4,035 research outputs found
Nuclear Three-body Force Effect on a Kaon Condensate in Neutron Star Matter
We explore the effects of a microscopic nuclear three-body force on the
threshold baryon density for kaon condensation in chemical equilibrium neutron
star matter and on the composition of the kaon condensed phase in the framework
of the Brueckner-Hartree-Fock approach. Our results show that the nuclear
three-body force affects strongly the high-density behavior of nuclear symmetry
energy and consequently reduces considerably the critical density for kaon
condensation provided that the proton strangeness content is not very large.
The dependence of the threshold density on the symmetry energy becomes weaker
as the proton strangeness content increases. The kaon condensed phase of
neutron star matter turns out to be proton-rich instead of neutron-rich. The
three-body force has an important influence on the composition of the kaon
condensed phase. Inclusion of the three-body force contribution in the nuclear
symmetry energy results in a significant reduction of the proton and kaon
fractions in the kaon condensed phase which is more proton-rich in the case of
no three-body force. Our results are compared to other theoretical predictions
by adopting different models for the nuclear symmetry energy. The possible
implications of our results for the neutron star structure are also briefly
discussed.Comment: 15 pages, 5 figure
Guided atom laser : a new tool for guided atom optics
We present a guided atom laser. A Bose-Einstein condensate (BEC) is created
in a crossed hybrid magnetic and an elongated optical trap, which acts as a
matterwave guide. Atoms are extracted from the BEC by radio frequency (rf)
outcoupling and then guided in the horizontal optical matterwave guide. This
method allows to control the acceleration of the beam and to achieve large de
Broglie wavelength. We also measure the longitudinal energy of the guided atom
laser using atom optical elements based on a blue light barrier
The effects of dog management on Echinococcus spp. prevalence in villages on the eastern Tibetan Plateau, China
Background The pastoral area of the eastern Tibetan plateau is a very important human echinococcosis endemic region. Domestic dogs are the main definitive host for the transmission of Echinococcus granulosus sensu lato (s.1.) and E. multilocularis to humans. To control the infection risks, a national-level canine echinococcosis prevention and control program has been implemented since 2015 in Shiqu County, Sichuan, China, The objective of this investigation was to evaluate its effect on Echinococcus spp. prevalence in dogs. Methods We surveyed 69 households with 84 owned dogs, for dog keeping information in the villages of Rizha and Eduoma. A total of 105 dog fecal samples, consisting of 75 from owned dogs and 30 unknown dog fecal samples were collected between 2015 and 2017 to determine Echinococcus spp. prevalence using copro-PCR. Eight variables based on household surveys were included into a logistic regression model for significantly relevant factors to canine echinococcosis prevalence in dogs. Results The overall Echinococcus spp. copro-DNA prevalence decreased significantly in dogs from 51.2% (2015) to 20.0% (2017) in Rizha, and insignificantly from 11.5% (2016) to 4.3% (2017) in Eduoma. Echinococcus multilocularis was the most prevalent species continually detected during the entire research period, while E. granulosus was rare and not detected in 2017. Echinococcus shiquicus prevalence was as high as E. multilocularis , although only detected in 2015 in Rizha. Unleashed dog feces were mainly collected in Rizha Village in 2015. Although 93.2% of owned dogs were leashed, and the monthly praziquantel dosing rate reached 97%, E. multilocularis infection could still be detected in 11.1% of owned dogs in 2017. Monthly deworming, leashing dogs 24h per day, and the avoidance of dogs feeding on livestock viscera are significant measures to prevent canine echinococcosis infection in owned dogs. Conclusion Carrying out a canine echinococcosis prevention and control program can significantly decrease the Echinococcus prevalence. The potential contact between leashed dogs and wild small mammals is still a risk to re-infect owned dogs. This study shows that the long term application of regular dog dosing in the vast remote echinococcosis endemic areas of west China is still challenging
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Research on the performance of radiative cooling and solar heating coupling module to direct control indoor temperature
The energy crisis and environmental pollution pose great challenges to human development. Traditional vapor-compression cooling consumes abundant energy and leads to a series of environmental problems. Radiative cooling without energy consumption and environmental pollution holds great promise as the next generation cooling technology, applied in buildings mostly in indirect way. In this work, a temperature-regulating module was introduced for direct summer cooling and winter heating. Firstly, the summer experiments were conduct to investigate the radiative cooling performance of the module. And the results indicated that the maximum indoor temperature reached only 27.5 °C with the ambient temperature of 34 °C in low latitude areas and the air conditioning system was on for only about a quarter of the day. Subsequently, the winter experiments were performed to explore the performance of the module in cooling and heating modes. The results indicated that indoor temperature can reach 25 °C in the daytime without additional heat supply and about a quarter of the day didn't require heating in winter. Additionally, the transient model of the module and the building revealed that the electricity saving of 42.4% (963.5 kWh) can be achieved in cooling season with the module, and that was 63.7% (1449.1 kWh) when coupling with energy storage system. Lastly, further discussion about the challenges and feasible solutions for radiative cooling to directly combine with the buildings were provided to advance the application of radiative cooling. Furthermore, with an acceptable payback period of 8 years, the maximum acceptable incremental cost reached 26.2 $/m2. The work opens up a new avenue for the application mode of the daytime radiative cooling technology
Energy Efficiency Evaluation of Refrigeration Technologies in Combined Cooling, Heating and Power Systems
With development of absorption refrigeration technology, the cooling requirement can be met using various optional refrigeration technologies in a CCHP system, including compression refrigeration, steam double-effect absorption refrigeration, steam single-effect absorption refrigeration, flue gas absorption refrigeration and hot water absorption refrigeration, etc. As a universal criterion, the COP coefficient cannot reflect the difference in availability of driving energy for different chillers. Exergy efficiency of optional chillers in CCHP system was analyzed and compared, which can be regarded as an important reference criterion in comparison of energy efficiency. Furthermore, a new index, relative electricity saving ratio, was put forward for evaluating end energy efficiency of all kinds of chillers in a CCHP system, which indicates actual energy or electricity saving ratio for different absorption chillers with various parameters in contrast to the reference electricity-driven refrigeration scheme
Beyond Wigner's isobaric multiplet mass equation: Effect of charge-symmetry-breaking interaction and Coulomb polarization
The quadratic form of the isobaric multiplet mass equation (IMME), which was
originally suggested by Wigner and has been generally regarded as valid, is
seriously questioned by recent high-precision nuclear mass measurements. The
usual resolution to this problem is to add empirically the cubic and quartic
-terms to characterize the deviations from the IMME, but finding the
origin of these terms remains an unsolved difficulty. Based on a strategy
beyond the Wigner's first-order perturbation, we derive explicitly the cubic
and quartic -terms. These terms are shown to be generated by the effective
charge-symmetry breaking and charge-independent breaking interactions in
nuclear medium combined with the Coulomb polarization effect. Calculations for
the - and lower -shells explore a systematical emergence of the cubic
-term, suggesting a general deviation from the original IMME.
Intriguingly, the magnitude of the deviation exhibits an oscillation-like
behavior with mass number, modulated by the shell effect.Comment: 13 pages, 4 figure
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