The relative contribution of long-distance dispersal and local diffusion in the spread of invasive species has been a subject of much debate. Invasion of the intertidal mudflats by Spartina alterniflora is an ideal ex...The relative contribution of long-distance dispersal and local diffusion in the spread of invasive species has been a subject of much debate. Invasion of the intertidal mudflats by Spartina alterniflora is an ideal example of stratified diffusion, involving both long-distance dispersal of seeds and local diffusion due to clonal growth. In conjunction with experimental data on range radius-versus-time curve, a traveling wave equation-based model is used to investigate the sensitivity of the spread rate of exotic S. alterniflora to parameters of long distance dispersal (c, maximum colonial establishment rate) and local colony diffusion (r, intrinsic growth rate) at two tidal marshes, the Eastern Chongming and the Jiuduansha Islands, at the Yangtze River estuary. Both Eastern Chong ming and Jiuduansha Islands are now national natural reserves in China, which were established in 2005. However, the mudflats and salt marshes in the two reserves are now heavily infested with introduced S. alterniflora, which may threaten the estuarine ecosystems and their biodiversity. S. alterniflora was first found in 1995 on Chongming. For rapid sediment accretion in mudflats in the estuary, S. alterniflora was also intentionally introduced to Jiuduansha in 1997 and Chongming in 2001, which has led to a rapid range expansion in the estuary. Our results show that range expansion of species with stratified diffusion is affected by both long-distance dispersal and local colony diffusion, and that there is a critical c*, below which the spread rate is more influenced by long-distance dispersal than by local diffusion. After applying this model to the invasion of S. alterniflora in the Yangtze River estuary, we derive that c = 1.7 × 10-3, c* = 0.126 and c = 4.8 × 10-3 km-2·yr-1, c* = 0.140 km-2·yr-1 at Chongming and Jiuduansha (Shanghai), respectively. Our results suggest that the range spread of S. alterniflora in the Yangtze River estuary is more influenced by long-distance dispersal than local colony diffusion, and that S. alterniflora generates about 1.7 × 10-3 to 4.8 × 10-3 colonies per square kilometers per year. This study provides important information about dispersal dynamics of S. alterniflora that may be useful for finding optimal control strategies. ·展开更多
This paper focuses on the non zero dispersion shifted fiber optical transmission system which employs cascaded in line Phase sensitive Amplifiers ( PSAs ). By computer simulation, we have revealed that the eye p...This paper focuses on the non zero dispersion shifted fiber optical transmission system which employs cascaded in line Phase sensitive Amplifiers ( PSAs ). By computer simulation, we have revealed that the eye penalty of high speed signal pulses increases with the accretion of dispersion and the transmission distance limited by Intersymbol Interference ( ISI ) of signals varies with the spacing and average output power of amplifiers for positive and negative fiber dispersion. The analysis shows that although PSA can compensate for both positive and negative dispersion, it is only valid for small dispersion coefficient fiber. Owing to the effect of Self phase modulation ( SPM ), the ISI limited transmission distance of positive dispersion fiber is much longer than that of negative dispersion fiber. In addition, for positive fiber dispersion, there is an optimum value of average output signal power from PSA leading to the longest ISI limited transmission distance.展开更多
The rock mechanical properties and elastic anisotropy of terrestrial shale oil reservoirs are affected by various factors,such as lithology,structure,pores,fractures,and fluids.The experimental study of dynamic and st...The rock mechanical properties and elastic anisotropy of terrestrial shale oil reservoirs are affected by various factors,such as lithology,structure,pores,fractures,and fluids.The experimental study of dynamic and static elastic properties can provide important mechanism analysis for the prediction of geological and engineering “sweet spots” in shale reservoirs.There are a large number of studies on the measurement of static mechanical properties of shale,but the experiments on dynamic crossband elastic anisotropy of terrestrial shale have not yet been conducted thoroughly.Therefore,we report the anisotropic dispersion mechanism of favorable lithofacies(lamellar dolomitic shale,with vertical and horizontal bedding) in the inter-salt shale oil reservoir of the Qianjiang Formation for different confining pressures and fluid saturation conditions.The experiments were conducted by the cross-band rock physics measurement technology that comprised low-frequency stress-strain measurements and a high-frequency ultrasonic test.The experimental results indicated that:(1) The elastic property dispersion of the terrestrial shale was stronger than that of marine shale due to the high viscosity of the medium oil in the terrestrial shale.The lamellar structures and interbedded fractures were the main factors that determined the strong anisotropy of the terrestrial shale.