366 research outputs found
Yi di yi xing yuan li ji suan chu tan tong xin xi liu lei Ʃ3 {112} jing jie
No full textM.Phil.CZTS is a promising low cost, earth abundant, and nontoxic solar cell absorber material for thin film solar cell. Grain boundary of CZTS is not well understood despite its significant influence on device performance. [1--4]This work is dedicated to the characterisation and passivation of quasi-S3 grain boundaries with (112) and (1 ¯1 ¯2 ¯) interfaces, which could be abundant experimentally. DFT calculations with GGA exchange functional is used to calculate the structure of those grain boundaries. Using modified wedge method, formation energies of reconstructed grain boundaries and relevant surfaces were calculated from various slabs. According to our calculations, we found repulsive anionanion terminated grain boundary with low formation energy. Such problematic grain boundaries may widely distributed in the device and hinder the performance. In addition to the structure studies, Electronic structures of low energy grain boundaries were calculated to understand their impact on device efficiency. Finally, Grain boundary passivated by Na and K was found to have low formation energy and electronically benign. Our results match very well with observations from previous experimental works. It provided a solid foundation for future studies of grain boundary engineering, which could be crucial to the success of CZTS.銅鋅錫硫是一種有前景的低成本、原科大量豐富和無毒的太陽能電池用太陽能電池吸收材料。銅鋅錫硫的晶界雖然對設備性能有重大影響，但並不被十分瞭解。 [1--4]這項研究專注於可能 在實驗常見的(112)和(1 ̅1 ̅2 ̅)界面的類Σ3 晶界的表徵和鈍化。利用 GGA 交換函數的第一性原理計算來計算晶界的結構。使用改進的楔形法，從各種板塊計算了重構晶界和相關表面的形成能。根據我們的計算，我們發現相斥的陰離子-陰離子晶界具有低的形成能。這種有問題的晶界可能廣泛分佈在設備中並阻礙其性能。除了結構研究外我們也計算了低能量晶界的電子結構，以瞭解其對器件效率的影響。最後，發現鈉和鉀能鈍化的晶界並具有低的形成能和良性電子結構。我們的結果與以前的實驗作品的觀察結果非常吻合。為未來的邊界工程研究奠定了堅實的基礎， 這對於銅鋅錫硫的成功至關重要。Wong, Man Hoi = 以第一性原理計算初探銅鋅錫硫類Ʃ3 {112}晶界 / 黃文愷.Thesis M.Phil. Chinese University of Hong Kong 2017.Includes bibliographical references (leaves 40-43).Abstracts also in Chinese.Title from PDF title page (viewed on 10, February, 2020).Wong, Man Hoi = Yi di yi xing yuan li ji suan chu tan tong xin xi liu lei Ʃ3 {112} jing jie / Huang Wenkai
Emerging roles of astrocytes in blood-brain barrier disruption upon amyloid-beta insults in Alzheimer’s disease
No full textBlood-brain barrier disruption occurs in the early stages of Alzheimer’s disease. Recent studies indicate a link between blood-brain barrier dysfunction and cognitive decline and might accelerate Alzheimer’s disease progression. Astrocytes are the most abundant glial cells in the central nervous system with important roles in the structural and functional maintenance of the blood-brain barrier. For example, astrocytic coverage around endothelial cells with perivascular endfeet and secretion of homeostatic soluble factors are two major underlying mechanisms of astrocytic physiological functions. Astrocyte activation is often observed in Alzheimer’s disease patients, with astrocytes expressing a high level of glial fibrillary acid protein detected around amyloid-beta plaque with the elevated phagocytic ability for amyloid-beta. Structural alterations in Alzheimer’s disease astrocytes including swollen endfeet, somata shrinkage and possess loss contribute to disruption in vascular integrity at capillary and arterioles levels. In addition, Alzheimer’s disease astrocytes are skewed into proinflammatory and oxidative profiles with increased secretions of vasoactive mediators inducing endothelial junction disruption and immune cell infiltration. In this review, we summarize the findings of existing literature on the relevance of