869 research outputs found
Does Tourist–Host Social Contact Reduce Perceived Cultural Distance?
Tourist–host social contact significantly influences the perceptions of tourists and deserves more attention from scholars in the field of tourism research. However, studies on the relationship between these two constructs are limited. To address this research gap, the present study develops and validates instruments for measuring social contact and perceived cultural distance in the context of tourism, explores the effects of social contact on perceived cultural distance, and provides implications for tourism stakeholders, including governments, tourism operators, and local communities. A survey was conducted among Hong Kong tourists traveling to Mainland China. The study had two significant findings: (1) the quality of contact negatively influences tourists’ perceived cultural distance and (2) in terms of the quantity of contact, social-oriented contacts negatively influence perceived cultural distance, whereas service-oriented contacts positively affect perceived cultural distance. Implications were provided to contribute to theoretical and empirical realms, and to guide policy formulation
Entangled Husimi distribution and Complex Wavelet transformation
Based on the proceding Letter [Int. J. Theor. Phys. 48, 1539 (2009)], we
expand the relation between wavelet transformation and Husimi distribution
function to the entangled case. We find that the optical complex wavelet
transformation can be used to study the entangled Husimi distribution function
in phase space theory of quantum optics. We prove that the entangled Husimi
distribution function of a two-mode quantum state |phi> is just the modulus
square of the complex wavelet transform of exp{-(|eta|^2)/2} with phi(eta)being
the mother wavelet up to a Gaussian function.Comment: 7 page
Observational constraints on Cosmic Reionization
Recent observations have set the first constraints on the epoch of
reionization (EoR), corresponding to the formation epoch of the first luminous
objects. Studies of Gunn-Peterson (GP) absorption, and related phenomena,
suggest a qualitative change in the state of the intergalactic medium (IGM) at
, indicating a rapid increase in the neutral fraction of the IGM,
from , perhaps up to
0.1, at . Conversely, transmission spikes in the GP trough, and the
evolution of the \lya galaxy luminosity function indicate at
, while the large scale polarization of the cosmic microwave
background (CMB) implies a significant ionization fraction extending to higher
redshifts, . The results suggest that reionization is less an
event than a process, with the process beginning as early as , and
with the 'percolation', or 'overlap' phase ending at . The data are
consistent with low luminosity star forming galaxies as being the dominant
sources of reionizing photons. Low frequency radio telescopes currently under
construction should be able to make the first direct measurements of HI 21cm
emission from the neutral IGM during the EoR, and upcoming measurements of
secondary CMB temperature anisotropy will provide fine details of the dynamics
of the reionized IGM.Comment: to appear in ARAA 2006, vol 44, page 415-462; latex. 84 pages. 15 fi
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Damage in unidirectional graphite/epoxy laminates containing a circular hole
In this paper, a damage mechanics model is described for determining progressive damage processes in unidirectional graphite/epoxy composite plates containing a central hole subjected to off-axis uniaxial tension. The inelastic behavior of these composite materials is attributed to the irreversible thermodynamics processes involving energy dissipation and stiffness variation caused by damage initiation and accumulation, The mechanical response of the composites is investigated by using a nonlinear finite element procedure formulated with a set of damage coupled constitutive equations. Separate damage criteria are derived for fiber failure and for matrix or fiber/matrix interaction failure in unidirectional composites. Validation of the damage model is achieved by comparing the numerical prediction and experimental data obtained from a Moire interferometry technique. It has been found that failure of the composite material near the hole region takes the form of an extensive damage zone. The macrocrack initiates at the material point near the hole boundary with a high damage value and propagates along the direction of damage zone extension. Preliminary results indicate that the proposed damage model is an effective method of studying progressive failure behavior of unidirectional composite laminates containing a circular hole and can be readily extended to examine the damage response of composite structures
Physiologically regulated transgenic ABCA1 does not reduce amyloid burden or amyloid‐beta peptide levels in vivo
J Lipid Res. 2007 Apr;48(4):914-23. Epub 2007 Jan 18.
Physiologically regulated transgenic ABCA1 does not reduce amyloid burden or amyloid-beta peptide levels in vivo.
Hirsch-Reinshagen V, Chan JY, Wilkinson A, Tanaka T, Fan J, Ou G, Maia LF, Singaraja RR, Hayden MR, Wellington CL.
Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, Canada.
Abstract
ABCA1-deficient mice have low levels of poorly lipidated apolipoprotein E (apoE) and exhibit increased amyloid load. To test whether excess ABCA1 protects from amyloid deposition, we crossed APP/PS1 mice to ABCA1 bacterial artificial chromosome (BAC) transgenic mice. Compared with wild-type animals, the ABCA1 BAC led to a 50% increase in cortical ABCA1 protein and a 15% increase in apoE abundance, demonstrating that this BAC supports modest ABCA1 overexpression in brain. However, this was observed only in animals that do not deposit amyloid. Comparison of ABCA1/APP/PS1 mice with APP/PS1 controls revealed no differences in levels of brain ABCA1 protein, amyloid, Abeta, or apoE, despite clear retention of ABCA1 overexpression in the livers of these animals. To further investigate ABCA1 expression in the amyloid-containing brain, we then compared ABCA1 mRNA and protein levels in young and aged cortex and cerebellum of APP/PS1 and ABCA1/APP/PS1 animals. Compared with APP/PS1 controls, aged ABCA1/APP/PS1 mice exhibited increased ABCA1 mRNA, but not protein, selectively in cortex. Additionally, ABCA1 mRNA levels were not increased before amyloid deposition but were induced only in the presence of extensive Abeta and amyloid levels. These data suggest that an induction of ABCA1 expression may be associated with late-stage Alzheimer's neuropathology.
