Nanotailoring Stereolithography Resins for Unique Applications using Carbon Nanotubes

Nanostructured materials and exploiting their properties in stereolithography (SL) may open new markets for unique rapidly manufactured functional devices. Controlled amounts of multiwalled carbon nanotubes (MWCNTs) were successfully dispersed in SL epoxy-based resins and complex three-dimensional (3D) parts were successfully fabricated by means of a multi-material SL setup. The effect of the nanosized filler was evaluated using mechanical testing. Small dispersions of MWCNTs resulted in significant effects on the physical properties of the polymerized resin. A MWCNT concentration of .05 wt% (w/v) in DSM Somos® WaterShed™ 11120 resin increased the ultimate tensile stress and fracture stress an average of 17% and 37%, respectively. Electron microscopy was used to examine the morphology of the nanocomposite and results showed affinity between the MWCNTs and SL resin and identified buckled nanotubes that illustrated strong interfacial bonding. These improved physical properties may provide opportunities for using nanocomposite SL resins in end-use applications. Varying types and concentrations of nanomaterials can be used to tailor existing SL resins for particular applications.Mechanical Engineerin

New conditions for the additive inverse eigenvalue problem for matrices

AbstractThis paper deals with the following inverse eigenvalue problem: Given an n by n real symmetric matrix A and a set of real numbers {λi}1n, find a diagonal matrix D such that A + D has eigenvalues λi. For the solvability of this problem a number of necessary conditions and sufficient conditions are known. In this work, new necessary conditions are derived, while some sufficient conditions are optimized. In particular, one sufficient condition due to Morel is obtained by optimizing a sufficient condition discovered by Laborde

Ghost-gluon coupling, power corrections and ΛMS‾\Lambda_{\overline {\rm MS}} from twisted-mass lattice QCD at Nf=2

We present results concerning the non-perturbative evaluation of the ghost-gluon running QCD coupling constant from $N_f=2$ twisted-mass lattice calculations. A novel method for calibrating the lattice spacing, independent of the string tension and hadron spectrum is presented with results in agreement with previous estimates. The value of $\Lambda_{\overline{MS}}$ is computed from the running of the QCD coupling only after extrapolating to zero dynamical quark mass and after removing a non-perturbative OPE contribution that is assumed to be dominated by the dimension-two \VEV{A^2} gluon condensate. The effect due to the dynamical quark mass in the determination of \Lams is discussed.Comment: 33 pages, 6 fig

Effects of a thermal inversion experiment on STEM students learning and application of damped harmonic motion

There are diverse teaching methodologies to promote both collaborative and individual work in undergraduate physics courses. However, few educational studies seek to understand how students learn and apply new knowledge through open-ended activities that require mathematical modeling and experimentation focused on environmental problems. In this work, we propose a novel home experiment to simulate the dynamics of a particulate under temperature inversion and model it as damped harmonic motion. Twenty six first year students enrolled in STEM majors answered six qualitative questions after designing and developing the experiment. These questions helped analyze the students epistemological beliefs about their learning process of physics topics and its applications. Results showed that this type of open-ended experiments could facilitate the students understanding of physics phenomena. In addition, this experiment showed that it could help physics professors to promote students epistemological development by giving their students the opportunity to search for different sources of knowledge and becoming self-learners instead of looking at the professor as the epistemological authority. At the end, students described this activity as a positive experience that helped them realize alternative ways to apply physics topics in different contexts of their environment.Comment: 23 pages, 5 figure

Evaluation of total phenolics, anthocyanins and antioxidant capacity in purple tomatillo (Physalis ixocarpa) genotypes

Purple tomatillo genotypes were evaluated for their total anthocyanin, phenolic and antioxidant capacity. The result showed that ICTS-UDG-9-224 and ICTS-UDG-9-32 had the highest amount of total phenolic compounds 10.08 and 9.6 mg GAE/g fresh weight in genotypes, respectively, followed by ICTS-UDG-1-1 and ICTS-UDG-2-2 (5.5 and 5.3 mg GAE/g fresh weight), respectively. The highest content of anthocyanins was found in the genotypes ICTS-UDG-9-32 (6.94 mg of pelargonidin 3-glucoside equivalents/g of fresh weight). In contrast, the genotypes ICTS-UDG-9-224 showed lowest values of antocyanins content. On the other hand, for total antioxidant capacity, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) methods showed that genotypes, ICTS-UDG-2-2 and ICTS-UDG-1-1 had the highest antioxidant capacity (approximately 80%) followed by genotypes ICTS-UDG-9-32 (55%) and ICTS-UDG-9-224 (28%), respectively. These results provide useful and important information for researchers in order to increase the antioxidant capacity and functional value of purple tomatillo for the food and nutraceutical industries.Key word: Antocyanins, purple tomatillos, bioactive compounds, antioxidant capacity

Artefacts and <A2> power corrections : revisiting the MOM Z_psi and Z_V

We extract the power corrections due to the A^2 condensate in the overlap quark propagator (vector part of the inverse propagator Z_psi). The results are consistent with the previous gluon analysis. The role of artefacts is extensively discussed.Comment: 33 pages, 5 figure

Geometrical approach to mutually unbiased bases

We propose a unifying phase-space approach to the construction of mutually unbiased bases for a two-qubit system. It is based on an explicit classification of the geometrical structures compatible with the notion of unbiasedness. These consist of bundles of discrete curves intersecting only at the origin and satisfying certain additional properties. We also consider the feasible transformations between different kinds of curves and show that they correspond to local rotations around the Bloch-sphere principal axes. We suggest how to generalize the method to systems in dimensions that are powers of a prime.Comment: 10 pages. Some typos in the journal version have been correcte