astrocyte alteration in response to amyloid pathology in the context of blood-brain barrier dysfunction. First, we briefly describe the physiological roles of astrocytes in blood-brain barrier maintenance. Then, we review the clinical evidence of astrocyte pathology in Alzheimer’s disease patients and the preclinical evidence in animal and cellular models. We further discuss the structural changes of blood-brain barrier that correlates with Alzheimer’s disease astrocyte. Finally, we evaluate the roles of soluble factors secreted by Alzheimer’s disease astrocytes, providing potential molecular mechanisms underlying blood-brain barrier modulation. We conclude with a perspective on investigating the therapeutic potential of targeting astrocytes for blood-brain barrier protection in Alzheimer’s disease
Vasorelaxant effects of oleamide in rat small mesenteric artery indicate action at a novel cannabinoid receptor
No full textCUHK electronic theses & dissertations collection
No full textLeung, Man Hau.Thesis M.Phil. Chinese University of Hong Kong 2014.Includes bibliographical references (leaves 61-64).Abstracts also in Chinese.Title from PDF title page (viewed on 29, November, 2016)
An EP Introducing Chinese Music Elements: Hong Kong
No full textThis project aims at creating music based on the theme of Hong Kong. The author will use four Chinese music elements: instruments, performance techniques, emotional expressions, and flexibility of Chinese music instruments adapting to different music genres to create an EP that intends to talk about the history of Hong Kong, emotional changes, freedom, and hope. Four elements will all appear in each song. Four songs will be presented in the EP based on the four points of Hong Kong. By taking the advantages of technology in recording and social media platforms, Chinese music can be heard widely in the world. The EP will be focusing on using GuZheng to present by using audio visual materials, remixes, improvisation, and collaboration. The purpose of this EP is twofold: to break the stereotypes of Chinese music and to allow more people to know about the beauty of Chinese music.https://remix.berklee.edu/graduate-studies-production-technology/1200/thumbnail.jp
Murine Beta-Amyloid (1–42) Oligomers Disrupt Endothelial Barrier Integrity and VEGFR Signaling via Activating Astrocytes to Release Deleterious Soluble Factors
No full textTransgenic mouse models of Alzheimer’s disease (AD) overexpress mutations of the human amyloid protein precursor (APP) and presenilin-1 (PSEN1) genes, which are known causes of amyloid pathology in familial AD. However, animal models for studying AD in the context of aging and age-related co-morbidities, such as blood–brain barrier (BBB) disruptions, are lacking. More recently, aged and progeroid mouse models have been proposed as alternatives to study aging-related AD, but the toxicity of murine amyloid-beta protein (Aβ) is not well defined. In this study, we aimed to study the potential toxicity of murine Aβ on brain endothelial cells and astrocytes, which are important components of the BBB, using mouse brain endothelial cells (bEnd.3) and astrocytes (C8-D1A). Murine-soluble Aβ (1–42) oligomers (sAβO42) (10 µM) induced negligible injuries in an endothelial monolayer but induced significant barrier disruptions in a bEnd.3 and C8-D1A co-culture. Similar results of endothelial perturbation were observed in a bEnd.3 monolayer treated with astrocyte-conditioned medium (ACM) generated by astrocytes exposed to sAβO42 (ACM-sAβO42), while additional exogenous sAβO42 did not cause further damage. Western blot analysis showed that ACM-sAβO42 altered the basal activities of vascular endothelial growth factor receptor 2 (VEGFR2), eNOS, and the signaling of the MEK/ERK and Akt pathways in bEnd.3. Our results showed that murine sAβO42 was moderately toxic to an endothelial and astrocyte co-culture. These damaging effects on the endothelial barrier were induced by deleterious soluble factors released from astrocytes, which disrupted endothelial VEGFR2 signaling and perturbed cell survival and barrier stabilization