PMID: 17235115 [PubMed - indexed for MEDLINE
Enhancing gravitational wave astronomy with galaxy catalogues
Joint gravitational wave (GW) and electromagnetic (EM) observations, as a key
research direction in multi-messenger astronomy, will provide deep insight into
the astrophysics of a vast range of astronomical phenomena. Uncertainties in
the source sky location estimate from gravitational wave observations mean
follow-up observatories must scan large portions of the sky for a potential
companion signal. A general frame of joint GW-EM observations is presented by a
multi-messenger observational triangle. Using a Bayesian approach to
multi-messenger astronomy, we investigate the use of galaxy catalogue and host
galaxy information to reduce the sky region over which follow-up observatories
must scan, as well as study its use for improving the inclination angle
estimates for coalescing binary compact objects. We demonstrate our method
using a simulated neutron stars inspiral signal injected into simulated
Advanced detectors noise and estimate the injected signal sky location and
inclination angle using the Gravitational Wave Galaxy Catalogue. In this case
study, the top three candidates in rank have , and posterior
probability of being the host galaxy, receptively. The standard deviation of
cosine inclination angle (0.001) of the neutron stars binary using
gravitational wave-galaxy information is much smaller than that (0.02) using
only gravitational wave posterior samples.Comment: Proceedings of the Sant Cugat Forum on Astrophysics. 2014 Session on
'Gravitational Wave Astrophysics
Extensive translation of circular RNAs driven by N6-methyladenosine
Extensive pre-mRNA back-splicing generates numerous circular RNAs (circRNAs) in human transcriptome. However, the biological functions of these circRNAs remain largely unclear. Here we report that N6-methyladenosine (m6A), the most abundant base modification of RNA, promotes efficient initiation of protein translation from circRNAs in human cells. We discover that consensus m6A motifs are enriched in circRNAs and a single m6A site is sufficient to drive translation initiation. This m6A-driven translation requires initiation factor eIF4G2 and m6A reader YTHDF3, and is enhanced by methyltransferase METTL3/14, inhibited by demethylase FTO, and upregulated upon heat shock. Further analyses through polysome profiling, computational prediction and mass spectrometry reveal that m6A-driven translation of circRNAs is widespread, with hundreds of endogenous circRNAs having translation potential. Our study expands the coding landscape of human transcriptome, and suggests a role of circRNA-derived proteins in cellular responses to environmental stress
Geometric effects on T-breaking in p+ip and d+id superconductors
Superconducting order parameters that change phase around the Fermi surface
modify Josephson tunneling behavior, as in the phase-sensitive measurements
that confirmed order in the cuprates. This paper studies Josephson coupling
when the individual grains break time-reversal symmetry; the specific cases
considered are and , which may appear in SrRuO and
NaCoO(HO) respectively. -breaking order parameters
lead to frustrating phases when not all grains have the same sign of
time-reversal symmetry breaking, and the effects of these frustrating phases
depend sensitively on geometry for 2D arrays of coupled grains. These systems
can show perfect superconducting order with or without macroscopic
-breaking. The honeycomb lattice of superconducting grains has a
superconducting phase with no spontaneous breaking of but instead power-law
correlations. The superconducting transition in this case is driven by binding
of fractional vortices, and the zero-temperature criticality realizes a
generalization of Baxter's three-color model.Comment: 8 page
Multiwavelength Study of M8.9/3B Solar Flare from AR NOAA 10960
We present a multi-wavelength analysis of a long duration white-light solar
flare (M8.9/3B) event that occurred on 4 June 2007 from NOAA AR 10960. The
flare was observed by several spaceborne instruments, namely SOHO/MDI,
Hinode/SOT, TRACE and STEREO/SECCHI. The flare was initiated near a small,
positive-polarity, satellite sunspot at the centre of the AR, surrounded by
opposite-polarity field regions. MDI images of the AR show considerable amount
of changes in a small positive-polarity sunspot of delta configuration during
the flare event. SOT/G-band (4305 A) images of the sunspot also suggest the
rapid evolution of the positive-polarity sunspot with highly twisted penumbral
filaments before the flare event, which were oriented in the counterclockwise
direction. It shows the change in orientation and also remarkable disappearance
of twisted penumbral filaments (~35-40%) and enhancement in umbral area
(~45-50%) during the decay phase of the flare. TRACE and SECCHI observations
reveal the successive activations of two helical twisted structures associated
with this sunspot, and the corresponding brightening in the chromosphere as
observed by the time-sequence images of SOT/Ca II H line (3968 A). The
secondary-helical twisted structure is found to be associated with the M8.9
flare event. The brightening starts 6-7 min prior to the flare maximum with the
appearance of secondary helical-twisted structure. The flare intensity
maximizes as this structure moves away from the AR. This twisted flux-tube
associated with the flare triggering, is found to be failed in eruption. The
location of the flare is found to coincide with the activation site of the
helical twisted structures. We conclude that the activations of successive
helical twists in the magnetic flux tubes/ropes plays a crucial role in the
energy build-up process and triggering of M-class solar flare without a CME.Comment: 22 pages, 12 figures, Accepted for Publication in Solar Physic
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