Academic literature on the topic 'Most critical factor (MCF)'
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Journal articles on the topic "Most critical factor (MCF)"
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Ma, Le, Zhenyu Liu, and Zhimin Fan. "Potential Mechanisms of miR-143/Krupple Like Factor 5 Axis in Impeding the Proliferation of Michigan Cancer Foundation-7 Breast Cancer Cell Line." Journal of Biomaterials and Tissue Engineering 11, no. 2 (February 1, 2021): 326–32. http://dx.doi.org/10.1166/jbt.2021.2545.
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Breast cancer is one of the most prevailing cancers in females, while the cancerous heterogeneity hinders its early diagnosis and subsequent therapy. miR-143-3p is a critical mediator in malignancy development and tumorigenesis as a tumor suppressor. Its role in various tumor entities has been investigated, such as colon cancer and breast cancer. Using MCF-7 breast cancer cell model, we planned to explore the underlying mechanisms of miR-143/KLF-5 axis in retarding breast cancer cells growth. Bioinformatics analysis searched the target KLF5 of miR-143, and the miR-143-targeted mimic and inhibitor were employed to detect the changes of KLF5. After transfection of mimic miR-143, the CCK-8 reagent assessed cell proliferation. Based on optimal stimulation time, miR-143 stimulation model was established, followed by determining expression of KLF5, EGFR and PCNA via western blot and qPCR. Eventually, siRNA-KLF5 was applied to silencing KLF5 level to evaluate its role in MCF-7 cells. The transcription and translation levels of KLF5 were diminished in miR-143-mimic transfected MCF-7 cells, while enhanced in miR-143-inhibitor transfected MCF-7 cells. When MCF-7 cells were transfected with miR-143-mimic at different time points, 48 hours was found to be the optimal transfection time, with reduced transcription and translation levels of KLF5, EGFR and PCNA. The transcription and translation levels of PNCA and EGFR were declined after silencing KLF5 by siRNA. miR-143/KLF5 axis could retard the proliferation of MCF-7 breast cancer cells.
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Sampath, Deepak, Richard C. Winneker, and Zhiming Zhang. "Cyr61, a Member of the CCN Family, Is Required for MCF-7 Cell Proliferation: Regulation by 17β-Estradiol and Overexpression in Human Breast Cancer." Endocrinology 142, no. 6 (June 1, 2001): 2540–48. http://dx.doi.org/10.1210/endo.142.6.8186.
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Abstract Cyr61, a member of the CCN (CTGF/Cyr61/NOV) family of growth regulators, is a secreted cysteine-rich proangiogenic factor that has been implicated in tumorigenesis. Previous studies have also demonstrated that Cyr61 is regulated by 17β-estradiol (E2) in the uterus. Therefore, we hypothesized that hormonal regulation of Cyr61 may be important in estrogen-dependent pathogenic processes such as breast tumorigenesis. Our study demonstrates that both Cyr61 messenger RNA and protein are induced by E2 in MCF-7 mammary adenocarcinoma cells that primarily overexpress estrogen receptor α (ERα) in a dose-dependent and immediate early fashion. Cyr61 gene induction by E2 is transcriptionally regulated by ERα as the antiestrogen, ICI 182,780, and actinomycin D blocked induction completely. In addition, Cyr61 is up-regulated in MCF-7 cells by epidermal growth factor (EGF) in an immediate early fashion as well. The functional relevance of steroid induction of Cyr61 in breast cancer cell growth is demonstrated by anti-Cyr61 neutralizing antibodies, which diminished E2 and EGF-dependent DNA synthesis and dramatically reduced E2-driven cell proliferation by more than 70%. Most importantly, Cyr61 is overexpressed in 70% (28 of 40) of breast cancer patients with infiltrating ductal carcinoma and is localized exclusively to hyperplastic ductal epithelial cells. Moreover, the levels of Cyr61 protein are higher in breast tumors that are ER+/EGF receptor+ than those that are ER−/EGF receptor+, suggesting that estrogens may mediate Cyr61 expression in vivo. Collectively, our data suggest that Cyr61 may play a critical role in estrogen- as well as growth factor-dependent breast tumor growth.
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Abuarqoub, Abdelrahman. "D-FAP: Dual-Factor Authentication Protocol for Mobile Cloud Connected Devices." Journal of Sensor and Actuator Networks 9, no. 1 (December 20, 2019): 1. http://dx.doi.org/10.3390/jsan9010001.
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Emerging Mobile Cloud Computing (MCC) technologies offer a new world of promise by leveraging the quality of mobile services. With MCC, resource-constrained mobile devices could capitalize on the computation/storage resources of cloud servers via communication networks. While MCC adoption is growing significantly, several challenges need to be addressed to make MCC-based solutions scale and meet the ever-growing demand for more resource intensive applications. Security is a critical problem hindering the adoption of MCC. One of the most important aspects of MCC security is to establish authenticated communication sessions between mobile devices and cloud servers. The huge amount of data stored on mobile devices poses information security risks and privacy concerns for individuals, enterprises, and governments. The ability to establish authenticated communication sessions between mobile devices and cloud servers can resolve many security concerns. Limited computing and energy resources on mobile devices makes authentication and encryption a challenging task. In this paper, an overview of MCC authentication protocols is presented. Then, a Dual-Factor Authentication Protocol for MCC devices (D-FAP) is proposed. D-FAP aims at increasing authentication security by using multi-factors while offloading computation to the cloud to reduce battery consumption. The security of the protocol is formally verified and informal analysis is performed for various attacks. The results prove that the D-FAP is successful in mitigating various outsider and insider attacks.
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Vrana, K. E., M. E. Churchill, T. D. Tullius, and D. D. Brown. "Mapping functional regions of transcription factor TFIIIA." Molecular and Cellular Biology 8, no. 4 (April 1988): 1684–96. http://dx.doi.org/10.1128/mcb.8.4.1684.
Full textAbstract:
Functional deletion mutants of the trans-acting factor TFIIIA, truncated at both ends of the molecule, have been expressed by in vitro transcription of a cDNA clone and subsequent cell-free translation of the synthetic mRNAs. A region of TFIIIA 19 amino acids or less, near the carboxyl terminus, is critical for maximal transcription and lies outside the DNA-binding domain. The elongated protein can be aligned over the internal control region (ICR) of the Xenopus 5S RNA gene with its carboxyl terminus oriented toward the 5' end of the gene and its amino terminus oriented toward the 3' end of the gene. The nine "zinc fingers" and the linkers that separate them comprise 80% of the protein mass and correspond to the DNA-binding domain of TFIIIA. The zinc fingers near the amino terminus of the protein contribute more to the overall binding energy of the protein to the ICR than do the zinc fingers near the carboxyl end. The most striking feature of TFIIIA is its modular structure. This is demonstrated by the fact that each zinc finger binds to just one of three short nucleotide sequences within the ICR.
