A hybrid PWM strategy for SMES integrated grid-feeding transformerless PV Inverters
- Authors: Mondal, Sudipto , Biswas, Shuvra , Bin Islam, Md Sabbir , Islam, Md Rabiul , Shah, Rakibuzzaman
- Date: 2023
- Type: Text , Conference paper
- Relation: 2023 IEEE International Conference on Applied Superconductivity and Electromagnetic Devices, ASEMD 2023, Tianjin, China, 27-29 October 2023, 2023 IEEE International Conference on Applied Superconductivity and Electromagnetic Devices, ASEMD 2023
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- Description: This paper presents a new hybrid pulse width modulation (PWM) strategy for improving the performance of superconducting magnetic energy storage (SMES) integrated solar photovoltaic (PV) based grid-feeding transformerless H6 inverter systems. The proposed PWM strategy offers significantly lower total harmonic distortion (THD) of output voltage compared to existing unipolar PWM (UPPWM), bipolar PWM (BPPWM), and some well-established advanced PWM techniques. A new carrier and reference signals are used to develop the proposed hybrid PWM strategy, which ensures low leakage current compared to existing counterparts. The presented inverter system is simulated in MATLAB/Simulink and PLECS computer simulation environment. Apart from simulated results, some preliminary experimental test results are also shown to validate the superiority of the proposed PWM strategy. © 2023 IEEE
Geographic constraint mobility model for ad hoc network
- Authors: Ahmed, Sabbir , Karmakar, Gour , Kamruzzaman, Joarder
- Date: 2008
- Type: Text , Conference paper
- Relation: Proceedings of the 2008 IEEE International Symposium on Modeling, Analysis & Simulation of Computer & Telecommunication Systems
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- Description: In this paper, we propose a mobility model and present its simulation tool to generate realistic mobility traces for mobile ad hoc network. The mobility model is capable of creating realistic node movement pattern in the presence of geographic constraints by exploiting the concepts of anchors. The model dynamically places anchors depending upon the context of the environment through which nodes are guided to move towards the destination, and obstacles of arbitrary shapes with or without doorways and any existing pathways, in full or part of the terrain can be incorporated which makes the simulation environment more realistic. The characteristics of the proposed mobility model tested on a real world university campus map at various movement patterns are presented that illustrate the impact of the mobility model on the performance of a routing protocol and usefulness of the proposed scenario generation tool.
Improved switching scheme to reduce the junction temperature and power loss of CHB inverters
- Authors: Afrin, Sadia , Biswas, Suvra , Bin Islam, Md Sabbir , Islam, Md Rabiul , Shah, Rakibuzzaman
- Date: 2023
- Type: Text , Conference paper
- Relation: 2023 IEEE International Conference on Applied Superconductivity and Electromagnetic Devices, ASEMD 2023, Tianjin, China, 27-29 October 2023, 2023 IEEE International Conference on Applied Superconductivity and Electromagnetic Devices, ASEMD 2023
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- Description: Excessive heating and power loss due to high-frequency switching are always alarming issues in the case of multilevel inverter (MLI) based applications such as solar photovoltaic (PV) systems and industrial drives. Both the heating and power loss of power semiconductor switches significantly rely on the switching pulse width modulation (PWM) scheme employed. This paper proposes an improved switching technique for a solar PV-fed grid-tied 5-level cascaded H-bridge (CHB) inverter, which also reduces the power semiconductor losses of the inverter in relation to several existing switching schemes. The proposed switching scheme employs a modified discontinuous standard mode signal to develop the modulating signal of the proposed method. Level-shifted triangular carrier signals are considered with the proposed switching signal to produce the gate pulses for the 5-level CHB inverter. The performance of the proposed switching scheme is validated through MATLAB/Simulink and PLECS computer simulation environments. © 2023 IEEE.
