaling in the Rayleigh-Jeans law, and there are also significant changes in the low temperature regime as compared to the microwave <span class="hlt">background</span>, in particular in the caloric and thermal equations of state.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017PhDT........89S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017PhDT........89S"><span>Investigation of the Mesoscale Interaction between the Sea Breeze Circulation and the Sandhills <span class="hlt">Convection</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sims, Aaron P.</p> <p></p> <p>In the Carolinas of the United States, there are two key land-surface features over which <span class="hlt">convective</span> precipitation often forms during the summer months. These geomorphic features are the Sandhills and coastline. Along the coastline, sea-breeze circulations regularly form and are known to initiate <span class="hlt">convection</span>. The Sandhills is a transitional zone of sandy soil surrounded by mixture of soils that include clay and loam. It extends through the central part of the Carolinas and into Georgia and is also the origin of <span class="hlt">convective</span> storms. The two geographical features, the coastline and the Sandhills, are in regional proximity of each other and the resultant sea-breeze front and the Sandhills <span class="hlt">convection</span> interact during summer. During this research, the investigation of the mechanism of interaction between these two features has led to the discovery of the Sandhills front, a shallow outflow density current that develops from deep <span class="hlt">convection</span> over the Sandhills and propagates eastward toward the coast. The convergence of the Sandhills front and the sea-breeze front initiates and enhances <span class="hlt">convection</span> between the Sandhills and the coastline. Observations during the month of June for the period 2004 to 2015 are used to evaluate the interaction between these two phenomena. On average, these interactions occur on approximately 24% of all days in June and on 36% of all days in June when synoptic scale systems are absent. Thus, the interactions between the sea-breeze and the Sandhills circulations do contribute to the precipitation in this region. <span class="hlt">Background</span> wind speeds and directions influence the location and the strength of <span class="hlt">convection</span> associated with this interaction. Onshore, offshore, and southwesterly flow classifications each present different strengths and locations of the interactions. Light winds ( 3 m s-1 to 6 m s-1 ) also influence the interactions differently. Observations indicate that moderate southwesterly flow has the highest total average and total maximum</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080045748&hterms=Exchange+rate+effects&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DExchange%2Brate%2Beffects','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080045748&hterms=Exchange+rate+effects&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DExchange%2Brate%2Beffects"><span>Effects of Deep <span class="hlt">Convection</span> on Atmospheric Chemistry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pickering, Kenneth E.</p> <p>2007-01-01</p> <p>This presentation will trace the important research developments of the last 20+ years in defining the roles of deep <span class="hlt">convection</span> in tropospheric chemistry. The role of deep <span class="hlt">convection</span> in vertically redistributing trace gases was first verified through field experiments conducted in 1985. The consequences of deep <span class="hlt">convection</span> have been noted in many other field programs conducted in subsequent years. Modeling efforts predicted that deep <span class="hlt">convection</span> occurring over polluted continental regions would cause downstream enhancements in photochemical ozone production in the middle and upper troposphere due to the vertical redistribution of ozone precursors. Particularly large post-<span class="hlt">convective</span> enhancements of ozone production were estimated for <span class="hlt">convection</span> occurring over regions of pollution from biomass burning and urban areas. These estimates were verified by measurements taken downstream of biomass burning regions of South America. Models also indicate that <span class="hlt">convective</span> transport of pristine marine boundary layer air causes decreases in ozone production rates in the upper troposphere and that <span class="hlt">convective</span> downdrafts bring ozone into the boundary layer where it can be destroyed more rapidly. Additional consequences of deep <span class="hlt">convection</span> are perturbation of photolysis rates, effective wet scavenging of soluble species, nucleation of new particles in <span class="hlt">convective</span> outflow, and the potential fix stratosphere-troposphere exchange in thunderstorm anvils. The remainder of the talk will focus on production of NO by lightning, its subsequent transport within <span class="hlt">convective</span> clouds . and its effects on downwind ozone production. Recent applications of cloud/chemistry model simulations combined with anvil NO and lightning flash observations in estimating NO Introduction per flash will be described. These cloud-resolving case-study simulations of <span class="hlt">convective</span> transport and lightning NO production in different environments have yielded results which are directly applicable to the design of lightning</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_24 --> <div id="page_25" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="481"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1226263','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1226263"><span>Transient Mixed <span class="hlt">Convection</span> Validation for NGNP</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Smith, Barton; Schultz, Richard</p> <p>2015-10-19</p> <p>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 <span class="hlt">convection</span>); (2) Blake Lance PhD dissertation (focused mainly on mixed and transient <span class="hlt">convection</span>). 