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405 results on '"Langevin, R."'

1. Perceived Acceptability of Child Maltreatment as a Moderator of the Association Between Experiences of Child Maltreatment and Post-Traumatic Symptoms : A Cross-Cultural Study

Author

Bartoli, E., Wadji, D. L., Oe, M., Cheng, P., Martin-Soelch, C., Pfaltz, Monique C., Langevin, R., Bartoli, E., Wadji, D. L., Oe, M., Cheng, P., Martin-Soelch, C., Pfaltz, Monique C., and Langevin, R.

Abstract

Despite the well-documented link between child maltreatment (CM) and mental health, evidence suggests substantial variability in the post-traumatic sequelae of CM across cultures. The perceived acceptability of CM in one’s community might moderate the association between CM and mental health, but little research has been conducted on it so far. This study examined how the perceived acceptability of CM may influence the relationship between CM experiences and post-traumatic symptoms in individuals from four different continents and if the pattern of associations is the same across countries. We recruited a sample of 478 adults from Cameroon (n = 111), Canada (n = 137), Japan (n = 108), and Germany (n = 122). We administered online questionnaires and performed multiple group moderation analyses for total CM, neglect, physical abuse, emotional maltreatment, sexual abuse, and exposure to domestic violence (DV). A significant positive main effect of CM on post-traumatic symptoms was found in the overall sample and in Cameroon; in Germany, only neglect and emotional maltreatment were positively associated to post-traumatic symptoms. Moderation effects were identified; the perceived acceptability of neglect in Cameroon and Germany and of exposure to DV in Cameroon had a dampening effect on the relationship between CM experiences and post-traumatic symptoms. Our findings confirm that CM experiences entail long-term post-traumatic sequelae that can vary across cultures and CM subtypes and further our understanding of this issue by showing that the perceived acceptability of CM may be an understudied moderator.

Published
2024
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2. Space of subspheres and conformal invariants of curves

Author

Langevin, R., O'Hara, J., and Sakata, S.

Subjects
Mathematics - Differential Geometry, 53A30, 53B30
Abstract

A space curve is determined by conformal arc-length, conformal curvature, and conformal torsion, up to M\"obius transformations. We use the spaces of osculating circles and spheres to give a conformally defined moving frame of a curve in the Minkowski space, which can naturally produce the conformal invariants and the normal form of the curve. We also give characterization of canal surfaces in terms of curves in the set of circles., Comment: 14pages

Published
2011

3. Conformal invariance of the writhe of a knot

Author

Langevin, R. and O'Hara, J.

Subjects
Mathematics - Geometric Topology, Mathematics - Differential Geometry, 57M25, 53A30
Abstract

We give a new proof of an old theorem by Banchoff and White 1975 that claims that the writhe of a knot is conformally invariant., Comment: 10 pages, 3 figures

Published
2008

5. Conformally invariant energies of knots II

Author

Langevin, R. and O'Hara, J.

Subjects
Mathematics - Geometric Topology, Mathematics - Differential Geometry, 57M25, 53A30
Abstract

This paper has been withdrawn by the authors, as it was combined with "Conformally invariant energies of knots I" (math/0409396) to be "Conformally invariant energies of knots" which has replaced the former., Comment: This paper has been withdrawn by the authors, as it was combined with "Conformally invariant energies of knots I" (math/0409396) to be "Conformally invariant energies of knots" which has replaced the former

Published
2004

6. Conformally invariant energies of knots

Author

Langevin, R. and O'Hara, J.

Subjects
Mathematics - Geometric Topology, Mathematics - Differential Geometry, 57M25, 53A30
Abstract

Conformally invariant functionals on the space of knots are introduced via extrinsic conformal geometry of the knot and integral geometry on the space of spheres. Our functionals are expressed in terms of a complex-valued 2-form which can be considered as the cross-ratio of a pair of infinitesimal segments of the knot. We show that our functionals detect the unknot as the total curvature does, and that their values explode if a knot degenerates to a singular knot with double points., Comment: 66 pages, 25 figures, to appear in J. Institut Math. Jussieu

Published
2004

7. How are experiences and acceptability of child maltreatment related to resilience and posttraumatic growth : a cross cultural study

Author

Wadji, D. L., Oe, M., Bartoli, E., Martin-Soelch, C., Pfaltz, Monique C., Langevin, R., Wadji, D. L., Oe, M., Bartoli, E., Martin-Soelch, C., Pfaltz, Monique C., and Langevin, R.