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Ni, Zhuoyu, Abbie Saunders, Nicholas J. Fuda, Jie Yao, Jose-Ramon Suarez, Watt W. Webb, and John T. Lis. "P-TEFb Is Critical for the Maturation of RNA Polymerase II into Productive Elongation In Vivo." Molecular and Cellular Biology 28, no. 3 (December 10, 2007): 1161–70. http://dx.doi.org/10.1128/mcb.01859-07.
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ABSTRACT Positive transcription elongation factor b (P-TEFb) is the major metazoan RNA polymerase II (Pol II) carboxyl-terminal domain (CTD) Ser2 kinase, and its activity is believed to promote productive elongation and coupled RNA processing. Here, we demonstrate that P-TEFb is critical for the transition of Pol II into a mature transcription elongation complex in vivo. Within 3 min following P-TEFb inhibition, most polymerases were restricted to within 150 bp of the transcription initiation site of the active Drosophila melanogaster Hsp70 gene, and live-cell imaging demonstrated that these polymerases were stably associated. Polymerases already productively elongating at the time of P-TEFb inhibition, however, proceeded with elongation in the absence of active P-TEFb and cleared from the Hsp70 gene. Strikingly, all transcription factors tested (P-TEFb, Spt5, Spt6, and TFIIS) and RNA-processing factor CstF50 exited the body of the gene with kinetics indistinguishable from that of Pol II. An analysis of the phosphorylation state of Pol II upon the inhibition of P-TEFb also revealed no detectable CTD Ser2 phosphatase activity upstream of the Hsp70 polyadenylation site. In the continued presence of P-TEFb inhibitor, Pol II levels across the gene eventually recovered.
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Elhady, Sameh S., Reda F. A. Abdelhameed, Salwa H. Zekry, Amany K. Ibrahim, Eman S. Habib, Khaled M. Darwish, Reem M. Hazem, Khadijah A. Mohammad, Hashim A. Hassanean, and Safwat A. Ahmed. "VEGFR-Mediated Cytotoxic Activity of Pulicaria undulata Isolated Metabolites: A Biological Evaluation and In Silico Study." Life 11, no. 8 (July 28, 2021): 759. http://dx.doi.org/10.3390/life11080759.
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Natural products play a remarkable role not only in the synthesis, design, and discovery of new drugs but also as the most prominent source of drugs and bioactive substances. Adding to the search for new sources of safe innovative antitumor drugs, here we reported a phytochemical study on Pulicaria undulata which revealed promising antiangiogenic agents. Six compounds were isolated and identified as xanthoxyline (1), stigmasterol (2), oleanolic acid (3), salvigenin (4), rhamnetin (5) and dihydroquercetin-4′-methyl ether (6) using nuclear magnetic resonance (NMR) spectroscopic techniques. Compound 3 and 4 are first reported in Pulicaria genus. Both the extract and isolated compounds were evaluated for in vitro antiproliferative activity against breast cancer cell line (MCF-7). In vivo antiproliferative activity against Ehrlich’s ascites carcinoma (EAC) were also assessed. The P. undulata extract and isolates showed significant reduction in tumor weight, decreased both serum vascular endothelial growth factor B (VEGF-B) levels and vascular endothelial growth factor receptor 2 (VEGFR-2) expression significantly compared to the control EAC group, suggesting an antiangiogenic activity through the inhibition of VEGF signaling. Besides, they displayed reduction in CD34 expression, confirming their antiangiogenic effect. Moreover, the potential affinity of isolated compounds to human estrogen nuclear receptor-alpha (hER-α), the most recognized modulator of VEGFR-2 expression, was virtually estimated through molecular modeling studies. The most promising activity profiles were assigned to the investigated flavonoids, compounds 4–6, as well as the alkyl-phenylketone, compound 1. Additionally, these four top active compounds showed respective high to intermediate docking scores while possessing preferential binding with hER-α critical pocket residues. Based on the provided data, these isolated compounds illustrated promising inhibitors of VEGF-stimulated angiogenesis, which could be a possible mechanism for their anticancer activity.
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Mohammad-Qureshi, Sarah S., Raphaël Haddad, Elizabeth J. Hemingway, Jonathan P. Richardson, and Graham D. Pavitt. "Critical Contacts between the Eukaryotic Initiation Factor 2B (eIF2B) Catalytic Domain and both eIF2β and -2γ Mediate Guanine Nucleotide Exchange." Molecular and Cellular Biology 27, no. 14 (May 25, 2007): 5225–34. http://dx.doi.org/10.1128/mcb.00495-07.
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ABSTRACT Diverse guanine nucleotide exchange factors (GEFs) regulate the activity of GTP binding proteins. One of the most complicated pairs is eukaryotic initiation factor 2B (eIF2B) and eIF2, which function during protein synthesis initiation in eukaryotes. We have mutated conserved surface residues within the eIF2B GEF domain, located at the eIF2Bε C terminus. Extensive genetic and biochemical characterization established how these residues contribute to GEF activity. We find that the universally conserved residue E569 is critical for activity and that even a conservative E569D substitution is lethal in vivo. Several mutations within residues close to E569 have no discernible effect on growth or GCN4 expression, but an alanine substitution at the adjacent L568 is cold sensitive and deregulates GCN4 activity at 15°C. The mutation of W699, found on a separate surface approximately 40 Å from E569, is also lethal. Binding studies show that W699 is critical for interaction with eIF2β, while L568 and E569 are not. In contrast, all three residues are critical for interaction with eIF2γ. These data show that multiple contacts between eIF2γ and eIF2Bε mediate nucleotide exchange.
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Lei, Lei, Delin Ren, and Zachary F. Burton. "The RAP74 Subunit of Human Transcription Factor IIF Has Similar Roles in Initiation and Elongation." Molecular and Cellular Biology 19, no. 12 (December 1, 1999): 8372–82. http://dx.doi.org/10.1128/mcb.19.12.8372.
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ABSTRACT Transcription factor IIF (TFIIF) is a protein allosteric effector for RNA polymerase II during the initiation and elongation phases of the transcription cycle. In initiation, TFIIF induces promoter DNA to wrap almost a full turn around RNA polymerase II in a complex that includes the general transcription factors TATA-binding protein, TFIIB, and TFIIE. During elongation, TFIIF also supports a more active conformation of RNA polymerase II. This conformational model for elongation is supported by three lines of experimental evidence. First, a region within the RNA polymerase II-associating protein 74 (RAP74) subunit of TFIIF (amino acids T154 to M177), a region that is critical for isomerization of the preinitiation complex, is also critical for elongation stimulation. Amino acid substitutions within this region are shown to have very similar effects on initiation and elongation, and mutagenic analysis indicates that L155, W164, N172, I176, and M177 are the most important residues in this region for transcription. Second, TFIIF is shown to have a higher affinity for rapidly elongating RNA polymerase II than for the stalled elongation complex, indicating that RNA polymerase II alternates between active and inactive states during elongation and that TFIIF stimulates elongation by supporting the active conformational state of RNA polymerase II. The deleterious I176A substitution in the critical region of RAP74 decreases the affinity of TFIIF for the active form of the elongation complex. Third, TFIIF is shown by Arrhenius analysis to stimulate elongation by populating an activated state of RNA polymerase II.
