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REU Participants

2007


2007 Research Experience for Undergraduates Participants


Amar Bains

Amar Bains

Home Institution: University of Pennsylvania
Major/Minor: Bioengineering
MRSEC Mentor: Robert Tranquillo

Effect of Mechanical Stretching on Cell-Seeded Fibrin-Based Tubular Construct: Comparison of Expression of Collagen I and III

The goal of tissue engineering is to develop treatments that allow full regeneration of tissue functionality after disease or injury. As part of this aim, it is important to investigate how to induce engineered tissue to mimic the mechanical properties of native tissue, and then characterizing the biological basis of these properties. Mechanical properties of engineered tissues can be enhanced through mechanical stimulation; however, it is not clear how differing methods of stimulation influence tissue properties. The purpose of my project is to determine how human dermal fibroblasts in a tubular fibrin scaffold respond to increasing cyclic circumferential strain over three weeks. After harvest, mechanical properties of the tissue will be determined through axial loading tests, while the expression levels of collagen I and III, the major load-bearing tissue structures, will be found using immunohistochemistry. Literature reveals that the ratio of collagen III to I is correlated to the overall mechanical properties of the tissue, and it is expected that this ratio will be increased by straining.


David Bunck

David Bunck

Home Institution: University of Wisconsin — Madison
Major/Minor: Chemistry and Religious Studies
MRSEC Mentor: Frank Bates

Influence of Nanometer Sized Silica Particles on Epoxies with Tunable Crosslink Density

Epoxy thermosets are currently utilized in a number of important structural applications where light weight, high strength, and high use temperature are required. Commercially, rigid inorganic particles have been utilized to decrease epoxy shrinkage, increase stiffness, and impart characteristics such as flame retardation or electrical conductivity. This research will examine what effect of ca. 15-20 nanometer sized silica particles will have on the mechanical properties of an epoxy. The molecular weight between crosslinks (Mc) will be systematically adjusted using a controllable epoxy thermoset (CET) allowing for the study of the silica particles' ability to modify epoxies of varying network sizes. Young's Modulus (E), the critical stress intensity factor (KIc), and the critical strain energy release rate (GIc) will be determined though compact tension and dynamic mechanical testing, while greater structural insight will be gained through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Overall, we expect an improvement in the mechanical properties of the silica modified epoxy through a relative increase of E, KIc, and GIc with respect to the unmodified system.


Melissa Burford

Melissa Burford

Home Institution: Howard University
Major/Minor: Biology/Chemistry
MRSEC Mentor: Chun Wang

The improvement of synthetic vectors for the delivery of plasmid DNA

One current method of DNA vaccine delivery is through synthetic vectors. The goal of these synthetic vectors is to deliver plasmid DNA to cells with low to no cytotoxic side-effects. We are testing diblock copolymers that consist of cationic polymers and hydrophilic poly(ethylene glycol) (PEG). The cationic polymers will electrostatically bind with DNA's negatively charged phosphate groups to yield a nanoparticle, while leaving PEG to stabilize the nanoparticle. This nanoparticle will be taken up by cells releasing DNA, which will then travel to the nucleus. Our goal is to test the efficiency of three diblock copolymers PEG-b-PAEM75, PEG-b-PIAEM, PEG-b-PHAEM.


Kathleen Crawford

Kathleen Crawford

Home Institution: University of Florida
Major/Minor: Materials Science and Engineering
MRSEC Mentor: Beth Stadler

Fabricating Byte Patterned Media Using Self-Assembled Anodized Aluminum Oxide

Continuous magnetic recording media which is currently used in hard drives has a theoretical information storage limit of 500 Gbytes/in2. Another option for recording media is byte patterned media (BPM). This aims to increase the storage density by creating a regular, repeating pattern. Anodized aluminum oxide (AAO) can be used to fabricate an ordered design on magnetic recording media. AAO is an inexpensive, bottom-up, self assembly process used to manufacture pores ranging in size from 10-150 nm. The AAO serves as a mask to layer Cr onto the substrate. Then fabrication techniques such as ion beam milling can be used to create byte patterned media.


