164 research outputs found
In Vitro Study of the Cytotoxic Effects of Low- and High-molecular-weight Fucoidan Extracted from New Zealand Seaweed Undaria Pinnatifida in MCF-7 and MDA-MB-231 Breast Cancer Cell Lines
No full textBreast cancer is known as the top cancer for women worldwide. It is estimated that every year over one million new cases of breast cancer are diagnosed and contribute largely to cancer related deaths. Chemotherapy, including neoadjuvant therapy and adjuvant therapy, is a critical part in treatment for breast cancer that impact on survival and life quality for patients. However, chemo-resistance and adverse effects occur frequently when patients receive chemotherapy or the improved target therapies. New strategies have been proposed to enhance the effects of anticancer drugs as combing them with natural dietary compounds, decreasing drug dose administered and reducing the toxicity to normal cells.
Fucoidan is noticed for its anti-cancer potential in treating breast cancer as well as in many other cancers. It is a natural bioactive compound derived from brown algae that has low toxicity and multiple anti-cancer pathways, the potential of which makes it a candidate for therapeutic agent using alone or in combination with other cytotoxic drugs. Base on the molecular weight, fucoidan can be categorised into three ranges: high-molecular weight fucoidan (HMF, >300k), medium-molecular weight fucoidan (MMF, 300-10k) and low-molecular weight fucoidan (LMF, <10k). In this study, the inhibitory effects of HMF and LMF from New Zealand Undaria Pinnatifida have been studied against breast cancer. Two breast cancer cell lines, MCF-7 and MDA-MB-231, have been used in this study representing ER-positive type and triple-negative type of breast cancer. A fibroblast (HDFa) cell line has also been used in this study, representing non-cancer cells, to examine toxicity of fucoidan.
By conducting MTT assays, apoptosis assay and other related mechanism assays on cancer cells, the findings in this study indicate that LMF exhibited much better inhibition on proliferation of breast cancer cells than HMF. Dose-dependent inhibition by LMF was observed in both MCF-7 and MDA-MB-231 after incubated for 48, 72 and 96 hours. MCF-7 cells are more sensitive to LMF than MDA-MB-231 by a distinction of about 20% inhibition at the highest concentration of LMF (56.6% inhibition at 200 µg/ml and 39.2% inhibition at 300µg/ml,72hrs, respectively) and time-dependent manner of inhibition was only observed in MCF-7. The IC50 of LMF to MCF-7 cells over 72 hours was determined to be about 19 µg/ml and dropped to 10.5 µg/ml after 96 hours. Induction of caspase-dependent apoptosis was observed in MDA-MB-231 cells through intrinsic apoptosis pathway alone or with the extrinsic pathway. An activation of NOS stimulated by LMF was observed in MDA-MB-231 cells at a dose-dependent manner. No obvious cytotoxicity of LMF to HDFa cells was observed by 72 hours incubation in a cell cycle assay. To conclude, LMF from New Zealand Undaria Pinnatifida showed great anti-cancer effects against these two types of breast cancer, therefore, it has great potential to be used as a therapeutic agent or a supplement to combine with other chemo-agents for treating breast cancer, even though it may not be potent enough to treat this type of cancer alone
In Vitro Study of the Cytotoxic Effects of Low- and High-Molecular-Weight Fucoidan Extracted from New Zealand Seaweed Undaria pinnatifida in MCF-7 and MDA-MB-231 Breast Cancer Cell Lines
No full textBreast cancer is known as the top cancer for women worldwide. It is estimated that every year over one million new cases of breast cancer are diagnosed and contribute largely to cancer related deaths. Chemotherapy, including neoadjuvant therapy and adjuvant therapy, is a critical part in treatment for breast cancer that impact on survival and life quality for patients. However, chemo-resistance and adverse effects occur frequently when patients receive chemotherapy or the improved target therapies. New strategies have been proposed to enhance the effects of anticancer drugs as combing them with natural dietary compounds, decreasing drug dose administered and reducing the toxicity to normal cells.
