1,523 research outputs found
New insight into cataract formation -- enhanced stability through mutual attraction
Small-angle neutron scattering experiments and molecular dynamics simulations
combined with an application of concepts from soft matter physics to complex
protein mixtures provide new insight into the stability of eye lens protein
mixtures. Exploring this colloid-protein analogy we demonstrate that weak
attractions between unlike proteins help to maintain lens transparency in an
extremely sensitive and non-monotonic manner. These results not only represent
an important step towards a better understanding of protein condensation
diseases such as cataract formation, but provide general guidelines for tuning
the stability of colloid mixtures, a topic relevant for soft matter physics and
industrial applications.Comment: 4 pages, 4 figures. Accepted for publication on Phys. Rev. Let
Effect of Hydrostatic Compression on the Energy of the 14.4-kev Gamma Ray from Fe^(57) in Iron
The energy of the recoil-free fraction of they rays emitted by nuclei bound in solids1 has been found to be affected by temperature and by electronic configuration. The latter effect has been named the "isomeric" shift. Compression of a
solid should influence the energy through both of these mechanisms. We have measured the effect of hydrostatic compression at 295°K on the energy hν of the recoil-free 14.4-kev γ rays emitted by 0.1-μsec Fe^(57) bound in metallic iron
Passage-time statistics of superradiant light pulses from Bose-Einstein condensates
We discuss the passage-time statistics of superradiant light pulses generated
during the scattering of laser light from an elongated atomic Bose-Einstein
condensate. Focusing on the early-stage of the phenomenon, we analyze the
corresponding probability distributions and their scaling behaviour with
respect to the threshold photon number and the coupling strength. With respect
to these parameters, we find quantities which only vary significantly during
the transition between the Kapitza Dirac and the Bragg regimes. A possible
connection of the present observations to Brownian motion is also discussed.Comment: Close to the version published in J. Phys.
The electron-phonon coupling strength at metal surfaces directly determined from the Helium atom scattering Debye-Waller factor
A new quantum-theoretical derivation of the elastic and inelastic scattering
probability of He atoms from a metal surface, where the energy and momentum
exchange with the phonon gas can only occur through the mediation of the
surface free-electron density, shows that the Debye-Waller exponent is directly
proportional to the electron-phonon mass coupling constant . The
comparison between the values of extracted from existing data on the
Debye-Waller factor for various metal surfaces and the values known
from literature indicates a substantial agreement, which opens the possibility
of directly extracting the electron-phonon coupling strength in quasi-2D
conducting systems from the temperature or incident energy dependence of the
elastic Helium atom scattering intensities.Comment: 14 pages, 2 figures, 1 tabl
The Electron-Phonon Coupling Constant for Single-Layer Graphene on Metal Substrates Determined from He Atom Scattering
Recent theory has demonstrated that the value of the electron-phonon coupling
strength can be extracted directly from the thermal attenuation
(Debye-Waller factor) of Helium atom scattering reflectivity. This theory is
here extended to multivalley semimetal systems and applied to the case of
graphene on different metal substrates and graphite. It is shown that
rapidly increases for decreasing graphene-substrate binding strength. Two
different calculational models are considered which produce qualitatively
similar results for the dependence of on binding strength. These
models predict, respectively, values of and 0.32 for a
hypothetical flat free-standing single-layer graphene with cyclic boundary
conditions. The method is suitable for analysis and characterization of not
only the graphene overlayers considered here, but also other layered systems
such as twisted graphene bilayers.Comment: 25 pages, 3 figures, 1 tabl
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