Abstract

Background: Post-traumatic growth (PTG) and resilience, regarded as positive psychological change following a traumatic experience, are under-researched across cultures in people exposed to child maltreatment (CM). Objective: We investigated how experiences and the perceived acceptability of CM are related to resilience and PTG in countries with different cultures, living standards, and gross national income. Method: A total of 478 adults from Cameroon (n = 111), Canada (n = 137), Japan (n = 108), and Germany (n = 122) completed an online survey with self-reported questionnaires, including the Brief Resilience Scale and the Post Traumatic Growth Inventory-Short Form. Results: Across countries, self-reported male gender and age were positively associated with resilience, while experiences of physical abuse and emotional maltreatment were negatively associated with resilience. Experiences of emotional maltreatment were positively associated with PTG. Higher levels of PTG and resilience were found amongst Cameroonian participants as compared to other countries. Conclusion: Our results suggest that positive changes following CM can vary significantly across cultures and that experiences of specific CM subtypes, but not the perceived acceptability of CM, may be important for a deeper understanding of how individuals overcome trauma and develop salutogenic outcomes. Our findings may inform CM intervention programmes for an enhanced cultural sensitivity.

Published
2023
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8. Associations between experiences of childhood maltreatment and perceived acceptability of child maltreatment : A cross-cultural and exploratory study

Author

Wadji, D. L., Oe, M., Cheng, P., Bartoli, E., Martin-Soelch, C., Pfaltz, Monique C., Langevin, R., Wadji, D. L., Oe, M., Cheng, P., Bartoli, E., Martin-Soelch, C., Pfaltz, Monique C., and Langevin, R.

Abstract

Background: Acceptable parental behaviors and practices toward a child vary across countries and may impact the risk of exposure to maltreatment. Conversely, prior experiences of maltreatment as a child may influence the acceptability of child maltreatment (CM) behaviors. Objective: This exploratory study examined the association between CM experiences and perceived acceptability of CM using data from four countries representing different cultures, living standards, and gross national income. Participants and setting: We recruited a convenience sample of 478 adults from Cameroon (n = 111), Canada (n = 137), Japan (n = 108), and Germany (n = 122) through online postings on social media. Methods: We administered questionnaires and conducted a three-stage hierarchical multiple regression with perceived acceptability of CM subscales as the dependent variable. Results: In all countries, higher scores of childhood neglect were associated with greater perceived acceptability of neglect in one's community (p <.001). Equally, our results showed that higher scores of childhood neglect or sexual abuse were associated with greater perceived acceptability of sexual abuse (p <.044). However, we did not find a significant relationship between other forms of CM (i.e., physical abuse, emotional maltreatment, exposure to domestic violence), and their perceived acceptability. Conclusions: Our findings suggest that experiences of some CM types, namely neglect and sexual abuse, may be associated with the perception that these are more acceptable within one's community. Perceived acceptability of CM might be a driver that can either prevent or perpetuate CM. Therefore, intervention and prevention programs could incorporate a deeper cross-cultural understanding and assessment of these social norms in order to foster meaningful behavioral changes.