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DEUTSCH, CLAUDE, and NAEEM A. TAHIR. "Fusion reactions and matter–antimatter annihilation for space propulsion." Laser and Particle Beams 24, no. 4 (October 2006): 605–16. http://dx.doi.org/10.1017/s0263034606060691.
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Magnetic confinement fusion (MCF) and inertial confinement fusion (ICF) are critically contrasted in the context of far-distant travels throughout solar system. Both are shown to potentially display superior capabilities for vessel maneuvering at high speed, which are unmatched by standard cryogenic propulsion (SCP). Costs constraints seem less demanding than for ground-based power plants. Main issue is the highly problematic takeoff from earth, in view of safety hazards concomitant to radioactive spills in case of emergency. So, it is recommended to assemble the given powered vessel at high earth altitude ∼ 700 km, above upper atmosphere. Fusion propulsion is also compared to fission powered one, which secures a factor of two improvement over SCP. As far a specific impulse (s) is considered, one expects 500–3000 from fission and as much as 104–105 from fusion through deuterium–tritium (D-T). Next, we turn attention to the most performing fusion reaction, i.e., proton–antiproton annihilation with specific impulse ∼ 103–106 and thrust–to–weight ratio ∼ 10−3–1. Production and costs are timely reviewed. The latter could drop by four orders of magnitude, which is possible with successful MCF or ICF. Appropriate vessel designs will be presented for fusion as well as for antimatter propulsion. In particular, ion compressed antimatter nuclear II (ICAN-II) project to Mars in 30 days with fusion catalyzed by 140 ng of antiprotons will be detailed (specific impulse ∼ 13500 s).
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Vrana, K. E., M. E. Churchill, T. D. Tullius, and D. D. Brown. "Mapping functional regions of transcription factor TFIIIA." Molecular and Cellular Biology 8, no. 4 (April 1988): 1684–96. http://dx.doi.org/10.1128/mcb.8.4.1684-1696.1988.
Full textAbstract:
Functional deletion mutants of the trans-acting factor TFIIIA, truncated at both ends of the molecule, have been expressed by in vitro transcription of a cDNA clone and subsequent cell-free translation of the synthetic mRNAs. A region of TFIIIA 19 amino acids or less, near the carboxyl terminus, is critical for maximal transcription and lies outside the DNA-binding domain. The elongated protein can be aligned over the internal control region (ICR) of the Xenopus 5S RNA gene with its carboxyl terminus oriented toward the 5' end of the gene and its amino terminus oriented toward the 3' end of the gene. The nine "zinc fingers" and the linkers that separate them comprise 80% of the protein mass and correspond to the DNA-binding domain of TFIIIA. The zinc fingers near the amino terminus of the protein contribute more to the overall binding energy of the protein to the ICR than do the zinc fingers near the carboxyl end. The most striking feature of TFIIIA is its modular structure. This is demonstrated by the fact that each zinc finger binds to just one of three short nucleotide sequences within the ICR.
Dissertations / Theses on the topic "Most critical factor (MCF)"
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Xu, Hongjiang. "Critical success factors for accounting information systems data quality." University of Southern Queensland, Faculty of Business, 2003. http://eprints.usq.edu.au/archive/00001526/.
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Quality information is critical to organisations’ success in today’s highly competitive environment. Accounting information systems (AIS) as a discipline within information systems require high quality data. However, empirical evidence suggests that data quality is problematic in AIS. Therefore, knowledge of critical factors that are important in ensuring data quality in accounting information systems is desirable. A literature review evaluates previous research work in quality management, data quality, and accounting information systems. It was found that there was a gap in the literature about critical success factors for data quality in accounting information systems. Based on this gap in the literature and the findings of the exploratory stage of the research, a preliminary research model for factors influence data quality in AIS was developed. A framework for understanding relationships between stakeholder groups and data quality in accounting information systems was also developed. The major stakeholders are information producers, information custodians, information managers, information users, and internal auditors. Case study and survey methodology were adopted for this research. Case studies in seven Australian organisations were carried out, where four of them were large organisations and the other three are small to medium organisations (SMEs). Each case was examined as a whole to obtain an understanding of the opinions and perspectives of the respondents from each individual organisation as to what are considered to be the important factors in the case. Then, cross-case analysis was used to analyze the similarities and differences of the seven cases, which also include the variations between large organisations and small to medium organisations (SMEs). Furthermore, the variations between five different stakeholder groups were also examined. The results of the seven main case studies suggested 26 factors that may have impact on data quality in AIS. Survey instrument was developed based on the findings from case studies. Two large-scale surveys were sent to selected members of Australian CPA, and Australian Computer Society to further develop and test the research framework. The major findings from the survey are: 1. respondents rated the importance of the factors consistent higher than the actual performance of those factors. 2. There was only one factor, ‘audit and reviews’, that was found to be different between different sized organisations. 3. Four factors were found to be significantly different between different stakeholder groups: user focus, measurement and reporting, data supplier quality management and audit and reviews. 4. The top three critical factors for ensuring data quality in AIS were: top management commitment, education and training, and the nature of the accounting information systems. The key contribution of this thesis is the theoretical framework developed from the analysis of the findings of this research, which is the first such framework built upon empirical study that explored factors influencing data quality in AIS and their interrelationships with stakeholder groups and data quality outcomes. That is, it is now clear which factors impact on data quality in AIS, and which of those factors are critical success factors for ensuring high quality information outcomes. In addition, the performance level of factors was also incorporated into the research framework. Since the actual performance of factors has not been highlighted in other studies, this research adds new theoretical insights to the extant literature. In turn, this research confirms some of the factors mentioned in the literature and adds a few new factors. Moreover, stakeholder groups of data quality in AIS are important considerations and need more attention. The research framework of this research shows the relationship between stakeholder groups, important factors and data quality outcomes by highlighting stakeholder groups’ influence on identifying the important factors, as well as the evaluation of the importance and p erformance of the factors.
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Thinh, Le Dang, and Le Dang Thinh. "Refining the Most Critical Factor of E-Commerce in Vietnam." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/61756435638880150158.
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碩士國立臺中教育大學
國際經營管理碩士學位學程(IMBA)
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This research examines the factor that effect the customer’s decision on selecting e-commerce websites through the lens of theory of planned behavior written by Icek Ajzen. Each small element can be essential for an e-commerce website to be success in certain markets. Researcher has adapted the factor analysis method to conduct a comprehensive investigation for refining the critical factors that effect on the customer decisions on selecting e-commerce websites to have their transaction, this research restricts the market of Vietnam by focusing the primary research motivation such as refining the most critical factors affecting consumers to select an online shopping website in Vietnam, from the outcomes to help e-commerce businesses to develop their marketing strategies effectively in Vietnam and give the suggestions for Vietnam empirical companies or developers to give a further boost for e-commerce sector. In order to unsatisfactorily the purpose of this research, a quantitative research was applied to the research project. The results of the research could be consulted by the e-commerce companies to become a foundation for establishing their business.
