1,341 research outputs found
Secondary implementation of interactive engagement teaching techniques: Choices and challenges in a Gulf Arab context
We report on a "Collaborative Workshop Physics" instructional strategy to
deliver the first IE calculus-based physics course at Khalifa University, UAE.
To these authors' knowledge, this is the first such course on the Arabian
Peninsula using PER-based instruction. A brief history of general university
and STEM teaching in the UAE is given. We present this secondary implementation
(SI) as a case study of a novel context and use it to determine if PER-based
instruction can be successfully implemented far from the cultural context of
the primary developer and, if so, how might such SIs differ from SIs within the
US. With these questions in view, a pre-reform baseline of MPEX, FCI, course
exam and English language proficiency data are used to design a hybrid
implementation of Cooperative Group Problem Solving. We find that for students
with high English proficiency, normalized gain on FCI improves from =
0.16+/-0.10 pre- to = 0.47+/-0.08 post-reform, indicating successful SI. We
also find that is strongly modulated by language proficiency and discuss
likely causes. Regardless of language skill, problem-solving skill is also
improved and course DFW rates drop from 50% to 24%. In particular, we find
evidence in post-reform student interviews that prior classroom experiences,
and not broader cultural expectations about education, are the more significant
cause of expectations at odds with the classroom norms of well-functioning
PER-based instruction. This result is evidence that PER-based innovations can
be implemented across great changes in cultural context, provided that the
method is thoughtfully adapted in anticipation of context and culture-specific
student expectations. This case study should be valuable for future reforms at
other institutions, both in the Gulf Region and developing world, facing
similar challenges involving SI of PER-based instruction outside the US.Comment: v1: 28 pages, 9 figures. v2: 19 pages, 6 figures, includes major
reorganization and revisions based on anonymous peer review. v3: 19 pages, 6
figures, minor revisions based on anonymous peer revie
Development of an evaluation technique for interplanetary mission astrionics Interim scientific report
Evaluating astrionics for interplanetary flyby missions using penalty function
Spectroscopy of 13B via the 13C(t,3He) reaction at 115 AMeV
Gamow-Teller and dipole transitions to final states in 13B were studied via
the 13C(t,3He) reaction at Et = 115 AMeV. Besides the strong Gamow-Teller
transition to the 13B ground state, a weaker Gamow-Teller transition to a state
at 3.6 MeV was found. This state was assigned a spin-parity of 3/2- by
comparison with shell-model calculations using the WBP and WBT interactions
which were modified to allow for mixing between nhw and (n+2)hw configurations.
This assignment agrees with a recent result from a lifetime measurement of
excited states in 13B. The shell-model calculations also explained the
relatively large spectroscopic strength measured for a low-lying 1/2+ state at
4.83 MeV in 13B. The cross sections for dipole transitions up to Ex(13B)= 20
MeV excited via the 13C(t,3He) reaction were also compared with the shell-model
calculations. The theoretical cross sections exceeded the data by a factor of
about 1.8, which might indicate that the dipole excitations are "quenched".
Uncertainties in the reaction calculations complicate that interpretation.Comment: 11 pages, 6 figure
Impact of Pycnonuclear Fusion Uncertainties on the Cooling of Accreting Neutron Star Crusts
The observation of X-rays during quiescence from transiently accreting
neutron stars provides unique clues about the nature of dense matter. This,
however, requires extensive modeling of the crusts and matching the results to
observations. The pycnonuclear fusion reaction rates implemented in these
models are theoretically calculated by extending phenomenological expressions
and have large uncertainties spanning many orders of magnitude. We present the
first sensitivity studies of these pycnonuclear fusion reactions in realistic
network calculations. We also couple the reaction network with the thermal
evolution code dStar to further study their impact on the neutron star cooling
curves in quiescence. Varying the pycnonuclear fusion reaction rates alters the
depth at which nuclear heat is deposited although the total heating remains
constant. The enhancement of the pycnonuclear fusion reaction rates leads to an
overall shallower deposition of nuclear heat. The impurity factors are also
altered depending on the type of ashes deposited on the crust. These total
changes correspond to a variation of up to 9 eV in the modeled cooling curves.
