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Journal articles on the topic "VDrama"
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Rayego-Mateos, Sandra, Jose Luis Morgado-Pascual, José Manuel Valdivielso, Ana Belén Sanz, Enrique Bosch-Panadero, Raúl R. Rodrigues-Díez, Jesús Egido, Alberto Ortiz, Emilio González-Parra, and Marta Ruiz-Ortega. "TRAF3 Modulation: Novel Mechanism for the Anti-inflammatory Effects of the Vitamin D Receptor Agonist Paricalcitol in Renal Disease." Journal of the American Society of Nephrology 31, no. 9 (July 6, 2020): 2026–42. http://dx.doi.org/10.1681/asn.2019111206.
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BackgroundCKD leads to vitamin D deficiency. Treatment with vitamin D receptor agonists (VDRAs) may have nephroprotective and anti-inflammatory actions, but their mechanisms of action are poorly understood.MethodsModulation of the noncanonical NF-κB2 pathway and its component TNF receptor–associated factor 3 (TRAF3) by the VDRA paricalcitol was studied in PBMCs from patients with ESKD, cytokine-stimulated cells, and preclinical kidney injury models.ResultsIn PBMCs isolated from patients with ESKD, TRAF3 protein levels were lower than in healthy controls. This finding was associated with evidence of noncanonical NF-κB2 activation and a proinflammatory state. However, PBMCs from patients with ESKD treated with paricalcitol did not exhibit these features. Experiments in cultured cells confirmed the link between TRAF3 and NF-κB2/inflammation. Decreased TRAF3 ubiquitination in K48-linked chains and cIAP1-TRAF3 interaction mediated the mechanisms of paricalcitol action.TRAF3 overexpression by CRISPR/Cas9 technology mimicked VDRA’s effects. In a preclinical model of kidney injury, paricalcitol inhibited renal NF-κB2 activation and decreased renal inflammation. In VDR knockout mice with renal injury, paricalcitol prevented TRAF3 downregulation and NF-κB2–dependent gene upregulation, suggesting a VDR-independent anti-inflammatory effect of paricalcitol.ConclusionsThese data suggest the anti-inflammatory actions of paricalcitol depend on TRAF3 modulation and subsequent inhibition of the noncanonical NF-κB2 pathway, identifying a novel mechanism for VDRA’s effects. Circulating TRAF3 levels could be a biomarker of renal damage associated with the inflammatory state.
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Banks, Mindy, and Stuart M. Sprague. "Vitamin D and Peritoneal Dialysis." Peritoneal Dialysis International: Journal of the International Society for Peritoneal Dialysis 28, no. 2_suppl (March 2008): 33–37. http://dx.doi.org/10.1177/089686080802802s06.
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Chronic kidney disease – mineral and bone disorder (CKD–MBD) is a cause of significant morbidity and mortality in patients with long-standing kidney disease. Management of secondary hyperparathyroidism includes the use of phosphorus-binding agents and treatment with activated vitamin D compounds, better referred to as vitamin D receptor agonists (VDRAs). In an effort to maximize the therapeutic response while reducing the adverse effects of calcitriol, the naturally synthesized hormone, the use of intravenous administration and several selective VDRAs have been developed. Recently, oral preparations of these selective VDRAs have become available, enabling their use in the peritoneal dialysis (PD) population. The present report reviews the data concerning the use of oral VDRAs for the treatment of hyperparathyroidism in PD patients. The data, although limited, appear to support the use of oral paricalcitol as the VDRA in PD patients. In addition, traditional teaching focuses only on therapy with VDRAs, ignoring vitamin D replacement in CKD stage 5. However, given the potential benefits of calcidiol (25-OH-D) repletion and the rampant 25-OH-D deficiency in the PD population, our opinion is that screening for and treating that deficiency should extend beyond early CKD and also include PD patients.
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Lim, Kenneth, Guerman Molostvov, Maria Lubczanska, Simon Fletcher, Rosemary Bland, Thomas F. Hiemstra, and Daniel Zehnder. "Impaired arterial vitamin D signaling occurs in the development of vascular calcification." PLOS ONE 15, no. 11 (November 19, 2020): e0241976. http://dx.doi.org/10.1371/journal.pone.0241976.