An environment-aware mobility model for wireless ad hoc network
- Authors: Ahmed, Sabbir , Karmakar, Gour , Kamruzzaman, Joarder
- Date: 2010
- Type: Text , Journal article
- Relation: Computer Networks Vol. 54, no. 9 (2010), p. 1470-1489
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- Description: Simulation is a cost effective, fast and flexible alternative to test-beds or practical deployment for evaluating the characteristics and potential of mobile ad hoc networks. Since environmental context and mobility have a great impact on the accuracy and efficacy of performance measurement, it is of paramount importance how closely the mobility of a node resembles its movement pattern in a real-world scenario. The existing mobility models mostly assume either free space for deployment and random node movement or the movement pattern does not emulate real-world situation properly in the presence of obstacles because of their generation of restricted paths. This demands for the development of a node movement pattern with accurately representing any obstacle and existing path in a complex and realistic deployment scenario. In this paper, we propose a general mobility model capable of creating a more realistic node movement pattern by exploiting the concept of flexible positioning of anchors. Since the model places anchors depending upon the context of the environment through which nodes are guided to move towards the destination, it is capable of representing any terrain realistically. Furthermore, obstacles of arbitrary shapes with or without doorways and any existing pathways in full or part of the terrain can be incorporated which makes the simulation environment more realistic. A detailed computational complexity has been analyzed and the characteristics of the proposed mobility model in the presence of obstacles in a university campus map with and without signal attenuation are presented which illustrates its significant impact on performance evaluation of wireless ad hoc networks.
Efficient data gathering in 3D linear underwater wireless sensor networks using sink mobility
- Authors: Akbar, Mariam , Javaid, Nadeem , Khan, Ayesha , Imran, Muhammad , Shoaib, Muhammad , Vasilakos, Athanasios
- Date: 2016
- Type: Text , Journal article
- Relation: Sensors (Switzerland) Vol. 16, no. 3 (2016), p.
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- Description: Due to the unpleasant and unpredictable underwater environment, designing an energy-efficient routing protocol for underwater wireless sensor networks (UWSNs) demands more accuracy and extra computations. In the proposed scheme, we introduce a mobile sink (MS), i.e., an autonomous underwater vehicle (AUV), and also courier nodes (CNs), to minimize the energy consumption of nodes. MS and CNs stop at specific stops for data gathering; later on, CNs forward the received data to the MS for further transmission. By the mobility of CNs and MS, the overall energy consumption of nodes is minimized. We perform simulations to investigate the performance of the proposed scheme and compare it to preexisting techniques. Simulation results are compared in terms of network lifetime, throughput, path loss, transmission loss and packet drop ratio. The results show that the proposed technique performs better in terms of network lifetime, throughput, path loss and scalability. © 2016 by the authors; licensee MDPI, Basel, Switzerland.
Ode to form
- Authors: Mestrom, Sanne
- Date: 2012
- Type: Text , Visual art work
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Soil moisture, organic carbon, and nitrogen content prediction with hyperspectral data using regression models
- Authors: Datta, Dristi , Paul, Manoranjan , Murshed, Manzur , Teng, Shyh Wei , Schmidtke, Leigh
- Date: 2022
- Type: Text , Journal article
- Relation: Sensors (Basel, Switzerland) Vol. 22, no. 20 (2022), p.
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- Description: Soil moisture, soil organic carbon, and nitrogen content prediction are considered significant fields of study as they are directly related to plant health and food production. Direct estimation of these soil properties with traditional methods, for example, the oven-drying technique and chemical analysis, is a time and resource-consuming approach and can predict only smaller areas. With the significant development of remote sensing and hyperspectral (HS) imaging technologies, soil moisture, carbon, and nitrogen can be estimated over vast areas. This paper presents a generalized approach to predicting three different essential soil contents using a comprehensive study of various machine learning (ML) models by considering the dimensional reduction in feature spaces. In this study, we have used three popular benchmark HS datasets captured in Germany and Sweden. The efficacy of different ML algorithms is evaluated to predict soil content, and significant improvement is obtained when a specific range of bands is selected. The performance of ML models is further improved by applying principal component analysis (PCA), a dimensional reduction method that works with an unsupervised learning method. The effect of soil temperature on soil moisture prediction is evaluated in this study, and the results show that when the soil temperature is considered with the HS band, the soil moisture prediction accuracy does not improve. However, the combined effect of band selection and feature transformation using PCA significantly enhances the prediction accuracy for soil moisture, carbon, and nitrogen content. This study represents a comprehensive analysis of a wide range of established ML regression models using data preprocessing, effective band selection, and data dimension reduction and attempt to understand which feature combinations provide the best accuracy. The outcomes of several ML models are verified with validation techniques and the best- and worst-case scenarios in terms of soil content are noted. The proposed approach outperforms existing estimation techniques.
