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Wong A, Morgis R, Entenman J, Ramirez SI, Hays AL, Wright TS, Scartozzi CM, Ruffin MT, Moss JL. Exploratory Analysis of Concordance Between Clinician-Collected and Self-Sampled Human Papillomavirus Tests in a Small Cohort of Average- and High-Risk Patients. Womens Health Rep (New Rochelle) 2024; 5:259-266. [PMID: 38516651 PMCID: PMC10956530 DOI: 10.1089/whr.2024.0004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 02/13/2024] [Indexed: 03/23/2024]
Abstract
Objectives Cervical cancer screening rates have stagnated, but self-sampling modalities have the potential to increase uptake. This study compares the test characteristics of self-sampled high-risk human papillomavirus (hrHPV) tests with clinician-collected hrHPV tests in average-risk (i.e., undergoing routine screening) and high-risk patients (i.e., receiving follow-up after abnormal screening results). Methods In this cross-sectional study, a relatively small cohort of average-risk (n = 35) and high-risk (n = 12) participants completed both clinician-collected and self-sampled hrHPV testing, along with a brief phone survey. We assessed hrHPV positivity, concordance, positive predictive value (PPV), negative predictive value (NPV), sensitivity, and specificity across both methods (for types 16, 18, or other hrHPV). We also explored the relationship between test concordance and sociodemographic/behavioral factors. Results Among average-risk participants, hrHPV positivity was 6% for both test methods (i.e., hrHPV-positive cases: n = 2), resulting in reported concordance, PPV, NPV, sensitivity, and specificity of 100%. Among high-risk participants, hrHPV positivity was 100% for clinician-collected tests but only 67% for self-sampled tests, showing varied concordance and sensitivity. Concordance was not associated with sociodemographic or behavioral factors. Conclusions Self-sampled hrHPV testing demonstrated high accuracy for average-risk patients in this exploratory study. However, its performance was less consistent in high-risk patients who had already received an abnormal screening result, which could be attributed to spontaneous viral clearance over time. The limited number of participants, particularly HPV-positive cases, suggests caution in interpreting these results. Further research with larger cohorts is necessary to validate these findings and to explore the integration of self-sampled hrHPV testing into routine clinical care, particularly for patients with a history of cervical abnormalities. Clinical Trial Registration NCT04591977, NCT04585243.
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Affiliation(s)
- Ashley Wong
- Penn State College of Medicine, The Pennsylvania State University, Hershey, Pennsylvania, USA
| | - Rebecca Morgis
- Penn State College of Medicine, The Pennsylvania State University, Hershey, Pennsylvania, USA
| | - Juliette Entenman
- Department of Family and Community Medicine, Penn State College of Medicine, The Pennsylvania State University, Hershey, Pennsylvania, USA
| | - Sarah I. Ramirez
- Department of Family and Community Medicine, Penn State College of Medicine, The Pennsylvania State University, Hershey, Pennsylvania, USA
| | - Amy L. Hays
- Department of Family and Community Medicine, Penn State College of Medicine, The Pennsylvania State University, State College, Pennsylvania, USA
| | - Tonya S. Wright
- Department of Obstetrics and Gynecology, Penn State College of Medicine, The Pennsylvania State University, Hershey, Pennsylvania, USA
| | - Christina M. Scartozzi
- Department of Family and Community Medicine, Penn State College of Medicine, The Pennsylvania State University, Reading, Pennsylvania, USA
| | - Mack T. Ruffin
- Department of Family and Community Medicine, Penn State College of Medicine, The Pennsylvania State University, Hershey, Pennsylvania, USA
| | - Jennifer L. Moss
- Department of Family and Community Medicine, Penn State College of Medicine, The Pennsylvania State University, Hershey, Pennsylvania, USA
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Popalis ML, Ramirez SI, Leach KM, Granzow ME, Stoltzfus KC, Moss JL. Improving cervical cancer screening rates: a scoping review of resources and interventions. Cancer Causes Control 2022; 33:1325-1333. [PMID: 35980511 PMCID: PMC10124066 DOI: 10.1007/s10552-022-01618-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 08/03/2022] [Indexed: 12/01/2022]
Abstract
INTRODUCTION Cervical cancer mortality can be prevented through early detection with screening methods such as Pap and high-risk human papillomavirus (hrHPV) tests; however, only 81% of women aged 21-65 are up-to-date on screening. Many interventions to increase cervical cancer screening have been implemented, but there is limited understanding about which intervention components are most successful. METHODS We conducted a scoping review of existing literature and available resources for cervical cancer screening interventions to identify gaps in the research. We used t tests and correlations to identify associations among intervention components and effect sizes. RESULTS Out of nine studies, the mean overall effect size for interventions was 11.3% increase in Pap testing for cervical cancer screening (range = - 4-24%). Interventions that included community health workers or one-on-one interaction had the biggest effect size (p < 0.05). No associations with effect size were noted for literacy level, number of intervention components, or targeting by race/ethnicity. CONCLUSIONS Future interventions may include educational sessions with community health workers or one-on-one patient interaction to improve cervical cancer screening. Further research is needed to establish effect sizes for large-scale interventions and hrHPV screening interventions.
