LoP Guest Wrote:
I am more concerned about the IP Tracker than the mass extinction possibility at the moment. Whats that all about?
If men in dark suits show up at your door, get out the back door as quickly as possible and don't look back.....
Actually, I would like to know a little more about it and the name of anti-virus routine for it.
I ran the pdf through an ocr engine for the people afraid of virilii!
NATURE VOL. 308 19 APRIL 1984
neurophysin may hinder its further packaging and processing in the neurosecretory granules. On the other hand, the modified C-terminus may have caused the neurophysin to have lost one of its supposed functions, namely to protect the hormone from proteolytic degradationm.
Received 16 January; accepted 23 February 1984. 1. Valtin, H., Stewart, J. & Sokol, H. W. Handbk PhysioL 7, 131-171 (1974). 2. Pickering, B. T. Be North, W. G. Ann. N. Y. Acad Sci. 394, 72-81 (1982)- 3. Cheng, S. W. T., North, W. G. & Ge/lai, M. Ann. N. Y. Acad. 394, 437-480 (1982)- 4_ Brownstein, J. M., Russell, J. T. & Gainer, H. Science 207, 373-378 (1980). 5. Gainer, H. Prog. Brain Res. 60, 205-215 (1982). 6- Land, H., Schiitz, G., Schmale, H. & Richter, D. Nature 295, 299-303 (1982). 7. Schmale, H., Heinsohn, S. & Richter, D. EMBO J. 2, 763-767 (1983). S. Sokol, H. W. & Valtin, H. Ann. N. Y. Acad. Sci. 394, 1-828 (1982). 9. Valtin, H., North, W. G., LaRochelle, F. T., Sokol, H. W. & Morris, J. Proc. 7th int. Congr. Nephrol., Basel, 313-320 (Karger, Basel, 1978). 10. Land, H. et al. Nature 302, 342-344 (1983). 11. Ivell, R. & Richter, D. Proc. nam. Acad. Sci. U.S.A. (in the press). 12. Valtin, H. & Schroeder, H. A. Am. J. Physiol. 206, 425-430 (1964). 11 Southern, E. M. .1 molec. Biol. 98, 503-517 (1975).
Terrestrial mass extinctions, cometary impacts and the Sun's motion perpendicular to the galactic plane Michael R. Rampino* & Richard B. Stothers National Aeronautics and Space Administration, Goddard Institute for Space Studies, 2880 Broadway, New York, New York 10025, USA
Episodes of mass extinctions on the Earth are now strongly suspec-ted to be cyclical'. We report here that our analysis of the data of Raup and Sepkoskil suggests that the dominant cyclicity in major marine mass extinctions during at least the past 250 Myr is 30± 1 Myr, with the standard deviation of an individual episode being ±9 Myr. We find this terrestrial cycle to be strongly corre-lated with the time needed for the Solar System to oscillate vertically about the plane of the Galaxy, which is 33 ± 3 Myr according to the best current astronomical evidence. It is argued that galactic triggering or forcing of terrestrial biological crises may arise as a result of collisions (or close encounters) of the Solar System with intermediate-sized to large-sized interstellar clouds of gas and dust, which are sufficiently concentrated towards the galactic plane to produce the observed cyclicity and its scatter. Among other consequences, a nearby interstellar cloud would gravitationally perturb the Solar System's family of comets and thereby increase the flux of comets and comet-derived bodies near the Earth, leading to large-body impacts. We find a dominant cyclicity of 31 ± 1 Myr in the observed age distribution of impact craters on Earth, the phase of this cycle agreeing with that shown by the major biological crises. Our galactic hypothesis can thus simultaneously account for the mean interval between major terrestrial crises and for the 50% scatter of the time intervals about their mean value. Raup and Sepkoskil have very recently presented evidence for an approximate cyclicity in marine mass extinctions over the past 250 Myr. Fourier analysis of their data showed a dominant periodicity of 30 Myr, a best-fit curve yielded a cycle of 26 Myr, and a non-parametric test (previously developed independently and somewhat differently in ref. 2) revealed a significant cycle at 26 Myr and an only slightly less significant cycle at 30 Myr. Using less extensive data, Fischer and Arthur3 had already suggested a 32-Myr periodicity in marine mass extinctions. Which periodicity, 26 Myr or 30 Myr, should be preferred?
