3,416 research outputs found
Web 2.0 Socail Network Sites and Facebook Marketing
The use of Web 2.0 and Social Network Sites (SNS) has become an amazing phenomenon. In fact, one of the fastest-growing arenas of the World Wide Web is the space of so-called social networking sites. Face book, Tweeter, MySpace and other Social Network Sites have huge population of users. Almost seven hundred million people use Facebook, and hundreds of million others use other social networking sites. More and more advertisers switch their marketing budget to these SNS. This study contributes to our understanding of the Web 2.0 and the use of social networking websites by examining available literature. It seeks to understand what Web 2.0 and SNS mean, the trends, its functions and how they can be leveraged for marketing purposes
Spectroscopic perspective on the interplay between electronic and magnetic properties of magnetically doped topological insulators
We combine low energy muon spin rotation (LE-SR) and soft-X-ray
angle-resolved photoemission spectroscopy (SX-ARPES) to study the magnetic and
electronic properties of magnetically doped topological insulators,
(Bi,Sb)Te. We find that one achieves a full magnetic volume fraction in
samples of (V/Cr)(Bi,Sb)Te at doping levels x 0.16.
The observed magnetic transition is not sharp in temperature indicating a
gradual magnetic ordering. We find that the evolution of magnetic ordering is
consistent with formation of ferromagnetic islands which increase in number
and/or volume with decreasing temperature. Resonant ARPES at the V edge
reveals a nondispersing impurity band close to the Fermi level as well as V
weight integrated into the host band structure. Calculations within the
coherent potential approximation of the V contribution to the spectral function
confirm that this impurity band is caused by V in substitutional sites. The
implications of our results on the observation of the quantum anomalous Hall
effect at mK temperatures are discussed
Stripe order and quasiparticle Nernst effect in cuprate superconductors
After a brief review of current ideas on stripe order in cuprate
high-temperature superconductors, we discuss the quasiparticle Nernst effect in
the cuprates, with focus on its evolution in non-superconducting stripe and
related nematic states. In general, we find the Nernst signal to be strongly
enhanced by nearby van-Hove singularities and Lifshitz transitions in the band
structure, implying that phases with translation symmetry breaking often lead
to a large quasiparticle Nernst effect due to the presence of multiple small
Fermi pockets. Open orbits may contribute to the Nernst signal as well, but do
so in a strongly anisotropic fashion. We discuss our results in the light of
recent proposals for a specific Lifshitz transition in underdoped YBCO and make
predictions for the doping dependence of the Nernst signal.Comment: 10 pages, 4 figs, article prepared for a special issue of New J Phy
Engineering the Level Structure of a Giant Artificial Atom in Waveguide Quantum Electrodynamics
Engineering light-matter interactions at the quantum level has been central
to the pursuit of quantum optics for decades. Traditionally, this has been done
by coupling emitters, typically natural atoms and ions, to quantized
electromagnetic fields in optical and microwave cavities. In these systems, the
emitter is approximated as an idealized dipole, as its physical size is orders
of magnitude smaller than the wavelength of light. Recently, artificial atoms
made from superconducting circuits have enabled new frontiers in light-matter
coupling, including the study of "giant" atoms which cannot be approximated as
simple dipoles. Here, we explore a new implementation of a giant artificial
atom, formed from a transmon qubit coupled to propagating microwaves at
multiple points along an open transmission line. The nature of this coupling
allows the qubit radiation field to interfere with itself leading to some
striking giant-atom effects. For instance, we observe strong
frequency-dependent couplings of the qubit energy levels to the electromagnetic
modes of the transmission line. Combined with the ability to in situ tune the
qubit energy levels, we show that we can modify the relative coupling rates of
multiple qubit transitions by more than an order of magnitude. By doing so, we
engineer a metastable excited state, allowing us to operate the giant transmon
as an effective lambda system where we clearly demonstrate electromagnetically
induced transparency.Comment: 12 pages, 8 figure
Be Stars in the Open Cluster NGC 6830
