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451 results on '"Kagan, Leonid"'

3. On disintegration of lean hydrogen flames in narrow gaps

Author

Yanez, Jorge, Kagan, Leonid, Kuznetsov, Mike, and Sivashinsky, Gregory

Subjects
Physics - Fluid Dynamics
Abstract

The disintegration of near limit flames propagating through the gap of Hele-Shaw cells has recently become a subject of active research. In this paper, the flamelets resulting from the disintegration of the continuous front are interpreted in terms of the Zeldovich flame-balls stabilized by volumetric heat losses. A complicated free-boundary problem for 2D self-drifting near circular flamelets is reduced to a 1D model. The 1D formulation is then utilized to obtain the locus of the flamelet velocity, size, heat losses and Lewis numbers at which the self-drifting flamelets may exist., Comment: 10 pages, 12 figures. arXiv admin note: text overlap with arXiv:2308.08537

Published
2024

4. On dynamics of gasless combustion in slowly varying periodic media: periodic fronts, their stability and propagation-extinction-diffusion-reignition pattern

Author

Matson, Amanda, Kagan, Leonid, Brauner, Claude-Michel, Sivashinsky, Gregory, and Gordon, Peter V.

Subjects
Nonlinear Sciences - Pattern Formation and Solitons, Mathematics - Analysis of PDEs
Abstract

In this paper we consider a classical model of gasless combustion in a one dimensional formulation under the assumption of ignition temperature kinetics. We study the propagation of flame fronts in this model when the initial distribution of the solid fuel is a spatially periodic function that varies on a large scale. It is shown that in certain parametric regimes the model supports periodic traveling fronts. An accurate asymptotic formula for the velocity of the flame front is derived and studied. The stability of periodic fronts is also explored, and a critical condition in terms of parameters of the problem is derived. It is also shown that the instability of periodic fronts, in a certain parametric regimes, results in a propagation-extinction-diffusion-reignition pattern which is studied numerically., Comment: 14 pages, 13 figures

Published
2024

6. Modeling of 2D self-drifting flame-balls in Hele-Shaw cells

Author

Yanez, Jorge, Kagan, Leonid, Sivashinsky, Gregory, and Kuznetsov, Mike

Subjects
Physics - Fluid Dynamics, Physics - Chemical Physics, 7610, 76V05
Abstract

The disintegration of near limit flames propagating through the gap of Hele-Shaw cells has recently become a subject of active research. In this paper, the flamelets resulting from the disintegration of the continuous front a reinterpreted in terms of the Zeldovich flame-balls stabilized by volumetric heat losses. A complicated free-boundary problem for 2D self-drifting near circular flamelets is reduced to a 1D model. The 1D formulation is then utilized to obtain the locus of the flamelet velocity, radius, heat losses and Lewis numbers at which the self-drifting flamelet exists., Comment: 19 pages, 22 figures

Published
2023

9. Modeling of thermonuclear fusion flames : transition to detonation

Author

Gordon, Peter V., Kagan, Leonid, and Sivashinsky, Gregory

Subjects
Physics - Fluid Dynamics, Astrophysics - High Energy Astrophysical Phenomena
Abstract

The paper is concerned with identification of the key mechanisms controlling deflagration-to-detonation transition in stellar medium. The issue of thermal runaway triggered by positive feedback between the advancing flame and the flame-driven precompression is discussed in the framework of a one-dimensional flame-folding model. The paper is an extension of the authors' previous study dealing with the non-stoichiometric fusion, $fuel \to products$, kinetics (Phys.Rev.E, 103(2021)) over physically more relevant, $fuel+fuel \to products$, kinetics. Despite this change the runaway effect endures. The transition occurs prior to merging of the flame with the flame-supported precursor shock, i.e. the pretransition flame does not reach the threshold of Chapman-Jouguet deflagration., Comment: 10 pages, 8 figures, 1 table