Books on the topic "Most critical factor (MCF)"
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Cohen, Richard I., ed. Jonatan Meir, Kabbalistic Circles in Jerusalem (1896–1948), trans. Avi Aronsky. Leiden: Brill, 2016. 269 pp. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190912628.003.0030.
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This chapter reviews the book Kabbalistic Circles in Jerusalem (1896–1948) (2016), by Jonatan Meir, translated by Avi Aronsky. In Kabbalistic Circles in Jerusalem, Meir focuses on the proliferation of Sharabian yeshivot and shows that it represented a critical move toward exotericism within what was previously one of the most esoteric branches of modern Kabbalah. He highlights the institutional, economic, and cultural factors underlying this phenomenon—the last pertaining to the competing claims of ethnic groups such as the Baghdadis, Bukharins, and immigrants from Aleppo (Halabis). Meir explores these changes in the context of the literary and political life of pre-state Jerusalem to demonstrate how the Sharabian seminaries became a potent factor in the life of the city.
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Chakera, Aron, William G. Herrington, and Christopher A. O’Callaghan. Oliguria and anuria. Edited by Patrick Davey and David Sprigings. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199568741.003.0056.
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Oliguria can be caused by any factor that affects renal function, or the free passage of urine down the urinary tract. Complete anuria most commonly occurs in men as a consequence of bladder outlet obstruction from an enlarged prostate. It can also arise in patients who have a single functioning kidney which then becomes obstructed or loses its vascular supply. Oliguria occurs commonly in hospitalized patients, is usually secondary to impaired renal perfusion, and is often predictable. The elderly and more unwell patients, for example, those in critical care settings, are most at risk. The presence of oliguria tends to reflect the severity of the underlying disease processes. The commonest cause of complete anuria is bladder outflow obstruction from an enlarged prostate. This may be precipitated by prostatitis or constipation in a patient with benign prostatic hypertrophy. In catheterized patients, a blocked catheter must be excluded.
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Rasmussen, Amy Cabrera. The Discursive Context of Reproductive Ethics. Edited by Leslie Francis. Oxford University Press, 2016. http://dx.doi.org/10.1093/oxfordhb/9780199981878.013.2.
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Examining how issues are framed in policy discourse illuminates the structure of ethical arguments and the social and political context within which these arguments are made. In the United States, reproductive discourse and policymaking display four contours. First, deemed a legitimate topic for government intervention, reproduction policy has most often been gendered and group-specific. Second, the issue category into which reproduction is placed is a critical factor in policy intervention: Is reproduction a matter of health, gender equality, or religious liberty? Third, in reproductive policymaking, abortion has taken on the role of master subissue, shaping approaches to reproductive issues and in some cases standing in for the larger range of reproductive matters. Finally, lack of understanding of the medical and technological factors related to reproduction among policymakers and the public makes policymaking difficult and augments abortion’s discursive power.
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Postuma, Ronald B. REM sleep behavior disorder. Edited by Sudhansu Chokroverty, Luigi Ferini-Strambi, and Christopher Kennard. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780199682003.003.0038.
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A diagnosis of REM sleep behavior disorder (RBD), a disorder characterized by “acting out” of dreams during REM sleep, has critical implications for a patient’s future. Aside from being a treatable parasomnia, usually managed with melatonin or clonazepam, RBD is the most powerful risk factor for Parkinson disease and dementia with Lewy bodies yet discovered. Over 70% of patients with idiopathic RBD will develop a neurodegenerative synucleinopathy. Moreover, the disease course is more severe in patients with RBD than those without. Numerous screens have been developed to aid detection, and clinical history can help distinguish RBD from NREM parasomnia. However, final diagnosis relies on polysomnographic documentation of REM atonia loss. Given the profound implications of idiopathic RBD, patients need careful counseling and the offer of neurological follow-up to detect and treat prodromal disease symptoms. Recognition of RBD is also a means to discover and test protective therapies against neurodegenerative disease.
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Sprague, Stuart M., and Menaka Sarav. Chronic kidney disease-mineral and bone disorder. Edited by David J. Goldsmith. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199592548.003.0115_update_001.
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The kidneys play a critical role in maintaining normal serum calcium and phosphorus concentrations, under the regulation of three main hormones: parathyroid hormone, calcitriol, and fibroblast growth factor 23. With the progression of chronic kidney disease (CKD), most patients develop CKD–mineral and bone disorder (CKD-MBD), which is a systemic disorder involving derangement in mineral metabolism, renal osteodystrophy, and extraskeletal calcification. Disturbances in mineral metabolism develop early in CKD and include phosphate retention, hypocalcaemia, vitamin D deficiency, and hyperparathyroidism. Renal osteodystrophy involves pathologic changes of bone morphology related to progressive CKD and is quantifiable by histomorphometry, based on bone biopsy. CKD-MBD is associated with significant morbidity, including bone loss, fractures, cardiovascular disease, immune suppression, as well as increased mortality. As the disorder begins early in the course of CKD, a proactive approach with intervention is important. Therapeutic strategies could then be employed to prevent and correct these disturbances, aiming to improve cardiovascular outcomes and survival. Current practice guidelines for CKD-MBD are based on insufficient data and high-quality studies are required before specific treatment can be advocated strongly.
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Karaman, Sinem, Aleksanteri Aspelund, Michael Detmar, and Kari Alitalo. The lymphatic system. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780198755777.003.0009.
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The lymphatic vascular system is an integral component of the circulatory system; it forms a one-way conduit that transports tissue interstitial components back to the venous circulation through lymph nodes. Lymphatic vessels extend to most tissues and contribute to the regulation of interstitial fluid homeostasis, trafficking of immune cells, and absorption of dietary fats from the gut. Developmentally, lymphatic vessels originate from embryonic veins and specialized angioblasts. A number of molecules have been identified in the commitment of endothelial cells to the lymphatic lineage, and the sprouting, expansion and maturation of the lymphatic vascular tree. Importantly, the vascular endothelial growth factor (VEGF) family members VEGFC and VEGFD, together with their receptors VEGFR2 and VEGFR3 have been implicated as critical regulators of lymphangiogenesis. Lymphatic vessels are involved in several human diseases, including cancer, where they contribute to tumour metastasis, the leading cause of cancer-related deaths. Lymphatic vessels regulate immune responses against foreign pathogens by transporting leucocytes to lymph nodes, but are also in involved in the regulation of self-tolerance. Defects in the lymphatic vascular system are causal for the development of lymphoedema.
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Colpan, Asli M., and Takashi Hikino, eds. Business Groups in the West. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198717973.001.0001.
