352 research outputs found
The PEROXIN11 protein family controls peroxisome proliferation in Arabidopsis
No full textPEROXIN11 ( PEX11) is a peroxisomal membrane protein in fungi and mammals and was proposed to play a major role in peroxisome proliferation. To begin understanding how peroxisomes proliferate in plants and how changes in peroxisome abundance affect plant development, we characterized the extended Arabidopsis thaliana PEX11 protein family, consisting of the three phylogenetically distinct subfamilies PEX11a, PEX11b, and PEX11c to PEX11e. All five Arabidopsis PEX11 proteins target to peroxisomes, as demonstrated for endogenous and cyan fluorescent protein fusion proteins by fluorescence microscopy and immunobiochemical analysis using highly purified leaf peroxisomes. PEX11a and PEX11c to PEX11e behave as integral proteins of the peroxisome membrane. Overexpression of At PEX11 genes in Arabidopsis induced peroxisome proliferation, whereas reduction in gene expression decreased peroxisome abundance. PEX11c and PEX11e, but not PEX11a, PEX11b, and PEX11d, complemented to significant degrees the growth phenotype of the Saccharomyces cerevisiae pex11 null mutant on oleic acid. Heterologous expression of PEX11e in the yeast mutant increased the number and reduced the size of the peroxisomes. We conclude that all five Arabidopsis PEX11 proteins promote peroxisome proliferation and that individual family members play specific roles in distinct peroxisomal subtypes and environmental conditions and possibly in different steps of peroxisome proliferation
Null Broadening Robust Adaptive Beamforming Algorithm Based on Power Estimation
No full textIn order to solve the problem of severely decreased performance under the situation of rapid moving sources and unstable array platforms, a null broadening robust adaptive beamforming algorithm based on power estimation is proposed in this paper. First of all, we estimate the interference signal power according to the characteristic subspace theory. Then, the correspondence between the signal power and steering vector (SV) is obtained based on the orthogonal property, and the interference covariance matrix (ICM) is reconstructed. Finally, with the aim of setting virtual interference sources, null broadening can be carried out. The proposed algorithm results in a deeper null, lower side lobes and higher tolerance of the desired signal steering vector mismatch under the condition of low complexity. The simulation results show that the algorithm also has stronger robustness
Quan you hua zhang liang wang luo chong zheng hua qun fang fa bu dong dian yu gong xing dui cheng xing de chan sheng
No full textLoop optimization for tensor network renormalization (Loop-TNR) method provides us very powerful tools to study strong correlated system on critical point with very high accuracy. We accurately simulate the phase diagram and critical behavior of the ferromagnetic q-state clock model on the square lattice by using the loop-TNR algorithm. The two phase transition points for q>= 6 are determined with extremely high accuracy. Furthermore, by accurately simulating the conformal scaling dimensions for both transition points, we are able to accurately determine the radius R of compactified boson theories at both transition points. In particular, the radius R at higher temperature phase transition is precisely the same as the predicted R for BKT transition. Finally, we also find that the radius R of compactified boson at self dual point precisely takes the value √2q, which is also consistent with previous theoretical predictions.In the next, we would see how conformal symmetry emerges at the critical point. By simulation on disordered q-state model with q=2,3,4 cases, we make a conclusion that the emergence of conformal symmetry on critical point is beyond the lattice symmetry. The conformal data read from these disordered model shows very strong evidence on that point. And then, we study the structure of the fixed point of RG flow of the tensor network with Z(q) symmetry, which would emerge U(1) symmetry at the critical point. By the structure of the rank-3 fixed point tensor, we see that up to the leading order of primary components, the fixed point tensor could be described by the 3-point correlation function of the CFT in the compactified boson.圈優化張量網路重整化群（loop-TNR）為研究強關聯系統的臨界點物理性質提供了一種高精度的數值重整化群方法。我們使用 loop-TNR 方法，精確地類比了鐵磁 q-state clock 模型的相圖及其臨界性質。