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 <span class="hlt">Convection</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20080045748&hterms=Chemistry+chemicals&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DChemistry%2Bchemicals','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20080045748&hterms=Chemistry+chemicals&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3DChemistry%2Bchemicals"><span>Effects of Deep <span class="hlt">Convection</span> on Atmospheric Chemistry</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pickering, Kenneth E.</p> <p>2007-01-01</p> <p>This presentation will trace the important research developments of the last 20+ years in defining the roles of deep <span class="hlt">convection</span> in tropospheric chemistry. The role of deep <span class="hlt">convection</span> in vertically redistributing trace gases was first verified through field experiments conducted in 1985. The consequences of deep <span class="hlt">convection</span> have been noted in many other field programs conducted in subsequent years. Modeling efforts predicted that deep <span class="hlt">convection</span> occurring over polluted continental regions would cause downstream enhancements in photochemical ozone production in the middle and upper troposphere due to the vertical redistribution of ozone precursors. Particularly large post-<span class="hlt">convective</span> enhancements of ozone production were estimated for <span class="hlt">convection</span> occurring over regions of pollution from biomass burning and urban areas. These estimates were verified by measurements taken downstream of biomass burning regions of South America. Models also indicate that <span class="hlt">convective</span> transport of pristine marine boundary layer air causes decreases in ozone production rates in the upper troposphere and that <span class="hlt">convective</span> downdrafts bring ozone into the boundary layer where it can be destroyed more rapidly. Additional consequences of deep <span class="hlt">convection</span> are perturbation of photolysis rates, effective wet scavenging of soluble species, nucleation of new particles in <span class="hlt">convective</span> outflow, and the potential fix stratosphere-troposphere exchange in thunderstorm anvils. The remainder of the talk will focus on production of NO by lightning, its subsequent transport within <span class="hlt">convective</span> clouds . and its effects on downwind ozone production. Recent applications of cloud/chemistry model simulations combined with anvil NO and lightning flash observations in estimating NO Introduction per flash will be described. These cloud-resolving case-study simulations of <span class="hlt">convective</span> transport and lightning NO production in different environments have yielded results which are directly applicable to the design of lightning</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19730019065','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19730019065"><span>Heat flow and <span class="hlt">convection</span> demonstration (Apollo 14)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bannister, T. C.</p> <p>1973-01-01</p> <p>Apollo 14 Astronaut Stuart A. Roosa conducted a group of experiments during the lunar flyback on February 7, 1971, to obtain information on heat flow and <span class="hlt">convection</span> in gases and liquids in an environment of less than 0.000001 g. Flow observations and thermal data have shown that: (1) as expected, there are <span class="hlt">convective</span> motions caused by surface tension gradients in a plane liquid layer with a free upper surface; (2) heat flow in enclosed liquids and gases occurs mainly by diffusive heat conduction; and (3) some <span class="hlt">convective</span> processes, whose characteristics are not fully known, add to the heat transfer. The raw data are presented, and the analysis approach is given.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19720005294','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19720005294"><span>Importance of combining <span class="hlt">convection</span> with film cooling</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Colladay, R. S.</p> <p>1971-01-01</p> <p>The interaction of film and <span class="hlt">convection</span> cooling and its effect on wall cooling efficiency is investigated analytically for two cooling schemes for advanced gas turbine applications. The two schemes are full coverage- and counterflow-film cooling. In full coverage film cooling, the cooling air issues from a large number of small discrete holes in the surface. Counterflow film cooling is a film-<span class="hlt">convection</span> scheme with film injection from a slot geometry. The results indicate that it is beneficial to utilize as much of the cooling air heat sink as possible for <span class="hlt">convection</span> cooling prior to ejecting it as a film.