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Journal of the American Chemical Society

Volumn 132, Issue 38, 2010, Pages 13313-13319

Torsion potential in polydiacetylene: Accurate computations on oligomers extrapolated to the polymer limit

(3) Sears, John S a Chance, Ronald R a Brédas, Jean Luc a

a GEORGIA INSTITUTE OF TECHNOLOGY (United States)

Author keywords

[No Author keywords available]

Indexed keywords

COLOR CHANGES; COMPUTATIONALLY EFFICIENT; DIACETYLENES; LOW ENERGIES; OPTOELECTRONIC PROPERTIES; ORDER OF MAGNITUDE; POLYDIACETYLENES; POLYMER CHAINS; RELIABLE ESTIMATES; SENSOR MATERIALS; TORSIONAL BARRIERS; WORK-RELATED;

COLORIMETRY; ELECTRONIC STRUCTURE; EXTRAPOLATION; LANGMUIR BLODGETT FILMS; OLIGOMERS; POLYMERS; TORSIONAL STRESS;

ACETYLENE;

ACETYLENE DERIVATIVE; OLIGOMER; POLYDIACETYLENE; POLYMER; UNCLASSIFIED DRUG;

ARTICLE; CHEMICAL STRUCTURE; TORSION;

EID: 77957108203 PISSN: 00027863 EISSN: 15205126 Source Type: Journal
DOI: 10.1021/ja103769j Document Type: Article

Times cited : (25)

References (70)

1
- 0018479435
- Tieke, B., Lieser, G., and Wegner, G. J. Polym. Sci., Part A: Polym. Chem. 1979, 17 (6) 1631-1644
- (1979) J. Polym. Sci., Part A: Polym. Chem. , vol.17 , Issue.6 , pp. 1631-1644
- Tieke, B.¹ Lieser, G.² Wegner, G.³

2
- 28244470373
- Enkelmann, V. and Wegner, G. Makromol. Chem. 1977, 178 (2) 635-638
- (1977) Makromol. Chem. , vol.178 , Issue.2 , pp. 635-638
- Enkelmann, V.¹ Wegner, G.²

3
- 0000837822
- Enkelmann, V., Schleier, G., Wegner, G., Eichele, H., and Schwoerer, M. Chem. Phys. Lett. 1977, 52 (2) 314-319
- (1977) Chem. Phys. Lett. , vol.52 , Issue.2 , pp. 314-319
- Enkelmann, V.¹ Schleier, G.² Wegner, G.³ Eichele, H.⁴ Schwoerer, M.⁵

4
- 84939218263
- Wegner, G. Z. Naturforsch., Teil B 1969, B 24 (7) 824-832
- (1969) Z. Naturforsch., Teil B , vol.24 , Issue.7 , pp. 824-832
- Wegner, G.¹

5
- 3042548180
- (R679-R697
- Carpick, R. W., Sasaki, D. Y., Marcus, M. S., Eriksson, M. A., and Burns, A. R. J. Phys.: Condens. Matter 2004, 16 (23 R679-R697
- (2004) J. Phys.: Condens. Matter , vol.16 , Issue.23
- Carpick, R.W.¹ Sasaki, D.Y.² Marcus, M.S.³ Eriksson, M.A.⁴ Burns, A.R.⁵

6
- 84889324039
- In;, Ed.; Wiley-VCH: Weiheim
- Schott, M. In Photophysics of Molecular Materials: From Single Molecules to Single Crystals; Lanzani, G., Ed.; Wiley-VCH: Weiheim, 2006; pp 49-151.
- (2006) Photophysics of Molecular Materials: From Single Molecules to Single Crystals , pp. 49-151
- Schott, M.¹ Lanzani, G.²

7
- 77957106578
- Fields, S. C. and Prusik, T. Proceedings of the XVIth International Congress of Refrigeration 1983, 3, 793-800
- (1983) Proceedings of the XVIth International Congress of Refrigeration , vol.3 , pp. 793-800
- Fields, S.C.¹ Prusik, T.²

8
- 33749872824
- Riel, G. K., Winters, P., Patel, G., and Patel, P. Radiat. Protect. Dosimetry 2006, 120 (1-4) 259-262
- (2006) Radiat. Protect. Dosimetry , vol.120 , Issue.1-4 , pp. 259-262
- Riel, G.K.¹ Winters, P.² Patel, G.³ Patel, P.⁴

