| 4071. |
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| 4072. |
- Stoller, R. E., et al.
(författare)
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Impact of Short-Range Forces on Defect Production from High Energy Collisions
- 2016
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Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9618 .- 1549-9626. ; 12:6, s. 2871-2879
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Tidskriftsartikel (refereegranskat)abstract
- Primary radiation damage formation in solid materials typically involves collisions between atoms that have up to a few hundred keV of kinetic energy. Dining these collisions, the-distance between two colliding atoms can approach 0.05 nm. At such small atomic separations, force fields fitted-to equilibrium properties tend to significantly underestimate the potential-energy-of the colliding dieter. To enable molecular dynamics simulations of high-energy collisions, it is common practice to use a screened Coulomb, force field to describe the interactions and to smoothly join this to the equilibrium force field at a suitable interatomic spacing. However, there is,no accepted standard method for choosing the parameters used in the joining process, and our results prove that defect production is sensitive to how the force field's are linked. A new procedure is presented that involves the use of ab initio calculations to,determine the magnitude and spatial dependence of the pair interactions at intermediate distances, along with systematic criteria for choosing the joining parameters. Results are presented for the case of nickel, which demonstrate the use and validity of the procedure.
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| 4073. |
- Stolte, W.C., et al.
(författare)
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The K-shell Auger decay of atomic oxygen
- 1997
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - 0953-4075. ; 30:20, s. 4489-4497
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Tidskriftsartikel (refereegranskat)abstract
- Relative photoionization cross sections for O+ and O2+ produced by the Auger decay of a 1s hole in atomic oxygen were measured by using synchrotron radiation between 525 and 553 eV. Energies and quantum defects of the members of the two Rydberg series converging to [1s]2s22p4(4P) and [1s]2s22p4(2P) ionization thresholds were determined. In addition, the 2P and 4P ionization thresholds were calculated from the two Rydberg series. The 182 meV resolution of the monochromator allowed a detailed study over both thresholds revealing evidence for post-collision interaction and allowing a comparison of the ionization continuum above both 2P and 4P thresholds with that of the ionization continuum above the Ar L2 and L3 edges. This comparison indicates that the lifetimes of the Ar(2p) and O(1s) hole states are approximately the same.
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| 4074. |
- Strakova, A., et al.
(författare)
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Recurrent horizontal transfer identifies mitochondrial positive selection in a transmissible cancer
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Autonomous replication and segregation of mitochondrial DNA (mtDNA) creates the potential for evolutionary conflict driven by emergence of haplotypes under positive selection for 'selfish' traits, such as replicative advantage. However, few cases of this phenomenon arising within natural populations have been described. Here, we survey the frequency of mtDNA horizontal transfer within the canine transmissible venereal tumour (CTVT), a contagious cancer clone that occasionally acquires mtDNA from its hosts. Remarkably, one canine mtDNA haplotype, A1d1a, has repeatedly and recently colonised CTVT cells, recurrently replacing incumbent CTVT haplotypes. An A1d1a control region polymorphism predicted to influence transcription is fixed in the products of an A1d1a recombination event and occurs somatically on other CTVT mtDNA backgrounds. We present a model whereby 'selfish' positive selection acting on a regulatory variant drives repeated fixation of A1d1a within CTVT cells.
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| 4075. |
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| 4076. |
- Su, B., et al.