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Affiliation(s)
- Madyson L Popalis
- Department of Family and Community Medicine, Penn State College of Medicine, Hershey, PA, USA
| | - Sarah I Ramirez
- Department of Family and Community Medicine, Penn State College of Medicine, Hershey, PA, USA
| | - Kelsey M Leach
- Department of Family and Community Medicine, Penn State College of Medicine, Hershey, PA, USA
| | - Marni E Granzow
- Department of Family and Community Medicine, Penn State College of Medicine, Hershey, PA, USA
| | - Kelsey C Stoltzfus
- Department of Family and Community Medicine, Penn State College of Medicine, Hershey, PA, USA
| | - Jennifer L Moss
- Department of Family and Community Medicine, Penn State College of Medicine, Hershey, PA, USA.
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Sznajder KK, Kjerulff KH, Wang M, Hwang W, Ramirez SI, Gandhi CK. Covid-19 vaccine acceptance and associated factors among pregnant women in Pennsylvania 2020. Prev Med Rep 2022; 26:101713. [PMID: 35127367 PMCID: PMC8800167 DOI: 10.1016/j.pmedr.2022.101713] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 01/06/2022] [Accepted: 01/23/2022] [Indexed: 01/10/2023] Open
Abstract
Data on factors associated with vaccine acceptance among pregnant women are critical to the rapid scale up of interventions to improve vaccine uptake. When COVID-19 vaccines were still in the testing phases of research, we surveyed pregnant women accessing prenatal care at an academic medical institution in Central Pennsylvania, United States to examine factors associated with vaccine acceptance. Willingness to receive a COVID-19 vaccine once a vaccine became available was asked as part of an ongoing study on the COVID-19 pandemic and pregnancy (n = 196). Overall, 65% of women reported they would be willing or somewhat willing to receive the COVID-19 vaccine. Women who had received an influenza vaccine within the past year were more likely to be willing to receive the COVID-19 vaccine than women who had never received an influenza vaccine or those who received it over one year ago (aOR 4.82; 95% CI 2.17, 10.72). Similarly, women who were employed full-time were more willing to receive the COVID-19 vaccine than women who were not employed full time (aOR 2.22; 95% CI 1.02, 4.81), and women who reported feeling overloaded were more willing to receive the COVID-19 vaccine than women who did not feel overloaded (aOR 2.18; 95% CI 1.02, 4.68). Our findings support the need to increase vaccination education among pregnant women before vaccines are rolled out, especially those who have not received an influenza vaccine within the past year. Improved understanding of willingness to vaccinate among pregnant women will improve future pandemic responses and current vaccination efforts.