9
- 0034620345
- Carpick, R. W., Sasaki, D. Y., and Burns, A. R. Langmuir 2000, 16 (3) 1270-1278
- (2000) Langmuir , vol.16 , Issue.3 , pp. 1270-1278
- Carpick, R.W.¹ Sasaki, D.Y.² Burns, A.R.³

10
- 0018108263
- Muller, H. and Eckhardt, C. J. Mol. Cryst. Liq. Cryst. 1978, 45 (3-4) 313-318
- (1978) Mol. Cryst. Liq. Cryst. , vol.45 , Issue.3-4 , pp. 313-318
- Muller, H.¹ Eckhardt, C.J.²

11
- 0037150349
- Lee, D. C., Sahoo, S. K., Cholli, A. L., and Sandman, D. J. Macromolecules 2002, 35 (11) 4347-4355
- (2002) Macromolecules , vol.35 , Issue.11 , pp. 4347-4355
- Lee, D.C.¹ Sahoo, S.K.² Cholli, A.L.³ Sandman, D.J.⁴

12
- 33845222704
- Chance, R. R., Baughman, R. H., Muller, H., and Eckhardt, C. J. J. Chem. Phys. 1977, 67 (8) 3616-3618
- (1977) J. Chem. Phys. , vol.67 , Issue.8 , pp. 3616-3618
- Chance, R.R.¹ Baughman, R.H.² Muller, H.³ Eckhardt, C.J.⁴

13
- 67749106308
- Ryu, S., Yoo, I., Song, S., Yoon, B., and Kim, J. M. J. Am. Chem. Soc. 2009, 131 (11) 3800-3801
- (2009) J. Am. Chem. Soc. , vol.131 , Issue.11 , pp. 3800-3801
- Ryu, S.¹ Yoo, I.² Song, S.³ Yoon, B.⁴ Kim, J.M.⁵

14
- 0027281690
- Charych, D. H., Nagy, J. O., Spevak, W., and Bednarski, M. D. Science 1993, 261 (5121) 585-588
- (1993) Science , vol.261 , Issue.5121 , pp. 585-588
- Charych, D.H.¹ Nagy, J.O.² Spevak, W.³ Bednarski, M.D.⁴

15
- 0029158754
- Reichert, A., Nagy, J. O., Spevak, W., and Charych, D. J. Am. Chem. Soc. 1995, 117 (2) 829-830
- (1995) J. Am. Chem. Soc. , vol.117 , Issue.2 , pp. 829-830
- Reichert, A.¹ Nagy, J.O.² Spevak, W.³ Charych, D.⁴

16
- 76649099770
- Chen, X., Kang, S., Kim, M. J., Kim, J., Kim, Y. S., Kim, H., Chi, B., Kim, S. J., Lee, J. Y., and Yoon, J. Angew. Chem., Int. Ed. 2010, 49 (8) 1422-1425
- (2010) Angew. Chem., Int. Ed. , vol.49 , Issue.8 , pp. 1422-1425
- Chen, X.¹ Kang, S.² Kim, M.J.³ Kim, J.⁴ Kim, Y.S.⁵ Kim, H.⁶ Chi, B.⁷ Kim, S.J.⁸ Lee, J.Y.⁹ Yoon, J.¹⁰

17
- 70349349141
- Jelinek, R. and Silbert, L. Mol. BioSyst. 2009, 5 (8) 811-818
- (2009) Mol. BioSyst. , vol.5 , Issue.8 , pp. 811-818
- Jelinek, R.¹ Silbert, L.²

18
- 63849328932
- Van Averbeke, B. and Beljonne, D. J. Phys. Chem. A 2009, 113 (12) 2677-2682
- (2009) J. Phys. Chem. A , vol.113 , Issue.12 , pp. 2677-2682
- Van Averbeke, B.¹ Beljonne, D.²

19
- 72449187082
- Schmalz, T. G. and Griffin, L. L. J. Chem. Phys. 2009, 131 (22) 224301
- (2009) J. Chem. Phys. , vol.131 , Issue.22 , pp. 224301
- Schmalz, T.G.¹ Griffin, L.L.²

