Academic literature on the topic 'MLT circulation'
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Journal articles on the topic "MLT circulation"
1
Griffith, Matthew J., David R. Jackson, Daniel J. Griffin, and Chris J. Budd. "Stable extension of the unified model into the mesosphere and lower thermosphere." Journal of Space Weather and Space Climate 10 (2020): 19. http://dx.doi.org/10.1051/swsc/2020018.
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A coupled Sun-to-Earth model is the goal for accurate forecasting of space weather. A key component of such a model is a whole atmosphere model – a general circulation model extending from the ground into the upper atmosphere – since it is now known that the lower atmosphere also drives variability and space weather in the upper atmosphere, in addition to solar variability. This objective motivates the stable extension of The Met Office’s Unified Model (UM) into the Mesosphere and Lower Thermosphere (MLT), acting as a first step towards a whole atmosphere model. At the time of performing this research, radiation and chemistry schemes that are appropriate for use in the MLT had not yet been implemented. Furthermore, attempts to run the model with existing parameterizations and a raised upper boundary led to an unstable model with inaccurate solutions. Here, this instability is examined and narrowed down to the model’s radiation scheme – its assumption of Local Thermodynamic Equilibrium (LTE) is broken in the MLT. We subsequently address this issue by relaxation to a climatological temperature profile in this region. This provides a stable extended UM which can be used as a developmental tool for further examination of the model performance. The standard vertical resolution used in the UM above 70 km is too coarse (approx. 5 km) to represent waves that are important for MLT circulation. We build on the success of the nudging implementation by testing the model at an improved vertical resolution. Initial attempts to address this problem with a 3 km vertical resolution and a 100 km lid were successful, but on increasing the resolution to 1.5 km the model becomes unstable due to large horizontal and vertical wind velocities. Increasing the vertical damping coefficient, which damps vertical velocities near the upper boundary, allows a successful year long climatology to be produced with these model settings. With the goal of a whole atmosphere model we also experiment with an increased upper boundary height. Increasing the upper model boundary to 120 and 135 km also leads to stable simulations. However, a 3 km resolution must be used and it is necessary to further increase the vertical damping coefficient. This is highly promising initial work to raise the UM into the MLT, and paves the way for the development of a whole atmosphere model.
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Mbatha, N., V. Sivakumar, S. B. Malinga, H. Bencherif, and S. R. Pillay. "Study on the impact of sudden stratosphere warming in the upper mesosphere-lower thermosphere regions using satellite and HF radar measurements." Atmospheric Chemistry and Physics Discussions 9, no. 6 (November 2, 2009): 23051–72. http://dx.doi.org/10.5194/acpd-9-23051-2009.
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Abstract. The occurrence of sudden stratospheric warming (SSW) excites disturbances in the mesosphere-lower thermospheric (MLT) wind and temperature. Here, we have examined the high frequency (HF) radar wind data from the South African National Antarctic Expedition, SANAE (72° S, 3° W), a radar which is part of the Super Dual Auroral Radar Network (SuperDARN). Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) on board the Thermosphere-Ionosphere-Mesosphere-Energetics and Dynamics (TIMED) satellite temperature data and National Centre for Environmental Prediction (NCEP) temperature and wind data were use to investigate the dynamical effects of the unprecedented September 2002 SSW in the Antarctica stratosphere and MLT. The mean zonal wind (from SANAE HF radar) at the MLT shows reversal in approximately 7 days before the reversal at 10 hPa (from NCEP). This indicates that there was a downwards propagation of circulation disturbance. Westerly zonal winds dominate the winter MLT, but during the 2002 winter there were many periods of westward winds observed compared to other years. The dynamic spectrums of both meridional and zonal winds show presence of planetary waves (of ~14-day period) before the occurrence of the SSW. The SABER vertical temperature profiles indicated the cooling of the MLT region before the SSW event.
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Mbatha, N., V. Sivakumar, S. B. Malinga, H. Bencherif, and S. R. Pillay. "Study on the impact of sudden stratosphere warming in the upper mesosphere-lower thermosphere regions using satellite and HF radar measurements." Atmospheric Chemistry and Physics 10, no. 7 (April 12, 2010): 3397–404. http://dx.doi.org/10.5194/acp-10-3397-2010.
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Abstract. The occurrence of a sudden stratospheric warming (SSW) excites disturbances in the mesosphere-lower thermospheric (MLT) wind and temperature. Here, we have examined the high frequency (HF) radar wind data from the South African National Antarctic Expedition, SANAE (72° S, 3° W), a radar which is part of the Super Dual Auroral Radar Network (SuperDARN). Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) on board the Thermosphere-Ionosphere-Mesosphere-Energetics and Dynamics (TIMED) satellite temperature data and National Centre for Environmental Prediction (NCEP) temperature and wind data are used to investigate the dynamical effects of the unprecedented September 2002 SSW in the Antarctica stratosphere and MLT. The mean zonal wind (from SANAE HF radar) at the MLT shows reversal approximately 7 days before the reversal at 10 hPa (from NCEP). This indicates that there was a downwards propagation of circulation disturbance. Westerly zonal winds dominate the winter MLT, but during the 2002 winter there are many periods of westward winds observed compared to other years. The normalised power spectrums of both meridional and zonal winds show presence of planetary waves (of ~14-day period) before the occurrence of the SSW. The SABER vertical temperature profiles indicated the cooling of the MLT region before the SSW event.
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Griffith, Matthew J., Shaun M. Dempsey, David R. Jackson, Tracy Moffat-Griffin, and Nicholas J. Mitchell. "Winds and tides of the Extended Unified Model in the mesosphere and lower thermosphere validated with meteor radar observations." Annales Geophysicae 39, no. 3 (June 10, 2021): 487–514. http://dx.doi.org/10.5194/angeo-39-487-2021.
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Abstract. The mesosphere and lower thermosphere (MLT) is a critical region that must be accurately reproduced in general circulation models (GCMs) that aim to include the coupling between the lower and middle atmosphere and the thermosphere. An accurate representation of the MLT is thus important for improved climate modelling and the development of a whole atmosphere model. This is because the atmospheric waves at these heights are particularly large, and so the energy and momentum they carry is an important driver of climatological phenomena through the whole atmosphere, affecting terrestrial and space weather. The Extended Unified Model (ExUM) is the recently developed version of the Met Office's Unified Model which has been extended to model the MLT. The capability of the ExUM to model atmospheric winds and tides in the MLT is currently unknown. Here, we present the first study of winds and tides from the ExUM. We make a comparison against meteor radar observations of winds and tides from 2006 between 80 and 100 km over two radar stations – Rothera (68∘ S, 68∘ W) and Ascension Island (8∘ S, 14∘ W). These locations are chosen to study tides in two very different tidal regimes – the equatorial regime, where the diurnal (24 h) tide dominates, and the polar regime, where the semi-diurnal (12 h) tide dominates. The results of this study illustrate that the ExUM is capable of reproducing atmospheric winds and tides that capture many of the key characteristics seen in meteor radar observations, such as zonal and meridional wind maxima and minima, the increase in tidal amplitude with increasing height, and the decrease in tidal phase with increasing height. In particular, in the equatorial regime some essential characteristics of the background winds, tidal amplitudes and tidal phases are well captured but with significant differences in detail. In the polar regime, the difference is more pronounced. The ExUM zonal background winds in austral winter are primarily westward rather than eastward, and in austral summer they are larger than observed above 90 km. The ExUM tidal amplitudes here are in general consistent with observed values, but they are also larger than observed values above 90 km in austral summer. The tidal phases are generally well replicated in this regime. We propose that the bias in background winds in the polar regime is a consequence of the lack of in situ gravity wave generation to generate eastward fluxes in the MLT. The results of this study indicate that the ExUM has a good natural capability for modelling atmospheric winds and tides in the MLT but that there is room for improvement in the model physics in this region. This highlights the need for modifications to the physical parameterization schemes used in the model in this region – such as the non-orographic spectral gravity wave scheme – to improve aspects such as polar circulation. To this end, we make specific recommendations of changes that can be implemented to improve the accuracy of the ExUM in the MLT.
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Wei, Guanchun, Jianyong Lu, Wenbin Wang, Yufeng Tian, Jingyuan Li, Shiping Xiong, Meng Sun, et al. "Temperature Variations in the Mesosphere and Lower Thermosphere during Geomagnetic Storms with Disparate Durations at High Latitudes." Universe 9, no. 2 (February 5, 2023): 86. http://dx.doi.org/10.3390/universe9020086.
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Using the temperature data observed from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER), we investigate the response of the mesosphere and lower thermosphere (MLT) to two medium geomagnetic storms with disparate durations, on 20 April 2018 and 10 April 2022. The high-latitude MLT temperature increase in the Southern hemisphere can reach 40 K during April 2018 geomagnetic storm with a longer duration (Kp values greater than 4 for 15 h), while the temperature variations are less than 10 K for the April 2022 event (Kp values greater than 4 for 6 h). To investigate the different temperature responses to disparate geomagnetic storm durations and understand what physical process results in this difference, we simulated the two events using the thermosphere ionosphere mesosphere electrodynamics general circulation model (TIMEGCM). The simulations show that more particles and energy input in longer-duration geomagnetic storms produce larger ion drag force and pressure gradient force at ~130 km, and then the enhanced two forces cause faster horizontal wind, leading to larger horizontal divergence. Subsequently, the stronger downward vertical wind is transported to the MLT region (below 110 km) and ultimately makes greater temperature increases through adiabatic heating/cooling and vertical advection. Therefore, the effects of the storm’s duration on the MLT temperature are also important.