Coalition of Oct4A and β1 integrins in facilitating metastasis in ovarian cancer
- Authors: Samardzija, Chantel , Luwor, Rodney , Quinn, Michael , Kannourakis, George , Findlay, Jock , Ahmed, Nuzhat
- Date: 2016
- Type: Text , Journal article
- Relation: BMC Cancer Vol. 16, no. 1 (2016), p. 1-16
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- Description: Background: Ovarian cancer is a metastatic disease and one of the leading causes of gynaecology malignancy-related deaths in women. Cancer stem cells (CSCs) are key contributors of cancer metastasis and relapse. Integrins are a family of cell surface receptors which allow interactions between cells and their surrounding microenvironment and play a fundamental role in promoting metastasis. This study investigates the molecular mechanism which associates CSCs and integrins in ovarian cancer metastasis. Methods: The expression of Oct4A in high-grade serous ovarian tumors and normal ovaries was determined by immunofluorescence analysis. The functional role of Oct4A was evaluated by generating stable knockdown (KD) of Oct4A clones in an established ovarian cancer cell line HEY using shRNA-mediated silencing. The expression of integrins in cell lines was evaluated by flow cytometry. Spheroid forming ability, adhesion and the activities of matrix metalloproteinases 9/2 (MMP-9/2) was measured by in vitro functional assays and gelatin zymography. These observations were further validated in in vivo mouse models using Balb/c nu/nu mice. Results: We report significantly elevated expression of Oct4A in high-grade serous ovarian tumors compared to normal ovarian tissues. The expression of Oct4A in ovarian cancer cell lines correlated with their CSC-related sphere forming abilities. The suppression of Oct4A in HEY cells resulted in a significant diminution of integrin β1 expression and associated α5 and α2 subunits compared to vector control cells. This was associated with a reduced adhesive ability on collagen and fibronectin and decreased secretion of pro-MMP2 in Oct4A KD cells compared to vector control cells. In vivo, Oct4A knock down (KD) cells produced tumors which were significantly smaller in size and weight compared to tumors derived from vector control cells. Immunohistochemical analyses of Oct4A KD tumor xenografts demonstrated a significant loss of cytokeratin 7 (CK7), Glut-1 as well as CD34 and CD31 compared to vector control cell-derived xenografts. Conclusion: The expression of Oct4A may be crucial to promote and sustain integrin-mediated extracellular matrix (ECM) remodeling requisite for tumor metastasis in ovarian cancer patients. © 2016 The Author(s).
Tumour microenvironment and metabolic plasticity in cancer and cancer stem cells : Perspectives on metabolic and immune regulatory signatures in chemoresistant ovarian cancer stem cells
- Authors: Ahmed, Nuzhat , Escalona, Ruth , Leung, Dilys , Chan, Emily , Kannourakis, George
- Date: 2018
- Type: Text , Journal article , Review
- Relation: Seminars in Cancer Biology Vol. 53, no. (2018), p. 265-281
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- Description: Cancer stem cells (CSCs) are a sub-population of tumour cells, which are responsible to drive tumour growth, metastasis and therapy resistance. It has recently been proposed that enhanced glucose metabolism and immune evasion by tumour cells are linked, and are modulated by the changing tumour microenvironment (TME) that creates a competition for nutrient consumption between tumour and different sub-types of cells attracted to the TME. To facilitate efficient nutrient distribution, oncogene-induced inflammatory milieu in the tumours facilitate adaptive metabolic changes in the surrounding non-malignant cells to secrete metabolites that are used as alternative nutrient sources by the tumours to sustain its increasing energy needs for growth and anabolic functions. This scenario also affects CSCs residing at the primary or metastatic niches. This review summarises recent advances in our understanding of the metabolic phenotypes of cancer cells and CSCs and how these processes are affected by the TME. We also discuss how the evolving TME modulates tumour cells and CSCs in cancer progression. Using previously described proteomic and genomic platforms, ovarian cancer cell lines and a mouse xenograft model we highlight the existence of metabolic and immune regulatory signatures in chemoresistant ovarian CSCs, and discuss how these processes may affect recurrence in ovarian tumours. We propose that progress in cancer control and eradication may depend not only on the elimination of highly chemoresistant CSCs, but also in designing novel strategies which would intervene with the tumour-promoting TME factors.