20
- 0005280022
- Tieke, B. and Lieser, G. Macromolecules 1985, 18 (3) 327-334
- (1985) Macromolecules , vol.18 , Issue.3 , pp. 327-334
- Tieke, B.¹ Lieser, G.²

21
- 0029253806
- Deckert, A. A., Horne, J. C., Valentine, B., Kiernan, L., and Fallon, L. Langmuir 1995, 11 (2) 643-649
- (1995) Langmuir , vol.11 , Issue.2 , pp. 643-649
- Deckert, A.A.¹ Horne, J.C.² Valentine, B.³ Kiernan, L.⁴ Fallon, L.⁵

22
- 0000363583
- Deckert, A. A., Fallon, L., Kiernan, L., Cashin, C., Perrone, A., and Encalarde, T. Langmuir 1994, 10 (6) 1948-1954
- (1994) Langmuir , vol.10 , Issue.6 , pp. 1948-1954
- Deckert, A.A.¹ Fallon, L.² Kiernan, L.³ Cashin, C.⁴ Perrone, A.⁵ Encalarde, T.⁶

23
- 12344333740
- Huang, X., Jiang, S. G., and Liu, M. H. J. Phys. Chem. B 2005, 109 (1) 114-119
- (2005) J. Phys. Chem. B , vol.109 , Issue.1 , pp. 114-119
- Huang, X.¹ Jiang, S.G.² Liu, M.H.³

24
- 0024017136
- Rawiso, M., Aime, J. P., Fave, J. L., Schott, M., Muller, M. A., Schmidt, M., Baumgartl, H., and Wegner, G. J. Physique 1988, 49 (5) 861-880
- (1988) J. Physique , vol.49 , Issue.5 , pp. 861-880
- Rawiso, M.¹ Aime, J.P.² Fave, J.L.³ Schott, M.⁴ Muller, M.A.⁵ Schmidt, M.⁶ Baumgartl, H.⁷ Wegner, G.⁸

25
- 0026419818
- Li, Y. J. and Chu, B. Macromolecules 1991, 24 (14) 4115-4122
- (1991) Macromolecules , vol.24 , Issue.14 , pp. 4115-4122
- Li, Y.J.¹ Chu, B.²

26
- 33748554154
- Schott, M. J. Phys. Chem. B 2006, 110 (32) 15864-15868
- (2006) J. Phys. Chem. B , vol.110 , Issue.32 , pp. 15864-15868
- Schott, M.¹

27
- 33847085750
- Chance, R. R. Macromolecules 1980, 13 (2) 396-398
- (1980) Macromolecules , vol.13 , Issue.2 , pp. 396-398
- Chance, R.R.¹

28
- 0001190588
- Baughman, R. H. J. Polym. Sci., Part B: Polym. Phys. 1974, 12 (8) 1511-1535
- (1974) J. Polym. Sci., Part B: Polym. Phys. , vol.12 , Issue.8 , pp. 1511-1535
- Baughman, R.H.¹

29
- 70349089767
- Filhol, J. S., Deschamps, J., Dutremez, S. G., Boury, B., Barisien, T., Legrand, L., and Schott, M. J. Am. Chem. Soc. 2009, 131 (20) 6976-6988
- (2009) J. Am. Chem. Soc. , vol.131 , Issue.20 , pp. 6976-6988
- Filhol, J.S.¹ Deschamps, J.² Dutremez, S.G.³ Boury, B.⁴ Barisien, T.⁵ Legrand, L.⁶ Schott, M.⁷

30
- 0025387504
- Brédas, J. L. and Heeger, A. J. Macromolecules 1990, 23 (4) 1150-1156
- (1990) Macromolecules , vol.23 , Issue.4 , pp. 1150-1156
- Brédas, J.L.¹ Heeger, A.J.²

31
- 36749105082
- Patel, G. N., Chance, R. R., and Witt, J. D. J. Chem. Phys. 1979, 70 (9) 4387-4392
- (1979) J. Chem. Phys. , vol.70 , Issue.9 , pp. 4387-4392
- Patel, G.N.¹ Chance, R.R.² Witt, J.D.³

32
- 0001401154
- Wudl, F. and Bitler, S. P. J. Am. Chem. Soc. 1986, 108 (15) 4685-4687
- (1986) J. Am. Chem. Soc. , vol.108 , Issue.15 , pp. 4685-4687
- Wudl, F.¹ Bitler, S.P.²