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Affiliation(s)
- Kristin K. Sznajder
- Department of Public Health Sciences, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
- Corresponding author at: Department of Public Health Sciences, Pennsylvania State University College of Medicine, 90 Hope Drive, Hershey, PA 17033, USA.
| | - Kristen H. Kjerulff
- Department of Public Health Sciences, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Ming Wang
- Department of Public Health Sciences, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Wenke Hwang
- Department of Public Health Sciences, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Sarah I. Ramirez
- Department of Family and Community Medicine, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
| | - Chintan K. Gandhi
- Department of Pediatrics, Pennsylvania State University College of Medicine, Hershey, PA 17033, USA
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Moss JL, Popalis M, Ramirez SI, Reedy-Cooper A, Ruffin MT. Disparities in Cancer Screening: The Role of County-Level Metropolitan Status and Racial Residential Segregation. J Community Health 2021; 47:168-178. [PMID: 34550504 DOI: 10.1007/s10900-021-01035-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/17/2021] [Indexed: 12/21/2022]
Abstract
Mortality from cervical and colorectal cancers can be reduced through routine screening, which can often be accessed through primary care. However, uptake of screening in the US remains suboptimal, with disparities observed across geographic characteristics, such as metropolitan status or level of racial residential segregation. Little is known about the interaction of metropolitan status and segregation in their relationship with cancer screening. We conducted a quantitative survey of 474 women aged 45-65 in central Pennsylvania. The survey collected county-level characteristics and participant-level demographics, beliefs, cancer screening barriers, and cervical and colorectal cancer screening. We used bivariate and multivariable logistic regression to analyze relationships between metropolitan status and segregation with screening. For cervical cancer screening, 82.8% of participants were up-to-date, which did not differ by county type in the final analysis. Higher healthcare trust, higher cancer fatalism, and reporting cost as a barrier were associated with cervical cancer screening. For colorectal cancer screening, 55.4% of participants were up-to-date, which differed by county type. In metropolitan counties, segregation was not associated with colorectal cancer screening, but in non-metropolitan counties, segregation was associated with greater colorectal cancer screening. The relationship between metropolitan status and being up-to-date with colorectal, but not cervical, cancer screening varied by segregation. Other important beliefs and barriers to screening varied by county type. This research can guide future cancer screening interventions in primary care settings in underserved communities.
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Affiliation(s)
- Jennifer L Moss
- Penn State College of Medicine, The Pennsylvania State University, Hershey, PA, USA.
- Department of Family and Community Medicine, Department of Public Health Sciences, Penn State College of Medicine, The Pennsylvania State University, 134 Sipe Ave., #205, MC HS72, P.O. Box 850, Hershey, PA, 17033, USA.
| | - Madyson Popalis
- Penn State College of Medicine, The Pennsylvania State University, Hershey, PA, USA
| | - Sarah I Ramirez
- Penn State College of Medicine, The Pennsylvania State University, Hershey, PA, USA
| | - Alexis Reedy-Cooper
- Penn State College of Medicine, The Pennsylvania State University, Hershey, PA, USA
| | - Mack T Ruffin
- Penn State College of Medicine, The Pennsylvania State University, Hershey, PA, USA
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Abstract
Women's health is largely influenced by cultural beliefs, local traditions, and access to care across the world. Immigrant and refugee women experience health in varied ways; prior experiences with health care and beliefs about health should be explored with women on their arrival to the United States. Topics that should be discussed include menstrual practices, contraception and beliefs about family planning, prior screening for preventable diseases, pregnancies and experiences with childbirth, sexual assault and trauma, and history of traditional practices, including female genital mutilation (dependent on area of origin).
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Affiliation(s)
- Alison N Huffstetler
- Department of Family Medicine and Population Health, Virginia Commonwealth University, 830 East Main Street, Richmond, VA 23219, USA.
