Modeling transport of soft particles in porous media.

Flow-driven transport of soft particles in porous media is ubiquitous in many natural and engineering processes, such as the gel treatment for enhanced oil recovery. In many of these processes, injected deformable particles block the pores and thus increase the overall pressure drop and reduce the permeability of the particle-resided region. The change of macroscopic properties (e.g., pressure drop and permeability) is an important indicator of the system performance, yet sometimes impossible to be measured. Therefore, it is desirable to correlate these macroscopic properties with the measurable or controllable properties. In this work, we study flow-driven transport of soft particles in porous media using a generalized capillary bundle model. By modeling a homogeneous porous medium as parallel capillaries along the flow direction with periodically distributed constrictions, we first build a governing differential equation for pressure. Solving this equation gives a quantitative correlation between the total pressure drop and measurable parameters, including concentration and stiffness of particles, size ratio of particle to pore throat, and flow rate. The resultant permeability reduction is also obtained. Our results show that the total pressure drop and permeability reduction are both exponentially dependent on the particle concentration and the size ratio of particles to pore throat. With no more than two fitting parameters, our model shows excellent agreements with several reported experiments. The work not only sheds light on understanding transport of soft particles in porous media but also provides important guidance for choosing the optimal parameters in the relevant industrial processes.

Aberrant brain functional connectome in patients with obstructive sleep apnea.

OBJECTIVE: Obstructive sleep apnea (OSA) is accompanied by widespread abnormal spontaneous regional activity related to cognitive deficits. However, little is known about the topological properties of the functional brain connectome of patients with OSA. This study aimed to use the graph theory approaches to investigate the topological properties and functional connectivity (FC) of the functional connectome in patients with OSA, based on resting-state functional magnetic resonance imaging (rs-fMRI). METHODS: Forty-five male patients with newly diagnosed untreated severe OSA and 45 male good sleepers (GSs) underwent a polysomnography (PSG), clinical evaluations, and rs-fMRI scans. The automated anatomical labeling (AAL) atlas was used to construct the functional brain connectome. The topological organization and FC of brain functional networks in patients with OSA were characterized using graph theory methods and investigated the relationship between functional network topology and clinical variables. RESULTS: Both the patients with OSA and the GSs exhibited high-efficiency "small-world" network attributes. However, the patients with OSA exhibited decreased σ, γ, Eglob; increased Lp, λ; and abnormal nodal centralities in several default-mode network (DMN), salience network (SN), and central executive network (CEN) regions. However, the patients with OSA exhibited abnormal functional connections between the DMN, SN, and CEN. The disrupted FC was significantly positive correlations with the global network metrics γ and σ. The global network metrics were significantly correlated with the Epworth Sleepiness Scale (ESS) score, Montreal Cognitive Assessment (MoCA) score, and oxygen desaturation index. CONCLUSION: The findings suggest that the functional connectome of patients with OSA exhibited disrupted functional integration and segregation, and functional disconnections of the DMN, SN, and CEN. The aberrant topological attributes may be associated with disrupted FC and cognitive functions. These topological abnormalities and disconnections might be potential biomarkers of cognitive impairments in patients with OSA.

Insight into the local source of polybrominated diphenyl ethers in the developing Tibetan Plateau: The composition and transport around the Lhasa landfill.

In the background region of the Tibetan Plateau (TP), the rapid urbanization probably results in the massive generation of persistent organic pollutants (POPs), which lacks monitoring and evaluation. Since landfill could serve as an important sink of the locally used POPs, the analysis of POPs in the Tibetan landfill area might help us to understand the source composition and their transport in the TP. In this study, the concentration variations of polybrominated diphenyl ethers (PBDEs) in five soil profiles and seven surficial sediments around the largest Tibetan landfill were investigated. The total concentrations of PBDEs ranged from 128 to 1219 ng/kg in soils, and from 447 to 7295 ng/kg in sediments. The dominance of nona- and deca-BDEs possibly indicated the wide usage of deca-BDE as flame retardant in the TP. The vertical and spatial distribution patterns of PBDEs within soils plausibly revealed their main transport pathways by atmospheric dispersion and leachate seepage from landfill. Based on principal components analysis and multiple linear regression, these two pathways were estimated to account for 61% and 39% of the total concentrations, respectively. Additionally, the spatial and vertical distributions of octa-to deca-BDEs within soils were significantly influenced by soil particle size. Although the PBDEs inventory in the study area was comparatively low, the rapid urbanization in the TP might dramatically accelerate the PBDE emissions in the future. This study firstly introduced the presence of local PBDEs in the TP, and the inventory already influenced the surrounding environment. Once involved in the regional cycle of the TP, the local source of PBDEs from waste might significantly serve to raise background level resulting otherwise primarily from long-range atmospheric transport.