33
- 26144450583
- Perdew, J. P. and Zunger, A. Phys. Rev. B 1981, 23 (10) 5048-5079
- (1981) Phys. Rev. B , vol.23 , Issue.10 , pp. 5048-5079
- Perdew, J.P.¹ Zunger, A.²

34
- 0037054670
- Polo, V., Kraka, E., and Cremer, D. Mol. Phys. 2002, 100 (11) 1771-1790
- (2002) Mol. Phys. , vol.100 , Issue.11 , pp. 1771-1790
- Polo, V.¹ Kraka, E.² Cremer, D.³

35
- 20544468409
- Lundberg, M. and Siegbahn, P. E. M. J. Chem. Phys. 2005, 122 (22) 224103
- (2005) J. Chem. Phys. , vol.122 , Issue.22 , pp. 224103
- Lundberg, M.¹ Siegbahn, P.E.M.²

36
- 33749598656
- Knoll, E. H. and Friesner, R. A. J. Phys. Chem. B 2006, 110 (38) 18787-18802
- (2006) J. Phys. Chem. B , vol.110 , Issue.38 , pp. 18787-18802
- Knoll, E.H.¹ Friesner, R.A.²

37
- 57349145899
- Goldfeld, D. A., Bochevarov, A. D., and Friesner, R. A. J. Chem. Phys. 2008, 129 (21) 214105
- (2008) J. Chem. Phys. , vol.129 , Issue.21 , pp. 214105
- Goldfeld, D.A.¹ Bochevarov, A.D.² Friesner, R.A.³

38
- 73949084299
- Hall, M. L., Goldfeld, D. A., Bochevarov, A. D., and Friesner, R. A. J. Chem. Theory Comput. 2009, 5 (11) 2996-3009
- (2009) J. Chem. Theory Comput. , vol.5 , Issue.11 , pp. 2996-3009
- Hall, M.L.¹ Goldfeld, D.A.² Bochevarov, A.D.³ Friesner, R.A.⁴

39
- 34250641957
- Holroyd, L. F. and van Mourik, T. Chem. Phys. Lett. 2007, 442 (1-3) 42-46
- (2007) Chem. Phys. Lett. , vol.442 , Issue.1-3 , pp. 42-46
- Holroyd, L.F.¹ Van Mourik, T.²

40
- 33846595224
- Jurecka, P., Cerny, J., Hobza, P., and Salahub, D. R. J. Comput. Chem. 2007, 28 (2) 555-569
- (2007) J. Comput. Chem. , vol.28 , Issue.2 , pp. 555-569
- Jurecka, P.¹ Cerny, J.² Hobza, P.³ Salahub, D.R.⁴

41
- 34249288385
- Zhao, Y. and Truhlar, D. G. J. Chem. Theory Comput. 2007, 3 (1) 289-300
- (2007) J. Chem. Theory Comput. , vol.3 , Issue.1 , pp. 289-300
- Zhao, Y.¹ Truhlar, D.G.²

42
- 33748591851
- Wodrich, M. D., Corminboeuf, C., and Schleyer, P. V. Org. Lett. 2006, 8 (17) 3631-3634
- (2006) Org. Lett. , vol.8 , Issue.17 , pp. 3631-3634
- Wodrich, M.D.¹ Corminboeuf, C.² Schleyer, P.V.³

43
- 77949679522
- Vázquez-Mayagoitia, Á., Sherrill, C. D., Apraá, E., and Sumpter, B. G. J. Chem. Theory Comput. 2010, 6 (3) 727-734
- (2010) J. Chem. Theory Comput. , vol.6 , Issue.3 , pp. 727-734
- Vázquez-Mayagoitia, Á.¹ Sherrill, C.D.² Apraá, E.³ Sumpter, B.G.⁴

44
- 70349915665
- Suponitsky, K. Y., Liao, Y., and Masunov, A. E. J. Phys. Chem. A 2009, 113 (41) 10994-11001
- (2009) J. Phys. Chem. A , vol.113 , Issue.41 , pp. 10994-11001
- Suponitsky, K.Y.¹ Liao, Y.² Masunov, A.E.³