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Long, Chi, Tao Yu, Yang-Yi Sun, Xiangxiang Yan, Jian Zhang, Na Yang, Jin Wang, Chunliang Xia, Yu Liang, and Hailun Ye. "Atmospheric Gravity Wave Derived from the Neutral Wind with 5-Minute Resolution Routinely Retrieved by the Meteor Radar at Mohe." Remote Sensing 15, no. 2 (January 4, 2023): 296. http://dx.doi.org/10.3390/rs15020296.
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Atmospheric gravity waves (GWs) in the mesosphere-lower thermosphere (MLT) are crucial for the understanding of general circulation. However, their dynamical characteristics are hardly retrieved due to the difficulty in the high-resolution observation of wind. Therefore, this paper uses eight years (2013–2020) of meteor radar measurements in the MLT region at Mohe station (53.5, 122.3), China, to retrieve high-temporal-resolution mesospheric wind data and further evaluate the temporal variation of GW kinetic energy. As the detected meteor trails exceed 6, the wind velocity is recalculated using the least square algorithm method, significantly increasing the temporal resolution of wind from 1 h up to 5 min. This resolution is sufficiently high for the investigation of GW kinetic energy, which exhibits a high spatial-temporal variability. For instance, it is enhanced in the winter season during the period of 0200–1400 UT and in the spring season during the period of 0800–1300 UT. The similarity between the climatological characteristics of GWs in MLT and the seasonal variation of GW total energy in the troposphere, determined from high-resolution radiosondes near to Mohe station, suggests that the meteorology in the lower atmosphere could be an important source of GWs in the MLT region.
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Jacobi, Christoph, Tatiana Ermakova, Daniel Mewes, and Alexander I. Pogoreltsev. "El Niño influence on the mesosphere/lower thermosphere circulation at midlatitudes as seen by a VHF meteor radar at Collm (51.3 ° N, 13 ° E)." Advances in Radio Science 15 (September 21, 2017): 199–206. http://dx.doi.org/10.5194/ars-15-199-2017.
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Abstract. Mesosphere/lower thermosphere (MLT) zonal winds continuously measured by a VHF meteor radar at Collm, Germany (51.3° N, 13.0° E) in the height range 82 – 97 km from 2004 to date are analyzed with respect to the signature of El Niño. The comparison of Niño3 equatorial SST index and MLT wind time series shows that in January and especially in February zonal winds are positively correlated with the Niño3 index. We note a delay of about one month of the MLT zonal wind effect with respect to equatorial sea surface temperature variability. The signal is strong for the upper altitudes (above 90 km) accessible to the radar observations, but weakens with decreasing height. This reflects the fact that during El Niño years the westerly winter middle atmosphere wind jet is weaker, and this is also the case with the easterly lower thermospheric jet. Owing to the reversal of the absolute El Niño signal from negative to positive with altitude, at the height of the maximum meteor flux, which is around 90 km, the El Niño signal is weak. The experimental results can be qualitatively reproduced by numerical experiments using a mechanistic global circulation model with prescribed tropospheric temperatures and latent heat release for El Niño and La Niña conditions.
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Tang, Qiong, Haiyang Sun, Zhitao Du, Jiaqi Zhao, Yi Liu, Zhengyu Zhao, and Xueshang Feng. "Unusual Enhancement of Midlatitude Sporadic-E Layers in Response to a Minor Geomagnetic Storm." Atmosphere 13, no. 5 (May 16, 2022): 816. http://dx.doi.org/10.3390/atmos13050816.
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This study investigates the variations of middle and low latitude sporadic-E (Es) layers in response to a geomagnetic storm. Es layers are observed by five ionosondes located in the Eastern Asian sector. The critical frequencies of Es layers (foEs) at six stations increased in sequence from high latitude stations to low latitude stations after IMF/Bz turning southward. Lomb–Scargle analysis shows the amplification of semidiurnal oscillation amplitude in the vertical height of Es layers during geomagnetic disturbance. Modeling results of the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) show the enhancement of the wind field in the mesosphere and the lower thermosphere (MLT) region. Our study provides evidence that the enhanced wind field in the MLT region during the storm period could result in the enhancement of Es layers at middle and low latitude.
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Yoshikawa, M., and S. Miyahara. "Zonal mean meridional circulation in the low to middle latitude of MLT region: A numerical simulation by a general circulation model." Advances in Space Research 32, no. 5 (September 2003): 709–17. http://dx.doi.org/10.1016/s0273-1177(03)00405-8.
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Dawe, Jordan T., and Lu Anne Thompson. "PDO-Related Heat and Temperature Budget Changes in a Model of the North Pacific." Journal of Climate 20, no. 10 (May 15, 2007): 2092–108. http://dx.doi.org/10.1175/jcli4229.1.
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Abstract Heat and temperature budget changes in a ⅓° model of the North Pacific driven by an idealized Pacific decadal oscillation (PDO) atmospheric forcing are diagnosed to determine the roles of atmospheric heat flux and ocean dynamics in upper-ocean heat content and mixed layer temperature (MLT) changes. Changes in MLT and heat content during the transition between negative and positive PDOs are driven primarily by atmospheric heat fluxes, with contributions from ageostrophic advection and entrainment. Once the new PDO state is established, atmospheric heat flux in the central North Pacific works to mitigate the MLT change while vertical entrainment and ageostrophic advection act to enhance it. Upper-ocean heat content is affected in a similar matter, except that vertical processes are not important in the heat budget balance. At the same time, changes in wind stress curl cause the subtropical gyre to spin up and the subpolar gyre boundary to migrate southward. These circulation changes cause a large increase in the geostrophic advective heat flux in the Kuroshio region. This increase results in more heat flux to the atmosphere, demonstrating an active role for ocean dynamics in the upper-ocean heat budget. Eddy heat flux divergence along the Kuroshio Extension doubles after the transition, due to stronger eddy activity related to increased Kuroshio transport.
Dissertations / Theses on the topic "MLT circulation"
1
Muller, Lucas Omar. "Mathematical modelling and simulation of the human circulation with emphasis on the venous system: application to the CCSVI condition." Doctoral thesis, Università degli studi di Trento, 2014. https://hdl.handle.net/11572/367928.
Full textAbstract:
Recent advances in medical science regarding the role of the venous system in the development of neurological conditions has renewed the attention of researchers in this district of the cardiovascular system. The main goal of this thesis is to perform a theoretical study of Chronic CerebroSpinal Venous Insufficiency (CCSVI), a venous pathology that has been associated to Multiple Sclerosis. CCSVI is a condition in which main cerebral venous drainage
pathways are obstructed. Its impact in cerebral hemodynamics and its connection to Multiple Sclerosis is subject of current debate in the medical community. In order to perform a credible study of the haemodynamical aspects of CCSVI, a sufficiently accurate mathematical model
of the problem under investigation must be used. The venous system has not received the same attention as the arterial counterpart by the medical community. As a consequence, the
mathematical modeling and numerical simulation of the venous system lies far behind that of the arterial system. The venous system is a low-pressure system, formed by very thin-walled vessels, if compared to arteries, that are likely to collapse under the action of gravitational
or external forces. These properties set special requirements on the mathematical models and
numerical schemes to be used. In this thesis we present a closed-loop multi-scale mathematical model of the cardiovascular system, where medium to large arteries and veins are represented as one-dimensional (1D) vessels, whereas the heart, the pulmonary circulation, capillary beds
and intracranial pressure are modeled as lumped parameter models. A characteristic feature of our closed-loop model is the detailed description of head and neck veins. Due to the large inter-subject variability of the venous system, we perform a patient-specific characterization of
major veins of the head and neck using MRI data collected in collaboration with the Magnetic Resonance Research Facility of the Wayne State University, Detroit (USA). Computational results are carefully validated using published data for the arterial system and most regions of the venous system. For head and neck veins validation is carried out through a detailed comparison of simulation results against patient-specific Phase-Contrast MRI flow quantification data. Regarding the development of novel numerical schemes, we construct high-order accurate, robust
and efficient numerical schemes for 1D blood flow in elastic and viscoelastic vessels, as well as a solver for vessel networks. The solver is validated in the context of an in vitro network of vessels for which experimental and numerical results are available. After validation of both, the mathematical model and the numerical methodology, we use our theoretical tool to study the influence of different CCSVI patterns on cerebral hemodynamics. CCSVI patterns are defined by the medical literature as combinations of venous obstructions at different locations. Here we used two strategies. First, we take a venous configuration corresponding to a healthy control
and explore the effect of different CCSVI patterns by modifying this network. Then, we characterize our venous network with the geometry of a real CCSVI patient and compare results with the ones obtained for the healthy control. The presented model provides a powerful tool to study still unresolved aspects of cerebral blood flow physiology, as well as several venous pathologies. Furthermore, it constitutes an ideal platform for improving currently used algorithms and for integrating fundamental physiological processes, such as detailed hemodynamics,
regulatory mechanisms and transport of substances.
