12,998 research outputs found
Specific heat and thermal conductivity of ferromagnetic magnons in Yttrium Iron Garnet
The specific heat and thermal conductivity of the insulating ferrimagnet
YFeO (Yttrium Iron Garnet, YIG) single crystal were measured
down to 50 mK. The ferromagnetic magnon specific heat shows a
characteristic dependence down to 0.77 K. Below 0.77 K, a downward
deviation is observed, which is attributed to the magnetic dipole-dipole
interaction with typical magnitude of 10 eV. The ferromagnetic magnon
thermal conductivity does not show the characteristic
dependence below 0.8 K. To fit the data, both magnetic defect
scattering effect and dipole-dipole interaction are taken into account. These
results complete our understanding of the thermodynamic and thermal transport
properties of the low-lying ferromagnetic magnons.Comment: 5 pages, 5 figure
Hertz-level Measurement of the 40Ca+ 4s 2S1/2-3d 2D5/2 Clock Transition Frequency With Respect to the SI Second through GPS
We report a frequency measurement of the clock transition of a single ^40Ca^+
ion trapped and laser cooled in a miniature ring Paul trap with 10^-15 level
uncertainty. In the measurement, we used an optical frequency comb referenced
to a Hydrogen maser, which was calibrated to the SI second through the Global
Positioning System (GPS). Two rounds of measurements were taken in May and June
2011, respectively. The frequency was measured to be 411 042 129 776 393.0(1.6)
Hz with a fractional uncertainty of 3.9{\times}10^-15 in a total averaging time
of > 2{\times}10^6 s within 32 days
Tourette syndrome in two brothers with balanced and unbalanced chromosome 12 rearrangements
published_or_final_versio
Assessment of China's virtual air pollution transport embodied in trade by using a consumption-based emission inventory
Substantial anthropogenic emissions from China have resulted in serious air pollution, and this has generated considerable academic and public concern. The physical transport of air pollutants in the atmosphere has been extensively investigated; however, understanding the mechanisms how the pollutant was transferred through economic and trade activities remains a challenge. For the first time, we quantified and tracked China's air pollutant emission flows embodied in interprovincial trade, using a multiregional input - output model framework. Trade relative emissions for four key air pollutants (primary fine particle matter, sulfur dioxide, nitrogen oxides and non-methane volatile organic compounds) were assessed for 2007 in each Chinese province. We found that emissions were significantly redistributed among provinces owing to interprovincial trade. Large amounts of emissions were embodied in the imports of eastern regions from northern and central regions, and these were determined by differences in regional economic status and environmental policy. It is suggested that measures should be introduced to reduce air pollution by integrating cross-regional consumers and producers within national agreements to encourage efficiency improvement in the supply chain and optimize consumption structure internationally. The consumption-based air pollutant emission inventory developed in this work can be further used to attribute pollution to various economic activities and final demand types with the aid of air quality models
Recursive solutions for Laplacian spectra and eigenvectors of a class of growing treelike networks
The complete knowledge of Laplacian eigenvalues and eigenvectors of complex
networks plays an outstanding role in understanding various dynamical processes
running on them; however, determining analytically Laplacian eigenvalues and
eigenvectors is a theoretical challenge. In this paper, we study the Laplacian
spectra and their corresponding eigenvectors of a class of deterministically
growing treelike networks. The two interesting quantities are determined
through the recurrence relations derived from the structure of the networks.
Beginning from the rigorous relations one can obtain the complete eigenvalues
and eigenvectors for the networks of arbitrary size. The analytical method
opens the way to analytically compute the eigenvalues and eigenvectors of some
other deterministic networks, making it possible to accurately calculate their
spectral characteristics.Comment: Definitive version accepted for publication in Physical Reivew
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Association Between Homocysteine and Vascular Calcification Incidence, Prevalence, and Progression in the MESA Cohort.
