286 research outputs found
In-situ TEM study of carbon nanomaterials and thermoelectric nanomaterials
No full textThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from PDF version of thesis.Includes bibliographical references (p. 103-112).Graphene nanoribbons (GNRs) are quasi one dimensional structures which have unique transport properties, and have a potential to open a bandgap at small ribbon widths. They have been extensively studied in recent years due to their high potential for future electronic and spintronic device applications. The edge structures - including the edge roughness and chirality - dramatically affect the transport, electronic, and magnetic properties of GNRs, and are of the critical importance. We have developed an efficient way of modifying the edges structures, to produce atomically smooth zigzag and armchair edges by using insitu TEM with a controlled bias. This work provides us with many opportunities for both fundamental studies and for future applications. I also report the use of either furnace heating or Joule heating to pacify the exposed graphene edges by loop formation in the graphitic nanoribbons. The edge energy minimization process involves the formation of loops between adjacent graphene layers. An estimation of the temperature during in-situ Joule heating is also reported based on the melting and evaporation of Pt nanoparticles. In this thesis work, I have also investigated the morphological and electronic properties of GNRs grown by chemical vapor deposition. Our results suggest that the GNRs have a surprisingly high crystallinity and a clean surface. Both folded and open edges are observed in GNRs. Atomic resolution scanning tunneling microscopy (STM) images were obtained on the folded layer and the bottom layer of the GNR, which enables clear identification of the chirality for both layers. We have also studied the electronic properties of the GNRs using low temperature scanning tunneling spectroscopy (STS). Our findings suggest that edges states exist at GNR edges which are dependent on the chiral angles of the GNRs.by Xiaoting Jia.Ph.D
Jeholornis prima Zhou 2002
No full textEMENDED DIAGNOSIS OF <i>J.</i> <i>PRIMA</i> <p> Based on the morphological study of this specimen, we provide the following revised diagnosis for <i>J. prima</i>. A large stem bird with the following combination of features: premaxilla edentulous with short maxillary process; two teeth with blunt crowns in maxilla and three relatively smaller teeth in dentary (new); paired, sheet-like preorbital ossifications present near the nasals (new, autapomorphy); C-shaped lacrimal with short rostrodorsal ramus and lacrimal foramen (new); unreduced postorbital forming a complete postorbital bar with jugal (new); pterygoid rami of vomer much longer than the fused rostral portion, expanded in the middle and lacking the caudodorsal process (new); palatine with broad pterygoid wing and jugal process (new); narrow and restricted mandibular fenestra between prearticular and surangular (new); 27 caudal vertebrae in total, with the transition point occurring after the fifth vertebra; lateral trabecula of sternum absent; caudalmost pair of sternal ribs expanded; first phalanx of the third manual digit twice as long as the second phalanx; ratio of forelimb (humerus plus ulna plus carpometacarpus) to hindlimb (femur plus tibiotarsus plus tarsometatarsus) of ~1.2:1; dorsal margin of the ilium nearly straight and craniodorsal–caudoventrally oriented (modified from Zhou & Zhang, 2002; O’Connor <i>et al.</i>, 2012; Zheng <i>et al.</i>, 2020).</p>Published as part of <i>Hu, Han, Wang, Yan, Fabbri, Matteo, O, Jingmai K., Connor, Mcdonald, Paul G., Wroe, Stephen, Yin, Xuwei, Zheng, Xiaoting, Zhou, Zhonghe & Benson, Roger B. J., 2023, Cranial osteology and palaeobiology of the Early Cretaceous bird Jeholornis prima (Aves: Jeholornithiformes), pp. 93-112 in Zoological Journal of the Linnean Society 198 (1)</i> on page 107, DOI: 10.1093/zoolinnean/zlac089, <a href="http://zenodo.org/record/7926859">http://zenodo.org/record/7926859</a>
Lactate Induces Tumor Progression via LAR Motif-Dependent Yin-Yang 1 Degradation
