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Selvakumar D, Sonu KP, Ramadoss G, Sivaramakrishnan R, Jayavel R, Eswaramoorthy M, Venkateswara Rao K, Pugazhendhi A. Heterostructures of polyaniline and Ce-ZnO nanomaterial coated flexible PET thin films for LPG gas sensing at standard environment. Chemosphere 2023; 314:137492. [PMID: 36481170 DOI: 10.1016/j.chemosphere.2022.137492] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 11/20/2022] [Accepted: 12/04/2022] [Indexed: 06/17/2023]
Abstract
The n-type Ce doped ZnO (Ce-ZnO) and p-type polyaniline (PANI) heterojunction were successfully synthesized via simple chemical solution method for sensing liquefied petroleum gas (LPG) at standard environment. The morphology and structures of as-prepared Ce-ZnO & PANI nanoparticles were analyzed by numerous kinds of techniques. Ce-ZnO & PANI nanoparticles were mixed with n-methylpyrrolidone (NMP) which is coated over the gold coated PET electrode by doctor blade method and dried overnight at 60 °C to form p-n junction. The as-formed p-n junction is to be driven with the help of 1.5 V potential at ambient temperature. X-ray photoelectron spectroscopy results of Ce-ZnO nanoparticles confirmed the existence of Ce4+ and the improved amount of both chemisorbed oxygen and oxygen vacancy after the formation of Ce-ZnO heterojunction. The maximum response of 80% was realized for hollow Ce-ZnO/PANI sensor at 100 ppm. The proposed material is a novel candidate to detect the LPG even at low (30) ppm and this study reveals the possibility of developing a potentially inexpensive hollow Ce-ZnO/PANI sensor for sensing LPG efficiently.
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Affiliation(s)
- D Selvakumar
- Department of ECE, KPR Institute of Engineering and Technology, Coimbatore, 641407, India; Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, 560064, India.
| | - K P Sonu
- Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, 560064, India
| | - G Ramadoss
- School of Chemical and Biotechnology, SASTRA Deemed University, Thanjavur, 613401, India
| | - R Sivaramakrishnan
- Laboratory of Cyanobacterial Biotechnology, Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
| | - R Jayavel
- Centre for Nanoscience and Technology, Anna University, Chennai, 600 025, India
| | - M Eswaramoorthy
- Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, 560064, India
| | - K Venkateswara Rao
- Centre for Nano Science and Technology, JNT University Hyderabad, Kukatpally, 500085, Telangana, India
| | - A Pugazhendhi
- School of Engineering, Lebanese American University, Byblos, Lebanon; University Centre for Research & Development, Department of Civil Engineering, Chandigarh University, Mohali, India.
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Sivaramakrishnan R, Nandhini A, Jaipreethi P, Kapilan K, Uthra S, Kanchana S, Yuvaraj D, Arumugam M. Tyrosinase from Sepiella inermis (Van Hasselt [Ferussac & d’Orbigny], 1835) and its Phenol Removal Activity. NEPT 2021. [DOI: 10.46488/nept.2021.v20i02.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Rajendra Thilahar C, Sivaramakrishnan R. A fuzzy rule based effective feature selection approach for augmented reality. IFS 2020. [DOI: 10.3233/jifs-191674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Thamizhvani TR, Lakshmanan S, Sivaramakrishnan R. Mobile application-based computer-aided diagnosis of skin tumours from dermal images. The Imaging Science Journal 2018. [DOI: 10.1080/13682199.2018.1492682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- T. R. Thamizhvani
- Department of Biomedical Engineering, Vels University, Chennai, India
| | - Suganthi Lakshmanan
- Department of Biomedical Engineering, SSN College of Engineering, Chennai, India
| | - R. Sivaramakrishnan
- Department of Biomedical Engineering, SSN College of Engineering, Chennai, India
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Sivaramakrishnan R, Gupta S, Agarwal SK, Bhowmik D, Mahajan S. Comparison of outcomes between surgically placed and percutaneously placed peritoneal dialysis catheters: A retrospective study. Indian J Nephrol 2016; 26:268-74. [PMID: 27512299 PMCID: PMC4964687 DOI: 10.4103/0971-4065.163425] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
There is lack of adequate data on comparison of outcomes between percutaneously placed peritoneal dialysis (PD) catheters inserted by nephrologists and PD catheters placed by surgeons. The aim of this study is to retrospectively analyze the outcomes of PD catheters inserted by surgeons (by open surgical or laparoscopic technique) and compare them with those inserted by nephrologists among ESRD patients who underwent elective PD catheter insertions between January 2009 and December 2012. The primary outcome measure was the proportion of catheters removed because of primary nonfunction. The secondary outcome measures were catheter survival, patient survival, and incidence of complications of catheter insertion. A total of 143 PD catheter insertions (88 by surgeons and 55 by nephrologists) performed in 132 patients were considered for the analysis. The primary nonfunction rate of PD catheter insertions in both groups was comparable (18.2% and 7.3%, P = 0.08). Break-in period was shorter in Group N (p = <0.001). No differences were noted in patient or catheter survival. Percutaneously placed PD catheters performed by nephrologists have comparable outcomes with surgically placed PD catheters among selected cases and have the advantage of lower costs, avoidance of operation theater scheduling issues, smaller incision length, and shorter break-in period. Therefore, more nephrologists should acquire the expertise on percutaneous PD catheter placement as it leads to lesser waiting times and better utilization of PD.