(2) The dispersion of elastic properties from low to high frequencies in a partial oil saturation state ranged from strong to weak;the wave-induced fluid flow or intrinsic dissipation of viscoelastic inclusions may be the dominant mechanisms that caused the seismic dispersion.(3) The elastic parameters measured in the direction vertical to the bedding plane had stronger dispersion and pressure sensitivity than those measured in the direction parallel to the bedding plane,and the anisotropy and pressure sensitivity at seismic frequencies were higher than those at the ultrasonic frequencies.(4) Fluid filling reduced the pressure sensitivity of the elastic parameters along the direction vertical to the bedding plane,whereas the opposite trend was observed along the direction parallel to the bedding plane.(5) The anisotropic Gassmann theory could explain the P-wave velocity well at an extremely low frequency,but the prediction of S-and P-wave velocities at a relatively high frequency remained insufficient.Overall,our study can serve as a reliable mechanism reference for the study of frequency-dependent properties of azimuthal anisotropy,and provide important guidance for the seismic prediction of “sweet spots” in shale oil reservoirs.展开更多
Background： Current evidence links atrial fibrillation （AF） to the inflammation. Inflammatory indexes such as high-sensitive C-reactive protein （hs-CRP） have been related to the development and persistence of AF....Background： Current evidence links atrial fibrillation （AF） to the inflammation. Inflammatory indexes such as high-sensitive C-reactive protein （hs-CRP） have been related to the development and persistence of AF. However, the role of inflammation in the atrial electrophysiological remodeling indexed by P-wave dispersion （Pa） remains unclear. Methods： The study consisted of 71 patients with lone paroxysmal AF （AF group） and 71 age- and gender-matched controls of paroxysmal supraventricular tachycardia without history of AF （control group）. Electrocardiography, P hs-CRP, and other clinical characteristics were compared between the two groups. Results： There was no significant difference between the two groups regarding age, gender, hyperlipidemia, etc. Compared to controls, left atrial diameter （44 ± 7 vs 39 ± 7 mm）, Pd （49 ± 13 vs 26 ± 8 ms）, and hs-CRP （2.17 [1.46-2.89] vs 1.12 [0.74-1.41] rag/L） were increased （P 〈 0.05）, respectively. Linear regression identified hs-CRP as an independent correlation ofPd level both in the total population and the AF group （r = 0.464 and 0.313; P 〈 0.001, respectively）. Multiple logistic regression revealed hs-C RP as an independent determinant of AF （odds ratio [OR] =l 5.430, 95% confidence interval： 6.031-39.476： P 〈0.001）. Further adjusted tbr Pd, both Pd and hs-CRP were independent predictors for AF, but the OR for hs-CRP in predicting AF has been attenuated from 15.430 to 6.246. Conclusions： In lone AF, P and plasma hs-CRP concentration are inter-associated and related to AF. The interaction between hs-CRP and AF may be mediated by Pe, suggesting an important role of inflammation in the atrial electrophysiological remodeling predisposing to AF.展开更多
Generally, nanoparticles are easy to aggregate due to their nano sizes, which influence the physical and chemical properties. In this work, a dispersion treatment of the TiO2 nanoparticles with different average sizes...Generally, nanoparticles are easy to aggregate due to their nano sizes, which influence the physical and chemical properties. In this work, a dispersion treatment of the TiO2 nanoparticles with different average sizes was employed to improve the dispersion of TiO2 nanoparticles, in order to prepare flexible photoanodes for dye-sensitized solar cells (DSCs) with novel photovoltaic properties at a low temperature. The effects of dispersion treatment on the dispersion of TiO2 nanoparticles, including the viscosities of the binder-free TiO2 paste, the morphologies and textural properties of nanoparticle-TiO2 films, and the photovoltaic properties of the flexible DSCs, were investigated. Flexible indium-tin oxide (ITO)-coated polyethylene naphthalate (PEN) substrates with sputter deposited Pt were employed as the transparent flexible counter electrodes. A short-circuit photocurrent density of 9.62 mA·cm 2, an open-circuit voltage of 0.757 V, a fill factor of 0.589 and an overall light-to-energy conversion efficiency of 4.29% for the flexible DSCs under AM1.5 illumination of 100 mW cm 2 were obtained with dispersion treatment. A 30.8% increment of the energy conversion efficiency for DSCs made by dispersion treatment was obtained compared with that made without dispersion treatment.展开更多