Background While elevated homocysteine has been associated with calcification in several studies, its importance as a cardiovascular risk factor remains unclear. This study examines the relationship between homocysteine and vascular and valve calcification in the MESA (Multi-ethnic Study of Atherosclerosis) cohort. Methods and Results MESA participants with baseline homocysteine measurements and cardiac computed tomography scans were included (N=6789). Baseline and follow-up assessment of vascular (coronary artery [CAC], descending thoracic aorta [DTAC]) and valve (aortic valve [AVC], mitral annular [MAC]) calcification was performed. Prevalence ratio/relative risk regression was used to assess the relationship of homocysteine with prevalent and incident calcification, and multivariable logistic regression was used to assess associations between homocysteine and calcification progression. Elevated homocysteine was associated with greater relative risk of prevalent and incident CAC and incident DTAC. We also identified a strong association between elevated homocysteine and CAC and DTAC progression. Elevated homocysteine was found to confer a >2-fold increased risk of severe CAC progression (defined as ΔCAC ≥100/year) and an ≈1.5-fold increased risk for severe DTAC progression (defined as ΔDTAC ≥100/year). Conclusions To our knowledge, this is the first study demonstrating an association between elevated homocysteine and both incidence and progression of coronary and extra-coronary vascular calcification. Our findings suggest a potential role for elevated homocysteine as a risk factor for severe vascular calcification progression. Future studies are warranted to further assess the utility of homocysteine as a biomarker for vascular calcification incidence and progression. Clinical Trial Registration https://www.clinicaltrials.gov/. Unique identifier: NCT00005487
Exact solution of mean geodesic distance for Vicsek fractals
The Vicsek fractals are one of the most interesting classes of fractals and
the study of their structural properties is important. In this paper, the exact
formula for the mean geodesic distance of Vicsek fractals is found. The
quantity is computed precisely through the recurrence relations derived from
the self-similar structure of the fractals considered. The obtained exact
solution exhibits that the mean geodesic distance approximately increases as an
exponential function of the number of nodes, with the exponent equal to the
reciprocal of the fractal dimension. The closed-form solution is confirmed by
extensive numerical calculations.Comment: 4 pages, 3 figure
Corrigendum to "Assessment of China's virtual air pollution transport embodied in trade by using a consumption-based emission inventory" published in Atmos. Chem. Phys., 15, 5443-5456, 2015
No abstract available
Evidence for the super Tonks-Girardeau gas
We provide evidence in support of a recent proposal by Astrakharchik at al.
for the existence of a super Tonks-Girardeau gas-like state in the attractive
interaction regime of quasi-one-dimensional Bose gases. We show that the super
Tonks-Giradeau gas-like state corresponds to a highly-excited Bethe state in
the integrable interacting Bose gas for which the bosons acquire hard-core
behaviour. The gas-like state properties vary smoothly throughout a wide range
from strong repulsion to strong attraction. There is an additional stable
gas-like phase in this regime in which the bosons form two-body bound states
behaving like hard-core bosons.Comment: 10 pages, 1 figure, 2 tables, additional text on the stability of the
super T-G gas-like stat
Compact Tm-doped fibre laser pumped by a 1600 nm Er-doped fibre laser designed for environmental gas sensing
In this work, the compact all-fibre linear Erbium (Er)-doped fibre lasers, operating at wavelengths of 1584 nm and 1600 nm have been described and optimized, with an aim to achieve better pumping conditions for a Thulium (Tm)-doped fibre laser. Optimization of the system has been carried out involving the studies on the different lengths of the Er-doped fibre and the different grating pairs used to achieve 173.5 mW of laser power at 1600 nm under bidirectional pumping at 980 nm. The designed Er-doped fibre laser at 1600 nm has been utilized successfully to pump longer wavelength Tm-doped fibre laser. The obtained laser power (output of Tm-doped fibre laser) of 35.5 mW at 1874 nm and 10.6 mW at 1995 nm is effective for environmental gas sensing, as these wavelengths align well with the absorption spectra of greenhouse gases such as CO2. The laser offers high power (tens of milliWatts), good directionality and a compact overall packaging with the diode pumping, making them ideally suited to ‘in-the-field’ use
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