COVID-19 : factors associated with the psychological distress, fear and resilient coping strategies among community members in Saudi Arabia
- Authors: Alharbi, Talal , Alqurashi, Alaa , Mahmud, Ilias , Alharbi, Rayan , Islam, Sheikh , Almustanyir, Sami , Maklad, Ahmed , AlSarraj, Ahmad , Mughaiss, Lujain , Al-Tawfiq, Jaffar , Ahmed, Ahmed , Barry, Mazin , Ghozy, Sherief , Alabdan, Lulwah , Alif, Sheikh , Sultana, Farhana , Salehin, Masudus , Banik, Biswajit , Cross, Wendy , Rahman, Muhammad Aziz
- Date: 2023
- Type: Text , Journal article
- Relation: Healthcare (Switzerland) Vol. 11, no. 8 (2023), p.
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- Description: (1) Background: COVID-19 caused the worst international public health crisis, accompanied by major global economic downturns and mass-scale job losses, which impacted the psychosocial wellbeing of the worldwide population, including Saudi Arabia. Evidence of the high-risk groups impacted by the pandemic has been non-existent in Saudi Arabia. Therefore, this study examined factors associated with psychosocial distress, fear of COVID-19 and coping strategies among the general population in Saudi Arabia. (2) Methods: A cross-sectional study was conducted in healthcare and community settings in the Saudi Arabia using an anonymous online questionnaire. The Kessler Psychological Distress Scale (K-10), Fear of COVID-19 Scale (FCV-19S) and Brief Resilient Coping Scale (BRCS) were used to assess psychological distress, fear and coping strategies, respectively. Multivariate logistic regressions were used, and an Adjusted Odds Ratio (AOR) with 95% Confidence Intervals (CIs) was reported. (3) Results: Among 803 participants, 70% (n = 556) were females, and the median age was 27 years; 35% (n = 278) were frontline or essential service workers; and 24% (n = 195) reported comorbid conditions including mental health illness. Of the respondents, 175 (21.8%) and 207 (25.8%) reported high and very high psychological distress, respectively. Factors associated with moderate to high levels of psychological distress were: youth, females, non-Saudi nationals, those experiencing a change in employment or a negative financial impact, having comorbidities, and current smoking. A high level of fear was reported by 89 participants (11.1%), and this was associated with being ex-smokers (3.72, 1.14–12.14, 0.029) and changes in employment (3.42, 1.91–6.11, 0.000). A high resilience was reported by 115 participants (14.3%), and 333 participants (41.5%) had medium resilience. Financial impact and contact with known/suspected cases (1.63, 1.12–2.38, 0.011) were associated with low, medium, to high resilient coping. (4) Conclusions: People in Saudi Arabia were at a higher risk of psychosocial distress along with medium-high resilience during the COVID-19 pandemic, warranting urgent attention from healthcare providers and policymakers to provide specific mental health support strategies for their current wellbeing and to avoid a post-pandemic mental health crisis. © 2023 by the authors.
A new fuzzy logic approach for consistent interpretation of dissolved gas-in-oil analysis
- Authors: Abu-Siada, Ahmed , Hmood, Sdood , Islam, Syed
- Date: 2013
- Type: Text , Journal article
- Relation: IEEE Transactions on Dielectrics and Electrical Insulation Vol. 20, no. 6 (2013), p. 2343-2349
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- Description: Dissolved gas analysis (DGA) of transformer oil is one of the most effective power transformer condition monitoring tools. There are many interpretation techniques for DGA results however all these techniques rely on personnel experience more than analytical formulation. As a result, various interpretation techniques do not necessarily lead to the same conclusion for the same oil sample. Furthermore, significant number of DGA results fall outside the proposed codes of the current based-ratio interpretation techniques and cannot be diagnosed by these methods. Moreover, ratio methods fail to diagnose multiple fault conditions due to the mixing up of produced gases. To overcome these limitations, this paper introduces a new fuzzy logic approach to reduce dependency on expert personnel and to aid in standardizing DGA interpretation techniques. The approach relies on incorporating all existing DGA interpretation techniques into one expert model. DGA results of 2000 oil samples that were collected from different transformers of different rating and different life span are used to establish the model. Traditional DGA interpretation techniques are used to analyze the collected DGA results to evaluate the consistency and accuracy of each interpretation technique. Results of this analysis were then used to develop the proposed fuzzy logic model.