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Affiliation(s)
- R Sivaramakrishnan
- Department of Nephrology, All India Institute of Medical Sciences, New Delhi, India
| | - S Gupta
- Department of Nephrology, All India Institute of Medical Sciences, New Delhi, India
| | - S K Agarwal
- Department of Nephrology, All India Institute of Medical Sciences, New Delhi, India
| | - D Bhowmik
- Department of Nephrology, All India Institute of Medical Sciences, New Delhi, India
| | - S Mahajan
- Department of Nephrology, All India Institute of Medical Sciences, New Delhi, India
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Mathur RP, Nayak S, Sivaramakrishnan R, Jain V. Role of Alpha Blockers in Hypertension with Benign Prostatic Hyperplasia. J Assoc Physicians India 2014; 62:40-44. [PMID: 26245042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Hypertension and benign prostatic hyperplasia (BPH) are common disorders of aging men. As the world population is aging these two diseases are becoming a significant public health problem worldwide. Approximately 30% of men treated for BPH have coexisting hypertension. The α-Adrenergic Blockers: Prazosin, Terazosin and Doxazosin are established agents in the therapy of hypertension, and are also effective drugs in the treatment of BPH. It is reasonable to use α-Adrenergic Blockers as the treatment of choice for men with hypertension and BPH.
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Peukert SL, Labbe NJ, Sivaramakrishnan R, Michael JV. Direct measurements of rate constants for the reactions of CH3 radicals with C2H6, C2H4, and C2H2 at high temperatures. J Phys Chem A 2013; 117:10228-38. [PMID: 23968575 DOI: 10.1021/jp4073153] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The shock tube technique has been used to study the reactions CH3 + C2H6 → C2H4 + CH4 + H (1), CH3 + C2H4 → Products + H (2), and CH3 + C2H2 → Products + H (3). Biacetyl, (CH3CO)2, was used as a clean high temperature thermal source for CH3-radicals for all the three reactions studied in this work. For reaction 1, the experiments span a T-range of 1153 K ≤ T ≤ 1297 K, at P ~ 0.4 bar. The experiments on reaction 2 cover a T-range of 1176 K ≤ T ≤ 1366 K, at P ~ 1.0 bar, and those on reaction 3 a T-range of 1127 K ≤ T ≤ 1346 K, at P ~ 1.0 bar. Reflected shock tube experiments performed on reactions 1-3, monitored the formation of H-atoms with H-atom Atomic Resonance Absorption Spectrometric (ARAS). Fits to the H-atom temporal profiles using an assembled kinetics model were used to make determinations for k1, k2, and k3. In the case of C2H6, the measurements of [H]-atoms were used to derive direct high-temperature rate constants, k1, that can be represented by the Arrhenius equation k1(T) = 5.41 × 10(-12) exp(-6043 K/T) cm(3) molecules(-1) s(-1) (1153 K ≤ T ≤ 1297 K) for the only bimolecular process that occurs, H-atom abstraction. TST calculations based on ab initio properties calculated at the CCSD(T)/CBS//M06-2X/cc-pVTZ level of theory show excellent agreement, within ±20%, of the measured rate constants. For the reaction of CH3 with C2H4, the present rate constant results, k2', refer to the sum of rate constants, k(2b) + k(2c), from two competing processes, addition-elimination, and the direct abstraction CH3 + C2H4 → C3H6 + H (2b) and CH3 + C2H4 → C2H2 + H + CH4 (2c). Experimental rate constants for k2' can be represented by the Arrhenius equation k2'(T) = 2.18 × 10(-10) exp(-11830 K/T) cm(3) molecules(-1) s(-1) (1176 K ≤ T ≤ 1366 K). The present results are in excellent agreement with recent theoretical predictions. The present study provides the only direct measurement for the high-temperature rate constants for these channels. Lastly, measurements of H-atoms from the reaction of CH3 with C2H2 provided direct unambiguous determinations of the rate constant for the dominant process under the present experimental conditions, the addition-elimination, CH3 + C2H2 → p-C3H4 + H (3b). Experimental rate constants for k(3b) can be represented by the Arrhenius equation k(3b)(T) = 5.16 × 10(-13) exp(-3852 K/T) cm(3) molecules(-1) s(-1) (1127 K ≤ T ≤ 1346 K). The present determinations for k(3b) represent the only direct measurements for this reaction and are also in good agreement with recent theoretical predictions. The present experimental k(3b) values were also used to derive rate constants, k(-3b), for the more extensively studied back-process, the reaction of H-atoms with propyne. The best fit Arrhenius equation, combining the presently derived k(-3b) values with a recent experimental determination for k(-3b), can be represented by k(-3b)(T) = 3.87 × 10(-11) exp(-1313 K/T) cm(3) molecules(-1) s(-1) (870 K ≤ T ≤ 1346 K). The present studies represent a novel implementation of the sensitive H-ARAS technique to measure rate constants for poorly characterized and difficult to isolate "slow" CH3-radical reactions with stable C2 hydrocarbons.
