1,532 research outputs found
Florida Association of Teacher Educators Journal
______________________________________________________________________________ This article discusses the findings and implications of a study of eight sixth-and eight eighthgrade teachers and their 628 students. Each teacher was observed six times for a total of 240 minutes. The study focused on 1) how teachers manage their students' behavior and how those management strategies impact teachers' interactions with their students and 2) how these strategies impacted student time-on-task behavior. Data analyses showed that as teacher management behaviors increased student time-on-task decreased and teacher instructional 2 behaviors decreased. The authors discuss ways teacher educators can help candidates develop important classroom management skills. ___________________________________________________________________________
Pumping two dilute gas Bose-Einstein condensates with Raman light scattering
We propose an optical method for increasing the number of atoms in a pair of
dilute gas Bose-Einstein condensates. The method uses laser-driven Raman
transitions which scatter atoms between the condensate and non-condensate atom
fractions. For a range of condensate phase differences there is destructive
quantum interference of the amplitudes for scattering atoms out of the
condensates. Because the total atom scattering rate into the condensates is
unaffected the condensates grow. This mechanism is analogous to that
responsible for optical lasing without inversion. Growth using macroscopic
quantum interference may find application as a pump for an atom laser.Comment: 4 pages, no figure
First results from the Very Small Array -- IV. Cosmological parameter estimation
We investigate the constraints on basic cosmological parameters set by the
first compact-configuration observations of the Very Small Array (VSA), and
other cosmological data sets, in the standard inflationary LambdaCDM model.
Using a weak prior 40 < H_0 < 90 km/s/Mpc and 0 < tau < 0.5 we find that the
VSA and COBE_DMR data alone produce the constraints Omega_tot =
1.03^{+0.12}_{-0.12}, Omega_bh^2 = 0.029^{+0.009}_{-0.009}, Omega_cdm h^2 =
0.13^{+0.08}_{-0.05} and n_s = 1.04^{+0.11}_{-0.08} at the 68 per cent
confidence level. Adding in the type Ia supernovae constraints, we additionally
find Omega_m = 0.32^{+0.09}_{-0.06} and Omega_Lambda = 0.71^{+0.07}_{-0.07}.
These constraints are consistent with those found by the BOOMERanG, DASI and
MAXIMA experiments. We also find that, by combining all the recent CMB
experiments and assuming the HST key project limits for H_0 (for which the
X-ray plus Sunyaev--Zel'dovich route gives a similar result), we obtain the
tight constraints Omega_m=0.28^{+0.14}_{-0.07} and Omega_Lambda=
0.72^{+0.07}_{-0.13}, which are consistent with, but independent of, those
obtained using the supernovae data.Comment: 10 pages, 6 figures, MNRAS in pres
First results from the Very Small Array -- I. Observational methods
The Very Small Array (VSA) is a synthesis telescope designed to image faint
structures in the cosmic microwave background on degree and sub-degree angular
scales. The VSA has key differences from other CMB interferometers with the
result that different systematic errors are expected. We have tested the
operation of the VSA with a variety of blank-field and calibrator observations
and cross-checked its calibration scale against independent measurements. We
find that systematic effects can be suppressed below the thermal noise level in
long observations; the overall calibration accuracy of the flux density scale
is 3.5 percent and is limited by the external absolute calibration scale.Comment: 9 pages, 10 figures, MNRAS in press (Minor revisions
Cosmological parameter estimation using Very Small Array data out to ℓ= 1500
We estimate cosmological parameters using data obtained by the Very Small Array (VSA) in its extended configuration, in conjunction with a variety of other cosmic microwave background (CMB) data and external priors. Within the flat Λ cold dark matter (ΛCDM) model, we find that the inclusion of high-resolution data from the VSA modifies the limits on the cosmological parameters as compared to those suggested by the Wilkinson Microwave Anisotropy Probe (WMAP) alone, while still remaining compatible with their estimates. We find that Ωbh2= 0.0234+0.0012−0.0014, Ωdmh2= 0.111+0.014−0.016, h= 0.73+0.09−0.05, nS= 0.97+0.06−0.03, 1010AS= 23+7−3 and τ= 0.14+0.14−0.07 for WMAP and VSA when no external prior is included. On extending the model to include a running spectral index of density fluctuations, we find that the inclusion of VSA data leads to a negative running at a level of more than 95 per cent confidence ( nrun=−0.069 ± 0.032 ), something that is not significantly changed by the inclusion of a stringent prior on the Hubble constant. Inclusion of prior information from the 2dF galaxy redshift survey reduces the significance of the result by constraining the value of Ωm. We discuss the veracity of this result in the context of various systematic effects and also a broken spectral index model. We also constrain the fraction of neutrinos and find that fν < 0.087 at 95 per cent confidence, which corresponds to mν < 0.32 eV when all neutrino masses are equal. Finally, we consider the global best fit within a general cosmological model with 12 parameters and find consistency with other analyses available in the literature. The evidence for nrun < 0 is only marginal within this model
Measurement of relative phase diffusion between two Bose-Einstein condensates
We propose a method of measuring diffusion of the relative phase between two
Bose-Einstein condensates occupying different nuclear or spin hyperfine states
coupled by a two-photon transition via an intermediate level. Due to the
macroscopic quantum coherence the condensates can be decoupled from the
electromagnetic fields. The rate of decoherence and the phase collapse may be
determined from the occupation of the intermediate level or the absorption of
radiation.Comment: 4 pages, RevTex, 2 ps figure
CMB observations from the CBI and VSA: A comparison of coincident maps and parameter estimation methods
We present coincident observations of the Cosmic Microwave Background (CMB)
from the Very Small Array (VSA) and Cosmic Background Imager (CBI) telescopes.