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19720033207&hterms=sink+holes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dsink%2Bholes','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19720033207&hterms=sink+holes&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dsink%2Bholes"><span>Importance of combining <span class="hlt">convection</span> with film cooling.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Colladay, R. S.</p> <p>1972-01-01</p> <p>The interaction of film and <span class="hlt">convection</span> cooling and its effect on wall cooling efficiency is investigated analytically for two cooling schemes for advanced gas turbine applications. The two schemes are full coverage- and counterflow-film cooling. In full coverage film cooling, the cooling air issues from a large number of small discrete holes in the surface. Counterflow film cooling is a film-<span class="hlt">convection</span> scheme with film injection from a slot geometry. The results indicate that it is beneficial to utilize as much of the cooling air heat sink as possible for <span class="hlt">convection</span> cooling prior to ejecting it as a film.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19760004794','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19760004794"><span>Skylab M518 multipurpose furnace <span class="hlt">convection</span> analysis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bourgeois, S. V.; Spradley, L. W.</p> <p>1975-01-01</p> <p>An analysis was performed of the <span class="hlt">convection</span> which existed on ground tests and during skylab processing of two experiments: vapor growth of IV-VI compounds growth of spherical crystals. A parallel analysis was also performed on Skylab experiment indium antimonide crystals because indium antimonide (InSb) was used and a free surface existed in the tellurium-doped Skylab III sample. In addition, brief analyses were also performed of the microsegregation in germanium experiment because the Skylab crystals indicated turbulent <span class="hlt">convection</span> effects. Simple dimensional analysis calculations and a more accurate, but complex, <span class="hlt">convection</span> computer model, were used in the analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1983phse.proc..192J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1983phse.proc..192J"><span><span class="hlt">Convective</span> heat transfer inside passive solar buildings</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jones, R. W.; Balcomb, J. D.; Yamaguchi, K.</p> <p>1983-11-01</p> <p>Natural <span class="hlt">convection</span> between spaces in a building which play a major role in energy transfer are discussed. Two situations are investigated: <span class="hlt">Convection</span> through a single doorway into a remote room, and a <span class="hlt">convective</span> loop in a two story house with a south sunspace where a north stairway serves as the return path. A doorway sizing equation is given for the single door case. Data from airflow monitoring in one two-story house and summary data for five others are presented. The nature of the airflow and design guidelines are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19870009515','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19870009515"><span><span class="hlt">Convective</span> cell development and propagation in a mesoscale <span class="hlt">convective</span> complex</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ahn, Yoo-Shin; Brundidge, Kenneth C.</p> <p>1987-01-01</p> <p>A case study was made of the mesoscale <span class="hlt">convective</span> complex (MCC) which occurred over southern Oklahoma and northern Texas on 27 May 1981. This storm moved in an eastsoutheasterly direction and during much of its lifetime was observable by radars at Oklahoma City, Ok. and Stephenville, Tx. It was found that the direction of cell (VIP level 3 or more reflectivity) propagation was somewhat erratic but approximately the same as the system (VIP level 1 reflectivity) movement and the ambient wind. New cells developed along and behind the gust front make it appear that once the MCC is initiated, a synergistic relationship exists between the gust front and the MCC. The relationship between rainfall patterns and amounts and the infrared (IR) temperature field in the satellite imagery were examined. The 210 K isotherm of GOES IR imagery was found to encompass the rain area of the storm. The heaviest rainfall was in the vicinity of the VIP level 3 cells and mostly contained within the 205 K isotherm of GOES IR imagery.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016IJSyS..47.3846G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016IJSyS..47.3846G"><span>Global state feedback <span class="hlt">stabilisation</span> of stochastic high-order nonlinear systems with high-order and low-order nonlinearities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Gao, Fangzheng; Wu, Yuqiang; Yu, Xin</p> <p>2016-12-01</p> <p>In this paper, the problem of global <span class="hlt">stabilisation</span> by state feedback is investigated for a class of stochastic high-order nonlinear systems with both high-order and low-order nonlinearities, to which the existing control methods are inapplicable. Based on the generalised stochastic Lyapunov theorem, and by skillfully using the method of adding a power integrator, a continuous state feedback controller is successfully constructed, which can guarantee the global asymptotic stability in probability of the resulting closed-loop system in the sense of weak solution, and also is able to lead to an interesting result of finite-time <span class="hlt">stabilisation</span> under appropriate conditions. Finally, two simulation examples are provided to demonstrate the effectiveness of the proposed approach.