2,897 research outputs found
Perceptions of placement experiences of Early Childhood Studies students: the fluency of knowledge and skills
This paper discusses how academic support prepares undergraduate students for their workplace experience, involving cohorts of students from two universities in England, who offer an undergraduate level, three-year, Early Childhood Studies (ECS) degree. By adopting an interpretive approach, questionnaires were administered to the students concerned (n = 65), to seek their views and opinions on the placement experience. These were administered prior to them attending their first placement and then again on their return. The study found that students were more prepared than they originally perceived themselves to be when undertaking placement, and that a lack of confidence derived from fearing the unknown. The findings indicated that tutor and peer support were most valued as preparation tools and it is suggested that this support is a major factor in the confidence levels of students. This paper argues that the explicit knowledge gained from studying a degree course, and the tacit knowledge and skills that are gained through placement should be viewed as a combined approach rather than two separate entities which should, in turn, aid in confidence building. This is of significance both nationally and internationally for those who may be considering including a workplace experience within their programme
Statistical mechanics of soft-boson phase transitions
The existence of structure on large (100 Mpc) scales, and limits to anisotropies in the cosmic microwave background radiation (CMBR), have imperiled models of structure formation based solely upon the standard cold dark matter scenario. Novel scenarios, which may be compatible with large scale structure and small CMBR anisotropies, invoke nonlinear fluctuations in the density appearing after recombination, accomplished via the use of late time phase transitions involving ultralow mass scalar bosons. Herein, the statistical mechanics are studied of such phase transitions in several models involving naturally ultralow mass pseudo-Nambu-Goldstone bosons (pNGB's). These models can exhibit several interesting effects at high temperature, which is believed to be the most general possibilities for pNGB's
Detection and Interpretation Of Long-Lived X-Ray Quasi-Periodic Pulsations in the X-Class Solar Flare On 2013 May 14
Quasi-periodic pulsations (QPP) seen in the time derivative of the GOES soft
X-ray light curves are analyzed for the near-limb X3.2 event on 14 May 2013.
The pulsations are apparent for a total of at least two hours from the
impulsive phase to well into the decay phase, with a total of 163 distinct
pulses evident to the naked eye. A wavelet analysis shows that the
characteristic time scale of these pulsations increases systematically from
25 s at 01:10 UT, the time of the GOES peak, to 100 s at 02:00 UT.
A second ridge in the wavelet power spectrum, most likely associated with
flaring emission from a different active region, shows an increase from
40 s at 01:40 UT to 100 s at 03:10 UT. We assume that the QPP that
produced the first ridge result from vertical kink-mode oscillations of the
newly formed loops following magnetic reconnection in the coronal current
sheet. This allows us to estimate the magnetic field strength as a function of
altitude given the density, loop length, and QPP time scale as functions of
time determined from the GOES light curves and RHESSI images. The calculated
magnetic field strength of the newly formed loops ranges from about 500 G
at an altitude of 24 Mm to a low value of 10 G at 60 Mm, in general
agreement with the expected values at these altitudes. Fast sausage mode
oscillations are also discussed and cannot be ruled out as an alternate
mechanism for producing the QPP
Examples of Embedded Defects (in Particle Physics and Condensed Matter)
We present a series of examples designed to clarify the formalism of the
companion paper `Embedded Vortices'. After summarising this formalism in a
prescriptive sense, we run through several examples: firstly, deriving the
embedded defect spectrum for Weinberg-Salam theory, then discussing several
examples designed to illustrate facets of the formalism. We then calculate the
embedded defect spectrum for three physical Grand Unified Theories and conclude
with a discussion of vortices formed in the superfluid He-A phase
transition.Comment: final corrections. latex fil
Deep Photometry of GRB 041006 Afterglow: Hypernova Bump at Redshift z=0.716
We present deep optical photometry of the afterglow of gamma-ray burst (GRB)
041006 and its associated hypernova obtained over 65 days after detection (55
R-band epochs on 10 different nights). Our early data (t<4 days) joined with
published GCN data indicates a steepening decay, approaching F_nu ~t^{-0.6} at
early times (<<1 day) and F_nu ~t^{-1.3} at late times. The break at
t_b=0.16+-0.04 days is the earliest reported jet break among all GRB
afterglows. During our first night, we obtained 39 exposures spanning 2.15
hours from 0.62 to 0.71 days after the burst that reveal a smooth afterglow,
with an rms deviation of 0.024 mag from the local power-law fit, consistent
with photometric errors. After t~4 days, the decay slows considerably, and the
light curve remains approximately flat at R~24 mag for a month before decaying
by another magnitude to reach R~25 mag two months after the burst. This
``bump'' is well-fitted by a k-corrected light curve of SN1998bw, but only if
stretched by a factor of 1.38 in time. In comparison with the other GRB-related
SNe bumps, GRB 041006 stakes out new parameter space for GRB/SNe, with a very
bright and significantly stretched late-time SN light curve. Within a small
sample of fairly well observed GRB/SN bumps, we see a hint of a possible
correlation between their peak luminosity and their ``stretch factor'', broadly