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This volume aims to explore the long-term evolution of different varieties of large enterprises in today’s developed economies. It focuses on the economic institution of business groups and attempts to comprehend the factors behind their rise, growth, struggle, and resilience; their behavioral and organizational characteristics; and their roles in national economic development. The volume seeks to enhance the scholarly and policy-oriented understanding of business groups in developed economies by bringing together state-of-the-art research on the characteristics and contributions of large enterprises in an evolutionary perspective. While business groups are a dominant and critical organization model in contemporary emerging economies and have lately attracted much attention in academic circles and business presses, their counterparts in developed economies have not been systematically examined. This book aims to fill this gap in the literature and is the first scholarly attempt to explore the evolutional paths and contemporary roles of business groups in developed economies from an internationally comparative perspective. In doing so, it argues that business groups actually rose to function as a critical factor of industrial dynamics in the context of the Second Industrial Revolution in the late nineteenth century. They have adapted their characteristic roles and transformed to fit to the changing market and institutional settings. As they flexibly co-evolve with the environment, the volume shows that business groups can remain as a viable organization model in the world’s most advanced economies today.
Book chapters on the topic "Most critical factor (MCF)"
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Roden, Dylan F., Jennifer M. Johnson, Petr Szturz, Paolo Bossi, and Athanassios Argiris. "New and Promising Targeted Therapies in First and Second-Line Settings." In Critical Issues in Head and Neck Oncology, 277–96. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-63234-2_18.
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AbstractDeeper understanding of the molecular pathogenesis of malignancies, including head and neck squamous cell carcinoma (HNSCC), has led to the investigation of several novel targeted therapies. These therapeutic approaches may eventually replace or complement existing treatment modalities, such as surgery, radiation therapy, and traditional cytotoxic chemotherapy. Epidermal growth factor receptor (EGFR) inhibitors, and specifically cetuximab, are as of now the only class of targeted agents, excluding immune checkpoint inhibitors, with approval in the treatment of HNSCC. Beyond EGFR inhibition, novel therapies under evaluation are directed against vascular endothelial growth factor (VEGF) and VEGF receptor (VEGFR), PI3K/AKT/mTOR pathway, cell cycle regulation (for example, cyclin dependent kinases 4 and 6), HRAS, DNA repair mechanisms, and others. Development of new therapies has to take into consideration the complexity of solid tumors and their heterogeneity. Multitargeted combination therapy approaches may be required in certain cases in order to maximize antitumor effect. Ways to individualize treatment using validated biomarkers are likely to improve outcomes. We review the most relevant molecular targets in HNSCC and provide updates on clinical trial data with promising new targeted agents.
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De Pauw, Ines, Carolien Boeckx, and An Wouters. "Mechanisms of Cetuximab Resistance and How to Overcome It." In Critical Issues in Head and Neck Oncology, 21–51. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-63234-2_3.
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AbstractDeregulated or increased signalling of the epidermal growth factor receptor (EGFR) plays an integral role in the development of various cancer types, including head and neck squamous cell carcinoma (HNSCC), making it a compelling drug target. However, after initially promising results of EGFR-targeted therapies, such as the monoclonal antibody cetuximab, it became clear that both intrinsic and acquired therapeutic resistance are major roadblocks in the field of personalised cancer treatments.In order to unravel and overcome resistance to cetuximab, at least two strategies can be adopted.Firstly, therapeutic resistance to anti-EGFR therapy may arise from mechanisms that can compensate for reduced EGFR signalling and/or mechanisms that can modulate EGFR-dependent signalling. In this chapter, we discuss which mechanisms of cetuximab resistance are already known and which ones deserve further investigation. This enhanced knowledge will guide us to rationally design and test novel combination therapies that overcome resistance to EGFR-targeting agents in cancer treatment.Secondly, an urgent need remains to develop novel targeted treatments for single-agent or combined therapy use. In this view, due to the particular mode of activation of the EGFR receptor, involving ligand-induced homo- and heterodimerization of the four HER receptors, an increased inhibition scope of HER receptors most likely results in a more potent blockade of the HER network, preventing premature emergence of resistance and leading to a more pronounced therapeutic benefit. We discuss two multitargeted compounds, being MEHD7945A (duligotuzumab) and afatinib, in this chapter.Despite the huge efforts to unravel the molecular landscape of HNSCC, the main clinically validated target remains EGFR. However, immune checkpoints, like programmed cell death protein 1 (PD-1), are gaining clinical approvals as well. We underscore the importance of adopting rational drug combinations to enhance the therapeutic effect of the EGFR-inhibitor cetuximab and highlight the ongoing search for predictive biomarkers, with the ultimate goal of delivering individualized cancer therapy to HNSCC patients.
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Garrett, Steven L. "The Simple Harmonic Oscillator." In Understanding Acoustics, 59–131. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44787-8_2.
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Abstract This chapter will introduce a system that is fundamental to our understanding of more physical phenomena than any other. Although the “simple” harmonic oscillator seems to be only the combination of the most mundane components, the formalism developed to explain the behavior of a mass, spring, and damper is used to describe systems that range in size from atoms to oceans. Our investigation goes beyond the “traditional” treatments found in the elementary physics textbooks. For example, the introduction of damping will open a two-way street: a damping element (i.e., a mechanical resistance, Rm) will dissipate the oscillator’s energy, reducing the amplitudes of successive oscillations, but it will also connect the oscillator to the surrounding environment that will return thermal energy to the oscillator. The excitation of a harmonic oscillator by an externally applied force, displacement, or combination of the two will result in a response that is critically dependent upon the relationship between the frequency of excitation and the natural frequency of the oscillator and will introduce the critical concepts of mechanical impedance, resonance, and quality factor. Finally, the harmonic oscillator model will be extended to coupled oscillators that are represented by combinations of several masses and several springs.
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Dwivedi, A., and T. Butcher. "RFID as the Critical Factor for Superior Healthcare Delivery." In Encyclopedia of Healthcare Information Systems, 1191–98. IGI Global, 2008. http://dx.doi.org/10.4018/978-1-59904-889-5.ch149.
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Innovations in information and communication technologies (ICTs) have transformed the manner in which healthcare organizations function. Applications of concepts such as data warehousing and data mining have exponentially increased the amount of information that a healthcare organization has access to. Work flow and associated Internet technologies are being seen as instruments to cut administrative expenses. Specifically designed ICT implementations, such as work flow tools, are being used to automate the electronic paper flow in a managed care operation, thereby cutting administrative expenses (Dwivedi, Bali, & Naguib, 2005, p. 44; Latamore, 1999). These recent innovations in the use of ICT applications in a healthcare context have altered the manner in which healthcare institutions exploit clinical and nonclinical data. The pendulum has shifted from the early 1980s, wherein the emphasis of ICT solutions for healthcare was on storage of data in an electronic medium, the prime objective of which was to allow exploitation of this data at a later point in time. As such, most of the early 1980s ICT applications in healthcare were built to provide support for retrospective information retrieval needs and, in some cases, to analyze the decisions undertaken. Clinical data that was traditionally used in a supportive capacity for historical purposes has today become an opportunity that allows healthcare stakeholders to tackle problems before they arise (Dwivedi et al., 2005).