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22269550','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22269550"><span>Cerium reduction at the interface between ceria and yttria-<span class="hlt">stabilised</span> zirconia and implications for interfacial oxygen non-stoichiometry</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Song, Kepeng; Schmid, Herbert; Srot, Vesna; Aken, Peter A. van; Gilardi, Elisa; Gregori, Giuliano; Maier, Joachim; Du, Kui</p> <p>2014-03-01</p> <p>Epitaxial CeO{sub 2} films with different thickness were grown on Y{sub 2}O{sub 3} <span class="hlt">stabilised</span> Zirconia substrates. Reduction of cerium ions at the interface between CeO{sub 2} films and yttria <span class="hlt">stabilised</span> zirconia substrates is demonstrated using aberration-corrected scanning transmission electron microscopy combined with electron energy-loss spectroscopy. It is revealed that most of the Ce ions were reduced from Ce{sup 4+} to Ce{sup 3+} at the interface region with a decay of several nanometers. Several possibilities of charge compensations are discussed. Irrespective of the details, such local non-stoichiometries are crucial not only for understanding charge transport in such hetero-structures but also for understanding ceria catalytic properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8542901','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8542901"><span><span class="hlt">Stabilisation</span> of high-activity 99mTc-d,l-HMPAO preparations with cobalt chloride and their biological behaviour.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mang'era, K O; Vanbilloen, H P; Schiepers, C W; Verbruggen, A M</p> <p>1995-10-01</p> <p>It has been reported that the stability of a 1.11-GBq (30 mCi) technetium-99m d,l-hexamethyl-propylene amine oxime (HMPAO) preparation can be improved to up to 5 h by the addition of 200 micrograms CoCl2.6H2O within 2 min after reconstitution. However, it is not clear whether this method is also efficient for high-activity preparations (5.55 GBq) and whether this modified 99mTc-d,l-HMPAO has the same biological properties and can safely be used. We have now studied CoCl2-<span class="hlt">stabilised</span> 99mTc-d,l-HMPAO preparations containing different amounts of "in-house" HMPAO ligand and SnCl2 and reconstituted with activities from 1.11 GBq to 5.55 GBq 99mTc. The characteristics of the generator eluates were also divergent, ranging from fresh eluates from a generator eluted less than 2 h previously to 4-h-old eluates from a generator not eluted during the preceding 72 h. Preparations containing up to 5.55 GBq 99mTc and as low as 2 micrograms SnCl2.2H2O can be efficiently <span class="hlt">stabilised</span> for at least 6 h by the addition of CoCl2 shortly after reconstitution. Interestingly, it was found that the <span class="hlt">stabilisation</span> method is not efficient if the cobalt ions are added prior to reconstitution of the preparation. This implies that the cobalt chloride cannot be incorporated in the labelling kit. Also, preparations with amounts of the ligand lower or higher than 0.5 mg formed the 99mTc-d,l-HMPAO complex with low radiochemical yield or showed rapid degradation. Therefore, combination of a subdivision and storage of Ceretec kits in fractions (as reported in the literature) is contra-indicated with this CoCl2 <span class="hlt">stabilisation</span> method. CoCl2-<span class="hlt">stabilised</span> Ceretec kits reconstituted with 5550 MBq 99mTcO4- and used 4-5 h after preparation retain the diagnostic usefulness of the fresh 1110-MBq preparation with regard to leucocyte labelling and brain imaging. Although baboon brain uptake of the <span class="hlt">stabilised</span> preparation was 6%-9% lower, this small difference could not be distinguished in the tomographic images. The</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015IJC....88..403F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015IJC....88..403F"><span>An improved sufficient condition for <span class="hlt">stabilisation</span> of unstable first-order processes by observer-state feedback</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Francisco Marquez Rubio, Juan; del Muro Cuéllar, Basilio; Velasco Villa, Martín; de Jesús Álvarez Ramírez, José</p> <p>2015-02-01</p> <p>This work considers the <span class="hlt">stabilisation</span> and control of unstable first-order linear systems subject to a relatively large I/O time delay. First, it is proposed an observer strategy to predict a specific internal signal in the process. The adequate prediction convergence is obtained and formally stated. Then, it is proposed an estimated state feedback control. Necessary and sufficient stability conditions with respect to time delay size and unstable time constant are provided. The proposed control strategy allows to address time delays as large as four times the unstable time constant of the open-loop system, in contrast with most of the reported related literature. Numerical examples are used for illustrating the parametric <span class="hlt">stabilisation</span> region as a function of the time delay.