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Title: The City in the Landscape: Alfred Caldwell's Broader Perspective on Urban Design
Creator: Jones, Kristin, Garcia-Requejo, Zaida
Date: 2020, 2020
Publisher: Editorial Universitat Politècnica de València
Description: Alfred Caldwell was among the first full- time American professors Mies van der Rohe hired at the Illinois Institute of Technology (IIT). Many...
Show moreAlfred Caldwell was among the first full- time American professors Mies van der Rohe hired at the Illinois Institute of Technology (IIT). Many have admired Mies’s architecture since the 1920s, and know that his ideas were also transmitted as a professor, first at the Bauhaus in Europe and then as Director of the Department of Architecture at IIT. Caldwell, a practicing landscape architect and protégé of Jens Jensen, is perhaps less widely known, but was a major influence on IIT’s program especially in the areas of construction, landscape, and architectural history. Caldwell completed a Master of Science in City Planning with a thesis entitled The City in the Landscape: A Preface for Planning, which can be considered a manifesto of both his professional ideas and IIT’s planning pedagogy. In addition to his own works, Caldwell collaborated with Mies and architect Ludwig Hilberseimer, Director of City and Regional Planning at IIT and former Head of Building Theory at the Bauhaus, on the design of built works which left behind artifacts representing the ideal of “the city in the landscape.” This communication examines the broader perspective on urban design influenced by the symbiotic disciplines of architecture, city-regional planning and landscape as manifested in the individual and collaborative built work and pedagogy of Caldwell, Hilberseimer, and Mies.
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Collection: EAAE-ARCC International Conference & 2nd Valencia International Biennial

Title: From positivism to conventionalism: Comte, Renouvier, and Poincaré
Creator: Schmaus, Warren
Date: 2019, 2019
Publisher: Elsevier

Title: INFORMATION QUALITY: RESTRUCTURING THE MODERN ACADEMIC LIBRARY FOR RESEARCH ACCURACY
Creator: JURKOWSKI, ODIN L.
Date: 1997-05
Description: Information overload causes problems in accessing information and is becoming more prevalent as technology allows us to store greater amounts...
Show moreInformation overload causes problems in accessing information and is becoming more prevalent as technology allows us to store greater amounts of information, and as researchers produce ever more specialized knowledge. This thesis will begin with a discussion of this overload followed by an examination of statistics gathered at Illinois Institute of Technology (which support the trend of increased interlibrary loan transactions and the rise in information availability). Following a review of the literature in library and information science, psychology, and linguistics, this thesis will discuss some of the solutions to this problem. First, access may be improved by transforming the storage of information from traditional print resources to electronic. Considering the restrictions of the present vendor supplied print resources, the limitations due to present copyright law, and cost comparisons between print and electronic subscriptions, we find a distinct advantage to future electronic access. This access can be improved through the use of electronic journals, full-text/image databases, and virtual libraries. Second, the searching capabilities of information systems can be improved in order to narrow information into more accurate search results. This can be done by advanced indexing, adding value, relevance and ranking, citation analysis to direct the patron towards improved search results, and by taking advantage of hypertext capabilities in order to ease navigation through information systems.
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Title: SELECTING AN EFFECTIVE DELIVERY METHOD FOR MULTIMEDIA-BASED DISTANCE EDUCATION
Creator: BURIAN, ARNOLD
Date: 1998-05

Title: TESTING COMPUTER INTERACTION TECHNOLOGY AND METHODS WITH CHILDREN
Creator: FROEHLICH, THORSTEN
Date: 2007-07
Description: Deploying educational computer games for children in schools requires understanding of usability. Usability of computer hardware as well as...
