26,253 research outputs found
Short- and long-term evolution in our arms race with cancer: Why the war on cancer is winnable.
Human society is engaged in an arms race against cancer, which pits one evolutionary process-human cultural evolution as we develop novel cancer therapies-against another evolutionary process-the ability of oncogenic selection operating among cancer cells to select for lineages that are resistant to our therapies. Cancer cells have a powerful ability to evolve resistance over the short term, leading to patient relapse following an initial period of apparent treatment efficacy. However, we are the beneficiaries of a fundamental asymmetry in our arms race against cancer: Whereas our cultural evolution is a long-term and continuous process, resistance evolution in cancer cells operates only over the short term and is discontinuous - all resistance adaptations are lost each time a cancer patient dies. Thus, our cultural adaptations are permanent, whereas cancer's genetic adaptations are ephemeral. Consequently, over the long term, there is good reason to expect that we will emerge as the winners in our war against cancer
Star formation in the Magellanic clouds
Because of their proximity, the Magellanic Clouds provide the opportunity to conduct a detailed study of the history and current state of star formation in dwarf irregular galaxies. There is considerable evidence that star formation in the Clouds was and is proceeding in a manner different from that found in a typical well-ordered spiral galaxy. Star formation in both Clouds appears to have undergone a number of relatively intense bursts. There exist a number of similarities and differences in the current state of star formation in the Magellanic Clouds and the Milky Way. Examination of Infrared Astronomy Satellite (IRAS) sources with ground based telescopes allows identification of highly evolved massive stars with circumstellar shells as well as several types of compact emission line objects
No Death Star -- For Now
A star passing within \sim 10^4 \au of the Sun would trigger a comet shower
that would reach the inner solar system about 0.18 Myr later. We calculate a
prior probability of ~0.4% that a star has passed this close to the Sun but
that the comet shower has not yet reached the Earth. We search the HIPPARCOS
catalog for such recent close-encounter candidates and, in agreement with
Garcia-Sanchez et al. (1997), find none. The new result reported in this Letter
is an estimation of the completeness of the search. Because of the relatively
bright completeness limit of the catalog itself, V~8, the search is sensitive
to only about half the stars that could have had such a near encounter. On the
other hand, we show that the search is sensitive to nearly all of the past
encounters that would lead to a major shower in the future and conclude that it
is highly unlikely that one will occur during the next 0.5 Myr.Comment: 10 pages, 1 figure. In press at The Astrophysical Journal Letter
Should Labor Defend Worker Rights as Human Rights? A Debate
The authors debate the relative merits and drawbacks of defining the labor movement under the umbrella of human rights, and the virtues of the rights of the individual versus the solidarity of the community
Principal -Blocks and Sylow -Subgroups
Let be a finite group with Sylow -subgroup .
Navarro-Tiep-Vallejo have conjectured that the principal -block of
contains exactly one irreducible Brauer character if and only if all odd-degree
ordinary irreducible characters in the principal -block of are fixed by
a certain Galois automorphism . Recent work of Navarro-Vallejo has
reduced this conjecture to a problem about finite simple groups. We show that
their conjecture holds for all finite simple groups, thus establishing the
conjecture for all finite groups.Comment: 12 page
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