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014APLM....2c2104S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014APLM....2c2104S"><span>Cerium reduction at the interface between ceria and yttria-<span class="hlt">stabilised</span> zirconia and implications for interfacial oxygen non-stoichiometry</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Song, Kepeng; Schmid, Herbert; Srot, Vesna; Gilardi, Elisa; Gregori, Giuliano; Du, Kui; Maier, Joachim; van Aken, Peter A.</p> <p>2014-03-01</p> <p>Epitaxial CeO2 films with different thickness were grown on Y2O3 <span class="hlt">stabilised</span> Zirconia substrates. Reduction of cerium ions at the interface between CeO2 films and yttria <span class="hlt">stabilised</span> zirconia substrates is demonstrated using aberration-corrected scanning transmission electron microscopy combined with electron energy-loss spectroscopy. It is revealed that most of the Ce ions were reduced from Ce4+ to Ce3+ at the interface region with a decay of several nanometers. Several possibilities of charge compensations are discussed. Irrespective of the details, such local non-stoichiometries are crucial not only for understanding charge transport in such hetero-structures but also for understanding ceria catalytic properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12361031','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12361031"><span>Selection of natural treatment processes for algae removal from <span class="hlt">stabilisation</span> ponds effluents in Brasilia, using multicriterion methods.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Neder, K D; Carneiro, G A; Queiroz, T R; de Souza, M A A</p> <p>2002-01-01</p> <p>A multicriterion methodology is used in the evaluation and selection of the most appropriate alternative(s) for removing algae from <span class="hlt">stabilisation</span> ponds effluents in a case study in Brasilia. For this purpose, five different natural treatment processes are tested at pilot scale: rock filter, sand filter, floating aquatic plants, constructed wetlands, and overland flow. These pilot units were constructed in Brasilia and set in parallel, each one receiving a portion of the effluent that comes from an existing wastewater treatment plant composed of preliminary treatment, UASB reactors, and high-rate <span class="hlt">stabilisation</span> ponds. Several evaluation criteria are used in order to relate the capabilities of the post-treatment processes to the multiple objectives in this case. Two multicriterion decision-aid methods--compromise programming and ELECTRE-III--are used to select the most satisfying processes. The top ranking alternatives are indicated for subsequent studies, considering the possible implementation of these technologies to existing plants.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26705354','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26705354"><span>DOSE REFERENCE LEVELS IN SPANISH INTRAORAL DENTAL RADIOLOGY: <span class="hlt">STABILISATION</span> OF THE INCORPORATION OF DIGITAL SYSTEMS IN DENTAL CLINICAL PRACTICES.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Alcaraz, M; Velasco, F; Olivares, A; Velasco, E; Canteras, M</p> <p>2016-12-01</p> <p>A total of 34 044 official quality assurance reports in dental radiodiagnostic surgery from 16 regions of Spain, compiled from 2002 to 2014, were studied in order to determine the progress of diagnostic reference levels (DRLs) for obtaining diagnostic images under normal conditions for clinical practice in Spanish dental clinics. A DRL of 2.8 mGy was set in 2014, which represents a 41.7 % decrease compared with that of 2002 (4.8 mGy). Over the same time period, the mean dose fell by 55.2 %. However, over the last 3 y, the <span class="hlt">stabilisation</span> of the mean dose administered to patients has been observed with only a 6.7 % reduction in DRLs, which corresponds to the <span class="hlt">stabilisation</span> of dental radiodiagnostic surgery on replacing the use of radiographic film with digital imaging systems. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AIPC.1672b0004T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AIPC.1672b0004T"><span>Berkeley Low <span class="hlt">Background</span> Facility</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Thomas, K. J.; Smith, A. R.; Poon, A. W. P.; Chan, Y. D.; Norman, E. B.; Lesko, K. T.</p> <p>2015-08-01</p> <p>The Berkeley Low <span class="hlt">Background</span> Facility (BLBF) at Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California provides low <span class="hlt">background</span> gamma spectroscopy services to a wide array of experiments and projects. The analysis of samples takes place within two unique facilities; locally within a carefully-constructed, low <span class="hlt">background</span> laboratory on the surface at LBNL and at the Sanford Underground Research Facility (SURF) in Lead, SD. These facilities provide a variety of gamma spectroscopy services to low <span class="hlt">background</span> experiments primarily in the form of passive material screening for primordial radioisotopes (U, Th, K) or common cosmogenic/anthropogenic products; active screening via neutron activation analysis for U,Th, and K as well as a variety of stable isotopes; and neutron flux/beam characterization measurements through the use of monitors. A general