我們以很高的精度確定了這一模型的兩個臨界點。此外，通過精確地計算兩個相變點的共形場論參數，我們可以精確地計算出對應的自由緊致玻色場的緊致半徑 R。特別地，在高溫的臨界點，緊致半徑 R 的數值結果與理論預測的 BKT 相變點的參數 R 高度近似。最後，我們得到，在自對偶點，自由緊致玻色場的緊致半徑 R 接近√2q 這非常符合理論預測。此外，我們研究了共形對稱性如何在臨界點產生。運用 loop-TNR 方法對一些具有無序相互作用的統計模型的類比，我們得出結論：共形對稱性在臨界點的產生與晶格對稱性無關。然後，我們研究了鐵磁 q-state clock 模型在 loop-TNR 方法中的重整化流的不動點性質，這一模型在臨界點會生成 U(1) 對稱性。通過對包含低能級初級場的 3 階張量結構的觀察，我們發現 loop-TNR 方法的三階不動點張量的低能級初級場張量元可以用自由緊致玻色場的三點關聯函數表示。Li, Guanrong = 圈優化張量網絡重整化群方法不動點與共形對稱性的產生 / 李冠融.Ph.D. Chinese University of Hong Kong 2021.Includes bibliographical references (leaves 75-85).Abstracts also in Chinese.Title from PDF title page (viewed on November 07, 2022).Li, Guanrong = Quan you hua zhang liang wang luo chong zheng hua qun fang fa bu dong dian yu gong xing dui cheng xing de chan sheng / Li Guanrong
JUNCTION CONDITIONS ON NULL HYPERSURFACES FOR SPHERICALLY SYMMETRICAL METRICS
No full textA necessary condition for the junction of two spherically symmetric metrics on a null hypersurface to satisfy Lichnerowicz's condition is derived. It is shown using this necessary condition that the junction of the Schwarzschild metric with the Gonzalez metric can never be c1, and the junction of the Reissner-Nordstrom metric with the metric suggested by Shen and Zhu can never be c1 either.Physics, MathematicalSCI(E)0ARTICLE61537-15403
Optimized antimicrobial and antiproliferative activities of titanate nanofibers containing silver
No full textYong Hua Su*, Zi Fei Yin*, Hai Liang Xin, Hui Qing Zhang, Jia Yu Sheng, Yan Long Yang, Juan Du, Chang Quan LingDepartment of Traditional Chinese Medicine, Changhai Hospital, The Second Military Medical University, Shanghai, People’s Republic of China*These authors contributed equallyAbstract: Titanate nanofibers containing silver have been demonstrated through the experiments reported herein to have effective antifungal and antiproliferative activities in the presence of UV light. The titanate nanofibers containing silver can be fabricated by means of ion exchange followed by a topochemical process in an environment suitable for reductive reactions. Excellent antibacterial, antifungal, and antiproliferative activities could be demonstrated by both Ag2Ti5O11 · xH2O and Ag/titanate (UV light irradiation) due to their unique structures and compositions, which have photocatalytic activities to generate reactive oxygen species and capabilities to continuously release the silver ions. Therefore these materials have the potential to produce a membrane for the treatment of superficial malignant tumor, esophageal cancer, or cervical carcinoma. They may also hold utility if incorporated into a coating on stents in moderate and advanced stage esophageal carcinoma or for endoscopic retrograde biliary drainage. These approaches may significantly reduce infections, inhibit tumor growth, and importantly, improve quality of life and prolong survival time for patients with tumors.Keywords: silver, titanate, photocatalytic, antiproliferative, antimicrobia
A Bio-inspired Approach to Cyber Security
No full textOwing to a growing reliance on information, technology and connectivity, Cyberspace has become the lifeline and interactive place for modern life. As such, Cyber security challenges are a global phenomenon whose adverse implications are catastrophic. Cyberspace is complex and unpredictable; its global connectedness and an explosion of data increases the threat surface as cyber infrastructures become highly complex and dynamic. Managing, i.e. ensuring and assuring security in cyberspace requires inspiration from advanced complex systems. Through evolution, nature has developed natural propensities in complex systems (including animalia and plants) that enable survival through adaptation. Predation-avoidance and anti-predation techniques employed by non-extinct preys could be exploited/adopted as mechanisms for adaptation through their application in Cyber security. This chapter presents an overall review of the current state of the Cyber security landscape. In addition, it demonstrates through further review, significant trends towards bio-inspired approaches as unconventional solutions to problems in other fields. Drawing from survivable preys in nature, the chapter speculates solutions for Cyberspace and Cyber security as follows; given an old problem (Pold) with an old solutions (Sold), a new problem (Pnew) can be conceptualized with new partial and perhaps null solutions (Snew) in the solutions space Sold to Snew.