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Affiliation(s)
- S L Peukert
- Chemical Sciences and Engineering Division, Argonne National Laboratory , Argonne, Illinois 60439, United States
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Peukert SL, Sivaramakrishnan R, Michael JV. High Temperature Shock Tube Studies on the Thermal Decomposition of O3 and the Reaction of Dimethyl Carbonate with O-Atoms. J Phys Chem A 2013; 117:3729-38. [DOI: 10.1021/jp400613p] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- S. L. Peukert
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439,
United States
| | - R. Sivaramakrishnan
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439,
United States
| | - J. V. Michael
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439,
United States
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Peukert SL, Sivaramakrishnan R, Michael JV. High Temperature Shock Tube and Theoretical Studies on the Thermal Decomposition of Dimethyl Carbonate and Its Bimolecular Reactions with H and D-Atoms. J Phys Chem A 2013; 117:3718-28. [DOI: 10.1021/jp312643k] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- S. L. Peukert
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439,
United States
| | - R. Sivaramakrishnan
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439,
United States
| | - J. V. Michael
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439,
United States
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Sivaramakrishnan R, Michael JV, Harding LB, Klippenstein SJ. Shock tube explorations of roaming radical mechanisms: the decompositions of isobutane and neopentane. J Phys Chem A 2012; 116:5981-9. [PMID: 22394380 DOI: 10.1021/jp210959j] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The thermal decompositions of isobutane and neopentane have been studied using both shock tube experiments and ab initio transition state theory based master equation calculations. Dissociation rate constants for these molecules have been measured at high temperatures (1260-1566 K) behind reflected shock waves using high-sensitivity H-ARAS detection. The two major dissociation channels at high temperature are iso-C(4)H(10) → CH(3) + i-C(3)H(7) (1a) and neo-C(5)H(12) → CH(3) + t-C(4)H(9) (2a). Ultrahigh-sensitivity ARAS detection of H-atoms produced from the rapid decomposition of the product radicals, i-C(3)H(7) in (1a) and t-C(4)H(9) in (2a), through i-C(3)H(7) + M → H + C(3)H(6) + M (3a) and t-C(4)H(9) + M → H + i-C(4)H(8) + M (4a) allowed measurements of both the total decomposition rate constants, k(total), and the branching to radical products, which were observed to be equivalent in both systems, k(1a)/k(total) and k(2a)/k(total) = 0.79 ± 0.05. Theoretical analyses indicate that in isobutane, the non-H-atom fraction has two contributions, the dominant fraction being due to the roaming radical mechanism leading to molecular products through iso-C(4)H(10) → CH(4) + C(3)H(6) (1b) with k(1b)/k(total) = 0.16, and a minor fraction that involves the isomerization of i-C(3)H(7) to n-C(3)H(7) that then subsequently forms methyl radicals, i-C(3)H(7) + M → n-C(3)H(7) + M → CH(3) + C(2)H(4) + M (3b). In contrast to isobutane, in neopentane, the contribution to the non-H-atom fraction is exclusively through the roaming radical mechanism that leads to neo-C(5)H(12) → CH(4) + i-C(4)H(8) (2b) with k(2b)/k(total) = 0.21. These quantitative measurements of larger contributions from the roaming mechanism for larger molecules are in agreement with the qualitative theoretical arguments that suggest long-range dispersion interactions (which become increasingly important for larger molecules) may enhance roaming.