45
- 0031578415
- Choi, C. H., Kertesz, M., and Karpfen, A. Chem. Phys. Lett. 1997, 276 (3-4) 266-268
- (1997) Chem. Phys. Lett. , vol.276 , Issue.3-4 , pp. 266-268
- Choi, C.H.¹ Kertesz, M.² Karpfen, A.³

46
- 0000186728
- Choi, C. H., Kertesz, M., and Karpfen, A. J. Chem. Phys. 1997, 107 (17) 6712-6721
- (1997) J. Chem. Phys. , vol.107 , Issue.17 , pp. 6712-6721
- Choi, C.H.¹ Kertesz, M.² Karpfen, A.³

47
- 33748805997
- Zhao, Y. and Truhlar, D. G. J. Phys. Chem. A 2006, 110 (35) 10478-10486
- (2006) J. Phys. Chem. A , vol.110 , Issue.35 , pp. 10478-10486
- Zhao, Y.¹ Truhlar, D.G.²

48
- 18044392571
- (043002
- Baer, R. and Neuhauser, D. Phys. Rev. Lett. 2005, 94 (4 043002
- (2005) Phys. Rev. Lett. , vol.94 , Issue.4
- Baer, R.¹ Neuhauser, D.²

49
- 24144451155
- Baerends, E. J. and Gritsenko, O. V. J. Chem. Phys. 2005, 123 (6) 62202
- (2005) J. Chem. Phys. , vol.123 , Issue.6 , pp. 62202
- Baerends, E.J.¹ Gritsenko, O.V.²

50
- 40549127108
- Zhao, Y. and Truhlar, D. G. Acc. Chem. Res. 2008, 41 (2) 157-167
- (2008) Acc. Chem. Res. , vol.41 , Issue.2 , pp. 157-167
- Zhao, Y.¹ Truhlar, D.G.²

51
- 55849117399
- Chai, J. D. and Head-Gordon, M. Phys. Chem. Chem. Phys. 2008, 10 (44) 6615-6620
- (2008) Phys. Chem. Chem. Phys. , vol.10 , Issue.44 , pp. 6615-6620
- Chai, J.D.¹ Head-Gordon, M.²

52
- 40149109196
- (084106
- Chai, J. D. and Head-Gordon, M. J. Chem. Phys. 2008, 128 (8 084106
- (2008) J. Chem. Phys. , vol.128 , Issue.8
- Chai, J.D.¹ Head-Gordon, M.²

53
- 0001436824
- Jurgenslutovsky, R. and Almlof, J. Chem. Phys. Lett. 1991, 178 (5-6) 451-454
- (1991) Chem. Phys. Lett. , vol.178 , Issue.5-6 , pp. 451-454
- Jurgenslutovsky, R.¹ Almlof, J.²

54
- 0037665260
- Wolinski, K. and Pulay, P. J. Chem. Phys. 2003, 118 (21) 9497-9503
- (2003) J. Chem. Phys. , vol.118 , Issue.21 , pp. 9497-9503
- Wolinski, K.¹ Pulay, P.²

55
- 45849097248
- Ksiazek, A. and Wolinski, K. Mol. Phys. 2008, 106 (6) 769-786
- (2008) Mol. Phys. , vol.106 , Issue.6 , pp. 769-786
- Ksiazek, A.¹ Wolinski, K.²

56
- 20344381993
- Feyereisen, M., Fitzgerald, G., and Komornicki, A. Chem. Phys. Lett. 1993, 208 (5-6) 359-363
- (1993) Chem. Phys. Lett. , vol.208 , Issue.5-6 , pp. 359-363
- Feyereisen, M.¹ Fitzgerald, G.² Komornicki, A.³

57
- 33746563448
- Shao, Y., Molnar, L. F., and Jung, Y. Phys. Chem. Chem. Phys. 2006, 8 (27) 3172-3191
- (2006) Phys. Chem. Chem. Phys. , vol.8 , Issue.27 , pp. 3172-3191
- Shao, Y.¹ Molnar, L.F.² Jung, Y.³

58
- 38849114436
- Distasio, R. A., Steele, R. P., and Head-Gordon, M. Mol. Phys. 2007, 105 (19-22) 2731-2742
- (2007) Mol. Phys. , vol.105 , Issue.19-22 , pp. 2731-2742
- Distasio, R.A.¹ Steele, R.P.² Head-Gordon, M.³