文摘The relative contribution of long-distance dispersal and local diffusion in the spread of invasive species has been a subject of much debate. Invasion of the intertidal mudflats by Spartina alterniflora is an ideal example of stratified diffusion, involving both long-distance dispersal of seeds and local diffusion due to clonal growth. In conjunction with experimental data on range radius-versus-time curve, a traveling wave equation-based model is used to investigate the sensitivity of the spread rate of exotic S. alterniflora to parameters of long distance dispersal (c, maximum colonial establishment rate) and local colony diffusion (r, intrinsic growth rate) at two tidal marshes, the Eastern Chongming and the Jiuduansha Islands, at the Yangtze River estuary. Both Eastern Chong ming and Jiuduansha Islands are now national natural reserves in China, which were established in 2005. However, the mudflats and salt marshes in the two reserves are now heavily infested with introduced S. alterniflora, which may threaten the estuarine ecosystems and their biodiversity. S. alterniflora was first found in 1995 on Chongming. For rapid sediment accretion in mudflats in the estuary, S. alterniflora was also intentionally introduced to Jiuduansha in 1997 and Chongming in 2001, which has led to a rapid range expansion in the estuary. Our results show that range expansion of species with stratified diffusion is affected by both long-distance dispersal and local colony diffusion, and that there is a critical c*, below which the spread rate is more influenced by long-distance dispersal than by local diffusion. After applying this model to the invasion of S. alterniflora in the Yangtze River estuary, we derive that c = 1.7 × 10-3, c* = 0.126 and c = 4.8 × 10-3 km-2·yr-1, c* = 0.140 km-2·yr-1 at Chongming and Jiuduansha (Shanghai), respectively. Our results suggest that the range spread of S. alterniflora in the Yangtze River estuary is more influenced by long-distance dispersal than local colony diffusion, and that S. alterniflora generates about 1.7 × 10-3 to 4.8 × 10-3 colonies per square kilometers per year. This study provides important information about dispersal dynamics of S. alterniflora that may be useful for finding optimal control strategies. ·
文摘This paper focuses on the non zero dispersion shifted fiber optical transmission system which employs cascaded in line Phase sensitive Amplifiers ( PSAs ). By computer simulation, we have revealed that the eye penalty of high speed signal pulses increases with the accretion of dispersion and the transmission distance limited by Intersymbol Interference ( ISI ) of signals varies with the spacing and average output power of amplifiers for positive and negative fiber dispersion. The analysis shows that although PSA can compensate for both positive and negative dispersion, it is only valid for small dispersion coefficient fiber. Owing to the effect of Self phase modulation ( SPM ), the ISI limited transmission distance of positive dispersion fiber is much longer than that of negative dispersion fiber. In addition, for positive fiber dispersion, there is an optimum value of average output signal power from PSA leading to the longest ISI limited transmission distance.
基金supported by the National Natural Science Foundation of China (Grant Nos.U20B2015,41574103,41974120,41804104,and U19B600304)。
文摘The rock mechanical properties and elastic anisotropy of terrestrial shale oil reservoirs are affected by various factors,such as lithology,structure,pores,fractures,and fluids.The experimental study of dynamic and static elastic properties can provide important mechanism analysis for the prediction of geological and engineering “sweet spots” in shale reservoirs.There are a large number of studies on the measurement of static mechanical properties of shale,but the experiments on dynamic crossband elastic anisotropy of terrestrial shale have not yet been conducted thoroughly.Therefore,we report the anisotropic dispersion mechanism of favorable lithofacies(lamellar dolomitic shale,with vertical and horizontal bedding) in the inter-salt shale oil reservoir of the Qianjiang Formation for different confining pressures and fluid saturation conditions.The experiments were conducted by the cross-band rock physics measurement technology that comprised low-frequency stress-strain measurements and a high-frequency ultrasonic test.The experimental results indicated that:(1) The elastic property dispersion of the terrestrial shale was stronger than that of marine shale due to the high viscosity of the medium oil in the terrestrial shale.The lamellar structures and interbedded fractures were the main factors that determined the strong anisotropy of the terrestrial shale.(2) The dispersion of elastic properties from low to high frequencies in a partial oil saturation state ranged from strong to weak;the wave-induced fluid flow or intrinsic dissipation of viscoelastic inclusions may be the dominant mechanisms that caused the seismic dispersion.(3) The elastic parameters measured in the direction vertical to the bedding plane had stronger dispersion and pressure sensitivity than those measured in the direction parallel to the bedding plane,and the anisotropy and pressure sensitivity at seismic frequencies were higher than those at the ultrasonic frequencies.(4) Fluid filling reduced the pressure sensitivity of the elastic parameters along the direction vertical to the bedding plane,whereas the opposite trend was observed along the direction parallel to the bedding plane.(5) The anisotropic Gassmann theory could explain the P-wave velocity well at an extremely low frequency,but the prediction of S-and P-wave velocities at a relatively high frequency remained insufficient.Overall,our study can serve as a reliable mechanism reference for the study of frequency-dependent properties of azimuthal anisotropy,and provide important guidance for the seismic prediction of “sweet spots” in shale oil reservoirs.
