Despite the fact that mixing uniformity (i.e. the consistency of binder distribution) significantly influence the quality of ground improvement during in situ soil mixing projects, its quantitative evaluation was rarely concerned due to the difficulty of measurement from an engineering perspective. A methodology was proposed to quantitatively evaluate the mixing uniformity of stabilized soil using handheld X-fluorescence spectrometry (XRF), which is helpful to elucidate the significance of mixing uniformity on strength. In other words, the calcium content was monitored to ascertain the distribution of cement within the matrix, and a quantitative index was subsequently established. It was observed that an increase in mixing uniformity resulted in a transition in the behavior of the stabilized clay from a plastic to a brittle failure mode, and from a localized failure to a global shear failure under unconfined compression. Subsequent observation of the destruction process revealed that cracks were more readily formed in the low cement zones and then bypass the high cement zones. Furthermore, the effect of mixing uniformity on strength is likely to be amplified with prolonged curing periods. The enhancement of uniformity would increase the volume of the high binder zones, thereby enhancing the overall high-strength performance. The proposed methodology is capable of characterizing the discreteness between the tracked element's measured and theoretical contents, thusing avoiding the uncertainty associated with other indirect indicators. The convenience of the portable handheld XRF apparatus was confirmed, as it can be readily deployed in situ or ex situ to track calcium content within the stabilized mass after borehole sampling.
ABSTRACT COVID-19 is a multi-system disease affecting many organs outside of the lungs, and patients generally develop varying degrees of neurological symptoms. Whereas, the pathogenesis underlying these neurological manifestations remains elusive. Although in vitro models and animal models are widely used in studies of SARS-CoV-2 infection, human organ models that can reflect the pathological alterations in a multi-organ context are still lacking. In this study, we propose a new strategy to probe the effects of SARS-CoV-2 on human brains in a linked alveolus-BBB organ chip platform. The new multi-organ platform allows to recapitulate the essential features of human alveolar-capillary barrier and blood-brain barrier in a microfluidic condition by co-culturing the organ-specific cells. The results reveal direct SARS-CoV-2 exposure has no obvious effects on BBB chip alone. While, infusion of endothelial medium from infected alveolus chips can cause BBB dysfunction and neuroinflammation on the linked chip platform, including brain endothelium disruption, glial cell activation and inflammatory cytokines release. These new findings suggest that SARS-CoV-2 could induce neuropathological alterations, which might not result from direct viral infection through hematogenous route, but rather likely from systemic inflammation following lung infection. This work provides a new strategy to study the virus-host interaction and neuropathology at an organ-organ context, which is not easily obtained by other in vitro models. This will facilitate to understand the neurological pathogenesis in SARS-CoV-2 and accelerate the development of new therapeutics. SUMMARY A linked human alveolus-BBB chip platform is established to explore the influences of SARS-CoV-2 on human brains in an organ-organ context. SARS-CoV-2 infection could induce BBB injury and neuroinflammation. The neuropathological changes are caused by SARS-CoV-2 indirectly, which might be mediated by systemic inflammation following lung infection, but probably not by direct viral neuroinvasion.
(1-x)Li2FeSiO4·xLi3PO4/C, i.e. Li2+xFe1-xPxSi1-xO4/C, are proposed as a novel cathode material for lithium ion batteries. (1-x)Li2FeSiO4·xLi3PO4/C composites are prepared by a citric acid assisted sol-gel method. A complete solid solution can be formed for any value of x if the calcination temperature is high enough. However, the coexistence of Li2FeSiO4-rich and Li3PO4-rich phases is confirmed when the calcination temperature is 700°C and x is higher than 0.1 and lower than 0.9. The discharge capacity declines with an increase in x when the current density is low, which is due to the reduction in the number of Fe2+/Fe3+ redox couples. When the applied current density is high enough (1 C or higher), Li2.05Fe0.95P0.05Si0.95O4 has the highest discharge capacity and capacity retention because of its best crystallinity, lowest charge transfer resistance and highest lithium ion diffusion coefficient. Lower calcination temperature leads to better pore size distribution, higher carbon content and smaller particle size, resulting in better electrochemical performance. The carbon network wraps and connects the Li2.05Fe0.95P0.05Si0.95O4 particles when the calcination temperature is 700°C, and it has a hierarchically porous structure. These features are of great benefit to its electrochemical performance.
