719 research outputs found
PELICAN: Permutation Equivariant and Lorentz Invariant or Covariant Aggregator Network for Particle Physics
Many current approaches to machine learning in particle physics use generic
architectures that require large numbers of parameters and disregard underlying
physics principles, limiting their applicability as scientific modeling tools.
In this work, we present a machine learning architecture that uses a set of
inputs maximally reduced with respect to the full 6-dimensional Lorentz
symmetry, and is fully permutation-equivariant throughout. We study the
application of this network architecture to the standard task of top quark
tagging and show that the resulting network outperforms all existing
competitors despite much lower model complexity. In addition, we present a
Lorentz-covariant variant of the same network applied to a 4-momentum
regression task
High Energy Electron Confinement in a Magnetic Cusp Configuration
We report experimental results validating the concept that plasma confinement
is enhanced in a magnetic cusp configuration when beta (plasma
pressure/magnetic field pressure) is order of unity. This enhancement is
required for a fusion power reactor based on cusp confinement to be feasible.
The magnetic cusp configuration possesses a critical advantage: the plasma is
stable to large scale perturbations. However, early work indicated that plasma
loss rates in a reactor based on a cusp configuration were too large for net
power production. Grad and others theorized that at high beta a sharp boundary
would form between the plasma and the magnetic field, leading to substantially
smaller loss rates. The current experiment validates this theoretical
conjecture for the first time and represents critical progress toward the
Polywell fusion concept which combines a high beta cusp configuration with an
electrostatic fusion for a compact, economical, power-producing nuclear fusion
reactor.Comment: 12 pages, figures included. 5 movies in Ancillary file
Model Order Reduction for Rotating Electrical Machines
The simulation of electric rotating machines is both computationally
expensive and memory intensive. To overcome these costs, model order reduction
techniques can be applied. The focus of this contribution is especially on
machines that contain non-symmetric components. These are usually introduced
during the mass production process and are modeled by small perturbations in
the geometry (e.g., eccentricity) or the material parameters. While model order
reduction for symmetric machines is clear and does not need special treatment,
the non-symmetric setting adds additional challenges. An adaptive strategy
based on proper orthogonal decomposition is developed to overcome these
difficulties. Equipped with an a posteriori error estimator the obtained
solution is certified. Numerical examples are presented to demonstrate the
effectiveness of the proposed method
Investigations on latent zoonoses in the context of the Swiss Swein 99 - project
Livestock producers in developed countries, such as pig producers, are facing the challenge to produce high quality products which satisfy their customers. Quality assurance programmes therefore are likely to become more important in the near future (Blaha, 1997). A prerequisite to the development of such programmes is the knowledge of animal health data, including zoonoses. In this context, an epidemiological study of the pig health and productivity in Switzerland, called Schwein 99 , has been initiated. This study has the overall objective to study the health and production profile of swine in a broad approach, where pigs are expected to be followed from birth to slaughter. Thus it will be carried out at three levels, i.e. at the breeding units, the fattening units and the abattoirs, respectively. This paper presents preliminary results from a pilot study carried out prior to the larger project to investigate the importance of selected zoonoses, Salmonella, Yersinia enterocolilica and Mycobacterium avium, in slaughtered healthy pigs
What factors influence training opportunities for older workers? Three factorial surveys exploring the attitudes of HR professionals
The core research questions addressed in this paper are: what factors influence HR professionals in deciding whether to approve training proposals for older workers? What kind of training are they more likely to recommend for older employees and in which organizational contexts? We administered three factorial surveys to 66 HR professionals in Italy. Participants made specific training decisions based on profiles of hypothetical older workers. Multilevel analyses indicated that access to training decreases strongly with age, while highly-skilled older employees with low absenteeism rates are more likely to enjoy training opportunities. In addition, older workers displaying positive performance are more likely to receive training than older workers who perform poorly, suggesting that training late in working life may serve as a reward for good performance rather than as a means of enhancing productivity. The older the HR professional evaluating training proposals, the higher the probability that older workers will be recommended for training.
keywords: training; older workers; HR professionals; factorial survey; multilevel model
The He(e, ed)p Reaction in q-constant Kinematics
The cross section for the He(e, ed)p reaction has been measured as a
function of the missing momentum in q -constant kinematics at
beam energies of 370 and 576 MeV for values of the three-momentum transfer
of 412, 504 and 604 \mevc. The L(+TT), T and LT structure functions have been
separated for = 412 and 504 \mevc. The data are compared to three-body
Faddeev calculations, including meson-exchange currents (MEC), and to
calculations based on a covariant diagrammatic expansion. The influence of
final-state interactions and meson-exchange currents is discussed. The
-dependence of the data is reasonably well described by all calculations.
However, the most advanced Faddeev calculations, which employ the AV18
nucleon-nucleon interaction and include MEC, overestimate the measured cross
sections, especially the longitudinal part, and at the larger values of .
The diagrammatic approach gives a fair description of the cross section, but
under(over)estimates the longitudinal (transverse) structure function.Comment: 17 pages, 7 figure
Aberrant chromatin landscape following loss of the H3.3 chaperone Daxx in haematopoietic precursors leads to Pu.1-mediated neutrophilia and inflammation
Defective silencing of retrotransposable elements has been linked to inflammageing, cancer and autoimmune diseases. However, the underlying mechanisms are only partially understood. Here we implicate the histone H3.3 chaperone Daxx, a retrotransposable element repressor inactivated in myeloid leukaemia and other neoplasms, in protection from inflammatory disease. Loss of Daxx alters the chromatin landscape, H3.3 distribution and histone marks of haematopoietic progenitors, leading to engagement of a Pu.1-dependent transcriptional programme for myelopoiesis at the expense of B-cell differentiation. This causes neutrophilia and inflammation, predisposing mice to develop an autoinflammatory skin disease. While these molecular and phenotypic perturbations are in part reverted in animals lacking both Pu.1 and Daxx, haematopoietic progenitors in these mice show unique chromatin and transcriptome alterations, suggesting an interaction between these two pathways. Overall, our findings implicate retrotransposable element silencing in haematopoiesis and suggest a cross-talk between the H3.3 loading machinery and the pioneer transcription factor Pu.1
Display of probability densities for data from a continuous distribution
Based on cumulative distribution functions, Fourier series expansion and
Kolmogorov tests, we present a simple method to display probability densities
for data drawn from a continuous distribution. It is often more efficient than
using histograms.Comment: 5 pages, 4 figures, presented at Computer Simulation Studies XXIV,
Athens, GA, 201
- …