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Carroll, Dustin. "Modeling Circulation Dynamics and Submarine Melt in Greenland Fjords." Thesis, University of Oregon, 2017. http://hdl.handle.net/1794/22626.
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Meltwater accumulated on the Greenland Ice Sheet drains to glacier beds, discharging into fjords hundreds of meters below sea level. The injection of meltwater at depth generates an upwelling plume that entrains warm ocean water as it rises along the terminus, increasing submarine melt and driving a fjord-scale exchange flow. However, due to sparse ocean-glacier observations, we lack a process understanding of how plumes control fjord circulation and submarine melt. Combining numerical modeling, theory, and observations, this dissertation investigates near-glacier plume dynamics, the influence of glacier depth on plume structure and submarine melt, and the role of fjord-glacier geometry on circulation in tidewater glacier fjords.
In Chapter II, I use buoyant plume theory and a nonhydrostatic, three-dimensional ocean–ice model to investigate the sensitivity of plume dynamics to subglacial discharge, turbulent diffusivity, and conduit geometry. Large discharges result in plumes with positive temperature and salinity anomalies in the upper water column. Fjord circulation is sensitive to conduit geometry; distributed subglacial discharge results in a stronger return flow of warm water toward the terminus. In Chapter III, I use buoyant plume theory, initialized with realistic ranges of subglacial discharge, glacier depth, and ocean stratification, to investigate how plume structure and submarine melt vary during summer months in 12 Greenland fjords. Grounding line depth is a primary control on plume-induced submarine melt: deep glaciers produce warm, salty subsurface plumes that undercut termini, and shallow glaciers produce cold, fresh surface-confined plumes that can overcut. Finally, in Chapter IV, I use regional-scale numerical ocean simulations to systematically evaluate how fjord circulation forced by subglacial plumes, tides, and wind stress depends on fjord width, glacier depth, and sill height. Glaciers grounded below sill depth can draw shelf waters over a shallow sill and into
fjord basins with seasonal subglacial discharge; this process is independent of external shelf forcing. These results underscore the first-order effect that subglacial discharge and fjord-glacier geometry have in controlling fjord circulation and, thus, ocean heat flux to the ice.
This dissertation includes previously published and co-authored material.
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Shah, Ajay M. (Ajay Mukesh). "Technologies for the isolation of circulating tumor cells." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/72916.
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Thesis (Ph. D. in Medical Engineering)--Harvard-MIT Program in Health Sciences and Technology, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 125-129).
Metastasis, the spread and growth of tumor cells from the primary site to distant organs, is arguably the most devastating and deadly attribute of cancer, and is ultimately responsible for 90% of cancer-related deaths. Circulating tumor cells (CTCs) are exceedingly rare cells found in the whole blood of cancer patients which have the potential to serve as a 'blood biopsy'. The intricate characterization of these cells could result in an entire new class of therapies directly targeting metastasis. Present technologies enable only a susbset of potential analyses to be conducted, principally due to sub-optimal cell isolation sensitivity, purity, throughput, or handling method. Here, we present two novel technologies to address the challenge of CTC isolation. First, we build on affinity-based microfluidic cell capture platforms by developing sacrificial hydrogel coatings to enable the innocuous release of captured cells; we demonstrate that model CTCs captured from whole blood remain viable and proliferative following release and are compatible with downstream immunostaining and FISH analysis. Second, we present a novel cell sorting system that interrogates over 10 million individual events each second, resulting in a high throughput, ultra-efficient rare cell sorter that delivers enriched cells in a vial, readily compatible with virtually any downstream assay. This is the first system combining the high sensitivity and single cell resolution that is characteristic of FACS with the practicality of MACS at a throughput and specificity afforded by inertial focusing, enabling operation in both 'positive selection' and 'negative depletion' modes. We find greater than 90% cell isolation efficiencies with over 2.5 log depletion of contaminating WBCs. Furthermore, the system is applied to clinical patient samples, and proof-of-concept is demonstrated in a cohort of breast, lung and prostate patients. Working in a negative depletion mode to isolate target cells in an unbiased fashion, we used the system to assess single putative CTCs isolated from an endogenous pancreatic mouse model for gene expression of tumor markers. Initial data confirms CTC heterogeneity at the single cell level, and positions us to move forward with single cell transcriptome sequencing, which may reveal a broad array of CTC phenotypes including metastatic precursors.
by Ajay Mukesh Shah.
Ph.D.in Medical Engineering
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Min, Changwook. "Miniaturized electromagnetic biosensors for circulating cancer biomarker detection." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/113786.
Full textAbstract:
Thesis: Ph. D. in Biomedical Engineering, Harvard-MIT Program in Health Sciences and Technology, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 113-120).
Cancer is one of leading cause of deaths, and responsible for 8.2 million deaths worldwide. Especially, 70% of deaths from cancer occur in low or mid income countries. In order to deliver affordable and accessible cancer care to low income developing countries, it is critical to develop rapid, low cost, and highly accurate tools for cancer detection and treatment. Recently, liquid biopsy and circulating cancer biomarkers such as circulating tumor cells (CTC), extracellular vesicles (EV), and cell free DNA (cfDNA) have gained great attentions for early diagnosis, prognosis, and treatment monitoring of cancer patients because they can be accessed in less invasive approaches through body fluids while providing quantitative information about original tumors at low cost. To facilitate detection of circulating cancer biomarkers, we developed electromagnetic biosensing systems for rapid and quantitative molecular analysis. First, we report portable nuclear magnetic resonance (NMR) system that detects cancer cells or proteins labelled with magnetic nanoparticles (MNPs). The developed NMR system could detect as low as 20 cancer cells in 5 uL samples. Second, we describe micro-Hall magnetometer that molecularly profiles single cancer cell with magnetic multiplexing. The micro-Hall magnetometer, which consisted of an array of 7 um x 7 um Hall sensors, showed its capability to differentiate magnetic particles with distinct magnetic moments. We applied this technology to molecular profiling of single ovarian cancer cell. Last, we introduce wirelessly powered electrochemical system that detect cancer specific EV and DNA. Using immuno-magnetic sandwich assay, we could enrich almost 100% of EVs from clinical specimens without ultracentrifugation and profile cancer specific transmembrane proteins from as low as 105 EVs. Also, we demonstrated PCR-free detection of single stranded DNA with in-vitro protein synthesis assay. These electromagnetic biosensors will be powerful tools to deliver more accessible and affordable cancer care to resource limited areas in developing countries.
by Changwook Min.
Ph. D. in Biomedical Engineering
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Muller, Lucas Omar. "Mathematical modelling and simulation of the human circulation with emphasis on the venous system: application to the CCSVI condition." Doctoral thesis, University of Trento, 2014. http://eprints-phd.biblio.unitn.it/1184/1/Mueller_PhD.pdf.
Full textAbstract:
Recent advances in medical science regarding the role of the venous system in the development of neurological conditions has renewed the attention of researchers in this district of the cardiovascular system. The main goal of this thesis is to perform a theoretical study of Chronic CerebroSpinal Venous Insufficiency (CCSVI), a venous pathology that has been associated to Multiple Sclerosis. CCSVI is a condition in which main cerebral venous drainage
pathways are obstructed. Its impact in cerebral hemodynamics and its connection to Multiple Sclerosis is subject of current debate in the medical community. In order to perform a credible study of the haemodynamical aspects of CCSVI, a sufficiently accurate mathematical model
of the problem under investigation must be used. The venous system has not received the same attention as the arterial counterpart by the medical community. As a consequence, the
mathematical modeling and numerical simulation of the venous system lies far behind that of the arterial system. The venous system is a low-pressure system, formed by very thin-walled vessels, if compared to arteries, that are likely to collapse under the action of gravitational
or external forces. These properties set special requirements on the mathematical models and
numerical schemes to be used. In this thesis we present a closed-loop multi-scale mathematical model of the cardiovascular system, where medium to large arteries and veins are represented as one-dimensional (1D) vessels, whereas the heart, the pulmonary circulation, capillary beds
and intracranial pressure are modeled as lumped parameter models. A characteristic feature of our closed-loop model is the detailed description of head and neck veins. Due to the large inter-subject variability of the venous system, we perform a patient-specific characterization of
major veins of the head and neck using MRI data collected in collaboration with the Magnetic Resonance Research Facility of the Wayne State University, Detroit (USA). Computational results are carefully validated using published data for the arterial system and most regions of the venous system. For head and neck veins validation is carried out through a detailed comparison of simulation results against patient-specific Phase-Contrast MRI flow quantification data. Regarding the development of novel numerical schemes, we construct high-order accurate, robust
and efficient numerical schemes for 1D blood flow in elastic and viscoelastic vessels, as well as a solver for vessel networks. The solver is validated in the context of an in vitro network of vessels for which experimental and numerical results are available. After validation of both, the mathematical model and the numerical methodology, we use our theoretical tool to study the influence of different CCSVI patterns on cerebral hemodynamics. CCSVI patterns are defined by the medical literature as combinations of venous obstructions at different locations. Here we used two strategies. First, we take a venous configuration corresponding to a healthy control
and explore the effect of different CCSVI patterns by modifying this network. Then, we characterize our venous network with the geometry of a real CCSVI patient and compare results with the ones obtained for the healthy control. The presented model provides a powerful tool to study still unresolved aspects of cerebral blood flow physiology, as well as several venous pathologies. Furthermore, it constitutes an ideal platform for improving currently used algorithms and for integrating fundamental physiological processes, such as detailed hemodynamics,
regulatory mechanisms and transport of substances.
