329 research outputs found

    Quantifying Fluid Shear Stress in a Rocking Culture Dish

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    Fluid shear stress (FSS) is an important stimulus for cell functions. Compared with the well established parallel-plate and cone-and-plate systems, a rocking “see-saw” system offers some advantages such as easy operation, low cost, and high throughput. However, the FSS spatiotemporal pattern in the system has not been quantified. In the present study, we developed a lubrication-based model to analyze the FSS distributions in a rocking rectangular culture dish. We identified an important parameter (the critical flip angle) that dictates the overall FSS behaviors and suggested the right conditions to achieving temporally oscillating and spatially relatively uniform FSS. If the maximal rocking angle is kept smaller than the critical flip angle, which is defined as the angle when the fluid free surface intersects the outer edge of the dish bottom, the dish bottom remains covered with a thin layer of culture medium. The spatial variations of the peak FSS within the central 84% and 50% dish bottom are limited to 41% and 17%, respectively. The magnitude of FSS was found to be proportional to the fluid viscosity and the maximal rocking angle, and inversely proportional to the square of the fluid depth-to-length ratio and the rocking period. For a commercial rectangular dish (length of 37.6 mm) filled with ∼2 mL culture medium, the FSS at the center of the dish bottom is expected to be on the order of 0.9 dyn/cm2 when the dish is rocked +5° at 1 cycle/s. Our analysis suggests that a rocking “see-saw” system, if controlled well, can be used as an alternative method to provide low-magnitude, dynamic FSS to cultured cells

    Financing Mode of American Small and Medium-sized Enterprises and the Enlightenment to Our Country

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    Because of the characteristic of small and medium-sized enterprises such as small scale of assets, low transparency message and heavy uncertainty of management, the financing mode of small and medium-sized enterprises of various countries is the same basically. This paper reflect the characteristic of the financing mode of small and medium-sized enterprises of our country indirectly through studying the financing mode and characteristics of American small and medium-sized enterprises, expecting to enlighten alleviating the difficulty of financing of small and medium-sized enterprises of our country . Key words: Financing mode, Characteristic, Enlightenment Résumé : La modèle de fusion des petites et moyennes entreprises dans tous les pays existe des points communs , en raison de ses quelques caractéristiques suivantes : les capitaux de petite envergure , la transparence insuffisante des informations et l’instabilité de gestion . A travers la recherche sur la modèle de fusion des petites et moyennes entreprises aux états-unis , ce texte reflète de façon indirecte les traits de modèle de fusion des petites et moyennes entreprises en Chine dans l’espoir de donner l’inspiration à l’atténuation des difficultés de la fusion des petites et moyennes entreprises de notre pays . Mots-clés: modèle de diffusion, traits , inspiration 摘要:由於中小企業具有資產規模小,資訊透明度低,經營不確定性大等特徵,各國中小企業融資模式存在一定的共同之處。本文通過研究美國中小企業融資模式及其特徵,間接反映了我國中小企業融資模式的特點,期望對緩解我國中小企業融資困難有所啟示。 關鍵詞:融資模式;特徵;啟

    Effect of Low-magnitude, High-frequency Vibration on Osteocytes in the Regulation of Osteoclasts

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    Osteocytes are well evidenced to be the major mechanosensor in bone, responsible for sending signals to the effector cells (osteoblasts and osteoclasts) that carry out bone formation and resorption. Consistent with this hypothesis, it has been shown that osteocytes release various soluble factors (e.g. transforming growth factor-β, nitric oxide, and prostaglandins) that influence osteoblastic and osteoclastic activities when subjected to a variety of mechanical stimuli, including fluid flow, hydrostatic pressure, and mechanical stretching. Recently, low-magnitude, high-frequency (LMHF) vibration (e.g., acceleration less than \u3c 1 × g, where g = 9.81 m/s2, at 20–90 Hz) has gained much interest as studies have shown that such mechanical stimulation can positively influence skeletal homeostasis in animals and humans. Although the anabolic and anti-resorptive potential of LMHF vibration is becoming apparent, the signaling pathways that mediate bone adaptation to LMHF vibration are unknown. We hypothesize that osteocytes are the mechanosensor responsible for detecting the vibration stimulation and producing soluble factors that modulate the activity of effector cells. Hence, we applied low-magnitude (0.3 × g) vibrations to osteocyte-like MLO-Y4 cells at various frequencies (30, 60, 90 Hz) for 1 h. We found that osteocytes were sensitive to this vibration stimulus at the transcriptional level: COX-2 maximally increased by 344% at 90 Hz, while RANKL decreased most significantly (−55%, p \u3c 0.01) at 60 Hz. Conditioned medium collected from the vibrated MLO-Y4 cells attenuated the formation of large osteoclasts (≥ 10 nuclei) by 36% (p \u3c 0.05) and the amount of osteoclastic resorption by 20% (p = 0.07). The amount of soluble RANKL (sRANKL) in the conditioned medium was found to be 53% lower in the vibrated group (p \u3c 0.01), while PGE2 release was also significantly decreased (−61%, p \u3c 0.01). We conclude that osteocytes are able to sense LMHF vibration and respond by producing soluble factors that inhibit osteoclast formation

    Towards Crowd-aware Indoor Path Planning (Extended Version)

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    Indoor venues accommodate many people who collectively form crowds. Such crowds in turn influence people's routing choices, e.g., people may prefer to avoid crowded rooms when walking from A to B. This paper studies two types of crowd-aware indoor path planning queries. The Indoor Crowd-Aware Fastest Path Query (FPQ) finds a path with the shortest travel time in the presence of crowds, whereas the Indoor Least Crowded Path Query (LCPQ) finds a path encountering the least objects en route. To process the queries, we design a unified framework with three major components. First, an indoor crowd model organizes indoor topology and captures object flows between rooms. Second, a time-evolving population estimator derives room populations for a future timestamp to support crowd-aware routing cost computations in query processing. Third, two exact and two approximate query processing algorithms process each type of query. All algorithms are based on graph traversal over the indoor crowd model and use the same search framework with different strategies of updating the populations during the search process. All proposals are evaluated experimentally on synthetic and real data. The experimental results demonstrate the efficiency and scalability of our framework and query processing algorithms.Comment: The extension of a VLDB'21 paper "Towards Crowd-aware Indoor Path Planning

    Effect of Nitric Oxide Treatment on Storage Quality of Glorious Oranges

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    AbstractEffect of nitric oxide (NO) treatment on storage quality and disease resistance of Glorious oranges was investigated in the experiment. The results showed that NO treatment could effectively reduce disease incidence inoculated with Collletotichum goeosporioides Penz and inhibit the increase of lesion diameter of Glorious oranges during storage. Compared with the control, NO treatment kept higher level of titritable acidity (TA), soluble protein, ascorbic acid (ASA) and reducing sugar, and lower level of weight lose rate and soluble solid concentration (SSC), retarding ripening of fruits