Keywords: Bio-inspired, Artificial Life, Cyber security, Cyberdefense, Autonomic Computing, Survivability, Cloud Computing, Machine Learning, Predator-Prey
Na mi ke li cai liao yu yi miao ling yu ying yong de kai fa
No full textPh.D.The adoption of nanoparticle-based formulations in vaccine design has led to many breakthroughs such as therapeutic cancer vaccine against established cancer or experimental vaccines against autoimmunity. As published works on nanoparticle vaccines accumulates, it becomes clear that the advantages of nanoparticle formulations are deeply rooted to the fundamental working of the immune system. Along the sequence of biological events that lead to the formation of an effective immune response, MHC II antigen presentation by dendritic cell is a critical step in the activation of CD4+ T cells for coordination of pathogen defense or autoimmunity suppression. However, the effect of nanoparticle formulations on MHC II presentation was largely unclear. In this thesis, we developed a cell-level assay using bone marrow-derived dendritic cell (BMDC) as our model system, to analyze the effect of nanoparticle formulations on MHC II presentation. The assay was developed with emphasis on accurate quantification of antigen uptake by BMDC. This set our work apart from similar studies, which frequently overlooked or casually examined antigen uptake, allowing MHC II presentation to be analyzed in per unit antigen uptake manner. We determined that intrinsic nanoparticle properties such as size and decomposability widely employed for enhancing lymphatic transport and cross presentation had no significant effect on MHC II presentation. The same was found for common carrier systems such as liposome, PLGA and silica. Inspired by findings on redox-based regulation of phagosomal proteases involved in MHC II presentation, we finally designed a PLGA nanoparticle for co-delivery of antigen and thiol-functionalized reductant. We found that the nanoparticle enhanced MHC II presentation and induced a tolerogenic dendritic cell profile on the cell level. At system level, the nanoparticle induced an immunoregulation-like T cell and antibody response profile.在疫苗設計的領域中，採用納米顆粒的製劑已經導致許多突破：如針對既定癌症的治療性癌症疫苗、或針對自身免疫的實驗性疫苗。隨著已發表的納米顆粒疫苗的工作慢慢積累，納米顆粒製劑的優勢顯明是深深植根於免疫系統的運作。在形成有效免疫反應的生物反應流程中，樹突細胞的MHC II 抗原呈現是激活CD4 + T 細胞、以致產生病原體防禦或自身免疫抑制的關鍵步驟。然而，納米顆粒製劑對主要組織相容性複合物第二型（MHC II）呈現的影響尚不清楚。在本論文中，我們開發了一種使用骨髓來源的樹突狀細胞（BMDC）作為我們的模型系統的細胞水平測定方法，以分析納米顆粒製劑對MHCII 呈現的影響。開發該測定法的重點在於BMDC 對抗原攝取的準確定量。這使我們的工作有別於類似的研究。這些研究經常忽略或隨便檢查抗原攝取。準確的抗原攝取定量允許了我們以每單位抗原攝取方式去分析MHC II 呈現。基於這個測定方法，我們確定廣泛用於增強淋巴轉運或交叉呈現的納米顆粒性質（大小和可分解性）對MHC II 呈現沒有顯著影響。對於常見的載體系統如脂質體、聚乳酸乙醇酸（PLGA）和二氧化矽，對MHC II呈現也沒有顯著影響。啟發於氧化還原反應對MHC II 呈現相關的吞噬體蛋白酶的操控，我們最終設計了一款共同遞送抗原和硫醇功能化還原劑的PLGA 納米顆粒載體。我們發現該納米顆粒增強了MHC II 的表達並在細胞層面上誘導了致耐受性樹突細胞表現型。在系統層面上，納米顆粒誘導了類似於免疫調節的T 細胞和抗體反應譜。Lung, Ping Sai = 納米顆粒材料於疫苗領域應用的開發 / 龍平西."November 2019."Thesis Ph.D. Chinese University of Hong Kong 2020.Includes bibliographical references (leaves 90-105).Abstracts also in Chinese.Title from PDF title page (viewed on 20 May, 2021).Lung, Ping Sai = Na mi ke li cai liao yu yi miao ling yu ying yong de kai fa / Long Pingxi
Mechanical forces and magnetic field simulation of transformer with finite element method
No full textJi yu wu ding er yang hua gui na mi ke li de an quan gao xiao na mi yao wu de yan jiu