| | - Sarah I Ramirez
- Department of Family and Community Medicine, Penn State Health, Milton S. Hershey Medical Center, 500 University Drive, Hershey, PA 17033, USA
| | - Sarah N Dalrymple
- Department of Family Medicine, University of Virginia, PO Box 800729, Charlottesville, VA 22908, USA
| | - Megan H Mendez Miller
- Department of Family and Community Medicine, Penn State Health, Milton S. Hershey Medical Center, 500 University Drive, Hershey, PA 17033, USA
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Vargas Pelaez AF, Ramirez SI, Valdes Sanchez C, Piedra Abusharar S, Romeu JC, Carmichael C, Bascoy S, Baron R, Pichardo-Lowden A, Albarracin N, Jones CC, Silveyra P. Implementing a medical student interpreter training program as a strategy to developing humanism. BMC Med Educ 2018; 18:141. [PMID: 29914460 PMCID: PMC6006684 DOI: 10.1186/s12909-018-1254-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Accepted: 06/11/2018] [Indexed: 05/19/2023]
Abstract
BACKGROUND Humanistic care in medicine has shown to improve healthcare outcomes. Language barriers are a significant obstacle to humanistic care, and trained medical interpreters have demonstrated to effectively bridge the gap for the vulnerable limited English proficiency (LEP) patient population. One way in which medical schools can train more humanistic physicians and provide language access is through the implementation of programs to train bilingual medical students as medical interpreters. The purpose of this prospective study was to evaluate whether such training had an impact on bilingual medical student's interpretation skills and humanistic traits. METHODS Between 2015 and 2017, whole-day (~ 8 h) workshops on medical interpretation were offered periodically to 80 bilingual medical students at the Penn State College of Medicine. Students completed a series of questionnaires before and after the training that assessed the program's effectiveness and its overall impact on interpretation skills and humanistic traits. Students also had the opportunity to become certified medical interpreters. RESULTS The 80 student participants were first- to third- year medical students representing 21 languages. Following training, most students felt more confident interpreting (98%) and more empathetic towards LEP patients (87.5%). Students' scores in the multiple-choice questions about medical interpretation/role of the interpreter were also significantly improved (Chi-Square test, p < 0.05). All students who decided to take the exam were able to successfully become certified interpreters. Ninety-two percent of participants reported they would recommend the program and would be willing to serve as a future "coaches" for interpreter training workshops delivered to peer students. CONCLUSIONS Our program was successful in increasing self-reported measures of empathy and humanism in medical students. Our data suggests that implementation of medical interpreter training programs can be a successful strategy to develop of humanism in medical students, and aid in the development of sustainable language access for LEP patients.
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Affiliation(s)
| | - Sarah I. Ramirez
- Department of Family and Community Medicine, Penn State College of Medicine, Hershey, PA USA
| | | | | | - Jose C. Romeu
- Department of Medicine, Penn State College of Medicine, Hershey, PA USA
| | | | | | - Rose Baron
- Penn State College of Medicine, Hershey, PA USA
| | | | | | | | - Patricia Silveyra
- Departments of Pediatrics, Biochemistry and Molecular Biology, and Humanities, Penn State College of Medicine, 500 University Drive, Mail Code H085, Hershey, PA 17033 USA
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Petrache I, Birukova A, Ramirez SI, Garcia JGN, Verin AD. The role of the microtubules in tumor necrosis factor-alpha-induced endothelial cell permeability. Am J Respir Cell Mol Biol 2003; 28:574-81. [PMID: 12707013 DOI: 10.1165/rcmb.2002-0075oc] [Citation(s) in RCA: 249] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Tumor necrosis factor (TNF)-alpha, a major proinflammatory cytokine, triggers endothelial cell activation and barrier dysfunction which are implicated in the pathogenesis of pulmonary edema associated with acute lung injury syndromes. The mechanisms of TNF-alpha-induced vascular permeability are not completely understood. Our initial experiments demonstrated that TNF-alpha-induced decreases in transendothelial electrical resistance across human pulmonary artery endothelial cells are independent of myosin light chain phosphorylation catalyzed by either myosin light chain kinase or Rho kinase. We next assessed the involvement of another cytoskeletal component, the tubulin-based microtubule network, and found TNF-alpha to induce a decrease in stable tubulin content and partial dissolution of peripheral microtubule network as evidenced by anti-acetylated tubulin and anti-beta-tubulin immunofluorescent staining, respectively. Microtubule-stabilizing agents, paclitaxel and epothilone B, significantly attenuated TNF-alpha-induced decreases in transendothelial electrical resistance, inhibited the cytokine-induced increases in actin stress fibers, formation of intercellular gap, and restored the TNF-alpha-compromised vascular endothelial (VE)-cadherin-based cell-cell junctions. Importantly, neither TNF-alpha nor paclitaxel treatment was associated with endothelial cell apoptosis. Inhibition of p38 mitogen-activated protein kinase by SB203580 significantly attenuated TNF-alpha-induced microtubule destabilization, actin rearrangement, and endothelial barrier dysfunction. These results strongly suggest the involvement of microtubule rearrangement in TNF-alpha-induced endothelial cell permeability via p38 mitogen-activated protein kinase activation.