overview of the facilities, services, and sensitivities will be presented. Recent activities and upgrades will also be described including an overview of the recently installed counting system at SURF (recently relocated from Oroville, CA in 2014), the installation of a second underground counting station at SURF in 2015, and future plans. The BLBF is open to any users for counting services or collaboration on a wide variety of experiments and projects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=reason+AND+student+NOT+attend+AND+lecture&pg=4&id=EJ876133','ERIC'); return false;" href="https://eric.ed.gov/?q=reason+AND+student+NOT+attend+AND+lecture&pg=4&id=EJ876133"><span>Building <span class="hlt">Background</span> Knowledge</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Fisher, Douglas; Ross, Donna; Grant, Maria</p> <p>2010-01-01</p> <p>Too often, students enter our classrooms with insufficient knowledge of physical science. As a result, they have a difficult time understanding content in texts, lectures, and laboratory activities. This lack of <span class="hlt">background</span> knowledge can have an impact on their ability to ask questions and wonder--both key components of inquiry. In this article,…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22488699','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22488699"><span>Berkeley Low <span class="hlt">Background</span> Facility</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Thomas, K. J.; Norman, E. B.; Smith, A. R.; Poon, A. W. P.; Chan, Y. D.; Lesko, K. T.</p> <p>2015-08-17</p> <p>The Berkeley Low <span class="hlt">Background</span> Facility (BLBF) at Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California provides low <span class="hlt">background</span> gamma spectroscopy services to a wide array of experiments and projects. The analysis of samples takes place within two unique facilities; locally within a carefully-constructed, low <span class="hlt">background</span> laboratory on the surface at LBNL and at the Sanford Underground Research Facility (SURF) in Lead, SD. These facilities provide a variety of gamma spectroscopy services to low <span class="hlt">background</span> experiments primarily in the form of passive material screening for primordial radioisotopes (U, Th, K) or common cosmogenic/anthropogenic products; active screening via neutron activation analysis for U,Th, and K as well as a variety of stable isotopes; and neutron flux/beam characterization measurements through the use of monitors. A general overview of the facilities, services, and sensitivities will be presented. Recent activities and upgrades will also be described including an overview of the recently installed counting system at SURF (recently relocated from Oroville, CA in 2014), the installation of a second underground counting station at SURF in 2015, and future plans. The BLBF is open to any users for counting services or collaboration on a wide variety of experiments and projects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvD..92l3006C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvD..92l3006C"><span>Nonthermal cosmic neutrino <span class="hlt">background</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chen, Mu-Chun; Ratz, Michael; Trautner, Andreas</p> <p>2015-12-01</p> <p>We point out that, for Dirac neutrinos, in addition to the standard thermal cosmic neutrino <span class="hlt">background</span> (C ν B ), there could also exist a nonthermal neutrino <span class="hlt">background</span> with comparable number density. As the right-handed components are essentially decoupled from the thermal bath of standard model particles, relic neutrinos with a nonthermal distribution may exist until today. The relic density of the nonthermal (nt) <span class="hlt">background</span> can be constrained by the usual observational bounds on the effective number of massless degrees of freedom Neff and can be as large as nν nt≲0.5 nγ. In particular, Neff can be larger than 3.046 in the absence of any exotic states. Nonthermal relic neutrinos constitute an irreducible contribution to the detection of the C ν B and, hence, may be discovered by future experiments such as PTOLEMY. We also present a scenario of chaotic inflation in which a nonthermal <span class="hlt">background</span> can naturally be generated by inflationary preheating. The nonthermal relic neutrinos, thus, may constitute a novel window into the very early Universe.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://eric.ed.gov/?q=mockingbirds&pg=2&id=EJ568485','ERIC'); return false;" href="https://eric.ed.gov/?q=mockingbirds&pg=2&id=EJ568485"><span>Foregrounding the <span class="hlt">Background</span>.</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Robbins, Bruce</p> <p>1998-01-01</p> <p>Argues that when introductory activities to the classics begin with <span class="hlt">background</span> information, it can upstage or confine the life of the story, and shows little faith in the students as readers or in the literature itself. Suggests sometimes letting the literature begin, and then helping students make sense of it. Discusses examples from "To Kill a…</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li class="active"><span>25</span></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_25 --> <center> <div class="footer-extlink text-muted"><small>Some links on this page may take you to non-federal websites. 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