1,768 research outputs found
Prevalence of the metabolic syndrome in Chinese adolescents
Since national figures on the occurrence of metabolic syndrome among Chinese adolescents are lacking, this study aims to estimate its prevalence and distribution among Chinese youngsters. The 2002 China National Nutrition and Health Survey is a nationally representative cross-sectional study. Applying the criteria for US adolescents, we estimated the prevalence of metabolic syndrome among 2761 adolescents aged 15 to 19 years. The prevalence of metabolic syndrome among Chinese adolescents overall was 3·7% (10% in US adolescents). It was 35·2 %, 23·4% and 2·3% among adolescents who were overweight (BMI 85th percentile and one or two parent(s) with metabolic syndrome, the prevalence was 46·4 %. A total of 96% of overweight adolescents had at least one and 74·1% overweight adolescents had at least two abnormalities of metabolic syndrome. Based on these figures, it is estimated that more than three million Chinese adolescents have metabolic syndrome. Both overweight and metabolic syndrome prevalence among adolescents are still relatively low in China, but the prevalence of metabolic syndrome among Chinese overweight adolescents is similar to those living in the USA
Evaluation of Ultimate Strength of Reinforced Concrete Beams Strengthened with FRP Sheets under Torsion
The ultimate torque of reinforced concrete (RC) members strengthened with fiber
reinforced polymer (FRP) sheets does not only depend on the torque of RC members, but also
on the FRP contribution to the torque. For structural design, predicting the accurate torsional
capacity of the strengthened beams is considerably important. Three existing models for
calculating the ultimate torsional moment of RC beams and two existing models for computing
the FRP contribution to the ultimate torque are described and combined. Based on an
experimental database collected from existing literature, six combinations were discussed and
evaluated from the calculative values compared with the experimental results. The comparison
shows that the combination of ACI 318 and fib Bulletin 14 models (Group 2), as well as
Chinese and Ghobarah models (Group 6), can reasonably and accurately predict the ultimate
torque of beams strengthened with FRP sheet. Furthermore, the ultimate torque of six boxsection
beams strengthened with fully wrapping or U-wrap calculated by the Group 6 shows
closely to the experimental results
Linear Optical Quantum Computing in a Single Spatial Mode
We present a scheme for linear optical quantum computing using time-bin
encoded qubits in a single spatial mode. We show methods for single-qubit
operations and heralded controlled phase (CPhase) gates, providing a sufficient
set of operations for universal quantum computing with the
Knill-Laflamme-Milburn scheme. Our scheme is suited to available photonic
devices and ideally allows arbitrary numbers of qubits to be encoded in the
same spatial mode, demonstrating the potential for time-frequency modes to
dramatically increase the quantum information capacity of fixed spatial
resources. As a test of our scheme, we demonstrate the first entirely single
spatial mode implementation of a two-qubit quantum gate and show its operation
with an average fidelity of 0.84+-0.07.Comment: 5 pages, 4 figures. Updated to be consistent with the published
versio
Analyzing key influences of tourists’ acceptance of online reviews in travel decisions
Purpose: This study aims to examine what influence travelers’ adoption of online reviews, and whether the online reviews will influence their travel planning decisions.
Design/methodology/approach: Data was collected from 193 respondents from eWOM websites and analyzed using structural equation modeling.
Findings: Our results revealed that eWOM has a significant influence on travel decisions. Furthermore, travelers were willing to adopt information from eWOM and this information was useful in their travel planning and decisions. Gender and time spent on online reviews were found to affect travel planning and decisions. Travelers also found that the reviews and issues raised in eWOM had credibility and were of good quality.
Research limitations/implications: Our study was not able to incorporate all factors which may be relevant to this study and so further theoretical development may be necessary to develop the conceptual model. The sample size, while adequate, can be expanded further.
Practical implications: Operators and administrators of eWOM can use these findings to develop more user-friendly interfaces so that more positive reviews and sales can be generated.
Social implications: Our results showed that travelers who adopt the information in eWOM will, in turn, use eWOM in their travel planning. This confirms the importance of eWOM and travelers in general will translate their pre-travel decisions into actual travel planning.
Originality/value: This research extended existing eWOM and information system adoption studies and focused on the travel planning context. This research validated the significant roles of eWOM argument quality and credibility in predicting the information usefulness of eWOM
A high-speed tunable beam splitter for feed-forward photonic quantum information processing
We realize quantum gates for path qubits with a high-speed,
polarization-independent and tunable beam splitter. Two electro-optical
modulators act in a Mach-Zehnder interferometer as high-speed phase shifters
and rapidly tune its splitting ratio. We test its performance with heralded
single photons, observing a polarization-independent interference contrast
above 95%. The switching time is about 5.6 ns, and a maximal repetition rate is
2.5 MHz. We demonstrate tunable feed-forward operations of a single-qubit gate
of path-encoded qubits and a two-qubit gate via measurement-induced interaction
between two photons
Quantum efficiency measurement of single photon detectors using photon pairs generated in optical fibers
Using the correlated signal and idler photon pairs generated in a dispersion
shifted fiber by a pulsed pump, we measure the quantum efficiency of a
InGaAs/InP avalanche photodiode-based single photon detector. Since the
collection efficiency of photon pairs is a key parameter to correctly deduce
the quantum efficiency, we carefully characterize the collection efficiency by
studying correlation dependence of photon pairs upon the spectra of pump,
signal and idler photons. This study allows us to obtain quantum efficiency of
the single photon detector by using photon pairs with various kinds of
bandwidths.Comment: 21pages, 6figures, 4tables, accepted for publication in J. Opt. Soc.
Am.
Reducing multi-photon rates in pulsed down-conversion by temporal multiplexing
We present a simple technique to reduce the emission rate of higher-order
photon events from pulsed spontaneous parametric down-conversion. The technique
uses extra-cavity control over a mode locked ultrafast laser to simultaneously
increase repetition rate and reduce the energy of each pulse from the pump
beam. We apply our scheme to a photonic quantum gate, showing improvements in
the non-classical interference visibility for 2-photon and 4-photon
experiments, and in the quantum-gate fidelity and entangled state production in
the 2-photon case.Comment: 8 pages, 6 figure
De Broglie Wavelength of a Nonlocal Four-Photon
Superposition is one of the most distinct features of quantum theory and has
been demonstrated in numerous realizations of Young's classical double-slit
interference experiment and its analogues. However, quantum entanglement - a
significant coherent superposition in multiparticle systems - yields phenomena
that are much richer and more interesting than anything that can be seen in a
one-particle system. Among them, one important type of multi-particle
experiments uses path-entangled number-states, which exhibit pure higher-order
interference and allow novel applications in metrology and imaging such as
quantum interferometry and spectroscopy with phase sensitivity at the
Heisenberg limit or quantum lithography beyond the classical diffraction limit.
Up to now, in optical implementations of such schemes lower-order interference
effects would always decrease the overall performance at higher particle
numbers. They have thus been limited to two photons. We overcome this
limitation and demonstrate a linear-optics-based four-photon interferometer.
Observation of a four-particle mode-entangled state is confirmed by
interference fringes with a periodicity of one quarter of the single-photon
wavelength. This scheme can readily be extended to arbitrary photon numbers and
thus represents an important step towards realizable applications with
entanglement-enhanced performance.Comment: 19 pages, 4 figures, submitted on November 18, 200
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