Articles in 2010

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  • A microfluidic valve that amplifies the pressure in a fluid channel enables the realization of static microfluidic digital control logic. This in turn could enable more versatility and integration in the control of flows in ‘lab-on-a-chip’ systems.

    • James A. Weaver
    • Jessica Melin
    • Mark A. Horowitz
    Article
  • Conventionally, the states of a two-dimensional quantum ring in a high magnetic field have a well-defined spatial structure. But Coulomb repulsion between individual orbits causes oscillations in the size of this structure each time a magnetic flux-quantum enters or leaves the system. This effect has now been measured experimentally in semiconducting quantum rings.

    • A. J. M. Giesbers
    • U. Zeitler
    • J. C. Maan
    Letter
  • Turbulence usually makes plasmas more homogeneous. But in an unusual device for which the confining field is generated by a levitated half-tonne superconducting magnet, a study finds that turbulent fluctuations can actually increase the density of a plasma by driving diffusion against a density gradient.

    • A. C. Boxer
    • R. Bergmann
    • P. Woskov
    Article
  • A photonic system that shows behaviour similar to that of a violation of parity–time symmetry provides a convenient test bed to explore this and related phenomena. It could also lead to a new class of optical materials with exotic properties that exploit non-reciprocal light flow.

    • Christian E. Rüter
    • Konstantinos G. Makris
    • Detlef Kip
    Letter
  • Advances in X-ray imaging are allowing the investigation of molecular dynamics on an attosecond timescale and at angstrom-scale spatial resolution. It is now even possible to reconstruct images of the molecular orbitals, which provides us with a better understanding of how molecules respond to intense fields.

    • S. Haessler
    • J. Caillat
    • P. Salières
    Article
  • Although ‘random lasing’ in disordered optical media was first demonstrated a decade ago, the mechanism by which it occurs is disputed. New evidence of random lasing in conjugated polymers strongly supports the notion that it is generated within random optical cavities that naturally occur within disordered media.

    • A. Tulek
    • R. C. Polson
    • Z. V. Vardeny
    Article
  • Guided by a general framework for wavefront engineering, experiments demonstrate that in a light field, lines of zero intensity can be shaped into knotted and linked loops of arbitrary topology.

    • Mark R. Dennis
    • Robert P. King
    • Miles J. Padgett
    Letter
  • Hard-X-ray mirrors usually rely on total external reflection at grazing incidence, owing to the high-penetration and low X-ray reflectivity of most materials. A demonstration of the almost perfect reflectance of hard X-rays from diamond at near-normal incidence could allow the development an entirely new class of X-ray optics.

    • Yuri V. Shvyd’ko
    • Stanislav Stoupin
    • Xianrong Huang
    Letter
  • A neutron scattering study shows that the spin excitations in both pnictide- and copper-oxide-based superconductors have the same four-fold symmetry. If these excitations do indeed mediate the superconductivity, the two families of materials may be more similar than previously thought.

    • M. D. Lumsden
    • A. D. Christianson
    • D. Mandrus
    Letter
  • Mimicking even the simplest of animal behaviour, such as walking along uneven terrain, is a challenging task. A study finds that incorporating a simple but inherently chaotic pattern generator into the control system of an autonomous robot allows it to show adaptive behaviour, enabling it to successfully navigate through a complex environment.

    • Silke Steingrube
    • Marc Timme
    • Poramate Manoonpong
    Article
  • Analysis of the electrons ionized from water dimers suggests that the energy absorbed by one molecule is rapidly transmitted to the second molecule from which the electron is ejected. This process, referred to as intermolecular Coulombic decay, is a qualitatively different source of low-energy electrons to conventional direct ionization processes.

    • T. Jahnke
    • H. Sann
    • R. Dörner
    Letter
  • Measurements of the magnetic-field-dependent polarization of a one-dimensional organic quantum magnet suggest its ferroelectric behaviour is mediated by a spin–Peierls instability. Such behaviour could provide a promising new approach to the design of spin-driven ferroelectrics.

    • Fumitaka Kagawa
    • Sachio Horiuchi
    • Yoshinori Tokura
    Letter
  • Most of the low-energy electrons emitted from a material when it is subjected to ionization radiation are believed to be directly ionized secondary electrons. Coincidence measurements of the electrons ejected from water clusters suggests many are produced by a quantitatively new mechanism, known as intermolecular Coulombic decay.

    • Melanie Mucke
    • Markus Braune
    • Uwe Hergenhahn
    Letter
  • There are many two-dimensional superconductors, but only now have monolayers of metallic atoms shown superconductivity. Grown on silicon substrates, epitaxial films of lead and indium represent the thinnest superconductors possible.

    • Tong Zhang
    • Peng Cheng
    • Qi-Kun Xue
    Letter
  • Will Sesame Street, video games and robots get school children interested in science?

    Editorial