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Görgen, Klaus. "Sensitivitätsstudien und Analyse von Atmosphäre-Meereis-Wechselwirkungen mit dem regionalen Atmosphärenmodell HIRHAM4 auf Basis eines neu entwickelten beobachtungsgestützten unteren Modellantriebs während ausgewählter Sommer über der Arktis, Laptewsee = Sensitivity studies and analysis of atmosphere-sea-ice-interactions with the regional atmospheric model HIRHAM4 using a newly developed observational lower boundary forcing dataset during selected summers over the Arctic/Laptev Sea /." Bremerhaven : Alfred-Wegener-Inst. für Polar- und Meeresforschung, 2006. http://www.gbv.de/dms/bs/toc/517265761.pdf.
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Huff, Russell. "Melt anomalies on the Greenland Ice Sheet and large scale modes of atmospheric circulation." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3256466.
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Persson, Marie, Christina Ekerfelt, Jan Ernerudh, Leif Matthiesen, Maria Jenmalm, Yvonne Jonsson, Martina Sandberg, and Göran Berg. "Increased circulating paternal antigen-specific IFN-γ- and IL-4-secreting cells during pregnancy in allergic and non-allergic women." Linköpings universitet, Klinisk immunologi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-16134.
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INTRODUCTION: Allergic women have been reported to give birth to more children than non-allergic women, speculatively explained by the former's predisposition for Th2 polarization, possibly favoring pregnancy. AIM: The aim of this study was to test the hypothesis that allergy is associated with more Th2-deviated responses to paternal antigens throughout pregnancy. METHODS: Blood samples were collected on six occasions during pregnancy and two occasions postpartum (pp). Of the 86 women initially included, 54 women had a normal pregnancy and completed the sampling procedures. Eleven women fulfilled the strict criteria for allergy (allergic symptoms and circulating IgE antibodies to inhalant allergens) and 23 were strictly non-allergic (non-sensitized without symptoms). The numbers of blood mononuclear cells secreting IFN-gamma and IL-4, spontaneously and in response to paternal alloantigens, were compared between the groups. RESULTS: The numbers of spontaneously as well as paternal antigen-induced IFN-gamma- and IL-4-secreting cells were similar in allergic and non-allergic pregnant women on all occasions. A similar increase in the numbers of both IFN-gamma- and IL-4-secreting cells were found in allergic and non-allergic women during pregnancy, both regarding spontaneous and paternal antigen-induced secretion. CONCLUSIONS: This study does not support the hypothesis of a more pronounced Th2-deviation to paternal antigens in allergic pregnant women compared with non-allergic pregnant women, as measured by number of cytokine-secreting cells. The observed increase of both IFN-gamma- and IL-4-secreting cells during normal pregnancy may be interpreted as a Th2-situation, since the effects of IL-4 predominate over the effects of IFN-gamma.
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Polanski, Stefan. "Simulation der indischen Monsunzirkulation mit dem Regionalen Klimamodell HIRHAM." Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5250/.
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In dieser Arbeit wird das regionale Klimamodell HIRHAM mit einer horizontalen Auflösung von 50 km und 19 vertikalen Schichten erstmals auf den asiatischen Kontinent angewendet, um die indische Monsunzirkulation unter rezenten und paläoklimatischen Bedingungen zu simulieren. Das Integrationsgebiet des Modells erstreckt sich von etwa 0ºN - 50ºN und 42ºE - 110ºE und bedeckt dabei sowohl die hohe Topographie des Himalajas und Tibet Plateaus als auch den nördlichen Indischen Ozean. Das Ziel besteht in der Beschreibung der regionalen Kopplung zwischen der Monsunzirkulation und den orographischen sowie diabatischen Antriebsmechanismen.
Eine 44-jährige Modellsimulation von 1958-2001, die am seitlichen und unteren Rand von ECMWF Reanalysen (ERA40) angetrieben wird, bildet die Grundlage für die Validierung der Modellergebnisse mit Beobachtungen auf der Basis von Stations- und Gitterdatensätzen. Der Fokus liegt dabei auf der atmosphärischen Zirkulation, der Temperatur und dem Niederschlag im Sommer- und Wintermonsun, wobei die Qualität des Modells sowohl in Bezug zur langfristigen und dekadischen Klimatologie als auch zur interannuellen Variabilität evaluiert wird. Im Zusammenhang mit einer realistischen Reproduktion der Modelltopographie kann für die Muster der Zirkulation und Temperatur eine gute Übereinstimmung zwischen Modell und Daten nachgewiesen werden. Der simulierte Niederschlag zeigt eine bessere Übereinstimmung mit einem hoch aufgelösten Gitterdatensatz über der Landoberfläche Zentralindiens und in den Hochgebirgsregionen, der den Vorteil des Regionalmodells gegenüber der antreibenden Reanalyse hervorhebt.
In verschiedenen Fall- und Sensitivitätsstudien werden die wesentlichen Antriebsfaktoren des indischen Monsuns (Meeresoberflächentemperaturen, Stärke des winterlichen Sibirischen Hochs und Anomalien der Bodenfeuchte) untersucht. Die Ergebnisse machen deutlich, dass die Simulation dieser Mechanismen auch mit einem Regionalmodell sehr schwierig ist, da die Komplexität des Monsunsystems hochgradig nichtlinear ist und die vor allem subgridskalig wirkenden Prozesse im Modell noch nicht ausreichend parametrisiert und verstanden sind.
Ein paläoklimatisches Experiment für eine 44-jährige Zeitscheibe im mittleren Holozän (etwa 6000 Jahre vor heute), die am Rand von einer globalen ECHAM5 Simulation angetrieben wird, zeigt markante Veränderungen in der Intensität des Monsuns durch die unterschiedliche solare Einstrahlung, die wiederum Einflüsse auf die SST, die Zirkulation und damit auf die Niederschlagsmuster hat.In this study the regional climate model HIRHAM with a horizontal resolution of 50 km and 19 vertical levels is applied over the Asian continent to simulate the Indian monsoon circulation under present-day and past conditions. The integration domain extends from 0ºN - 50ºN and 42ºE - 110ºE and covers the high topography of Himalayas and Tibetan Plateau as well as the northern Indian Ocean. The main objective is the description of the regional coupling between monsoon circulation and orographic as well as thermal driving mechanisms of monsoon. A 44-years long simulation from 1958-2001, driven at the lateral and lower boundaries by European reanalysis (ERA40), is the basis for the validation of model results with observations based on station and gridded data sets. The focus is on the the long-term and decadal summer and winter monsoon climatology and its variability concerning atmospheric circulation, temperature and precipitation. The results successfully reproduce the observations due to a realistic simulation of topographic features. The simulated precipitation shows a better agreement with a high-resolution gridded data set over the central land areas of India and in the higher elevated Tibetan and Himalayan regions than ERA40. In different case and sensitivity studies the main driving mechanisms of the Indian monsoon (Sea Surface Temperatures, strength of the Siberian High in winter and soil moisture anomalies) are investigated. The results show, that the simulation of these mechanisms with a regional climate model is also difficult related to the complex non linear monsoon system and the small-scale processes, which are not just sufficiently parameterized and understood in the model. A paleoclimatic experiment for a 44-years long time slice in mid-holocene (6000 years before present), which is driven by a global ECHAM5 simulation, shows significant changes in the monsoon intensity due to the different solar forcing, which influences the SST, the circulation and the precipitation.
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Dansereau, Véronique. "Ice shelf-ocean interactions in a general circulation model : melt-rate modulation due to mean flow and tidal currents." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78549.
Full textAbstract:
Thesis (S.M.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 121-123).