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Affiliation(s)
- R Sivaramakrishnan
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
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11
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12
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Sivaramakrishnan R, Su MC, Michael JV, Klippenstein SJ, Harding LB, Ruscic B. Shock Tube and Theoretical Studies on the Thermal Decomposition of Propane: Evidence for a Roaming Radical Channel. J Phys Chem A 2011; 115:3366-79. [DOI: 10.1021/jp2006205] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- R. Sivaramakrishnan
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - M.-C. Su
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - J. V. Michael
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - S. J. Klippenstein
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - L. B. Harding
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - B. Ruscic
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
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Sivaramakrishnan R, Kaul B, Jain SB, Mandonca S, Gupta S. Multiple sclerosis in a patient with membranous glomerulopathy: is vitamin D deficiency the culprit in the presence of HLA DRB1*1501 allele? Mult Scler 2011; 17:254. [DOI: 10.1177/1352458510383149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- R Sivaramakrishnan
- Department of Nephrology, All India Institute of Medical Sciences, Delhi, India
| | - Bhavna Kaul
- Department of Neurology, All India Institute of Medical Sciences, Delhi, India
| | - Sheel Badhra Jain
- Department of Nephrology, All India Institute of Medical Sciences, Delhi, India
| | - Sathish Mandonca
- Department of Nephrology, All India Institute of Medical Sciences, Delhi, India
| | - Sanjay Gupta
- Department of Nephrology, All India Institute of Medical Sciences, Delhi, India
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Arockia Selvakumar A, Sathish Pandian R, Sivaramakrishnan R, Kalaichelvan K. Simulation and performance study of 3 — DOF parallel manipulator units. INTERACT-2010 2010. [DOI: 10.1109/interact.2010.5706219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
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Sivaramakrishnan R, Su MC, Michael JV, Klippenstein SJ, Harding LB, Ruscic B. Rate Constants for the Thermal Decomposition of Ethanol and Its Bimolecular Reactions with OH and D: Reflected Shock Tube and Theoretical Studies. J Phys Chem A 2010; 114:9425-39. [DOI: 10.1021/jp104759d] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- R. Sivaramakrishnan
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - M.-C. Su
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - J. V. Michael
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - S. J. Klippenstein
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - L. B. Harding
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - B. Ruscic
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
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Sivaramakrishnan R, Michael JV, Klippenstein SJ. Direct Observation of Roaming Radicals in the Thermal Decomposition of Acetaldehyde. J Phys Chem A 2009; 114:755-64. [DOI: 10.1021/jp906918z] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- R. Sivaramakrishnan
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - J. V. Michael
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - S. J. Klippenstein
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
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Klippenstein SJ, Harding LB, Ruscic B, Sivaramakrishnan R, Srinivasan NK, Su MC, Michael JV. Thermal Decomposition of NH2OH and Subsequent Reactions: Ab Initio Transition State Theory and Reflected Shock Tube Experiments. J Phys Chem A 2009; 113:10241-59. [PMID: 19722533 DOI: 10.1021/jp905454k] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- S. J. Klippenstein
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - L. B. Harding
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - B. Ruscic
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - R. Sivaramakrishnan
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - N. K. Srinivasan
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - M.-C. Su
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - J. V. Michael
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
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Sivaramakrishnan R, Michael JV. Rate Constants for OH with Selected Large Alkanes: Shock-Tube Measurements and an Improved Group Scheme. J Phys Chem A 2009; 113:5047-60. [DOI: 10.1021/jp810987u] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- R. Sivaramakrishnan
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
| | - J. V. Michael
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439
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Holtze C, Sivaramakrishnan R, Antonietti M, Tsuwi J, Kremer F, Kramer KD. The microwave absorption of emulsions containing aqueous micro- and nanodroplets: A means to optimize microwave heating. J Colloid Interface Sci 2006; 302:651-7. [PMID: 16930614 DOI: 10.1016/j.jcis.2006.07.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2006] [Revised: 06/15/2006] [Accepted: 07/05/2006] [Indexed: 10/24/2022]
Abstract
The microwave absorption at frequencies between 10 MHz and 4 GHz is measured for aqueous brine droplets dispersed in a dielectric medium (epsilon(')=2.0). By varying the size of the droplets, ion type and ion concentration, it is found that the microwave absorption goes through a maximum which depends on the type of ions and their concentration. The absorption process is attributed to the polarization of the microdroplets through surface charges. Means to optimize microwave heating in emulsions is discussed.
