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1. Softening Mechanism of Coherent Phonons in Antimony Under High Density Photoexcitation

Author

Kumagai, H., Matsubara, I., Nakahara, J., and Mishina, T.

Subjects
Condensed Matter - Materials Science
Abstract

We have investigated the dynamical properties of coherent phonons generated in antimony under high density photo excitation. Precise measurements and extended analysis of coherent phonon oscillations provide new insights into the process of impulsive softening. In the process of recovering from instantaneous softening, phonon frequency shows an unexpected temporal evolution involving an abrupt change and a slight overshoot. Moreover, fluence dependence of the initial phonon frequency is strongly correlated with the phonon frequency shift of the high-pressure Raman spectra. These results clearly prove that the structural changes (lattice contraction and expansion) induced by laser excitation governs the softening mechanism of coherent phonons., Comment: 10 pages, 5 figures

Published
2016

2. Safety and efficacy of eculizumab in Guillain-Barré syndrome: a multicentre, double-blind, randomised phase 2 trial

Author

Misawa, S, Kuwabara, S, Sato, Y, Yamaguchi, N, Nagashima, K, Katayama, K, Sekiguchi, Y, Iwai, Y, Amino, H, Suichi, T, Yokota, T, Nishida, Y, Kanouchi, T, Kohara, N, Kawamoto, M, Ishii, J, Kuwahara, M, Suzuki, H, Hirata, K, Kokubun, N, Masuda, R, Kaneko, J, Yabe, I, Sasaki, H, Kaida, K, Takazaki, H, Suzuki, N, Suzuki, S, Nodera, H, Matsui, N, Tsuji, S, Koike, H, Yamasaki, R, Kusunoki, S, Nagashima, T, Shimizu, T, Hirotani, M, Kadoya, M, Nakahara, J, Shimizu, J, Tanaka, M, Sobue, G, Katsuno, M, Yamaguchi, H, Ogata, H, Misawa, Sonoko, Kuwabara, Satoshi, Sato, Yasunori, Yamaguchi, Nobuko, Nagashima, Kengo, Katayama, Kanako, Sekiguchi, Yukari, Iwai, Yuta, Amino, Hiroshi, Suichi, Tomoki, Yokota, Takanori, Nishida, Yoichiro, Kanouchi, Tadashi, Kohara, Nobuo, Kawamoto, Michi, Ishii, Junko, Kuwahara, Motoi, Suzuki, Hidekazu, Hirata, Koichi, Kokubun, Norito, Masuda, Ray, Kaneko, Juntaro, Yabe, Ichiro, Sasaki, Hidenao, Kaida, Ken-ichi, Takazaki, Hiroshi, Suzuki, Norihiro, Suzuki, Shigeaki, Nodera, Hiroyuki, Matsui, Naoko, Tsuji, Shoji, Koike, Haruki, Yamasaki, Ryo, and Kusunoki, Susumu

Published
2018
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8. Safety of tapering tacrolimus dose in patients with well‐controlled anti‐acetylcholine receptor antibody‐positive myasthenia gravis

Author

Nishida, Y., primary, Takahashi, Y. K., additional, Kanai, T., additional, Nose, Y., additional, Ishibashi, S., additional, Sanjo, N., additional, Uzawa, A., additional, Oda, F., additional, Ozawa, Y., additional, Kuwabara, S., additional, Noguchi, E., additional, Suzuki, S., additional, Nakahara, J., additional, Suzuki, N., additional, Ogawa, T., additional, Yokoyama, K., additional, Hattori, N., additional, Konno, S., additional, Fujioka, T., additional, Kawaguchi, N., additional, Hatanaka, Y., additional, Sonoo, M., additional, Kaneko, J., additional, Ogino, M., additional, Nishiyama, K., additional, Nomura, K., additional, and Yokota, T., additional

Published
2019
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9. Siponimod versus placebo in secondary progressive multiple sclerosis (EXPAND): a double-blind, randomised, phase 3 study

