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Audio-guided mindfulness training in schools and its effect on academic attainment: Contributing to theory and practice
We report the results of a randomized trial (N = 337) examining the effectiveness of a daily audio-guided MBI in raising academic achievement in 16 volunteer classrooms across two socio-demographically diverse United States primary schools. The study's findings were that, over the intervention period, improvements in Math scores, Social Studies scores and Grade Point Averages (GPA) were generally higher for students in intervention classrooms. However, confidence intervals were wide and there was pre-existing variability between schools and grades, resulting in few significant differences as a result of the intervention and generally low effect sizes. Through a careful discussion of the study's results, the paper contributes to theory by generating a comprehensive agenda for follow-up research. The study also contributes to practice by reporting on the effectiveness of technology-enabled mindfulness training because participating teachers seemed able to implement the intervention with almost no further training or need for hiring external mindfulness experts
Simulation studies of time-control procedures for the advanced air traffic control system
The problem of mixing aircraft equipped with time-controlled guidance systems and unequipped aircraft in the terminal area has been investigated via a real-time air traffic control simulation. These four-dimensional (4D) guidance systems can predict and control the touchdown time of an aircraft to an accuracy of a few seconds throughout the descent. The objectives of this investigation were to (1) develop scheduling algorithms and operational procedures for various traffic mixes that ranged from 25% to 75% 4D-equipped aircraft; (2) examine the effect of time errors at 120 n. mi. from touchdown on touchdown time scheduling of the various mix conditions; and (3) develop efficient algorithms and procedures to null the initial time errors prior to reaching the final control sector, 30 n. mi. from touchdown. Results indicate substantial reduction in controller workload and an increase in orderliness when more than 25% of the aircraft are equipped with 4D guidance systems; initial random errors of up to + or - 2 min can be handled via a single speed advisory issued in the arrival control sector, thus avoiding disruption of the time schedule
Dual contribution to amplification in the mammalian inner ear
The inner ear achieves a wide dynamic range of responsiveness by mechanically
amplifying weak sounds. The enormous mechanical gain reported for the mammalian
cochlea, which exceeds a factor of 4,000, poses a challenge for theory. Here we
show how such a large gain can result from an interaction between amplification
by low-gain hair bundles and a pressure wave: hair bundles can amplify both
their displacement per locally applied pressure and the pressure wave itself. A
recently proposed ratchet mechanism, in which hair-bundle forces do not feed
back on the pressure wave, delineates the two effects. Our analytical
calculations with a WKB approximation agree with numerical solutions.Comment: 4 pages, 4 figure
On Predicting the Solar Cycle using Mean-Field Models
We discuss the difficulties of predicting the solar cycle using mean-field
models. Here we argue that these difficulties arise owing to the significant
modulation of the solar activity cycle, and that this modulation arises owing
to either stochastic or deterministic processes. We analyse the implications
for predictability in both of these situations by considering two separate
solar dynamo models. The first model represents a stochastically-perturbed flux
transport dynamo. Here even very weak stochastic perturbations can give rise to
significant modulation in the activity cycle. This modulation leads to a loss
of predictability. In the second model, we neglect stochastic effects and
assume that generation of magnetic field in the Sun can be described by a fully
deterministic nonlinear mean-field model -- this is a best case scenario for
prediction. We designate the output from this deterministic model (with
parameters chosen to produce chaotically modulated cycles) as a target
timeseries that subsequent deterministic mean-field models are required to
predict. Long-term prediction is impossible even if a model that is correct in
all details is utilised in the prediction. Furthermore, we show that even
short-term prediction is impossible if there is a small discrepancy in the
input parameters from the fiducial model. This is the case even if the
predicting model has been tuned to reproduce the output of previous cycles.
Given the inherent uncertainties in determining the transport coefficients and
nonlinear responses for mean-field models, we argue that this makes predicting
the solar cycle using the output from such models impossible.Comment: 22 Pages, 5 Figures, Preprint accepted for publication in Ap
In--out intermittency in PDE and ODE models
We find concrete evidence for a recently discovered form of intermittency,
referred to as in--out intermittency, in both PDE and ODE models of mean field
dynamos. This type of intermittency (introduced in Ashwin et al 1999) occurs in
systems with invariant submanifolds and, as opposed to on--off intermittency
which can also occur in skew product systems, it requires an absence of skew
product structure. By this we mean that the dynamics on the attractor
intermittent to the invariant manifold cannot be expressed simply as the
dynamics on the invariant subspace forcing the transverse dynamics; the
transverse dynamics will alter that tangential to the invariant subspace when
one is far enough away from the invariant manifold.
Since general systems with invariant submanifolds are not likely to have skew
product structure, this type of behaviour may be of physical relevance in a
variety of dynamical settings.