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Affiliation(s)
- Christian Holtze
- Max Planck Institute of Colloids and Interfaces, Department of Colloid Chemistry, Research Campus Golm, D-14424 Potsdam, Germany
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Sivaramakrishnan R, Tranter RS, Brezinsky K. High Pressure Pyrolysis of Toluene. 1. Experiments and Modeling of Toluene Decomposition. J Phys Chem A 2006; 110:9388-99. [PMID: 16869688 DOI: 10.1021/jp060820j] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The pyrolysis of toluene, the simplest methyl-substituted aromatic molecule, has been studied behind reflected shock waves using a single pulse shock tube. Experiments were performed at nominal high pressures of 27 and 45 bar and spanning a wide temperature range from 1200 to 1900 K. A variety of stable species, ranging from small hydrocarbons to single ring aromatics (principal soot precursors such as phenylacetylene and indene) were sampled from the shock tube and analyzed using standard gas chromatographic techniques. A detailed chemical kinetic model with 262 reactions and 87 species was assembled to simulate the stable species profiles (specifically toluene, benzene and methane) from the current high-pressure pyrolysis data sets and shock tube-atomic resonance absorption spectrometry (ARAS) H atom profiles obtained from prior toluene pyrolysis experiments performed under similar high-temperature conditions and lower pressures from 1.5 to 8 bar. The primary steps in toluene pyrolysis represent the most sensitive and dominant reactions in the model. Consequently, in the absence of unambiguous direct experimental measurements, we have utilized recent high level theoretical estimates of the barrierless association rate coefficients for these primary reactions, C6H5 + CH3 --> C6H5CH3 (1a) and C6H5CH2 + H --> C6H5CH3 (1b) in the detailed chemical kinetic model. The available data sets can be successfully reconciled with revised values for deltaH0f(298K)(C6H5CH2) = 51.5 +/- 1.0 kcal/mol and deltaH0f(298K)(C6H5) = 78.6 +/- 1.0 kcal/mol that translate to primary dissociation rate constants, reverse of 1a and 1b, represented by k(-1a,infinity) = (4.62 x 10(25))T(-2.53)exp[-104.5 x 10(3)/RT] s(-1) and k(-1b,infinity) = (1.524 x 10(16))T(-0.04)exp[-93.5 x 10(3)/RT] s(-1) (R in units of cal/(mol K)). These high-pressure limiting rate constants suggest high-temperature branching ratios for the primary steps that vary from 0.39 to 0.52 over the temperature range 1200-1800 K.
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Affiliation(s)
- R Sivaramakrishnan
- Department of Mechanical & Industrial Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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Sivaramakrishnan R, Tranter RS, Brezinsky K. High Pressure Pyrolysis of Toluene. 2. Modeling Benzyl Decomposition and Formation of Soot Precursors. J Phys Chem A 2006; 110:9400-4. [PMID: 16869689 DOI: 10.1021/jp0608224] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The pyrolysis of toluene, the simplest methyl-substituted aromatic molecule, has been studied behind reflected shock waves using a single pulse shock tube. Part 1 in this two-part series focused on the high-pressure experimental results and the high-pressure limiting rate coefficients for the primary steps in toluene decomposition. The present work focuses on the modeling of benzyl decomposition and the growth of key soot precursors (C2H2, C4H2, C8H6, and indene) from toluene pyrolysis with 81 among the 262 reactions in the detailed toluene model representing the chemistry that describes the formation and decomposition of these species. Feasible pathways for benzyl decomposition as well as phenylacetylene and indene formation have been tested. The simulations also show very good agreement with the single pulse shock tube profiles for the growth of key soot precursors such as C2H2, C4H2, C8H6, and indene.