Author

Kappos, L., Bar-Or, A., Cree, B. A. C., Fox, R. J., Giovannoni, G., Gold, R., Vermersch, P., Arnold, D. L., Arnould, S., Scherz, T., Wolf, C., Wallstrom, E., Dahlke, F., Achiron, A., Achtnichts, L., Agan, K., Akman-Demir, G., Allen, A. B., Antel, J. P., Antiguedad, A. R., Apperson, M., Applebee, A. M., Ayuso, G. I., Baba, M., Bajenaru, O., Balasa, R., Balci, B. P., Barnett, M., Bass, A., Becker, V. U., Bejinariu, M., Bergh, F. T., Bergmann, A., Bernitsas, E., Berthele, A., Bhan, V., Bischof, F., Bjork, R. J., Blevins, G., Boehringer, M., Boerner, T., Bonek, R., Bowen, J. D., Bowling, A., Boyko, A. N., Boz, C., Bracknies, V., Braune, S., Brescia Morra, V., Brochet, B., Brola, W., Brownstone, P. K., Brozman, M., Brunet, D., Buraga, I., Burnett, M., Buttmann, M., Butzkueven, H., Cahill, J., Calkwood, J. C., Camu, W., Cascione, M., Castelnovo, G., Centonze, D., Cerqueira, J., Chan, A., Cimprichova, A., Cohan, S., Comi, G., Conway, J., Cooper, J. A., Corboy, J., Correale, J., Costell, B., Cottrell, D. A., Coyle, P. K., Craner, M., Cui, L., Cunha, L., Czlonkowska, A., da Silva, A. M., de Sa, J., de Seze, J., Debouverie, M., Debruyne, J., Decoo, D., Defer, G., Derfuss, T., Deri, N. H., Dihenia, B., Dioszeghy, P., Donath, V., Dubois, B., Duddy, M., Duquette, P., Edan, G., Efendi, H., Elias, S., Emrich, P. J., Estruch, B. C., Evdoshenko, E. P., Faiss, J., Fedyanin, A. S., Feneberg, W., Fermont, J., Fernandez, O. F., Ferrer, F. C., Fink, K., Ford, H., Ford, C., Francia, A., Freedman, M., Frishberg, B., Galgani, S., Garmany, G. P., Gehring, K., Gitt, J., Gobbi, C., Goldstick, L. P., Gonzalez, R. A., Grandmaison, F., Grigoriadis, N., Grigorova, O., Grimaldi, L. M. E., Gross, J., Gross-Paju, K., Gudesblatt, M., Guillaume, D., Haas, J., Hancinova, V., Hancu, A., Hardiman, O., Harmjanz, A., Heidenreich, F. R., Hengstman, G. J. D., Herbert, J., Herring, M., Hodgkinson, S., Hoffmann, O. M., Hofmann, W. E., Honeycutt, W. D., Hua, L. H., Huang, D., Huang, Y., Hupperts, R., Imre, P., Jacobs, A. K., Jakab, G., Jasinska, E., Kaida, K., Kalnina, J., Kaprelyan, A., Karelis, G., Karussis, D., Katz, A., Khabirov, F. A., Khatri, B., Kimura, T., Kister, I., Kizlaitiene, R., Klimova, E., Koehler, J., Komatineni, A., Kornhuber, A., Kovacs, K., Koves, A., Kozubski, W., Krastev, G., Krupp, L. B., Kurca, E., Lassek, C., Laureys, G., Lee, L., Lensch, E., Leutmezer, F., Li, H., Linker, R. A., Linnebank, M., Liskova, P., Llanera, C., Lu, J., Lutterotti, A., Lycke, J., Macdonell, R., Maciejowski, M., Maeurer, M., Magzhanov, R. V., Maida, E. -M., Malciene, L., Mao-Draayer, Y., Marfia, G. A., Markowitz, C., Mastorodimos, V., Matyas, K., Meca-Lallana, J., Merino, J. A. G., Mihetiu, I. G., Milanov, I., Miller, A. E., Millers, A., Mirabella, M., Mizuno, M., Montalban, X., Montoya, L., Mori, M., Mueller, S., Nakahara, J., Nakatsuji, Y., Newsome, S., Nicholas, R., Nielsen, A. S., Nikfekr, E., Nocentini, U., Nohara, C., Nomura, K., Odinak, M. M., Olsson, T., van