While this is not sufficient to explain the shallow heat source, it is
comparable to the observational uncertainties and can still be important for
modeling the neutron star crust.Comment: AASTeX63, 11 pages with 9 figure
Beta-delayed proton emission in the 100Sn region
Beta-delayed proton emission from nuclides in the neighborhood of 100Sn was
studied at the National Superconducting Cyclotron Laboratory. The nuclei were
produced by fragmentation of a 120 MeV/nucleon 112Sn primary beam on a Be
target. Beam purification was provided by the A1900 Fragment Separator and the
Radio Frequency Fragment Separator. The fragments of interest were identified
and their decay was studied with the NSCL Beta Counting System (BCS) in
conjunction with the Segmented Germanium Array (SeGA). The nuclei 96Cd, 98Ing,
98Inm and 99In were identified as beta-delayed proton emitters, with branching
ratios bp = 5.5(40)%, 5.5+3 -2%, 19(2)% and 0.9(4)%, respectively. The bp for
89Ru, 91,92Rh, 93Pd and 95Ag were deduced for the first time with bp = 3+1.9
-1.7%, 1.3(5)%, 1.9(1)%, 7.5(5)% and 2.5(3)%, respectively. The bp = 22(1)% for
101Sn was deduced with higher precision than previously reported. The impact of
the newly measured bp values on the composition of the type-I X-ray burst ashes
was studied.Comment: 15 pages, 14 Figures, 4 Table
The Nd(He,) and Sm(,He) reactions with applications to decay of Nd
The Nd(He,) reaction at 140 MeV/u and Sm(,He)
reaction at 115 MeV/u were measured, populating excited states in Pm.
The transitions studied populate intermediate states of importance for the
(neutrinoless) decay of Nd to Sm. Monopole and
dipole contributions to the measured excitation-energy spectra were extracted
by using multipole decomposition analyses. The experimental results were
compared with theoretical calculations obtained within the framework of
Quasiparticle Random-Phase Approximation (QRPA), which is one of the main
methods employed for estimating the half-life of the neutrinoless
decay () of Nd. The present results thus provide useful
information on the neutrino responses for evaluating the and
matrix elements. The matrix element
calculated from the Gamow-Teller transitions through the lowest state
in the intermediate nucleus is maximally about half of that deduced from the
half-life measured in direct counting experiments and at least
several transitions through intermediate states in Pm are
required to explain the half-life.
Because Gamow-Teller transitions in the Sm(,He) experiment are
strongly Pauli-blocked, the extraction of Gamow-Teller strengths was
complicated by the excitation of the , ,
isovector spin-flip giant monopole resonance (IVSGMR). However, the near
absence of Gamow-Teller transition strength made it possible to cleanly
identify this resonance, and the strength observed is consistent with the full
exhaustion of the non-energy-weighted sum rule for the IVSGMR.Comment: 18 pages, 13 figures, 2 table
On the extraction of weak transition strengths via the (3He,t) reaction at 420 MeV
Differential cross sections for transitions of known weak strength were
measured with the (3He,t) reaction at 420 MeV on targets of 12C, 13C, 18O,
26Mg, 58Ni, 60Ni, 90Zr, 118Sn, 120Sn and 208Pb. Using this data, it is shown
the proportionalities between strengths and cross sections for this probe
follow simple trends as a function of mass number. These trends can be used to
confidently determine Gamow-Teller strength distributions in nuclei for which
the proportionality cannot be calibrated via beta-decay strengths. Although
theoretical calculations in distorted-wave Born approximation overestimate the
data, they allow one to understand the main experimental features and to
predict deviations from the simple trends observed in some of the transitions.Comment: 4 pages, 2 figure
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