Published
2021

14. Deflagration-to-detonation transition in an unconfined space: II. Expanding hydrogen-oxygen flames

Author

Koksharov, Andrey, Kagan, Leonid, and Sivashinsky, Gregory

Subjects
Physics - Fluid Dynamics
Abstract

The problem of deflagration-to-detonation transition in an unconfined environment is revisited. With a freely expanding self-accelerating hydrogen-oxygen flame as an example, it is shown that deflagration-to-detonation transition is indeed possible provided the flame is large enough. The transition occurs prior to merging of the flame with the flame-supported precursor shock. The pre-transition flame does not reach the threshold of CJ-deflagration. Numerical simulations employed are based on the recently developed pseudo-spectral method with time and space adaptation.

Published
2019

18. Strongly nonlinear asymptotic model of cellular instabilities in premixed flames with stepwise ignition temperature kinetics

Author

Kilker, Nathan, Golovaty, Dmitry, Gordon, Peter V., Kagan, Leonid, and Sivashinsky, Gregory I.

Subjects
Nonlinear Sciences - Chaotic Dynamics
Abstract

In this paper we consider ignition-temperature, first-order reaction model of thermo-diffusive combustion that describes dynamics of thick flames arising in a theory of combustion of hydrogen-oxygen and ethylene-oxygen mixtures. These flames often assume the shape of propagating curved interfaces that correspond to level sets of constant temperature. We derive a fully nonlinear equation that governs dynamics of these level sets under a single assumption of small curvature. We study this equation for various asymptotic parameter regimes and discuss the ranges of validity of the corresponding simplified models. Our theoretical findings are supported by numerical simulations.

Published
2016

21. Development of a Population Pharmacokinetic Gabapentin Model Leveraging Therapeutic Drug Monitoring Concentrations.

Author

Al-Zubaydi, Firas, Wassef, Andrew, Kagan, Leonid, and Brunetti, Luigi

Subjects
DRUG monitoring, TYPE 2 diabetes diagnosis, PARAMETER estimation, BODY mass index, GABA
Abstract

Background/Objectives: Gabapentin has variable pharmacokinetics (PK), which contributes to difficulty in dosing and increased risk of adverse events. The objective of this study was to leverage gabapentin concentrations from therapeutic drug monitoring (TDM) to develop a population PK (popPK) model and characterize significant covariates that impact gabapentin PK. Methods: Data were retrospectively collected from 82 hospitalized adult patients with TDM gabapentin concentrations. Renal function indicators (i.e., estimated glomerular filtration rate, creatinine clearance, acute kidney injury), body weight parameters (i.e., actual body weight, ideal body weight, adjusted body weight, lean body weight, body mass index, obesity status), fasting plasma glucose levels, and diagnosis of type 2 diabetes were tested as potential covariates. A popPK model was developed in MONOLIX (2020R1, Lixoft, France). Results: A one-compartment model best described gabapentin PK with first-order absorption, dose-dependent bioavailability, first-order elimination, and no lag time. Population parameter estimates for the volume of distribution (Vd), and clearance (Cl) were 44.61 L, and 5.73 L/h, respectively. Serum creatinine was a significant covariate on Cl. Conclusions: The popPK model highlights the importance of renal function in the interindividual variability of gabapentin PK and suggests that diabetes and body weight parameters have no impact on gabapentin PK. Moreover, our study supports the utility of leveraging data obtained from clinical TDM for popPK model development. [ABSTRACT FROM AUTHOR]

Published
2024
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22. Epidural methadone and morphine pharmacokinetics and clinical effects in healthy volunteers: A randomized, crossover‐design trial.