Show moreDeploying educational computer games for children in schools requires understanding of usability. Usability of computer hardware as well as the game user interaction is a major concern of this research. The aim of this thesis is to compare the usability of mice and touchpads, as well as test graphics tablets, with third and fifth grade students. Each of these technologies' usability is measured using drag and drop, point and click, and click-only interaction by measuring time to complete tasks and error rate. For this purpose, 142 students participated in a quantitative usability test conducted in five Chicago-area elementary schools. Students played a custom-designed computer game asking them to solve mathematical problems appropriate for their level of education. The main purpose of the game was to create a realistic workload for users. The game tracked students' interactions by recording on-screen cursor movements. Statistical analysis of variance (a = 0.01) of usability showed no significant difference using point and click compared to drag and drop. There was no significant difference between using mice and touchpads. However, because students had no prior experience using graphics tablets, tablet use could not be learned within ten minutes. Finally, usability was found to increase with students' age. Further, when the movements were analyzed for patterns, statistical analysis revealed that workload had a significant influence on usability. Two patterns emerged: hovering with the cursor to find answers on screen, and evading screen areas where accidental dropping of an item could result in an incorrect answer. Although students employing these patterns require more time than reported in previous research, workload had never been considered as a significant factor before. In conclusion, schools can deploy either desktop computers commonly using mice or notebook computers commonly using touchpads because usability does not differ significantly. Workload is the important factor on usability, and thus when developing and usability testing specific games, the users' workload has to be observed. In addition, game designers should consider supporting both drag and drop and point and click. Finally, when testing games, children should be exactly the age of the target audience for accurate results.
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Title: THE FRONT VOWELS BEFORE R OF THE NORTH-CENTRAL STATES
Creator: HARTMANN, ERIKA
Date: 1981-05

Title: INCORPORATING DATABASE EDUCATION INTO THE GRADUATE TECHNICAL COMMUNICATION CURRICULUM
Creator: GEHRS, GORDON SCOTT
Date: 2008-05
Description: The purpose of this study was to identify if there existed a need for database education in technical communication programs. This was...
Show moreThe purpose of this study was to identify if there existed a need for database education in technical communication programs. This was achieved using a two part approach: Jobs data was collected from three major search engines and the results plotted showing a roughly 20% requirement for techcomm positions to have some database knowledge and skill. Then the data was further striated by which techcomm positions were expected to have which skills. The jobs data was also supported by the database skills taught in computer science education, and that of information technology. Next, twelve graduate programs were analyzed for their database educational requirements to show that the need for database skills was not being met in techcomm graduate programs. Finally course content was proposed for five new database courses: OS and Networking Basics, Introduction to Databases, Database Design, and Using Databases. A single course outline is proposed for programs wishing to implement the material more easily.
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Title: EVALUATION OF IMPLEMENTING SGML AT ENDEAVOR INFORMATION SYSTEMS
Creator: STENGLEIN, KRISTEN R.
Date: 1996-04
Description: With large amounts of information for multiple outputs being stored on computers, companies need an effective method of creating, storing, and...
Show moreWith large amounts of information for multiple outputs being stored on computers, companies need an effective method of creating, storing, and re-using information. This proposal investigates whether the Standard Generalized Markup Language (SGML) is the best method to achieve these goals for a small company.
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Title: EVALUATION IF COMPLETENESS, COMPREHENSION AND CREDIBILITY ON AN E-HEALTH WEB SITE
Creator: MASTARONE, GINNIFER L.
Date: 2007-05

Title: THE EFFECT OF MOOD INDUCTION ON ADOLESCENT SPEECH BEHAVIOR
Creator: LAWRENCE, HALCYON
Date: 2010-12
Description: An experiment was conducted to determine if a sad mood induction procedure using music and self-imagery would produce sad speech in...
Show moreAn experiment was conducted to determine if a sad mood induction procedure using music and self-imagery would produce sad speech in adolescents. The participants were asked to rate their perceived positive and negative affect and they were recorded. reading speech materials. Results indicate that although participants perceived a change in mood from neutral to sad, none of the baseline acoustic correlates of sad speech were identified in their recordings. These results suggest that either participants were not induced into a sad mood by this procedure or that the method of self-reporting is an inadequate assessment for this age group, signaling that more effective ways to measure mood for adolescents should be investigated. Additionally, since most studies on sad speech use actors, the results may indicate that acted speech provides significantly different correlates from emotionally-induced speech. Finally, a similarly valenced mood may have been induced instead of sadness (e.g. "calmness") which possesses different acoustic correlates from sad speech. Whilst the findings suggest that there is need for further research on these issues, this experiment demonstrates that mood inducement procedures (MIPs), primarily used in the field of psychology, can be applied in other domains. For example, MIPs conducted in online environments could provide useful insights into how mood affects users' online behaviors.