TIMP-2 regulates proliferation, invasion and STAT3-mediated cancer stem cell-dependent chemoresistance in ovarian cancer cells
- Authors: Escalona, Ruth , Bilandzic, Maree , Western, Patrick , Kadife, Elif , Kannourakis, George , Findlay, Jock , Ahmed, Nuzhat
- Date: 2020
- Type: Text , Journal article
- Relation: BMC Cancer Vol. 20, no. 1 (2020), p.
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- Description: Background: The metzincin family of metalloproteinases and the tissue inhibitors of metalloproteinases (TIMPs) are essential proteins required for biological processes during cancer progression. This study aimed to determine the role of TIMP-2 in ovarian cancer progression and chemoresistance by reducing TIMP-2 expression in vitro in Fallopian tube secretory epithelial (FT282) and ovarian cancer (JHOS2 and OVCAR4) cell lines. Methods: FT282, JHOS2 and OVCAR4 cells were transiently transfected with either single or pooled TIMP-2 siRNAs. The expression of different genes after TIMP-2 knock down (T2-KD) or in response to chemotherapy was determined at the mRNA level by quantitative real time PCR (qRT-PCR) and at the protein level by immunofluorescence. Sensitivity of the cell lines in response to chemotherapy after TIMP-2 knock down was investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and 5-Ethynyl-2′-deoxyuridine (EdU) assays. Cell invasion in response to TIMP-2 knockdown was determined by xCELLigence. Results: Sixty to 90 % knock down of TIMP-2 expression was confirmed in FT282, OVCAR4 and JHOS2 cell lines at the mRNA and protein levels. TIMP-2 knock down did not change the mRNA expression of TIMP-1 or TIMP-3. However, a significant downregulation of MMP-2 in T2-KD cells occurred at both the protein and activation levels, compared to Control (Cont; scrambled siRNA) and Parental cells (P, transfection reagent only). In contrast, membrane bound MT1-MMP protein levels were significantly upregulated in T2-KD compared to Cont and P cells. T2-KD cells exhibited enhanced proliferation and increased sensitivity to cisplatin and paclitaxel treatments. Enhanced invasion was observed in the T2-KD-JOSH2 and OVCAR4 cells but not in T2-KD-FT282 cells. Treatment with cisplatin or paclitaxel significantly elevated the expression of TIMP-2 in Cont cells but not in T2-KD cells, consistent with significantly elevated expression of chemoresistance and CSC markers and activation of STAT3. Furthermore, a potent inhibitor of STAT3 activation, Momelotinib, suppressed chemotherapy-induced activation of P-STAT3 in OVCAR4 cells with concomitant reductions in the expression of chemoresistance genes and CSC markers. Conclusions: The above results suggest that TIMP-2 may have a novel role in ovarian cancer proliferation, invasion and chemoresistance. © 2020 The Author(s).
Optimizing 3d printed metallic object’s postprocessing : a case of gamma‐tial alloys
- Authors: Chowdhury, M. A. K. , Sharif Ullah, A. , Teti, Roberto
- Date: 2021
- Type: Text , Journal article
- Relation: Materials Vol. 14, no. 5 (2021), p. 1-15
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- Description: Gamma‐TiAl (γ‐TiAl) alloys can be used in high‐end products relevant to the aerospace, defense, biomedical, and marine industries. Fabricating objects made of γ‐TiAl alloys needs an additive manufacturing process called Electron Beam Melting (EBM) or other similar processes because these alloys are difficult‐to‐cut materials. An object fabricated by EBM exhibits poor surface finish and must undergo postprocessing. In this study, cylindrical specimens were fabricated by EBM and post‐processed by turning at different cutting conditions (cutting speed, depth of cut, feed rate, insert radius, and coolant flowrate). The EBM conditions were as follows: average powder size 110 μm, acceleration voltage 60 kV, beam current 10 mA, beam scanning speed 2200 mm/s, and beam focus offset 0.20 mm. The surface roughness and cutting force were recorded for each set of cutting conditions. The values of the cutting conditions were set by the L36 Design of Experiment approach. The effects of the cutting conditions on surface roughness and cutting force are elucidated by constructing the possibility distributions (triangular fuzzy numbers) from the experimental data. Finally, the optimal cutting conditions to improve the surface finish of specimens made of γ‐TiAl alloys are determined using the possibility distributions. Thus, this study’s outcomes can be used to develop intelligent systems for optimizing additive manufacturing processes. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
Knock down of TIMP-2 by siRNA and CRISPR/Cas9 mediates diverse cellular reprogramming of metastasis and chemosensitivity in ovarian cancer
- Authors: Escalona, Ruth , Chu, Simon , Kadife, Elif , Kelly, Jason , Kannourakis, George , Findlay, Jock , Ahmed, Nuzhat
- Date: 2022
- Type: Text , Journal article
- Relation: Cancer Cell International Vol. 22, no. 1 (2022), p.
