Impact!: Improving Student Learning through an Inquiry Crater Investigation

The fight against student compartmentalization of science concepts is an ongoing battle for all science educators. When an inquiry-based investigation of natural phenomena, like that presented here, is integrated into curricula new links between science concepts are created. These new connections promote a deep and robust understanding of science content. This cratering activity has students applying prior knowledge of gravitational forces, momentum, conservation of energy, and density while exploring the intricate relationships between these fundamental concepts. This activity also provides abundant opportunities for explicit connections to the nature of science. Impact cratering is a phenomena which can be easily modeled within a classroom, and deeply understanding it requires application of several fundamental science concepts. This article addresses National Science Education Standards A, B, D, and G and Iowa Teaching Standards 1, 2, 3, 4, and 5

Impact of stout-link smearing in lattice fermion actions

The impact of stout-link smearing in lattice fermion actions is examined through the consideration of the mass and renormalization functions of the overlap quark propagator over a variety of smeared configurations. Up to six sweeps of stout-link smearing are investigated. For heavy quark masses, the quark propagator is strongly affected by the smearing procedure. For moderate masses, the effect appears to be negligible. A small effect is seen for light quark masses, where dynamical mass generation is suppressed through the smearing procedure.Comment: 7 pages, 3 figures, presented at the XXVII International Symposium on Lattice Field Theory - LAT2009, July 26-31 2009, Peking University, Beijing, Chin

Stout-link smearing in lattice fermion actions

The properties of the momentum space quark propagator in Landau gauge are studied for the overlap quark action in quenched lattice QCD. Numerical calculations are performed over four ensembles of gauge configurations, where three are smeared using either 1, 3, or 6 sweeps of stout-link smearing. We calculate the non-perturbative wave function renormalization function $Z(p)$ and the non-perturbative mass function $M(p)$ for a variety of bare quark masses. We find that the wave-function renormalization function is slightly sensitive to the number of stout-link smearing sweeps. For the mass function we find the effect of the stout-link smearing algorithm to be small for moderate to light bare quark masses. For a heavy bare quark mass we find a strong dependence on the number of smearing sweeps.Comment: 8 pages, 4 figure

Low-lying Odd-parity States of the Nucleon in Lattice QCD

The world's first examination of the odd-parity nucleon spectrum at light quark masses in 2+1 flavor lattice QCD is presented. Configurations generated by the PACS-CS collaboration and made available through the ILDG are used, with the lightest pion mass at 156 MeV. A novel method for tracking the individual energy eigenstates as the quark mass changes is introduced. The success of this approach reveals the flow of the states towards the physical masses. Using the correlation matrix method, the two lowest-energy states revealed are found to be in accord with the physical spectrum of Nature.Comment: 5 page

Roper Resonance in 2+1 Flavor QCD

The low-lying even-parity states of the nucleon are explored in lattice QCD using the PACS-CS collaboration 2+1-flavor dynamical-QCD gauge-field configurations made available through the International Lattice Datagrid (ILDG). The established correlation-matrix approach is used, in which various fermion source and sink smearings are utilized to provide an effective basis of interpolating fields to span the space of low-lying energy eigenstates. Of particular interest is the nature of the first excited state of the nucleon, the $N{1/2}^{+}$ Roper resonance of $P_{11}$ pion-nucleon scattering. The Roper state of the present analysis approaches the physical mass, displaying significant chiral curvature at the lightest quark mass. These full QCD results, providing the world's first insight into the nucleon mass spectrum in the light-quark regime, are significantly different from those of quenched QCD and provide interesting insights into the dynamics of QCD.Comment: 7 pages, 5 figures. Revised version with new results to appear in PL

"It wasn't slavery time anymore": foodworkers' strike at Chapel Hill, spring 1969

Intolerable working conditions provoked UNC cafeteria workers--most of them black women--to walk off their jobs. Although unprecedented, the strike came at a time and place that were already ripe for confrontation over labor, racial, and student issues. With negotiations at an impasse, scuffles between student strike supporters and opponents prompted campus administrators to close Lenoir Dining Hall. At the insistence of North Carolina's governor, Lenoir was reopened under guard of the state patrol, thereby invigorating debate about academic freedom and the university's political integrity. Later, the governor forced the evacuation of the building which strike supporters occupied. The four-week strike ended when, after extraordinary procedures, state employees throughout North Carolina received a twenty-cent increase in the minimum wage. This study surveys conditions prior to the walkout, outlines strike events chronologically, and assesses the assumptions and strategies of participants

