http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 저자 : Zachary Aman (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
-
Hydrate plug formation risk with varying watercut and inhibitor concentrations
Sohn, Young hoon,Kim, Jakyung,Shin, Kyuchul,Chang, Daejun,Seo, Yutaek,Aman, Zachary M.,May, Eric F. Elsevier 2015 Chemical engineering science Vol.126 No.-
<P><B>Abstract</B></P> <P>Hydrate formation introduces a potential operating and safety hazard in subsea oil and gas pipelines. The aggregation and deposition of hydrate particles together increase the resistance-to-flow in the pipeline, which dissipates the energy available to transport the resource and may even lead to a plug that blocks flow completely. The effects of 20–100% watercut and hydrate thermodynamic and kinetic inhibitors on both hydrate growth rate and resistance-to-flow have been studied in a high-pressure autoclave apparatus. The highest resistance-to-flow was observed for systems with around 60% watercut, for which oil-continuous condition existed for the majority of the hydrate growth period with free water available to bind both hydrate aggregates and deposits. Severe and periodic local maxima in the torque required to maintain a constant rotational speed were repeatedly observed in the autoclave at 60% watercut; these could be partially suppressed by adding 10wt% MEG to the water phase. The resistance-to-flow signal was fully suppressed in two system configurations: (i) 10wt% MEG with 0.5wt% of PVCap, a hydrate kinetic inhibitor; and (ii) 30wt% MEG. The results suggest that the injection of a thermodynamic inhibitor at less than 25% of the full inhibition requirement could be sufficient to alleviate the risk of a hydrate blockage. A simple model to describe hydrate growth in water- and oil-continuous systems was successfully deployed to predict hydrate growth rate in systems with varying watercut, with and without inhibitor.</P>
-
-
Lee, Yu Bin,Kim, Eun Mi,Byun, Hayeon,Chang, Hyung-kwan,Jeong, Kwanghee,Aman, Zachary M.,Choi, Yu Suk,Park, Jungyul,Shin, Heungsoo Elsevier 2018 Biomaterials Vol.165 No.-
<P><B>Abstract</B></P> <P>Numerous methods have been reported for the fabrication of 3D multi-cellular spheroids and their use in stem cell culture. Current methods typically relying on the self-assembly of trypsinized, suspended stem cells, however, show limitations with respect to cell viability, throughput, and accurate recapitulation of the natural microenvironment. In this study, we developed a new system for engineering cell spheroids by self-assembly of micro-scale monolayer of stem cells. We prepared synthetic hydrogels with the surface of chemically formed micropatterns (squares/circles with width/diameter of 200 μm) on which mesenchymal stem cells isolated from human nasal turbinate tissue (hTMSCs) were selectively attached and formed a monolayer. The hydrogel is capable of thermally controlled expansion. As the temperature was decreased from 37 to 4 °C, the cell layer detached rapidly (<10 min) and assembled to form spheroids with consistent size (∼100 μm) and high viability (>90%). Spheroidization was significantly delayed and occurred with reduced efficiency on circle patterns compared to square patterns. Multi-physics mapping supported that delamination of the micro-scale monolayer may be affected by stress concentrated at the corners of the square pattern. In contrast, stress was distributed symmetrically along the boundary of the circle pattern. In addition, treatment of the micro-scale monolayer with a ROCK inhibitor significantly retarded spheroidization, highlighting the importance of contraction mediated by actin stress fibers for the stable generation of spheroidal stem cell structures. Spheroids prepared from the assembly of monolayers showed higher expression, both on the mRNA and protein levels, of ECM proteins (fibronectin and laminin) and stemness markers (Oct4, Sox2, and Nanog) compared to spheroids prepared from low-attachment plates, in which trypsinized single cells are assembled. The hTMSC spheroids also presented enhanced expression levels of markers related to tri-lineage (osteogenic, chondrogenic and adipogenic) differentiation. The changes in microcellular environments and functionalities were double-confirmed by using adipose derived mesenchymal stem cells (ADSCs). This spheroid engineering technique may have versatile applications in regenerative medicine for functionally improved 3D culture and therapeutic cell delivery.</P>
-
Volume Adaptation Controls Stem Cell Mechanotransduction
Major, Luke G.,Holle, Andrew W.,Young, Jennifer L.,Hepburn, Matt S.,Jeong, Kwanghee,Chin, Ian L.,Sanderson, Rowan W.,Jeong, Ji Hoon,Aman, Zachary M.,Kennedy, Brendan F.,Hwang, Yongsung,Han, Dong-Wook American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.49
<P>Recent studies have found discordant mechanosensitive outcomes when comparing 2D and 3D, highlighting the need for tools to study mechanotransduction in 3D across a wide spectrum of stiffness. A gelatin methacryloyl (GelMA) hydrogel with a continuous stiffness gradient ranging from 5 to 38 kPa was developed to recapitulate physiological stiffness conditions. Adipose-derived stem cells (ASCs) were encapsulated in this hydrogel, and their morphological characteristics and expression of both mechanosensitive proteins (Lamin A, YAP, and MRTFa) and differentiation markers (PPARγ and RUNX2) were analyzed. Low-stiffness regions (∼8 kPa) permitted increased cellular and nuclear volume and enhanced mechanosensitive protein localization in the nucleus. This trend was reversed in high stiffness regions (∼30 kPa), where decreased cellular and nuclear volumes and reduced mechanosensitive protein nuclear localization were observed. Interestingly, cells in soft regions exhibited enhanced osteogenic RUNX2 expression, while those in stiff regions upregulated the adipogenic regulator PPARγ, suggesting that volume, not substrate stiffness, is sufficient to drive 3D stem cell differentiation. Inhibition of myosin II (Blebbistatin) and ROCK (Y-27632), both key drivers of actomyosin contractility, resulted in reduced cell volume, especially in low-stiffness regions, causing a decorrelation between volume expansion and mechanosensitive protein localization. Constitutively active and inactive forms of the canonical downstream mechanotransduction effector TAZ were stably transfected into ASCs. Activated TAZ resulted in higher cellular volume despite increasing stiffness and a consistent, stiffness-independent translocation of YAP and MRTFa into the nucleus. Thus, volume adaptation as a function of 3D matrix stiffness can control stem cell mechanotransduction and differentiation.</P> [FIG OMISSION]</BR>
연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