Interactions between the ocean circulation in sub-ice shelf cavities and the overlying ice shelf have received considerable attention in the context of observed changes in flow speeds of marine ice sheets around Antarctica. Modeling these interactions requires parameterizing the turbulent boundary layer processes to infer melt rates from the oceanic state at the ice-ocean interface. Here we explore two such parameterizations in the context of the MIT ocean general circulation model coupled to the z-coordinates ice shelf cavity model of Losch (2008). We investigate both idealized ice shelf cavity geometries as well as a realistic cavity under Pine Island Ice Shelf (PIIS), West Antarctica. Our starting point is a three-equation melt rate parameterization implemented by Losch (2008), which is based on the work of Hellmer and Olbers (1989). In this form, the transfer coefficients for calculating heat and freshwater fluxes are independent of frictional turbulence induced by the proximity of the moving ocean to the fixed ice interface. More recently, Holland and Jenkins (1999) have proposed a parameterization in which the transfer coefficients do depend on the ocean-induced turbulence and are directly coupled to the speed of currents in the ocean mixed layer underneath the ice shelf through a quadratic drag formulation and a bulk drag coefficient. The melt rate parameterization in the MITgcm is augmented to account for this velocity dependence. First, the effect of the augmented formulation is investigated in terms of its impact on melt rates as well as on its feedback on the wider sub-ice shelf circulation. We find that, over a wide range of drag coefficients, velocity-dependent melt rates are more strongly constrained by the distribution of mixed layer currents than by the temperature gradient between the shelf base and underlying ocean, as opposed to velocity-independent melt rates. This leads to large differences in melt rate patterns under PIIS when including versus not including the velocity dependence. In a second time, the modulating effects of tidal currents on melting at the base of PIIS are examined. We find that the temporal variability of velocity-dependent melt rates under tidal forcing is greater than that of velocity-independent melt rates. Our experiments suggest that because tidal currents under PIIS are weak and buoyancy fluxes are strong, tidal mixing is negligible and tidal rectification is restricted to very steep bathymetric features, such as the ice shelf front. Nonetheless, strong tidally-rectified currents at the ice shelf front significantly increase ablation rates there when the formulation of the transfer coefficients includes the velocity dependence. The enhanced melting then feedbacks positively on the rectified currents, which are susceptible to insulate the cavity interior from changes in open ocean conditions.
by Véronique Dansereau.
S.M.
Books on the topic "MLT circulation"
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Yun, Sŏng-bŏm. Haeyang isang hyŏnsang kamsi pangan mit yech'ŭk yŏn'gu. Inch'ŏn-si: Kukt'o Haeyangbu Kungnip Haeyang Chosawŏn, 2011.
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Ding, Yulong. Fundamental studies on the production of high carbon ferrochromium using melt circulation. Birmingham: University of Birmingham, 1997.
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Kouker, Wolfgang. Eine Studie zur Klimatologie der mittleren Atmosphäre mit Hilfe eines 3-D Zirkulationsmodells. Berlin: D. Reimer, 1988.
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Langematz, Ulrike. Eine dreidimensionale Modellsimulation der Zirkulation in der Mittleren Atmosphäre mit Aspekten troposphärisch-stratosphärischer Wechselwirkungen: (DK 551.506.7/551.510.53 ... Berlin: D. Reimer, 1991.
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Chŏng, Hyŏn-t'ae. Konggong tosŏgwan taech'ul yŏnch'e pangji mit hoesuyul hyangsang pangan yŏn'gu: Tosŏgwan Yŏn'guso 2009-yŏndo hyŏmnyŏk yŏn'gu, 2. Sŏul T'ŭkpyŏlsi: Tosŏgwan Yŏn'guso, 2009.
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Görgen, Klaus. Sensitivitätsstudien und Analyse von Atmosphäre-Meereis-Wechselwirkungen mit dem regionalen Atmosphärenmodell HIRHAM4 auf Basis eines neu entwickelten beobachtungsgestützten unteren Modellantriebs während ausgewählter Sommer über der Arktis, Laptewsee: Sensitivity studies and analysis of atmosphere-sea-ice-interactions with the regional atmospheric model HIRHAM4 using a newly developed observational lower boundary forcing dataset during selected summers over the Arctic/Laptev Sea. Bremen: Alfred-Wegener-Institut für Polar- und Meeresforschung, 2006.
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Holger, Fischer. Vergleichende Untersuchungen eines optimierten dynamisch-thermodynamischen Meereismodells mit Beobachtungen im Weddellmeer =: Comparison of an optimized dynamic-thermodynamic sea ice model with observations in the Weddell Sea. Bremerhaven: Alfred-Wegener-Institut für Polar- und Meeresforschung, 1995.
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Fieg, Kerstin. Der Ozean als Teil des gekoppelten Klimasystems: Versuch der Rekonstruktion der glazialen Zirkulation mit verschieden komplexen Atmosphärenkomponenten = The ocean as a part of the coupled climate system : an attempt to reconstruct the glacial circulation with different models of the atmosphere. Bremerhaven: Alfred-Wegener-Institut für Polar- und Meeresforschung, 1996.
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Weber, Anne-Katrin. Television before TV. Nieuwe Prinsengracht 89 1018 VR Amsterdam Nederland: Amsterdam University Press, 2022. http://dx.doi.org/10.5117/9789463727815.
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Television before TV rethinks the history of interwar television by exploring the medium’s numerous demonstrations organized at national fairs and international exhibitions in the late 1920s and 1930s. Building upon extensive archival research in Britain, Germany, and the United States, Anne-Katrin Weber analyses the sites where the new medium met its first audiences. She argues that public displays were central to television’s social construction; for the historian, the exhibitions therefore constitute crucial events to understand not only the medium’s pre-war emergence, but also its subsequent domestication in the post-war years. Designed as a transnational study, her book highlights the multiple circulations of artefacts and ideas across borders of democratic and totalitarian regimes alike. Richly illustrated with 100 photographs, Weber finally emphasizes that even without regular programmes, interwar television was widely seen.
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Kay, Hailbronner, Klein Eckart Dr, and Kokott Juliane, eds. Einwanderungskontrolle und Menschenrechte =: Immigration control and human rights : Beiträge anlässlich des Symposiums am 29./30. Juni 1998 in Potsdam, finanziert mit Unterstützung des German Marshall Fund der Vereinigten Staaten von Amerika und des Menschenrechtszentrums an der Universität Potsdam. Heidelberg: C.F. Müller, 1999.
Find full textBook chapters on the topic "MLT circulation"
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de Ruiter, Marike, and Camiel Jonk. "9 Middelen met effect op de circulatie." In Farmacotherapie voor de zorgprofessional, 185–215. Houten: Bohn Stafleu van Loghum, 2016. http://dx.doi.org/10.1007/978-90-368-1209-2_9.
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Norén, Fredrik. "Nordic Public Information: An Epistemic Community of Experiences and Ideas in the 1970s." In Nordic Media Histories of Propaganda and Persuasion, 73–95. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-05171-5_4.
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AbstractThis chapter studies the exchanges of ideas and experiences related to public information within the Nordic region and beyond. As an empirical case, the analytical focus centres on the Swedish Board of Public Information (Nämnden för samhällsinformation, 1971–1981) and traces the various contacts—through seminars, study visits, conferences, and so on—that the agency initiated and was part of during the 1970s. By examining the archival material through the concepts of epistemic community and circulation of knowledge, the analysis shows how issues of public information attracted various actors—which represented different social sectors (bureaucracy, advertising industry, academia, etc.) and different interests—that met across national borders in attempts to address challenges of communicating societal important information to citizens.
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Turner, Nigel M., Joke Kieboom, and A. Nusmeier. "C: De gestructureerde benadering van problemen met de circulatie." In Advanced Paediatric Life Support, 80–117. Houten: Bohn Stafleu van Loghum, 2022. http://dx.doi.org/10.1007/978-90-368-2771-3_4.
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Tacken, M. H. P., J. van der Bom, and T. Takken. "Conditietraining bij een kind met een univentriculair hart (Fontan-circulatie)." In Fysiotherapeutische casuïstiek, 1–7. Houten: Bohn Stafleu van Loghum, 2006. http://dx.doi.org/10.1007/978-90-313-8645-1_1.
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Diephuis, J. C. "Wat zijn de belangrijkste neurofysio-psychologische risico’s en klachten na een ingreep met extra-corporele circulatie?" In Vademecum permanente nascholing huisartsen, 166–68. Houten: Bohn Stafleu van Loghum, 2006. http://dx.doi.org/10.1007/978-90-313-8808-0_81.
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Bharatiraja, C., P. Sanjeevikumar, J. L. Munda, Lars Norum, and S. Raghu. "Mitigation of Circulating Current in Diode clamped MLI fed Induction Motor Drive Using Carrier Shifting PWM Techniques." In Advances in Systems, Control and Automation, 71–83. Singapore: Springer Singapore, 2017. http://dx.doi.org/10.1007/978-981-10-4762-6_6.
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Peixoto, Johne Jesus Mol, Natalia Barros Barony, Heric Henrique Souza e. Silva, Weslei Viana Gabriel, Carlos Antonio da Silva, Itavahn Alves da Silva, and Varadarajan Seshadri. "Assessment of Slag Entrainment in a RH Degasser Through Physical Modelling Using Circulating Fluids of Different Densities/Oil Systems for Simulating Steel Melt/Slag." In The Minerals, Metals & Materials Series, 121–31. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-51340-9_13.
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Seiler, Christian. "Cardiovascular physiology: regulation of coronary circulation." In ESC CardioMed, edited by Guido Grassi, 120–25. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780198784906.003.0023.
