1,426 research outputs found
Can Social Capital be Transferred Cross the Boundary of the Real and Virtual Worlds? An Empirical Investigation of Twitter
Micro-blogs like Twitter are playing increasingly important roles in social life. Some key users of Twitter have drawn huge attention from other people. Their opinions have had significant influence on the rest of Twitter users. In other words, these people are highly reputable and have more social capital in the Twitter world. But what factors contribute to the social capital in a part of the virtual world like Twitter is still largely unknown. This paper investigates the source of social capital in the Twitter world. We identify two types of sources that influence a userâs social capital in the Twitter world: (1) inherited capital from outside the Twitter world; and (2) social activities conducted within the Twitter world. The results show that both inherited capital from outside, and activities within, the Twitter world, have positive influence on a userâs social capital in the Twitter world. Our results suggest that social capital can be transferred from the real world to the virtual one. Meanwhile the inherited social capital of a user from outside the Twitter world significantly impacts the level of activities the user undertakes in the Twitter world. For ordinary people, inherited social capital positively associates with the level of their social activities in the Twitter world. But for the most well known Twitter users, who are usually celebrities, this relationship is negative. Implications for research and practice are further discussed
Characterization of high finesse mirrors: loss, phase shifts and mode structure in an optical cavity
An extensive characterization of high finesse optical cavities used in cavity
QED experiments is described. Different techniques in the measurement of the
loss and phase shifts associated with the mirror coatings are discussed and
their agreement shown. Issues of cavity field mode structure supported by the
dielectric coatings are related to our effort to achieve the strongest possible
coupling between an atom and the cavity.Comment: 8 pages, 4 figure
III-V 4D Transistors
We fabricated for the first time vertically and laterally integrated III-V 4D transistors. III-V gate-all-around (GAA) nanowire MOSFETs with arrays show high drive current of and high transconductance of . The vertical stacking of the III-V nanowires have provided an elegant solution to the drivability bottleneck of nanowire devices and is promising for future low-power logic and RF application.Chemistry and Chemical Biolog
Towards a lightweight mobile semantic-based approach for enhancing interaction with smart objects
This work describes a semantic extension for a user-smart object interaction model based on the ECA paradigm (Event-Condition-Action). In this approach, smart objects publish their sensing (event) and action capabilities in the cloud and mobile devices are prepared to retrieve them and act as mediators to configure personalized behaviours for the objects. In this paper, the information handled by this interaction system has been shaped according several semantic models that, together with the integration of an embedded ontological and rule-based reasoner, are exploited in order to (i) automatically detect incompatible ECA rules configurations and to (ii) support complex ECA rules definitions and execution. This semantic extension may significantly improve the management of smart spaces populated with numerous smart objects from mobile personal devices, as it facilitates the configuration of coherent ECA rules
Dynamics of FitzHugh-Nagumo excitable systems with delayed coupling
Small lattices of nearest neighbor coupled excitable FitzHugh-Nagumo
systems, with time-delayed coupling are studied, and compared with systems of
FitzHugh-Nagumo oscillators with the same delayed coupling. Bifurcations of
equilibria in N=2 case are studied analytically, and it is then numerically
confirmed that the same bifurcations are relevant for the dynamics in the case
. Bifurcations found include inverse and direct Hopf and fold limit cycle
bifurcations. Typical dynamics for different small time-lags and coupling
intensities could be excitable with a single globally stable equilibrium,
asymptotic oscillatory with symmetric limit cycle, bi-stable with stable
equilibrium and a symmetric limit cycle, and again coherent oscillatory but
non-symmetric and phase-shifted. For an intermediate range of time-lags inverse
sub-critical Hopf and fold limit cycle bifurcations lead to the phenomenon of
oscillator death. The phenomenon does not occur in the case of FitzHugh-Nagumo
oscillators with the same type of coupling.Comment: accepted by Phys.Rev.