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Conflicting data exists as to whether vitamin D receptor agonists (VDRa) are protective of arterial calcification. Confounding this, is the inherent physiological differences between human and animal experimental models and our current fragmented understanding of arterial vitamin D metabolism, their alterations in disease states and responses to VDRa’s. Herein, the study aims to address these problems by leveraging frontiers in human arterial organ culture models. Human arteries were collected from a total of 24 patients (healthy controls, n = 12; end-stage CKD, n = 12). Cross-sectional and interventional studies were performed using arterial organ cultures treated with normal and calcifying (containing 5mmol/L CaCl2 and 5mmol/L β-glycerophosphate) medium, ex vivo. To assess the role of VDRa therapy, arteries were treated with either calcitriol or paricalcitol. We found that human arteries express a functionally active vitamin D system, including the VDR, 1α-hydroxylase and 24-hydroxylase (24-OHase) components and these were dysregulated in CKD arteries. VDRa therapy increased VDR expression in healthy arteries (p<0.01) but not in CKD arteries. Arterial 1α-OHase (p<0.05) and 24-OHase mRNA and protein expression were modulated differentially in healthy and CKD arteries by VDRa therapy. VDRa exposure suppressed Runx2 and MMP-9 expression in CKD arteries, however only paricalcitol suppressed MMP-2. VDRa exposure did not modulate arterial calcification in all organ culture models. However, VDRa reduced expression of senescence associated β-galactosidase (SAβG) staining in human aortic-smooth muscle cells under calcifying conditions, in vitro. In conclusion, maladaptation of arterial vitamin D signaling components occurs in CKD. VDRa exposure can exert vasculo-protective effects and seems critical for the regulation of arterial health in CKD.
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Morgado-Pascual, Jose L., Sandra Rayego-Mateos, Jose M. Valdivielso, Alberto Ortiz, Jesus Egido, and Marta Ruiz-Ortega. "Paricalcitol Inhibits Aldosterone-Induced Proinflammatory Factors by Modulating Epidermal Growth Factor Receptor Pathway in Cultured Tubular Epithelial Cells." BioMed Research International 2015 (2015): 1–13. http://dx.doi.org/10.1155/2015/783538.
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Chronic kidney disease is characterized by Vitamin D deficiency and activation of the renin-angiotensin-aldosterone system. Increasing data show that vitamin D receptor agonists (VDRAs) exert beneficial effects in renal disease and possess anti-inflammatory properties, but the underlying mechanism remains unknown. Emerging evidence suggests that “a disintegrin and metalloproteinase” (ADAM)/epidermal growth factor receptor (EGFR) signalling axis contributes to renal damage. Aldosterone induces EGFR transactivation regulating several processes including cell proliferation and fibrosis. However, data on tubular epithelial cells is scarce. We have found that, in cultured tubular epithelial cells, aldosterone induced EGFR transactivation via TGF-α/ADAM17. Blockade of the TGF-α/ADAM17/EGFR pathway inhibited aldosterone-induced proinflammatory gene upregulation. Moreover, among the potential downstream mechanisms, we found that TGF-α/ADAM17/EGFR inhibition blocked ERK and STAT-1 activation in response to aldosterone. Next, we investigated the involvement of TGF-α/ADAM17/EGFR axis in VDRA anti-inflammatory effects. Preincubation with the VDRA paricalcitol inhibited aldosterone-induced EGFR transactivation, TGF-α/ADAM-17 gene upregulation, and downstream mechanisms, including proinflammatory factors overexpression. In conclusion, our data suggest that the anti-inflammatory actions of paricalcitol in tubular cells could depend on the inhibition of TGF-α/ADAM17/EGFR pathway in response to aldosterone, showing an important mechanism of VDRAs action.
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Sprague, Stuart M., Adrian C. Covic, Jürgen Floege, Markus Ketteler, Jaco Botha, Edward M. Chong, and Anjay Rastogi. "Pharmacodynamic Effects of Sucroferric Oxyhydroxide and Sevelamer Carbonate on Vitamin D Receptor Agonist Bioactivity in Dialysis Patients." American Journal of Nephrology 44, no. 2 (2016): 104–12. http://dx.doi.org/10.1159/000447600.