Oosten, B. W., Oreja-Guevara, C., Oschmann, P., Overell, J., Pachner, A., Panczel, G., Pandolfo, M., Papeix, C., Patrucco, L., Pelletier, J., Piedrabuena, R., Pless, M., Polzer, U., Pozsegovits, K., Rastenyte, D., Rauer, S., Reifschneider, G., Rey, R., Rizvi, S. A., Robertson, D., Rodriguez, J. M., Rog, D., Roshanisefat, H., Rowe, V., Rozsa, C., Rubin, S., Rusek, S., Sacca, F., Saida, T., Salgado, A. V., Sanchez, V. E. F., Sanders, K., Satori, M., Sazonov, D. V., Scarpini, E. A., Schlegel, E., Schluep, M., Schmidt, S., Scholz, E., Schrijver, H. M., Schwab, M., Schwartz, R., Scott, J., Selmaj, K., Shafer, S., Sharrack, B., Shchukin, I. A., Shimizu, Y., Shotekov, P., Siever, A., Sigel, K. -O., Silliman, S., Simo, M., Simu, M., Sinay, V., Siquier, A. E., Siva, A., Skoda, O., Solomon, A., Stangel, M., Stefoski, D., Steingo, B., Stolyarov, I. D., Stourac, P., Strassburger-Krogias, K., Strauss, E., Stuve, O., Tarnev, I., Tavernarakis, A., Tello, C. R., Terzi, M., Ticha, V., Ticmeanu, M., Tiel-Wilck, K., Toomsoo, T., Tubridy, N., Tullman, M. J., Tumani, H., Turcani, P., Turner, B., Uccelli, A., Urtaza, F. J. O., Vachova, M., Valikovics, A., Walter, S., Van Wijmeersch, B., Vanopdenbosch, L., Weber, J. R., Weiss, S., Weissert, R., West, T., Wiendl, H., Wiertlewski, S., Wildemann, B., Willekens, B., Visser, L. H., Vorobeychik, G., Xu, X., Yamamura, T., Yang, Y. N., Yelamos, S. M., Yeung, M., Zacharias, A., Zelkowitz, M., Zettl, U., Zhang, M., Zhou, H., Zieman, U., Ziemssen, T., Bergmann A., Haas J., Mirabella M. (ORCID:0000-0002-7783-114X), Terzi M., Kappos, L., Bar-Or, A., Cree, B. A. C., Fox, R. J., Giovannoni, G., Gold, R., Vermersch, P., Arnold, D. L., Arnould, S., Scherz, T., Wolf, C., Wallstrom, E., Dahlke, F., Achiron, A., Achtnichts, L., Agan, K., Akman-Demir, G., Allen, A. B., Antel, J. P., Antiguedad, A. R., Apperson, M., Applebee, A. M., Ayuso, G. I., Baba, M., Bajenaru, O., Balasa, R., Balci, B. P., Barnett, M., Bass, A., Becker, V. U., Bejinariu, M., Bergh, F. T., Bergmann, A., Bernitsas, E., Berthele, A., Bhan, V., Bischof, F., Bjork, R. J., Blevins, G., Boehringer, M., Boerner, T., Bonek, R., Bowen, J. D., Bowling, A., Boyko, A. N., Boz, C., Bracknies, V., Braune, S., Brescia Morra, V., Brochet, B., Brola, W., Brownstone, P. K., Brozman, M., Brunet, D., Buraga, I., Burnett, M., Buttmann, M., Butzkueven, H., Cahill, J., Calkwood, J. C., Camu, W., Cascione, M., Castelnovo, G., Centonze, D., Cerqueira, J., Chan, A., Cimprichova, A., Cohan, S., Comi, G., Conway, J., Cooper, J. A., Corboy, J., Correale, J., Costell, B., Cottrell, D. A., Coyle, P. K., Craner, M., Cui, L., Cunha, L., Czlonkowska, A., da Silva, A. M., de Sa, J., de