Holistic lifecycle investigation of alternative fuel - hydrogen
No full textThe shipping industry facilitates movement of huge amounts of cargoes at the most cost-effective manner when compared to other modes of freight transport. The industry experienced changes in the principal energy sources throughout the past few centuries, where developments are driven by a steady stream of technological advancement. Due to its many benefits, heavy fuel oil (HFO) has since 1970 been the fuel of choice for the maritime sector because of numerous improvements to the diesel engine. However, the continued use of fossil fuels is a concern in terms of sustainability. In 2050, it is anticipated that the production of greenhouse gases (GHG), mainly CO2, will increase by 50% to 250%. MEPC 72 adopted the "Initial IMO Strategy on Reduction of GHG Emissions from Ships" in 2018 with requests of specifically aligning with the Paris Agreement, aiming to reduce overall annual GHG emission by at least 50% relative to GHG level in 2008 by 2050. In shipping industry, there are several potential alternative fuels that may accomplish the radical reduction in CO2 emissions required to achieve the IMO's target in 2050. This paper seeks to investigate the hydrogen life cycle as an alternative fuel holistically by assessing the economic viability of the maritime industry’s adoption. To ensure consistency and reliability of results, primary and secondary data were gathered to gain a better understanding on the cost-competitiveness of hydrogen. The primary data consisted of interviews with various members employed in different areas of the maritime industry, while the secondary data consisted of literature from various sources that served as cross references. The interviewees are Mr Josiah Eng from Siemens Energy, Mr Tsuyoshi Yuri and Mr Seokho Yoon from Mitsui O.S.K Lines (MOL), and Mr Samuel Lee from PSA.
Upon analysis of the data, the study revealed several economic considerations that the maritime industry could undertake. The considerations include comparing the economic benefits of importing hydrogen from other nations against producing hydrogen locally. The study also identified challenges, opportunities for adopting hydrogen in mid and long term. Some challenges include the high price of producing and transporting hydrogen, the lack of infrastructure for hydrogen to be imported, and identifying the offtakers who will undertake the cost of hydrogen after being adopted in the maritime industry. However, the study also found various opportunities where hydrogen has enormous potential for decarbonizing the energy mix. Hydrogen may eventually overtake and could be the preferred choice of alternative fuel in the maritime industry in 2050. Production costs will decline over time because of continuously declining costs for producing renewable energy, economies of scale, lessons learned from current projects, and technology advancements. Green hydrogen will consequently become more affordable.