Published
2023
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9. Social functioning in individuals affected by childhood maltreatment: establishing a research agenda to inform interventions

Author

Ceylan, Deniz (ORCID 0000-0002-1438-8240 & YÖK ID 137755), Pfaltz, M.C.; Halligan, S.L.; Haim-Nachum, S.; Sopp, M.R.; Ahs, F.; Bachem, R.; Bartoli, E.; Belete, H.; Belete, T.; Berzengi, A.; Dukes, D.; Essadek, A.; Iqbal, N.; Jobson, L.; Langevin, R.; Levy-Gigi, E.; Lüönd, A.M.; Martin-Soelch, C.; Michael, T.; Oe, M.; Olff, M.; Raghavan, V.; Ramakrishnan, M.; Sar V.; Spies, G.; Wadji, D.L.; Wamser-Nanney, R.; Fares-Otero, N.E.; Schnyder, U.; Seedat, S., School of Medicine, Ceylan, Deniz (ORCID 0000-0002-1438-8240 & YÖK ID 137755), Pfaltz, M.C.; Halligan, S.L.; Haim-Nachum, S.; Sopp, M.R.; Ahs, F.; Bachem, R.; Bartoli, E.; Belete, H.; Belete, T.; Berzengi, A.; Dukes, D.; Essadek, A.; Iqbal, N.; Jobson, L.; Langevin, R.; Levy-Gigi, E.; Lüönd, A.M.; Martin-Soelch, C.; Michael, T.; Oe, M.; Olff, M.; Raghavan, V.; Ramakrishnan, M.; Sar V.; Spies, G.; Wadji, D.L.; Wamser-Nanney, R.; Fares-Otero, N.E.; Schnyder, U.; Seedat, S., and School of Medicine

Abstract

Childhood maltreatment (CM) is linked to impairments in various domains of social functioning. Here, we argue that it is critical to identify factors that underlie impaired social functioning as well as processes that mediate the beneficial health effects of positive relationships in individuals exposed to CM. Key research recommendations are presented, focusing on: (1) identifying attachment-related alterations in specific inter- and intrapersonal processes (e.g., regulation of closeness and distance) that underlie problems in broader domains of social functioning (e.g., lack of perceived social support) in individuals affected by CM; (2) identifying internal (e.g., current emotional state) and external situational factors (e.g., cultural factors, presence of close others) that modulate alterations in specific social processes; and (3) identifying mechanisms that explain the positive health effects of intact social functioning. Methodological recommendations include: (1) assessing social processes through interactive and (close to) real-life assessments inside and outside the laboratory; (2) adopting an interdisciplinary, lifespan perspective to assess social processes, using multi-method assessments; (3) establishing global research collaborations to account for cultural influences on social processes and enable replications across laboratories and countries. The proposed line of research will contribute to globally develop and refine interventions that prevent CM and further positive relationships, which - likely through buffering the effects of chronic stress and corresponding allostatic load - foster resilience and improve mental and physical health, thereby reducing personal suffering and the societal and economic costs of CM and its consequences. Interventions targeting euthymia and psychological well-being are promising therapeutic concepts in this context., Swiss National Science Foundation; CIBERSAM; Biomedical Research Networking Center for Mental Health Network; German Academic Exchange Service (DAAD)

Published
2022

10. Two Necessary Conditions for Creativity.

Author

Ontario Inst. for Studies in Education, Toronto., Day, H. I., and Langevin, R.

Abstract

It is proposed that both curiosity and intelligence are necessary but not sufficient conditions for creative production. Research literature is discussed concerning curiosity as a motivational construct (a state of arousal), and as a personality trait, supporting the notion that curiosity is necessary to creativity. Research relating intelligence and creativity is then discussed, coming to the general consensus that creative individuals must have at least minimal ability to deal inventively with symbol systems and to conceptualize the environment. The authors find that both traits correlate significantly with high scores in a test of creativity. Some 75 nursing students were asked to complete intelligence and curiosity tests as well as the Remote Association Test and a test which required production of humorous captions for a number of Thematic Apperception Test cards. Results generally supported the hypothesis. (BP)

