Impact of agricultural irrigation and resettlement practices on carbon storage in arid inland river basins: A case study of the Shule river basin.

Agricultural irrigation and resettlement have significant impacts on carbon storage in arid inland river basins. With the background of "Comprehensive development measures for agricultural irrigation and resettlement in Shule River Basin (SRB)", this paper uses land use data to estimate regional carbon storage through InVEST model and revises the result by using net ecosystem productivity (NEP). The influence of land use change on carbon storage and the driving factors of carbon storage spatial differentiation were analyzed by using the optimal parameters geographical detector (OPGD). It can be inferred from the results that: (1) During 2000-2020, the increase of cropland and grassland area is the main type of land use change in the central oasis area of Yumen City and Guazhou County. Cumulative carbon storage increased by 1.75 × 107 t. (2) NEP in the central oasis area of Yumen City and Guazhou County showed a fluctuating upward trend, and it generally behaves as a carbon sink. The average annual NEP was 1.78 × 105 t, and the carbon sink increased by 0.95 × 105 t. (3) The main factors responsible for driving are vegetation, elevation, potential evapotranspiration, and precipitation. The explanatory power of each factor in carbon storage spatial differentiation was enhanced by the interaction between natural and anthropogenic factors. The interaction between vegetation and the human factor is more significant than that of the human single factor. (4) Agricultural irrigation and resettlement measures did not cause a decline in ecosystem carbon storage in Yumen City and Guazhou County in the central part of SRB. Conversely, the region's ecosystems have seen an increase in carbon storage as a result of the increase in cropland. (5) The introduction of the NEP modification method and the OPGD model improves the accuracy of carbon storage estimation and obtains better driving results in spatial differentiation. The study idea provides a new perspective for the estimation of carbon storage as a whole, and provides a reference basis for the formulation of ecological protection policies.

Application of density clustering with noise combined with particle swarm optimization in UWB indoor positioning.

Due to the presence of non-line-of-sight (NLOS) obstacles, the localization accuracy in ultra-wideband (UWB) wireless indoor localization systems is typically substantially lower. To minimize the influence of these environmental factors and improve the accuracy of indoor wireless positioning, this paper proposes a density clustering with noise combined with particle swarm optimization (DCNPSO) to improve UWB positioning. Which exploits the advantages of the density-based spatial clustering algorithm with noise (DBSCAN) and particle swarm optimization (PSO) algorithm. The experimental results show that the DCNPSO algorithm achieves 45.25% and 36.14% higher average positioning accuracy than the DBSCAN and PSO algorithms, respectively. The positioning error of this algorithm remains stable within 3 cm in static positioning and can achieve high accuracy in NLOS environments.

Urban Vitality Measurement and Influence Mechanism Detection in China.

Urban vitality is the life force of a city. In this paper, starting from three subsystems of population, economy, and function, the comprehensive index system for measuring urban vitality was constructed respectively from three scales: grid, prefecture-level administrative region, and urban agglomeration. GIS spatial analysis methods were used to measure the urban vitality index and analyze the spatial distribution pattern. Then, the MGWR was used to reveal the main factors affecting the difference in urban vitality and analyze the influence mechanism of urban vitality. Accordingly, countermeasures and suggestions for creating vibrancy were put forward. The result shows the following: At the grid scale, urban vitality presents a spatial distribution pattern of "large dispersion, small agglomeration", which has significant differentiation characteristics of city scale and hierarchy. At the administrative region scale, the overall vitality of cities at the prefecture level and above in China is not high, and the spatial differences are large. The spatial scan identified 28 vigorous cities with high potential, belonging to 6 vigorous clusters. On the scale of urban agglomeration, according to the degree of vitality, there are three gradients. The spatial difference in urban vitality was affected by the internal characteristics and external environment.

Spatial remodelling of calcium release units may impair cardiac electro-mechanical function: A simulation study.

Excitation-contraction coupling (E-C coupling) is thought to be based on elementary calcium release units (CRUs) in which clusters of ryanodine receptors (RyRs) localized on the sarcoplasmic reticulum (SR) are in close apposition to L-type Ca2+ channels (LCCs) on the transverse tubules (TTs). However, a fraction of LCC-RyR structure may be uncoupled due to the remodelling of TTs, which would tend to destroy the E-C coupling in the failing heart. Here we proposed a multiscale model of the ventricular myocyte to investigate the relationship between LCC-RyR structure and cardiac electro-mechanical function. The mathematical model consisted of a two-dimensional (2D) subcellular Ca2+ reaction-diffusion sub-model, a cellular electrophysiological sub-model and a cardiomyocyte contraction sub-model. The simulation results showed that the remodelling of CRU microstructure would disturb Ca2+ homeostasis, leading to a dyssynchronous Ca2+ transient, and postpone the generation of isometric force. Our study suggests that structural remodelling is an important mechanism for dysfunction of Ca2+ handling, cellular electrophysiology and contractility in failing heart.

Transmission matrix-based Electric field Monte Carlo study and experimental validation of the propagation characteristics of Bessel beams in turbid media.

A novel Transmission matrix-based Electric field Monte Carlo (TEMC) method is introduced to study the propagation characteristics of Bessel beams with different orbital angular momentum (OAM) in turbid media. As an extension to the Electric field Monte Carlo (EMC) approach, electric field transmission modes were simulated to properly evaluate light interference. Beam transmission patterns, intensity attenuation, and the degree of polarization (DOP) through turbid media of varying thickness were analyzed. It was found that the OAM plays a subtle role in transmission through turbid media, showing only a weak correlation with total transmission, the preservation of DOP, and the penetration depth. The TEMC simulation results were in excellent agreement with experiments, validating the proposed method for the study of coherence phenomenon in turbid media.

