منابع مشابه
Fossil genes and microbes in the oldest ice on earth.
Although the vast majority of ice that formed on the Antarctic continent over the past 34 million years has been lost to the oceans, pockets of ancient ice persist in the Dry Valleys of the Transantarctic Mountains. Here we report on the potential metabolic activity of microbes and the state of community DNA in ice derived from Mullins and upper Beacon Valleys. The minimum age of the former is ...
متن کاملDiversity of Holocene life forms in fossil glacier ice.
Studies of biotic remains of polar ice caps have been limited to morphological identification of plant pollen and spores. By using sensitive molecular techniques, we now demonstrate a much greater range of detectable organisms; from 2000- and 4000-year-old ice-core samples, we obtained and characterized 120 clones that represent at least 57 distinct taxa and reveal a diversity of fungi, plants,...
متن کاملNortheast Siberian ice wedges confirm Arctic winter warming over the past two millennia
15 Arctic climate has experienced major changes over the past millennia that are not fully 16 understood in terms of their controls and seasonality. Stable-data from ice wedges in 17 permafrost provide unique information on past winter climate. Recently, an ice-wedge 18 record from the Lena River Delta suggested for the first time that Siberian winter 19 temperatures increased throughout the Ho...
متن کاملCenterpoint Theorems for Wedges
The Centerpoint Theorem states that, for any set S of n points in R, there exists a point p in R such that every closed halfspace containing p contains at least dn/(d+ 1)e points of S. We consider generalizations of the Centerpoint Theorem in which halfspaces are replaced with wedges (cones) of angle α. In R, we give bounds that are tight for all values of α and give an O(n) time algorithm to f...
متن کاملFloodlight illumination of infinite wedges
The floodlight illumination problem asks whether there exists a one-to-one placement of n floodlights illuminating infinite wedges of angles α1, . . . , αn at n sites p1, . . . , pn in a plane such that a given infinite wedge W of angle θ located at point q is completely illuminated by the floodlights. We prove that this problem is NP-hard, closing an open problem from 2001 [6]. In fact, we sho...
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ژورنال
عنوان ژورنال: Nature
سال: 1966
ISSN: 0028-0836,1476-4687
DOI: 10.1038/211728a0