1,811 research outputs found
The Impact of a Kindergarten Intervention Program on Student Reading Achievement in Primary Grades
One of the biggest issues in education today is that no common structure exists to serve students before they reach their fifth birthday. There exists opportunities for children to receive social, emotional and educational instruction, but there are no requirements to participate. Commonly, parents of children that have the financial means take advantage of pre-Kindergarten opportunities, but not every family has that benefit. Researchers have discovered this to be the most critical time in terms of social, psychological and intellectual development in young children. For some students, waiting until they enter Kindergarten to intervene is too late. The purpose of this quantitative study was to explore the effects of a Kindergarten intervention program on student cohort reading achievement scores for primary grades from Summer 2011 to Spring 2013. Thus, this study compared groups mean scale scores on AIMSweb assessments for students who did participate in the Jump Start program to mean scale scores on the AIMSweb assessments on groups of students that did not participate in the Jump Start program. The study also took into account those students from both groups that did and did not participate in a summer intervention. There were no statistically significant differences of student scores between students that received the Jump Start intervention and those that did not receive the Jump Start intervention. This study suggests that with the needed program for students that are at-risk, the students in these groups were able to perform at similar levels as their peers that did not meet the at-risk criteria. The study suggests further research on the effects of the Jump Start intervention with larger groups of students, which will be possible as the program grows each year. The study also suggests consideration of district policy on the allocation of dollars to expand this Jump Start program
Temperature dependence of exciton recombination in semiconducting single-wall carbon nanotubes
We study the excitonic recombination dynamics in an ensemble of (9,4)
semiconducting single-wall carbon nanotubes by high sensitivity time-resolved
photo-luminescence experiments. Measurements from cryogenic to room temperature
allow us to identify two main contributions to the recombination dynamics. The
initial fast decay is temperature independent and is attributed to the presence
of small residual bundles that create external non-radiative relaxation
channels. The slow component shows a strong temperature dependence and is
dominated by non-radiative processes down to 40 K. We propose a quantitative
phenomenological modeling of the variations of the integrated photoluminescence
intensity over the whole temperature range. We show that the luminescence
properties of carbon nanotubes at room temperature are not affected by the
dark/bright excitonic state coupling
Towards visualisation of central-cell-effects in scanning-tunnelling-microscope images of subsurface dopant qubits in silicon
Atomic-scale understanding of phosphorous donor wave functions underpins the
design and optimisation of silicon based quantum devices. The accuracy of
large-scale theoretical methods to compute donor wave functions is dependent on
descriptions of central-cell-corrections, which are empirically fitted to match
experimental binding energies, or other quantities associated with the global
properties of the wave function. Direct approaches to understanding such
effects in donor wave functions are of great interest. Here, we apply a
comprehensive atomistic theoretical framework to compute scanning tunnelling
microscopy (STM) images of subsurface donor wave functions with two
central-cell-correction formalisms previously employed in the literature. The
comparison between central-cell models based on real-space image features and
the Fourier transform profiles indicate that the central-cell effects are
visible in the simulated STM images up to ten monolayers below the silicon
surface. Our study motivates a future experimental investigation of the
central-cell effects via STM imaging technique with potential of fine tuning
theoretical models, which could play a vital role in the design of donor-based
quantum systems in scalable quantum computer architectures.Comment: Nanoscale 201
The Hodge ring of Kaehler manifolds
We determine the structure of the Hodge ring, a natural object encoding the
Hodge numbers of all compact Kaehler manifolds. As a consequence of this
structure, there are no unexpected relations among the Hodge numbers, and no
essential differences between the Hodge numbers of smooth complex projective
varieties and those of arbitrary Kaehler manifolds. The consideration of
certain natural ideals in the Hodge ring allows us to determine exactly which
linear combinations of Hodge numbers are birationally invariant, and which are
topological invariants. Combining the Hodge and unitary bordism rings, we are
also able to treat linear combinations of Hodge and Chern numbers. In
particular, this leads to a complete solution of a classical problem of
Hirzebruch's.Comment: Dedicated to the memory of F. Hirzebruch. To appear in Compositio
Mat
Remarks on hard Lefschetz conjectures on Chow groups
We propose two conjectures of Hard Lefschetz type on Chow groups and prove
them for some special cases. For abelian varieties, we shall show they are
equivalent to well-known conjectures of Beauville and Murre.Comment: to appear in Sciences in China, Ser. A Mathematic
Optical properties of potential-inserted quantum wells in the near infrared and Terahertz ranges
We propose an engineering of the optical properties of GaAs/AlGaAs quantum
wells using AlAs and InAs monolayer insertions. A quantitative study of the
effects of the monolayer position and the well thickness on the interband and
intersubband transitions, based on the extended-basis sp3d5s* tight-binding
model, is presented. The effect of insertion on the interband transitions is
compared with existing experimental data. As for intersubband transitions, we
show that in a GaAs/AlGaAs quantum well including two AlAs and one InAs
insertions, a three level {e1 , e2 , e3 } system where the transition energy
e3-e2 is lower and the transition energy e2-e1 larger than the longitudinal
optical phonon energy (36 meV) can be engineered together with a e3-e2
transition energy widely tunable through the TeraHertz range
A hybrid metal/semiconductor electron pump for quantum metrology
Electron pumps capable of delivering a current higher than 100pA with
sufficient accuracy are likely to become the direct mise en pratique of the
possible new quantum definition of the ampere. Furthermore, they are essential
for closing the quantum metrological triangle experiment which tests for
possible corrections to the quantum relations linking e and h, the electron
charge and the Planck constant, to voltage, resistance and current. We present
here single-island hybrid metal/semiconductor transistor pumps which combine
the simplicity and efficiency of Coulomb blockade in metals with the
unsurpassed performances of silicon switches. Robust and simple pumping at
650MHz and 0.5K is demonstrated. The pumped current obtained over a voltage
bias range of 1.4mV corresponds to a relative deviation of 5e-4 from the
calculated value, well within the 1.5e-3 uncertainty of the measurement setup.
Multi-charge pumping can be performed. The simple design fully integrated in an
industrial CMOS process makes it an ideal candidate for national measurement
institutes to realize and share a future quantum ampere
Unitary representations of the Galilean line group: Quantum mechanical principle of equivalence
We present a formalism of Galilean quantum mechanics in non-inertial
reference frames and discuss its implications for the equivalence principle.
This extension of quantum mechanics rests on the Galilean line group, the
semidirect product of the real line and the group of analytic functions from
the real line to the Euclidean group in three dimensions. This group provides
transformations between all inertial and non-inertial reference frames and
contains the Galilei group as a subgroup. We construct a certain class of
unitary representations of the Galilean line group and show that these
representations determine the structure of quantum mechanics in non-inertial
reference frames. Our representations of the Galilean line group contain the
usual unitary projective representations of the Galilei group, but have a more
intricate cocycle structure. The transformation formula for the Hamiltonian
under the Galilean line group shows that in a non-inertial reference frame it
acquires a fictitious potential energy term that is proportional to the
inertial mass, suggesting the equivalence of inertial mass and gravitational
mass in quantum mechanics
- …