No full textWith recent development of nanoscience and nanotechnology, a great amount of efforts have been devoted to nanomedicine development. Among various nanomaterials, silica nanoparticle (NP) is generally accepted as non-toxic, and can provide a versatile platform for drug loading. In addition, the surface of the silica NP is hydrophilic, being favorable for cellular uptake. Therefore, it is considered as one of the most promising candidates to serve as carriers for drugs.The present thesis mainly focuses on the design of silica based nanocarrier-drug systems, aiming at achieving safe nanocarrier excretion from the biological system and enhanced drug efficacy, which two are considered as most important issues in nanomedicine development.To address the safe carrier excretion issue, we have developed a special type of self-decomposable SiO₂-drug composite NPs. By creating a radial concentration gradient of drug in the NP, the drug release occurred simultaneously with the silica carrier decomposition. Such unique characteristic was different from the conventional dense SiO₂-drug NP, in which drug was uniformly distributed and can hardly escape the carrier. We found that the controllable release of the drug was primarily determined by diffusion, which was caused by the radial drug concentration gradient in the NP. Escape of the drug molecules then triggered the silica carrier decomposition, which started from the center of the NP and eventually led to its complete fragmentation. The small size of the final carrier fragments enabled their easy excretion via renal systems.Apart from the feature of safe carrier excretion, we also found the controlled release of drugs contribute significantly to the drug efficacy enhancement. By loading an anticancer drug doxorubicin (Dox) to the decomposable SiO₂-methylene blue (MB) NPs, we achieved a self-decomposable SiO₂(MB)-Dox nanomedicine. The gradual escape of drug molecules from NPs and their enabled cytosolic release by optical switch, led to not only high but also stable drug concentration in cytosol within a sustained period. This resulted in enhanced drug efficacy, which is especially manifested in multidrug resistant (MDR) cancer cells, due to the fact that the NP-carrier drug can efficiently bypass the efflux mechanisms and increase drug availability. Together with its feature of spontaneous carrier decomposition and safe excretion, this type of nanomedicine’s high drug efficacy highlights its potential for low dose anticancer drug treatment and reduced adverse effect to biological system, holding great promise for clinical translation.The enhanced drug efficacy by employing the self-decomposable silica nanocarrier is also demonstrated in photodynamic therapy (PDT). The loose and fragmentable features of the self-decomposable SiO₂-photosensitizer (PS) NPs promoted the out-diffusion of the generated ROS, which resulted in a higher efficacy than that of dense SiO₂-PS NPs. On the other hand, we also explored another nanocarrier configuration of Au nanorods decorated SiO₂ NP, with PS drug embedded into dense SiO₂ matrix. A different mechanism of drug efficacy enhancement was presented as the Au’s surface plasmon resonance enhanced the ROS production. Although the drug efficacy of such SiO₂(PS)-Au NPs was similar to that of self-decomposable SiO₂-PS NPs, their potential for clinical applications was limited without the feature of safe carrier excretion.In summary, the self-decomposable SiO₂ based NP developed is a most promising system to serve as safe and effective carriers for drugs. Together with the known biocompatibility of silica, the feature of controllable drug release and simultaneous carrier decomposition achieved in the self-decomposable SiO₂-drug NPs make it ideal for a wide range of therapeutic applications.