Samuel Eisenberg

Samuel Eisenberg

Home Institution: Harvey Mudd College
Major/Minor: Physics
MRSEC Mentor: Chris Leighton

Anomalous Hall Effect in La1-xSrxCoO3 Single Crystals

The doped perovskite cobaltite La1-xSrxCoO3 (LSCO) exhibits a number of interesting electrical and magnetic properties. The material has doping-dependent magnetoelectronic phase separation into ferromagnetic metallic clusters embedded in a non-ferromagnetic insulating matrix. LSCO behaves as an insulator and shows hysteretic magnetoresistance at doping levels up to x = 0.17, at which point the clusters overlap and it undergoes a percolation transition, coincident with a transition to long-range ordered ferromagnetism. Reports in the literature show that LSCO and the related La1-xCaxCoO3 compound exhibit a spontaneous Hall effect of an unprecedented magnitude. Our work will continue the exploration of the Hall effect in single crystal LSCO at a variety of doping levels and temperatures in order to further describe the physical properties of this material. The aim is to correlate the Hall measurements with the known phenomenology of the magnetic phase separation.


Allison Heussler

Allison Heussler

Home Institution: Augsburg College
Major/Minor: Physics
MRSEC Mentor: Xiaoyang Zhu

Low Voltage Electrowetting on a novel dielectric

Electrowetting is a way to tune surface energy and associated contact angle at an interface. Promising applications of electrowetting include directing flow in microfluidics and for preventing proteins from denaturing on a protein microarray. However, achieving a large contact angle change in a aqueous salt solution currently requires a large and impractical voltage, of at least 100 volts, or requires changing the dielectric thinness to a nanometer thin film. We propose to create a novel dielectric by adding ionic liquid ([EMI][TFS]) to a polymer (PMMA). The effective potential of electrowetting scales inversely with the dielectric thickness, by adding an ionic liquid to the dielectric we hope to effectively reduce the dielectric thickness to the length scale of an electrical double layer (~1nm). This novel dielectric may allow us to observe electrowetting at voltages under 1 volt.


Kyle Holmberg

Kyle Holmberg

Home Institution: Northwestern University
Major/Minor: Biomedical Engineering
MRSEC Mentor: Wei Shen

Molecular Engineering of Thermal-Sensitive Bioactive Surfaces

Bioactive surfaces are applicable in cell behavior studies and tissue engineering. This project will explore a molecular engineering approach that enables thermal-sensitive presentation of bioactive signals. Controlling the relative height of poly-ethylene glycol (PEG) and an immobilized signaling molecule will allow regulation of cell accessibility. Temperature-responsive phase transition behavior of an elastin-like polypeptide (ELP) spacer provides a means to regulate the signaling molecule height. To prevent formation of molecular islands, PEG and the signaling molecule will be each linked to a distinct coiled-coil protein domain, which readily forms heterodimers. Proteins will be produced through bacterial biosynthetic machinery. PEG will be conjugated to the coil-coil protein through N-hydroxysuccinimide ester chemistry. A genetically engineered cysteine residue at a terminal site of one coiled-coil will allow immobilization of these molecules to a maleimide-coated surface. We expect that these substrates will dynamically present a model bioactive molecule, a FLAG tag, in response to temperature changes.


Carrington Howard

Carrington Howard

Home Institution: Howard University
Major/Minor: Biology/Chemistry
MRSEC Mentor: Chun Wang

The Improvement of Synthetic Vectors for the Delivery of Plasmid DNA

In the field of gene therapy, one method of growing interest is delivery via synthetic vectors. Researchers believe that DNA polymers will prove to be efficient, more economical in production, and safer than other methods such as viral vectors. We are testing are diblock copolymers that consist of the following: cationic polymers, which bond to the negatively-charged phosphate groups of DNA, and hydrophilic poly(ethylene glycol) (PEG). Once bonded and stabilized by the cationic polymer and PEG, the DNA is taken up by the cell, transported to the nucleus, and released by the polymer. The goal of our research is to test the efficiency of three different diblock copolymers: PEG-b-PAEM75, PEG-b-PIAEM, and PEG-b-PHAEM.