Seze, J., Debouverie, M., Debruyne, J., Decoo, D., Defer, G., Derfuss, T., Deri, N. H., Dihenia, B., Dioszeghy, P., Donath, V., Dubois, B., Duddy, M., Duquette, P., Edan, G., Efendi, H., Elias, S., Emrich, P. J., Estruch, B. C., Evdoshenko, E. P., Faiss, J., Fedyanin, A. S., Feneberg, W., Fermont, J., Fernandez, O. F., Ferrer, F. C., Fink, K., Ford, H., Ford, C., Francia, A., Freedman, M., Frishberg, B., Galgani, S., Garmany, G. P., Gehring, K., Gitt, J., Gobbi, C., Goldstick, L. P., Gonzalez, R. A., Grandmaison, F., Grigoriadis, N., Grigorova, O., Grimaldi, L. M. E., Gross, J., Gross-Paju, K., Gudesblatt, M., Guillaume, D., Haas, J., Hancinova, V., Hancu, A., Hardiman, O., Harmjanz, A., Heidenreich, F. R., Hengstman, G. J. D., Herbert, J., Herring, M., Hodgkinson, S., Hoffmann, O. M., Hofmann, W. E., Honeycutt, W. D., Hua, L. H., Huang, D., Huang, Y., Hupperts, R., Imre, P., Jacobs, A. K., Jakab, G., Jasinska, E., Kaida, K., Kalnina, J., Kaprelyan, A., Karelis, G., Karussis, D., Katz, A., Khabirov, F. A., Khatri, B., Kimura, T., Kister, I., Kizlaitiene, R., Klimova, E., Koehler, J., Komatineni, A., Kornhuber, A., Kovacs, K., Koves, A., Kozubski, W., Krastev, G., Krupp, L. B., Kurca, E., Lassek, C., Laureys, G., Lee, L., Lensch, E., Leutmezer, F., Li, H., Linker, R. A., Linnebank, M., Liskova, P., Llanera, C., Lu, J., Lutterotti, A., Lycke, J., Macdonell, R., Maciejowski, M., Maeurer, M., Magzhanov, R. V., Maida, E. -M., Malciene, L., Mao-Draayer, Y., Marfia, G. A., Markowitz, C., Mastorodimos, V., Matyas, K., Meca-Lallana, J., Merino, J. A. G., Mihetiu, I. G., Milanov, I., Miller, A. E., Millers, A., Mirabella, M., Mizuno, M., Montalban, X., Montoya, L., Mori, M., Mueller, S., Nakahara, J., Nakatsuji, Y., Newsome, S., Nicholas, R., Nielsen, A. S., Nikfekr, E., Nocentini, U., Nohara, C., Nomura, K., Odinak, M. M., Olsson, T., van Oosten, B. W., Oreja-Guevara, C., Oschmann, P., Overell, J., Pachner, A., Panczel, G., Pandolfo, M., Papeix, C., Patrucco, L., Pelletier, J., Piedrabuena, R., Pless, M., Polzer, U., Pozsegovits, K., Rastenyte, D., Rauer, S., Reifschneider, G., Rey, R., Rizvi, S. A., Robertson, D., Rodriguez, J. M., Rog, D., Roshanisefat, H., Rowe, V., Rozsa, C., Rubin, S., Rusek, S., Sacca, F., Saida, T., Salgado, A. V., Sanchez, V. E. F., Sanders, K., Satori, M., Sazonov, D. V., Scarpini, E. A., Schlegel, E., Schluep, M., Schmidt, S., Scholz, E., Schrijver, H. M., Schwab, M., Schwartz, R., Scott, J., Selmaj, K., Shafer, S., Sharrack, B., Shchukin, I. A., Shimizu, Y., Shotekov, P., Siever, A., Sigel, K. -O., Silliman, S., Simo, M., Simu, M., Sinay, V., Siquier, A. E., Siva, A., Skoda, O., Solomon, A., Stangel, M., Stefoski, D., Steingo, B., Stolyarov, I. D., Stourac, P., Strassburger-Krogias, K., Strauss, E., Stuve, O., Tarnev, I., Tavernarakis, A., Tello, C. R., Terzi, M., Ticha, V., Ticmeanu, M., Tiel-Wilck, K., Toomsoo, T., Tubridy, N., Tullman, M. J., Tumani, H., Turcani, P., Turner, B., Uccelli, A., Urtaza, F. J. O., Vachova, M., Valikovics, A., Walter, S., Van Wijmeersch, B., Vanopdenbosch, L., Weber, J. R., Weiss, S., Weissert, R., West, T., Wiendl, H., Wiertlewski, S., Wildemann, B., Willekens, B., Visser, L. H., Vorobeychik, G., Xu, X., Yamamura, T., Yang, Y. N., Yelamos, S. M., Yeung, M., Zacharias, A., Zelkowitz, M., Zettl, U., Zhang, M., Zhou, H., Zieman, U., Ziemssen, T., Bergmann A., Haas J., Mirabella M. (ORCID:0000-0002-7783-114X), and Terzi M.