Author

Hincker, Alexander, Reschke, Matthew, Ginosar, Yehuda, Kagan, Leonid, Kharasch, Evan D., Siemiątkowska, Anna, Park, Celine, Bakos, Kristopher, Ben‐Abdallah, Arbi, and Haroutounian, Simon

Subjects
PAIN threshold, LUMBAR pain, POSTOPERATIVE pain, METHADONE hydrochloride, MORPHINE
Abstract

Aims: Epidural opioids can provide effective analgesia for acute postoperative pain. Due to its unique physicochemical properties and long systemic elimination half‐life, epidural methadone may provide lasting analgesia with minimal adverse effects; however, human studies are lacking. The aim of the study was to test the hypothesis that epidural methadone would exhibit greater segmental analgesia (analgesia at the dermatome of injection vs. distant dermatomes) than epidural morphine. Methods: In a prospective, randomized, double‐blinded, crossover study, thirteen healthy volunteers received a 4‐mg epidural bolus of methadone or morphine at L3–L4 and underwent repeated assessment of dermatomal heat pain tolerance and pressure pain threshold at lumbar (L3) and trigeminal (V2) dermatomes, pupil diameter, respiratory parameters and venous opioid concentration for 24 h. The primary outcome was selective (lumbar vs. trigeminal) segmental analgesia for heat pain, as a marker of a spinal analgesic mechanism. Results: The degree of segmental analgesia to heat pain tolerance was not different between morphine and methadone (P =.09), although morphine (P =.0009) but not methadone (P =.81) produced significant analgesia to heat pain at the lumbar vs. trigeminal dermatome over 0–12 h. Morphine overall provided longer lasting analgesia to heat pain vs. methadone (24 vs. 2 h, respectively). Morphine elicited greater systemic effects, including miosis (P =.009) and opioid‐related adverse effects (P =.002). Conclusions: These results suggest that, with equal epidural doses, both methadone and morphine produced analgesia and methadone did not produce greater segmental effects than morphine. Epidural methadone provided a more favourable adverse effect profile. [ABSTRACT FROM AUTHOR]

Published
2024
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25. Effects of intestine-specific deletion of FGF15 on the development of fatty liver disease with vertical sleeve gastrectomy

Author

Chow, Monica D., primary, Otersen, Katherine, additional, Wassef, Andrew, additional, Kong, Bo, additional, Yamarthy, Sowmya, additional, Rizzolo, Daniel, additional, Yang, Ill, additional, Buckley, Brian, additional, Lu, Alexander, additional, Crook, Naomi, additional, Lee, Matthew, additional, Gao, Judy, additional, Naganand, Sareena, additional, Stofan, Mary F., additional, Armstrong, Laura, additional, Schumacher, Justin, additional, Taylor, Rulaiha, additional, Henry, Zakiyah, additional, Basaly, Veronia, additional, Yang, Zhenning, additional, Zhang, Min, additional, Huang, Mingxing, additional, Kagan, Leonid, additional, Brunetti, Luigi, additional, Sadek, Ragui, additional, Lee, Yi-Horng, additional, and Guo, Grace L., additional

Published
2024
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35. Lipophilic activated ester prodrug approach for drug delivery to the intestinal lymphatic system

Author

Lee, Jong Bong, Zgair, Atheer, Malec, Jed, Kim, Tae Hwan, Kim, Min Gi, Ali, Joseph, Qin, Chaolong, Feng, Wanshan, Chiang, Manting, Gao, Xizhe, Voronin, Gregory, Garces, Aimie E., Lau, Chun Long, Chan, Ting-Hoi, Hume, Amy, McIntosh, Tecashanell M., Soukarieh, Fadi, Al-Hayali, Mohammed, Cipolla, Elena, Collins, Hilary M., Heery, David M., Shin, Beom Soo, Yoo, Sun Dong, Kagan, Leonid, Stocks, Michael J., Bradshaw, Tracey D., Fischer, Peter M., and Gershkovich, Pavel

Published
2018
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38. Challenging the Norm: A Multidisciplinary Perspective on Intravenous to Subcutaneous Bridging Strategies for Biologics

Author

Ait‐Oudhia, Sihem, primary, Wang, Yow‐Ming, additional, Dosne, Anne‐Gaelle, additional, Roy, Amit, additional, Jin, Jin Y., additional, Shen, Jun, additional, Kagan, Leonid, additional, Musuamba, Flora T., additional, Zhang, Lucia, additional, Kijima, Shinichi, additional, Gastonguay, Marc R, additional, and Ouellet, Daniele, additional

