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Whenever the European enterprise takes another step forward, its leaders say there will be no change. The European Communities' research policy is just one illustration that such a doctrine does not make sense.
One of President Bill Clinton's early decisions was to lift the ban on federally supported research on human fetal tissue. Under what circumstances can research on this material be justified?
The general enthusiasm for the fortieth anniversary of the structure of DNA should not blind us to a few blemishes on the otherwise fair face of molecular biology.
THE recent discovery1 of superconductivity below a transition temperature (Tc) of 94 K in HgBa2CuO4+δ has extended the repertoire of high-Tc superconductors containing copper oxide planes embedded in suitably structured (layered) materials. Previous experience with similar compounds containing bismuth and thallium instead of mercury suggested that even higher transition temperatures might be achieved in mercury-based compounds with more than one CuO2 layer per unit cell. Here we provide support for this conjecture, with the discovery of superconductivity above 130 K in a material containing HgBa2Ca2Cu3O1+x (with three CuO2 layers per unit cell), HgBa2CaCu2O6+x (with two CuO2 layers) and an ordered superstructure comprising a defined sequence of the unit cells of these phases. Both magnetic and resistivity measurements confirm a maximum transition temperature of ∼ 133 K, distinctly higher than the previous established record value of 125–127 K observed in Tl2Ba2Ca2Cu3O10 (refs 2,3).
Work published over the past month provides insight into the mechanism of genomic imprinting in mice and the possible phenotypic consequences of imprinting in humans.
Featured this week — antibody purification kits, a diode-array detector for liquid chromatography, software for chromatography applications, columns, media and a collection of catalogues for one-stop shopping.
