Development and Implementation of An Introduction To Stem Course For Dual-Enrollment Programs

A new Introduction to Science, Technology, Engineering, and Mathematics (STEM) course was developed and taught for the first time during the summer in 2009 to dual enrollment college students at South Texas College (STC). The new Introduction to STEM course was developed in collaboration between STEM Faculty members at the University of Texas-Pan American (UTPA) and STC, with the objective of creating, supporting and strengthening STEM pathways for students in the Dual-Enrollment Engineering Academy (DEEA) and other dual-enrollment or similar programs. The course was offered to two groups of students, at two different campuses in the DEEA program at STC. DEEA students take college courses to accomplish an associate degree in Engineering by the end of their senior year of high school. Challenge-based instruction (CBI) was implemented in this new course; challenges, lecture and handout materials, hands-on activities, and assessment tools were developed and implemented in the areas of basic electronics, mechatronics, renewable energy, statics, dynamics, chemistry, reverse engineering, and forward engineering. This paper describes the new course development and implementation, as well as its impact on students and Faculty, including the student assessment results and the interaction of Faculty members from both institutions. The instruction materials and tools developed for the new course could be modified and adapted for implementation in other engineering and science courses at UTPA, STC, and other institutions to increase and improve educational challenges and hands-on activities in the curricula and in recruiting programs and/or activities

A comparative study of polyurethane nanofibers with different patterns and its analogous nanofibers containing MWCNTs

Tissue engineering is a multidisciplinary field that has evolved in various dimensions in recent years. One of the main aspects in this field is the proper adjustment and final compatibility of implants at the target site of surgery. For this purpose, it is desired to have the materials fabricated at the nanometer scale, since these dimensions will ultimately accelerate the fixation of implants at the cellular level. In this study, electrospun polyurethane nanofibers and their analogous nanofibers containing MWCNTs are introduced for tissue engineering applications. Since MWCNTs agglomerate to form bundles, a high intensity sonication procedure was used to disperse them, followed by electrospinning the polymer solutions that contained these previously dispersed MWCNTs. Characterization of the produced nanofibers has confirmed production of different non-woven mats, which include random, semi-aligned and mostly aligned patterns. A simultaneous and comparative study was conducted on the nanofibers with respect to their thermal stability, mechanical properties and biocompatibility. Results indicate that the mostly aligned nanofibers pattern presents higher thermal stability, mechanical properties, and biocompatibility. Furthermore, incorporation of MWCNTs among the different arrangements significantly improved the mechanical properties and cell alignment along the nanofibers

Microscopic and Spectroscopic Studies of Thermally Enhanced Electrospun PMMA Micro- and Nanofibers

Carbon nanofibers (CNFs) have been incorporated into poly(methyl methacrylate) (PMMA) through electrospinning. The resulting micro- and nanofibers have been characterized by Scanning Electron Microscopy (SEM), which confirmed fiber formation and demonstrated a core-sheath structure of the PMMA fibers. Thermogravimetric Analysis (TGA) was used to obtain the thermal properties of the materials, indicating an enhancement in the thermal properties of the composite fibers. In addition, Fourier Transform Infrared Spectroscopy (FTIR) was utilized to investigate the interactions of PMMA micro- and nanofibers with CNFs, demonstrating the preferred sites of intermolecular interactions between the polymer matrix and the filler