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Background: Many patients with chronic kidney disease are prescribed vitamin D receptor agonists (VDRAs) for the management of secondary hyperparathyroidism. Oral phosphate binders may interact with, and potentially reduce the therapeutic activity of, oral VDRAs. This post hoc analysis of a Phase 3 study evaluated the pharmacodynamic effects of the iron-based phosphate binder sucroferric oxyhydroxide (SFOH) and sevelamer (SEV) carbonate on VDRA activity in dialysis patients. Methods: One thousand and fifty nine patients were randomized to SFOH 1.0-3.0 g/day (n = 710) or SEV 2.4-14.4 g/day (n = 349) for up to 52 weeks. Potential interactions of SFOH and SEV with VDRAs were assessed using serum intact parathyroid hormone (iPTH) concentrations as a pharmacodynamic biomarker. Three populations of SFOH- and SEV-treated patients were analyzed: Population 1 (n = 187), patients taking concomitant stable doses of oral VDRAs only; Population 2 (n = 250), patients taking no concomitant VDRAs; Population 3 (n = 68), patients taking concomitant stable doses of intravenous paricalcitol only. Populations were compared using a mixed-effects model to obtain the least squares mean change in iPTH from baseline to Week 52. Differences between treatment groups were also compared. Results: In Population 1, iPTH decreased from baseline to Week 52 in the SFOH group (-25.3 pg/ml) but increased in the SEV group (89.8 pg/ml) (p = 0.02). In Population 2, iPTH increased to a similar extent in both treatment groups. In Population 3, iPTH concentrations in both treatment groups decreased to a similar degree (-29.6 and -11.4 pg/ml for SFOH and SEV, respectively; p = 0.87). Conclusions: In contrast with SEV, SFOH did not appear to impact the iPTH-lowering effect of oral VDRAs.
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Cozzolino, Mario, Florjan Mehmeti, Paola Ciceri, Elisa Volpi, Andrea Stucchi, Irene Brenna, and Daniele Cusi. "The Effect of Paricalcitol on Vascular Calcification and Cardiovascular Disease in Uremia: Beyond PTH Control." International Journal of Nephrology 2011 (2011): 1–5. http://dx.doi.org/10.4061/2011/269060.
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Secondary hyperparathyroidism is a systemic disorder that associates with bone and cardiovascular disease, including arterial calcification. Treatment with calcitriol, the active form of vitamin D, reduces parathyroid hormone levels, but may result in elevations in serum calcium and phosphorus, increasing the risk of vascular calcification in dialysis patients. New vitamin D receptor activators (VDRAs) have been developed and investigated with the rationale to treat high serum PTH levels, with a reduced risk of hypercalcemia and hyperphosphatemia. Paricalcitol is a selective VDRA that suppresses PTH secretion with minimal increases on serum calcium and phosphate. Moreover, paricalcitol prevents vascular calcification in experimental models of renal failure, compared with calcitriol.
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Wu-Wong, J. Ruth, Yung-wu Chen, and Jerry L. Wessale. "Vitamin D receptor agonist VS-105 improves cardiac function in the presence of enalapril in 5/6 nephrectomized rats." American Journal of Physiology-Renal Physiology 308, no. 4 (February 15, 2015): F309—F319. http://dx.doi.org/10.1152/ajprenal.00129.2014.
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Vitamin D receptor (VDR) agonists (VDRAs) are commonly used to manage hyperparathyroidism secondary to chronic kidney disease (CKD). Patients with CKD experience extremely high risks of cardiovascular morbidity and mortality. Clinical observations show that VDRA therapy may be associated with cardio-renal protective and survival benefits in patients with CKD. The 5/6 nephrectomized (NX) Sprague-Dawley rat with established uremia exhibits elevated serum parathyroid hormone (PTH), hypertension, and abnormal cardiac function. Treatment of 5/6 NX rats with VS-105, a novel VDRA (0.05 and 0.5 μg/kg po by gavage), once daily for 8 wk in the presence or absence of enalapril (30 mg/kg po via drinking water) effectively suppressed serum PTH without raising serum calcium. VS-105 alone reduced systolic blood pressure (from 174 ± 6 to 145 ± 9 mmHg, P < 0.05) as effectively as enalapril (from 174 ± 6 to 144 ± 7 mmHg, P < 0.05). VS-105 improved cardiac functional parameters such as E/A ratio, ejection fraction, and fractional shortening with or without enalapril. Enalapril or VS-105 alone significantly reduced left ventricular hypertrophy (LVH); VS-105 plus enalapril did not further reduce LVH. VS-105 significantly reduced both cardiac and renal fibrosis. The lack of hypercalcemic toxicity of VS-105 is due to its lack of effects on stimulating intestinal calcium transport and inducing the expression of intestinal calcium transporter genes such as Calb3 and TRPV6. These studies demonstrate that VS-105 is a novel VDRA that may provide cardiovascular benefits via VDR activation. Clinical studies are required to confirm the cardiovascular benefits of VS-105 in CKD.