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Dwivedi, A., and T. Butcher. "RFID as the Critical Factor for Superior Healthcare Delivery." In Ubiquitous and Pervasive Computing, 823–32. IGI Global, 2010. http://dx.doi.org/10.4018/978-1-60566-960-1.ch050.
Full textAbstract:
Innovations in information and communication technologies (ICTs) have transformed the manner in which healthcare organizations function. Applications of concepts such as data warehousing and data mining have exponentially increased the amount of information that a healthcare organization has access to. Work flow and associated Internet technologies are being seen as instruments to cut administrative expenses. Specifically designed ICT implementations, such as work flow tools, are being used to automate the electronic paper flow in a managed care operation, thereby cutting administrative expenses (Dwivedi, Bali, & Naguib, 2005, p. 44; Latamore, 1999). These recent innovations in the use of ICT applications in a healthcare context have altered the manner in which healthcare institutions exploit clinical and nonclinical data. The pendulum has shifted from the early 1980s, wherein the emphasis of ICT solutions for healthcare was on storage of data in an electronic medium, the prime objective of which was to allow exploitation of this data at a later point in time. As such, most of the early 1980s ICT applications in healthcare were built to provide support for retrospective information retrieval needs and, in some cases, to analyze the decisions undertaken. Clinical data that was traditionally used in a supportive capacity for historical purposes has today become an opportunity that allows healthcare stakeholders to tackle problems before they arise (Dwivedi et al., 2005).
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da Anunciação, Pedro Fernandes, Vitor Dinis, and Francisco Madeira Esteves. "Preventive Maintenance as a Critical Success Factor in Industry 4.0." In Digital Transformation and Challenges to Data Security and Privacy, 311–31. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-4201-9.ch018.
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In an economy that tends to operate in real time, where companies reduce stocks and value the customization of products and services according to the needs of their customers, information systems and technologies assume a predominant role. Equipment maintenance proves to be critical in supplying markets and meeting consumer needs. Regarding the maintenance of equipment, most managers are faced with the technical indications of suppliers, serving as a reference for the respective interventions. However, these indications often do not contemplate the contingency of certain situations, excessive hours of operation, or temperatures higher than those indicated. Preventive maintenance assumes an important role in the maintenance area by allowing interventions that are more appropriate to the wear and tear of the equipment. The technological potential associated with the internet of things or analytics allows the generation of economic value by guaranteeing the adequate conditions of the equipment and by avoiding disruptions in supply to the markets.
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Prineas, Stavros. "Safety-critical communication." In Handbook of Communication in Anaesthesia & Critical Care. Oxford University Press, 2010. http://dx.doi.org/10.1093/oso/9780199577286.003.0025.
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In Chapter 1 we highlighted an example of failed handover in a tragic case report. This example underscores the difficulty that doctors, as a craft group, often have when we try to talk about communication problems. When trying to explain why an adverse event has occurred, we frequently invoke ‘poor communication’ as a contributing factor. Deeper discussion, however, often proves to be a woollier beast, and we often retreat to the comforting realm of the technical, where the landscape is reassuringly familiar and the outlines are, for us, more clearly defined. Unfortunately the mammoth in the room cannot be ignored; under systematic scrutiny, ‘communication failure’ consistently represents one of the lead contributors to serious adverse events. Most recently, analysis of AIMS report data in an Australian area health service revealed that communication problems were the largest single contributing factor to severe and/or life-threatening clinical incidents over a 2-year period (2007–2009). Perhaps if we develop a better vocabulary of the types of communication errors that occur commonly in the workplace, we can be more articulate about them and develop more focused strategies to overcome them. Communication can be defined as the transfer of meaning from one person to another. For the purposes of developing practical communication tools, communication can be broken down into a package of signals sent from one person—the transmitter— to another—the receiver. These signals are both verbal and non-verbal. It is essential to realize that as social beings we are all constantly ‘transmitting’ signals—not just in the content of our words, but the types of words we use, the tone of our voice, our facial expressions, our body language, our physical proximity to others, the way we dress, the material possessions we display, etc. At any one time most of us are only partly conscious of the total package of what we are ‘saying’ to others. At the same time we are constantly receiving signals and, to a greater or lesser extent, trying to read meaning into and ‘make sense’ of these perceptions. Again often we are only partly conscious of the meaning of the ‘vibes’ we receive; yet they can have a profound impact on what we hear from others.
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Kukreja, Naveen. "Gastroenterology." In Anesthesiology Critical Care Board Review, 43–59. Oxford University Press, 2019. http://dx.doi.org/10.1093/med/9780190908041.003.0004.
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Gastrointestinal and hepatic disease is seen as a complicating factor for some of the most acute and chronically ill patients in the intensive care domain. These patients are not only academically challenging but also clinically challenging and commonly fall into the practice of general surgery as well as hepatology. This chapter reviews the laboratory and clinical presentations of these patients, along with discussion pertaining to common sources of morbidity. Furthermore, scoring systems and acuity markers for these patients are reviewed, along with practical management approaches. Disturbances in the gastrointestinal system are a hallmark of the perioperative patient and should be expected on the examination and in practice.
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Karlaftis, Matthew G. "Critical Review and Analysis of Air-Travel Demand." In Computational Models, Software Engineering, and Advanced Technologies in Air Transportation, 71–87. IGI Global, 2010. http://dx.doi.org/10.4018/978-1-60566-800-0.ch005.
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Demand forecasting may be the most critical factor in the development of airports and airline networks. This chapter reviews various approaches used to forecast air travel and airport demand forecasting. It classifies existing methods according to the modeling approach used to evaluate the available data; then, the forecasting approaches are viewed in relation to data requirements. Finally, a new matrix classification scheme is introduced that combines both the data available and the technique used to evaluate this data in a more concise and manner.
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Hill, Denzil R., and James A. Onigkeit. "Hypertensive Emergencies." In Mayo Clinic Critical and Neurocritical Care Board Review, edited by Eelco F. M. Wijdicks, James Y. Findlay, William D. Freeman, and Ayan Sen, 207–10. Oxford University Press, 2019. http://dx.doi.org/10.1093/med/9780190862923.003.0030.
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Hypertension is a global problem. According to the World Heart Federation, nearly 1 billion people worldwide have hypertension, and nearly two-thirds of them live in developing countries. By the year 2025, hypertension may affect more than 1.5 billion people. Uncontrolled hypertension is 1 of the main causes of premature death worldwide and the most common risk factor for heart disease, stroke, and renal diseases.
Conference papers on the topic "Most critical factor (MCF)"
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Florescu, Gheorghe, and Mihail Cojan. "Identification of CSSC Caused by Ageing and Degradation." In 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/icone14-89286.