Published
2023
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40. Simplified urine-based method to detect rifampin underexposure in adults with tuberculosis: a prospective diagnostic accuracy study

Author

Xie, Yingda L., primary, Modi, Nisha, additional, Handler, Deborah, additional, Yu, Sijia, additional, Rao, Prakruti, additional, Kagan, Leonid, additional, Petros de Guex, Kristen, additional, Reiss, Robert, additional, Siemiątkowska, Anna, additional, Narang, Anshika, additional, Narayanan, Navaneeth, additional, Hearn, Jasie, additional, Khalil, Amanda, additional, Woods, Patricia, additional, Young, Laura, additional, Lardizabal, Alfred, additional, Subbian, Selvakumar, additional, Peloquin, Charles A., additional, Vinnard, Christopher, additional, Thomas, Tania A., additional, and Heysell, Scott K., additional

Published
2023
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46. The Sequence of the Human Genome

Author

Venter, J. Craig, Adams, Mark D., Myers, Eugene W., Li, Peter W., Mural, Richard J., Sutton, Granger G., Smith, Hamilton O., Yandell, Mark, Evans, Cheryl A., Holt, Robert A., Gocayne, Jeannine D., Amanatides, Peter, Ballew, Richard M., Huson, Daniel H., Wortman, Jennifer Russo, Zhang, Qing, Kodira, Chinnappa D., Zheng, Xiangqun H., Chen, Lin, Skupski, Marian, Subramanian, Gangadharan, Thomas, Paul D., Zhang, Jinghui, Nelson, Catherine, Broder, Samuel, Clark, Andrew G., Nadeau, Joe, McKusick, Victor A., Zinder, Norton, Levine, Arnold J., Roberts, Richard J., Simon, Mel, Slayman, Carolyn, Hunkapiller, Michael, Bolanos, Randall, Delcher, Arthur, Dew, Ian, Fasulo, Daniel, Flanigan, Michael, Florea, Liliana, Halpern, Aaron, Hannenhalli, Sridhar, Kravitz, Saul, Levy, Samuel, Mobarry, Clark, Reinert, Knut, Remington, Karin, Abu-Threideh, Jane, Beasley, Ellen, Biddick, Kendra, Bonazzi, Vivien, Brandon, Rhonda, Cargill, Michele, Chandramouliswaran, Ishwar, Charlab, Rosane, Chaturvedi, Kabir, Deng, Zuoming, Di Francesco, Valentina, Dunn, Patrick, Eilbeck, Karen, Evangelista, Carlos, Gabrielian, Andrei E., Gan, Weiniu, Ge, Wangmao, Gong, Fangcheng, Gu, Zhiping, Guan, Ping, Heiman, Thomas J., Higgins, Maureen E., Ji, Rui-Ru, Ke, Zhaoxi, Ketchum, Karen A., Lai, Zhongwu, Lei, Yiding, Li, Zhenya, Li, Jiayin, Liang, Yong, Lin, Xiaoying, Lu, Fu, Merkulov, Gennady V., Milshina, Natalia, Moore, Helen M., Naik, Ashwinikumar K, Narayan, Vaibhav A., Neelam, Beena, Nusskern, Deborah, Rusch, Douglas B., Salzberg, Steven, Shao, Wei, Shue, Bixiong, Sun, Jingtao, Wang, Zhen Yuan, Wang, Aihui, Wang, Xin, Wang, Jian, Wei, Ming-Hui, Wides, Ron, Xiao, Chunlin, Yan, Chunhua, Yao, Alison, Ye, Jane, Zhan, Ming, Zhang, Weiqing, Zhang, Hongyu, Zhao, Qi, Zheng, Liansheng, Zhong, Fei, Zhong, Wenyan, Zhu, Shiaoping