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Cianciolo, Giuseppe, Andrea Galassi, Irene Capelli, Maria Laura Angelini, Gaetano La Manna, and Mario Cozzolino. "Vitamin D in Kidney Transplant Recipients: Mechanisms and Therapy." American Journal of Nephrology 43, no. 6 (2016): 397–407. http://dx.doi.org/10.1159/000446863.
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Chronic kidney disease-mineral and bone disorder (CKD-MBD) is common in kidney transplant recipients (KTRs), where secondary hyperparathyroidism (HPTH) and post-transplantation bone disease (PTBD) are potential effectors of both graft and vascular aging. Reduced 25(OH)D levels are highly prevalent in KTRs. Experimental and clinical evidence support the direct involvement of deranged vitamin D metabolism in CKD-MBD among KTRs. This review analyzes the pathophysiology of vitamin D derangement in KTRs and its fall out on patient and graft outcome, highlighting the roles of both nutritional and active vitamin D compounds to treat PTBD, cardiovascular disease (CVD) and graft dysfunction. Fibroblast growth factor-23-parathyroid hormone (PTH)-vitamin D axis, immunosuppressive therapy and previous bone status have been associated with PTBD. Although several studies reported reduced PTH levels in KTRs receiving nutritional vitamin D, its effects on bone mineral density (BMD) remain controversial. Active vitamin D reduced PTH levels and increased BMD after transplantation, but paricalcitol treatment was not accompanied by benefits on osteopenia. Vitamin D is considered protective against CVD due to the widespread pleiotropic effects, but data among KTRs remain scanty. Although vitamin deficiency is associated with lower glomerular filtration rate (GFR) and faster estimated GFR decline and data on the anti-proteinuric effects of vitamin D receptor activation (VDRA) in KTRs sound encouraging, reports on related improvement on graft survival are still lacking. Clinical data support the efficacy of VDRA against HPTH and show promising evidence of VDRA's effect in counteracting post-transplant proteinuria. New insights are mandatory to establish if the improvement of surrogate outcomes will translate into better patient and graft outcome.
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Inaguma, Daijo, Yoshitaka Tatematsu, Naoki Okamoto, Soshiro Ogata, Hideki Kawai, Eiichi Watanabe, Yukio Yuzawa, Midori Hasegawa, and Naotake Tsuboi. "Multicentre, open-label, randomised, controlled trial to compare early intervention with calcimimetics and conventional therapy in preventing coronary artery calcification in patients with secondary hyperparathyroidism (UPCOMING): a study protocol." BMJ Open 14, no. 1 (January 2024): e076962. http://dx.doi.org/10.1136/bmjopen-2023-076962.
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IntroductionCoronary artery and heart valve calcification is a risk factor for cardiovascular death in haemodialysis patients, so calcification prevention should be started as early as possible. Treatment with concomitant calcimimetics and low-dose vitamin D receptor activators (VDRAs) is available, but not enough evidence has been obtained on the efficacy of this regimen, particularly in patients with short dialysis duration. Therefore, this study will evaluate the efficacy and safety of early intervention with upacicalcet, a calcimimetic used to prevent coronary artery calcification in this patient population.Methods and analysisThis multicentre, open-label, randomised, parallel-group controlled study will compare an early intervention group, which received upacicalcet and a low-dose VDRA, with a conventional therapy group, which received a VDRA. The primary endpoint is a change in log coronary artery calcium volume score from baseline to 52 weeks. The main inclusion criteria are as follows: (1) age 18 years or older; (2) dialysis is planned or dialysis duration is less than 60 months; (3) intact parathyroid hormone (PTH) >240 pg/mL or whole PTH level>140 pg/mL; (4) serum-corrected calcium≥8.4 mg/dL and (5) Agatston score >30. The main exclusion criteria are as follows: (1) history of parathyroid intervention or fracture in the past 12 weeks; (2) history of myocardial infarction, stroke or leg amputation in the past 12 weeks; (3) history of coronary angioplasty and (4) heart failure of New York Heart Association class III or worse.Ethics and disseminationThe study will comply with the Declaration of Helsinki and the Japanese Clinical Trials Act. The study protocol has been approved by the Fujita Health University Certified Review Board (file no. CR22-052). Written informed consent will be obtained from all participants. Study results will be presented in academic meetings and peer-reviewed academic journals.Trial registration numberjRCTs041220126.