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Affiliation(s)
- Irina Petrache
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Abstract
Since 1997, after having identified for the first time C4N2 (the only molecule detected on Titan and undetected in the laboratory at this date) in a simulated atmosphere of Titan, our group intended to determine several properties (including optical behavior) of laboratory analogues of Titan's tholins. This article summarizes the results obtained in the frame of that program (observation by microscopy, solubility in hydrocarbons and nitriles, chemical composition, and optical behavior in the 200-900nm range), and finally investigates the following items: what are the key questions still remaining?; how to answer them?
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Affiliation(s)
- P Coll
- Laboratoire des Systemes Atmospheriques, UMR CNRS 7583, Universites Paris 7 et 12 France
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Navarro-Gonzalez R, Ramirez SI, de la Rosa JG, Coll P, Raulin F. Production of hydrocarbons and nitriles by electrical processes in Titan's atmosphere. Adv Space Res 2001; 27:271-282. [PMID: 11605642 DOI: 10.1016/s0273-1177(01)00057-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Although lightning has not been observed in Titan's atmosphere, the presence of methane rain in the troposphere suggests the possibility of electrical activity in the form of corona and/or lightning discharges. Here we examine the chemical effects of these electrical processes on a Titan simulated atmosphere composed of CH4 in N2 at various mixing ratios. Corona discharges were simulated in two different experimental arrays. For the detection of reactive intermediates we used a mass spectrometer to study the main positive ions arising by bombarding low-energy electrons from a hot filament into low-pressure methane. The final stable products, generated by applying a high voltage in a coaxial reactor with either positive or negative polarity, were separated and detected by gas chromatography-Fourier transform infrared spectroscopy and electron impact mass spectrometry (GC-FTIR-MS). Lightning discharges were simulated by a hot and dense plasma generated by a Nd-YAG laser and the final products were separated and detected by GC-FTIR-MS. Corona discharges produce linear and branched hydrocarbons as well as nitriles whereas lightning discharges generate mainly unsaturated hydrocarbons and nitriles. Lightning discharges are about 2 orders of magnitude more efficient in product formation than corona discharges.
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Affiliation(s)
- R Navarro-Gonzalez
- Laboratorio de Quimica de Plasmas y Estudios Planetarios, Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Circuito Exterior, Ciudad Universitaria, Apartado Postal 70-543, Mexico D.F. 04510, Mexico
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Ramirez SI, Navarro-Gonzalez R, Coll P, Raulin F. Possible contribution of different energy sources to the production of organics in Titan's atmosphere. Adv Space Res 2001; 27:261-270. [PMID: 11605641 DOI: 10.1016/s0273-1177(01)00056-4] [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] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
A quantitative comparison of the products arising from the irradiation of a Titan's simulated atmosphere is presented. The energy sources used represent some of the main events that occur in the satellite's atmosphere. All of the compounds identified are classified in the hydrocarbon and nitrile chemical families. Almost all of the detected compounds in Titan's atmosphere are produced by one or more energy sources. The compounds with the highest energy yields include the C2 hydrocarbons, methanonitrile and ethanonitrile. The possibility of using some of the produced organics as tracer compounds during the Huygens descend to identify the leading energy form in the different atmospheric levels remains open.