Chris Leonard

Chris Leonard

Home Institution: Gustavus Adolphus College
Major/Minor: Chemistry
MRSEC Mentor: Kent Mann

Synthesis, Characterization, and Drop Casting of Ruthenium-based Semiconductors

Presently, a bevy of new materials are being investigated as viable alternatives to silicon-based semiconductors. Previous research has shown that ruthenium complexes with a diimine moiety have tunable electrical properties arising from their unique crystal structures. This project specifically pertains to the synthesis and characterization of bis (2,2,6,6-tetramethyl 3,5-heptanedione) 1,10-phenanthroline Ruthenium. Theoretically, the crystal packing of this complex should improve upon its previous analogues, optimizing its electrical properties. A drop-cast technique will be used to apply the material to a thin film transistor. Ultimately, a direct study of the material's electron mobility in a transistor will demonstrate its practicality as a semiconductor.


Amy LeVee

Amy LeVee

Home Institution: Yeshiva University
Major/Minor: Pre-engineering/Physics/Math
MRSEC Mentor: E. Dan Dahlberg

The Inspection of Gadolinium at its Curie Temperature

The purpose of my research is to understand the behavior of gadolinium in its ferromagnetic and paramagnetic states, specifically around its Curie temperature. Previous research on various ferromagnetic and paramagnetic elements preformed in Dr. E. Dan Dahlberg's lab shows distinctly different behaviors for elements in these various states. This was proven by graphing phase responses against lift heights using Magnetic Force Microscopy (MFM). Lift height refers to how far the cantilever in the MFM is retracted from the sample. It is retracted proportionally from the ridges of the sample. The reason why we are testing gadolinium in particular is because gadolinium's Curie temperature is around room temperature, which is extremely convenient. The first step in this experiment is to ensure that gadolinium behaves the way other paramagnetic and ferromagnetic elements behave, following the example of the previous research. The knowledge gained from these innovative experiments should allow for a comprehensive understanding of Gadolinium susceptibility (from the phase responses) around the Curie temperature.


Jeremy Lois

Jeremy Lois

Home Institution: Macalester College
Major/Minor: Chemistry and Biology
MRSEC Mentor: Efie Kokkoli

pH-sensitive Liposomes and their Leakages within Ranging pH Environments

Liposome usage in medicine is growing. Cancer treatment uses stealth liposomes for drug delivery, reducing side effects during chemotherapy. Research into liposome drug delivery systems is ongoing. Aspects needing improvement are circulation times of the liposomes within the body and their delivery pathways. Improvements here will allow for more efficient drug delivery. This summer I am working with pH-sensitive liposomes. pH-sensitive liposomes have longer circulation times due to compatibility with physiological pH (7.4). Once internalized by the target cell, the liposomes then deteriorate in the acidic environments (pH of 6.5, 5.5, and 4.5) of endosomes, introducing their contents into the cell. pH-sensitive liposomes are composed of lipids, marker/bullet proteins, and pH-sensitive molecules. Liposomes can carry many diverse molecules and drugs. For my experiment the liposomes are incubated at 37°C in different pH solutions and contain calcein, a fluorescent dye used to measure leakage with a spectrophotometer.


Robert Mohr

Robert Mohr

Home Institution: Swarthmore College
Major/Minor: Physics
MRSEC Mentor: Paul Crowell

Non-Local AC Measurement of Spin in a Lateral Fe/GaAs Device

The manipulation of electron spin has many potential applications in future electronic devices, provided that spin can be successfully injected, controlled, and detected in semiconductors. One such method which has been shown to be successful involves the transfer of spin polarization from Fe to GaAs by applying a current across a doped Fe/GaAs interface. The net spin is detected elsewhere in the semiconductor as a voltage difference across a Fe electrode, which is sensitive to the spin orientation. This has already been accomplished using DC. However, AC would improve the signal-to-noise ratio and allow for additional analysis such as tunnel spectroscopy. AC measurements have already been attempted, but were obscured by noise introduced by the apparatus used. This summer, I will minimize the noise in the experimental setup and conduct AC measurements.


Tosin Odufuye

Tosin Odufuye

Home Institution: University of Minnesota
Major/Minor: Chemical Engineering and Physiology
MRSEC Mentor: Wei Shen

Molecular Engineering of Photo-Sensitive Bioactive Surfaces

Through molecular engineering of proteins and polymers photo-sensitive bioactive surfaces will be developed to permit tempering of immobilized signaling molecules in a momentarily controlled manner by programming photo stimuli. Binding of molecules to cell surface receptors can be controlled by the relative height difference between bioactive binding molecules and immobile polymer chains that are co-immobilized on a substrate. In our lab, surfaces are being engineered on which the height of the bioactive binding molecule (ligand) and its accessibility can be controlled by photo stimuli through the engineering of a photo sensitive phase transition behavior of the polymer spacer that links bioactive molecules to the surfaces. Once photo sensitive bioactive surfaces are developed a nick binding molecule will be engineered for dynamic presentation and its impact on stem cell fates will be examined.