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- Description: Background: The endogenous tissue inhibitor of metalloproteinase-2 (TIMP-2), through its homeostatic action on certain metalloproteinases, plays a vital role in remodelling extracellular matrix (ECM) to facilitate cancer progression. This study investigated the role of TIMP-2 in an ovarian cancer cell line in which the expression of TIMP-2 was reduced by either siRNA or CRISPR/Cas9. Methods: OVCAR5 cells were transiently and stably transfected with either single or pooled TIMP-2 siRNAs (T2-KD cells) or by CRISPR/Cas9 under the influence of two distinct guide RNAs (gRNA1 and gRNA2 cell lines). The expression of different genes was analysed at the mRNA level by quantitative real time PCR (qRT-PCR) and at the protein level by immunofluorescence (IF) and western blot. Proliferation of cells was investigated by 5-Ethynyl-2′-deoxyuridine (EdU) assay or staining with Ki67. Cell migration/invasion was determined by xCELLigence. Cell growth in vitro was determined by 3D spheroid cultures and in vivo by a mouse xenograft model. Results: Approximately 70–90% knock down of TIMP-2 expression were confirmed in T2-KD, gRNA1 and gRNA2 OVCAR5 ovarian cancer cells at the protein level. T2-KD, gRNA1 and gRNA2 cells exhibited a significant downregulation of MMP-2 expression, but concurrently a significant upregulation in the expression of membrane bound MMP-14 compared to control and parental cells. Enhanced proliferation and invasion were exhibited in all TIMP-2 knocked down cells but differences in sensitivity to paclitaxel (PTX) treatment were observed, with T2-KD cells and gRNA2 cell line being sensitive, while the gRNA1 cell line was resistant to PTX treatment. In addition, significant differences in the growth of gRNA1 and gRNA2 cell lines were observed in in vitro 3D cultures as well as in an in vivo mouse xenograft model. Conclusions: Our results suggest that the inhibition of TIMP-2 by siRNA and CRISPR/Cas-9 modulate the expression of MMP-2 and MMP-14 and reprogram ovarian cancer cells to facilitate proliferation and invasion. Distinct disparities in in vitro chemosensitivity and growth in 3D culture, and differences in tumour burden and invasion to proximal organs in a mouse model imply that selective suppression of TIMP-2 expression by siRNA or CRISPR/Cas-9 alters important aspects of metastasis and chemosensitivity in ovarian cancer. © 2022, The Author(s).
A zero-watermarking algorithm for privacy protection in biomedical signals
- Authors: Ali, Zulfiqar , Imran, Muhammad , Alsulaiman, Mansour , Zia, Tanveer , Shoaib, Muhammad
- Date: 2018
- Type: Text , Journal article
- Relation: Future Generation Computer Systems Vol. 82, no. (2018), p. 290-303
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- Description: Confidentiality of health information is indispensable to protect privacy of an individual. However, recent advances in electronic healthcare systems allow transmission of sensitive information through the Internet, which is prone to various vulnerabilities, attacks and may leads to unauthorized disclosure. Such situations may not only create adverse effects for individuals but may also cause severe consequences such as hefty regulatory fines, bad publicity, legal fees, and forensics. To avoid such predicaments, a privacy protected healthcare system is proposed in this study that protects the identity of an individual as well as detects vocal fold disorders. The privacy of the developed healthcare system is based on the proposed zero-watermarking algorithm, which embeds a watermark in a secret key instead of the signals to avoid the distortion in an audio sample. The identity is protected by the generation of its secret shares through visual cryptography. The generated shares are embedded by finding the patterns into the audio with the application of one-dimensional local binary pattern. The proposed zero-watermarking algorithm is evaluated by using audio samples taken from the Massachusetts Eye and Ear Infirmary voice disorder database. Experimental results demonstrate that the proposed algorithm achieves imperceptibility and is reliable in its extraction of identity. In addition, the proposed algorithm does not affect the results of disorder detection and it is robust against noise attacks of various signal-to-noise ratios. © 2017 Elsevier B.V.
