43,485 research outputs found
Changing habitat associations of a thermally constrained species, the silver-spotted skipper butterfly, in response to climate warming
Moving Mirrors and Thermodynamic Paradoxes
Quantum fields responding to "moving mirrors" have been predicted to give
rise to thermodynamic paradoxes. I show that the assumption in such work that
the mirror can be treated as an external field is invalid: the exotic
energy-transfer effects necessary to the paradoxes are well below the scales at
which the model is credible. For a first-quantized point-particle mirror, it
appears that exotic energy-transfers are lost in the quantum uncertainty in the
mirror's state. An accurate accounting of these energies will require a model
which recognizes the mirror's finite reflectivity, and almost certainly a model
which allows for the excitation of internal mirror modes, that is, a
second-quantized model.Comment: 7 pages, Revtex with Latex2
New Cosmological Structures on Medium Angular Scales Detected with the Tenerife Experiments
We present observations at 10 and 15 GHz taken with the Tenerife experiments
in a band of the sky at Dec.=+35 degrees. These experiments are sensitive to
multipoles in the range l=10-30. The sensitivity per beam is 56 and 20 microK
for the 10 and the 15 GHz data, respectively. After subtraction of the
prediction of known radio-sources, the analysis of the data at 15 GHz at high
Galactic latitude shows the presence of a signal with amplitude Delta Trms ~ 32
microK. In the case of a Harrison-Zeldovich spectrum for the primordial
fluctuations, a likelihood analysis shows that this signal corresponds to a
quadrupole amplitude Q_rms-ps=20.1+7.1-5.4 microK, in agreement with our
previous results at Dec.+=40 degrees and with the results of the COBE DMR.
There is clear evidence for the presence of individual features in the RA range
190 degrees to 250 degrees with a peak to peak amplitude of ~110 microK. A
preliminary comparison between our results and COBE DMR predictions for the
Tenerife experiments clearly indicates the presence of individual features
common to both. The constancy in amplitude over such a large range in frequency
(10-90 GHz) is strongly indicative of an intrinsic cosmological origin for
these structures.Comment: ApJ Letters accepted, 13 pages Latex (uses AASTEX) and 4 encapsulated
postscript figures
NEET Speaks: Influences Shaping Young Peopleās Choices of Education, Training and Employment
The International Centre for Guidance Studies (iCeGS), University of Derby, has produced this report for South Yorkshire Learning and Skills Council in association with Connexions Doncaster. It is based on the findings from a qualitative study designed to focus on the voices of young people in the Doncaster area, who are not in education, employment or training (NEET). The research aimed to explore individualsā perceptions of the significance of community attachments, including issues such as neighbourhood, fraternities, and young peopleās access to learning and work opportunities. This report is complementary to ongoing work carried by Connexions Doncaster as part of their NEET Strategy 2007-2008 framework.
Background
This study is designed to add qualitative depth to, as well as expand on the findings from South Yorkshire Learning and Skills Council and Connexions Doncaster locally funded 14-19 youth support projects. The approach of the project is based on a belief that young people gain benefits from their experience within their social and geographical (neighbourhood) communities, which are often not formally recognised. Some of these benefits may mitigate the NEET experience. They may include:
Skills and knowledge
Enhanced networks
Self-assurance within a peer group
Personal growth
Communication skills.
The point here is that external perceptions may well be incapable of recognising positive aspects or boundaryless benefits such as those listed above, which may in fact be a key to positive outcomes for disengaged young people. Knowledge of these benefits, it is believed, will help policy makers, Connexions staff, colleges and providers to better understand how to provide programmes of engagement for these young people.