For the maritime industry to step up and adopt hydrogen as an alternative fuel in the maritime industry, the author has mentioned the necessity for investing, alignment of policies, and market creation and provided recommendations on what is required of the government, businesses, and consumers to guide the maritime industry towards adopting hydrogen economically by 2050.Bachelor of Science (Maritime Studies
The role of aerosol phase state on the heterogeneous OH oxidation of aqueous organic-inorganic aerosols
No full textM.Phil.Aerosols are the suspensions of tiny particles in air that have pivotal effects on climate and air quality. Organic compounds, which are found to be internally mixed with inorganic salts in aerosols, are subjected to heterogeneous oxidation initiated by gas-phase OH radicals through aerosol surficial interactions. The role of inorganic salts in heterogeneous reactivity and chemistry of organic compounds is yet unknown. On the other hand, aqueous droplets composed of inorganic salts and organic compounds can undergo phase separation into two separated phases, depending on composition and relative humidity (RH). Such phase separation behavior could also influence the heterogeneous reactivity. In this thesis, to gain a better fundamental understanding in the effects of salt and aerosol phase state on the OH-initiated oxidation of aqueous organic–inorganic aerosols over a range of RH, an aerosol system consisting of 3-methylglutaric acid (3-MGA) and ammonium sulfate (AS), which may exhibit both single liquid phase and two separated phases, was chosen as model system. An aerosol flow tube reactor and Direct Analysis in Real Time (DART) ionization source coupled with a high-resolution mass spectrometer were used to perform heterogeneous oxidation experiments and analyze the molecular information of the aerosols, respectively.In the first study, when the aqueous organic–inorganic aerosols exhibit a single liquid phase at high RH, the heterogeneous reaction pathways and major products formed are likely unaffected by the dissolved inorganic ions. On the other hand, a lower heterogeneous reactivity of organic compounds toward gas-phase OH radicals was observed when the salt was added. It is likely attributed to the lower surface concentration of 3-MGA at or near the aerosol surface resulted from the dissolved salt and concomitant enhanced water uptake, reducing the reactive collision probability between 3-MGA molecules and OH radicals at the interface. In the second study, at lower humidity, the aqueous 3-MGA/AS aerosols underwent liquid–liquid phase separation at ~72–74.6 % RH, with an organic-rich outer phase and an inorganic-rich inner phase. Phase-separated droplets showed higher reactivity towards gas-phase OH radicals, compared to droplets with a single liquid phase at higher RH. This could be explained by the uneven surface distribution of 3-MGA within the phase-separated droplets with more 3-MGA at the droplet surface, increasing reaction probability between 3-MGA molecules and OH radicals. For both single-phase and phase-separated aerosols, the heterogeneous reactivity exhibits a decreasing trend as RH increased. It can be attributed to the dilution effect and the subsequent higher 3-MGA concentration at lower RH which intensifies the parent decay initiated by alkoxy radicals. Since molecular distribution is important in determining reactivity, the heterogeneous OH reactivity of organic compounds that are potentially surface-active was also studied, using 3-methyltetrol sulfate esters as the model compound. Overall, the results have clearly demonstrated the significance of aerosol phase state and molecular distribution on the heterogeneous OH reactivity of organic compounds in the aqueous organic-inorganic aerosols. Yet, these heterogeneous oxidation mechanisms are typically not accounted for in large-scale atmospheric chemical transport model. The results should be considered in current models in order to better understand the sources, composition and fate of organic compounds in the atmosphere.