(författare)
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Estimated changes in different forms of precipitation (snow, sleet, and rain) across China: 1961–2016
- 2022
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Ingår i: Atmospheric Research. - : Elsevier BV. - 0169-8095. ; 270
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Tidskriftsartikel (refereegranskat)abstract
- Different forms of precipitation (snow, sleet, and rain) have divergent effects on the Earth's surface water and energy fluxes. Therefore, discriminating between these forms, and exploring their climatology and variations are of significant importance, especially under a changing climate. In this study, a state-of-the-art parameterization scheme with wet-bulb temperature (Tw), relative humidity (RH), surface air pressure, and elevation as inputs was used to estimate the climatologies and trends of the different forms of precipitation and their temperature thresholds across China mainland from 1961 to 2016. The results indicate that on average, only 9.6% and 0.8% of the total precipitation (602.9 mm) over China during 1961–2016 occurred as snow and sleet. The trends of the different forms of precipitation varied greatly from region to region and from season to season. The regionally averaged annual precipitation, rainfall, and snowfall across China significantly increased at rates of 11.4 mm/decade, 11.0 mm/decade, and 1.0 mm/decade, respectively, whereas the annual sleet decreased at a rate of −0.3 mm/decade. The region-wide snow (rain) fraction significantly increased (decreased) in Northwestern China (NWC) and Northern China (NC) but significantly decreased (increased) on the Tibetan Plateau (TP). Given the heterogeneous RH and complex topography, the Tw values at which snow-sleet and sleet-rain occurred with equal frequency—that is, Ts and Tr, varied significantly across China, averaging 0.1 °C and 0.3 °C, respectively. However, most regions experienced significant decreases in the temperature thresholds (especially Tr), with decreasing RH. Almost all of the regions also experienced significant increases in Tw, especially on the TP and during the winter and spring. The adverse combination of the increase in Tw and the decrease in the temperature thresholds resulted in more precipitation falling as rain, although the snowfall slightly increased in some regions.
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| 4077. |
- Su, Y., et al.
(författare)
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Optical signal processing in SOI waveguide devices
- 2009
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Ingår i: 2009 14th OptoElectronics and Communications Conference, OECC 2009. - 9781424441037 ; , s. -733
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Konferensbidrag (refereegranskat)abstract
- We experimentally demonstrate optical signal processing in silicon ring resonators, including slow-light delay of digital and microwave photonic signals, dense wavelength conversions/multicasting, optical up-convertion, format conversions, temporal differentiation, and bio-sensing.
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| 4078. |
- Su, Y., et al.
(författare)
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Signal processing in silicon waveguides
- 2009
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Ingår i: 2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009. - Washington, D.C. : OSA. - 9781557528773 ; , s. 5377017-
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Konferensbidrag (refereegranskat)abstract
- We experimentally demonstrate optical signal processing in silicon ring resonators, including slow and fast in silicon rings, optical delay of digital and microwave photonic signals, dense wavelength conversions/multicasting, optical up-conversion, format conversions, temporal differentiation, and bio-sensing.
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| 4079. |
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| 4080. |
- Sui, Y., et al.
(författare)
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Mining urban sustainable performance : Spatio-temporal emission potential changes of urban transit buses in post-COVID-19 future
- 2020
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Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 280
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Tidskriftsartikel (refereegranskat)abstract
- Emission benefits of transit buses depend on ridership. Declines in ridership caused by COVID-19 leads uncertainty about the emission reduction capacity of buses. This paper provides a method framework for analyzing spatio-temporal emission patterns of buses in combination with real-time ridership and potential emission changes in the post-COVID-19 future. Based on GPS trajectory and Smart Card data of 2056 buses from 278 routes covering 1.5 million ridership in Qingdao, China, spatio-temporal emissions characteristics of buses are studied. 7589 taxis with 0.2 million passengers’ trips are used for acquiring private cars’ emissions to evaluate the emissions difference between buses and cars. Empirical results show that the average difference between buses and cars with 2 persons can reach up to 117 g/km-person during 7:00–8:59 and 115 g/km-person during 17:00–18:59. However, buses have various emission benefits around the city at different periods. A double increase in emissions during non-rush hours can be observed compared with rush hours. 224 online survey data are used to study the potential ridership reduction trend in post-COVID-19. Results show that 56.3% of respondents would decrease the usage of buses in the post-COVID-19 future. Based on this figure, our analysis shows that per kilometer-person emissions of buses are higher than cars during non-rush hours, however, still lower than cars during rush hours. We conclude that when ridership reduces by more than 40%, buses cannot be “greener” travel modal than cars as before. Finally, several feasible policies are suggested for this potential challenge. Our study provides convincing evidence for understanding the emission patterns of buses, to support better buses investment decisions and promotion on eco-friendly public transport service in the post-COVID-19 future.
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