Fucoidan is noticed for its anti-cancer potential in treating breast cancer as well as in many other cancers. It is a natural bioactive compound derived from brown algae that has low toxicity and multiple anti-cancer pathways, the potential of which makes it a candidate for therapeutic agent using alone or in combination with other cytotoxic drugs. Base on the molecular weight, fucoidan can be categorised into three ranges: high-molecular weight fucoidan (HMF, >300k), medium-molecular weight fucoidan (MMF, 300-10k) and low-molecular weight fucoidan (LMF, <10k). In this study, the inhibitory effects of HMF and LMF from New Zealand Undaria Pinnatifida have been studied against breast cancer. Two breast cancer cell lines, MCF-7 and MDA-MB-231, have been used in this study representing ER-positive type and triple-negative type of breast cancer. A fibroblast (HDFa) cell line has also been used in this study, representing non-cancer cells, to examine toxicity of fucoidan.
By conducting MTT assays, apoptosis assay and other related mechanism assays on cancer cells, the findings in this study indicate that LMF exhibited much better inhibition on proliferation of breast cancer cells than HMF. Dose-dependent inhibition by LMF was observed in both MCF-7 and MDA-MB-231 after incubated for 48, 72 and 96 hours. MCF-7 cells are more sensitive to LMF than MDA-MB-231 by a distinction of about 20% inhibition at the highest concentration of LMF (56.6% inhibition at 200 µg/ml and 39.2% inhibition at 300µg/ml,72hrs, respectively) and time-dependent manner of inhibition was only observed in MCF-7. The IC50 of LMF to MCF-7 cells over 72 hours was determined to be about 19 µg/ml and dropped to 10.5 µg/ml after 96 hours. Induction of caspase-dependent apoptosis was observed in MDA-MB-231 cells through intrinsic apoptosis pathway alone or with the extrinsic pathway. An activation of NOS stimulated by LMF was observed in MDA-MB-231 cells at a dose-dependent manner. No obvious cytotoxicity of LMF to HDFa cells was observed by 72 hours incubation in a cell cycle assay. To conclude, LMF from New Zealand Undaria Pinnatifida showed great anti-cancer effects against these two types of breast cancer, therefore, it has great potential to be used as a therapeutic agent or a supplement to combine with other chemo-agents for treating breast cancer, even though it may not be potent enough to treat this type of cancer alone
Author response image 1. Author response
No full textAnkyrin adaptors together with their spectrin partners coordinate diverse ion channels and cell adhesion molecules within plasma membrane domains and thereby promote physiological activities including fast signaling in the heart and nervous system. Ankyrins specifically bind to numerous membrane targets through their 24 ankyrin repeats (ANK repeats), although the mechanism for the facile and independent evolution of these interactions has not been resolved. Here we report the structures of ANK repeats in complex with an inhibitory segment from the C-terminal regulatory domain and with a sodium channel Nav1.2 peptide, respectively, showing that the extended, extremely conserved inner groove spanning the entire ANK repeat solenoid contains multiple target binding sites capable of accommodating target proteins with very diverse sequences via combinatorial usage of these sites. These structures establish a framework for understanding the evolution of ankyrins' membrane targets, with implications for other proteins containing extended ANK repeat domains.</p
Ji yu jin chang sheng xue xuan fu de zi yun xing he zi fu dong er wei zhi dong qi
