560 research outputs found
A brief review of topological photonics in one, two, and three dimensions
Topological photonics has attracted increasing attention in recent years due
to the unique opportunities it provides to manipulate light in a robust way
immune to disorder and defects. Up to now, diverse photonic platforms, rich
physical mechanisms and fruitful device applications have been proposed for
topological photonics, including one-way waveguide, topological lasing,
topological nanocavity, Dirac and Weyl points, Fermi arcs, nodal lines, etc. In
this review, we provide an introduction to the field of topological photonics
through the lens of topological invariants and bulk-boundary correspondence in
one, two, and three dimensions, which may not only offer a unified
understanding about the underlying robustness of diverse and distinct
topological phenomena of light, but could also inspire further developments by
introducing new topological invariants and unconventional bulk-boundary
correspondence to the research of topological photonics.Comment: 29 pages, 12 figures, 341 reference
Magnetic properties of Gd_xY_{1-x}Fe_2Zn_{20}: dilute, large, moments in a nearly ferromagnetic Fermi liquid
Single crystals of the dilute, rare earth bearing, pseudo-ternary series,
Gd_xY_{1-x}Fe_2Zn_{20} were grown out of Zn-rich solution. Measurements of
magnetization, resistivity and heat capacity on Gd_xY_{1-x}Fe_2Zn_{20} samples
reveal ferromagnetic order of Gd^{3+} local moments across virtually the whole
series (). The magnetic properties of this series, including the
ferromagnetic ordering, the reduced saturated moments at base temperature, the
deviation of the susceptibilities from Curie-Weiss law and the anomalies in the
resistivity, are understood within the frame work of dilute,
moments (Gd^{3+}) embedded in a nearly ferromagnetic Fermi liquid
(YFe_2Zn_{20}). The s-d model is employed to further explain the variation of
with x as well as the temperature dependences of of the
susceptibilities
Quasi-Periodic Occultation by a Precessing Accretion Disk and Other Variabilities of SMC X-1
We have investigated the variability of the binary X-ray pulsar, SMC X-1, in
data from several X-ray observatories. We confirm the ~60-day cyclic variation
of the X-ray flux in the long-term monitoring data from the RXTE and CGRO
observatories. X-ray light curves and spectra from the ROSAT, Ginga, and ASCA
observatories show that the uneclipsed flux varies by as much as a factor of
twenty between a high-flux state when 0.71 second pulses are present and a
low-flux state when pulses are absent. In contrast, during eclipses when the
X-rays consist of radiation scattered from circumsource matter, the fluxes and
spectra in the high and low states are approximately the same. These
observations prove that the low state of SMC X-1 is not caused by a reduction
in the intrinsic luminosity of the source, or a spectral redistribution
thereof, but rather by a quasi-periodic blockage of the line of sight, most
likely by a precessing tilted accretion disk. In each of two observations in
the midst of low states a brief increase in the X-ray flux and reappearance of
0.71 second pulses occurred near orbital phase 0.2. These brief increases
result from an opening of the line of sight to the pulsar that may be caused by
wobble in the precessing accretion disk. The records of spin up of the neutron
star and decay of the binary orbit are extended during 1991-1996 by
pulse-timing analysis of ROSAT, ASCA, and RXTE PCA data. The pulse profiles in
various energy ranges from 0.1 to >21 keV are well represented as a combination
of a pencil beam and a fan beam. Finally, there is a marked difference between
the power spectra of random fluctuations in the high-state data from the RXTE
PCA below and above 3.4 keV. Deviation from the fitted power law around 0.06 Hz
may be QPO.Comment: Accepted to ApJ. 33 pages including 11 figure
Impact of Taiwan open policy on Chinese tourist satisfaction
The Taiwan government has imposed a daily visitation quota with strict regulations on Chinese visitor travel modes, length of stay, and visa authorizations since July 2008. This highly controlled scheme was an attempt to maintain service quality on top of security and political considerations. The purpose of this study is to provide in-depth analysis regarding the Chinese tourist satisfaction over time under different travel modes. The results indicated that package tour (PT) visitors generally gave higher satisfaction scores than free and independent travel (FIT) visitors. However, PT visitors demonstrated a decreased level of satisfaction on their tour arrangements of hotels, meals, itineraries. Addressing safety and
environmental issues is the priority task in order to provide quality travel services
Prediction of Anisotropic Single-Dirac-Cones in BiSb Thin Films
The electronic band structures of BiSb thin films can be
varied as a function of temperature, pressure, stoichiometry, film thickness
and growth orientation. We here show how different anisotropic
single-Dirac-cones can be constructed in a BiSb thin film for
different applications or research purposes. For predicting anisotropic
single-Dirac-cones, we have developed an iterative-two-dimensional-two-band
model to get a consistent inverse-effective-mass-tensor and band-gap, which can
be used in a general two-dimensional system that has a non-parabolic dispersion
relation as in a BiSb thin film system
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Dairy consumption and cardiometabolic diseases: systematic review and updated meta-analyses of prospective cohort studies
Purpose of Review Dairy products contain both beneficial and harmful nutrients in relation to cardiometabolic diseases. Here, we
provide the latest scientific evidence regarding the relationship between dairy products and cardiometabolic diseases by
reviewing the literature and updating meta-analyses of observational studies.