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PSA studies, that were developed for some NPPs, permit the using of the created models to perform many research tests, in order to optimize the structures, systems and components (SSCs) operation or to identify the NPP or systems weaknesses, due to specific or special factors. SSCs that influence decisively the NPP reliability are considered as critical. Also, for the accident conditions, the SSC, which have a major influence to the system availability or operability, are considered as critical. Many worldwide NPPs reached the life time or are very close to do that. Several SSCs have shorter life times than NPP’s life time. Ageing is one of the factors that decrease the SSC life time. Due to ageing, if are not replaced, some SSCs, or groups of redundant SSCs, become critical looking to safety. Some questions for what to do in the situation when a SSC must be replaced and the SSC specific manufacturer doesn’t exist, could also be put. The paper tried to solve the problem of SSC modeling by introducing of an ageing factor in SSC model. Fault tree (F/T) modeling approach is assumed. There are two possibilities for modeling: failure rates that are changed or specific MCS (minimal cut set) term modified by ageing. Risk analysis and PSA techniques are used as a basis for analysis. The paper includes: the steps to establish the systems or components that suffer ageing; methods to identify CSSC taking into account ageing; the events associated to ageing/degradation and presentation of method to determine the ageing related events, selection of the SSCs that are important for analyses; selection of the most significant ageing events; ranking of ageing events; association of events to these components in order to decide for the CSSC detailed analyses; ranking / ordering of the ageing related events; optimization of NPP systems design and operation considering ageing; impact of ageing to NPP operation/safety/safety margins and to manufacturer technical specifications. The paper presents a brief description of the most important aspects of the methods, used to analyze the ageing effects on appearing of CSSCs, taking into account the previous developed NPP PSA models and PSA modeling tools.
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Slagis, Gerry C. "Piping Seismic Stress Limits: A Critical Review." In ASME 2002 Pressure Vessels and Piping Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/pvp2002-1422.
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Seismic stress limits for nuclear piping were published by the Section III code in 1994. Because of concerns on the technical bases for the rules, NRC has not approved their use. Modifications to the rules have been made in 2001. The 1994 seismic stress limits are reduced, and one type of joint now has a seismic stress limit that is less that the static load limit. A limit for seismic that is less than the limit for a static load contradicts the test data. Most of the technical concerns were valid. The 1994 rules are based on the premise that collapse is not a potential failure mode for a seismic event. However, collapse occurred in two of the EPRI component tests. Seismic margins in the component tests were overestimated. Revisions to the seismic margin data do not support the higher stress limits. A different approach has been taken to justify the 2001 rules. A probability approach is used where seismic capacity is related to a strength factor. The strength factor is based on the measured ultimate moment in the component tests. The capacity is the strength factor multiplied by a nonlinear dynamic factor. A small nonlinear dynamic factor is used because of concerns with off-resonance margin in stiff components. In contrast, the tests demonstrate large nonlinear dynamic factors. The intent of the new rules is to limit piping response to the SSE to the linear elastic range.
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Alkhalidi, Ammar A. T., and Ryo S. Amano. "Factor Affecting Bubble Creation and Bubble Size." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-62117.
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This paper presents the factors affecting air bubble size when air is injected through a perforated membrane into a water pool. Critical factors that govern the size of air bubbles are the air pressure and the flow rate as well as the hole size of the diffuser membrane. In order to have a better understanding of how bubble size can be affected and what the most effecting conditions are, the study was conducted in a computational fluid dynamic (CFD) investigation, which was validated by the experimental results.
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Roos, E., K. H. Herter, and F. Otremba. "Detailed Assessment of Fatigue Life: A Critical Review." In ASME 2002 Pressure Vessels and Piping Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/pvp2002-1329.
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For the construction, design and operation of technical components and systems the appropriate technical codes and standards provide detailed stress analysis procedures, material data and a design philosophy which guarantees a reliable behaviour of the structural components throughout the specified lifetime. Especially for cyclic stress evaluation the different codes and standards provide different fatigue analyses procedures to be performed considering the various (specified or measured) loading histories (of mechanical and thermal origin) and geometric complexities of the components. In order to fully understand the background of the fatigue analysis included in the codes and standards as well as of the fatigue design curves used as a limiting criteria (to determine the fatigue life usage factor), it is important to understand the history and the methodologies which are available for the design engineers. In the paper the different fatigue analysis procedures in the technical codes and standards (e.g. ASME-III, KAT 3201.2, prEN 13445-18) are discussed in detail. The most important parameters influencing the fatigue analysis, like plastification factor Ke, the correction factors with respect to mean stress, to surface finish, to tempeature, to the environment and to unwelded and welded components are verified on the basis of experimental results. Thus safety margins relevant for the assessment of fatigue life are shown and compared with the safety factors implemented in the different technical codes and standards.
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Ameli, Alireza, Ali Afzalifar, Teemu Turunen-Saaresti, and Jari Backman. "Centrifugal Compressor Design for Near-Critical Point Applications." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75067.
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The supercritical CO2 (sCO2) Brayton cycle has been attracting much attention to produce the electricity power, chiefly due to its higher thermal efficiency with the relatively lower temperature at the turbine inlet compared to other common energy conversion cycles. Centrifugal compressor operating conditions in the supercritical Brayton cycle are commonly set in vicinity of the critical point, owing to smaller compressibility factor and eventually lower compressor work. This paper investigates and compares different centrifugal compressor design methodologies in close proximity to the critical point and suggests the most accurate design procedure based on the findings. An in-house mean-line design code, which is based on the individual enthalpy loss models, is compared to stage efficiency correlation design methods. Moreover, modifications are introduced to the skin friction loss calculation to establish an accurate 1-D design methodology. Moreover, compressor performances are compared to the experimental measurements.
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Hemmes, Kas. "Fuel Cell Dogmas Revisited." In ASME 2004 2nd International Conference on Fuel Cell Science, Engineering and Technology. ASMEDC, 2004. http://dx.doi.org/10.1115/fuelcell2004-2453.
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In spite of the fact that the development of fuel cells is a scientific and technological process, the process, itself seems to be largely determined by the human factor. By a number of examples it will be shown that this development and the creative process necessary for its progress is sometimes hindered by strong beliefs and frequently repeated statements that within themselves hold some truth but do not represent the whole truth. They can be regarded as ‘fuel cell dogmas’. Often implicit assumptions or particular boundary conditions lie behind the dogma. These assumptions or conditions may be altered in the course of the developments or for specific applications. Sometimes the dogma is essentially a rumor that is conveniently accepted by newcomers in the field. An example of the latter is the ban on the use of LiNa carbonate electrolyte in a MCFC instead of LiK because of its supposed higher corrosiveness. Nowadays LiNa is accepted as the new standard electrolyte in a MCFC. The most famous dogma is that fuel cells are more efficient than heat engines because they are not limited by the Carnot efficiency. Yet it is not always true, not even in the reversible limit. For a long time polymer fuel cells were considered to be inherently too expensive because of the membrane and the Pt catalyst. They were considered only suitable for niche markets such as space applications. As we know now General Motors believes differently. Other dogmas are: - Fuel cells have a higher efficiency than heat engines. - A fuel cell converts Hydrogen into power and heat. - Nernst loss is always proportional to utilization and inevitable. - To be economically feasible the fuel gas utilization should be as high as possible. - To be economically feasible the fuel cell should be operated at the highest possible power density. - A fuel cell always has two inlets and two outlets. - In order to use solid fuels in a fuel cell they must be gasified first. - Only low temperature fuel cells are suitable for automotive applications. These and other dogmas will be critically analyzed in terms of the underlying assumptions and boundary conditions. New options that are revealed by breaking through the dogmas are briefly sketched.