*Present address: Department of Geological Sciences, Columbia University, New York, New York 10027, USA.
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LETTERS TO NATURE
We thank Heidje Christiansen for technical assistance and Drs Monika Rehbein for DNA preparation, Gerd Scherer for providing A641 and Richard Ivell for helpful discussions. This work received financial support from the Deutsche Forschungsgemeinschaft.
14. Maxam, A. M. & Gilbert, W. Meth. Enzym. 65, 499-560 (1980). 15. Wallace, R. B. et aL Nucleic Acids Res. 6, 3543-3557 (1979). 16. Breslow, E. A. Rev. Biochem. 48, 251-274 (1979). 17. Lu, C.-L., Cantin, M., Seidah, N. G. & Chratien, M..1. Histochern. Cytochern. 30,999-1003 (1982). 18. Martin, R. & Voigt, K. H. Nature 289, 502-504 (1981). 19. Russell, J. T., Brownstein, M. J. & Gainer, H. Endocrinology 107, 1880-1981 (1980). 20_ Chirgwin, J. M., Przybyla, A. E., MacDonald, R. J. & Rutter, W. J. Biochemistry 18, 5294-5299 (1979). 21. BIM, N. & Stafford, D. W. Nucleic Acids Res. 3, 2303-2308 (1976). 22. Murray. N. E., Brammar, W. J. & Murray, K. Malec. gen. Genet. 150, 53-61 (1977). 23. Breathnach, R. & Chambon, P. A. Rev. Biochem. 50, 349-383 (1981). 24. Gal, A., Nahon, J.-L. & Sala-Trepat, J. M. Analyt. Biochem. 132, 190-194 (1983). • 25. Kidd, V_ J., Wallace, R. B., ltakura, K. & Woo, S.L.C. Nature 304, 230-234 (1983).
Raup and Sepkoski listed all discernible mass extinction peaks that exceeded 2% extinctions on a family level. As they were well aware, however, there are a number of uncertainties in their selection procedure. First, 2% may be too small to be statistically meaningful; Raup4 elsewhere suggested the use of 10%. Second, there are several minor fluctuations on the time curve of mass extinctions, some of which Raup and Sepkoski selected as true peaks and others they rejected as spurious peaks. Third, as the resolution in time is only one geological stage, other individual minor mass extinction episodes may exist at the substage level. In view of these uncertainties concerning identification and significance, we consider it best to follow Raup4 and adopt a cutoff of 10% extinctions, while disregarding all the minor inflections on the curve. The large remaining peaks then refer exclusively to the major mass extinction episodes and can be assumed to be completely sampled. They are listed in Table 1 (where the dates have been slightly revised according to ref. 5). Nine dates appear in this table, in contrast to the 12 listed by Raup and Sepkoski. Intervals of time between successive episodes of major mass extinctions lie in the range 17-53 Myr, with mean time interval 29 Myr. We regard the large (50%) dispersion as physically real, although some of it must be due to uncertainties of the dating. Reasons given below suggest that the dispersion is randomly generated. If, however, a true underlying mean periodicity does exist and no major mass extinction episodes are either missing or redundant, we can unambiguously assign a cycle number to each episode (Table 1). Non-parametric tests (like those in refs 1,2) are then no longer appropriate. Regression of the episode date on the cycle number by the method of least squares provides an unbiased estimate of the best-fitting mean period, which is found to be 30± 1 Myr. If other recently proposed geological time scales are adopted', essentially the same mean period emerges. This invariance is not surprising because the central limit theorem ensures that the presence of even rather large random errors in the dates will not significantly affect either the mean time interval or the best-fitting least-squares period. If the cycle number is left as a free parameter, the best-fitting mean period P derived from a suitable non-parametric method2, m which the observed times are fitted to a formula of the type t = to+ nP, is 26 Myr, where t, to and n are an observed time, the most recent epoch and an integer, respectively. This would agree with Raup and Sepkoski's1 result. However, Raup and Sepkoski have emphasized the approximate nature of any period that can be derived from so few data points. We prefer, in fact, the assignment of the cycle numbers as given above and therefore the period of 30 Myr. There are additional reasons for our preference: first, other kinds of geological data (including 41 dated impact craters) show periods of 30-35 Myr, and, second,
©1984 Nature Publishing Group
am dressed in a dark suit today
and i werk fer da gubbmint