Published
1968

13. Mental health responses to COVID-19 around the world

Author

Olff, M., Primasari, I., Qing, Y., Coimbra, B. M., Hovnanyan, A., Grace, E., Williamson, R. E., Hoeboer, C. M., Aakvaag, H. F., Ajdukovic, D., Anastassiou-Hadjicharalambous, X., Bakker, A., Brocker, E. E., Cantoni, L., Cloitre, M., de Soir, E. L. J. L., Dragandragan, M., Dyregrov, A., El-Hage, W., Ford, J. D., Haagsma, J. A., Javakhishvili, J. D., Kassam-Adams, N., Kristensen, C. H., Langevin, R., Lanza, J. A., Lueger-Schuster, B., Manickam, L. S., Marengo, D., Mello, M. F., Nickerson, A., Oe, M., Heval Ozgen, M., Rabellino, D., Sales, L., Salgado, C., Schellong, J., Schnyder, U., Seedat, S., Semenova, N. B., Smith, A. J., Sobczak, S., June ter Heide, J., Vazquez, C., Videira Pinto, J., Wagner, A. C., Wang, L., Zrnic, I., Adult Psychiatry, APH - Global Health, APH - Mental Health, ANS - Mood, Anxiety, Psychosis, Stress & Sleep, Graduate School, ANS - Amsterdam Neuroscience, University of Zurich, and Olff, Miranda

Subjects
050103 clinical psychology, salud mental global, insomnia, depresión, RC435-571, 失眠, 2738 Psychiatry and Mental Health, 0302 clinical medicine, Psychiatric history, anxiety, COVID-19, depression, dissociation, global mental health, PTSD, public health, risk factors, screening, 全球心理健康, insomnio, Medicine, Depression (differential diagnoses), media_common, General Environmental Science, Psychiatry, 05 social sciences, 焦虑, 筛查, Anxiety, Psychological resilience, medicine.symptom, Research Article, trastorno de estrés postraumático, medicine.medical_specialty, tamizaje, media_common.quotation_subject, 抑郁, 610 Medicine & health, 03 medical and health sciences, Social support, salud pública, SDG 3 - Good Health and Well-being, disociación, 解离, factores de riesgo, 0501 psychology and cognitive sciences, Basic Research Article, 风险因素, business.industry, Public health, Stressor, ansiedad, Mental health, 030227 psychiatry, 10057 Klinik für Konsiliarpsychiatrie und Psychosomatik, 公共卫生, General Earth and Planetary Sciences, business
Abstract

Background: The mental health impact of the COVID-19 crisis may differ from previously studied stressful events in terms of psychological reactions, specific risk factors, and symptom severity across geographic regions worldwide. Objective: To assess the impact of COVID-19 on a wide range of mental health symptoms, to identify relevant risk factors, to identify the effect of COVID-19 country impact on mental health, and to evaluate regional differences in psychological responses to COVID-19 compared to other stressful events. Method: 7034 respondents (74% female) participated in the worldwide Global Psychotrauma Screen – Cross-Cultural responses to COVID-19 study (GPS-CCC), reporting on mental health symptoms related to COVID-19 (n = 1838) or other stressful events (n = 5196) from April to November 2020. Results: Events related to COVID-19 were associated with more mental health symptoms compared to other stressful events, especially symptoms of PTSD, anxiety, depression, insomnia, and dissociation. Lack of social support, psychiatric history, childhood trauma, additional stressful events in the past month, and low resilience predicted more mental health problems for COVID-19 and other stressful events. Higher COVID-19 country impact was associated with increased mental health impact of both COVID-19 and other stressful events. Analysis of differences across geographic regions revealed that in Latin America more mental health symptoms were reported for COVID-19 related events versus other stressful events, while the opposite pattern was seen in North America. Conclusions: The mental health impact of COVID-19-related stressors covers a wide range of symptoms and is more severe than that of other stressful events. This difference was especially apparent in Latin America. The findings underscore the need for global screening for a wide range of mental health problems as part of a public health approach, allowing for targeted prevention and intervention programs., HIGHLIGHTS In a large global sample, COVID-19 was associated with more severe mental health symptoms compared to other stressful or traumatic events. The impact of COVID-19 on mental health differed around the world with an especially large impact in Latin America.