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This chapter reviews coronary circulatory structural and functional aspects with a focus on human physiology and on pathophysiology relating to ischaemic heart disease. During augmented myocardial oxygen demand (e.g. during physical exercise), oxygen extraction is enhanced only marginally due to high extraction at rest. Thus, the increased demand is met by augmented coronary blood flow. The structural design of the coronary artery tree is matched to myocardial perfusion at rest, and can be derived from an economic construction principle ubiquitously present in biology: the physiological or optimality principle of minimum work. Myocardial perfusion at rest amounts to 1 mL/min/g, the level of which is maintained over a broad range of coronary perfusion pressures between 60 and 140 mmHg (coronary autoregulation). Coronary flow at rest under different coronary pressure challenges is held constant by microcirculatory resistance adaptation. Likewise, coronary flow in response to augmented myocardial metabolic challenges is increased four- to fivefold (coronary flow reserve) by a reduction in microcirculatory resistance. Active regulation of coronary microcirculatory resistance results from a balance between vasodilator and vasoconstrictor stimuli exerted by metabolic signals from the myocardium, the vascular endothelium, and neurohumoral influences. An atherosclerotic coronary stenosis is a vascular resistance in series to the downstream microcirculatory resistance inducing an epicardial coronary pressure drop. At rest, normal coronary flow is maintained due to compensatory microvascular dilatation. Hence, the capacity for further microcirculatory dilatation under increased oxygen demand is limited, that is, coronary flow reserve is reduced.
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Spickett, Gavin P. "Tissue typing." In Oxford Handbook of Clinical Immunology and Allergy, 579–90. Oxford University Press, 2013. http://dx.doi.org/10.1093/med/9780199603244.003.0021.
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Introduction Matching procedures: detecting pre-formed circulating antibodies Mixed lymphocyte reaction (MLR) HTLp and CTLp frequency Tissue typing: serological methods Molecular HLA typing KIR typing HLA testing as a disease marker Human anti-animal antibodies Chimerism studies Useful websites • Key elements for successful transplantation are: •...
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MOINE, Florian. "La circulation internationale des publications enfantines de Casterman (1950-1970)." In Les maisons d’édition francophones au prisme de leurs archives, 157–72. Editions des archives contemporaines, 2022. http://dx.doi.org/10.17184/eac.6523.
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Fondée sur l’exploitation des riches archives du département international de la maison d’édition, cette étude met en évidence la stratégie éditoriale d’exportation du catalogue enfantin de Casterman depuis l’après-guerre jusqu’aux années 1980, à travers l’exemple des circulations internationales des Aventures de Tintin d’Hergé et de la collection « Farandole », qui abrite les albums de Martine. Cet exemple permet de saisir la place des cessions de droits dans la stratégie entrepreneuriale d’un éditeur industriel de l’enfance et ses effets sur la production, ainsi que d’apercevoir le développement d’une sociabilité éditoriale internationale.
Conference papers on the topic "MLT circulation"
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Farrow, Tom, Nurlan Gadimov, Kyriacos Agapiou, and Mukhtar Safarov. "Mitigating Lost Circulation Across Permeable Formations of the Gunashli Field in the Caspian Sea with a New Tailored Spacer System." In SPE Annual Caspian Technical Conference. SPE, 2021. http://dx.doi.org/10.2118/207017-ms.
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Abstract Cementing operations seek to minimize non-productive time (NPT) as part of the broad effort to optimize costs. A commonly encountered event that contributes to NPT is lost circulation. Lost circulation may often be associated, and treated, during drilling operations, but can occur during cementing practices, e.g. while running casing in the wellbore and/or circulating cement and treatment fluids. When fluids are lost to the formation and not appropriately cured, cementing objectives may not be met and, ultimately, zonal isolation can be compromised. Additional costs may be incurred to remediate the well construction and achieve a dependable barrier. It is, therefore, of great interest to develop and implement solutions which can facilitate the prevention and treatment of lost circulation. Described herein is the evaluation and use of a new tailored spacer system (TSS) engineered to effectively prevent lost circulation and maintain wellbore stability. The TSS was designed for use in cementing shallow water Caspian Sea wells with permeable formations and a history of losses. The spacer was subjected to conventional spacer tests and simulations including rheological measurements, compatibility assessments and fluid modeling to ensure job requirements would be met. Loss control tests were performed to verify the efficacy of the TSS to effectively prevent losses. All screenings demonstrated the TSS would be well-suited for the intended field application. The spacer system was successfully deployed in Caspian Sea wells and helped meet cementing objectives where conventional treatments failed.
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Farrow, Tom, Nurlan Gadimov, Kyriacos Agapiou, and Mukhtar Safarov. "Mitigating Lost Circulation Across Permeable Formations of the Gunashli Field in the Caspian Sea with a New Tailored Spacer System." In SPE Annual Caspian Technical Conference. SPE, 2021. http://dx.doi.org/10.2118/207017-ms.
Full textAbstract:
Abstract Cementing operations seek to minimize non-productive time (NPT) as part of the broad effort to optimize costs. A commonly encountered event that contributes to NPT is lost circulation. Lost circulation may often be associated, and treated, during drilling operations, but can occur during cementing practices, e.g. while running casing in the wellbore and/or circulating cement and treatment fluids. When fluids are lost to the formation and not appropriately cured, cementing objectives may not be met and, ultimately, zonal isolation can be compromised. Additional costs may be incurred to remediate the well construction and achieve a dependable barrier. It is, therefore, of great interest to develop and implement solutions which can facilitate the prevention and treatment of lost circulation. Described herein is the evaluation and use of a new tailored spacer system (TSS) engineered to effectively prevent lost circulation and maintain wellbore stability. The TSS was designed for use in cementing shallow water Caspian Sea wells with permeable formations and a history of losses. The spacer was subjected to conventional spacer tests and simulations including rheological measurements, compatibility assessments and fluid modeling to ensure job requirements would be met. Loss control tests were performed to verify the efficacy of the TSS to effectively prevent losses. All screenings demonstrated the TSS would be well-suited for the intended field application. The spacer system was successfully deployed in Caspian Sea wells and helped meet cementing objectives where conventional treatments failed.
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Barreiro, Jose A., John S. Knowles, Carl R. Johnson, Iain D. Gordon, and Lene K. Gjerde. "Successful Application of a Reinforced Composite Mat Pill Technology for Lost Circulation Control in the Norwegian Continental Shelf." In SPE/IADC International Drilling Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/204062-ms.
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Abstract An operator in the Norwegian continental shelf (NCS) required sufficient zonal isolation around a casing shoe to accommodate subsequent targeted injection operations. Located in the Ivar Aasen field, and classified as critical, the well had a 9 ⅝-in. casing shoe set in the depleted Skagerrak 2 reservoir. The lost circulation risk was high during cementing because the Hugin formation, located above the reservoir, contained 40 m [~ 131.2 ft] of highly porous and permeable sandstone. During previous operations in the field, lost circulation was observed before and during the casing running and cementing operations. After unsuccessful attempts to cure the losses with various lost circulation materials, a new solution was proposed to target the specific lost circulation problem by combining two types of reinforced composite mat pill (RCMP) technology. Specifically, the first type of RCMP technology was engineered for use in the viscous preflush spacer, and the second was applied to the cement slurry itself. Working in synergy, the RCMP systems mitigated the risk of incomplete zonal isolation. With no losses observed upon reaching total depth (TD) for the 12 ¼-in. hole, the 9 ⅝-in. casing was run with a reamer shoe and 15 rigid centralizers. Between 2700 and 2728 m [~ 8,858 and 8,950 ft] measured depth (MD), the rig observed constant drag of 30 to 40 MT whilst working the casing down, and circulation was completely lost before partial returns were eventually observed. The rig continued to work the string down to the planned landing depth at 3897 m [~ 12,785 ft] MD. Precementing circulation ensued with staged pump rates increasing at 100-L/min [~ 0.6-bbl/min] intervals up to 1400 L/min [~ 8.8 bbl/min], which induced losses at a rate of 6.5 m3/hour [~ 40 bbl/hour]). Subsequently, the flow rate was reduced to 1300 L/min [~ 8.1 bbl/min], and the annular volume was circulated 2.6 times with full returns. Attempts to reduce equivalent circulating density (ECD) ahead of the cementing operation were implemented at 1300 L/min [~ 8.1 bbl/min] using a low-density, low-rheology oil-based drilling fluid pill. However, a significant loss rate of 18.0 m3/hour [~113 bbl/hour] was observed. The flow rate was reduced to 950 L/min [~ 6.0 bbl/min], and partial circulation was recovered. After the spacer and cement had reached the annulus, full returns were immediately observed and continued until the top plug was successfully bumped. Acoustic logging determined that the operation had achieved the primary job objective of establishing the required length of hydraulically isolating cement in the annulus. Lost circulation is a costly problem that can be difficult to solve, even with the wide variety of technologies available (Vidick, B., Yearwood, J. A., and Perthuis, H. 1988. How To Solve Lost Circulation Problems. SPE-17811-MS). This case study demonstrates a successful solution. The operator will be able to incorporate lessons learned and best practices into future operations, and these lessons and practices will be useful to other operators with similar circumstances.
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Schuchinsky, Alexander. "Stacked multistage lumped element circulator." In 2012 IEEE/MTT-S International Microwave Symposium - MTT 2012. IEEE, 2012. http://dx.doi.org/10.1109/mwsym.2012.6259580.
