39,125 research outputs found
Dynamical Self-assembly during Colloidal Droplet Evaporation Studied by in situ Small Angle X-ray Scattering
The nucleation and growth kinetics of highly ordered nanocrystal
superlattices during the evaporation of nanocrystal colloidal droplets was
elucidated by in situ time resolved small-angle x-ray scattering. We
demonstrated for the first time that evaporation kinetics can affect the
dimensionality of the superlattices. The formation of two-dimensional
nanocrystal superlattices at the liquid-air interface of the droplet has an
exponential growth kinetics that originates from interface "crushing".Comment: 4 pages, 4 figure
Hysteroscopic Essure Inserts for Permanent Contraception: Extended Follow-Up Results of a Phase III Multicenter International Study.
Multiparty Quantum Secret Sharing Based on Entanglement Swapping
A multiparty quantum secret sharing (QSS) protocol is proposed by using
swapping quantum entanglement of Bell states. The secret messages are imposed
on Bell states by local unitary operations. The secret messages are split into
several parts and each part is distributed to a party so that no action of a
subset of all the parties but their entire cooperation is able to read out the
secret messages. In addition, the dense coding is used in this protocol to
achieve a high efficiency. The security of the present multiparty QSS against
eavesdropping has been analyzed and confirmed even in a noisy quantum channel.Comment: 5 page
Chorus acceleration of radiation belt relativistic electrons during March 2013 geomagnetic storm
Abstract The recent launching of Van Allen probes provides an unprecedent opportunity to investigate variations of the radiation belt relativistic electrons. During the 17-19 March 2013 storm, the Van Allen probes simultaneously detected strong chorus waves and substantial increases in fluxes of relativistic (2 - 4.5 MeV) electrons around L = 4.5. Chorus waves occurred within the lower band 0.1-0.5fce (theelectron equatorial gyrofrequency), with a peak spectral density ∼10-4 nT 2/Hz. Correspondingly, relativistic electron fluxes increased by a factor of 102-103 during the recovery phase compared to the main phase levels. By means of a Gaussian fit to the observed chorus spectra, the drift and bounce-averaged diffusion coefficients are calculated and then used to solve a 2-D Fokker-Planck diffusion equation. Numerical simulations demonstrate that the lower-band chorus waves indeed produce such huge enhancements in relativistic electron fluxes within 15 h, fitting well with the observation. Key Points Initial RBSP correlated data of chorus waves and relativistic electron fluxes A realistic simulation to examine effect of chorus on relativistic electron flux Chorus yields huge increases inelectron flux rapidly, consistent with data
Symmetry protected Z2-quantization and quaternionic Berry connection with Kramers degeneracy
As for a generic parameter dependent hamiltonian with the time reversal (TR)
invariance, a non Abelian Berry connection with the Kramers (KR) degeneracy are
introduced by using a quaternionic Berry connection. This quaternionic
structure naturally extends to the many body system with the KR degeneracy. Its
topological structure is explicitly discussed in comparison with the one
without the KR degeneracy. Natural dimensions to have non trivial topological
structures are discussed by presenting explicit gauge fixing. Minimum models to
have accidental degeneracies are given with/without the KR degeneracy, which
describe the monopoles of Dirac and Yang. We have shown that the Yang monopole
is literally a quaternionic Dirac monopole. The generic Berry phases
with/without the KR degeneracy are introduced by the complex/quaternionic Berry
connections. As for the symmetry protected quantization of these
general Berry phases, a sufficient condition of the -quantization
is given as the inversion/reflection equivalence. Topological charges of the
SO(3) and SO(5) nonlinear -models are discussed in their relation to
the Chern numbers of the and models as well.Comment: Submitted for New J. Physics, Special issue on Topological
Insulators. 18 pages, 2 figure
Effect of iron content and potassium substitution in AFeSe (A = K, Rb, Tl) superconductors: a Raman-scattering investigation
