23,900 research outputs found
Increase in soil organic carbon by agricultural intensification in northern China
Acknowledgements. This research was supported by National Natural Science Foundation of China (no. 31370527 and 31261140367) and the National Science and Technology Support Program of China (no. 2012BAD14B01-2). The authors gratefully thank the Huantai Agricultural Station for providing of the Soil Fertility Survey data. We also thank Zheng Liang from China Agricultural University for the soil sampling and analysis in 2011. Thanks are extended to Jessica Bellarby for helpful discussion and suggestions.Peer reviewedPublisher PD
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Provision of secondary frequency regulation by coordinated dispatch of industrial loads and thermal power plants
Demand responsive industrial loads with high thermal inertia have potential to provide ancillary service for frequency regulation in the power market. To capture the benefit, this study proposes a new hierarchical framework to coordinate the demand responsive industrial loads with thermal power plants in an industrial park for secondary frequency control. In the proposed framework, demand responsive loads and generating resources are coordinated for optimal dispatch in two-time scales: (1) the regulation reserve of the industrial park is optimally scheduled in a day-ahead manner. The stochastic regulation signal is replaced by the specific extremely trajectories. Furthermore, the extremely trajectories are achieved by the day-ahead predicted regulation mileage. The resulting benefit is to transform the stochastic reserve scheduling problem into a deterministic optimization; (2) a model predictive control strategy is proposed to dispatch the industry park in real time with an objective to maximize the revenue. The proposed technology is tested using a real-world industrial electrolysis power system based upon Pennsylvania, Jersey, and Maryland (PJM) power market. Various scenarios are simulated to study the performance of the proposed approach to enable industry parks to provide ancillary service into the power market. The simulation results indicate that an industrial park with a capacity of 500 MW can provide up to 40 MW ancillary service for participation in the secondary frequency regulation. The proposed strategy is demonstrated to be capable of maintaining the economic and secure operation of the industrial park while satisfying performance requirements from the real world regulation market
Homologous Muscle Contraction during Unilateral Movement Does Not Show a Dominant Effect on Leg Representation of the Ipsilateral Primary Motor Cortex
Co-activation of homo- and heterotopic representations in the primary motor cortex (M1) ipsilateral to a unilateral motor task has been observed in neuroimaging studies. Further analysis showed that the ipsilateral M1 is involved in motor execution along with the contralateral M1 in humans. Additionally, transcranial magnetic stimulation (TMS) studies have revealed that the size of the co-activation in the ipsilateral M1 has a muscle-dominant effect in the upper limbs, with a prominent decline of inhibition within the ipsilateral M1 occurring when a homologous muscle contracts. However, the homologous muscle-dominant effect in the ipsilateral M1 is less clear in the lower limbs. The present study investigates the response of corticospinal output and intracortical inhibition in the leg representation of the ipsilateral M1 during a unilateral motor task, with homo- or heterogeneous muscles. We assessed functional changes within the ipsilateral M1 and in corticospinal outputs associated with different contracting muscles in 15 right-handed healthy subjects. Motor tasks were performed with the right-side limb, including movements of the upper and lower limbs. TMS paradigms were measured, consisting of short-interval intracortical inhibition (SICI) and recruitment curves (RCs) of motor evoked potentials (MEPs) in the right M1, and responses were recorded from the left rectus femoris (RF) and left tibialis anterior (TA) muscles. TMS results showed that significant declines in SICI and prominent increases in MEPs of the left TA and left RF during unilateral movements. Cortical activations were associated with the muscles contracting during the movements. The present data demonstrate that activation of the ipsilateral M1 on leg representation could be increased during unilateral movement. However, no homologous muscle-dominant effect was evident in the leg muscles. The results may reflect that functional coupling of bilateral leg muscles is a reciprocal movement
Deformation of a Trapped Fermi Gas with Unequal Spin Populations
The real-space densities of a polarized strongly-interacting two-component
Fermi gas of Li atoms reveal two low temperature regimes, both with a
fully-paired core. At the lowest temperatures, the unpolarized core deforms
with increasing polarization. Sharp boundaries between the core and the excess
unpaired atoms are consistent with a phase separation driven by a first-order
phase transition. In contrast, at higher temperatures the core does not deform
but remains unpolarized up to a critical polarization. The boundaries are not
sharp in this case, indicating a partially-polarized shell between the core and
the unpaired atoms. The temperature dependence is consistent with a tricritical
point in the phase diagram.Comment: Accepted for publication in Physical Review Letter
Evolution of sperm morphology in anurans : Insights into the roles of mating system and spawning location
Background: The degree of postcopulatory sexual selection, comprising variable degrees of sperm competition and cryptic female choice, is an important evolutionary
force to influence sperm form and function. Here we investigated the effects of
mating system and spawning location on the evolution of sperm morphology in 67
species of Chinese anurans. We also examined how relative testes mass as an
indicator of the level of sperm competition affected variation in sperm morphology
across a subset of 29 species.
Results: We found a significant association of mating system and spawning location
with sperm morphology. However, when removing the effects of body mass or
absolute testes mass for species for which such data were available, this effect became
non-significant. Consistent with predictions from sperm competition theory, we found
a positive correlation between sperm morphology and relative testes mass after taking
phylogeny into account.
Conclusions: Our findings suggest that sexual selection in Chinese anurans favors
longer sperm when the level of sperm competition is high. Pre-copulatory male-male
competition and spawning location, on the other hand, do not affect the evolution of
sperm morphology after taking body mass and absolute testes mass into account
On peaked solitary waves of Degasperis - Procesi equation
The Degasperis - Procesi (DP) equation describing the propagation of shallow
water waves contains a physical parameter , and it is well-known that
the DP equation admits solitary waves with a peaked crest when . In
this article, we illustrate, for the first time, that the DP equation admits
peaked solitary waves even when . This is helpful to enrich our
knowledge and deepen our understandings about peaked solitary waves of the DP
equation.Comment: 11 pages, 3 figures, accepted by Science China - Physics, Mechanics &
Astronom
Geographic variation in life-history traits : growth season affects age structure, egg size and clutch size in Andrew’s toad (Bufo andrewsi)
Background: Environmental variation associated with season length is likely to promote differentiation in lifehistory
traits, but has been little studied in natural populations of ectotherms. We investigated patterns of variation
in egg size, clutch size, age at sexual maturity, maximum age, mean age, growth rate and adult body size in
relation to growth season length among 17 populations of Andrew’s toad (Bufo andrewsi) at different latitudes and
altitudes in the Hengduan Mountains, western China.
Results: We found that egg size, age at sexual maturity, and mean age increased with decreasing length of the
growth season, whereas clutch size showed a converse cline. Body size did not increase with decreasing length of
the growth season, but was tightly linked to lifetime activity (i.e. the estimated number of active days during
lifetime). Males and females differed in their patterns of geographic variation in growth rates, which may be the
result of forces shaping the trade-off between growth and reproduction in different environments.
Conclusions: Our findings suggest that growth season plays an important role in shaping variation in life-history
traits in B. andrewsi across geographical gradients
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