文摘Background： Current evidence links atrial fibrillation （AF） to the inflammation. Inflammatory indexes such as high-sensitive C-reactive protein （hs-CRP） have been related to the development and persistence of AF. However, the role of inflammation in the atrial electrophysiological remodeling indexed by P-wave dispersion （Pa） remains unclear. Methods： The study consisted of 71 patients with lone paroxysmal AF （AF group） and 71 age- and gender-matched controls of paroxysmal supraventricular tachycardia without history of AF （control group）. Electrocardiography, P hs-CRP, and other clinical characteristics were compared between the two groups. Results： There was no significant difference between the two groups regarding age, gender, hyperlipidemia, etc. Compared to controls, left atrial diameter （44 ± 7 vs 39 ± 7 mm）, Pd （49 ± 13 vs 26 ± 8 ms）, and hs-CRP （2.17 [1.46-2.89] vs 1.12 [0.74-1.41] rag/L） were increased （P 〈 0.05）, respectively. Linear regression identified hs-CRP as an independent correlation ofPd level both in the total population and the AF group （r = 0.464 and 0.313; P 〈 0.001, respectively）. Multiple logistic regression revealed hs-C RP as an independent determinant of AF （odds ratio [OR] =l 5.430, 95% confidence interval： 6.031-39.476： P 〈0.001）. Further adjusted tbr Pd, both Pd and hs-CRP were independent predictors for AF, but the OR for hs-CRP in predicting AF has been attenuated from 15.430 to 6.246. Conclusions： In lone AF, P and plasma hs-CRP concentration are inter-associated and related to AF. The interaction between hs-CRP and AF may be mediated by Pe, suggesting an important role of inflammation in the atrial electrophysiological remodeling predisposing to AF.
基金supported by the National High Technology Research and Development Program of China (Grant No. 2011AA-050522)Sanjiang-yuan Scientific Program of Qinghai Science & Technology Department(Grant No. 2010-N-S03)the Ministry of Science & Technology (MOST) International S&T Cooperation Program of China (Grant No. 2010DFA-64360)
文摘Generally, nanoparticles are easy to aggregate due to their nano sizes, which influence the physical and chemical properties. In this work, a dispersion treatment of the TiO2 nanoparticles with different average sizes was employed to improve the dispersion of TiO2 nanoparticles, in order to prepare flexible photoanodes for dye-sensitized solar cells (DSCs) with novel photovoltaic properties at a low temperature. The effects of dispersion treatment on the dispersion of TiO2 nanoparticles, including the viscosities of the binder-free TiO2 paste, the morphologies and textural properties of nanoparticle-TiO2 films, and the photovoltaic properties of the flexible DSCs, were investigated. Flexible indium-tin oxide (ITO)-coated polyethylene naphthalate (PEN) substrates with sputter deposited Pt were employed as the transparent flexible counter electrodes. A short-circuit photocurrent density of 9.62 mA·cm 2, an open-circuit voltage of 0.757 V, a fill factor of 0.589 and an overall light-to-energy conversion efficiency of 4.29% for the flexible DSCs under AM1.5 illumination of 100 mW cm 2 were obtained with dispersion treatment. A 30.8% increment of the energy conversion efficiency for DSCs made by dispersion treatment was obtained compared with that made without dispersion treatment.