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Affiliation(s)
- R Sivaramakrishnan
- Department of Mechanical & Industrial Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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Abstract
Whenever physical methods are used in the field of diagnostics, it is necessary to find an unambiguous mapping of the properties of the tested tissues (e.g. normal or pathologic) to their answer to the respective analysis tool such as nuclear magnetic resonance (NMR), ultrasound, x-rays or the relatively new method of parelectric spectroscopy (PS). The well-established non-invasive NMR method has, by now, a sufficiently wide-spread atlas of such mappings. This has to be contrasted to the situation of the PS method where first experiments showed the fulfillment of conditions necessary for any reliable diagnosis, namely the uncertainties of the results being small compared to the differences between the normal and pathologic state of the tissues under test. To help close this gap, we present here results of the behaviour of 12 different organs of mice, taken 20 min after excision and give the dependence of the two most essential PS parameters, the dipole density Delta epsilon and the mobility f(0), on the type of healthy organs. To be able to use tumorous tissues preserved in formaldehyde after excision for comparison purposes, we have been measuring the changes of some organs between the fresh state and the preserved state under formaldehyde for over 180 min each.
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Affiliation(s)
- T Blaschke
- Department of Physics, Freie Universität Berlin, Berlin, Germany
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Lombardi Borgia S, Regehly M, Sivaramakrishnan R, Mehnert W, Korting HC, Danker K, Röder B, Kramer KD, Schäfer-Korting M. Lipid nanoparticles for skin penetration enhancement—correlation to drug localization within the particle matrix as determined by fluorescence and parelectric spectroscopy. J Control Release 2005; 110:151-63. [PMID: 16297487 DOI: 10.1016/j.jconrel.2005.09.045] [Citation(s) in RCA: 173] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2005] [Revised: 09/05/2005] [Accepted: 09/27/2005] [Indexed: 11/16/2022]
Abstract
With topical treatment of skin diseases, the requirement of a high and reproducible drug uptake often still is not met. Moreover, drug targeting to specific skin strata may improve the use of agents which are prone to cause local unwanted effects. Recent investigations have indicated that improved uptake and skin targeting may become feasible by means of nanoparticular systems such as solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC) and nanoemulsions (NE). Here we describe techniques to characterize drug loading to carrier systems and skin penetration profiles by using the lipophilic dye nile red as a model agent. Since the mode of drug association with the particle matrix may strongly influence the efficiency of skin targeting, parelectric spectroscopy (PS) was used to differentiate between matrix incorporation and attachment to the particle surface and fluorescence spectroscopy (FS) to solve dye distribution within NLC particles. Nile red was incorporated into the lipid matrix or the covering tensed shell, respectively, of SLN and NLC with all the lipids studied (Compritol, Precirol, oleic acid, Miglyol). In NLC, the dye was enriched in the liquid phase. Next, nile red concentrations were followed by image analysis of vertical sections of pigskin treated with dye-loaded nanoparticular dispersions and an oil-in-water cream for 4 and 8 h in vitro. Following the SLN dispersions, dye penetration increased about fourfold over the uptake obtained following the cream. NLC turned out less potent (<threefold increase) and penetration appeared even reduced when applying a NE. In contrast to previous studies with glucocorticoids attached to the surface of SLN, a targeting effect was not detected here. Therefore, drug targeting appears to be more strictly related to the mode of interaction of drug and particle than penetration enhancement.
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Sivaramakrishnan R, Kankate L, Niehus H, Kramer KD. Parelectric spectroscopy of drug-carrier-systems—distribution of carrier masses or activation energies. Biophys Chem 2005; 114:221-8. [PMID: 15829356 DOI: 10.1016/j.bpc.2004.12.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2004] [Accepted: 12/08/2004] [Indexed: 12/01/2022]
Abstract
The answer of a high-frequency electromagnetic wave to a sample as termination of an open-ended coaxial line gives the mobility and the density of permanent electric dipole moments in the substance under test. As long as these dipoles are attached to carrier molecules of well defined masses, both parameters can be extracted from the reflected wave in a quick manner giving unambiguous results. The corresponding algorithm has been applied to solid lipid nanoparticles with glucocorticoid molecules attached to or incorporated in the carrier molecules. The results from measurements in the frequency region (0.1-100) MHz have recently been published. As soon as we have to envisage a distribution in carrier masses and/or in activation energies of the attached molecules, we have to apply a more sophisticated evaluation algorithm. The need for a more generalised algorithm is clear as well, when we have to deal with more than one dipole-carrying constituent in the samples. All these evaluation algorithms shall be presented together with the mathematical basis in a short but exact form.