Firm growth by women-owned Small and Medium Enterprises in a developing economy setting
- Authors: Jomaraty, Mosfeka
- Date: 2015
- Type: Text , Thesis , PhD
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- Description: The growth experiences of women-owned Small and Medium Enterprises (SMEs) in the context of a developing economy are examined through the lens of pragmatism. This approach views a businesswoman’s ‘belief’, ‘habit’ and ‘doubt’ as critical for researching gender related issues in entrepreneurship. This study explains the growth aspects of women-owned manufacturing and services SMEs of Bangladesh with the aim of addressing two neglected research issues. One is the scarcity of studies on growth oriented women entrepreneurs in developing countries. The other is the lack of focus on very successful high-growth women-owned firms in the context of a strong male-dominated economy. This study adopts a framework developed out of the Diana International Project to evaluate the factors influencing the growth of these successful, growing, Bangladeshi women-owned businesses. In order to evaluate the growth process itself, this framework was then modified with growth resources and actions as explained by Edith Penrose in her 1959 seminal book The Theory of Growth of the Firm. This allows for the investigation of the effects of managerial and entrepreneurial abilities in growth, and the identification of how firms achieve growth. A multiple-case design is adopted, covering sixteen successful growth-oriented firms in the manufacturing and services sector. SMEs were studied as the basis for firm growth from initial venture creation, while the sector concentration on manufacturing and services reflects the urban nature of the study in examining firms that exist in the capital city of Dhaka. Data from in-depth interviews and supporting documents were used for the case studies and integrated with the theoretical framework. Themes were categorised and patterns compared against the framework. The results of this research suggest that SME growth is a process which is gradual and iterative, comprising a series of growth strategies and approaches. The framework identifies interactive connection between different growth variables and highlights how industry sector and the national context of a growing economy facilitate growth of women-owned SMEs. The case study based research seeks to advance scholarship in relation to women’s entrepreneurship globally and contribute to the understanding of growth oriented women’s entrepreneurship. Building upon existing knowledge, this research endeavours to generate new insights and advance theoretical discourse by providing richness and subtlety to the knowledge of growth process and opening up new avenues for future research.
- Description: Doctor of Philosophy
The attributes of plakins in cancer and disease: perspectives on ovarian cancer progression, chemoresistance and recurrence
- Authors: Wesley, Tamsin , Berzins, Stuart , Kannourakis, George , Ahmed, Nuzhat
- Date: 2021
- Type: Text , Journal article , Review
- Relation: Cell Communication and Signaling Vol. 19, no. 1 (2021), p.
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- Description: The plakin family of cytoskeletal proteins play an important role in cancer progression yet are under-studied in cancer, especially ovarian cancer. These large cytoskeletal proteins have primary roles in the maintenance of cytoskeletal integrity but are also associated with scaffolds of intermediate filaments and hemidesmosomal adhesion complexes mediating signalling pathways that regulate cellular growth, migration, invasion and differentiation as well as stress response. Abnormalities of plakins, and the closely related spectraplakins, result in diseases of the skin, striated muscle and nervous tissue. Their prevalence in epithelial cells suggests that plakins may play a role in epithelial ovarian cancer progression and recurrence. In this review article, we explore the roles of plakins, particularly plectin, periplakin and envoplakin in disease-states and cancers with emphasis on ovarian cancer. We discuss the potential role the plakin family of proteins play in regulating cancer cell growth, survival, migration, invasion and drug resistance. We highlight potential relationships between plakins, epithelial-mesenchymal transition (EMT) and cancer stem cells (CSCs) and discuss how interaction of these processes may affect ovarian cancer progression, chemoresistance and ultimately recurrence. We propose that molecular changes in the expression of plakins leads to the transition of benign ovarian tumours to carcinomas, as well as floating cellular aggregates (commonly known as spheroids) in the ascites microenvironment, which may contribute to the sustenance and progression of the disease. In this review, attempts have been made to understand the crucial changes in plakin expression in relation to progression and recurrence of ovarian cancer. [MediaObject not available: see fulltext.] © 2021, The Author(s).
