Nature：结肠癌干细胞的标记
小肠和结肠壁上的细胞在整个生命中能迅速再生。虽然它们是所有干细胞中功能最明确的细胞之一，但分离出纯粹或高度富集的小肠上皮干细胞群一直是一个难以实现的目标。现在，这个目标已经实现。Lgr5基因（Wnt细胞信号系统）已经被确定为几种成年组织和癌症中干细胞的一个独特标记。Lgr5最初是在结肠癌细胞中发现的，现在在恶化前的小鼠腺瘤中也发现了，这说明Lgr5也许是结肠癌干细胞的一个标记。
原始出处:
Nature 449, 1029-1032 (25 October 2007) | doi:10.1038/nature06229; Received 20 June 2007; Accepted 3 September 2007
Attosecond spectroscopy in condensed matter
A. L. Cavalieri1, N. Müller2, Th. Uphues1,2, V. S. Yakovlev3, A. Baltu
ka1,4, B. Horvath1, B. Schmidt5, L. Blümel5, R. Holzwarth5, S. Hendel2, M. Drescher6, U. Kleineberg3, P. M. Echenique7, R. Kienberger1, F. Krausz1,3 & U. Heinzmann2
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching, Germany
- Fakultät für Physik, Universität Bielefeld, D-33615 Bielefeld, Germany
- Department für Physik, Ludwig-Maximilians-Universität, Am Coulombwall 1, D-85748 Garching, Germany
- Institut für Photonik, Technische Universität Wien, Gu
hausstr. 27, A-1040 Wien, Austria
- Menlo Systems GmbH, Am Klopferspitz 19, D-82152 Martinsried, Germany
- Institut für Experimentalphysik, Universität Hamburg, Luruper Chaussee 149, D-22761 Hamburg, Germany
- Dpto. Fisica de Materiales UPV/EHU, Centro Mixto CSIC-UPV/EHU and Donostia International Physics Center (DPIC), Paseo Manual de Lardizabal 4, 20018 San Sebastian, Spain
Correspondence to: A. L. Cavalieri1F. Krausz1,3U. Heinzmann2 Correspondence and requests for materials should be addressed to A.L.C. (Email: adrian.cavalieri@mpq.mpg.de) or F.K. (Email: krausz@lmu.de) or U.H. (Email: uheinzm@physik.uni-bielefeld.de).
Abstract
Comprehensive knowledge of the dynamic behaviour of electrons in condensed-matter systems is pertinent to the development of many modern technologies, such as semiconductor and molecular electronics, optoelectronics, information processing and photovoltaics. Yet it remains challenging to probe electronic processes, many of which take place in the attosecond (1 as = 10-18 s) regime. In contrast, atomic motion occurs on the femtosecond (1 fs = 10-15 s) timescale and has been mapped in solids in real time1, 2 using femtosecond X-ray sources3. Here we extend the attosecond techniques4, 5 previously used to study isolated atoms in the gas phase to observe electron motion in condensed-matter systems and on surfaces in real time. We demonstrate our ability to obtain direct time-domain access to charge dynamics with attosecond resolution by probing photoelectron emission from single-crystal tungsten. Our data reveal a delay of approximately 100 attoseconds between the emission of photoelectrons that originate from localized core states of the metal, and those that are freed from delocalized conduction-band states. These results illustrate that attosecond metrology constitutes a powerful tool for exploring not only gas-phase systems, but also fundamental electronic processes occurring on the attosecond timescale in condensed-matter systems and on surfaces.
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