No full textM.Phil.Acoustic radiation force in the near-field of a vibrating source can be utilized to lift and transport objects, which provides a non-contact driving technology in addition to maglev. This research presents a novel self-running planar motion stage utilizing near-field acoustic transportation phenomenon and coupled resonant vibration of the device.Finite element analysis models have been established to find the needed resonant modes and optimize the design of the structure. The first longitudinal and the second bending modes are designed to have an identical frequency to create elliptical vibration of the structure, which can provide vertical levitation force as well as the propulsion force. A dynamic model based on the Reynolds Equation has been established to study the levitation and driving mechanism of the proposed device. The levitation and driving forces are analyzed; and the relationship between the driving force and the input phase difference is investigated to optimize the following position control. A capacitance surface encoder is proposed to provide the levitation height and two dimensional position feedback for the stage. The encoder design is based on the measurement of capacitance change between the driving stage and the metal sensing plates embedded in the ground. The lateral position (in the XY plane) of the circular stage can be uniquely determined based on the capacitance values.A prototype including the stage, encoder, and controller is implemented and characterized to demonstrate the performance of the proposed design. Two motion characteristics of the stage are first tested: one is the influence of the excitation voltage amplitude on the levitation height, and the other is the influence of the amplitude and phase angles of the excitation signals on the velocity and thrust force. In the calibration of the encoder, the calculated coordinates are firstly compensated for the scaling and the misalignment of the encoder axis and the precision stage. And the systematic errors from the nonlinear features are identified and fitted to a third-order polynomial equation in each axis. In the control scheme, the capacitance encoder works as the feedback module, and a LabVIEW program is used for date acquisition and processing. The stage is tested and demonstrated to follow a circular trajectory with a radius of 3.5mm.This work investigates a novel self-floating and self-running two-dimensional actuator using near-field acoustic levitation and coupled resonant vibration of the device. Compared with the conventional designs based on near-field acoustic levitation, the proposed design eliminates any external component such as guide rail, which contributes to bigger working space. This design also has two-dimensional motion capability with higher load capacity and energy efficiency. A dynamic model based on the Reynolds Equation is established to study the driving mechanism. A capacitance surface encoder is proposed to provide the two dimensional position feedback for the stage. A prototype including the stage, encoder, and controller is implemented and characterized to demonstrate the capability of the proposed design.振動源在近場中產生的輻射力可以用於提升和運輸物體，這現象可用於非接觸驅動技術，並有別於磁懸浮技術。本研究提出了一種新型的自運行平面運動機構，該機構利用了近場聲學傳播現象和裝置的耦合諧振。通過有限元分析可以找到機構的共振模態，並且用於指導結構的優化設計。通過結構設計，使得一階縱向模態和二階橫向模態具有相同的振動頻率，以產生橢圓振動，橢圓振動同時提供懸浮立和前進驅動力。建立了基於雷諾方程的運動模型，來分析機構的懸浮和運動機制。通過分析懸浮力和驅動力，獲得驅動力與輸入信號相位差之間的關係，用於之後定位平臺的位置控制。基於表面電容的編碼器被用於定位平臺的位置反饋，這個反饋包括了平臺的懸浮高度以及它的二維平面位置。編碼器可以測量懸浮平臺和固定在地上的金屬感應板間的電容。基於測得的電容值，通過相應的計算，可以得出平臺在XY平面內的確定位置。建立了包括運動器，編碼器和控制器在內的實驗模型，用於驗證設計的性能。首先是關於驅動器運動性能的測定，第一個是電壓大小對懸浮高度的影響，第二個是電壓大小以及電壓相位角對於運動速度和驅動力的影響。在編碼器的校準過程中，首先補償了由於編碼器和精密平臺錯位以及縮放而引起的誤差， 然後運用三階多項式來擬合每個軸的非線性系統誤差。在控制方案中，電容式編碼器起反饋作用，一個LabVIEW程序用於對電信號的處理。在運動測試中，平臺行走了一個半徑為3.5mm的圓形軌跡。這項研究成功研發了一種新型的自懸浮和自運動的二維運動機構，這個機構運用了近場超聲懸浮和耦合共振效應。與傳統的近場超聲懸浮裝置相比，新的設計不需要導軌之類的任何外部部件，這有助於提供更大的工作空間。該設計具有二維運動能力，並有更高的負載能力和能量效率。建立了基於雷諾方程的運動模型來研究其運動機制。用電容編碼器來當作二維定位平臺的位置反饋。包括運動機構，編碼器和控制器在內的實驗模型被建立，用於驗證設計的性能。Chen, Keyu.Thesis M.Phil. Chinese University of Hong Kong 2017.Includes bibliographical references (leaves 56-60).Abstracts also in Chinese.Title from PDF title page (viewed on 06, February, 2020).Chen, Keyu
A Mean Field Game Approach to Relative Investment-Consumption Games with Habit Formation
No full textThis paper studies an optimal investment-consumption problem for competitive
agents with exponential or power utilities and a common finite time horizon.
