8,363 research outputs found
Peer Evaluation of Video Lab Reports in a Blended Introductory Physics Course
The Georgia Tech blended introductory calculus-based mechanics course
emphasizes scientific communication as one of its learning goals, and to that
end, we gave our students a series of four peer-evaluation assignments intended
to develop their abilities to present and evaluate scientific arguments. Within
these assignments, we also assessed students' evaluation abilities by comparing
their evaluations to a set of expert evaluations. We summarize our development
efforts and describe the changes we observed in student evaluation behavior.Comment: 4 pages, 1 table, 2 figures, submitted to Summer 2014 PERC
Proceeding
Pregenomic RNA encapsidation analysis of eleven missense and nonsense polymerase mutants of human hepatitis B virus
We characterized 11 DNA polymerase mutants of human hepatitis B virus (HBV) which contain single missense or nonsense mutations in the various domains within this gene. Except for mutant 738, a tight association between DNA replication and RNA packaging of these missense pol mutants was observed. Further analysis of HBV core particle-associated RNA indicated that only the 3.5-kb core-specific RNA, but not the precore-specific RNA, is selectively packaged in this tissue culture system. Previously, we have demonstrated that only the 3.5-kb core-specific RNA can serve as an efficient template for pol translation. Taken together, our results suggest that selectivity of HBV RNA packaging occurs as a result of selective translation of pol-containing mRNAs. Furthermore, our data suggest that the RNA encapsidation domain of pol overlaps with all of the domains of pol involved in the synthesis of terminal protein, as well as DNA replication. Finally, on the basis of gradient centrifugation analysis, a pol defect appeared to have no negative effect on the assembly or stability of core particles. A new method to assay RNA encapsidation, as well as potential RNase H activity, is reported
The Initial State of Students Taking an Introductory Physics MOOC
As part of a larger research project into massively open online courses
(MOOCs), we have investigated student background, as well as student
participation in a physics MOOC with a laboratory component. Students completed
a demographic survey and the Force and Motion Conceptual Evaluation at the
beginning of the course. While the course is still actively running, we have
tracked student participation over the first five weeks of the eleven-week
course.Comment: Accepted to PERC Proceedings 201
The mixed black hole partition function for the STU model
We evaluate the mixed partition function for dyonic BPS black holes using the
recently proposed degeneracy formula for the STU model. The result factorizes
into the OSV mixed partition function times a proportionality factor. The
latter is in agreement with the measure factor that was recently conjectured
for a class of N=2 black holes that contains the STU model.Comment: 14 page
Finite resolution measurement of the non-classical polarization statistics of entangled photon pairs
By limiting the resolution of quantum measurements, the measurement induced
changes of the quantum state can be reduced, permitting subsequent measurements
of variables that do not commute with the initially measured property. It is
then possible to experimentally determine correlations between non-commuting
variables. The application of this method to the polarization statistics of
entangled photon pairs reveals that negative conditional probabilities between
non-orthogonal polarization components are responsible for the violation of
Bell's inequalities. Such negative probabilities can also be observed in finite
resolution measurements of the polarization of a single photon. The violation
of Bell's inequalities therefore originates from local properties of the
quantum statistics of single photon polarization.Comment: 15 pages, 5 figures and 1 table, new figure to illustrate results,
improved explanation of statistical analysi
d-Wave Pairing Correlation in the Two-Dimensional t-J Model
The pair-pair correlation function of the two-dimensional t-J model is
studied by using the power-Lanczos method and an assumption of monotonic
behavior. In comparison with the results of the ideal Fermi gas, we conclude
that the 2D t-J model does not have long range d-wave superconducting
correlation in the interesting parameter range of . Implications
of this result will also be discussed.Comment: 4 pages, 6 figures, accepted by PR
Low energy physical properties of high-Tc superconducting Cu oxides: A comparison between the resonating valence bond and experiments
In a recent review by Anderson and coworkers\cite{Vanilla}, it was pointed
out that an early resonating valence bond (RVB) theory is able to explain a
number of unusual properties of high temperature superconducting (SC)
Cu-oxides. Here we extend previous calculations \cite{anderson87,FC
Zhang,Randeria} to study more systematically low energy physical properties of
the plain vanilla d-wave RVB state, and to compare results with the available
experiments. We use a renormalized mean field theory combined with variational
Monte Carlo and power Lanczos methods to study the RVB state of an extended
model in a square lattice with parameters suitable for the hole doped
Cu-oxides. The physical observable quantities we study include the specific
heat, the linear residual thermal conductivity, the in-plane magnetic
penetration depth, the quasiparticle energy at the antinode , the
superconducting energy gap, the quasiparticle spectra and the Drude weight. The
traits of nodes (including , the Fermi velocity and the velocity
along Fermi surface ), as well as the SC order parameter are also
studied. Comparisons of the theory and the experiments in cuprates show an
overall qualitative agreement, especially on their doping dependences.Comment: 12 pages, 14 figures, 1 tabl
New high-efficiency source of photon pairs for engineering quantum entanglement
We have constructed an efficient source of photon pairs using a
waveguide-type nonlinear device and performed a two-photon interference
experiment with an unbalanced Michelson interferometer. Parametric
down-converted photons from the nonlinear device are detected by two detectors
located at the output ports of the interferometer. Because the interferometer
is constructed with two optical paths of different length, photons from the
shorter path arrive at the detector earlier than those from the longer path. We
find that the difference of arrival time and the time window of the coincidence
counter are important parameters which determine the boundary between the
classical and quantum regime. When the time window of the coincidence counter
is smaller than the arrival time difference, fringes of high visibility
(80 10%) were observed. This result is only explained by quantum theory
and is clear evidence for quantum entanglement of the interferometer's optical
paths.Comment: 4 pages, 4 figures, IQEC200
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