«Strengthening the Nation through Diversity, Innovation & Leadership in STEM San Antonio,Texas · October 3-6, 2013 Get Connected! Connect with the ...»
Differentiation of pluripotent stem cells into a specific phenotype is a sought-after outcome for advancing bonerelated tissue engineering and tissue regeneration applications of these most promising cells. To date, biochemical compounds (e.g., bone morphogenetic proteins) have been used to promote differentiation of mesenchymal stem cells, which have the potential to differentiate into osteoblasts, chondrocytes, and adipocytes, into osteoblasts. In contrast, the effects of biophysical stimuli on such outcomes remain unknown. The present in vitro study examined the effects of electric current in the absence of supplemented exogenous growth factors on the differentiation of Engineering mesenchymal stem cells. For this purpose, adult, human mesenchymal cells were cultured on flat, indium-tin-oxidecoated glass precoated with fibronectin in the absence of supplemented exogenous growth factors. A custom-made laboratory set-up was used to expose these cells (passage 3 - 5) to alternating electric current (5 - 10 μA, 5 - 10 Hz, sinusoidal waveform), for either 3 or 6 hours daily for up to 21 consecutive days.
ANALYSIS OF FOCAL ADHESION PROPERTIES AS A FUNCTION OF DIFFERENTIATION STATEPiyumi Wijesekara Kankanange, Adam Engler, Andrew Holle.
University of California, San Diego, La Jolla, CA.
Focal adhesions are large macromolecular assemblies of the plasma membrane that allow cells to communicate with their outside environment. Various different focal adhesions exist between the cells and the extra cellular matrix.
Preliminary results indicate that focal adhesions play an important role in mechanically induced differentiation. While focal adhesions have been studied to an extensive degree, little is known as to whether focal adhesion dynamics are predictive of differentiation state across a wide range of cell types. In order to address this question, three different cell types from undifferentiated to terminally-differentiated will be characterized with respect to their focal adhesionrelated characteristics. Western blots and immunofluorescence of eight focal adhesion proteins vinculin, FAK (focal adhesion kinase), p130Cas, SORBS1, SORBS3, filamin, palladin and paxillin will be performed on all cell types plated onto substrates with stiffnesses of 1, 11, and 34 kPa, as well as glass. Focal adhesion size and distribution will also be quantified from immunofluorescence images. If a certain type of focal adhesion protein is more important for differentiation, one might conclude that this specific focal adhesion protein would be more common in less differentiated cells. This characterization of focal adhesion dynamics across a range of different human cell lines representing the continuum of potency is an important step towards the final goal of understanding whether focal adhesion characteristics are predictive of differentiation state.
THE OPTIMIZATION OF MAGNETIC COBALT CARBIDE NANOPARTICLES SYNTHESIZED VIA A POLYOLMETHOD Raziel Acosta, Hyojung Yoon.
University of California, San Diego, La Jolla, CA.
Permanent magnets are an important feature in our current technologies such as in hybrid electrical vehicles and wind generators. Developing alternatives to rare earth permanent magnets has become a critical investment due to the high costs of rare earth metals, which are primarily mined outside of the US. It was recently discovered that cobalt carbide nanoparticles produce substantial magnetic properties even though previous theoretical studies indicated they shouldn’t. Our goal is to consistently produce cobalt carbide nanoparticle assemblies that have high magnetic
181 UNDERGRADUATE POSTER ABSTRACTS
properties. In the polyol method, a wet chemical synthesis, the reactants are used in a batch reactor to produce cobalt carbide nanoparticle assemblies. By experimenting with certain reaction parameters such as the reaction time, temperature, and concentrations of reagents, different assemblies of Co3C and Co2C can be achieved. Even though Co3C has better magnetic properties than Co2C, when a mixture of the two is synthesized, even greater magnetic properties can be achieved because the Co2C phase hinders demagnetizing magnetostatic interactions that occur between neighboring Co3C phases. By using different characterization techniques such as vibrating sample magnetometery, X-ray diffraction, and transmission electron microscopy, the magnetization and coercivity, phase confirmation, and morphology of the product can be obtained, respectively. Using these methods, we will be able to determine the magnetic properties as well as the physical characteristics of our synthesized material. If cobalt carbide composites with significant magnetic properties can be consistently produced, they can rival current rare-earthdependent permanent magnets.
MUTATING THE TYPE 3 SECRETION SYSTEM IN SALMONELLA TO EXPORT HETEROLOGOUS PROTEINSElias Valdivia, Kevin Metcalf, Danielle Tullman-Ercek.
University of California, Berkeley, Berkeley, CA.
We developed a protein pump in Salmonella to continually secrete proteins that can be easily recovered from the media. Heterologous proteins are made by bacteria with recombinant DNA methods for therapeutic and industrial processes, but the purification from the cell is difficult. The proteins aggregate to form insoluble inclusion bodies in the cytoplasm when they are over expressed. During the purification process, large amounts of protein are damaged by the harsh chemicals used and are difficult to separate from other cellular contents; therefore, the recovery of the final product is not the most efficient way for industrial-level production. However, many pathogenic bacteria have a type-3 secretion system (T3SS) that is used to pump proteins out of the cell. In this work, we made point mutations to this protein pump in Salmonella enterica Typhimurium to enhance the secretion of heterologous proteins into the media. This prevents the accumulation of inclusion bodies inside the cytoplasm. In addition, the secreted proteins fold into the native state and retain normal function. To determine which mutation results in the highest protein secretion, we compared the secreted protein titer by western blotting. We screened for mutants with a strong signal in the supernatant. This indicates a high secretion of proteins.
SEISMIC PERFORMANCE AND DESIGN OF EMBEDDED STEEL COLUMN BASE CONNECTIONSEmmanuel Flores1, David Grilli2, Amit Kanvinde2.
