79 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
Coverage and Energy Analysis of Mobile Sensor Nodes in Obstructed Noisy Indoor Environment: A Voronoi Approach
The rapid deployment of wireless sensor network (WSN) poses the challenge of
finding optimal locations for the network nodes, especially so in (i) unknown
and (ii) obstacle-rich environments. This paper addresses this challenge with
BISON (Bio-Inspired Self-Organizing Network), a variant of the Voronoi
algorithm. In line with the scenario challenges, BISON nodes are restricted to
(i) locally sensed as well as (ii) noisy information on the basis of which they
move, avoid obstacles and connect with neighboring nodes. Performance is
measured as (i) the percentage of area covered, (ii) the total distance
traveled by the nodes, (iii) the cumulative energy consumption and (iv) the
uniformity of nodes distribution. Obstacle constellations and noise levels are
studied systematically and a collision-free recovery strategy for failing nodes
is proposed. Results obtained from extensive simulations show the algorithm
outperforming previously reported approaches in both, convergence speed, as
well as deployment cost.Comment: 17 pages, 24 figures, 1 tabl
Electron Spin Dynamics and Hyperfine Interactions in Fe/Al_0.1Ga_0.9As/GaAs Spin Injection Heterostructures
We have studied hyperfine interactions between spin-polarized electrons and
lattice nuclei in Al_0.1Ga_0.9As/GaAs quantum well (QW) heterostructures. The
spin-polarized electrons are electrically injected into the semiconductor
heterostructure from a metallic ferromagnet across a Schottky tunnel barrier.
The spin-polarized electron current dynamically polarizes the nuclei in the QW,
and the polarized nuclei in turn alter the electron spin dynamics. The
steady-state electron spin is detected via the circular polarization of the
emitted electroluminescence. The nuclear polarization and electron spin
dynamics are accurately modeled using the formalism of optical orientation in
GaAs. The nuclear spin polarization in the QW is found to depend strongly on
the electron spin polarization in the QW, but only weakly on the electron
density in the QW. We are able to observe nuclear magnetic resonance (NMR) at
low applied magnetic fields on the order of a few hundred Oe by electrically
modulating the spin injected into the QW. The electrically driven NMR
demonstrates explicitly the existence of a Knight field felt by the nuclei due
to the electron spin.Comment: 19 Figures - submitted to PR
Integral abutment bridges: Investigation of seismic soil-structure interaction effects by shaking table testing
In recent years there has been renewed interest on integral abutment bridges (IABs), mainly due to their low construction and maintenance cost. Owing to the monolithic connection between deck and abutments, there is strong soil-structure interaction between the bridge and the backfill under both thermal action and earthquake shaking. Although some of the regions where IABs are adopted qualify as highly seismic, there is limited knowledge as to their dynamic behaviour and vulnerability under strong ground shaking. To develop a better understanding on the seismic behaviour of IABs, an extensive experimental campaign involving over 75 shaking table tests and 4800 time histories of recorded data, was carried out at EQUALS Laboratory, University of Bristol, under the auspices of EU-sponsored SERA project (Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe). The tests were conducted on a 5 m long shear stack mounted on a 3 m Ă— 3 m 6-DOF earthquake simulator, focusing on interaction effects between a scaled bridge model, abutments, foundation piles and backfill soil. The study aims at (a) developing new scaling procedures for physical modelling of IABs, (b) investigating experimentally the potential benefits of adding compressible inclusions (CIs) between the abutment and the backfill and (c) exploring the influence of different types of connection between the abutment and the pile foundation. Results indicate that the CI reduces the accelerations on the bridge deck and the settlements in the backfill, while disconnecting piles from the cap decreases bending near the pile head
Layered, Tunable Graphene Oxide-Nylon Heterostructures for Wearable Electrocardiogram Sensors
Nanoscale engineered materials combined with wearable wireless technologies
can deliver a new level of health monitoring. A reduced graphene oxide-nylon
composite material is developed and tested, demonstrating its usefulness as a
material for sensors in wearable, long-term electrocardiogram (ECG) monitoring
via a comparison to one of the widely used ECG sensors. The structural analysis
by scanning electron (SEM) and atomic force microscopy (AFM) shows a limited
number of defects on a macroscopic scale. Fourier Transform Infrared (FTIR) and
Raman spectroscopy confirm the presence of rGOx, and the ratio of D- and
G-features as a function of thickness correlates with the resistivity analysis.
The negligible effect of the defects and the tunability of electrical and
optical properties, together with live ECG data, demonstrate its signal
transduction capability.Comment: 7 main text and 4 supporting figures, under revie
Optical Pumping in Ferromagnet-Semiconductor Heterostructures: Magneto-optics and Spin Transport
Epitaxial ferromagnetic metal - semiconductor heterostructures are
investigated using polarization-dependent electroabsorption measurements on
GaAs p-type and n-type Schottky diodes with embedded In1-xGaxAs quantum wells.
We have conducted studies as a function of photon energy, bias voltage,
magnetic field, and excitation geometry. For optical pumping with circularly
polarized light at energies above the band edge of GaAs, photocurrents with
spin polarizations on the order of 1 % flow from the semiconductor to the
ferromagnet under reverse bias. For optical pumping at normal incidence, this
polarization may be enhanced significantly by resonant excitation at the
quantum well ground-state. Measurements in a side-pumping geometry, in which
the ferromagnet can be saturated in very low magnetic fields, show hysteresis
that is also consistent with spin-dependent transport. Magneto-optical effects
that influence these measurements are discussed.Comment: PDF, 4 figures, 1 tabl
Understanding the benefit of metformin use in cancer treatment
Biguanides have been developed for the treatment of hyperglycemia and type 2 diabetes. Recently, metformin, the most widely prescribed biguanide, has emerged as a potential anticancer agent. Epidemiological, preclinical and clinical evidence supports the use of metformin as a cancer therapeutic. The ability of metformin to lower circulating insulin may be particularly important for the treatment of cancers known to be associated with hyperinsulinemia, such as those of the breast and colon. Moreover, metformin may exhibit direct inhibitory effects on cancer cells by inhibiting mammalian target of rapamycin (mTOR) signaling and protein synthesis. The evidence supporting a role for metformin in cancer therapy and its potential molecular mechanisms of action are discussed
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