Recent Findings We updated our previous meta-analyses of cohort studies on type 2 diabetes, coronary heart disease (CHD), and
stroke with nine studies and confirmed previous results. Total dairy and low-fat dairy (per 200 g/d) were inversely associated with
a 3–4% lower risk of diabetes. Yogurt was non-linearly inversely associatedwith diabetes (RR = 0.86, 95%CI: 0.83–0.90 at 80 g/
d). Total dairy and milk were not associated with CHD (RR~1.0). An increment of 200 g of daily milk intake was associated with
an 8% lower risk of stroke.
Summary The latest scientific evidence confirmed neutral or beneficial associations between dairy products and risk of cardiometabolic
diseases
Entropy of a Kerr-de Sitter black hole due to arbitrary spin fields
The Newman-Penrose formalism is used to derive the Teukolsky master equations
controlling massless scalar, neutrino, electromagnetic, gravitino, and
gravitational field perturbations of the Kerr-de Sitter spacetime. Then the
quantum entropy of a non-extreme Kerr-de Sitter black hole due to arbitrary
spin fields is calculated by the improved thin-layer brick wall model. It is
shown that the subleading order contribution to the entropy is dependent on the
square of the spins of particles and that of the specific angular momentum of
black holes as well as the cosmological constant. The logarithmic correction of
the spins of particles to the entropy relies on the rotation of the black hole
and the effect of the cosmological constant.Comment: 28 pages, two figures, Revtex4.0. Final revised version to appear in
PR
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Protein-coding variants implicate novel genes related to lipid homeostasis contributing to body-fat distribution.
Body-fat distribution is a risk factor for adverse cardiovascular health consequences. We analyzed the association of body-fat distribution, assessed by waist-to-hip ratio adjusted for body mass index, with 228,985 predicted coding and splice site variants available on exome arrays in up to 344,369 individuals from five major ancestries (discovery) and 132,177 European-ancestry individuals (validation). We identified 15 common (minor allele frequency, MAF ≥5%) and nine low-frequency or rare (MAF <5%) coding novel variants. Pathway/gene set enrichment analyses identified lipid particle, adiponectin, abnormal white adipose tissue physiology and bone development and morphology as important contributors to fat distribution, while cross-trait associations highlight cardiometabolic traits. In functional follow-up analyses, specifically in Drosophila RNAi-knockdowns, we observed a significant increase in the total body triglyceride levels for two genes (DNAH10 and PLXND1). We implicate novel genes in fat distribution, stressing the importance of interrogating low-frequency and protein-coding variants
Variation of the magnetic ordering in GdTZn (T= Fe, Ru, Os, Co, Rh and Ir) and its correlation with the electronic structure of isostructural YTZn
Magnetization, resistivity and specific heat measurements were performed on
the solution-grown, single crystals of six GdTZn (T = Fe, Ru, Os,
Co, Rh and Ir) compounds, as well as their Y analogues. For the Gd compounds,
the Fe column members manifest a ferromagnetic (FM) ground state (with an
enhanced Curie temperature, , for T = Fe and Ru), whereas the
Co column members manifest an antiferromagnetic (AFM) ground state.
Thermodynamic measurements on the YTZn revealed that the enhanced
for GdFeZn and GdRuZn can be understood
within the framework of Heisenberg moments embedded in a nearly ferromagnetic
Fermi liquid. Furthermore, electronic structure calculations indicate that this
significant enhancement is due to large, close to the Stoner FM criterion,
transition metal partial density of states at Fermi level, whereas the change
of FM to AFM ordering is associated with filling of electronic states with two
additional electrons per formula unit. The degree of this sensitivity is
addressed by the studies of the pseudo-ternary compounds
Gd(FeCo)Zn and Y(FeCo)Zn which
clearly reveal the effect of 3d band filling on their magnetic properties.Comment: 32 pages, 28 figure
Distinct Properties of Hexameric but Functionally Conserved Mycobacterium tuberculosis Transcription-Repair Coupling Factor
Transcription coupled nucleotide excision repair (TC-NER) is involved in correcting UV-induced damage and other road-blocks encountered in the transcribed strand. Mutation frequency decline (Mfd) is a transcription repair coupling factor, involved in repair of template strand during transcription. Mfd from M. tuberculosis (MtbMfd) is 1234 amino-acids long harboring characteristic modules for different activities. Mtbmfd complemented Escherichia coli mfd (Ecomfd) deficient strain, enhanced survival of UV irradiated cells and increased the road-block repression in vivo. The protein exhibited ATPase activity, which was stimulated ∼1.5-fold in the presence of DNA. While the C-terminal domain (CTD) comprising amino acids 630 to 1234 showed ∼2-fold elevated ATPase activity than MtbMfd, the N-terminal domain (NTD) containing the first 433 amino acid residues was able to bind ATP but deficient in hydrolysis. Overexpression of NTD of MtbMfd led to growth defect and hypersensitivity to UV light. Deletion of 184 amino acids from the C-terminal end of MtbMfd (MfdΔC) increased the ATPase activity by ∼10-fold and correspondingly exhibited efficient translocation along DNA as compared to the MtbMfd and CTD. Surprisingly, MtbMfd was found to be distributed in monomer and hexamer forms both in vivo and in vitro and the monomer showed increased susceptibility to proteases compared to the hexamer. MfdΔC, on the other hand, was predominantly monomeric in solution implicating the extreme C-terminal region in oligomerization of the protein. Thus, although the MtbMfd resembles EcoMfd in many of its reaction characteristics, some of its hitherto unknown distinct properties hint at its species specific role in mycobacteria during transcription-coupled repair
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