隨著近年來納米科學技術的快速發展，致力於納米藥物的研发也越來越多。在眾多納米材料體系中，二氧化硅納米顆粒因其無毒、易載藥、且易於細胞攝入等特性，被認為是最具前景的藥物載體之一。本文主要致力於設計以二氧化硅納米顆粒為載體的納米藥物體系，使之同時具備能夠被生物體安全排泄以降低潛在不良影響，并且能夠加強藥效的特性，而這兩方面被認為正是納米藥物發展中最重要的議題。爲了實現藥物載體安全排泄，我們設計了一種特殊類型可自降解的二氧化硅-藥物複合納米顆粒。通過在納米顆粒中控制形成徑向藥物濃度梯度分佈，我們達到了藥物釋放的同時伴隨二氧化硅載體解體的效果。這一特徵不同於傳統二氧化硅-藥物複合納米顆粒中藥物均勻分佈而難以擴散出載體的情況。我們發現在這種可自降解的二氧化硅-藥物複合納米顆粒中，首先徑向藥物濃度梯度分佈所引起的擴散控制著藥物釋放，而後藥物分子的流失促發二氧化硅載體由內而外的逐步分解，最終全面解體分裂成碎片。這些碎片的小尺度使得它們易於經泌尿系統安全排泄出體外。除此之外，我們發現這種納米載體的可控藥物釋放特性可以大大提高藥效。通過將抗癌藥阿黴素載入自降解二氧化硅-亞甲藍納米顆粒中，我們得到一種可自降解二氧化硅/亞甲藍-阿黴素(SiO₂(MB)-Dox)複合納米顆粒。藥物分子可以逐漸擴散出納米顆粒，並且在光控開關作用下釋放到細胞胞漿中，使之在胞漿中持續保持穩定高濃度。這樣使得藥效得以加強，尤其是在多藥抗藥性腫瘤細胞中作用尤為明顯，這得益於納米載體藥物可以有效避開藥泵機制并提高藥物利用率。除了它的自發載體分解和安全排泄特性，這種納米藥物的高藥效使得它在低藥量治療和減少不良副作用方面的潛力突出，臨床應用前景廣大。可自降解二氧化硅納米載體所帶來的的藥效增強亦顯示在光動力學治療法中。可自降解二氧化硅-光敏劑藥物(SiO₂-PS)複合納米顆粒鬆散易分解的結構特性促使其內部產生的活性氧物質易於擴散出藥物載體，這使得它的藥效高於傳統二氧化硅-光敏劑複合納米顆粒。另一方便，我們設計了一種金修飾的二氧化硅納米顆粒載體。它具有另一種不同的藥效增強機制，即利用金納米顆粒表面等離子體共振效應來增強活性氧物質的產生。雖然藥效與可自降解二氧化硅-光敏劑複合納米顆粒相似，但是它無法安全排泄，限制了其在臨床上的應用。綜上所述，我們發展的可自降解二氧化硅納米顆粒作為一種安全高效的藥物載體顯示出其非常大的應用前景。二氧化硅以其衆所周知的生物相容性，和我們發展的可控藥物釋放及同步載體分解特性，已成為理想的藥物載體并有希望廣泛適用於治療應用。Zhang, Silu = 基於無定二氧化硅納米顆粒的安全高效納米藥物的研究 / 張思鷺.Thesis (Ph.D.)--Chinese University of Hong Kong, 2014.Includes bibliographical references.Abstracts also in Chinese.Title from PDF title page (viewed on 12, October, 2016).Zhang, Silu = Ji yu wu ding er yang hua gui na mi ke li de an quan gao xiao na mi yao wu de yan jiu / Zhang Silu.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only.Detailed summary in vernacular field only
Human Capital, Economic Growth, and Regional Inequality in China
No full textWe study the dispersion in rates of provincial economic- and TFP growth in China. Our results show that regional growth patterns can be understood as a function of several interrelated factors, which include investment in physical capital, human capital, and infrastructure capital; the infusion of new technology and its regional spread; and market reforms, with a major step forward occurring following Deng Xiaoping’s “South Trip” in 1992. We find that FDI had much larger effect on TFP growth before 1994 than after, and we attribute this to emergence of other channels of technology transfer when marketization accelerated. We find that human capital positively affects output per worker and productivity growth. In particular, in terms of its direct contribution to production, educated labor has a much higher marginal product. Moreover, we estimate a positive, direct effect of human capital on TFP growth. This direct effect is hypothesized to come from domestic innovation activities. The estimated spillover effect of human capital on TFP growth is positive and statistically significant, which is very robust to model specifications and estimation methods. The spillover effect appears to be much stronger before 1994. We conduct cost-benefit analysis and a policy “experiment,” in which we project the impact increases in human capital and infrastructure capital on regional inequality. We conclude that investing in human capital will be an effective policy to reduce regional gaps in China as well as an efficient means to promote economic growth.Regional Inequality, China, Human Capital, Foreign Direct Investment, Spillovers, Technology Transmission
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