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Tai, Sheng-Lun, Yu-Chieng Liou, Juanzhen Sun, Shao-Fan Chang, and Min-Chao Kuo. "Precipitation Forecasting Using Doppler Radar Data, a Cloud Model with Adjoint, and the Weather Research and Forecasting Model: Real Case Studies during SoWMEX in Taiwan." Weather and Forecasting 26, no. 6 (December 1, 2011): 975–92. http://dx.doi.org/10.1175/waf-d-11-00019.1.
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Abstract The quantitative precipitation forecast (QPF) capability of the Variational Doppler Radar Analysis System (VDRAS) is investigated in the Taiwan area, where the complex topography and surrounding oceans pose great challenges to accurate rainfall prediction. Two real cases observed during intensive operation periods (IOPs) 4 and 8 of the 2008 Southwest Monsoon Experiment (SoWMEX) are selected for this study. Experiments are first carried out to explore the sensitivity of the retrieved fields and model forecasts with respect to different background fields. All results after assimilation of the Doppler radar data indicate that the principal kinematic and thermodynamic features recovered by the VDRAS four-dimensional variational data assimilation (4DVAR) technique are rather reasonable. Starting from a background field generated by blending ground-based in situ measurements (radiosonde and surface mesonet station) and reanalysis data over the oceans, VDRAS is capable of capturing the evolution of the major precipitation systems after 2 h of simulation. The model QPF capability is generally comparable to or better than that obtained using only in situ observations or reanalysis data to prepare the background fields. In a second set of experiments, it is proposed to merge the VDRAS analysis field with the Weather Research and Forecasting Model (WRF), and let the latter continue with the following model integration. The results indicate that through this combination, the performance of the model QPF can be further improved. The accuracy of the predicted 2-h accumulated rainfall turns out to be significantly higher than that generated by using VDRAS or WRF alone. This can be attributed to the assimilation of meso- and convective-scale information, embedded in the radar data, into VDRAS, and to better treatment of the topographic effects by the WRF simulation. The results illustrated in this study demonstrate a feasible extension for the application of VDRAS in other regions with similar geographic conditions and observational limitations.
Dissertations / Theses on the topic "VDrama"
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Chenane, Chabane. "Analyse et reconstruction de la dynamique des véhicules motorisés (VDRM) et détection de situations limites de roulis." Thesis, Evry-Val d'Essonne, 2014. http://www.theses.fr/2014EVRY0037/document.
