Heat conduction mechanisms in nanofluids and suspensions

Nanofluids, liquids containing suspensions of nanoparticles, have been reported by some groups to exhibit substantially higher thermal conductivity than that of their corresponding base fluids that cannot be explained by existing theories. However, the reported high thermal conductivity sometimes cannot be reproduced by others. Potential mechanisms leading to this enhancement are still under scrutiny. In this paper, we first take a critical review of heat conduction mechanisms proposed in literature, and then summarize our work. Our experimental studies demonstrate that nanoparticle clustering is the key contributor to the thermal conductivity enhancement. Guided by this insight, we use graphite flakes as additives and develop a method to prepare stable graphite suspensions with large thermal conductivity enhancement in water and oil. We also observe thermal percolation phenomenon and explained the phenomenon based on combined optical and AC impedance spectroscopy studies. We demonstrate temperature regulation of electrical and thermal properties of graphite suspensions through solid–liquid phase change, which may potentially be useful in energy systems in the future.United States. Air Force Office of Scientific Research (AFOSR FA9550-11-1-0174)China. Fundamental Research Funds for the Central Universitie

Class-level Multiple Distributions Representation are Necessary for Semantic Segmentation

Existing approaches focus on using class-level features to improve semantic segmentation performance. How to characterize the relationships of intra-class pixels and inter-class pixels is the key to extract the discriminative representative class-level features. In this paper, we introduce for the first time to describe intra-class variations by multiple distributions. Then, multiple distributions representation learning(\textbf{MDRL}) is proposed to augment the pixel representations for semantic segmentation. Meanwhile, we design a class multiple distributions consistency strategy to construct discriminative multiple distribution representations of embedded pixels. Moreover, we put forward a multiple distribution semantic aggregation module to aggregate multiple distributions of the corresponding class to enhance pixel semantic information. Our approach can be seamlessly integrated into popular segmentation frameworks FCN/PSPNet/CCNet and achieve 5.61\%/1.75\%/0.75\% mIoU improvements on ADE20K. Extensive experiments on the Cityscapes, ADE20K datasets have proved that our method can bring significant performance improvement

Analyzing characteristics of collateral flow to parasylvian cortical arteries by three-dimensional digital subtraction angiography–magnetic resonance angiography fusion imaging in adult moyamoya disease

ObjectiveThe hemodynamic sources of recipient parasylvian cortical arteries (PSCAs) were significantly related to postoperative cerebral hyperperfusion (CHP) after bypass surgery in patients with moyamoya disease (MMD). The present study aimed to introduce a new method to investigate the characteristics of PSCAs hemodynamic sources and their relationships with clinical presentations in adult MMD and to provide preoperative evaluation for recipient vessel selection in MMD bypass surgery.MethodsThe hemodynamic sources of the PSCAs in 171 symptomatic MMD hemispheres were analyzed by three-dimensional digital subtraction angiography (3D-DSA) combined with magnetic resonance angiography (MRA) fusion imaging. The spatial and temporal characteristics of the hemodynamic sources of the PSCAs and their associations with the patient's demographics, Suzuki stage, and initial onset type were investigated.ResultsSix major types of hemodynamic sources in the PSCAs were observed. There was a significant difference between the hemodynamic sources of the PSCAs above and below the SF (P < 0.001). With advancing Suzuki stages, collateral flow to the PSCAs above the SF from the internal carotid arteries (ICAs) significantly decreased, while the non-ICAs increased (P < 0.001). Multivariate analysis revealed that hemodynamic sources of the PSCAs above the SF were significantly associated with patients' initial onset type (P = 0.026).ConclusionIn MMD hemispheres, the hemodynamic sources of the PSCAs above the SF are more varied than those below the SF and present a typical conversion trend from ICAs to non-ICAs with advancing Suzuki stages. Analyzing the hemodynamic sources of the PSCAs can help in understanding the conversion pattern of compensatory vascular systems, predicting episodes in MMD, and preoperatively evaluating suitable recipient vessel selection for bypass surgery to avoid postoperative CHP

How does authentic leadership promote taking charge: The mediating effect of team social capital and the moderating effect of absorptive capacity