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Title: UTILIZATION OF CONCEPTS OF INSTRUCTIONAL DESIGN, INFORMATION ARCHITECTURE AND USABILITY TO CREATE A CORPORATE EMPLOYEE TRAINING PROGRAM
Creator: DIGIACOMO, PHILIP A.
Date: 2007-05
Description: Purpose: The Bally Problem...
Show morePurpose: The Bally Problem In 2003, Bally Total Fitness began the process of an international restructuring. The purpose of this restructuring initiative was to address the continuing decay of process efficiency, profitability and company image through a bottom up approach with the staff of the 400+ Bally Total Fitness clubs. The key for this approach was to place the primary focus on two departments; Operations and Employee Training & Development. This documentation and accompanying materials have been compiled as a means with which to outline and catalogue the employee training component of this restructure as well as the process in which the project was carried out. One of the primary reasons Employee Training & Development was considered key in this restructure was due to the need for a single department to facilitate the cultural change throughout the company, which was considered essential to the turnaround effort. The company realized that the only way to properly facilitate this change was to assure that adult learning professionals worked at all levels of the company to educate the staff and steer the needed transition. It was determined that Employee Training & Development must be restructured in a way that allowed for a higher quality of effectiveness in the field, regional offices and the corporate headquarters. The company, as a whole, was looking to implement a more balanced approach to training that would create a well rounded club level employee rather than staff with limited niche roles. Additionally, the company mandated that the corporate team for Employee Training & Development would simultaneously help to educate the executive team while field training managers facilitated the initiative in the clubs and regional offices. For this reason, the corporation decided to restructure the department with the primary goal of recreating a training department from the ground up that would utilize modern philosophies, concepts and technology for adult learning in order to strengthen the ability, productiveness and quality of employee training. To address the employee training component of the restructuring initiative, a team of training professionals were assembled with an initial purpose statement: To assess, evaluate and develop the Bally Total Fitness employee training program utilizing contemporary theories and approaches to adult learning. This team was directed to create and execute upon an approved turnaround strategy with the goal of improved employee development as the dominant focus. Accomplishment of this goal would only be considered to be achieved through development of a training program that addressed and resolved any issues found within the original employee training curriculum that could be shown to adversely affect the average employee's ability with responsibilities, on-the-job attitude and customer service. Preparation for this restructuring required the newly created team to conduct in depth analyses of each department within the corporation to determine the level of importance they played within the overall structure of daily business and how employee training impacted the quality and productivity of their functions. Once these departmental analyses were completed, the team would be expected to create, present and execute a project plan to begin the process of resolving the employee training issues plaguing the corporation.
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Title: DEVELOPING INFORMATION PRODUCTS USING QUALITY MANAGEMENT
Creator: BATSON, LAURA SHEEHAN
Date: 2010-12
Description: In regards to information design, research provides high-level suggestions on how to learn and interact with customers to obtain their desired...
Show moreIn regards to information design, research provides high-level suggestions on how to learn and interact with customers to obtain their desired requirements; but specifics on an approach to eliciting and controlling measurable requirements throughout the development process are not explored. In other areas of design, such an approach already exists: Quality Management, which has successfully improved processes and provided measurements for improvement in order to decrease errors and increase productivity. This dissertation analyzes the applicability of quality management tools to the process of developing information products. The methodology involved two phases. In the initial phase, the researcher had the task of improving a company's benefits enrollment package for two groups. A Traditional Group used the currently accepted best practices in technical communication, performing a heuristic evaluation and a usability test to determine what changes to make in the existing package. This group focuses on the existing benefits enrollment package. In contrast, a Quality Management Group developed a benefits enrollment package using quality management tools, gathering quantifiable functional requirements early in the design and continuing throughout the process. The researcher prepared a revised benefits enrollment package for both groups, and the results of the studies were compared. According to the usability analysis, the Traditional Group showed considerable improvement from the original package to the redesigned package. However, the Quality Management Group showed even greater improvements in several areas, suggesting the potential viability of this method in information design. Future studies should focus on testing the effectiveness of this process on other types of information products. For the products that are successful, information designers could greatly benefit in learning how to use quality management tools to provide more precise and measurable information products.