We have performed Raman-scattering measurements on high-quality single
crystals of the superconductors KFeSe ( = 32 K),
TlKFeSe ( = 29 K), and
TlRbFeSe ( = 31 K), as well as of the
insulating compound KFeSe. To interpret our results, we have made
first-principles calculations for the phonon modes in the ordered iron-vacancy
structure of KFeSe. The modes we observe can be assigned
very well from our symmetry analysis and calculations, allowing us to compare
Raman-active phonons in the AFeSe compounds. We find a clear frequency
difference in most phonon modes between the superconducting and
non-superconducting potassium crystals, indicating the fundamental influence of
iron content. By contrast, substitution of K by Tl or Rb in
AFeSe causes no substantial frequency shift for any modes
above 60 cm, demonstrating that the alkali-type metal has little effect
on the microstructure of the FeSe layer. Several additional modes appear below
60 cm in Tl- and Rb-substituted samples, which are vibrations of heavier
Tl and Rb ions. Finally, our calculations reveal the presence of "chiral"
phonon modes, whose origin lies in the chiral nature of the
KFeSe structure.Comment: 11 pages, 10 figures and 2 table
Simple scheme for implementing the Deutsch-Jozsa algorithm in thermal cavity
We present a simple scheme to implement the Deutsch-Jozsa algorithm based on
two-atom interaction in a thermal cavity. The photon-number-dependent parts in
the evolution operator are canceled with the strong resonant classical field
added. As a result, our scheme is immune to thermal field, and does not require
the cavity to remain in the vacuum state throughout the procedure. Besides,
large detuning between the atoms and the cavity is not necessary neither,
leading to potential speed up of quantum operation. Finally, we show by
numerical simulation that the proposed scheme is equal to demonstrate the
Deutsch-Jozsa algorithm with high fidelity.Comment: 7 pages, 4 figure
Constraint on the CKM angle alpha from the experimental measurements of CP violation in B_d^0 --> pi^+ pi^- decay
In this paper, we study and try to find the constraint on the CKM angle alpha
from the experimental measurements of CP violation in B_d^0 --> pi^+ pi^-
decay, as reported very recently by BaBar and Belle Collaborations. After
considering uncertainties of the data and the ratio r of penguin over tree
amplitude, we found that strong constraint on both the CKM angle alpha and the
strong phase delta can be obtained from the measured CP asymmetries S_{pi pi}
and A_{pi pi}: (a) the ranges of 87 degrees <= alpha <= 131 degrees and 36
degrees <= delta <= 144 degrees are allowed by 1 sigma of the averaged data for
r = 0.31; (b) for Belle's result alone, the limits on alpha and delta are 104
degrees <= alpha <= 139 degrees and 42 degrees <= delta <= 138 degrees for 0.32
<= r <= 0.41; and (c) the angle alpha larger than 90 degrees is preferred.Comment: Revtex, 17 pages with 6 ps/eps figure files, new Babar data Reported
at ICHEP 2002 considere
Electric-field-induced phase transition of <001> oriented Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals
oriented 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 single crystals were poled under
different electric fields, i.e. Epoling=4 kV/cm and Epoling=13 kV/cm. In
addition to the temperature-dependent dielectric constant measurement, X-ray
diffraction was also used to identify the poling-induced phase transitions.
Results showed that the phase transition significantly depends on the poling
intensity. A weaker field (Epoling=4 kV/cm) can overcome the effect of random
internal field to perform the phase transition from rhombohedral ferroelectric
state with short range ordering (microdomain) FESRO to rhombohedral
ferroelectric state with long range ordering (macrodomain) FElRO. But the
rhombohedral ferroelectric to tetragonal ferroelectric phase transition
originating from to polarization rotation can only be induced by a
stronger field (Epoling=13 kV/cm). The sample poled at Epoling=4 kV/cm showed
higher piezoelectric constant, d33>1500 pC/N, than the sample poled at
Epoling=13 kV/cm.Comment: 7 pages, 2 figure
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