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Muhammad, Faraz Khan, Zahid Mohammed Karajagi, Surya Pallapothu, Hafez Mohamed, Pierre Klem, and Umar Arshad. "Engineered Reinforced Composite Mat Pills to Effectively Combat Losses While Drilling in Qatar." In IADC/SPE Asia Pacific Drilling Technology Conference. SPE, 2021. http://dx.doi.org/10.2118/201030-ms.
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Abstract Drilling into fractures and fissures in carbonate reservoirs with lateral pore pressure variations is a major challenge. Accurately predicting and managing fracture initiation and fracture closure pressure is not practically feasible in naturally fractured carbonate rocks. Local fracture closure pressure (FCP, minimum in situ stress) around fractures are much lower than the mean value of FCP for the area, as observed in the Al Shaheen field. Drilling operators are experiencing massive lost circulation resulting in potential formation damage; and cost overruns. To address these lost circulation instances, modern lost circulation pills must be implemented. Drilling through the natural fractures within parts of the Shuaiba limestone reservoir usually results in significant drilling fluid losses, up to 50 m3/h. Lateral pore pressure variation causes dynamic inflow conditions within the wellbore, which make plugging fractures difficult. In addressing these lost circulation challenges, various approaches were previously used, notably reducing the hydrostatic pressure of fluids column, utilizing lighter weight drilling fluids, reducing the penetration of fluids into fractures with the use of various lost circulation materials, and the use of thixotropic cement slurries and lightweight high-solids-content cement slurries. Conventional lost circulation treatments provided very limited success under these conditions. An engineered composite fiber-based lost circulation pill with an innovative blend of fibers and sized solids to bridge and plug thief zones has been developed to address these lost circulation challenges. This pill was designed to be pumped through either a dummy bottomhole assembly (BHA) or through bypass circulation ports above the BHA with total flow area of 1.571 in2. These pills have been successfully used to mitigate losses while drilling as well as to achieve an incremental equivalent static density up to 144 kg/m3 to drill and cement the section. An impermeable grid created by this system was able to withstand the additional pressures. As a result, all the wells treated with these pills in the field were successfully drilled and cemented. After establishing the field specific guidelines over 2 years, continuous success was replicated in other wells for all the operator's rigs in Qatar.
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Kim, Hyoung Tae, Han Seo, Sunghyuk Im, Bo Wook Rhee, and Jae Eun Cha. "Experimental Study of Moderator Circulation in CANDU6 Calandria Tank." In 2014 22nd International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icone22-31140.
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As a CANDU6 reactor has a high pressure primary cooling system and an independently cooled moderator system, the moderator in the calandria would act as a supplementary heat sink during a loss of coolant accident (LOCA) if the primary cooling and emergency coolant injection systems fail to remove the decay heat from the fuel. For the safety concern it is required to predict the 3-dimensional velocity and temperature distribution of moderator fluid to confirm the effectiveness of moderator heat sink. Korea Atomic Energy Research Institute (KAERI) is carrying out a scaled-down moderator test program to simulate the CANDU6 moderator circulation phenomena during steady state operation and accident conditions. This research program includes the construction of the Moderator Circulation Test (MCT) facility, production of the validation data for self-reliant CFD tools, and development of optical measurement system using the Particle Image Velocimetry (PIV). In the present work the PIV technique is used to measure the velocity distributions in the scaled moderator tank of MCT under iso-thermal test conditions. The preliminary PIV measurement data are obtained and compared with CFX code predictions.
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Hawari, A., D. Carpenter, K. Robb, R. Scarlat, and C. Forsberg. "Building a Molten-Salt Forced-Circulation Loop for the MIT Reactor." In 2020 ANS Virtual Winter Meeting. AMNS, 2020. http://dx.doi.org/10.13182/t123-32945.
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Boyajian, Taline, Didier Vincent, Sophie Neveu, Martine LeBerre, and Jean-Jacques Rousseau. "Coplanar circulator made from composite magnetic material." In 2011 IEEE/MTT-S International Microwave Symposium - MTT 2011. IEEE, 2011. http://dx.doi.org/10.1109/mwsym.2011.5972759.
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Boyajian, T., D. Vincent, S. Neveu, M. Le Berre, and J. Rousseau. "Coplanar circulator made from composite magnetic material." In 2011 IEEE/MTT-S International Microwave Symposium - MTT 2011. IEEE, 2011. http://dx.doi.org/10.1109/mwsym.2011.5973323.
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Wang, Xinkun, and Junhong Li. "Numerical Calculation of Triangle Circulation Drip Irrigation Emitters." In ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30581.
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Based on the hydraulic characteristics of triangle circulation, sudden-expansion pipe and sudden contraction pipe, Construct a drip irrigation emitter with strong turbulent flow, large over-current cross-section and strong anti-clogging ability. Triangular circulation flow path emitters for the key structural parameters for the factors, application of computer numerical fluid dynamics CFD software FLUENT6.3, simulate triangular circulation flow channel structure, analyze the influence of various structural parameters on hydraulic performance of emitters, flow index, flow rate and the anti-clogging ability. The results show that increase unit cusp, unit chamfer, the flow index increased, but the effect to varying degrees; inlet dimension increase, flow index reduced; flow channel depth and flow channel width increases, the discharge increases. Increase unit cusp, unit chamfered, can improve the anti-clogging performance of emitters. Based on the above results, to design an emitter structure with good performance, and its numerical simulation analysis, the flow index, flow rate and anti-clogging ability have met the requirements of drip irrigation. Provide a theoretical basis for the triangle circulation emitter structure design and quantitative analysis. The research has a positive meaning for energy conservation.
Reports on the topic "MLT circulation"
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Chen, Z., S. E. Grasby, C. Deblonde, and X. Liu. AI-enabled remote sensing data interpretation for geothermal resource evaluation as applied to the Mount Meager geothermal prospective area. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/330008.
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The objective of this study is to search for features and indicators from the identified geothermal resource sweet spot in the south Mount Meager area that are applicable to other volcanic complexes in the Garibaldi Volcanic Belt. A Landsat 8 multi-spectral band dataset, for a total of 57 images ranging from visible through infrared to thermal infrared frequency channels and covering different years and seasons, were selected. Specific features that are indicative of high geothermal heat flux, fractured permeable zones, and groundwater circulation, the three key elements in exploring for geothermal resource, were extracted. The thermal infrared images from different seasons show occurrence of high temperature anomalies and their association with volcanic and intrusive bodies, and reveal the variation in location and intensity of the anomalies with time over four seasons, allowing inference of specific heat transform mechanisms. Automatically extracted linear features using AI/ML algorithms developed for computer vision from various frequency bands show various linear segment groups that are likely surface expression associated with local volcanic activities, regional deformation and slope failure. In conjunction with regional structural models and field observations, the anomalies and features from remotely sensed images were interpreted to provide new insights for improving our understanding of the Mount Meager geothermal system and its characteristics. After validation, the methods developed and indicators identified in this study can be applied to other volcanic complexes in the Garibaldi, or other volcanic belts for geothermal resource reconnaissance.
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Chapman, Ray, Phu Luong, Sung-Chan Kim, and Earl Hayter. Development of three-dimensional wetting and drying algorithm for the Geophysical Scale Transport Multi-Block Hydrodynamic Sediment and Water Quality Transport Modeling System (GSMB). Engineer Research and Development Center (U.S.), July 2021. http://dx.doi.org/10.21079/11681/41085.
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The Environmental Laboratory (EL) and the Coastal and Hydraulics Laboratory (CHL) have jointly completed a number of large-scale hydrodynamic, sediment and water quality transport studies. EL and CHL have successfully executed these studies utilizing the Geophysical Scale Transport Modeling System (GSMB). The model framework of GSMB is composed of multiple process models as shown in Figure 1. Figure 1 shows that the United States Army Corps of Engineers (USACE) accepted wave, hydrodynamic, sediment and water quality transport models are directly and indirectly linked within the GSMB framework. The components of GSMB are the two-dimensional (2D) deep-water wave action model (WAM) (Komen et al. 1994, Jensen et al. 2012), data from meteorological model (MET) (e.g., Saha et al. 2010 - http://journals.ametsoc.org/doi/pdf/10.1175/2010BAMS3001.1), shallow water wave models (STWAVE) (Smith et al. 1999), Coastal Modeling System wave (CMS-WAVE) (Lin et al. 2008), the large-scale, unstructured two-dimensional Advanced Circulation (2D ADCIRC) hydrodynamic model (http://www.adcirc.org), and the regional scale models, Curvilinear Hydrodynamics in three dimensions-Multi-Block (CH3D-MB) (Luong and Chapman 2009), which is the multi-block (MB) version of Curvilinear Hydrodynamics in three-dimensions-Waterways Experiments Station (CH3D-WES) (Chapman et al. 1996, Chapman et al. 2009), MB CH3D-SEDZLJ sediment transport model (Hayter et al. 2012), and CE-QUAL Management - ICM water quality model (Bunch et al. 2003, Cerco and Cole 1994). Task 1 of the DOER project, “Modeling Transport in Wetting/Drying and Vegetated Regions,” is to implement and test three-dimensional (3D) wetting and drying (W/D) within GSMB. This technical note describes the methods and results of Task 1. The original W/D routines were restricted to a single vertical layer or depth-averaged simulations. In order to retain the required 3D or multi-layer capability of MB-CH3D, a multi-block version with variable block layers was developed (Chapman and Luong 2009). This approach requires a combination of grid decomposition, MB, and Message Passing Interface (MPI) communication (Snir et al. 1998). The MB single layer W/D has demonstrated itself as an effective tool in hyper-tide environments, such as Cook Inlet, Alaska (Hayter et al. 2012). The code modifications, implementation, and testing of a fully 3D W/D are described in the following sections of this technical note.