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Tranter RS, Raman A, Sivaramakrishnan R, Brezinsky K. Ethane oxidation and pyrolysis from 5 bar to 1000 bar: Experiments and simulation. INT J CHEM KINET 2005. [DOI: 10.1002/kin.20067] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Sivaramakrishnan R, Tranter RS, Brezinsky K. Ring Conserved Isodesmic Reactions: A New Method for Estimating the Heats of Formation of Aromatics and PAHs. J Phys Chem A 2005; 109:1621-8. [PMID: 16833486 DOI: 10.1021/jp045076m] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Density functional theory (DFT) has been used along with isodesmic reaction schemes to estimate heats of formation for aromatics and polynuclear aromatic hydrocarbons (PAHs). Calculations have been performed for 42 molecules, 12 of which have uncertain or unknown experimental values, using the B3-LYP functional with the small 6-31G(d) basis set. Heats of formation for the group of test molecules were estimated using both conventional bond separation (BS) isodesmic reactions as well as a new technique of ring conserved (RC) isodesmic reactions which is able to correct systematic errors in B3-LYP calculations. When a ring conserved isodesmic reaction based on delocalization energies is used, the estimated heat of formation is more accurate than that obtained by the bond separation technique. The methodology for creating and using appropriate ring conserved isodesmic reactions is discussed. The present scheme also compares favorably against a recently developed bond centered group additivity scheme that was tested against a large number of PAH molecules.
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Affiliation(s)
- R Sivaramakrishnan
- Department of Chemical and Mechanical Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, USA
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Sivaramakrishnan R, Nakamura C, Mehnert W, Korting HC, Kramer KD, Schäfer-Korting M. Glucocorticoid entrapment into lipid carriers--characterisation by parelectric spectroscopy and influence on dermal uptake. J Control Release 2005; 97:493-502. [PMID: 15212881 DOI: 10.1016/j.jconrel.2004.04.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2004] [Accepted: 04/02/2004] [Indexed: 11/26/2022]
Abstract
Topical glucocorticoids such as betamethasone 17-valerate (BMV) and prednicarbate (PC) are an important therapeutic option in atopic eczema. To reduce the risk of dermal atrophy, we aimed at BMV incorporation into solid lipid nanoparticles (SLN) for epidermal targeting using various lipids and emulsifiers corresponding to previous work on PC. Cutaneous absorption into excised human skin was compared to the one with a cream. While Compritol-based particles increased BMV uptake about fourfold we failed, however, to obtain epidermal targeting. To obtain insight into the location of active substance relative to the carrier, we used the recently optimised method of parelectric spectroscopy (PS). In fact, we were able to study electric dipole movements in the broad field of a frequency span from 0.1 to 100 MHz demonstrating that glucocorticoids are attached to the particle surface but are not incorporated into the lipid matrix. With BMV, the loading capacity of the particle surface lies clearly below the usual concentration of 0.1% which is not the case with PC. An adequate association of drug and carrier is essential for epidermal targeting. Parelectric spectroscopy provides insight into the interaction between drug and lipidic carrier.
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Tranter RS, Sivaramakrishnan R, Srinivasan N, Brezinsky K. Calibration of reaction temperatures in a very high pressure shock tube using chemical thermometers. INT J CHEM KINET 2001. [DOI: 10.1002/kin.1069] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Affiliation(s)
- V P Gangadharan
- Department of Medical Oncology, Regional Cancer Centre, Trivandrum, India
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Kasturi T, Amruta Reddy P, Mandal A, Sivaramakrishnan R, Rajasekhar B, Ganesha Prasad K, Radhakrishnan R, Viswamitra M. One pot synthesis of polycyclic oxygen aromatics. Tetrahedron 1990. [DOI: 10.1016/s0040-4020(01)87889-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Murty VM, De SK, Bhagawan SS, Sivaramakrishnan R, Athithan SK. Viscoelastic properties of short-fiber-reinforced rubber composites and the role of adhesion. J Appl Polym Sci 1983. [DOI: 10.1002/app.1983.070281113] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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