Chris Sarra

Chris Sarra

Home Institution: Cornell University
Major/Minor: Materials Science and Engineering
MRSEC Mentor: Dan Frisbie

Morphology and Electrical Properties of P3HT as a Semiconducting Polymer

In recent years, poly(3-hexylthiophene) (P3HT) has proven itself to be a benchmark organic semiconducting polymer, employable in a variety of organic electronic devices (e.g. field-effect transistors, photovoltaics, etc.); however, researchers have little control over the microstructures of P3HT thin films. In order to control the morphology of these films, we propose to spin-coat various concentrations of a self-assembling diblock copolymer containing P3HT from a high boiling point solution, onto transparent, conducting substrates. We will use ultraviolet-visible light (UV-Vis) spectroscopy, profilometry, and atomic force microscopy (AFM) to characterize these spin-coated films. After fully characterizing the thin film properties of the block copolymer, we will selectively etch the PLA blocks out of the film using a base bath, leaving behind a nanoporous P3HT film. We will then fabricate ordered bulk heterojunction organic photovoltaic cells (BHJ OPVs) to further analyze the morphological and electrical properties of P3HT as a semiconducting polymer.


Carrie Stephani

Carrie Stephani

Home Institution: University of Minnesota
Major/Minor: Chemistry and Physics
MRSEC Mentor: Jeff Roberts

Dispersion of Silicon Nanoparticles in Solutions of Various Polarities

Silicon nonoparticles are of particular interest for such applications as solar cells, semi-conductors, bioprobes, and non-toxic biological markers. Silicon is ideally suited for these applications because it is inert, non-toxic, abundant, economical, and emits light once it reaches a small enough size. To produce many of these applications, it is necessary to retain the crystalline structure of silicon; however, silicon nanoparticles are susceptible to rapid oxidation. To overcome this, the particles are often coated with a monolayer, effectively passivating the crystalline silicon core. The application of this monolayer makes it necessary to determine the exact composition of the monolayer. The composition of this monolayer, as well as the size of the particle, determines the characteristic of the light emitted. For silicon nanoparticles to be of use in biological systems, they must be dispersible in water. Applications for silicon nanoparticles, however, are not limited to biology, so it is important to learn about their dispersibility in other solvents as well. Roughly half a dozen solvents with a range of polarities will be mixed with silicon nanoparticles coated with different materials to compile a table of dispersibility. Based on these results, NMR spectroscopy will be used to attempt to determine the specific nature of the organic monolayer of the surface of the particles.


Kari Tanaka

Kari Tanaka

Home Institution: Macalester College
Major/Minor: Chemistry Emphasis in Biochemistry
MRSEC Mentor: Chris Macosko

Compatibility of Immiscible Polymers by Random Copolymer

Blending immiscible polymers together can create a synergistic effect giving the blend the desirable physical properties of each polymer and minimizing the undesirable traits. The adhesion between the immiscible polymers is increased by the addition of a compatiblizer. In previous studies, the copolymer PRD 770 has show to strengthen adhesion between polystyrene (PS) and polymethyl methacrylate (PMMA). The goal is to investigate the effect the copolymer has on the coarsening rate during annealing. A decrease in the coarsening rate would indicate the copolymer is able to reach the interface and stabilize the blend.


John Tritsch

John Tritsch

Home Institution: University of Wisconsin — Eau Claire
Major/Minor: Chemistry/Physics
MRSEC Mentor: Uwe Kortshagen

Sintering of Germanium Nanocrystals

Germanium nanocrystals are of interest for efficient interconversion between electrical and light energy. Due to quantum confinement in semiconductor nanostructures, tuning of optical properties may be accomplished through modification of particle size. Control of optoelectronic properties is an intense concentration of research which may lead to more efficient lighting and photovoltaics. Production and utilization of these nano-scale materials require identified scalable processes. Germanium nanoparticle sintering will be examined by TEM monitoring of surface diffusion, particle melting, and coalescence. Because of the smaller surface to volume ratio and amplified surface tension, melting temperature and corresponding sintering temperature should prove to be indirectly proportional to particle size.