The models employed here to demonstrate in--out intermittency are
axisymmetric mean--field dynamo models which are often used to study the
observed large scale magnetic variability in the Sun and solar-type stars. The
occurrence of this type of intermittency in such models may be of interest in
understanding some aspects of such variabilities.Comment: To be published in Chaos, June 2001, also available at
http://www.eurico.web.co
Flux-transport dynamos with Lorentz force feedback on differential rotation and meridional flow: Saturation mechanism and torsional oscillations
In this paper we discuss a dynamic flux-transport dynamo model that includes
the feedback of the induced magnetic field on differential rotation and
meridional flow. We consider two different approaches for the feedback:
meanfield Lorentz force and quenching of transport coefficients such as
turbulent viscosity and heat conductivity. We find that even strong feedback on
the meridional flow does not change the character of the flux-transport dynamo
significantly; however it leads to a significant reduction of differential
rotation. To a large degree independent from the dynamo parameters, the
saturation takes place when the toroidal field at the base of the convection
zone reaches between 1.2 an 1.5 T, the energy converted intomagnetic energy
corresponds to about 0.1 to 0.2% of the solar luminosity. The torsional
oscillations produced through Lorentz force feedback on differential rotation
show a dominant poleward propagating branch with the correct phase relation to
the magnetic cycle. We show that incorporating enhanced surface cooling of the
active region belt (as proposed by Spruit) leads to an equatorward propagating
branch in good agreement with observations.Comment: 15 pages, 12 figures, Accepted for publication in ApJ August 10
issue; corrected typos, corrected referenc
Octave Spanning Frequency Comb on a Chip
Optical frequency combs have revolutionized the field of frequency metrology
within the last decade and have become enabling tools for atomic clocks, gas
sensing and astrophysical spectrometer calibration. The rapidly increasing
number of applications has heightened interest in more compact comb generators.
Optical microresonator based comb generators bear promise in this regard.
Critical to their future use as 'frequency markers', is however the absolute
frequency stabilization of the optical comb spectrum. A powerful technique for
this stabilization is self-referencing, which requires a spectrum that spans a
full octave, i.e. a factor of two in frequency. In the case of mode locked
lasers, overcoming the limited bandwidth has become possible only with the
advent of photonic crystal fibres for supercontinuum generation. Here, we
report for the first time the generation of an octave-spanning frequency comb
directly from a toroidal microresonator on a silicon chip. The comb spectrum
covers the wavelength range from 990 nm to 2170 nm and is retrieved from a
continuous wave laser interacting with the modes of an ultra high Q
microresonator, without relying on external broadening. Full tunability of the
generated frequency comb over a bandwidth exceeding an entire free spectral
range is demonstrated. This allows positioning of a frequency comb mode to any
desired frequency within the comb bandwidth. The ability to derive octave
spanning spectra from microresonator comb generators represents a key step
towards achieving a radio-frequency to optical link on a chip, which could
unify the fields of metrology with micro- and nano-photonics and enable
entirely new devices that bring frequency metrology into a chip scale setting
for compact applications such as space based optical clocks
The Interaction Of Multiple Convection Zones In A-type Stars
A-type stars have a complex internal structure with the possibility of
multiple convection zones. If not sufficiently separated, such zones will
interact through the convectively stable regions that lie between them. It is
therefore of interest to ask whether the typical conditions that exist within
such stars are such that these convections zones can ever be considered as
disjoint.
In this paper we present results from numerical simulations that help in
understanding how increasing the distance between the convectively unstable
regions are likely to interact through the stable region that separates them.
This has profound implications for mixing and transport within these stars.Comment: 9 pages, 15 figures, Preprint accepted for publication in MNRA
Quantum states far from the energy eigenstates of any local Hamiltonian
What quantum states are possible energy eigenstates of a many-body
Hamiltonian? Suppose the Hamiltonian is non-trivial, i.e., not a multiple of
the identity, and L-local, in the sense of containing interaction terms
involving at most L bodies, for some fixed L. We construct quantum states \psi
which are ``far away'' from all the eigenstates E of any non-trivial L-local
Hamiltonian, in the sense that |\psi-E| is greater than some constant lower
bound, independent of the form of the Hamiltonian.Comment: 4 page
Spin entangled two-particle dark state in quantum transport through coupled quantum dots
We present a transport setup of coupled quantum dots that enables the
creation of spatially separated spin-entangled two-electron dark states. We
prove the existence of an entangled transport dark state by investigating the
system Hamiltonian without coupling to the electronic reservoirs. In the
transport regime the entangled dark state which corresponds to a singlet has a
strongly enhanced Fano factor compared to the dark state which corresponds to a
mixture of the triplet states. Furthermore we calculate the concurrence of the
occupying electrons to show the degree of entanglement in the transport regime.Comment: 9 pages and 3 figure
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