8,542 research outputs found
Model atmospheres for type Ia supernovae: Basic steps towards realistic synthetic spectra
Type Ia supernovae are an important tool for studying the expansion history
of the universe. Advancing our yet incomplete understanding of the explosion
scenario requires detailed and realistic numerical models in order to interpret
and analyze the growing amount of observational data. Here we present first
results of our new NLTE model calculations for the expanding atmospheres of
type Ia supernovae that employ a detailed and consistent treatment of all
important NLTE effects as well as line blocking and blanketing. The comparison
of the synthetic spectra resulting from these models with observed data shows
that the employed methods represent an important step towards a more realistic
description of the atmospheres of supernovae Ia.Comment: 4 pages, 1 figure, to appear in: Proceedings of the 11th Workshop on
Nuclear Astrophysics, Ringberg Castle, Germany, 200
Betaine, organic acids and inulin do not affect ileal and total tract nutrient digestibility or microbial fermentation in piglets
The study was conducted to investigate the effects of betaine alone or combined with organic acids and inulin on ileal and total tract nutrient digestibilities and intestinal microbial fermentation characteristics in piglets. In total, 24 four-week-old barrows with an average initial body weight of 6.7 kg were used in two consecutive experiments with 12 piglets each. Betaine, organic acids and inulin at a level of 0.2, 0.4 and 0.2%, respectively, or combinations of these supplements were added to the basal diet. The supplementation of betaine, organic acids and inulin or any of their combinations did not affect ileal and total tract nutrient digestibilities. The microbial fermentation products both at the ileal and faecal level were not affected by any of the treatments. In conclusion, combining betaine with organic acids and inulin did not have any associated effects on the variables that were measured
New calculation schemes for proton-deuteron scattering including the Coulomb interaction
The Coulomb interaction between the protons is included in the description of
proton-deuteron scattering using the screening and renormalization approach in
the framework of momentum-space integral equations. Two new calculational
schemes are presented that confirm the reliability of the perturbative approach
for treating the screened Coulomb interaction in high partial waves, used by us
in earlier works.Comment: To be published in Phys. Rev.
Active Semi-Supervised Learning Using Sampling Theory for Graph Signals
We consider the problem of offline, pool-based active semi-supervised
learning on graphs. This problem is important when the labeled data is scarce
and expensive whereas unlabeled data is easily available. The data points are
represented by the vertices of an undirected graph with the similarity between
them captured by the edge weights. Given a target number of nodes to label, the
goal is to choose those nodes that are most informative and then predict the
unknown labels. We propose a novel framework for this problem based on our
recent results on sampling theory for graph signals. A graph signal is a
real-valued function defined on each node of the graph. A notion of frequency
for such signals can be defined using the spectrum of the graph Laplacian
matrix. The sampling theory for graph signals aims to extend the traditional
Nyquist-Shannon sampling theory by allowing us to identify the class of graph
signals that can be reconstructed from their values on a subset of vertices.
This approach allows us to define a criterion for active learning based on
sampling set selection which aims at maximizing the frequency of the signals
that can be reconstructed from their samples on the set. Experiments show the
effectiveness of our method.Comment: 10 pages, 6 figures, To appear in KDD'1
Developing collaborative partnerships with culturally and linguistically diverse families during the IEP process
Family participation in the special education process has been federally mandated for 40 years, and educators recognize that effective collaboration with their studentsâ families leads to improved academic and social outcomes for students. However, while some family-school relationships are positive and collaborative, many are not, particularly for culturally and linguistically diverse (CLD) families. This article provides practice guidelines based in research for teachers who seek to improve their practices when working with CLD families who have children served by special education
Vibrational branching ratios and hyperfine structure of BH and its suitability for laser cooling
The simple structure of the BH molecule makes it an excellent candidate for
direct laser cooling. We measure the branching ratios for the decay of the
state to vibrational levels of the ground state, , and find that they are exceedingly favourable for laser
cooling. We verify that the branching ratio for the spin-forbidden transition
to the intermediate state is inconsequentially small. We
measure the frequency of the lowest rotational transition of the X state, and
the hyperfine structure in the relevant levels of both the X and A states, and
determine the nuclear electric quadrupole and magnetic dipole coupling
constants. Our results show that, with a relatively simple laser cooling
scheme, a Zeeman slower and magneto-optical trap can be used to cool, slow and
trap BH molecules.Comment: 7 pages, 5 figures. Updated analysis of A state hyperfine structure
and other minor revision
A robust floating nanoammeter
A circuit capable of measuring nanoampere currents while floating at voltages
up to at least 25kV is described. The circuit relays its output to ground
potential via an optical fiber. We particularly emphasize the design and
construction techniques which allow robust operation in the presence of high
voltage spikes and discharges.Comment: 5 pages, 2 figure
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