header image
Home arrow Nature
Nature
Nature - Issue - nature.com science feeds
Nature is the international weekly journal of science: a magazine style journal that publishes full-length research papers in all disciplines of science, as well as News and Views, reviews, news, features, commentaries, web focuses and more, covering all branches of science and how science impacts upon all aspects of society and life.

Nature
  • Atom gravimeters and gravitational redshift
    Arising from: H. Müller, A. Peters & S. Chu Nature463, 926–929 (2010); Müller & Chu replyIn ref. 1 the authors present a re-interpretation of atom interferometry experiments published a decade ago. They now consider the atom interferometry experiments as a measurement of the gravitational redshift on the quantum clock operating at the Compton frequency ωC = mc2/ ≈ 2π × 3.0 × 1025 Hz, where m is the caesium (Cs) atom rest mass. They then argue that this redshift measurement compares favourably with existing as well as projected clock tests. Here we show that this interpretation is incorrect.

  • Müller, Peters & Chu reply
    Replying to: P. Wolf et al.Nature doi:10.1038/nature09340 (2010)We stand by our result. The Comment revisits an interesting issue that has been known for decades. Because it applies to all experiments, classical redshift tests and atom interferometry redshift tests are equivalent for all aspects in question.

  • Can controversies be put to REST?
    Arising from: S. K. Singh et al.Nature453, 223–227 (2008); Singh et al.replyThe contribution of REST to embryonic stem (ES) cell pluripotency has been uncertain. Two years ago, Singh et al. claimed that Rest+/− and REST knock-down ES cells expressed reduced levels of pluripotency markers, in contrast to a prior and subsequent reports. To understand the basis of this difference, we analysed the YHC334 (YHC) and RRC160 (RRC) gene-trap ES cell lines used by Singh et al., obtained directly from BayGenomics. Both REST mutant lines generated REST–βGeo fusion proteins, but expressed pluripotency genes at levels similar to appropriately matched parental wild ES cells, consistent with expression being REST–independent.

  • Singh et al. reply
    Replying to: H. F. Jørgensen & A. G. Fisher Nature 467, doi:10.1038/nature09305 (2010)Jørgensen and Fisher suggest that the discrepancy with our results could be attributable to our use of E14Tg2a (or its derivatives, such as OS25) rather than E14Tg2a.4 as the parental control line for the REST+/− cells (YHC and RRC). We have now reconfirmed our use of E14Tg2a.4 clonal cells as the control cells. Also, we have found that the YHC and RRC cells used in our experiments, originally purchased from Bay Genomics, differ from the YHC and RRC cells used by Jørgensen and Fisher with respect to pluripotency-based on alkaline phosphatase/self-renewal assays (N. Song and S.K.S., unpublished results). We are currently using other assays to confirm these observations.

  • A law in time?
    Congress must act quickly to save US stem-cell research.