Propagation characteristics of partially coherent circular Airy beams.

The abruptly autofocusing properties of partially coherent circular Airy beam (CAB) with different spatial coherent length are theoretically investigated in this paper. It is found that, as spatial coherent length decreases, the size of the focal spot would increase and the focal intensity would decrease. But the abruptly autofocusing property for partially coherent CAB is still quite obvious, when comparing with the common partially coherent Gaussian beam under the same conditions; and its autofocusing position is less easily influenced by coherence. The influences of initial radius r0 and decaying parameter a on the autofocusing property have also been investigated in the end.

Abruptly autofocusing property of circular Airy vortex beams with different initial launch angles.

Controlling the trajectory of circular Airy beams (CABs) by negative launch angles would greatly reduce their abruptly autofocusing property. By numerically simulating the propagation of a circular Airy vortex beam with different initial launch angles, we demonstrate in this paper that a larger topological charge of optical vortex (OV) is quite helpful to enhance the abruptly autofocusing property under different launch angles (especially for negative launch angles), without affecting the focal position and trajectory. Two opposite OVs would attract each other and partially overlap in the focal plane of CAB under different launch angles, causing even stronger autofocusing. As the distance between two OVs increases, the focal intensity contrast would decrease, especially for a beam with positive launch angles, whose autofocusing property decreases much more quickly with the distance.

Propagation characteristics of the modified circular Airy beam.

We have proposed a kind of modified circular Airy beam (MCAB) based upon a modification of the Fourier spectrum of circular Airy beams (CAB) in this paper. Unlike most abruptly autofocusing beams, the position of peak intensity of MCAB can be moved to any rings behind. Two apodization parameters are introduced to describe the propagation characteristics of MCAB. It is found that the focal position, focal trajectory and the size of focal spot do not change with the apodization parameters; but the abruptly autofocusing property will be greatly enhanced if appropriately apodization parameters are chosen. Comparing with the common CAB and the previous blocked CAB, the MCAB shows better abruptly autofocusing property. It may have more applications in various fields.

Simulation of arrhythmogenic effect of rogue RyRs in failing heart by using a coupled model.

Cardiac cells with heart failure are usually characterized by impairment of Ca(2+) handling with smaller SR Ca(2+) store and high risk of triggered activities. In this study, we developed a coupled model by integrating the spatiotemporal Ca(2+) reaction-diffusion system into the cellular electrophysiological model. With the coupled model, the subcellular Ca(2+) dynamics and global cellular electrophysiology could be simultaneously traced. The proposed coupled model was then applied to study the effects of rogue RyRs on Ca(2+) cycling and membrane potential in failing heart. The simulation results suggested that, in the presence of rogue RyRs, Ca(2+) dynamics is unstable and Ca(2+) waves are prone to be initiated spontaneously. These release events would elevate the membrane potential substantially which might induce delayed afterdepolarizations or triggered action potentials. Moreover, the variation of membrane potential depolarization is indicated to be dependent on the distribution density of rogue RyR channels. This study provides a new possible arrhythmogenic mechanism for heart failure from subcellular to cellular level.

Cancer stem cell, niche and EGFR decide tumor development and treatment response: A bio-computational simulation study.

Recent research in cancer biology has suggested the hypothesis that tumors are initiated and driven by a small group of cancer stem cells (CSCs). Furthermore, cancer stem cell niches have been found to be essential in determining fates of CSCs, and several signaling pathways have been proven to play a crucial role in cellular behavior, which could be two important factors in cancer development. To better understand the progression, heterogeneity and treatment response of breast cancer, especially in the context of CSCs, we propose a mathematical model based on the cell compartment method. In this model, three compartments of cellular subpopulations are constructed: CSCs, progenitor cells (PCs), and terminal differentiated cells (TCs). Moreover, (1) the cancer stem cell niche is, considered by modeling its effect on division patterns (symmetric or asymmetric) of CSCs, and (2) the EGFR signaling pathway is integrated by modeling its role in cell proliferation, apoptosis. Our simulation results indicate that (1) a higher probability for symmetric division of CSC may result in a faster expansion of tumor population, and for a larger number of niches, the tumor grows at a slower rate, but the final tumor volume is larger; (2) higher EGFR expression correlates to tumors with larger volumes while a saturation function is observed, and (3) treatments that inhibit tyrosine kinase activity of EGFR may not only repress the tumor volume, but also decrease the CSCs percentages by shifting CSCs from symmetric divisions to asymmetric divisions. These findings suggest that therapies should be designed to effectively control or eliminate the symmetric division of CSCs and to reduce or destroy the CSC niches.

Mathematical models of canine right and left atria cardiomyocytes.

The aim of this study is to build two mathematical models of canine ionic currents specific to right atria and left atria. The canine left atria mathematical model was firstly modified from the Ramirez-Nattel-Courtemanche (RNC) model using the recently available experimental data of ionic currents and was further developed based on our own experimental data. A model of right atria was then built by considering the differences between right atria and left atria. The two developed models well reproduced the experimental data on action potential morphology, the rate dependence, and action potential duration restitution. They are useful for investigating the mechanisms underlying the heterogeneity of canine regional action potentials and would help the simulation of whole heart excitation propagation and cardiac arrhythmia in the near future.