氣溶膠是懸浮於空氣中的細小顆粒。有機化合物與中的無機鹽可以同時存在於氣溶膠內。這些有機化合物會在氣溶膠表面發生「非均相氧化」（液態氣溶膠和氣態羥自由基之間的氧化反應）。截至現時，無機鹽會對有機化合物「非均相氧化」的動力學和化學反應產生怎樣的影響仍有待闡釋。另一方面，由無機鹽和有機化合物構成的氣溶膠會視乎成分和相對濕度(RH)發生兩相分離，可能會影響到氧化期間的反應性。本論文旨在更對鹽和氣溶膠相態怎樣影響到有機–無機氣溶膠在不同濕度下的「非均相氧化」有更好的基本了解。本論文選了3-甲基戊二酸和硫酸銨（AS）組成的氣溶膠作研究對象，該氣溶膠既可以呈現液態單相，也可以呈現兩個液態分離相。氧化實驗於氣溶膠流管反應器中進行，並使用了電離源（DART）和高分辨率質譜儀進行實時分析氣溶膠的分子成分。第一部分的實驗結果顯示有機–無機氣溶膠在高濕度會呈現液態單相，並且溶解成離子的無機鹽對有機–無機氣溶膠非均相化學沒有太⼤影響。然而，無機鹽可能會影響到3-甲基戊二酸的表面濃度和氣溶膠的吸濕性，因而減低整體反應性。第二部分的實驗結果顯示3-甲基戊二酸/硫酸銨氣溶膠於較低的濕度（〜72–74.6 ％ RH）下進行了液態兩相分離，形成較多有機化合物的外相和較多無機化合物的內相。相較於單相的氣溶膠，兩相分離的氣溶膠因3-甲基戊二酸的表面分佈不平均，有更高的反應性。當濕度上升時，不論是單相還是兩相分離的氣溶膠，非均相反應性都有下降的趨勢。這可能歸因於稀釋效應以及隨著濕度上升而變得更低的3-甲基戊二酸濃度，減少了由烷氧自由基引起的化學反應。由於氣溶膠的分子分佈對反應性有重要影響，所以本論文亦研究了表面活性的3-甲基四硫醇硫酸酯的非均相反應性。總括而言，這項研究展⽰了氣溶膠的相態和分子分佈對有機–無機氣溶膠氧化的重要性，有助現今的大氣化學傳送模型理解大氣中的有機化合物的起源、構成和化學變化。Lam, Hoi Ki.Thesis M.Phil. Chinese University of Hong Kong 2020.Includes bibliographical references (leaves 109-119).Abstracts also in Chinese
Xiphophorus variatus
No full text<i>Xiphophorus variatus</i> (Meek) <p>(Fig. 49, [LU])</p> <p> Fig. 49. <i>Xiphophorus variatus</i>, 37.2 mm SL female (top), 27.7 mm SL male (bottom), Wong Lung Hang Stream.</p> <p> <b>Distribution.</b> Ho Chung River, Hoi Ha Stream, Shap Sze Heung area, Lam Tsuen River, Kau Lung Hang Lo Wai Stream, Wang Tong River (Chan, 2001); Sha Ha Stream (Maunsell Consultants Asia Limited, 2004); Sam Dip Tam Stream, Tso Kung Tam Stream (Mott Connell Limited, 2005); Lung Mei area (Halcrow China Limited, 2007); Big Wave Bay Stream (DSD, 2010); Tai Tam Tuk Reservoir (Lai, 2011); Pok Fu Lam Reservoir (Lai, 2011; GBIF.org, 2021); Tei Lung Hau area (Ove Arup & Partners Hong Kong Limited, 2011); Tai Sheung Tok area (Ove Arup & Partners Hong Kong Limited, 2014); Mui Tsz Lam stream (AECOM Asia Company Limited, 2016a; current survey); Hung Shui Kiu area (AECOM Asia Company Limited, 2016b); Tai O River (Atkins China Limited, 2016; current survey); Tseng Lan Shue area (Black & Veatch Hong Kong Limited, 2018); Ha Che area (Atkins China Limited, 2020); Pak Tin area (Tai Wai) (AECOM Asia Company Limited, 2021a); Sha Lo Tung Stream (AFCD, 2021c); Sai Kung River, Wong Lung Hang Stream, Pak Ngan Heung Stream, Tai Tei Tong Stream, Cheung Po Stream, Shek Kong Stream (DSD, 2021); Fung Yuen area, Chuen Lung area, Sha Kok Mei area, Pui O Stream, Tung Ma To Stream (GBIF.org, 2021); Tung Chung River (Green Power, 2021; current survey); Little Hawaii Stream, Tai Chung Hau Stream, Hoi Ha Stream, Tai Lung Wo Liu Stream, Yuen Tun Ha Stream, She Shan River, Tung Tsz Stream, Tan Shan River, Tsing Tam Tsuen Stream (Tsang & Dudgeon, 2021a); Tong Fuk River, Deep Water Bay Stream (current survey).</p> <p> <b>Native range.</b> Central and South America.</p> <p> <b>Remarks.</b> Often coexists with <i>Xiphophorus hellerii</i> in Hong Kong streams.</p>Published as part of <i>Chan, Jeffery C. F., Tsang, Alphonse H. F., Yau, Sze-man, Hui, Tommy C. H., Lau, Anthony, Tan, Heok Hui, Low, Bi Wei, Dudgeon, David & Liew, Jia Huan, 2023, The non-native freshwater fishes of Hong Kong: diversity, distributions, and origins, pp. 128-168 in Raffles Bulletin of Zoology 71</i> on pages 151-152, DOI: 10.26107/RBZ-2023-0012, <a href="http://zenodo.org/record/7815765">http://zenodo.org/record/7815765</a>
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