Abstract

Background: No treatment has consistently shown efficacy in slowing disability progression in patients with secondary progressive multiple sclerosis (SPMS). We assessed the effect of siponimod, a selective sphingosine 1-phosphate (S1P) receptor1,5 modulator, on disability progression in patients with SPMS. Methods: This event-driven and exposure-driven, double-blind, phase 3 trial was done at 292 hospital clinics and specialised multiple sclerosis centres in 31 countries. Using interactive response technology to assign numbers linked to treatment arms, patients (age 18–60 years) with SPMS and an Expanded Disability Status Scale score of 3·0–6·5 were randomly assigned (2:1) to once daily oral siponimod 2 mg or placebo for up to 3 years or until the occurrence of a prespecified number of confirmed disability progression (CDP) events. The primary endpoint was time to 3-month CDP. Efficacy was assessed for the full analysis set (ie, all randomly assigned and treated patients); safety was assessed for the safety set. This trial is registered with ClinicalTrials.gov, number NCT01665144. Findings: 1651 patients were randomly assigned between Feb 5, 2013, and June 2, 2015 (1105 to the siponimod group, and 546 to the placebo group). One patient did not sign the consent form, and five patients did not receive study drug, all of whom were in the siponimod group. 1645 patients were included in the analyses (1099 in the siponimod group and 546 in the placebo). At baseline, the mean time since first multiple sclerosis symptoms was 16·8 years (SD 8·3), and the mean time since conversion to SPMS was 3·8 years (SD 3·5); 1055 (64%) patients had not relapsed in the previous 2 years, and 918 (56%) of 1651 needed walking assistance. 903 (82%) patients receiving siponimod and 424 (78%) patients receiving placebo completed the study. 288 (26%) of 1096 patients receiving siponimod and 173 (32%) of 545 patients receiving placebo had 3-month CDP (hazard ratio 0·79, 95% CI 0·65–0·95; relative

Published
2018

13. Safety of tapering tacrolimus dose in patients with well‐controlled anti‐acetylcholine receptor antibody‐positive myasthenia gravis.

Author

Nishida, Y., Takahashi, Y. K., Kanai, T., Nose, Y., Ishibashi, S., Sanjo, N., Uzawa, A., Oda, F., Ozawa, Y., Kuwabara, S., Noguchi, E., Suzuki, S., Nakahara, J., Suzuki, N., Ogawa, T., Yokoyama, K., Hattori, N., Konno, S., Fujioka, T., and Kawaguchi, N.