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Title: THE DEVELOPMENT OF THE WISHNICK LEARNING CENTER: A DIGITAL MEDIA CENTER
Creator: SMITH, KEVIN G.
Date: 2004-03
Description: This research paper presents a case to establish a central location for multimedia usage, resources and services for both the IIT community...
Show moreThis research paper presents a case to establish a central location for multimedia usage, resources and services for both the IIT community and external communities on the campus of Illinois Institute of Technology. Though a two phased research process, I worked to established baseline multimedia resource data from 10 separate university schools which in turn helped me to collect current multimedia resources information on all service providers on IIT campuses. The final step was to create and implement a detailed survey assessment of current IIT students and alumni, faculty and staff, community users, on campus service providers and partners on the impressions current impressions and needs of multimedia services on campus. I concluded that through more communication and collaboration between existing campus multimedia service providers and partners, plus open communication with the clients, IIT could better allocate current multimedia resources on campus for all respective clientele. By combining both financial and human resources and centralizing the efforts to one location, the campus can begin the current and growing need for more multimedia resources and services on campus. However, more in-depth research and assessment of current and future client needs are required to help support the case, while paying particular attention to current faculty skill set, incoming student skill set, and the surrounding community development in the area of technological skill set. Hypothesis and Objectives My hypothesis is that centralized multimedia resources and services on IIT's campuses would provide clients with more cost-effective, efficient services than the decentralized multimedia resources and services that are currently provided. Additionally, I plan to make recommendations for the role, staffing, facility usage, and placement of a new centrally located multimedia facility. The objectives of this research are to obtain insights, determine needs, and list accomplishments for multimedia facility usage currently provided on IIT campuses. I am also collecting information from faculty, students, and staff regarding current usage and projected multimedia needs. Information collected from the research will also help to establish future recommendations for the development of a Multimedia and Instructional Technology (MIT) facility on campus, (currently known as the Digital Media Center), and determine recommendations for current computer and technology resources on campus utilized by participants in the survey.
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Title: RUNTIME FOR PERFORMING EXACT TESTS ON THE PI STATISTICAL MODEL FOR RANDOM GRAPHS
Creator: Dillon, Martin
Date: 2016, 2016-05
Description: In statistics, we ask whether some statistical model ts observed data. We use a Markov chain proposed by Gross, Petrovi c, and Stasi to...
Show moreIn statistics, we ask whether some statistical model ts observed data. We use a Markov chain proposed by Gross, Petrovi c, and Stasi to perform exact testing for the p1 random graph model. By comparing it to the simple switch Markov chain, we prove that it mixes rapidly on many classes of degree sequences, and we discuss why it is sometimes better suited than the simple switch chain, and try to easily introduce the concepts from the general theory along the way.
M.S. in Applied Mathematics, May 2016
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Title: Leveraging the flexibility of Islandora to create a dual-use digital repository
Creator: Esquivel, Alicia, Fluhr, Tim, Strohm, Adam
Date: 2021, 2021
Publisher: Henry Stewart Publications
Collection: Journal of Digital Media Management

Title: Investigation of Novel Solid Polymer Electrolytes and Lithium Salts for Rechargeable Lithium Batteries
Creator: Zhao, Wendy
Date: 2021
Description: Lithium-ion batteries (LIBs) are extensively used in many consumer electronic products. LIBs have great potential for application in electric...