Published
2021

14. A STUDY OF CLERICS WHO COMMIT SEXUAL OFFENSES: ARE THEY DIFFERENT FROM OTHER SEX OFFENDERS?

Author

Langevin, R., Curnoe, S., and Bain, J.

Subjects
Clergy -- Psychological aspects, Sex offenders -- Psychological aspects, Child sexual abusers -- Psychological aspects, Family and marriage, Sociology and social work
Abstract

Objective: The goal of this study was to determine if cleric-sex offenders differed significantly from other sex offenders when compared to a control group and assessed with standard instruments that examine the major factors important in sexual offenses. Method: Twenty-four male clerics accused of sexual offenses were compared to 24 male sex offender controls, matched on offense type, age, education, and marital status. Both groups were compared to a general sample of sex offenders (n = 2125) matched only for offense type. The three groups were compared on sexual history and preference, substance abuse, mental illness and personality, history of crime and violence, neuropsychological impairment, and endocrine abnormalities, using reliable and valid measures. Results: The clerics in this study formed a statistically significant highly educated, older, and predominantly single subgroup of sex offenders. The majority of cleric-sex offenders suffered from a sexual disorder (70.8%), predominantly homosexual pedophilia, as measured by phallometric testing, but did not differ from the control groups in this respect. The clerics were comparable to the other two groups in most respects, but tended to show less antisocial personality disorders and somewhat more endocrine disorders. The most noteworthy features differentiating the clerics from highly educated matched controls were that clerics had a longer delay before criminal charges were laid, or lacked criminal charges altogether, and they tended to use force more often in their offenses. Conclusions: In spite of differences in age, education, and occupation between cleric-sex offenders and sex offenders in general, the same procedures should be used in the assessment of this group as for the sex offender population in general. Hypotheses about reduced sexual outlet and increased sexual abuse of clerics in childhood were not supported. Assessment and treatment of cleric-sex offenders should focus especially on sexual deviance, substance abuse, and endocrine disorders.