No full textThe metabolic reprogramming of aerobic glycolysis contributes to tumorigenesis. High plasma lactate is a critical regulator in the development of many human malignancies; however, the underlying molecular mechanisms of cancer progression in response to lactate (LA) remain elusive. Here, we show that the reduction of Yin-Yang 1 (YY1) expression correlated with high LA commonly occurs in various cancer cell types, including B-lymphoma and cervical cancer. Mechanistically, LA induces YY1 nuclear export and degradation via HSP70-mediated autophagy adjacent to mitochondria in a histidine (His)-rich LA-responsive (LAR) motif-dependent manner. The mutation of the LAR motif blocks LA-mediated YY1 cytoplasmic accumulation and in turn enhances cell apoptosis. Furthermore, low expression of YY1 promotes colony formation, invasion, angiogenesis, and growth of cancer cells in response to LA in vitro and in vivo using a murine xenograft model. Taken together, our findings reveal a key LAR element and may serve as therapeutic target for intervening cancer progression.Implications: We have shown that lactate can induce YY1 degradation via its His-rich LAR motif and low expression of YY1 promotes cancer cell progression in response to lactate, leading to better prediction of YY1 targeting therapy.</p
Wu Bochao’s Beixin Music Theory Textbook and Its Enlightenment for the Contemporary Era
No full textThis study examines Beixin Music Theory Teaching Book (1930) by Wu Bochao, a significant music textbook from the Republic of China era, focusing on its compilation background, content structure, editorial features, and contemporary relevance. As a core material for junior high school music education, the textbook reflects the transformation of Chinese music textbooks from singing collections to comprehensive works during that period. The research first contextualizes Wu Bochao’s musical contributions and the historical context of the textbook, then analyzes its structure—divided into three parts: music fundamentals, musical knowledge, and harmony outlines—and its content covering basic theory, techniques, and exercises. Key features include comprehensive and systematic content, integration of practicality and professionalism, and a blend of era characteristics and practicality. Despite limitations like insufficient music appreciation content and excessive difficulty, the textbook offers insights for modern music textbook compilation, emphasizing student-centered concepts and balanced content arrangement
Performance analysis on a large scale borehole ground source heat pump in Tianjin cultural centre
No full textImproving the performance of heterogeneous multi-core processors by modifying the cache coherence protocol
No full textAuthor Correction: Placental growth factor exerts a dual function for cardiomyogenesis and vasculogenesis during heart development
Full text linkCorrection to: Nature Communications, published online 05 September 2023 The original version of this Article omitted from the author list the 9th author, Miia L. Lehtinen, who is from the Department of Cell and Molecular Biology, Karolinska Institutet and Department of Cardiac Surgery, Heart and Lung Center, Helsinki University Hospital and University of Helsinki, Helsinki, Finland. The corrected version of the Acknowledgements removes the following from the original version: ‘Miia Lehtinen.’ Additionally, the following was added to the Author Contributions: ‘M.L.L. performed in vivo experiments relating to the primate works.’ This has been corrected in both the PDF and HTML versions of the Article.</p
RhoA/ROCK xin hao tong lu zai fa yu zhong xiao shu chang dao nei di yuan xing shen jing ji xi bao qian yi zhong de zuo yong