Organochlorine pesticides in the sedimentary core of the southern Tibetan Plateau: The missing pieces induced by lateral remobilization.

The sedimentary core in remote alpine lakes has been recognized as an ideal proxy to reconstruct the emission and air deposition histories of persistent organic pollutants (POPs). Nevertheless, POPs formerly stored in a catchment might also contribute to the variation in the lake sediment by lateral remobilization. In this study, to reveal the relative importance of lateral remobilization, we measured the vertical profiles and isomeric ratios of dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs) and endosulfan in a dated sedimentary core collected from Lake Yamzho Yumco in the southern Tibetan Plateau. In addition to the flux peaks in the 1970s corresponding to the heavy atmospheric deposition of DDTs and HCHs, these pollutants' fluxes displayed rebounds in the flood periods, with characteristic low ratios of DDT/DDE (α-/ß-HCH). This might indicate a massive remobilization of "weathered" pesticides from catchment soil to the lake because of strong hydro-dynamics. Moreover, the relative contribution of lateral remobilization to the lake sediment in the past decades was recognized through the correlation between DDT/DDE (α-/ß-HCH) ratios and ∑DDT (∑HCH) fluxes. The results showed that the lateral remobilization contributed to 20-42% of the total fluxes. This study discriminated the air deposition from the contribution of lateral remobilization, which improves current understanding of the vertical POPs profiles in the sedimentary core.

The emerging source of polycyclic aromatic hydrocarbons from mining in the Tibetan Plateau: Distributions and contributions in background soils.

The Tibetan Plateau (TP) serves as the background for persistent organic pollutants around the world. In addition to outside sources, local sources greatly contribute to the environment of the TP in recent decades. Mining activity could serve as an emerging source of polycyclic aromatic hydrocarbons (PAHs), although this issue has been neglected in the TP until now. To investigate the distributions and contributions of PAHs transported from mining activity, forty-one surface soil samples along six sampling directions were collected at a regular distance from the Jiama mining area (JMA) of the TP at altitudes between 3726 and 4863m. The total concentration of 16 PAHs was 52.34±22.58ng/g. The result of the source identification suggested that mining activity represented the primary source for heavy molecular weight (HMW) PAHs in soils, while light molecular weight (LMW) and middle molecular weight (MMW) PAHs were contributed by multiple sources. For HMW PAHs, the concentrations and proportions decreased logarithmically with transport distance from the JMA. Furthermore, the transport distance of HMW PAHs was found to be affected by the prevailing wind direction. In addition to transport from the source area, the distributions of LMW and MMW PAHs were also influenced by the altitude. In the impact area of Jiama mining activity, the soil mass inventory was estimated to be 6.4±0.8tons for HMW PAHs. In future decades, HMW PAHs emitted from Jiama mining activity are projected to exceed 5% of the annual local emission in the TP. Our study evidenced that Tibetan mining activity serves as an important emerging source of PAHs, which would be transported within the TP and threaten the fragile ecosystem of the TP.

Regulation of spinal neuroimmune responses by prolonged morphine treatment in a rat model of cancer induced bone pain.

Cancer induced bone pain (CIBP) is a major clinical problem. Although opioids remain the principal axis in drug therapies for CIBP, their sustained application is known to induce cellular and molecular adaptations including enhanced neuroimmune reactivity. This is generally characterized by glial activation and proinflammatory cytokine production which frequently results in pharmacological tolerance. This research was performed to investigate spinal neuroimmune responses after prolonged systemic morphine treatment in a rat model of CIBP. The model was established using a unilateral intra-tibia injection of Walker 256 mammary gland carcinoma cells. Subcutaneous morphine was repeatedly administered from postoperative days 14 to 19. Mechanical allodynia to von Frey filaments and ambulatory pain scores were recorded to investigate changes of nociceptive behaviors. Spinal glial activation was detected by immunohistochemistry and real-time PCR; the production of proinflammatory cytokines (IL-1beta and TNF-alpha) was examined through real-time PCR and ELISA. Results showed that chronic morphine use failed to elicit analgesic tolerance in the rat CIBP model. Moreover, the treatment had no significant influence on the activated spinal glia morphology, cell density and expression of special cytomembrane markers, whereas it significantly down-regulated the local proinflammatory cytokine production at the mRNA and protein level. Collectively, these data suggest that chronic morphine treatment in CIBP is not concomitant with pharmacological tolerance, at least partially because the treatment fails to amplify spinal neuroimmune responses.