Lisa Wang

Lisa Wang

Home Institution: Carleton College
Major/Minor: Chemistry
MRSEC Mentor: Marc Hillmyer/William Tolman

Polymerization of γ-butyrolactone using Zn(II) alkoxide catalyst

Biodegradable polymers are currently used in many commercial products such as water bottles and sutures. Homopoly(γ-butyrolactone) (PBL) is a biodegradable polyester produced in nature by microorganisms. The laboratory synthesis of homoPBL via ring-opening polymerization has not been studied in detail due to γ-butyrolactone's thermodynamic stability. The goal of my project is to ring-open polymerize γ-butyrolactone using a highly active catalyst at low temperatures. First, the Zn(II) alkoxide catalyst will be synthesized. Second, polymerization of γ-butyrolactone will be attempted utilizing the Zn alkoxide catalyst at varied temperatures.


Matt Wang

Matt Wang

Home Institution: University of Tennessee — Knoxville
Major/Minor: Chemical Engineering
MRSEC Mentor: David Morse

Dissolution Kinetics of Block Copolymer Micelles

Diblock copolymers are often used as surfactants in blends of immiscible homopolymers. Copolymer is wasted if it remains bound in micelles, rather than absorbing to an interface. To transport copolymers to an interface, micelles must dissolve. Experiments and existing theory suggest that the rate of dissolution sensitively depends on the molecular weight of copolymer. This project is designed to study the dissolution kinetics of diblock copolymer micelles formed in a matrix of homopolymers with Self-Consistent Field Theory (SCFT). SCFT is the standard theoretical tool for long chain polymers, in which the free energy can be evaluated based on a statistical description of the polymer conformations. The excess free energy of forming a distinct micelle can be expressed as a function of aggregation number, which will allow us to estimate the barrier of spontaneous micelle dissolution.


Morgan Wells

Morgan Wells

Home Institution: Gustavus Adolphus College
Major/Minor: Chemistry/Biology
MRSEC Mentor: Thomas Hoye

Synthesis and Characterization of Polymer Conjugates with Anticancer Applications

A cancer drug taken intravenously typically diffuses homogenously within the body. However due to the EPR effect, if that drug is bound within a larger polymer nanoparticle it can be concentrated in the tumor, leading to a variety of benefits including lower side effects and smaller doses. Polymer and nanoparticle candidates for this application were synthesized and characterized (dynamic light scattering, SEM). Particular emphasis was placed on the rate of hydrolysis of the nanoparticle, because with future work this will determine the rate of drug release in a cancer patient.


Lynn Wolf

Lynn Wolf

Home Institution: Iowa State University
Major/Minor: Chemical Engineering and Physics
MRSEC Mentor: Frank Bates

Ternary Block Copolymer/Homopolymer Bicontinuous Microemulsions

Recently it has been shown that thermodynamically stable bicontinuous microemulsions can be made from ternary blends of two homopolymers and the corresponding diblock copolymer. Three systems of ternary blends will be compared in this study: a monodisperse diblock with a low molecular weight, a polydisperse diblock of the same low molecular weight, and a monodisperse diblock with a high molecular weight. The order-disorder transition temperature (TODT) of the blends will be found using rheological measurements, cloud point measurements and small angle x-ray scattering (SAXS). The TODT measurements will be used to construct a phase diagram for the three systems so the bicontinuous microemulsion channels can be compared. Preliminary results suggest that when polydisperse diblocks are introduced to the system, TODT is increased compared to the same system made from monodisperse diblocks.