Subjects
MYASTHENIA gravis, AGE of onset, TACROLIMUS
Abstract

Background and purpose: Tapering immunosuppressants is desirable in patients with well‐controlled myasthenia gravis (MG). However, the association between tapering of calcineurin inhibitor dosage and reduction‐associated exacerbation is not known. The aim of this study was to clarify the frequency of reduction‐associated exacerbation when tacrolimus is tapered in stable patients with anti‐acetylcholine receptor antibody‐positive MG, and to determine the factors that predict exacerbations. Methods: We retrospectively analyzed 115 patients in whom tacrolimus dosage was tapered. The reduction‐associated exacerbation was defined as the appearance or worsening of one or more MG symptoms <3 months after the reduction. Results: Tacrolimus dosage was successfully tapered in 110 patients (96%) without any exacerbation. Five patients (4%) experienced an exacerbation, but symptoms were reversed in all patients when the tacrolimus dose was increased to the previous maintenance level. No patient developed an MG crisis. The age at onset was significantly earlier (30 vs. 56 years, P = 0.025) and the reduction in dosage was significantly larger (2.0 vs. 1.0 mg/day, P = 0.002) in patients with reduction‐associated exacerbation than in those without exacerbation. The cut‐off values determined in a receiver‐operating characteristic curve analysis were 52 years (sensitivity, 57%; specificity, 100%) for the age at onset and 1.5 mg (sensitivity, 80%; specificity, 100%) for the dose reduction. Conclusion: Tapering of tacrolimus was possible in most patients with well‐controlled anti‐acetylcholine receptor antibody‐positive MG. Early age at onset and a large reduction from maintenance dosage were associated with exacerbation. Reductions ≤1.5 mg/day from the maintenance dosage should be considered for patients with late‐onset disease. [ABSTRACT FROM AUTHOR]

Published
2020
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14. Broad Raman scattering and luminescence in β-carotene solution.

Author

Nakamura, R., Yamamoto, S., and Nakahara, J.

Subjects
CAROTENES, SOLUTION (Chemistry), RAMAN effect
Abstract

Resonant secondary radiation spectra of dilute β-carotene solution (10[sup -4]-10[sup -5] M) are measured under stationary excitation. The excitation energy is varied within 0-0 and 0-1 transition energies in the S[sub 2]-S[sub 0] transition of β-carotene. When the excitation energy is varied from the peak of the 0-0 absorption band to the low-energy side at 60 K and 175 K, (a) the line shape of 0-0 emission band changes from symmetric to asymmetric, and (b) the intensity of luminescence rapidly decreases as compared with the intensity of Raman scattering by v[sub l], v[sub 2], and v[sub 3] intramolecular vibronic modes of β-carotene. When the 0-1 absorption band is excited, we successfully separate luminescence and broad Raman component (BR), which is resonant Raman scattering of low-frequency phonon modes in solution. The line shape of the density of vibronic states weighed by the coupling strength between electronic states in a dye molecule and vibrations of the surrounding atoms (WDOS) is determined by BR. Taking into account inhomogeneous broadening and assuming linear electronphonon coupling, the resonant secondary radiation spectra are calculated using obtained WDOS. The above characters of the experimental results (a) and (b) are well reproduced by the calculations. [ABSTRACT FROM AUTHOR]

Published
2002
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17. Thermoelectric properties of lanthanum sulfide with Sm, Eu, and Yb additives.

Author

Nakahara, J. F., Takeshita, T., Tschetter, M. J., Beaudry, B. J., and Gschneidner, K. A.

Subjects
*LANTHANUM compounds, *SAMARIUM, *EUROPIUM, *YTTERBIUM, *THERMOELECTRICITY
Abstract

Presents a study which determined the thermoelectric properties of lanthanum sulfide with samarium, europium and ytterbium additives. Analysis of the lattice parameters of the alloys; Variation of the Seebeck coefficient and electrical resistivity as a function of electron concentration; Stability of the samarium and europium ternaries.

Published
1988
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19. Hydrogenated amorphous carbon films deposited by low-frequency plasma chemical vapor deposition at room temperature.

Author

Shimozuma, M., Tochitani, G., Ohno, H., Tagashira, H., and Nakahara, J.

Subjects
CARBON, CHEMICAL vapor deposition, THIN films
Abstract

Provides information on hydrogenated amorphous carbon films prepared at room temperature by low frequency plasma chemical vapor deposition using methane and hydrogen. Measurement of resistivity and breakdown electric field after deposition; Infrared absorption spectrum of the grown film for the carbon-hydrogen stretching mode region; Raman spectroscopy using argon laser excitation.