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Affiliation(s)
- S I Ramirez
- Laboratorio de Quimica de Plasmas y Estudios Planetarios, Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Circuito Exterior, C.U., Apartado Postal 70-543, Mexico D.F. 04510, Mexico
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Abstract
The atmosphere of Titan is constantly bombarded by galactic cosmic rays and Saturnian magnetospheric electrons causing the formation of free electrons and primary ions, which are then stabilized by ion cluster formation and charging of aerosols. These charged particles accumulate in drops in cloud regions of the troposphere. Their abundance can substantially increase by friction, fragmentation or collisions during convective activity. Charge separation occurs with help of convection and gravitational settling leading to development of electric fields within the cloud and between the cloud and the ground. Neutralization of these charged particles leads to corona discharges which are characterized by low current densities. We have therefore, experimentally studied the corona discharge of a simulated Titan's atmosphere (10% methane and 2% argon in nitrogen) at 500 Torr and 298 K by GC-FTIR-MS techniques. The main products have been identified as hydrocarbons (ethane, ethyne, ethene, propane, propene+propyne, cyclopropane, butane, 2-methylpropane, 2-methylpropene, n-butane, 2-butene, 2,2-dimethylpropane, 2-methylbutane, 2-methylbutene, n-pentane, 2,2-dimethylbutane, 2-methylpentane, 3-methylpentane, n-hexane, 2,2-dimethylhexane, 2,2-dimethylpentane, 2,2,3-trimethylbutane, 2,3-dimethylpentane and n-heptane), nitriles (hydrogen cyanide, cyanogen, ethanenitrile, propanenitrile, 2-methylpropanenitrile and butanenitrile) and a highly branched hydrocarbon deposit. We present the trends of hydrocarbons and nitriles formation as a function of discharge time in an ample interval and have derived their initial yields of formation. The results clearly demonstrate that a complex organic chemistry can be initiated by corona processes in the lower atmosphere. Although photochemistry and charged particle chemistry occurring in the stratosphere can account for many of the observed hydrocarbon species in Titan, the predicted abundance of ethene is too low by a factor of 10 to 40. While some ethene will be produced by charged-particle chemistry, the production of ethene by corona processes and its subsequent diffusion into the stratosphere appears to be an adequate source. Because little UV penetrates to the lower atmosphere to destroy the molecules formed there, the corona-produced species may be long-lived and contribute significantly to the composition of the lower atmosphere and surface.
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Affiliation(s)
- R Navarro-Gonzalez
- Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, DF.
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12
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Abstract
The atmosphere of Titan is constantly bombarded by galactic cosmic rays and Saturnian magnetospheric electrons causing the formation of free electrons and primary ions, which are then stabilized by ion cluster formation and charging of aerosols. These charged particles accumulate in drops in cloud regions of the troposphere. Their abundance can substantially increase by friction, fragmentation or collisions during convective activity. Charge separation occurs with help of convection and gravitational settling leading to development of electric fields within the cloud and between the cloud and the ground. Neutralization of these charge particles leads to corona discharges which are characterized by low current densities. These electric discharges could induce a number of chemical reactions in the troposphere and hence it is of interest to explore such effects. We have therefore, experimentally studied the corona discharge of a simulated Titan's atmosphere (10% methane and 2% argon in nitrogen) at 500 Torr and 298 K by GC-FTIR-MS techniques. The main products have been identified as hydrocarbons (ethane, ethyne, ethene, propane, propene + propyne, cyclopropane, butane, 2-methylpropane, 2-methylpropene, n-butene, 2-butene, 2,2-dimethylpropane, 2-methylbutane, 2-methylbutene, n-pentane, 2,2-dimethylbutane, 2-methylpentane, 3-methylpentane, n-hexane, 2,2-dimethylhexane, 2,2-dimethylpentane, 2,2,3-trimethylbutane, 2,3-dimethylpentane and n-heptane), nitriles (hydrogen cyanide, cyanogen, ethanenitrile, propanenitrile, 2-methylpropanenitrile and butanenitrile) and an uncharacterized film deposit. We present their trends of formation as a function of discharge time in an ample interval and have derived their initial yields of formation. These results clearly demonstrate that a complex organic chemistry can be initiated by corona processes in the lower atmosphere. Although photochemistry and charged particle chemistry occurring in the stratosphere can account for many of the observed hydrocarbon species in Titan, the predicted abundance of ethene is to low by a factor of 10 to 40. While some ethene will be produced by charged-particle chemistry, its production by corona processes and subsequent diffusion into the stratosphere appears to be an adequate source. Because little UV penetrates to the lower atmosphere to destroy the molecules formed there, the corona-produced species may be long-lived and contribute significantly to the composition of the lower atmosphere and surface.
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Affiliation(s)
- R Navarro-Gonzalez
- Laboratoire de Quimica de Plasmas y Estudios Planetarios, Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Mexico D.F
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