similar to the well-studied Phillips relation for the type Ia supernovae.Comment: ApJ Letters, accepted. Additional material available at
ftp://cfa-ftp.harvard.edu/pub/kstanek/GRB041006
Recommended from our members
The statistical distribution of swash maxima on natural beaches
Cartwright and Longuet-Higgins (1956) describe the statistical distribution of maxima that would result from the linear superposition of random, Gaussian waves. The distribution function depends solely upon the relative width of the power spectrum and root-mean-square value of the process time series. Runup field data from three experiments are presented to determine the extent to which the distribution of swash maxima can be approximated using the Cartwright and Longuet-Higgins probability density function. The model is found to be satisfactory for describing various distribution statistics including the average maxima, the proportion of negative maxima, and the elevation at which one third of the swash maxima are exceeded. However, systematic discrepancies that scale as a function of time series skewness are observed in the statistics describing the upper tail of the distributions. Although we conclude that the linear model is incapable of delineating these apparent nonlinearities in the swash time series, the extent of the deviation can be estimated empirically for the purpose of constraining nonlinear models and nearshore engineering design
Recommended from our members
Wavenumber-frequency structure of infragravity swash motions
Alongshore-separated time series of natural swash motions were obtained over a range of environmental conditions using a video technique. Although the frequency spectra and normalized wavenumber spectra for these motions were particularly bland, wavenumber-frequency spectra of these data showed clear partitions of infragravity band energy levels associated with various wave types. For the frequencies 0.025 < ƒ ≤ 0.05 Hz, 45 ± 13% of the shoreline variance was, on average, associated with high-mode (n ≥ 2) edge waves and/or leaky waves, while approximately half that amount was associated with low-mode edge waves. Gravity wave motions (comprising both edge and leaky modes) were typically dominant in a lower-frequency band (0.001 < ƒ ≤ 0.025 Hz). A substantial portion of the variance in this band (21 ± 10%, with a maximum of 38%), however, was identified as a nondispersive waveform with wavenumbers well outside of the wavenumber-frequency bounds for gravity waves. Surprisingly, this nongravity swash variance showed no significant dependence on mean alongshore current strength or mean alongshore current shear as measured in the surf zone trough separating the shoreline from an offshore bar. In addition, the celerities of these swash zone nondispersive waves were found to differ in magnitude, and in one instance, sign, from celerities of similarly structured waves measured farther offshore in the surf zone. These unexpected observations with respect to low-frequency, nongravity swash energy imply a strong decorrelation between trough and shoreline fluid motions
The Strongly Polarized Afterglow of GRB 020405
We report polarization measurements and photometry for the optical afterglow
of the gamma-ray burst GRB 020405. We measured a highly significant 9.9%
polarization (in V band) 1.3 days after the burst and argue that it is
intrinsic to the GRB. The light curve decay is well fitted by a
power-law; we do not see any evidence for a break between 1.24 and 4.3 days
after the burst. We discuss these measurements in the light of several models
of GRB afterglows.Comment: submitted to ApJ
Response of Drought-Tolerant Hybrids to Environmental Yield Potential
Due to increasing non-irrigated corn acres, decreasing availability of irrigation water in some areas of western Kansas, and increasing water restrictions, producers are looking for more efficient ways to use available water. Drought-tolerant (DT) hybrid technologies are marketed for their ability to produce more stable yields in stress-prone environments. The objective of this research was to understand how DT and non-DT corn hybrids respond to a wide range of environmental conditions in terms of soil water status change, canopy indicators of stress, dry matter partitioning, and grain yield. Two DT hybrids, and one non-DT hybrid were compared in 2014 and 2015 at five locations in rain-fed, limited-irrigation, or fully irrigated regimes making a total of 18 environments. Grain yield was measured at all 18 environments, and biomass production was estimated at 14 of the environments. Yields of all hybrids were comparable in most environments, but as environment yields increased beyond 200 bu/a, one of the DT hybrids lagged behind the other two hybrids. Although one of the DT hybrids had slightly greater harvest index values than the other two hybrids in environments that resulted in a greater portion of dry matter allocated to grain, the differences were not consistent enough to be conclusive
Enhanced Non-Gaussianity from Excited Initial States
We use the techniques of effective field theory in an expanding universe to
examine the effect of choosing an excited inflationary initial state built over
the Bunch-Davies state on the CMB bi-spectrum. We find that even for Hadamard
states, there are unexpected enhancements in the bi-spectrum for certain
configurations in momentum space due to interactions of modes in the early
stages of inflation. These enhancements can be parametrically larger than the
standard ones and are potentially observable in current and future data. These
initial state effects have a characteristic signature in -space which
distinguishes them from the usual contributions, with the enhancement being
most pronounced for configurations corresponding to flattened triangles for
which two momenta are collinear.Comment: 33 pages, 1 figure. Refs added and minor addition
- …