The consistency of the full datasets is tested in the map plane and the Fourier
plane, prior to the usual compression of CMB data into flat bandpowers. Of the
three mosaics observed by each group, two are found to be in excellent
agreement. In the third mosaic, there is a 2 sigma discrepancy between the
correlation of the data and the level expected from Monte Carlo simulations.
This is shown to be consistent with increased phase calibration errors on VSA
data during summer observations. We also consider the parameter estimation
method of each group. The key difference is the use of the variance window
function in place of the bandpower window function, an approximation used by
the VSA group. A re-evaluation of the VSA parameter estimates, using bandpower
windows, shows that the two methods yield consistent results.Comment: 10 pages, 6 figures. Final version. Accepted for publication in MNRA
Estimating the bispectrum of the Very Small Array data
We estimate the bispectrum of the Very Small Array data from the compact and
extended configuration observations released in December 2002, and compare our
results to those obtained from Gaussian simulations. There is a slight excess
of large bispectrum values for two individual fields, but this does not appear
when the fields are combined. Given our expected level of residual point
sources, we do not expect these to be the source of the discrepancy. Using the
compact configuration data, we put an upper limit of 5400 on the value of f_NL,
the non-linear coupling parameter, at 95 per cent confidence. We test our
bispectrum estimator using non-Gaussian simulations with a known bispectrum,
and recover the input values.Comment: 17 pages, 16 figures, replaced with version accepted by MNRAS.
Primordial bispectrum recalculated and figure 11 change
Future Seismic Hazards in Southern California - Phase I: Implications of the 1992 Landers Earthquake Sequence
Southern California and its seismologists received a wake-up call on June 28, 1992. The
largest earthquake to strike southern California in 40 years occurred near the town of Landers,
located 30 km north of the San Andreas fault. It had a magnitude of 7.5 (M7.5). Three and one-half
hours later, a M6.5 aftershock struck the Big Bear area 40 km (kilometers) to the west of
Landers. An ad hoc working group was rapidly convened in July, 1992, to evaluate how the
Landers-Big Bear earthquake sequence might affect future large earthquakes along major faults
in southern California. In particular, what are the chances of large earthquakes in the next few
years and how do they compare to previous estimates (such as those of the Working Group on
California Earthquake Probabilities -- WGCEP, 1988)? Such an evaluation was made for central
California after the Lorna Prieta earthquake of 1989 (WGCEP, 1990). The charge to the Landers
ad hoc working group included analyzing the seismicity for the last several years in southern
California and the new paleoseismic, geologic, and geodetic data recently available for southern
California. To inform the public about the potential hazard of plausible earthquakes, the working
group was also asked to map the predicted severity of ground shaking for such earthquakes
compared to that from the Landers earthquake
Branding and a child’s brain: an fMRI study of neural responses to logos
Branding and advertising have a powerful effect on both familiarity and preference for products, yet no neuroimaging studies have examined neural response to logos in children. Food advertising is particularly pervasive and effective in manipulating choices in children. The purpose of this study was to examine how healthy children’s brains respond to common food and other logos. A pilot validation study was first conducted with 32 children to select the most culturally familiar logos, and to match food and non-food logos on valence and intensity. A new sample of 17 healthy weight children were then scanned using functional magnetic resonance imaging. Food logos compared to baseline were associated with increased activation in orbitofrontal cortex and inferior prefrontal cortex. Compared to non-food logos, food logos elicited increased activation in posterior cingulate cortex. Results confirmed that food logos activate some brain regions in children known to be associated with motivation. This marks the first study in children to examine brain responses to culturally familiar logos. Considering the pervasiveness of advertising, research should further investigate how children respond at the neural level to marketing
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