Authentic leaders are consistent with the expectations of Chinese traditional cultural values for leaders. The purpose of this study is to take team internal social capital (TISC) as the mediating variable and individual absorptive capacity as the moderating variable to explore the relationship between authentic leadership and taking charge. We collected 337 questionnaires from China and used linear regression to explore the influencing mechanisms and boundary conditions. The study results showed that the trickle-down of authentic leadership and the trickle-round of TISC can directly promote employees’ taking charge. Further, individual absorptive capacity positively moderated the relationship between TISC and taking charge. Our study provides a new perspective of leadership support for employees to implement taking charge in the context of high-power distance in China. From the perspective of authentic leadership, it is verified that leadership support is a necessary condition to motivate employees to implement proactive behavior. Moreover, compared with the research on the influence of leadership on proactive behavior, team-related and organization-related factors have not received enough attention. According to the social learning theory, we constructed an integrated framework for the first time in which leadership, team, and individual jointly affect taking charge

Interferon-β-induced miR-155 inhibits osteoclast differentiation by targeting SOCS1 and MITF

AbstractIFN-β is induced via a c-fos dependent mechanism that is present downstream of the receptor activator of NF-κB ligand (RANKL)-RANK signal transduction cascade during osteoclast differentiation. Increased production of IFN-β in turn inhibits osteoclastogenesis. However, the mechanism by which IFN-β exerts its suppressive function remains unclear. In the present study, we found that miR-155, an IFN-β-induced miRNA, mediated the suppressive effect of IFN-β on osteoclast differentiation by targeting SOCS1 and MITF, two essential regulators of osteoclastogenesis. These findings have not only demonstrated that miR-155 inhibits osteoclast differentiation, but also provided a new therapeutic target for treatment of osteoclast-mediated diseases

Viscosity and Thermal Conductivity of Stable Graphite Suspensions Near Percolation

Nanofluids have received much attention in part due to the range of properties possible with different combinations of nanoparticles and base fluids. In this work, we measure the viscosity of suspensions of graphite particles in ethylene glycol as a function of the volume fraction, shear rate, and temperature below and above the percolation threshold. We also measure and contrast the trends observed in the viscosity with increasing volume fraction to the thermal conductivity behavior of the same suspensions: above the percolation threshold, the slope that describes the rate of thermal conductivity enhancement with concentration reduces compared to below the percolation threshold, whereas that of the viscosity enhancement increases. While the thermal conductivity enhancement is independent of temperature, the viscosity changes show a strong dependence on temperature and exhibit different trends with respect to the temperature at different shear rates above the percolation threshold. Interpretation of the experimental observations is provided within the framework of Stokesian dynamics simulations of the suspension microstructure and suggests that although diffusive contributions are not important for the observed thermal conductivity enhancement, they are important for understanding the variations in the viscosity with changes of temperature and shear rate above the percolation threshold. The experimental results can be collapsed to a single master curve through calculation of a single dimensionless parameter (a Péclet number based on the rotary diffusivity of the graphite particles).United States. Air Force Office of Scientific Research (FA9550-11-1-0174)National Natural Science Foundation (China) (51036003

Risk of COVID-19 Transmission Aboard Aircraft: An Epidemiological Analysis Based on the National Health Information Platform.

OBJECTIVES This study aims to investigate the risk of COVID-19 transmission on aircraft. METHODS We obtained data on all international flights to Lanzhou, China, from June 1 to August 1, 2020, through the Gansu Province National Health Information Platform and the official website of the Gansu Provincial Center for Disease Control and Prevention. Statistical analysis was then performed. RESULTS Three international flights arrived in Lanzhou. The flights had a total of 700 passengers, of whom 405 (57.9%) were male and 80 (11.4%) were children below age fourteen. Twenty-seven (3.9%) passengers were confirmed to have COVID-19. Confirmed patients were primarily male (17, 65.4%) with a median age of 27.0 years. The majority of confirmed cases were seated in the middle rows of the economy class, or near public facility areas such as restrooms and galleys. The prevalence of COVID-19 did not differ between passengers sitting on window, aisle or middle seats. Compared with passengers sitting on the same row up to two rows behind a confirmed case, passengers seated in the two rows ahead a confirmed case were at a slightly higher risk of being infected. CONCLUSIONS COVID-19 may be transmitted during a passenger flight, although there is still no direct evidence