Published
2000

16. Abstracts from the sixth meeting of the international association of pancreatology, November 2–4, 1994, Chicago, IL

Author

Burdick, Michael, Hollingsworth, Tony, Gansauge, S., Gansauge, F., Link, K. H., Schoenberg, M. H., Poch, B., Beger, H. G., Wagner, A. C. C., Steffen, H., Göke, B., Gaisano, H. Y., Sheu, L., Foskett, J. K., Trimble, W. S., Lee, Y. L., Kwon, H. Y., Park, H. S., Lee, S. M., Park, H. J., aguchi, S., Green, G. M., Mitamura, K., Komatsu, Y., Arai, I., Yamaura, H., Wang, OJ, Adrian, TE, Teyssen, S., Niebel, W., Niebergall, E., Singer, M. V., Umehara, K, Ohara, T, Kataoka, K, Okamura, H, Kato, M, Sakagami, J, Ohta, A, Murase, M, Hosoda, M, Yamane, Y, Kashima, K, Ibata, Y, Balthazar, Emil J., Banks, P. A., Garzof, S. G., Langevin, R. E., Silverman, S. G., Sica, G. T., Bassi, C., Benini, A., Muner, A., Falconi, M., Abbas, H., Pederzoli, P., Salvia, R., Minelli, E. Bertazzoni, Shaskar, S. Shanmuga, Shearer, M. G., Imrie, C. W., Brodmerkel, G. J., Reed, P. A., Carr-Locke, DL, Musa, A, Lichtenstein, DR, Dam, J Van, Banks, PA, Eisele, S., Schoenberg, M. H., Böchjer, M., Beger, H. G., Foitzik, Th., Fern’andez-del Castillo, C., Rattner, D. W., Ferraro, M. J., Warshaw, A. L., Foitzik, Th., Schmidt, J., Hotz, H., Warshaw, A. L., Buhr, H. J., Klar, E., Heinisch, A., Kadow, R., Bioss, U., Schölmerich, J., Zimgibl, H., Leser, H. -G., Manes, G., Rabitti, P. G., Laccetti, M., Cavallera, A., Paceili, L., Gagiione, G., Uomo, G., Marinqhini, A., Zinsmeister, A. R., Melton, L. J., DiMagno, E. P., Marotta, F., Chui, D. H., Barbi, G., Zhong, G. G., Marotta, F., Chui, D. H., Tajiri, H., Bellini, O., Zhong, G. G., Barbi, G., McKay, C, Baxter, J. N., Imrie, C. W., Mithöfer, K., Fern’andez-delCastillo, C., Frick, T. W., Lewandrowski, K., Rattner, D. W., Warshaw, A. L., Pezzilli, R., Billi, P., Miniero, R., Gullo, L., Barakat, B., Migliuli, M., Rau, B., Schad, M., Schoenberg, M., Beger, H. G., Richter, F., Matthias, R., Sakagami, J, Kataoka, K, Ohta, A, Umehara, K, Imoto, M, Murase, M, Hosoda, M, Yamane, Y, Kato, M, Kashima, K, Ashihara, T, Schofield, D, Sharer, NM, Heywood, KM, Waters, HM, Braganza, JM, Scott, P, Sharer, NM, Bilton, D, Deardon, D, Lee, S, Taylor, PM, McCloy, RF, Braganza, JM, Shen, J., Shao, H., Wu, Z. P., Jin, J. J., Shiel, N, Cassidy, O, Sharma, H, Braganza, J. M., Soöckmann, F., Ahrens, J., Leonhardt, U., Otto, J., Ritzel, U., Ramadori, G., Tian, Fuzhou, Hu, JZ, Huang, DR, Wang, XH, Lian, HW, Zhang, BY, Miao, JG, Li, Xu, Zhou, HT, Uomo, G., Rabitti, P. G., Laccetti, M., Manes, G., Esposico, P., Perrocti, F., Visconci, M., Vaccaro, M. I., Dagrosa, M. A., Mora, M. I., Sordelli, D. O., Vogt, W., MeOmann, H., Heinisch, A., Linseis, A., Holstege, A., Schölmerich, J., Leser, H. -G., Weiser, M. R., Gibbs, S. A. L., Hechcman, H. B., Moore, F. D., Worthington, H. V., Runt, L. P., HcCloy, R. F., KacLennan, I. A., Braqanza, J. M., Heath, D, Alexander, D, Wilson, C, Larvin, M, Imrie, CW, McMahon, MJ, Larvin, M, Ward, J, Robinson, PJ, Chalmers, AG, McMahon, MJ, Apte, M, Wilson, J, McCaughan, G, Korsten, M, Norton, I, Piroia, R, Bimmler, D., Frick, T. W., Scheele, G. A., Bockman, Dale