Nitroxide-Functionalized Graphene Oxide from Graphite Oxide

A facile method for preparing functionalized graphene oxide single layers with nitroxide groups is reported herein. Highly oxidized graphite oxide (GO=90.6%) was obtained, slightly modifying an improved Hummer’s method. Oxoammonium salts (OS) were investigated to introduce nitroxide groups to GO, resulting in a one-step functionalization and exfoliation. The mechanisms of functionalization/exfoliation are proposed, where the oxidation of aromatic alcohols to ketone groups, and the formation of alkoxyamine species are suggested. Two kinds of functionalized graphene oxide layers (GOFT1 and GOFT2) were obtained by controlling the amount of OS added. GOFT1 and GOFT2 exhibited a high interlayer spacing (d0001 = 1.12nm), which was determined by X-ray diffraction. The presence of new chemical bonds C-N (~9.5 %) and O-O (~4.3 %) from nitroxide attached onto graphene layers were observed by X-ray photoelectron spectroscopy. Single-layers of GOFT1 were observed by HRTEM, exhibiting amorphous and crystalline zones at a 50:50 ratio; in contrast, layers of GOFT2 exhibited a fully amorphous surface. Fingerprint of GOFT1 single layers was obtained by electron diffraction at several tilts. Finally, the potential use of these materials within Nylon 6 matrices was investigated, where an unusual simultaneous increase in tensile stress, tensile strain and Young’s modulus was observed

Effect of Polymer Concentration Rotational Speed and Solvent Mixture On Fiber Formation Using Forcespinning®

Polycaprolactone (PCL) fibers were produced using Forcespinning® (FS). The effects of PCL concentration, solvent mixture, and the spinneret rotational speed on fiber formation were evaluated. The concentration of the polymer in the solvents was a critical determinant of the solution viscosity. Lower PCL concentrations resulted in low solution viscosities with a correspondingly low fiber production rate with many beads. Bead-free fibers with high production rate and uniform fiber diameter distribution were obtained from the optimum PCL concentration (i.e., 12.5 wt%) with tetrahydrofuran (THF) as the solvent. The addition of N, N-dimethylformamide (DMF) to the THF solvent promoted the gradual formation of beads, split fibers, and generally affected the distribution of fiber diameters. The crystallinity of PCL fibers was also affected by the processing conditions, spinning speed, and solvent mixture

Imaging, Spectroscopy, Mechanical, Alignment and Biocompatibility Studies of Electrospun Medical Grade Polyurethane (Carbothane™ 3575A) Nanofibers and Composite Nanofibers Containing Multiwalled Carbon Nanotubes

In the present study, we discuss the electrospinning of medical grade polyurethane (Carbothane™ 3575A) nanofibers containing multi-walled-carbon-nanotubes (MWCNTs). A simple method that does not depend on additional foreign chemicals has been employed to disperse MWCNTs through high intensity sonication. Typically, a polymer solution consisting of polymer/MWCNTs has been electrospun to form nanofibers. Physiochemical aspects of prepared nanofibers were evaluated by SEM, TEM, FT-IR and Raman spectroscopy, confirming nanofibers containing MWCNTs. The biocompatibility and cell attachment of the produced nanofiber mats were investigated while culturing them in the presence of NIH 3T3 fibroblasts. The results from these tests indicated non-toxic behavior of the prepared nanofiber mats and had a significant attachment of cells towards nanofibers. The incorporation of MWCNTs into polymeric nanofibers led to an improvement in tensile stress from 11.40 ± 0.9 to 51.25 ± 5.5 MPa. Furthermore, complete alignment of the nanofibers resulted in an enhancement on tensile stress to 72.78 ± 5.5 MPa. Displaying these attributes of high mechanical properties and non-toxic nature of nanofibers are recommended for an ideal candidate for future tendon and ligament grafts

Imaging, Spectroscopic, Mechanical and Biocompatibility Studies of Electrospun Tecoflex® EG 80A Nanofibers and Composites Thereof Containing Multiwalled Carbon Nanotubes

The present study discusses the design, development and characterization of electrospun Tecoflex® EG 80A class of polyurethane nanofibers and the incorporation of multiwalled carbon nanotubes (MWCNTs) to these materials. Scanning electron microscopy results confirmed the presence of polymer nanofibers, which showed a decrease in fiber diameter at 0.5% wt. and 1% wt. MWCNTs loadings, while transmission electron microscopy showed evidence of the MWCNTs embedded within the polymer matrix. The fourier transform infrared spectroscopy and Raman spectroscopy were used to elucidate the polymer-MWCNTs intermolecular interactions, indicating that the C-N and N-H bonds in polyurethanes are responsible for the interactions with MWCNTs. Furthermore, tensile testing indicated an increase in the Young’s modulus of the nanofibers as the MWCNTs concentration was increased. Finally, NIH 3T3 fibroblasts were seeded on the obtained nanofibers, demonstrating cell biocompatibility and proliferation. Therefore, the results indicate the successful formation of polyurethane nanofibers with enhanced mechanical properties, and demonstrate their biocompatibility, suggesting their potential application in biomedical area