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Le monde des Véhicules à Deux Roues Motorisés (VDRM) a changé considérablement,en matière de qualité et de performances. Ces véhicules ont pris une place importante dans notre vie quotidienne, que ce soit pour les déplacements ou les loisirs, ce qui a contribué à l’augmentation et à la diversité du parc. Néanmoins, la sécurité des usagers est devenue une des préoccupations des institutions routières et des organismes de recherche, vu le nombre croissant des accidents et la vulnérabilité à laquelle sont confrontés. Nos travaux de recherche s’inscrivent dans la thématique d’étude (modélisation et observation) et d’analyse de la dynamique limite des VDRM. L’objectif étant la conception des outils nécessaires à l’établissement de systèmes d’aide à la conduite, de type préventif, dédiés à renforcer la sécurité du conducteur et à améliorer sa conduite. Le principal outil est un bon dispositif de simulation, vu les contraintesrencontrées pour la réalisation en pratique des tests, tel que la sécurité du pilote, le coût, etc. C’est ainsi, qu’une synthèse de trois modèles dynamiques non linéaires, àun corps, à deux corps et à cinq corps, est proposée. Une fonction de risque, relativeà l’angle de roulis du véhicule maximal, est établie. Sa variation en fonction desparamètres inertiels et géométriques de l’ensemble véhicule et conducteur, de leursdynamiques et de l’infrastructure, a fait l’objet d’une étude approfondie. La difficultéd’implémentation de nombreux capteurs, nous a conduit à concevoir des méthodesd’observation des dynamiques importantes pour la mise en pratique des systèmesde sécurité. Pour ce faire, nous avons reconstruit les grandeurs, contribuant à la dynamique latérale, par l’application de l’observateur Proportionnel Double Intégral(P2I) sur deux cas de modèles (3DDL et 4 DDL). La dernière partie du mémoire, est consacrée aux travaux réalisés sur l’instrumentation du prototype Scooter dont dispose le laboratoire. L’analyse des données enregistrées sur piste et la validation des techniques d’observation développées y sont détailléesThe world of Powered Two Wheeled (PTW) vehicles has changed considerably in quality and performance. These vehicles have taken an important place in our live, whether for transportation or leisure, which contributed to the increasing and diversity of their park. However, the safety of users has become a concern of road institutions and research organizations, given the increasing number of accidents and vulnerability at which they are faced. Our research fall within the thematic study of modeling, observation and dynamic limit analysis of the PTW vehicles. The main objective is to design tools needed to establish safety systems, of preventive kind, dedicated to enhance driver safety and improve his conduct. The main tool is a good device simulation, given the constraints encountered in the practical realization of tests, such as driver safety, cost, etc. For this, a synthesis of three non-linear dynamic models of one body, two bodies and five bodies, is proposed. A risk function relative to the maximum roll angle of the vehicle is established. Its variation according to the inertial and geometric parameters of the whole vehicle and driver, their dynamics and infrastructure, has been subject of extensive study. The difficulty of implementing many sensors has led us to develop methods to reconstruct the important dynamics for the implementation of safety systems. To do this, we reconstructed quantities contributing to the lateral dynamics by applying the Proportional Two Integral (P2I) observer. The last part of the manuscript is devoted to the work carried out about the instrumentationof the Scooter prototype, available at our laboratory. The analysis of the recorded data on the test track and the validation of the observers developed are detailed
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Yang, Ching-yu, and 楊靜伃. "Improving short-term QPF by using a 4DVAR radar data assimilation system (VDRAS) and WRF." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/06282880686618820363.
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碩士國立中央大學
大氣物理研究所
100
The NCAR Variational Doppler Radar Analysis System (VDRAS) is a system which uses the 4DVAR technique to assimilate the radar reflectivity and radial wind observations, and is capable of providing the three-dimensional kinematic and thermodynamic fields within a weather system. Since VDRAS is formulated on a Cartesian coordinate, its application to Taiwan where the topography is complicated is expected to be limited. Previous studies in which the analysis fields from VDRAS were merged with WRF showed encouraging results in improving the model Quantitative Precipitation Forecast (QPF). The purpose of this study is to test the sensitivity of the cycling configuration for VDRAS, and find a robust way of combining VDRAS and WRF. A real case of Mei-Yu front occurred on 14 June 2008 during Southwest Monsoon Experiment (SoWMEX) IOP8 is selected. In the first set of experiment, three tests are designed to examine the sensitivity of the analysis and forecast with respect to VDRAS cycling configuration containing 1-3 cycles in assimilation processes, respectively. The results of the principal kinematic and thermodynamic features reveal that VDRAS with two cycles is better than the other designs. In the second set of experiment, the VDRAS analysis fields are merged with WRF model. Assuming that the synoptic scale influence can be neglected within a period of three to four hours, it is found that using a single domain instead of nested domains can effectively remove the noises generated along the domain boundaries. Two different ways are used to merge VDRAS with WRF, and they are “direct replacement” and “WRF 3DVAR”, respectively. It is found that when the VDRAS analysis fields generated by 1-3 cycles are directly merged with WRF model, the two-cycle VDRAS analysis field produces the best results. The impact of using VDRAS outputs to improve the QPF can last for about four hours. The accuracy of the predicted 4-hour accumulated rainfall after merging VDRAS and WRF turns out to be significantly higher than that generated by using VDRAS or WRF alone. This can be attributed to the assimilation of meso- and convective scale information, embedded in the radar data into the VDRAS, and to a better treatment of the topographic effects by the WRF model simulation. However, the experiments of using “WRF 3DVAR” to merge VDRAS analysis fields with WRF are not successful, and this method needs a longer time to spin up. This research suggests an effective way of using VDRAS to forecast rainfall under Taiwan’s mountainous situation.