Published
1989
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20. Intermolecular interaction of carbon disulfide under pressure (high pressure and effective negative solvation pressure)

Author

Ishibashi, Y., Mishina, T., Nakahara, J., Ishibashi, Y., Mishina, T., and Nakahara, J.

Abstract

Raman spectra of liquid carbon disulfide (CS2) were measured under high pressures and in dilution with ethanol and with heptane. The pressure and concentration dependences of the molecular vibration modes 1 and 2 2 of CS2 are discussed. The intermolecular distance changes simultaneously with concentration and pressure. In addition, dilution also varies the environment around the CS2 molecule. The derivative of the intermolecular interaction energy is obtained from the frequency shift from the gas phase to the liquid phase of the 1 and 2 2 vibrations. The results show that dilution effectively acts as negative pressures, where the intermolecular distance between CS2 molecules increases in the mixtures with ethanol and heptane. These effective pressures and pressures give the change in the intramolecular double bond between carbon and sulfur atoms. But, these give a different effect for the damping of vibrations.

Published
2006

23. Improved perfluoroalkylether fluid development

Author

Paciorek, K. L, Masuda, S. R, Nakahara, J. H, and Kratzer, R. H

Subjects
Inorganic And Physical Chemistry
Abstract

The objective of this program was to optimize and scale up the linear perfluoroalkylether stabilization process and to provide test data regarding the fluids' thermal oxidative stability in the presence of metal alloys. The stabilization of Fomblin Z-25 was scaled up to 300 g of fluid. The modified fluid was stable at 316 C in oxygen in the presence of M-50 alloy for more than 24 hrs but less than 40 hrs; the amount of volatiles produced after 24 hrs was 5.5 mg/g. In the presence of Ti(4Al,4Mn) alloy, under the above conditions, following an exposure of 24 hrs, the amount of volatiles formed was 6.2 mg/g; 56 hrs exposure yielded 13.9 mg/g. The commercial fluid at 288 C (in oxygen) in the presence of M-50 after 15 hrs of exposure decomposed extensively, 342 mg/g; in the presence of Ti(4Al,4Mn) alloy after only 8 hrs at 288 C, the amount of volatiles was 191 mg/g. Formulation of the commercial fluid with C2PN3 additive was not as effective as the stabilization processing. All the perfluoroalkylether fluids studied were stable in nitrogen at 343 C. The thermal oxidative stability in the absence of metal alloys varied, with Aflunox exhibiting the best behavior. All the fluids were degraded in oxygen at 316 C during 24 hrs exposure to Ti(4Al,4Mn) alloy with the exception of a perfluoroalkylether substituted triazine and the modified Z-25.

Published
1987

24. Improved perfluoroalkylether fluid development

Author

Jones, W. R., Jr, Paciorek, K, Nakahara, J, Smythe, M, and Kratzer, R

Subjects
Nonmetallic Materials
Abstract

The feasibility of transforming a commercial linear perfluoroalkylether fluid into a material stable in the presence of metals and metal alloys in oxidizing atmospheres at 300 C without the loss of the desirable viscosity temperature characteristics was determined. The approach consisted of thermal oxidative treatment in the presence of catalyst to remove weak links, followed by transformation of the created functional groups into phospha-s-triazine linkages. It it found that the experimental material obtained in 66% yield from the commercial fluid exhibits, over an 8 hr period at 300 C in the presence of Ti(4Al, 4Mn) alloy, thermal oxidative stability better by a factor of 2.6x1000 based on volatiles evolved than the commercial product. The viscosity and molecular weight of the developed fluid are unchanged and are essentially identical with the commercial material. No metal corrosion occurs with the experimental fluid at 300 C.