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Mueller, Jochen, Shi En Kim, Kristina Shea, and Chiara Daraio. "Tensile Properties of Inkjet 3D Printed Parts: Critical Process Parameters and Their Efficient Analysis." In ASME 2015 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/detc2015-48024.
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To design and optimize for capabilities of additive manufacturing processes it is also necessary to understand and model their variations in geometric and mechanical properties. In this paper, such variations of inkjet 3D printed parts are systematically investigated by analyzing parameters of the whole process, i.e. storage of the material, printing, testing, and storage of finished parts. The goal is to both understand the process and determine the parameters that lead to the best mechanical properties and the most accurate geometric properties. Using models based on this understanding, we can design and optimize parts, and fabricate and test them successfully, thus closing the loop. Since AM materials change rapidly and this process will have to be repeated, it is shown how to create a cost and time efficient experimental design with the one-factor-at-a-time and design of experiments methods, yielding high statistical accuracies for both main and interaction effects. The results show that the number of intersections between layers and nozzles along the load-direction has the strongest impact on the mechanical properties followed by the UV exposure time, which is investigated by part spacing, the position on the printing table and the expiry date of the material. Minor effects are found for the storage time and the surface roughness is not affected by any factor. Nozzle blockage, which leads to a smaller flow-rate of printing material, significantly affected the width and waviness of the printed product. Furthermore, the machine’s warm-up time is found to be an important factor.
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Urra, Susan, and Jessica Green. "Human Factor Modelling in the Pipeline Industry." In 2012 9th International Pipeline Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/ipc2012-90303.
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Most pipeline leaks and ruptures can be attributed to some degree to human factors. Therefore, identifying, measuring and improving areas of potential human factor issues can greatly decrease the risk of pipeline failure. ‘Human factors’ refers to the study of various aspects of human characteristics and job experience, job and task design, tools and equipment design, and work environment which can affect pipeline operations and overall system performance. Enbridge Pipelines has developed a risk assessment model that assesses the risk of human factors along the company’s nationwide liquid pipeline system. The Human Factors Risk Assessment Model generates a risk score for each aspect of the pipeline as well as an overall risk score which highlights the business areas of highest concern. The implementation of the model included the execution of a pilot study to calibrate the model. To perform the pilot, data was collected from the control center, field and office locations through different methodologies such as survey, interview and databases available. The results from the control room operation surveys indicate that the main areas of human error potential in the control room can be mitigated by decreasing the number of manual calculations the operators have to complete and ensuring operators aren’t taking on extra work that should be completed by other areas. These workload improvements would decrease the chance of an operator having to complete two or more control operations at the same time. Lastly, controlling the amount of phone activities that interfere with monitoring and control operations also gives an opportunity to reduce the potential for human error in the control room. Improvements that can be made in the office to reduce human error potential include the development of a human factors standard and improving the critical procedure observation and management of change systems. Measuring, acknowledging and mitigating human factor risks at Enbridge will yield a decrease in the risk of pipeline failure across the entire liquid pipeline system.
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Pryputniewicz, Ryszard J., Dariusz R. Pryputniewicz, and Emily J. Pryputniewicz. "Effect of Process Parameters on TED-Based Q-Factor of MEMS." In ASME 2007 InterPACK Conference collocated with the ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ipack2007-33094.
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Continued advances in microelectromechanical systems (MEMS) technology have led to development of numerous applications including, but not limited to: automotive, communication, information technology, deep-space, medical, safety, national security, etc. These developments are being made possible because of creative designs and novel packaging based on use of some of the most sophisticated analytical and experimental tools available today. These tools are also employed to overcome limitations due to inherent behavior of materials fabricated into miniature shapes subjected to extremely harsh operating conditions while satisfying very challenging specifications/requirements of their applications. Thermoelastic internal friction is present in all structural materials and has been found experimentally in miniature silicon resonators (e.g., microgyroscopes, accelerometers, as well as biological, chemical, and other sensors/actuators) that rely on vibrations of either sensing elements or application-specific elastic suspensions that resonate. Regardless of their applications, sensors are always designed to provide the most sensitive responses to the signals they are developed to detect and/or monitor. One way to describe this sensitivity is to use the Quality (Q) factor. Most recent experimental evidence indicates that as the physical sizes of sensors decrease (especially because of continued advances in fabrication, e.g., by surface micromachining) the corresponding Q-factors become more and more dependent on thermoelastic damping (TED). This form of damping depends on material properties such as coefficient of thermal expansion, thermal conductivity, specific heat, density, and modulus of elasticity. It is also related to such design/operating parameters as resonator dimensions and temperature. This paper reviews a theoretical analysis of the effects that thermoelastic internal friction has on the Q-factor of microscale resonators and shows that the internal friction relating to TED is a fundamental damping mechanism in determination of quality of high-Q resonators over a range of operating conditions. Furthermore, the analysis also shows that the Q of resonators can be critical to the development of modern sensors. Microscale resonators are often used as basic sensing elements in the modern micromachined sensors. These sensors are frequency-modulated devices and exhibit a change in output frequency that is related to measurements and/or control of a physical variable. Accuracy and precision of these measurements/controls are inherently dependent on the frequency stability of the sensor/device output. This, in turn, greatly depends on damping in the resonating element itself.
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Khalifeh, Mahmoud, Babak Akbari, Ahsan Khan, and Daniel C. Braga. "A Critical Review of Rules and Regulations for Permanently Plugged and Abandoned Wells." In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-95330.
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Abstract Permanent Plug and Abandonment (P&A) of wells has been an inevitable part of hydrocarbon exploration and production; however, the methodology has not evolved with the same pace as the rest of the industry. Nonetheless, after the environmental impact of some recent events including the Deepwater Horizon oil spill, permanent P&A of hydrocarbon wells has been receiving more attention. Accordingly, regulatory authorities who oversee the P&A activities and operators have tried to improve the pre-existing P&A methodology by defining a modern P&A philosophy, zero leakage criterion. Although the legislated criterion, adapted by most authorities, has challenged the industry and it had a constructive impact on P&A operations, due to technology deficiencies, the associated cost of operation has significantly increased. In this work, most of the publicly available regulations and their recommended practices addressing P&A have been reviewed and discussed. The focus has been given to zero leakage acceptance policy, conventional versus risk-based approach, barrier verification, human factor in P&A, and technology deficiencies. Although Norway is not a major hydrocarbon producer based on the daily production rate, but because of its stricter requirement on P&A, its recommended practice (NORSOK D-010) for P&A has been used in different oil producing countries. As P&A and its impact on environment is a transnational subject, it is suggested to formulate an international guideline or standard on P&A, given the fact that every well is unique when considering P&A operation.