University of California, Berkeley, Berkeley, CA, 2University of California, Davis, Davis, CA.
1 Steel column base connections are very important structural interfaces because this is where load is transferred from the entire structure to the foundation. It is common for exposed-base connections to be used in low-to-midrise buildings with moderate lateral load. However, the use of exposed-steel base connections becomes impractical for mid-to-high-rise buildings in highly seismic regions because of their difficulty in resisting large moments through tension in anchor rods and fulfilling steel anchorage requirements outlined by current building codes. For this reason, embedded steel columns are the preferred alternative to restrain column bases due to their ability to better resist moment and shear. Despite the widespread use of embedded columns, there is very little experimental data and there are no true design guidelines on this type of connection. What this investigation will do is develop a fundamental understanding of the force transfer mechanisms and demonstrate strength, stiffness, ductility, and damage states that occur in embedded steel columns. To do this, five realistically sized embedded steel columns will be taken to a strong reaction floor to be subjected to various combinations of axial compression or tension with cyclic lateral loading.
Data from these tests will be recorded as lateral force-displacement hysteretic curves, stress distributions over the embedded part of the columns, and observed failure modes. From this project, it is anticipated that the data acquired will develop new equations for strength, develop guidelines for embedded steel columns and, more importantly, lead to updates to building codes, standards, and specifications.
USING THE STEEL PLATE SHEAR WALL FOR SEISMIC HAZARD MITIGATIONDavid Alvarez1, Cheng Chen2, James Enright2, Cham Htun1, Jasmine Flores1.
Cañada College, Redwood City, CA, 2San Francisco State University, San Francisco, CA.
1 In a 10-week summer research internship program, sophomore civil engineering community college students have the opportunity to design a 3-story building structure using a steel plate shear wall lateral force resisting system in the earthquake-prone San Francisco Bay area. Buildings have to be designed with a strong infrastructure such that they will withstand severe earthquakes. The objective of this research is to understand how to implement today’s seismic technologies in designing a cost-efficient and environmentally friendly building. The use of structural engineering design specifications and seismic provisions such as ASCE 7-10 (American Society of Civil Engineering) and AISC 341-10 (American Institute of Steel Construction) promotes early exposure to building codes currently being used in Engineering the field. Computer programs such as Excel and MathCAD are used to design the innovative lateral force resisting components to optimize the structures’ performance. SAP2000 (Structural Analysis Program) is used to simulate and evaluate the response of the designed structure to selected ground motions from past earthquakes in California. This ground-motion data was acquired from the USGS Pacific Earthquake Engineering Research Center. This research internship program allows for the development of project management, time management, and teamwork skills, all of which help strengthen students’ knowledge of seismic design in civil engineering and enhance preparation for academic and professional careers. The project intends to provide community college students research opportunities and make recommendations on improving the engineering curriculum at San Francisco State University and Cañada College.
AN INVESTIGATION OF THE DESIGN AND MODELING OF SEISMIC PERFORMANCE FORTHE OLIVENHAIN
DAM AND RESERVOIRGabriela Bernaldino1, Kelly Rodgers2.
University of California, San Diego, La Jolla, CA, 2San Diego County Water Authority, San Diego, CA.
1 Eighty percent of the water used in San Diego, California, is imported through pipelines that cross several major seismic fault lines. California has many seismic issues, and public water agencies have to be creative in their engineering methods for enhancing water supply availability for emergencies and accommodating population growth.
Unanticipated events such as prolonged droughts or a catastrophic earthquake can endanger the water supply for the San Diego region. This is an ongoing issue for San Diego County. The County Water Authority determined there was a need to build the Olivenhain Dam and Reservoir. In this effort, it was critical that the dam, a roller compacted concrete gravity dam, be designed for seismic performance so that it remains operational during a maximum credible earthquake. Using the Olivenhain Dam as a case study, the dam’s design will be dissected to investigate the material properties, boundary conditions, applied loads, and the linear and dynamic analyses of the dam and reservoir.
Examining the dam model through these components will illustrate the engineering assumptions made in the design process, thus verifying that the dam is designed to remain operational during a 7.25-magnitude earthquake to support emergency water supply operations. The San Diego region is growing, and it is essential that concrete dams in seismic regions be designed to perform satisfactorily during maximum credible earthquake events.
SEISMIC EVALUATION & DESIGN: SPECIAL MOMENT-RESISTING FRAME STRUCTUREAgustin Robles1, Jose Valdovinos2, Cheng Chen2.
Cañada Community College, Redwood City, CA, 2San Francisco State University, San Francisco, CA.
1 This project focuses on designing a five-story, steel, moment-resisting frame in the earthquake-prone San Francisco Bay area in California near the Hayward fault. The structural engineer’s main priority is safety; buildings have to be designed with a strong infrastructure such that they will withstand severe earthquakes. The objective of this research is to understand how to implement today’s seismic technologies in designing a cost-efficient and environmentally friendly building. Computer-aided programs SAP2000 (Structural Analysis Program) and MS Excel are used to design, simulate, and analyze the structure. This research internship program allows for the development of project management, time management, and teamwork skills, all of which help strengthen students’ knowledge of seismic design in civil engineering and enhance preparation for academic and professional careers. The project intends to provide community college students research opportunities and make recommendations on improving the engineering curriculum at San Francisco State University and Cañada College.
MODELING AND IMPLEMENTATION OF BRAIN-INSPIRED NEURAL NETWORK FOR EDGE DETECTION AND
OBJECT RECOGNITIONNorman Ettedgui1, Rita Melgar1, Hamid Mahmoodi2.
Cañada College, Redwood City, CA, 2San Francisco State University, San Francisco, CA.