A novel concept for three-phase cascaded multilevel inverter topologies
- Authors: Hasan, Mubashwar , Abu-Siada, Ahmed , Islam, Syed , Muyeen, S.
- Date: 2018
- Type: Text , Journal article
- Relation: Energies Vol. 11, no. 2 (2018), p. 1-16
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- Description: One of the key challenges in multilevel inverters (MLIs) design is to reduce the number of components used in the implementation while maximising the number of output voltage levels. This paper proposes a new concept that facilitates a device count reduction technique of existing cascaded MLIs. Moreover, the proposed concept can be utilised to extend existing single phase cascaded MLI topologies to three-phase structure without tripling the number of semiconductor components and input dc-supplies as per the current practice. The new generalized concept involves two stages; namely, cascaded stage and phase generator stage. The phase generator stage is a combination of a conventional three-phase two level inverter and three bi-directional switches while the cascaded stage can employ any existing cascaded topology. A laboratory prototype model is built and extensive experimental analyses are conducted to validate the feasibility of the proposed cascaded MLI concept.
A novel generalized concept for three phase cascaded multilevel inverter topologies
- Authors: Hasan,Md Mubashwar , Abu-Siada, Ahmed , Islam, Syed , Muyeen, S
- Date: 2017
- Type: Text , Conference proceedings
- Relation: 9th Annual IEEE Green Technologies Conference (GreenTech 2017); Denver, CO; 29th-21st March, 2017 p. 110-117
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- Description: Many new cascaded multilevel inverter (MLI) topologies have recently been proposed and published in the literature. All proposed topologies demand significant amount of semiconductor components and input dc supplies, which is considered the main drawback for the implementation of three phase cascaded MLIs. This paper proposes a new generalized concept that could be employed within any existing cascaded MLI topology in order to reduce its size in terms of device count including semiconductor switches, diodes, and dc power supplies. The new generalized concept involves two stages namely, cascaded stage (CS) and phase generator stage (PGS). The PGS stage is a combination of conventional three phase two level inverter (CTPTLI) and three bidirectional (BD) switches, while the cascaded stage can be modified using any existing cascaded topology. The proposed concept is validated through extensive simulation and experimental analyses. Results show the capability of the proposed technique in reducing device count of the existing topologies while maintaining its performance.
A fault-tolerant cascaded switched-capacitor multilevel inverter for domestic applications in smart grids
- Authors: Akbari, Ehsan , Teimouri, Ali , Saki, Mojtaba , Rezaei, Mohammad , Hu, Jiefeng , Band, Shahab , Pai, Hao-Ting , Mosavi, Amir
- Date: 2022
- Type: Text , Journal article
- Relation: IEEE Access Vol. 10, no. (2022), p. 110590-110602
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- Description: Cascaded multilevel inverters (MLIs) generate an output voltage using series-connected power modules that employ standard configurations of low-voltage components. Each module may employ one or more switched capacitors to double or quadruple its input voltage. The higher number of switched capacitors and semiconductor switches in MLIs compared to conventional two-level inverters has led to concerns about overall system reliability. A fault-tolerant design can mitigate this reliability issue. If one part of the system fails, the MLI can continue its planned operation at a reduced level rather than the entire system failing, which makes the fault tolerance of the MLI particularly important. In this paper, a novel fault location technique is presented that leads to a significant reduction in fault location detection time based on the reliability priority of the components of the proposed fault-tolerant switched capacitor cascaded MLI (CSCMLI). The main contribution of this paper is to reduce the number of MLI switches under fault conditions while operating at lower levels. The fault-tolerant inverter requires fewer switches at higher reliability, and the comparison with similar MLIs shows a faster dynamic response of fault detection and reduced fault location detection time. The experimental results confirm the effectiveness of the presented methods applied in the CSCMLI. Also, all experimental data including processor code, schematic, PCB, and video of CSCMLI operation are attached. © 2013 IEEE.