We report the discovery of 2 new Be stars, and re-identify one known Be star
in the open cluster NGC 6830. Eleven H-alpha emitters were discovered using the
H-alpha imaging photometry of the Palomar Transient Factory Survey. Stellar
membership of the candidates was verified with photometric and kinematic
information using 2MASS data and proper motions. The spectroscopic confirmation
was carried out by using the Shane 3-m telescope at Lick observatory. Based on
their spectral types, three H-alpha emitters were confirmed as Be stars with
H-alpha equivalent widths > -10 Angstrom. Two objects were also observed by the
new spectrograph SED-Machine on the Palomar 60 inch Telescope. The SED-Machine
results show strong H-alpha emission lines, which are consistent with the
results of the Lick observations. The high efficiency of the SED-Machine can
provide rapid observations for Be stars in a comprehensive survey in the
future.Comment: 11 pages, 8 figures, AJ in pres
Scalar Dark Matter From Theory Space
The scalar dark matter candidate in a prototypical theory space little Higgs
model is investigated. We review all details of the model pertinent to dark
matter. We perform a thermal relic density calculation including couplings to
the gauge and Higgs sectors of the model. We find two regions of parameter
space that give acceptable dark matter abundances. The first region has a dark
matter candidate with a mass of order 100 GeV, the second region has a heavy
candidate with a mass greater than about 500 GeV$. The dark matter candidate in
either region is an admixture of an SU(2) triplet and an SU(2) singlet, thereby
constituting a WIMP (weakly interacting massive particle).Comment: 18 pages, 2 figures, version to appear in PR
Exploiting the Temporal Logic Hierarchy and the Non-Confluence Property for Efficient LTL Synthesis
The classic approaches to synthesize a reactive system from a linear temporal
logic (LTL) specification first translate the given LTL formula to an
equivalent omega-automaton and then compute a winning strategy for the
corresponding omega-regular game. To this end, the obtained omega-automata have
to be (pseudo)-determinized where typically a variant of Safra's
determinization procedure is used. In this paper, we show that this
determinization step can be significantly improved for tool implementations by
replacing Safra's determinization by simpler determinization procedures. In
particular, we exploit (1) the temporal logic hierarchy that corresponds to the
well-known automata hierarchy consisting of safety, liveness, Buechi, and
co-Buechi automata as well as their boolean closures, (2) the non-confluence
property of omega-automata that result from certain translations of LTL
formulas, and (3) symbolic implementations of determinization procedures for
the Rabin-Scott and the Miyano-Hayashi breakpoint construction. In particular,
we present convincing experimental results that demonstrate the practical
applicability of our new synthesis procedure
Narrowly distributed crystal orientation in biomineral vaterite
Biominerals formed by animals provide skeletal support, and many other
functions. They were previously shown to grow by aggregation of amorphous
nanoparticles, but never to grow ion-by-ion from solution, which is a common
growth mechanism for abiotic crystals. We analyze vaterite CaCO3 multi
crystalline spicules from the solitary tunicate Herdmania momus, with
Polarization dependent Imaging Contrast PIC mapping, scanning and aberration
corrected transmission electron microscopies. The first fully quantitative PIC
mapping data, presented here, measured 0{\deg} 30{\deg} angle spreads between
immediately adjacent crystals. Such narrowly distributed crystal orientations
demonstrate that crystallinity does not propagate from one crystal to another
0{\deg} angle spreads, nor that new crystals with random orientation 90{\deg}
nucleate. There are no organic layers at the interface between crystals, hence
a new, unknown growth mechanism must be invoked, with crystal nucleation
constrained within 30{\deg}. Two observations are consistent with crystal
growth from solution: vaterite microcrystals express crystal faces, and are
smooth at the nanoscale after cryo fracture. The observation of 30{\deg} angle
spreads, lack of interfacial organic layers, and smooth fracture figures
broadens the range of known biomineralization mechanisms and may inspire novel
synthetic crystal growth strategies. Spherulitic growth from solution is one
possible mechanism consistent with all these observations.Comment: Chemistry of Materials 201
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