59
- 0004245508
- Werner, H. J., Knowles, P. J., and Lindh, R. MOLPRO 2009, 1
- (2009) MOLPRO , pp. 1
- Werner, H.J.¹ Knowles, P.J.² Lindh, R.³

60
- 0002745201
- Hampel, C., Peterson, K. A., and Werner, H. J. Chem. Phys. Lett. 1992, 190 (1-2) 1-12
- (1992) Chem. Phys. Lett. , vol.190 , Issue.1-2 , pp. 1-12
- Hampel, C.¹ Peterson, K.A.² Werner, H.J.³

61
- 0000724478
- Helgaker, T., Klopper, W., Koch, H., and Noga, J. J. Chem. Phys. 1997, 106 (23) 9639-9646
- (1997) J. Chem. Phys. , vol.106 , Issue.23 , pp. 9639-9646
- Helgaker, T.¹ Klopper, W.² Koch, H.³ Noga, J.⁴

62
- 0347007668
- Feller, D. J. Chem. Phys. 1992, 96 (8)) 6104-6114
- (1992) J. Chem. Phys. , vol.96 , Issue.8 , pp. 6104-6114
- Feller, D.¹

63
- 33846490219
- Gierschner, J., Cornil, J., and Egelhaaf, H. J. Adv. Mater. 2007, 19 (2) 173-191
- (2007) Adv. Mater. , vol.19 , Issue.2 , pp. 173-191
- Gierschner, J.¹ Cornil, J.² Egelhaaf, H.J.³

64
- 0031222029
- Meier, H., Stalmach, U., and Kolshorn, H. Acta Polym. 1997, 48 (9) 379-384
- (1997) Acta Polym. , vol.48 , Issue.9 , pp. 379-384
- Meier, H.¹ Stalmach, U.² Kolshorn, H.³

65
- 36549102457
- Rossi, G., Chance, R. R., and Silbey, R. J. Chem. Phys. 1989, 90 (12) 7594-7601
- (1989) J. Chem. Phys. , vol.90 , Issue.12 , pp. 7594-7601
- Rossi, G.¹ Chance, R.R.² Silbey, R.³

66
- 72549114373
- Zou, G., Jiang, H., Zhang, Q. J., Kohn, H., Manaka, T., and Iwamoto, M. J. Mater. Chem. 2010, 20 (2) 285-291
- (2010) J. Mater. Chem. , vol.20 , Issue.2 , pp. 285-291
- Zou, G.¹ Jiang, H.² Zhang, Q.J.³ Kohn, H.⁴ Manaka, T.⁵ Iwamoto, M.⁶

67
- 41149177461
- Hsu, L., Cvetanovich, G. L., and Stupp, S. I. J. Am. Chem. Soc. 2008, 130 (12) 3892-3899
- (2008) J. Am. Chem. Soc. , vol.130 , Issue.12 , pp. 3892-3899
- Hsu, L.¹ Cvetanovich, G.L.² Stupp, S.I.³

68
- 34250620978
- Zou, G., Kohn, H., Ohshima, Y., Manaka, T., and Iwamoto, M. Chem. Phys. Lett. 2007, 442 (1-3) 97-100
- (2007) Chem. Phys. Lett. , vol.442 , Issue.1-3 , pp. 97-100
- Zou, G.¹ Kohn, H.² Ohshima, Y.³ Manaka, T.⁴ Iwamoto, M.⁵

69
- 33845240402
- Manaka, T., Kon, H., Ohshima, Y., Zou, G., and Iwamoto, M. Chem. Lett. 2006, 35 (9) 1028-1029
- (2006) Chem. Lett. , vol.35 , Issue.9 , pp. 1028-1029
- Manaka, T.¹ Kon, H.² Ohshima, Y.³ Zou, G.⁴ Iwamoto, M.⁵

70
- 0005364316
- Morgan, J., Rumbles, G., Crystall, B., Smith, T. A., and Bloor, D. Chem. Phys. Lett. 1992, 196 (5) 455-461
- (1992) Chem. Phys. Lett. , vol.196 , Issue.5 , pp. 455-461
- Morgan, J.¹ Rumbles, G.² Crystall, B.³ Smith, T.A.⁴ Bloor, D.⁵

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