Polymer electrolyte fuel cells (PEFCs) have shown significant advances in terms of performance, efficiency and durability for a wide range of applications. Flow-fields are crucial components that affect the water management and performance of PEFCs. The existence of gas channel and land configurations in the conventional flow-field designs render gas and water distribution highly non-uniform. Such issue can lead to a series of events detrimental to PEFC performance and longevity [1]. As an alternative, new type of flow-field such as metal foam has been introduced. In-depth understanding of water management in metal foam flow-field based PEFC is indispensable for the optimisation of performance and durability. Here, liquid water formation and transport across the 25 cm 2 metal foam flow-field based PEFC is evaluated using neutron radiography. A nickel foam was put on cathode aluminium plate and a silicone gasket was then placed around the foam to seal in gases. A vertical single-channel serpentine was used for the anode aluminium flow-field, as shown in Fig. 1 (a). All experiments were conducted at the cold neutron radiography (CONRAD) beamline facility at Helmholtz-Zentrum Berlin (HZB). The setup for neutron imaging has been described in [2]. The result showed the enhancement of mass transport and cell performance in the metal foam flow-field compared to the conventional triple-serpentine design. Correlation of performance to neutron radiography reveals that the performance deviation in the mass transport region is likely due to flooding issues. The metal foam flow-field based PEFC exhibits less flooding and better uniformity in the local water distribution compared with that of serpentine flow-field design (Fig. 1 (b)). [1] Wu, Y., et al. "Effect of serpentine flow-field design on the water management of polymer electrolyte fuel cells: An in-operando neutron radiography study." Journal of Power Sources 399 (2018): 254-263. [2] Wu, Y., et al. "Effect of compression on the water management of polymer electrolyte fuel cells: An in-operando neutron radiography study." Journal of Power Sources 412 (2019): 597-605. Figure 1
Effective water management is crucial for the optimal operation of low-temperature polymer electrolyte membrane fuel cells (PEMFCs). Excessive liquid water production can cause flooding in the gas diffusion electrodes and flow channels, limiting mass transfer and reducing PEMFC performance. To tackle this issue, a nature-inspired chemical engineering (NICE) approach has been adopted that takes cues from the integument structure of desert-dwelling lizards for passive water transport. By incorporating engraved, capillary microchannels into conventional flow fields, PEMFC performance improves significantly, including a 15% increase in maximum power density for a 25 cm
Malignant melanoma is a type of highly aggressive tumor, which has a strong ability to metastasize to brain, and 60–70% of patients die from the spread of the tumor into the central nervous system. Exosomes are a type of nano-sized vesicle secreted by most living cells, and accumulated studies have reported that they play crucial roles in brain tumor metastasis, such as breast cancer and lung cancer. However, it is unclear whether exosomes also participate in the brain metastasis of malignant melanoma. Here, we established a human blood–brain barrier (BBB) model by co-culturing human brain microvascular endothelial cells, astrocytes and microglial cells under a biomimetic condition, and used this model to explore the potential roles of exosomes derived from malignant melanoma in modulating BBB integrity. Our findings showed that malignant melanoma-derived exosomes disrupted BBB integrity and induced glial activation on the BBB chip. Transcriptome analyses revealed dys-regulation of autophagy and immune responses following tumor exosome treatment. These studies indicated malignant melanoma cells might modulate BBB integrity via exosomes, and verified the feasibility of a BBB chip as an ideal platform for studies of brain metastasis of tumors in vitro.
Abstract Early human brain development can be affected by multiple prenatal factors that involve chemical exposures in utero, maternal health characteristics such as psychiatric disorders, and cancer. Breast cancer is one of the most common cancers worldwide arising pregnancy. However, it is not clear whether the breast cancer might influence the brain development of fetus. Exosomes secreted by breast cancer cells play a critical role in mediating intercellular communication and interplay between different organs. In this work, we engineered human induced pluripotent stem cells (hiPSCs)-derived brain organoids in an array of micropillar chip and probed the influences of breast cancer cell (MCF-7) derived-exosomes on the early neurodevelopment of brain. The formed brain organoids can recapitulate essential features of embryonic human brain at early stages, in terms of neurogenesis, forebrain regionalization, and cortical organization. Treatment with breast cancer cell derived-exosomes, brain organoids exhibited enhanced expression of stemness-related marker OCT4 and forebrain marker PAX6. RNA-seq analysis reflected several activated signaling pathways associated with breast cancer, medulloblastoma and neurogenesis in brain organoids induced by tumor-derived exosomes. These results suggested that breast cancer cell-derived exosomes might lead to the impaired neurodevelopment in the brain organoids and the carcinogenesis of brain organoids. It potentially implies the fetus of pregnant women with breast cancer has the risk of impaired neurodevelopmental disorder after birth.
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