Show moreLithium-ion batteries (LIBs) are extensively used in many consumer electronic products. LIBs have great potential for application in electric vehicles by virtue of their high power density and charge cycles. Research and development in this area has been focused on all around the globe. The major challenges include high cost, safety issues of the solvent based electrolytes, and low conductivities at ambient temperature of the solid polymer electrolytes (SPEs).This dissertation describes four novel electrolyte systems and a series of low lattice energy lithium salts synthesized and characterized for applications in LIBs. First, a new SPE has been derived from oligomeric poly(ethylene oxide) (PEO)-grafted crosslinked polystyrene (XPS) microspheres containing 1-2 lithium sulfonate moieties. This SPE possesses amorphous character with a glass transition temperature (Tg) around 135 ºC, displayed a good electrochemical stability with excellent ionic conductivity in excess of 10^-4 S/cm at 25ºC, and no significant thermal decomposition until 420 ºC. Second, a hybrid composite polymer electrolyte (CPE) was constructed with a gel matrix formed through hydrogen bonding by incorporating nanoparticles of fumed silica into the nanoscale network of PEO-XPS. Fumed silica with large surface modification group like polysiloxane formed an ideal gel structure offering significant high mechanical strength above 10^4 Pa, and a good ionic conductivity at 25°C. Third, a nonvolatile x-linked gel membrane electrolyte was synthesized with amino methacrylate, to introduce hemi-labile ligands as ionic liquid, into the polymer network. This new material exhibited improved salt solubility and ionic conductivity, due to the fast ligand exchange that facilitates the lithium ion structural transport, and also displayed an excellent electrochemical stability(4.8 V vs, Li/Li+). Fourth, a self-healing and thermal reversible polymer electrolyte designed based on Diels-Alder conjugation between multi-maleimides (2M-3M) and multi-furans (2F-4F) was synthesized. The reversible x-linking was realized through Diels-Alder (DA) and Retro-DA reactions by applying heating (>130°C)/cooling (<90°C) cycles. Last, new lithium salts with star and branch structures containing 1-4 of imide or methide moieties were synthesized and evaluated in PEO electrolyte system. These salts demonstrated good ambient temperature ionic conductivity at low concentrations, and the electrochemical stabilities were equal to or better than the most commonly used lithium salt, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Synthesis and characterization, including electrochemical properties, thermal and electrochemical stabilities, mechanical behaviors and surface morphologies of these new materials are described and discussed.
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Title: BLOCKCHAIN FOR TRANSACTIVE ENERGY MARKET WITH NETWORKED MICROGRIDS
Creator: Yan, Mingyu
Date: 2021
Description: Transactive energy, which allows and incentivizes microgrids (MGs) to trade energy with each other, is regarded as the next-generation energy...
Show moreTransactive energy, which allows and incentivizes microgrids (MGs) to trade energy with each other, is regarded as the next-generation energy management scheme to accommodate the penetration of distributed energy resources (DERs). Blockchain provides an effective and decentralized strategy, which can address the operational challenges introduced by the transactive energy market. This thesis is aimed at providing effective transactive energy markets for incentivizing MGs to trade energy and utilizing blockchain technologies to provide a secure and efficient energy trading environment for all participants.First, this thesis offers a centralized transactive market for networked MGs to transact energy through the centralized distribution system operator (DSO) while ensuring the power network limits. All MGs cooperate in this market and the cooperative behaviors are captured using the cooperative game with externalities. A two-level problem is studied to allocate the total payoff to all participating MGs. Numerical results for a 4-MG system and the IEEE 33-bus show the validity of the centralized transactive energy model. Second, this thesis proposes a two-level network-constrained peer-to-peer (P2P) transactive energy for multi-MGs, which guarantees the distribution power network security and allows MGs to trade energy with each other flexibly. At the lower level, a P2P transactive energy is employed for multi-MGs to trade energy with each other. A multi-leader multi-follower (MLMF) Stackelberg game approach is utilized to model the energy trading process among MGs. At the upper level, the DSO reconfigures the distribution network based on the P2P transactive energy trading results by applying the AC optimal power flow considering the distribution network reconfiguration. If there are any network violations, the DSO requests energy trading adjustments at the lower level for network security. Numerical results for a 4-MG system, the modified IEEE 33-bus, and the 123-bus distribution power systems show the effectiveness of the proposed transactive energy model and its solution technique. Third, this thesis adopts the blockchain for the peer-to-peer transactive energy market among MGs. A two-level integrated blockchain-power system is provided, in which all MGs and the DSO are equipped with blockchain. At the lower level, MGs trade energy with each other through the lower-level MG blockchain, while the DSO manages the network security through the upper level DSO blockchain. We illustrate how to utilize blockchain technologies, i.e., public and private keys and smart contracts, to provide an efficient and secure energy trading environment for all MGs. Last, this thesis applies the blockchain for transacting energy and carbon right for networked MGs. MGs transact energy and carbon right through the centralized DSO while ensuring the power network limits. The introduction of blockchain achieves secure and decentralized market settlements in this centralized market. Numerical results for a 4-MG system and modified IEEE 33-bus systems show the effectiveness of the proposed transactive energy and carbon market.