E., Büchler, Markus, Beger, Hans G., Cavallini, G., Brunori, M. P., Rigo, L., Bovo, P., Filippini, M., Vaona, B., Di Francesco, V., Frulloni, L., Marcori, M., Farri, P. C., Laardini, M. T., Pederzoli, P., Chowdhury, Riaz, Ochi, Koji, Mizushima, Takaaki, Tsurumi, Tetsuya, Harada, Hideo, Laver, P., Hoist, J. J., Ohe, M. v. d., Goebell, H., Mi Zumoto, A., Sarr, M. G., DiMagno, E. P., Moore, R., Frey, C. F., Debas, H. T., Mulvihill, S. J., Onizuka, S., Kuroda, H., Kuroda, Y., Hongo, H., Matsuzaki, S., Ito, M., Sekine, L., Tsunoda, T., Pap, ’A., Hrisztov, V., Pap, ’A., Marosi, E., Simon, K., Tak’acs, T., Pederzoli, P., Falconi, M., Bassi, C., Bonora, A., Talamini, G., Saivia, R., Benini, L., Caldiron, E., Vesentini, S., Cavallini, G., Raijman, Isaac, Kortan, Paul, Haber, Gregory B., Ramesh, H, Varghese, CJ, Schofield, D, Kay, PM, Bottiglieri, T, Uden, S, Bilton, D, Braganza, JM, Gut, A, Segal, I, Snehalatha, C, Mohan, V, Braganza, JM, Silva, E., Ceneviva, R., Velludo, M. A. L., Silvan, E., Ruebner, B., Ceneviva, R., Velludo, M. A. L., Roselino, J. E. S., Foss, M. C., Talaraini, G., Falcaoi, M., Frmlltai, L, K Fraacesca, V., Maxwi, M., Vaosa, B., Baro, P., Baxu, C., Pedercoli, P., Cavalliai, G., Taiamini, G., Iacano, C., Faicsai, M., Frulloni, L., Rige, L., Castagnisi, A., Marcori, M., Angelini, G., Bassi, C., Bom, P., Vaoss, B., Vantini, I., Sen, G., Pederzali, P., Cavallini, G., Štimee, B, Bulajič, M, Milosavljevi’c, T, Krsti’c, R, Markovi’c, M, Korneti, V, Ugljcš’c, M, Abruzzesse, IL, Evans, DB, Larry, L, King, T, Raijman, I, Roubein, L, Frazier, M, lacono, C., Faca, E., Falezza, G., Bonora, E., Aurola PP, Serio, G., lacono, C., Nicoli, N., Mansueto, G. C., Zicari, M., Marchiori, L., Mangiante, G., Seno, G., Imarnura, M., Yamauchi, H., Inoue, M., Onda, M., UchlDa, E., Almqtq, T., Yamanaka, Y., Kqbayashi, T., Yokqyama, T., Aida, K., Sasajima, K., Tajiri, T., Egami, K., Yamashita, K., Naitq, Z., Asano, G., Lewandrowski, K. B., Kirby, R. E., Southern, J. F., Compton, C. C., Warshaw, A. L., Lip, J, Strömmer, L, Permert, J, Larsson, J, Adrian, TE, Loftus, E. V., Adkins, M. C., Olivares-Pakzad, B., Batts, K. P., Stephens, D. H., Farnell, M. B., Sarr, H. G., Thompson, G. B., van Heerden, J. A., Kelly, D. G., Miller, L. J., Pearson, R. K., Clain, J. E., Petersen, B. T., DiMagno, E. P., Matsumoto, Cancer S., Chowdhury, R., Mizushima, T., Ochi, K., Harada, H., Miki, H., Ozkan, Hnsan, Saisho, Hiromitsu, Yarnaguchi, Taketo, Ishihara, Takeshi, Kikuchi, Yasuharu, Tsuyuguchi, Toshio, Ohto, Masao, Pasqual, C., Sperti, C., Liesai, G., Guido, M., Pedrazzoli, S., Sperti, C., Pasquali, C., Khajeturian, E., Guolo, P., Pedrazzoli, S., Tadokoro, H., Watanabe, S., Moriyoshi, Y., Yoshida, K., Shiratori, K., Takeuchi, T., Uchida, E., Onda, M., Tajiri, T., Egami, K., Yamashita, K., Aida, K., Yamanaka, Y., Kobayashi, T., Aimoto, T., Yokoyama, T., Inoue, M., Naito, Z., Asano, G., Valentich, M. A., Monis, B., Barotto, N. N., and Herrera, P.