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Kuo, Min-Chao, and 郭閔超. "Improving short-range QPF in Taiwan by VDRAS and WRF using data from multiple weather radars." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/30100864927063636693.
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碩士國立中央大學
大氣物理研究所
99
In this research, the Variational Doppler Radar Analysis System (VDRAS) is used to assimilate radar data. The VDRAS has the capability to conduct forecast, but only over flat surface. Thus, it is attempted to merge the VDRAS analysis field with WRF, so that one can use the latter to resolve the terrain. In this study, we will use RCCG, RCKT, RCHL and S-POL radars to perform a series of assimilation experiments with different strategies. A real case of a shallow surface front occurred from 0500UTC to 0900UTC on 02 June 2008 during Southwest Monsoon Experiment IOP4 is selected. Experimental results reveal that assimilating more radar data leads to a better performance of the rainfall forecast. It is also shown that assimilating radar data is better than using WRF alone. Further improvements can be achieved when WRF is merged with VDRAS analysis field twice. By assimilating radar data on 0500~0600UTC, when convective system is still over the ocean, results in a more accurate forecast of the rainfall than performing the radar data assimilation on 0700~0800UTC, when convective system already reaches the complex terrain. This difference can be explained in the following. Since a large portion of the convection system is over the terrain on 0700UTC~0800UTC, therefore even with radar data assimilation, the VDRAS is not able to capture the major features of the convective structure due to its inability to resolve the complex terrain. The above-mentioned experimental results can be used as a guideline for applying VDRAS in Taiwan or other places with similar geographic environment and observational limitations.
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Chang, Shao-Fan, and 張少凡. "The influence of assimilation strategies and ice-phase microphysics on the application of a four-dimensional Variational Doppler Radar Analysis System (VDRAS) for quantitative precipitation forecasts." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/06292548093300322850.
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博士國立中央大學
大氣物理研究所
101
A series of observation system simulation experiments (OSSEs) and real case study are conducted to investigate the application of the Doppler radar data assimilation technique for numerical model quantitative precipitation forecasts (QPF). A four-dimensional Variational Doppler Radar Analysis System (VDRAS) is adopted for all experiments. The first set of OSSEs demonstrates that when the background field contains the imperfect information predicted from a mesoscale model, the incorrect convective-scale perturbations in the background can result in spurious scattered precipitation. However, a smoothing procedure can be utilized to remove the fine structures from the primitive model output to avoid this over-prediction. Results from a second set of OSSEs indicate that the lack of low-elevation data due to beam blockage could significantly alter the retrieved low-level thermal and dynamical structures when different number of data assimilation cycles is applied. These impacts could lower the rainfall forecast capability of the model. The third set of OSSEs shows that, when the rainwater is assimilated over a long assimilation window, the nonlinearity embedded in the microphysical process could lead the minimization algorithm to a wrong direction, causing a further degradation of the rainfall prediction. However, using multiple short assimilation cycles produces better minimization and forecast results than those obtained with a single long cycle. A real case experiment based on data collected during Intensive Operation Period (IOP) #8 of the 2008 Southwest Monsoon Experiment (SoWMEX) is conducted to provide a verification of the conclusions obtained from OSSEs under a realistic framework. The microphysics scheme of VDRAS is extended from warm rain process to cold rain process. It is found that the retrieved water content would be underestimated if all radar reflectivities are assumed to be in the form of warm rain. This underestimation can be improved when the cold rain process is implemented into VDRAS. The VDRAS with ice physics can provide better rainfall forecast.
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Tai, Sheng-Lun, and 戴聖倫. "The Development and Application of a Terrain-Resolving Scheme for the Forward Model and Its Adjoint in the Four-Dimensional Variational Doppler Radar Analysis System (VDRAS)." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/9uz4mj.