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Title: IMPROVING DEEP LEARNING BASED SEMANTIC SEGMENTATION USING CONTEXT INFORMATION
Creator: Xia, Zhengyu
Date: 2021
Description: Semantic segmentation is an important but challenging task in computer vision because it aims to assign each pixel a category label accurately...
Show moreSemantic segmentation is an important but challenging task in computer vision because it aims to assign each pixel a category label accurately. Nowadays, applications such as autonomous driving, path navigation, image search engine, or augmented reality require accurate semantic analysis and efficient segmentation mechanisms. In this thesis, we propose multiple models to improve the performance of semantic segmentation. In the first part, we focus on the single-task network, which aims to improve the performance of semantic segmentation. Our research includes exploiting context information using mixed spatial pyramid pooling to extract dense context-embedded features in FCN-based semantic segmentation. We also propose a GAF module to generate a global context-based attention map to guide the shallow-layer feature maps for better pixel localization. In the second part, we focus on a multi-task network that incorporates semantic segmentation to improve other computer vision tasks such as object detection. Specifically, a multi-task network, along with a learning strategy is designed to let semantic segmentation and object detection assist each other since they are highly correlated. Also, we include weakly-supervised multi-label semantic segmentation learning to deal with the shortage of high-quality training examples and to improve the performance of cross-domain object detection. In the third part, we focus on improving the performance of video panoptic segmentation, which is a unified network that incorporates semantic segmentation and instance segmentation using video streams. We design a new ConvLSTM pyramid to transmit spatio-temporal contextual information in our video panoptic segmentation network. Specifically, we propose a modified ConvLSTM to generate temporal contextual information. Also, we design an MSTPP module to obtain mixed spatio-temporal context-embedded feature maps. Experimental results on different datasets show that our proposed method achieves better performance compared with the state-of-the-art methods.
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Title: ANALYTIC STUDY OF THE CELLULAR FUNCTIONS OF UBL4A
Creator: Zhang, Huaiyuan
Date: 2021
Description: Ubiquitin-like protein 4A (Ubl4A) is a small protein encoded by a “housekeeping” gene that locates on the X chromosome. As a multi-functional...