Each agent regards the average of habit formation and wealth from all peers as
benchmarks to evaluate the performance of her decision. We formulate the
n-agent game problems and the corresponding mean field game problems under the
two utilities. One mean field equilibrium is derived in a closed form in each
problem. In each problem with n agents, an approximate Nash equilibrium is then
constructed using the obtained mean field equilibrium when n is sufficiently
large. The explicit convergence order in each problem can also be obtained. In
addition, we provide some numerical illustrations of our results.Comment: arXiv admin note: substantial text overlap with arXiv:2206.13341 by
other author
Intraseasonal Reversal of Winter Temperature Anomalies in Eastern China in Early 2022 and Its Possible Causes
No full textA remarkable intraseasonal reversal of temperature anomaly is witnessed in eastern China in early 2022, characterized by a warm January and a cold February. ERA5 daily reanalysis data, multiple regression and the Linear Baroclinic Model (LBM) are employed to investigate the characteristics and causes of this abnormal temperature Pattern. The findings indicate that: (1) The two Rossby wave trains along the south and north westerly jets over Eurasia have synergistic impacts on middle and high latitudes. In January, the south branch Rossby wave train exhibited a positive phase, coinciding with a negative phase in the north branch wave train. As a result, the south trough strengthens, while the north trough weakens, leading to anomalous warm advection that warms eastern China. In February, the phases of these two Rossby waves are reversed, causing anomalous cold advection as the southern trough diminishes and the northern trough intensifies, resulting in colder conditions in eastern China. (2) Tropical convection activity weakens in January, whereas it intensifies in February in the northeast Indian Ocean. The weakening of the East Asian trough as a result of the convective latent heat anomalies caused an anticyclonic circulation over the Korean Peninsula in January through the Pacific-Japan teleconnection-like pattern, which is necessary for the maintenance of warm anomalies. Conversely, increased convective activity in February induces cyclonic circulation, deepening the East Asian trough over the Korean Peninsula and contributing to the persistence of cold anomalies. (3) The Rossby wave trains along the two westerly jets and the tropical convective activity in the northeastern Indian Ocean work in tandem, simultaneously strengthening or weakening the East Asian trough. Consequently, the East Asian trough weakens in January and strengthens in February
An Evaluation of Environmental Governance in Urban China Based on a Hesitant Fuzzy Linguistic Analytic Network Process
No full textThe aim of this study is to evaluate the performance of urban environmental governance by developing hesitant fuzzy linguistic analytic network process (HFL-ANP). The study bridges the gaps in current knowledge in the following ways: the study methodically develops the HFL-ANP method to evaluate and pick the optimal environmental governance strategy from alternatives; theoretically, network structure of evaluation indicators system on environmental governance is constructed, and the objective and subjective information in the evaluation process of environmental governance is combined. In detail, based on the environmental Kuznets curve (EKC) and the pollution haven hypothesis, the paper constructs the evaluation indexes system of environmental governance and takes observation time length into consideration. Then, we choose three urban cases of environmental governance by exploring the existing literature. Furthermore, we develop the HFL-ANP method and apply it to the cases. The study calculates the initial weights of all indexes by using multiplicative consistency of the HFL preference relation, and derives the decision matrix through combining objective information with subjective information of environmental governance. Finally, we come to the following conclusions: ANP network stricture is close to real-world practical problems and provides the basis for HFL-ANP method; HFL-ANP is a very suitable method of assessing environmental governance; and based on the urban cases of environmental governance, Shanghai is the optimal alternative. In addition, this indicator system can only be applied to cities in China, and the administrative hierarchy of policies has not been considered by this method. Thus, future studies should expand this method and indicator network to contain different countries and different administrative hierarchy
ROSES: A Novel Semi-supervised Feature Selector
No full textPart 7: Pattern RecognitionInternational audienceIn this study, a novel ROugh set based Semi-supervised fEature Selector (Roses) was developed to pre-process partially labeled data. The main innovations of our Roses are: 1) the selected features over labeled samples laid the foundation for further searching qualified features over unlabeled samples; 2) a new granularity related measure was designed to quickly evaluate features. Through testing four different ratios (20%, 40%, 60%, 80%) of labeled samples, the experimental results over 15 UCI datasets demonstrated that our framework is superior to the other five popular partially labeled data feature selectors: 1) the feature subsets identified by Roses offer competitive classification performances; 2) Roses is good at seeking a balance between efficiency of searching features and effectiveness of the selected features
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