C., Zhao, Shaying, Gilbert, Dennis, Baumhueter, Suzanna, Spier, Gene, Carter, Christine, Cravchik, Anibal, Woodage, Trevor, Ali, Feroze, An, Huijin, Awe, Aderonke, Baldwin, Danita, Baden, Holly, Barnstead, Mary, Barrow, Ian, Beeson, Karen, Busam, Dana, Carver, Amy, Cheng, Ming Lai, Curry, Liz, Danaher, Steve, Davenport, Lionel, Desilets, Raymond, Dietz, Susanne, Dodson, Kristina, Doup, Lisa, Ferriera, Steven, Garg, Neha, Gluecksmann, Andres, Hart, Brit, Haynes, Jason, Haynes, Charles, Heiner, Cheryl, Hladun, Suzanne, Hostin, Damon, Houck, Jarrett, Howland, Timothy, Ibegwam, Chinyere, Johnson, Jeffery, Kalush, Francis, Kline, Lesley, Koduru, Shashi, Love, Amy, Mann, Felecia, May, David, McCawley, Steven, Mclntosh, Tina, McMullen, Ivy, Moy, Mee, Moy, Linda, Murphy, Brian, Nelson, Keith, Pfannkoch, Cynthia, Pratts, Eric, Puri, Vinita, Qureshi, Hina, Reardon, Matthew, Rodriguez, Robert, Rogers, Yu-Hui, Romblad, Deanna, Ruhfel, Bob, Scott, Richard, Sitter, Cynthia, Smallwood, Michelle, Stewart, Erin, Strong, Renee, Suh, Ellen, Thomas, Reginald, Tint, Tse, Sukyee, Vech, Claire, Wang, Gary, Wetter, Jeremy, Williams, Sherita, Williams, Monica, Windsor, Sandra, Winn-Deen, Emily, Wolfe, Keriellen, Zaveri, Jayshree, Zaveri, Karena, Abril, Josep F., Guigó, Roderic, Campbell, Michael J., Sjolander, Kimmen V., Karlak, Brian, Kejariwal, Anish, Mi, Huaiyu, Lazareva, Betty, Hatton, Thomas, Narechania, Apurva, Diemer, Karen, Muruganujan, Anushya, Guo, Nan, Sato, Shinji, Bafna, Vineet, Istrail, Sorin, Lippert, Ross, Schwartz, Russell, Walenz, Brian, Yooseph, Shibu, Allen, David, Basu, Anand, Baxendale, James, Blick, Louis, Caminha, Marcelo, Carnes-Stine, John, Caulk, Parris, Chiang, Yen-Hui, Coyne, My, Dahlke, Carl, Mays, Anne Deslattes, Dombroski, Maria, Donnelly, Michael, Ely, Dale, Esparham, Shiva, Fosler, Carl, Gire, Harold, Glanowski, Stephen, Glasser, Kenneth, Glodek, Anna, Gorokhov, Mark, Graham, Ken, Gropman, Barry, Harris, Michael, Heil, Jeremy, Henderson, Scott, Hoover, Jeffrey, Jennings, Donald, Jordan, Catherine, Jordan, James, Kasha, John, Kagan, Leonid, Kraft, Cheryl, Levitsky, Alexander, Lewis, Mark, Liu, Xiangjun, Lopez, John, Ma, Daniel, Majoros, William, McDaniel, Joe, Murphy, Sean, Newman, Matthew, Nguyen, Trung, Nguyen, Ngoc, Nodell, Marc, Pan, Sue, Peck, Jim, Peterson, Marshall, Rowe, William, Sanders, Robert, Scott, John, Simpson, Michael, Smith, Thomas, Sprague, Arlan, Stockwell, Timothy, Turner, Russell, Venter, Eli, Wang, Mei, Wen, Meiyuan, Wu, David, Wu, Mitchell, Xia, Ashley, Zandieh, Ali, and Zhu, Xiaohong

Published
2001

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