Show moreUbiquitin-like protein 4A (Ubl4A) is a small protein encoded by a “housekeeping” gene that locates on the X chromosome. As a multi-functional protein, it has roles in a variety of cellular events including anti-tumorigenesis, response to DNA damage, inhibiting the fusion between autophagosome and lysosome, and docking of the tail-anchored proteins to the endoplasmic reticulum. We have previously reported that the newborns from Ubl4A-deficient mice had a high rate of mortality due to defect of AKT-dependent glucose metabolism. At the molecular level, Ubl4A directly binds with the actin related protein (Arp) 2/3 complex to accelerate the building up of the actin branching network, which further promotes the translocation and activation of the Akt, a key kinase for multiple cellular processes, from the cytosol to the plasma membrane.In further exploration of the molecular basis of Ubl4A in cell survival, here, we demonstrated that Ubl4A is critical for mitochondrial fusion and cell survival under nutrient depletion. In WT (wild-type) cells, the association of Ubl4A and the Arp2/3 complex serves as a primed “pool” of the actin branching network near mitochondria and enables mitochondria to fuse quickly for energy conservation upon starvation insult. However, such a “ready-to-go pool” of mitochondria was significantly decreased in the Ubl4A-deficient cells. As the result, the mitochondria became fragmentated, exhibited decreased trans-membrane potential, and accumulated ROS (reactive oxygen species), consequently, initiated mitochondria-mediated apoptosis. In this study, we also observed that Ubl4A-deficient mice displayed type II diabetic phenotype under a high-fat diet feeding. The preliminary results showed that these Ubl4A-deficient mice were more sensitive to glucose intolerance than their WT littermates, most likely owing to a delay in glucose uptake, and/or insulin secretion, both of which require the Arp2/3-actin branching network. We speculated that Ubl4A might be involved in cellular vesicle formation and/or secretion, but further investigation is needed to approve this hypothesis. Taken together, these findings provide a novel function of Ubl4A and further insight into the multi-functional roles of Ubl4A in mammalian cells, as well as the molecular basis for understanding the clinical relevance of Ubl4A in related human diseases.
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Title: Fate of Listeria Monocytogenes on Hard-cooked Eggs Treated With Citric Acid
Creator: Zeng, Hui
Date: 2021
Description: Commercially-prepared hard-cooked eggs are available for foodservice and to the public in retail grocers. Potential contamination with...
Show moreCommercially-prepared hard-cooked eggs are available for foodservice and to the public in retail grocers. Potential contamination with Listeria monocytogenes during or after the cooking and peeling steps is of concern since this pathogen can proliferate at refrigeration temperatures. Citric acid is a common preservative used in the food industry to treat hard-boiled eggs (HBEs). The purpose of this project was to evaluate the efficacy of citric acid treatment of HBEs to reduce the population levels of L. monocytogenes during 24 h (treatment trials) and 28 d storage (storage trials) at 5 or 25°C. Fresh eggs were boiled for 12 min, cooled to 4°C, peeled, and stored at 5°C for 24 h prior to experiments. In treatment trials, HBEs were dip inoculated with a 4-strain cocktail of rifampicin-resistant L. monocytogenes resulting in either 4 (low) or 7 (high) log CFU/egg. Eggs were air-dried 10 min, followed by treatment with pH 2.5 citric acid (PHCA) or 0.2 M citric acid (calculated as the molarity resulting in pH 2.5: MCA) at 5 or 25°C for 24 h. In treatment-storage trials, citric acid treatment of HBEs occurred before or after inoculation, followed by 28-d storage at 5 or 25°C. L. monocytogenes populations were enumerated by homogenization of eggs with BLEB and cultivation on BHI/rifampicin agar. Enrichment in BLEB was conducted if the pathogen was below the level of enumeration. Significant differences in the populations of L. monocytogenes due to temperature of the acid treatment (5 or 25°C) or the two citric acids (MCA and PHCA) were determined using Student’s T-test and ANOVA with Tukey’s post-test, p ≤ 0.05. Overall, the largest L. monocytogenes reduction occurred after 6 h treatment of HBEs with PHCA at 25°C (1.59 ± 0.00 log CFU/egg) and after 24 h with MCA at 5°C (1.23 ± 0.54 log CFU/egg) when the pathogen was inoculated at the low and high levels, respectively. In treatment-storage trials, citric acid treatment after HBE contamination resulted in a fewer number of samples where the pathogen was detected compared to when treatment occurred before contamination. Citric acid treatment for 24 h also resulted in a greater number of samples where L. monocytogenes was not detected than the 1 h treatment. The results of this study determined that L. monocytogenes could survive on HBEs treated with citric acid, regardless of treatment or storage temperature and acid concentration (PHCA or MCA).
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