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Yaron, Zvi, Martin P. Schreibman, Abigail Elizur, and Yonathan Zohar. Advancing Puberty in the Black Carp (Mylopharyngodon Piceus) and the Striped Bass (Morone Saxatilis). United States Department of Agriculture, August 1993. http://dx.doi.org/10.32747/1993.7568102.bard.
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The black carp (bc)GtH IIb cDNA was amplified and isolated, cloned and sequenced. Comparison of the bcGtH IIb deduced a.a. sequence with that of GtH IIb from other teleosts revealed high homology to cyprinid species and a lower homology to salmonid or perciform fish. The gene coding for the GtH IIb was isolated and sequenced. Three bc recombinant phages which hybridized to the goldfish GtH Ib cDNA probe were isolated and are currently being characterized. The region coding for the mature GtH IIb was expressed in a bacterial expression vector resulting in the production of a recombinant protein. In vitro folding resulted in a protein only 1.3% of which displaced the native common carp GtH II in a RIA. Therefore, the common carp GtH RIA was utilized for the physiological studies at the current phase of the project. Two non-functional sites were identified along the brain-pituitary gonadal axis in the immature black carp. The pituitary is refractory to GnRH stimulation due to a block proximal to the activation of PKA and PKC probably at the level of GnRH receptors. The gonads, although capable of producing steroids, are refractory to gonadotropic stimulation but do respond to cAMP antagonists, indicating a block at the GtH receptor level. Attempts to advance puberty in 2 and 3 y old black carp showed that testosterone (T) stimulates GtH synthesis in the pituitary and increases its sensitivity to GnRh. A 2 month treatment combining T+GnRH increased the circulating GFtH level in 3 y old fish. Addition of domperidone to such a treatment facilitated both the accumulation of GtH in the pituitary and its response to GnRH. The cDNA of striped bass GtH a, Ib and IIb subunits were amplified, isolated, cloned and sequenced, and their deduced a.a. sequences were compared with those of other teleosts. A ribonuclease protection assay was developed for a sensitive and simultaneous determination of all GtH subunits, and of b-actin mRNAs of the striped bass. GnRH stimulated dramatically the expression of the a and GtH IIb subunits but the level of GtH Ib mRNA increased only moderately. These findings suggest that GtH-II, considered in salmonids to be involved only in final stages of gametogenesis, can be induced by GnRH to a higher extent than GtH-I in juvenile striped bass. The native GtH II of the striped bass was isolated and purified, and an ELISA for its determination was developed. The production of all recombinant striped bass GtH subunits is in progress using the insect cell (Sf9) culture and the BAC-TO-BAC baculovirus expression system. A recombinant GtH IIb subunit has been produced already, and its similarity to the native subunit was confirmed. The yield of the recombinant glycoprotein can reach 3.5 mg/ml after 3 days culture. All male striped bass reach puberty after 3 y. However, precocious puberty was discovered in 1 and 2 y old males. Females become vitellogenic during their 4th year. In immature 2 y old females, T treatment elevates the pituitary GtH II content while GnRH only potentiates the effect. However, in males GnRH and not T affects GtH accumulation in the pituitary. Neither GnRH, nor T treatment resulted in gonadal growth in 2 y old striped bass, indicating that either the accumulated GtH II was not released, or if released, the gonads were refractory to GtH stimulation, similar to the situation in the immature black carp. In 3 y old female striped bass, 150 day GnRHa treatment resulted in an increase in GSI, while T treatment, with or without GnRHa, resulted in a decrease in oocyte diameter, similar to the effect seen in the black carp. Further attempts to advance puberty in both fish species should take into account the positive effect of T on pituitary GtH and its negative effect of ovarian growth.
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Yaron, Zvi, Abigail Elizur, Martin Schreibman, and Yonathan Zohar. Advancing Puberty in the Black Carp (Mylopharyngodon piceus) and the Striped Bass (Morone saxatilis). United States Department of Agriculture, January 2000. http://dx.doi.org/10.32747/2000.7695841.bard.
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Both the genes and cDNA sequences encoding the b-subunits of black carp LH and FSH were isolated, cloned and sequenced. Sequence analysis of the bcFSHb and LHb5'flanking regions revealed that the promoter region of both genes contains canonical TATA sequences, 30 bp and 17 bp upstream of the transcription start site of FSHb and LHb genes, respectively. In addition, they include several sequences of cis-acting motifs, required for inducible and tissue-specific transcriptional regulation: the gonadotropin-specific element (GSE), GnRH responsive element (GRE), half sites of estrogen and androgen response elements, cAMP response element, and AP1. Several methods have been employed by the Israeli team to purify the recombinant b subunits (EtOH precipitation, gel filtration and lentil lectin). While the final objective to produce pure recombinantGtH subunits has not yet been achieved, we have covered much ground towards this goal. The black carp ovary showed a gradual increase in both mass and oocyte diameter. First postvitellogenic oocytes were found in 5 yr old fish. At this age, the testes already contained spermatozoa. The circulating LH levels increased from 0.5 ng/ml in 4 yr old fish to >5ng/ml in 5 yr old fish. In vivo challenge experiments in black carp showed the initial LH response of the pituitary to GnRH in 4 yr old fish. The response was further augmented in 5 yr old fish. The increase in estradiol level in response to gonadotropic stimulation was first noted in 4 yr old fish but this response was much stronger in the following year. In vivo experiments on the FSHb and LHb mRNA levels in response to GnRH were carried out on common carp as a model for synchronom spawning cyprinids. These experiments showed the prevalence of FSHP in maturing fish while LHP mRNA was prevalent in mature fish, especially in females. The gonadal fat-pad was found to originate from the retroperitoneal mesoderm and not from the genital ridge, thus differing from that reported in certain amphibians This tissue possibly serves as the major source of sex steroids in the immature black carp. However, such a function is taken over by the developing gonads in 4 yr old fish. In the striped bass, we described the ontogeny of the neuro-endocrine parameters along the brain-pituitary-gonadal axis during the first four years of life, throughout gonadal development and the onset of puberty. We also described the responsiveness of the reproductive axis to long-term hormonal manipulations at various stages of gonadal development. Most males reached complete sexual maturity during the first year of life. Puberty was initiated during the third year of life in most females, but this first reproductive cycle did not lead to the acquisition of full sexual maturity. This finding indicates that more than one reproductive cycle may be required before adulthood is reached. Out of the three native GnRHs present in striped bass, only sbGnRH and cGnRH II increased concomitantly with the progress of gonadal development and the onset of puberty. This finding, together with data on GtH synthesis and release, suggests that while sbGnRH and cGnRH II may be involved in the regulation of puberty in striped bass, these neuropeptides are not limiting factors to the onset of puberty. Plasma LH levels remained low in all fish, suggesting that LH plays only a minor role in early gonadal development. This hypothesis was further supported by the finding that experimentally elevated plasma LH levels did not result in the induction of complete ovarian and testicular development. The acquisition of complete puberty in 4 yr old females was associated with a rise in the mRNA levels of all GtH subunit genes, including a 218-fold increase in the mRNA levels of bFSH. mRNA levels of the a and PLH subunits increased only 11- and 8-fold, respectively. Although data on plasma FSH levels are unavailable, the dramatic increase in bFSH mRNA suggests a pivotal role for this hormone in regulating the onset and completion of puberty in striped bass. The hormonal regulation of the onset of puberty and of GtH synthesis and release was studied by chronic administration of testosterone (T) and/or an analog of gonadotropin-releasing hormone (G). Sustained administration of T+G increased the mRNA levels of the PLH subunit to the values characteristic of sexually mature fish, and also increased the plasma levels of LH. However, these changes did not result in the acceleration of sexual maturation. The mRNA levels of the bFSH subunit were slightly stimulated, but remained about 1/10 of the values characteristic of sexually mature fish. It is concluded that the stimulation of FSH gene expression and release does not lead to the acceleration of sexual maturity, and that the failure to sufficiently stimulate the bFSH subunit gene expression may underlie the inability of the treatments to advance sexual maturity. Consequently, FSH is suggested to be the key hormone to the initiation and completion of puberty in striped bass. Future efforts to induce precocious puberty in striped bass should focus on understanding the regulation of FSH synthesis and release and on developing technologies to induce these processes. Definite formulation of hormonal manipulation to advance puberty in the striped bass and the black carp seems to be premature at this stage. However, the project has already yielded a great number of experimental tools of DNA technology, slow-release systems and endocrine information on the process of puberty. These systems and certain protocols have been already utilized successfully to advance maturation in other fish (e.g. grey mullet) and will form a base for further study on fish puberty.