15,536 research outputs found
A simple remark on a flat projective morphism with a Calabi-Yau fiber
If a K3 surface is a fiber of a flat projective morphisms over a connected
noetherian scheme over the complex number field, then any smooth connected
fiber is also a K3 surface. Observing this, Professor Nam-Hoon Lee asked if the
same is true for higher dimensional Calabi-Yau fibers. We shall give an
explicit negative answer to his question as well as a proof of his initial
observation.Comment: 8 pages, main theorem is generalized, one more remark is added,
mis-calculation and typos are corrected etc
Randomised controlled trial of primary school based intervention to reduce risk factors for obesity
OBJECTIVE: To assess if a school based intervention was
effective in reducing risk factors for obesity.
DESIGN: Group randomised controlled trial.
SETTING: 10 primary schools in Leeds.
PARTICIPANTS: 634 children aged 7Â-11 years.
INTERVENTION: Teacher training, modification of school
meals, and the development of school action plans
targeting the curriculum, physical education, tuck
shops, and playground activities.
MAIN OUTCOME MEASURES: Body mass index, diet,
physical activity, and psychological state.
RESULTS: Vegetable consumption by 24 hour recall was
higher in children in the intervention group than the
control group (weighted mean difference 0.3
portions/day, 95% confidence interval 0.2 to 0.4),
representing a difference equivalent to 50% of
baseline consumption. Fruit consumption was lower
in obese children in the intervention group ( - 1.0,
- 1.8 to - 0.2) than those in the control group. The
three day diary showed higher consumption of high
sugar foods (0.8, 0.1 to 1.6)) among overweight
children in the intervention group than the control
group. Sedentary behaviour was higher in overweight
children in the intervention group (0.3, 0.0 to 0.7).
Global self worth was higher in obese children in the
intervention group (0.3, 0.3 to 0.6). There was no
difference in body mass index, other psychological
measures, or dieting behaviour between the groups.
Focus groups indicated higher levels of self reported
behaviour change, understanding, and knowledge
among children who had received the intervention.
CONCLUSION: Although it was successful in producing
changes at school level, the programme had little
effect on children's behaviour other than a modest
increase in consumption of vegetables
Evaluation of implementation and effect of primary school based intervention to reduce risk factors for obesity
OBJECTIVES: To implement a school based health
promotion programme aimed at reducing risk factors
for obesity and to evaluate the implementation
process and its effect on the school.
DESIGN: Data from 10 schools participating in a group
randomised controlled crossover trial were pooled
and analysed.
SETTING: 10 primary schools in Leeds.
Participants 634 children (350 boys and 284 girls)
aged 7Â11 years.
MAIN OUTCOME MEASURES: Response rates to
questionnaires, teachers' evaluation of training and
input, success of school action plans, content of
school meals, and children's knowledge of healthy
living and self reported behaviour.
RESULTS: All 10 schools participated throughout the
study. 76 (89%) of the action points determined by
schools in their school action plans were achieved,
along with positive changes in school meals. A high
level of support for nutrition education and
promotion of physical activity was expressed by both
teachers and parents. 410 (64%) parents responded to
the questionnaire concerning changes they would like
to see implemented in school. 19 out of 20 teachers
attended the training, and all reported satisfaction
with the training, resources, and support. Intervention
children showed a higher score for knowledge,
attitudes, and self reported behaviour for healthy
eating and physical activity.