Fabrication of Poly(vinylidene fluoride) (PVDF) Nanofibers Containing Nickel Nanoparticles as Future Energy Server Materials

In the present study, we introduce Poly(vinylidene fluoride) (PVDF) nanofibers containing nickel (Ni) nanoparticles (NPs) as a result of an electrospinning. Typically, a colloidal solution consisting of PVDF/Ni NPs was prepared to produce nanofibers embedded with solid NPs by electrospinning process. The resultant nanostructures were studied by SEM analyses, which confirmed well oriented nanofibers and good dispersion of Ni NPs over them. The XRD results demonstrated well crystalline feature of PVDF and Ni in the obtained nanostructures. Physiochemical aspects of prepared nano-structures were characterized for TEM which confirmed nanofibers were welloriented and had good dispersion of Ni NPs. Furthermore, the prepared nano-structures were studied for hydrogen production applications. Due to high surface to volume ratio of nanofibers form than the thin film ones, there was tremendous increase in the rate of hydrogen production. Overall, results satisfactorily confirmed the use of these materials in hydrogen production

Polycaprolactone-Based Nanofibers and their In-Vitro and In-Vivo Applications in Bone Tissue Engineering

The encouraging results using some nanomaterials for bone tissue engineering has prompted researchers to investigate additional materials and their potential applications in in-vitro and in-vivo experiments. Research data suggests that the appropriate feasibility of nanomaterials can be obtained when these are fine-tuned into a scaffold with excellent biocompatibility, without immunological response, and desired biodegradability until new bone formation materializes. Osteoinductivity results from the osteointegration after mechanical interlocking with the material surface occurs, and/or due to the physio-chemical nature mimicking the original bone of the designed nanomaterials. Among the abundance of synthetic polymers, polycaprolactone (PCL) is readily processed into nanofibers using electrospinning or other similar techniques, and their resulting web-like structures (i.e., in the form of electrospun nanofibers) makes them the ideal candidate for mimicking the extracellular matrix present in the bone. Typically, as-spun PCL nanofibers can potentially enhance cell attachment, proliferation, and can boost cell infiltration due to small and large pore sizes, which are appropriate features that favor the growth of soft tissues. However, PCL nanofibers in their pristine form have also proven useful for growing osteoclasts, osteoblasts, osteocytes, and chondrocytes, which are essential for hard tissue regeneration. Nevertheless, to develop a scaffold that holds particular importance in the conversion of a soft-to-hard interface, a series of modifications are needed to create an ideal platform for bone growth. Moreover, the current challenges faced by bone tissue engineering include the need to bridge the barrier for getting vascularized at the defect site, excellent mechanical strength of the nanofibers, immune integration, and vascularization. Therefore, research is more focused on creating functional nanomaterials, which can overcome these issues and can ideally seal the gaps due to insufficient vascularization. In this chapter, we report different fabrication strategies to prepare PCL scaffolds for use in bone regeneration. Extensive descriptions of PCL based frameworks used as bone regenerating materials are discussed in context with the latest developments. In addition to electrospinning, we also introduce different techniques used to prepare PCL nanofibers for various hard tissue related applications. In brief, this chapter will highlight the fabrication strategies using mixed solvents, and how changing these parameters affects the overall nanofibers production

4,4′-(1,1,1,3,3,3-Hexafluoro­propane-2,2-diyl)bis­(benzoyl chloride)

In the structure of the title mol­ecule, C17H8Cl2F6O2, the dihedral angle between the least-squares planes of the benzene rings is 66.31 (15)°. The CF3 groups adopt an eclipsed conformation