No full textPh.D.The enteric nervous system (ENS) originates from neural crest cells (NCCs) at two different levels along the neuraxis: vagal (somites 1-7) and sacral (caudal to somite 24 in the mouse) levels. While the development of vagal NCCs has been widely studied, little has been known about sacral NCCs, particularly in mammals. The objective of the present study was to determine whether the RhoA/ROCK pathway regulates sacral NCC migration in the developing mouse gut.First, it was found that the RhoA activity was concentrated in the leading edge of migrating sacral NCCs as detected by a fluorescent RhoA-FRET biosensor in vitro. Next, when cultured sacral NCCs emigrated from the pelvic ganglia were treated with different concentrations of Y-27632 to suppress active ROCK in vitro, significant decreases in the migration distance and fiber extension of sacral NCCs emigrated from the pelvic ganglion were observed.Immunofluorescent localization demonstrated that the expression of cofilin which is a downstream protein of the RhoA/ROCK pathway remained unchanged while its phosphorylated form p-cofilin (inactive state) was increased significantly when sacral NCCs were treated with Y-27632 in vitro. Expression of F-actin, which was immunostained by a phalloidin probe, was decreased after Y-27632 treatment. Time-lapse live cell imaging also showed that the speed and persistence of sacral NCC migration after Y-27632 treatment were decreased, and their directional migration was disrupted.An embryonic gut explant culture system, where a pelvic ganglion (serving as a cell source of sacral NCCs) was recombined with a recipient hindgut segment, was then established to study the migration and differentiation of sacral NCCs ex vivo. Immunofluorescence staining on whole-mount preparations and cryosections showed that the migration and differentiation of endogenous vagal NCCs in the hindgut explant cultured ex vivo were similar to those in the hindgut developed from E12.5 to E16.5 in vivo. The gut culture explant system hence appeared to be able to support the normal development of the hindgut explant ex vivo for at least 4 days. The hindgut explant was then used as a recipient gut segment for tissue recombination with a pelvic ganglion from which GFP-labelled sacral NCCs migrated into the recipient hindgut segment. Two days after the recipient hindgut segment was combined with the pelvic ganglion, the recombined tissues were treated with different concentrations of Y-27632. It was found that Y-27632 reduced the migration distance, cell number and axonal extension of sacral NCCs from the pelvic ganglion to the hindgut explant, but did not change their proliferation and apoptosis rates of sacral NCCs within the hindgut segment.In summary, these observations provide evidence that the RhoA/ROCK pathway was involved in the regulation of sacral NCC migration by modulating F-actin formation and also affected the directional migration of sacral NCCs migration in the developing mouse gut.腸道神經系統起源於神經軸上的兩種神經嵴細胞：迷走源性神經嵴細胞（位於體節 1-7）和骶源性神經嵴細胞 （在小鼠中位於尾端至體節24），儘管迷走源性神經嵴細胞的發育研究已經被廣泛地研究，但是在哺乳動物中有關骶源性神經嵴細胞的研究卻很少。此項研究的目的是確定RhoA/ROCK信號通路是否會影響小鼠胚胎腸道內的骶源性神經嵴細胞的遷移。透過使用熒光共振能量轉移技術的熒光RhoA生物傳感器， RhoA蛋白的活性被發現主要集中在遷移中的骶源性神經嵴細胞的前緣區域。在體外培養環境下，從盆腔神經節遷移出來的骶源性神經嵴細胞在不同濃度的抑制活性ROCK藥物Y-27632中培養，結果表明Y-27632顯著地減少了神經纖維的延伸和骶源性神經嵴細胞的遷移。熒光免疫定位實驗表明，用含有Y-27632的培養液培養骶源性神經嵴細胞後，RhoA/ROCK 信號通路的下游蛋白之一cofilin的總表達量沒有變化但是其磷酸化形式p-colilin（非活化狀態）卻顯著地增加了。 透過運用phalloidin試劑的免疫染色, F-actin的表達量在經過Y-27632處理後被發現降低了。實時活細胞成像結果表明骶源性神經嵴細胞在經過Y-27632處理後，其遷移的凈速度和方向的一貫性降低了， 以及其方向性遷移都受到了干擾。為研究骶源性神經嵴細胞在小鼠腸道內的遷移和分化的情況， 盆神經節 （提供骶源性神經嵴細胞的組織）和受體腸道在體外被組合， 以建立一個體外胚胎腸道培養系統。 腸道組織整體製片和冰凍切片的熒光免疫染色結果表明在經過體外培養的的後腸外植體之內的內源性迷走源性神經嵴細胞的遷移和分化情況與體內發育的12.5到16.5胚胎日的後腸內的迷走源性神經嵴細胞類似。因此，這些結果顯示體外胚胎腸道培養系統能支持胚胎腸道外植體至少四天的正常發育。所以後腸外植體被用作受體腸道片段并與盆神經節組合以讓帶有GFP標記的骶源性神經嵴細胞遷移進受體後腸片段。 在受體後腸片段與盆神經節組合的兩天後，組合了的組織在不同濃度的Y-27632中繼續培養。實驗結果表明Y-27632降低了骶源性神經嵴細胞由盆神經節向後腸外植體的遷移距離，細胞數量以及神經纖維的延伸，但是沒有影響他們在後腸外植體的增殖和凋亡比率。總結來說，這些實驗現象表明RhoA/ROCK 信號通路通過調控F-actin的形成以及調節骶源性神經嵴細胞的定向遷移，並在發育中小鼠腸道內骶源性神經嵴細胞的定向遷移過程中發揮作用。Zhang, Xiaoting.Thesis Ph.D. Chinese University of Hong Kong 2017.Includes bibliographical references (leaves 230-253).Abstracts also in Chinese.Title from PDF title page (viewed on …).Zhang, Xiaoting
Research on the Protective Effects of Different Chinese Medicine Compounds on Gefitinib-Induced Hepatotoxicity
No full textObjective Our objective was to screen drugs with good protective effects on gefitinib-induced hepatotoxicity
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