CONCLUSION: This programme was successfully
implemented and produced changes at school level
that tackled risk factors for obesity
HAMEV and SQRED: Fortran 77 Subroutines for Computing the Eigenvalues of Hamiltonian Matrices Using Van Loanss Square Reduced Method
This paper describes LAPACK-based Fortran 77 subroutines for the reduction of a Hamiltonian matrix to square-reduced form and the approximation of all its eigenvalues using the implicit version of Van Loan's method. The transformation of the Hamilto- nian matrix to a square-reduced Hamiltonian uses only orthogonal symplectic similarity transformations. The eigenvalues can then be determined by applying the Hessenberg QR iteration to a matrix of half the order of the Hamiltonian matrix and taking the square roots of the computed values. Using scaling strategies similar to those suggested for algebraic Riccati equations can in some cases improve the accuracy of the computed eigenvalues. We demonstrate the performance of the subroutines for several examples and show how they can be used to solve some control-theoretic problems
Raman signatures of classical and quantum phases in coupled dots: A theoretical prediction
We study electron molecules in realistic vertically coupled quantum dots in a
strong magnetic field. Computing the energy spectrum, pair correlation
functions, and dynamical form factor as a function of inter-dot coupling via
diagonalization of the many-body Hamiltonian, we identify structural
transitions between different phases, some of which do not have a classical
counterpart. The calculated Raman cross section shows how such phases can be
experimentally singled out.Comment: 9 pages, 2 postscript figures, 1 colour postscript figure, Latex 2e,
Europhysics Letters style and epsfig macros. Submitted to Europhysics Letter
The Voluntary Adjustment of Railroad Obligations
Automatic memory management techniques eliminate many programming errors that are both hard to find and to correct. However, these techniques are not yet used in embedded systems with hard realtime applications. The reason is that current methods for automatic memory management have a number of drawbacks. The two major ones are: (1) not being able to always guarantee short real-time deadlines and (2) using large amounts of extra memory. Memory is usually a scarce resource in embedded applications. In this paper we present a new technique, Real-Time Reference Counting (RTRC) that overcomes the current problems and makes automatic memory management attractive also for hard real-time applications. The main contribution of RTRC is that often all memory can be used to store live objects. This should be compared to a memory overhead of about 500% for garbage collectors based on copying techniques and about 50% for garbage collectors based on mark-and-sweep techniques
VPLanet: The Virtual Planet Simulator
We describe a software package called VPLanet that simulates fundamental
aspects of planetary system evolution over Gyr timescales, with a focus on
investigating habitable worlds. In this initial release, eleven physics modules
are included that model internal, atmospheric, rotational, orbital, stellar,
and galactic processes. Many of these modules can be coupled simultaneously to
simulate the evolution of terrestrial planets, gaseous planets, and stars. The
code is validated by reproducing a selection of observations and past results.
VPLanet is written in C and designed so that the user can choose the physics
modules to apply to an individual object at runtime without recompiling, i.e.,
a single executable can simulate the diverse phenomena that are relevant to a
wide range of planetary and stellar systems. This feature is enabled by
matrices and vectors of function pointers that are dynamically allocated and
populated based on user input. The speed and modularity of VPLanet enables
large parameter sweeps and the versatility to add/remove physical phenomena to
assess their importance. VPLanet is publicly available from a repository that
contains extensive documentation, numerous examples, Python scripts for
plotting and data management, and infrastructure for community input and future
development.Comment: 75 pages, 34 figures, 10 tables, accepted to the Proceedings of the
Astronomical Society of the Pacific. Source code, documentation, and examples
available at https://github.com/VirtualPlanetaryLaboratory/vplane
A Study of the Direct-Fitting Method for Measurement of Galaxy Velocity Dispersions
We have measured the central stellar velocity dispersions of 33 nearby spiral
and elliptical galaxies, using a straightforward template-fitting algorithm
operating in the pixel domain. The spectra, obtained with the Double
Spectrograph at Palomar Observatory, cover both the Ca triplet and the Mg b
region, and we present a comparison of the velocity dispersion measurements
from these two spectral regions. Model fits to the Ca triplet region generally
yield good results with little sensitivity to the choice of template star. In
contrast, the Mg b region is more sensitive to template mismatch and to details
of the fitting procedure such as the order of a polynomial used to match the
continuum shape of the template to the object. As a consequence of the
correlation of the [Mg/Fe] ratio with velocity dispersion, it is difficult to
obtain a satisfactory model fit to the Mg b lines and the surrounding Fe blends
simultaneously, particularly for giant elliptical galaxies with large velocity
dispersions. We demonstrate that if the metallicities of the galaxy and
template star are not well matched, then direct template-fitting results are
improved if the Mg b lines themselves are excluded from the fit and the
velocity dispersion is determined from the surrounding weaker lines.Comment: 14 pages. To appear in A
Quickening the pulse: Fractal tempos in continental arc magmatism
The magmatic history of a continental arc can be characterized as punctuated equilibrium, whereby long periods of low-level activity are interrupted periodically by short bursts of high-volume magmatism (“flare-ups”). Geochronological records, most notably from zircon, reveal episodicity in volcanism, pluton formation, and detrital sedimentation in, and associated with, arc segments and volcano-plutonic suites. Distinct tempos can be recognized at all resolvable spatial and temporal scales and are broadly fractal, with each scale reflecting the timescale of processes occurring at different levels in the arc crust. The tempos of continental arc magmatism thus reflect modulation of the mantle-power input as it is progressively filtered through the continental crust
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