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博士國立中央大學
大氣科學學系
105
The four-dimensional Variational Doppler Radar Analysis System (VDRAS) developed at the National Center for Atmospheric Research (NCAR) is significantly improved by implementing a terrain-resolving scheme to its forward model and adjoint based on the Ghost Cell Immersed Boundary Method (GCIBM), which allows the topographic effects to be considered without the necessity to re-build the model on a terrain-following coordinate system. The new system, called IBM_VDRAS, is able to perform forward forecast and backward adjointmodel integration over non-flat lower boundaries, ranging from mountains with smooth slopes to buildings with sharp surfaces. To evaluate the performance of the forward model over complex terrain, idealized numerical experiments of a two-dimensional linear mountain wave and three-dimensional lee side vortices are first conducted, followed by a comparison with a simulation by the Weather Research and Forecasting (WRF) model. In addition, the building-scale simulation demonstrates its flexibility in resolving terrain as well. An Observation Simulation System Experiment (OSSE) is also conducted with the assimilation of simulated radar data to examine the ability of IBM_VDRAS in analyzing orographically forced moist convection. It is shown that the IBM_VDRAS can retrieve terrain-influenced three-dimensional meteorological fields including winds, thermodynamic and microphysical parameters with reasonable accuracy. This new system is utilized to study precipitation process in a real case of pre-frontal rainbands passed over southern Taiwan on June 14 of 2008, collected by IOP 8 of the 2008 Southwest Monsoon Experiment (SoWMEX). Prior to physical discussion, the multivariate analysis is verified by various types of measurements including mesonet stations, wind profiler, radiosonde and Doppler radar radial velocity. It shows that IBM_VDRAS has robust performance in retrieving the meteorological states. Further examinations on the frequent updated analyses demonstrate the importance of quasi-steady convergence line near southwestern coast of Taiwan. The major mechanisms leading to the formation and maintenance of this convergence line is decomposed into pure topographic, pure evaporation cooling, nonlinear interactive effect, and is further explored through a series of sensitivity experiments. Pure topographic effect is found to be the dominant factor in modulating the convection development. However, the contributions from nonlinear interaction and pure evaporation, although with weaker magnitudes, cannot be neglected. A schematic diagram is formulated to explain how a local circulation system is built and maintained to support the above mentioned quasi-stationary coastal convergence line, which is responsible for a long-lasting severe precipitation event. It is clear that the interaction among mountain blockage, evaporation cooling effect, and the development of an enhanced widespread high pressure zone over the southwest plain area, are the key factors to modulate the evolution of the convective system.
Books on the topic "VDrama"
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d1938-, Reynolds Henry. The chant of Jimmie Blacksmith. Strawberry Hills, N.S.W: Currency Press, 2008.
Find full textBook chapters on the topic "VDrama"
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Balsom, Erika. "Transmission, from the Movie-Drome to Vdrome." In After Uniqueness, 219–36. Columbia University Press, 2017. http://dx.doi.org/10.7312/columbia/9780231176934.003.0009.
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Chapter 8 revisits the utopian moment of exhibiting experimental film and video art on television in light of contemporary efforts to develop authorized platforms for the distribution of artists’ moving image on the Internet. This chapter turns to the life and legacy of the late-night programs Screening Room (1971–81) and Midnight Underground (1993–97), comparing and contrasting the broadcasting model with the recent narrowcasting initiative Vdrome, www.vdrome.org, which shows a single artists’ video for a limited period of time, usually ten days.
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"8. Transmission, from the Movie-Drome to Vdrome." In After Uniqueness, 219–36. Columbia University Press, 2017. http://dx.doi.org/10.7312/bals17692-010.
Full textConference papers on the topic "VDrama"
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Dai, Jie, Lei Han, Wei Zhang, ChangJiang Zhang, and Hanlei Feng. "A deep belief network approach using VDRAS data for nowcasting." In Ninth International Conference on Graphic and Image Processing, edited by Hui Yu and Junyu Dong. SPIE, 2018. http://dx.doi.org/10.1117/12.2303475.
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Roberts, Justin, James MacKrell, D. B. Piyarathna, Gary Krishnan, Cristian Coarfa, David Rowley, and Nancy L. Weigel. "Abstract 1817: A novel non-secosteroidal VDR agonist, VDRM2, inhibits prostate tumor growth." In Proceedings: AACR 107th Annual Meeting 2016; April 16-20, 2016; New Orleans, LA. American Association for Cancer Research, 2016. http://dx.doi.org/10.1158/1538-7445.am2016-1817.
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