GeoGebra for learning and teaching: A parallel investigation

In the study reported on here, we investigated the effects of the use of dynamic geometry software (DGS) (i.e., GeoGebra) on learners’ learning and a teacher’s beliefs. The learners and teacher involved in the study were from a high-poverty, rural high school in South Africa. We compared grade 11 learners (N = 56) who used GeoGebra in the context of learning circle geometry with learners who experienced geometry through traditional lecture-based instruction. Participating learners were from classes in a public school located in the rural Umkhanyakude district of KwaZulu-Natal, Republic of South Africa. Results showed that learners using GeoGebra were more successful at solving problems and justifying their statements, while the other learners provided a limited justification for their answers. In a parallel and complementary investigation the teacher’s attitudes toward using GeoGebra as an instructional tool were considered qualitatively. Results showed that even in high-poverty, rural settings where the availability of technological resources are limited, the use of GeoGebra affected learners’ learning and had positive effects on the teacher’s beliefs regarding teaching and learning. Keywords: Euclidean geometry; GeoGebra; performance; theorems and proof

Scaling behavior of quark propagator in full QCD

We study the scaling behavior of the quark propagator on two lattices with similar physical volume in Landau gauge with 2+1 flavors of dynamical quarks in order to test whether we are close to the continuum limit for these lattices. We use configurations generated with an improved staggered (``Asqtad'') action by the MILC collaboration. The calculations are performed on $28^3\times 96$ lattices with lattice spacing $a = 0.09$ fm and on $20^3\times 64$ lattices with lattice spacing $a = 0.12$ fm. We calculate the quark mass function, $M(q^2)$, and the wave-function renormalization function, $Z(q^2)$, for a variety of bare quark masses. Comparing the behavior of these functions on the two sets of lattices we find that both $Z(q^2)$ and $M(q^2)$ show little sensitivity to the ultraviolet cutoff.Comment: 6 pages, 5 figure

Joint stiffness is heritable and associated with fibrotic conditions and joint replacement

ObjectiveJoint stiffness is a common, debilitating, age-related symptom, which may be seen after total joint replacement (TJR). Stiffness also occurs in fibrotic conditions such as shoulder capsulitis and Dupuytren's contracture. We speculated that the two traits (TJR and fibrotic disease) are linked pathogenically.MethodsUsing the TwinsUK NIHR BRC BioResource we tested the hypotheses that 1) joint (hip and knee) stiffness, TJR (hip and knee), and fibrotic conditions are associated and 2) genetic factors contribute to them.ResultsParticipating twins (n = 9718) had completed self-reported questionnaires on the traits of interest. All three traits were significantly associated with increasing age and body mass index (BMI), as well as female sex, on univariate analysis. Multivariable logistic regression analyses showed a significant association between TJR and joint stiffness (OR = 3.96, 95% confidence interval, CI 2.77-5.68) and between fibrotic conditions and joint stiffness (OR = 2.39, 1.74-3.29), adjusting for age, sex, BMI and twin relatedness. Monozygotic versus dizygotic intraclass correlations gave heritability estimates for TJR = 46% and joint stiffness = 32%.ConclusionThat fibrotic conditions, joint stiffness and TJR are significantly associated suggests a common disease process, possibly fibrosis, which is genetically mediated

Scaling behavior and positivity violation of the gluon propagator in full QCD

The Landau-gauge gluon propagator is studied using the coarse and fine dynamical MILC configurations. The effects of dynamical quarks are clearly visible and lead to a reduction of the nonperturbative infrared enhancement relative to the quenched case. Lattice spacing effects are studied and found to be small. The gluon spectral function is shown to clearly violate positivity in both quenched and full QCD.Comment: 7 pages, 9 figures. References and 1 figure added, minor text modifications, version to be published in PR