Nick Young

Nick Young

Home Institution: Bucknell University
Major/Minor: Chemical Engineering
MRSEC Mentor: Tim Lodge

Temperature-Dependent Transport of Block Copolymer Micelles between Immiscible Liquids

Recently, the ability of block copolymers to self-assemble into micelles has drawn interest for a variety of applications, including drug delivery and phase transfer. Appropriate choice of polymer blocks and solvents allows the micelles to be reversibly transferred between layers of water and ionic liquid (IL), while remaining intact. Diblock copolymers of poly(N-isopropyl acrylamide) and poly(ethylene oxide) (PNIPAm-PEO) will be synthesized by RAFT polymerization and driven between water and an appropriate IL by varying temperature. A micelle with PEO corona and PNIPAm core will form above PNIPAm's lower critical solution temperature in water, and will transfer to the IL phase upon further heating as it becomes more favorable to PEO. The exchange can be confirmed by cryogenic transmission electron microscopy (cryo-TEM). Once in the IL, PNIPAm can be desegregated by heating above the upper critical solution temperature. This phenomenon could allow the development of a system employing temperature-controlled release of encapsulated chemicals.



Faculty-Student Team Participants

2007


Dan Hawk and Erin Thomas

Dan Hawk and Erin Thomas(not pictured)

Home Institution: College of Menominee Nation
MRSEC Mentor: Jim Kakalios

Reversing the Reversible Photoelectric Effect of Amorphous Silicon Photoconductivity

Global Warming affects the biosphere and is being addressed at the international level. Maximizing solar efficiency will increase the global energy portfolio. Amorphous silicon offers an inexpensive thin-film solar cell with high optical absorption in the visible light spectrum; however, it has a reversible photoelectric effect. This effect decreases both photo and dark conductivity of up to four orders of magnitude. We change the film properties e.g., composition, and dopants, to maximize conductivity to increase efficiency. Higher efficiencies would reduce greenhouse gases, a contributor to Global Warming.


Patrick Hawk and Tom Marsh

Patrick Hawk and Tom Marsh

Home Institution: University of St. Thomas
MRSEC Mentor: Dan Frisbie

Dielectric Alignment of a Surface Anchored Supramolecular Nucleic Acid

Nucleic acids are attractive materials for creating nanoscale devices by virtue of their inherent ability to self-assemble into complex supramolecular structures given the appropriate sequences and reaction conditions. The ability to chemically synthesize nucleic acids with any sequence enables them to be employed as a programmable scaffold components designed to self-assemble into a specific structure. One application of this property is the construction of molecular scaffolds or nanoscaffolds. These scaffolds are very useful for the positioning of other materials, such as gold nanoparticles, at regular intervals with a relatively high degree of precision. However, the positioning of the scaffolds themselves is quite random. Manipulation by a scanning probe microscopy tip or by dielectrophoretic focusing can position the scaffolds. Another way of positioning the scaffolds is to have a starting point for assembly directly on the surface. Our work deals with creating an apparatus that can test how scaffolds made of G-DNA (Tet1.5, (GGGGTTGGGG)) can be lined up in a predictable, reproducible way via dielectrophoretic focusing. Once the parameters for the focusing have been found, dielectric substrates that include starting points for the build-up of scaffolds could also be utilized.



Research Experience for Teachers (RET) Participants

2007


David Hill

David Hill

Home Institution: Afrocentric Educational Academy
MRSEC Mentor: Michael Tsapatsis

Zeolites, Nanotechnology, Spanning from the Beginning of Time in Nature to Everyday Applications

This presentation is the result of the Nanoscale Informal Science Education Network (NISE Net) which is in partnership with the Science Museum of Minnesota, Science Museum of Boston and the Exploratorium Museum of Science in San Francisco, California. Our goal is to introduce to the public, one study in Nanotechnology, which are Zeolites. Although Zeolites have been around in nature from the beginning of the earth, little is known about them and their usefulness. This presentation is an information bridging project to familiarize the general public with technology in use today using Zeolites.


Clair Hypolite

Claire Hypolite

Home Institution: Minneapolis Edison
MRSEC Mentor: Kevin Dorfman

Adapting Soft Lithography for the High School Classroom

Soft lithography is a technique with novel uses in micropatterning of surfaces and creating small channels for microfluidics research. In this research, poly dimethyl siloxane (PDMS) stamps were created using soft lithography were used in micro-contact printing in order to pattern different molecules onto glass surfaces. The resulting pattern was revealed by placing the surfaces on a bed of ice, causing selective condensation on the stamped surface. The process will be modified for use in high school classrooms, where students will use the technique to create macroscale stamps in a interdisciplinary project uniting science and art.






The University is funded through the National Science Foundation MRSEC Program, Award DMR-1420013


Contact Information

UMN MRSEC

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P: 612-626-0713 | F: 612-626-7805