Random Field Models for Relaxor Ferroelectric Behavior
Heat bath Monte Carlo simulations have been used to study a four-state clock
model with a type of random field on simple cubic lattices. The model has the
standard nonrandom two-spin exchange term with coupling energy and a random
field which consists of adding an energy to one of the four spin states,
chosen randomly at each site. This Ashkin-Teller-like model does not separate;
the two random-field Ising model components are coupled. When , the
ground states of the model remain fully aligned. When , a
different type of ground state is found, in which the occupation of two of the
four spin states is close to 50%, and the other two are nearly absent. This
means that one of the Ising components is almost completely ordered, while the
other one has only short-range correlations. A large peak in the structure
factor appears at small for temperatures well above the transition
to long-range order, and the appearance of this peak is associated with slow,
"glassy" dynamics. The phase transition into the state where one Ising
component is long-range ordered appears to be first order, but the latent heat
is very small.Comment: 7 pages + 12 eps figures, to appear in Phys Rev
Elemental and SrâNdâPb isotope geochemistry of the Cenozoic basalts in Southeast China : insights into their mantle sources and melting processes.
We analyzed whole-rock major and trace elements and SrâNdâPb isotopes of the Cenozoic basalts in Southeast China to investigate their mantle source characteristics and melting process. These basalts are spatially associated with three extensional fault systems parallel to the coast line. After correction for the effect of olivine microlites on bulk-rock compositions and the effect of crystal fractionation, we obtained primitive melt compositions for these samples. These primitive melts show increasing SiO2, Al2O3 but decreasing FeO, MgO, TiO2, P2O5, CaO and CaO/Al2O3 from the interior to the coast. Such spatial variations of major element abundances and ratios are consistent with a combined effect of fertile source compositional variation and increasing extent and decreasing pressure of decompression melting from beneath the thick lithosphere in the interior to beneath the thin lithosphere in the coast.
These basalts are characterized by incompatible element enrichment but varying extent of isotopic depletion. This element-isotope decoupling is most consistent with recent mantle source enrichment by means of low-degree melt metasomatism that elevated incompatible element abundances without yet having adequate time for isotopic ingrowth in the mantle source regions. Furthermore, Sr and Nd isotope ratios show significant correlations with Nb/Th, Nb/La, Sr/Srâ and Eu/Euâ, which substantiates the presence of recycled upper continental crustal material in the mantle sources of these basalts.
Pb isotope ratios also exhibit spatial variation, increasing from the interior to the coastal area. The significant correlations of major element abundances with Pb isotope ratios indicate that the Pb isotope variations also result from varied extent and pressure of decompression melting. We conclude that the elevated Pb isotope ratios from the interior to coast are consistent with increasing extent of decompression melting of the incompatible element depleted mantle matrix, which hosts enriched Pb isotope compositions
Edge reconstruction in the fractional quantum Hall regime
The interplay of electron-electron interaction and confining potential can
lead to the reconstruction of fractional quantum Hall edges. We have performed
exact diagonalization studies on microscopic models of fractional quantum Hall
liquids, in finite size systems with disk geometry, and found numerical
evidence of edge reconstruction under rather general conditions. In the present
work we have taken into account effects like layer thickness and Landau level
mixing, which are found to be of quantitative importance in edge physics. Due
to edge reconstruction, additional nonchiral edge modes arise for both
incompressible and compressible states. These additional modes couple to
electromagnetic fields and thus can be detected in microwave conductivity
measurements. They are also expected to affect the exponent of electron Green's
function, which has been measured in tunneling experiments. We have studied in
this work the electric dipole spectral function that is directly related to the
microwave conductivity measurement. Our results are consistent with the
enhanced microwave conductivity observed in experiments performed on samples
with an array of antidots at low temperatures, and its suppression at higher
temperatures. We also discuss the effects of the edge reconstruction on the
single electron spectral function at the edge.Comment: 19 pages, 12 figure
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