Published
1986

25. The effects of metals and inhibitors on thermal oxidative degradation reactions of unbranched perfluoroalkyl ethers

Author

Jones, W. R., Jr, Paciorek, K. J. L, Harris, D. H, Smythe, M. E, Nakahara, J. H, and Kratzer, R. H

Subjects
Nonmetallic Materials
Abstract

Thermal oxidative degradation studies were performed on unbranched perfluoroalkylethers at 288 C in oxygen. Metals and alloys studied included Ti, Al, and Ti (4 Al, 4 Mn). The mechanism of degradation was by chain scission. Ti and Al promoted less degradation than Ti (4 Al, 4 Mn). The two inhibitors investigated (a perfluorophenyl phosphine and a phosphatriazine) reduced degradation rates by several orders of magnitude. Both inhibitors were effective for the same duration (75 to 100 hours). The phosphatriazine appeared to provide more surface protection.

Published
1985

26. Synthesis of perfluoroalkylene aromatic diamines

Author

Paciorek, K. L, Ito, T. I, Nakahara, J. H, and Kratzer, R. H

Subjects
Nonmetallic Materials
Abstract

Analogues of methylene dianilines were synthesized, in which the methylene group between the two aromatic nuclei was replaced by various perfluoroalkylene linkage. The hydrolytic thermal, and thermal oxidative stabilities of PMR Polyimides derived from these diamines were determined. Three types of PMR Polyimide discs were fabricated from the dimethyl ester of 3,3', 4,4'-benzophenonetetracarboxylic acid, the methyl ester of 5-norbornene-2,3-dicarboxylic acid, and one of the following three diamines: methyl dianiline, 1,3-bis(4-aminophenyl)hexafluoropropane, and 2,2-bis(4-aminophenyl)hexafluoropropane. The polyimide based on 2,2-bis(4-aminophenyl)hexafluoropropane exhibited the best hydrolytic, thermal, and thermal oxidative stability as determined by moisture uptake and thermogravimetric analysis.

Published
1978

27. Cross Linking and Degradation Mechanisms in Model Sealant Candidates

Author

Paciorek, K. L, Kaufman, J, Ito, T. I, Nakahara, J. H, and Kratzer, R. H

Subjects
Nonmetallic Materials
Abstract

Model compounds were investigated as to which type of heterocyclic ring is the most advantageous for curing sealants based on perfluoroalkylether chains. The relative thermal, thermal oxidative, hydrolytic, and fuel stability of potential crosslinks were determined. Specifically substituted materials were synthesized and evaluation of their stabilities in air, inert atmosphere, water, and Jet-A fuel at 235 and 325 C was made. Three heterocyclic ring systems were considered, namely, triazine, 1,2,4- and 1,3,4-oxadiazoles.

Published
1977

28. Syntheses and Degradations of Fluorinated Heterocyclics

Author

Paciorek, K. J. L, Kaufman, J, Nakahara, J. H, Ito, T. I, Kratzer, R. H, Rosser, R. W, and Parker, J. A

Subjects
Chemistry And Materials (General)
Abstract

2,5-Bis(perfluoro-n-heptyl)-, 2-perfluoroalkylether-5-perfluoro-n- heptyl- , and 2 , 5-bisperfluoroalkylether-1,3,4-oxadiazoles were synthesized and characterized. 2,5-Bis(perfluoro-n-heptyl)-1,3,4-oxadiazole was thermally and hydrolytically stable at 325 C; however, in the presence of air, degradation took place at 235 C. The perfluoroalkylether analogue exhibited thermal and hydrolytic stability at 325 C; it was found to be unaffected by jet-A fuel and air at 235 C. At 325 C in air some degradation occurred as evidenced by volatiles production, oxygen consumption, and 96% starting material recovery.

Published
1977

41. Preface

Author

Nakahara, J., primary, Kobayashi, T., additional, and Onari, S., additional

Published
2001
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49. Novel Trimethylsilyl-Substituted Aminobranes

Author

ULTRASYSTEMS DEFENSE INC IRVINE CA, Paciorek, K. J., Masuda, S. R., Hoferkamp, L. A., Nakahara, J. H., Kratzer, R. H., ULTRASYSTEMS DEFENSE INC IRVINE CA, Paciorek, K. J., Masuda, S. R., Hoferkamp, L. A., Nakahara, J. H., and Kratzer, R. H.

Abstract

Published in Inorganic Chemistry, v30 n3 p577-579, 1991.

Published
1991

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