Aim
The project was designed to explore the extent to which hard to reach individualsā learning and career development needs are currently being met, focusing in particular on emerging themes based on their experience of family, community, learning and work. The project aims to inform the future development of suitably
NEET Speaks: Influences Shaping Young Peopleās Choices of Education, Training and Employment
The research approach adopted is based on the fundamental belief that young people gain benefits from their experience within their social and geographical communities, i.e. neighbourhoods, which are often not formally recognised. The project explored the extent to which hard-to-reach individualsā learning and career development needs are currently being met. It focused in particular on emerging themes based on young peopleās experiences of family, community, learning and work
The Tenerife Cosmic Microwave Background Maps: Observations and First Analysis
The results of the Tenerife Cosmic Microwave Background (CMB) experiments are
presented. These observations cover 5000 and 6500 square degrees on the sky at
10 and 15 GHz respectively centred around Dec.~ +35 degrees. The experiments
are sensitive to multipoles l=10-30 which corresponds to the Sachs-Wolfe
plateau of the CMB power spectra. The sensitivity of the results are ~31 and
\~12 microK at 10 and 15 GHz respectively in a beam-size region (5 degrees
FWHM). The data at 15 GHz show clear detection of structure at high Galactic
latitude; the results at 10 GHz are compatible with these, but at lower
significance. A likelihood analysis of the 10 and 15 GHz data at high Galactic
latitude, assuming a flat CMB band power spectra gives a signal Delta
T_l=30+10-8 microK (68 % C.L.). Including the possible contaminating effect due
to the diffuse Galactic component, the CMB signal is Delta T_l=30+15-11 microK.
These values are highly stable against the Galactic cut chosen. Assuming a
Harrison-Zeldovich spectrum for the primordial fluctuations, the above values
imply an expected quadrupole Q_RMS-PS=20+10-7 microK which confirms previous
results from these experiments, and which are compatible with the COBE DMR.Comment: 17 pages, 7 figures. Submitted to Ap
Electronic and optical properties of quantum wells embedded in wrinkled nanomembranes
The authors theoretically investigate quantum confinement and transition
energies in quantum wells (QWs) asymmetrically positioned in wrinkled
nanomembranes. Calculations reveal that the wrinkle profile induces both blue-
and redshifts depending on the lateral position of the QW probed. Relevant
radiative transistions include the ground state of the electron (hole) and
excited states of the hole (electron). Energy shifts as well as stretchability
of the structure are studied as a function of wrinkle amplitude and period.
Large tunable bandwidths of up to 70 nm are predicted for highly asymmetric
wrinkled QWs.Comment: 3 pages, 4 figures. The following article has been submitted to
Applied Physics Letters. After it is published, it will be found at
http://apl.aip.or
Near-infrared integral field spectroscopy of Massive Young Stellar Objects
We present medium resolution () -band integral field
spectroscopy of six MYSOs. The targets are selected from the RMS survey, and we
used the NIFS on the Gemini North telescope. The data show various spectral
line features including Br, CO, H, and \mbox{He\,{\sc i}}. The
Br line is detected in emission in all objects with
-- 200 kms. V645 Cyg shows a high-velocity
P-Cygni profile between -800 kms and -300 kms. We performed
three-dimensional spectroastrometry to diagnose the circumstellar environment
in the vicinity of the central stars using the Br line. We measured the
centroids of the velocity components with sub-mas precision. The centroids
allow us to discriminate the blueshifted and redshifted components in a roughly
east--west direction in both IRAS 18151--1208 and S106 in Br. This lies
almost perpendicular to observed larger scale outflows. We conclude, given the
widths of the lines and the orientation of the spectroastrometric signature,
that our results trace a disc wind in both IRAS 18151--1208 and S106. The CO
absorption lines at low transitions are detected in IRAS
18151--1208 and AFGL 2136. We analysed the velocity structure of the neutral
gas discs. In IRAS 18151--1208, the absorption centroids of the blueshifted and
redshifted components are separated in a direction of north-east to south-west,
nearly perpendicular to that of the larger scale jet. The
position-velocity relations of these objects can be reproduced with central
masses of 30 M_{\sun} for IRAS 18151--1208 and 20 M_{\sun} for AFGL 2136.
We also detect CO bandhead emission in IRAS 18151--1208, S106 and
V645 Cyg. The results can be fitted reasonably with a Keplerian rotation model,
with masses of 15, 20 and 20 M_{\sun} respectively.Comment: 17 pages, 10 figures, accepted by MNRA
The origin of the red luminescence in Mg-doped GaN
Optically-detected magnetic resonance (ODMR) and positron annihilation
spectroscopy (PAS) experiments have been employed to study magnesium-doped GaN
layers grown by metal-organic vapor phase epitaxy. As the Mg doping level is
changed, the combined experiments reveal a strong correlation between the
vacancy concentrations and the intensity of the red photoluminescence band at
1.8 eV. The analysis provides strong evidence that the emission is due to
recombination in which electrons both from effective mass donors and from
deeper donors recombine with deep centers, the deep centers being
vacancy-related defects.Comment: 4 pages, 3 figure
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