Published
1994
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25. The Minkowski-Lorentz space for Computer Aided Design purposes

Author

Becar, Jean-Paul, Garnier, L., Druoton, L, Langevin, R, Fuchs, L, Morin, G., Laboratoire de Mathématiques et leurs Applications de Valenciennes - EA 4015 (LAMAV), Université de Valenciennes et du Hainaut-Cambrésis (UVHC)-Centre National de la Recherche Scientifique (CNRS)-INSA Institut National des Sciences Appliquées Hauts-de-France (INSA Hauts-De-France), BECAR, JEAN-PAUL, Centre National de la Recherche Scientifique (CNRS)-Université Polytechnique Hauts-de-France (UPHF)-Université Polytechnique Hauts-de-France (UPHF), Institut de minéralogie et de physique des milieux condensés (IMPMC), and Université Pierre et Marie Curie - Paris 6 (UPMC)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[MATH] Mathematics [math], [MATH.MATH-MG] Mathematics [math]/Metric Geometry [math.MG], [MATH]Mathematics [math], [MATH.MATH-MG]Mathematics [math]/Metric Geometry [math.MG]
Abstract

International audience; This document deals with the Computer Aided Geometric Design with a short presentation of the Minkowski-Lorentz space. This space generalizes to R 5 the one used in the relativity theory. The Minkowski-Lorentz space oers a more intuitive writing of a sphere given by a point, a normal vector at the point and its curvature. It also eases the use of canal surfaces thus represented by curves. The quadratic computation in R 3 becomes linear in that space. The use of spheres, canal surfaces and their particular case known as Dupin cyclides is illustrated in a schematic seahorse. The seahorse applies the G 1 connection in the Minkowski-Lorentz space. Oriented spheres and Pencils An oriented sphere S with centre Ω and radius r > 0 satises the relationship − − → ΩM = ρ − → N with the rule ρ = r (resp. ρ = −r) if the unit normal vector − → N to the sphere at point M is getting outside (resp. inside). The power of the point M to the sphere S is dened by χ S (M) = ΩM 2 − ρ 2. The set of points solution of λ 1 χ S 1 (M) + λ 2 χ S 2 (M) = 0 is called the spheres pencil dened by S 1 et S 2 .

Published
2016

27. Espace de Minkowski-Lorentz et des sphères : un état de l’art

Author

Becar, Jean-Paul, Druoton, Lucie, Fuchs, L., Garnier, L., Langevin, R., Morin, Géraldine, Laboratoire de Mathématiques et leurs Applications de Valenciennes - EA 4015 (LAMAV), and Université de Valenciennes et du Hainaut-Cambrésis (UVHC)-Centre National de la Recherche Scientifique (CNRS)-INSA Institut National des Sciences Appliquées Hauts-de-France (INSA Hauts-De-France)

Subjects
[MATH]Mathematics [math], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2016

28. Dynamics and the Godbillon-Vey Class of C^1 Foliations

Author

Hurder, Steven and Langevin, R��mi

Subjects
Mathematics::Dynamical Systems, Differential Geometry (math.DG), Mathematics::K-Theory and Homology, FOS: Mathematics, Mathematics::Differential Geometry, 57R30, 58H10, 37C40
Abstract

Let F be a codimension-one, C^2-foliation on a manifold M without boundary. In this work we show that if the Godbillon--Vey class GV(F) \in H^3(M) is non-zero, then F has a hyperbolic resilient leaf. Our approach is based on methods of C^1-dynamical systems, and does not use the classification theory of C^2-foliations. We first prove that for a codimension--one C^1-foliation with non-trivial Godbillon measure, the set of infinitesimally expanding points E(F) has positive Lebesgue measure. We then prove that if E(F) has positive measure for a C^1-foliation F, then F must have a hyperbolic resilient leaf, and hence its geometric entropy must be positive. The proof of this uses a pseudogroup version of the Pliss Lemma. The theorem then follows, as a C^2-foliation with non-zero Godbillon-Vey class has non-trivial Godbillon measure. These results apply for both the case when M is compact, and when M is an open manifold., This manuscript is a revision of the section 3 material from the previous version, and includes edits to the pictures in the text

Published
2014
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48. The geometry of canal surfaces and the length of curves in de Sitter space

Author

Langevin, R��mi and Solanes, Gil

Subjects
Differential Geometry (math.DG), FOS: Mathematics
Abstract

We find the minimal value of the length in de Sitter space of closed space-like curves with non-vanishing non-space-like geodesic curvature vector. These curves are in correspondence with closed almost-regular canal surfaces, and their length is a natural magnitude in conformal geometry. As an application, we get a lower bound for the total conformal torsion of closed space curves.

Published
2011
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