4,155 research outputs found
Math Speak and Students\u27 Justifications Promote Deeper Understanding of Mathematics Concepts
Expected seismicity and the seismic noise environment of Europa
Seismic data will be a vital geophysical constraint on internal structure of
Europa if we land instruments on the surface. Quantifying expected seismic
activity on Europa both in terms of large, recognizable signals and ambient
background noise is important for understanding dynamics of the moon, as well
as interpretation of potential future data. Seismic energy sources will likely
include cracking in the ice shell and turbulent motion in the oceans. We define
a range of models of seismic activity in Europa's ice shell by assuming each
model follows a Gutenberg-Richter relationship with varying parameters. A range
of cumulative seismic moment release between and Nm/yr is
defined by scaling tidal dissipation energy to tectonic events on the Earth's
moon. Random catalogs are generated and used to create synthetic continuous
noise records through numerical wave propagation in thermodynamically
self-consistent models of the interior structure of Europa. Spectral
characteristics of the noise are calculated by determining probabilistic power
spectral densities of the synthetic records. While the range of seismicity
models predicts noise levels that vary by 80 dB, we show that most noise
estimates are below the self-noise floor of high-frequency geophones, but may
be recorded by more sensitive instruments. The largest expected signals exceed
background noise by 50 dB. Noise records may allow for constraints on
interior structure through autocorrelation. Models of seismic noise generated
by pressure variations at the base of the ice shell due to turbulent motions in
the subsurface ocean may also generate observable seismic noise.Comment: 24 pages, 11 figures, Added in supplementary information from
revision submission, including 3 audio files with sonification of Europa
noise records. To view attachments, please download and extract the gzipped
tar source file listed under "Other formats
Stability ordering of cycle expansions
We propose that cycle expansions be ordered with respect to stability rather
than orbit length for many chaotic systems, particularly those exhibiting
crises. This is illustrated with the strong field Lorentz gas, where we obtain
significant improvements over traditional approaches.Comment: Revtex, 5 incorporated figures, total size 200
Utilization of soil organic phosphorus as a strategic approach for sustainable agriculture
Soil organic phosphorus (P
org
) can significantly assist in minimizing the adverse effects of chemi-
cal phosphorus fertilizers on aquatic and marine resources. Success to achieve the desired last-
ing transformation is primarily reliant on the drastic reduction of wasteful applications of chemical
phosphorus fertilizers, thereby paving the way for proper investment of soil P
org
reserves. To this
end, organically-bound phosphorus can be viewed as a cornerstone for the future development
of agriculture. Thus, we consider it very timely to emphasize the suitability of soil P
org
to lead the
way
BioAssay Ontology (BAO): a semantic description of bioassays and high-throughput screening results
<p>Abstract</p> <p>Background</p> <p>High-throughput screening (HTS) is one of the main strategies to identify novel entry points for the development of small molecule chemical probes and drugs and is now commonly accessible to public sector research. Large amounts of data generated in HTS campaigns are submitted to public repositories such as PubChem, which is growing at an exponential rate. The diversity and quantity of available HTS assays and screening results pose enormous challenges to organizing, standardizing, integrating, and analyzing the datasets and thus to maximize the scientific and ultimately the public health impact of the huge investments made to implement public sector HTS capabilities. Novel approaches to organize, standardize and access HTS data are required to address these challenges.</p> <p>Results</p> <p>We developed the first ontology to describe HTS experiments and screening results using expressive description logic. The BioAssay Ontology (BAO) serves as a foundation for the standardization of HTS assays and data and as a semantic knowledge model. In this paper we show important examples of formalizing HTS domain knowledge and we point out the advantages of this approach. The ontology is available online at the NCBO bioportal <url>http://bioportal.bioontology.org/ontologies/44531</url>.</p> <p>Conclusions</p> <p>After a large manual curation effort, we loaded BAO-mapped data triples into a RDF database store and used a reasoner in several case studies to demonstrate the benefits of formalized domain knowledge representation in BAO. The examples illustrate semantic querying capabilities where BAO enables the retrieval of inferred search results that are relevant to a given query, but are not explicitly defined. BAO thus opens new functionality for annotating, querying, and analyzing HTS datasets and the potential for discovering new knowledge by means of inference.</p
Congruences modulo prime powers of Hecke eigenvalues in level
We continue the study of strong, weak, and -weak eigenforms introduced by
Chen, Kiming, and Wiese. We completely determine all systems of Hecke
eigenvalues of level modulo , showing there are finitely many. This
extends results of Hatada and can be considered as evidence for the more
general conjecture formulated by the author together with Kiming and Wiese on
finiteness of systems of Hecke eigenvalues modulo prime powers at any fixed
level. We also discuss the finiteness of systems of Hecke eigenvalues of level
modulo , reducing the question to the finiteness of a single eigenvalue.
Furthermore, we answer the question of comparing weak and -weak eigenforms
and provide the first known examples of non-weak -weak eigenforms.Comment: 28 pages; Minor revisio
Strange hyperon and antihyperon production from quark and string-rope matter
Hyperon and antihyperon production is investigated using two microscopical
models: {\bf (1)} the fast hadronization of quark matter as given by the ALCOR
model; {\bf (2)} string formation and fragmentation as in the HIJING/B model.
We calculate the particle numbers and momentum distributions for Pb+Pb
collisions at CERN SPS energies in order to compare the two models with each
other and with the available experimental data. We show that these two
theoretical approaches give similar yields for the hyperons, but strongly
differ for antihyperons.Comment: 11 pages, Latex, 3 EPS figures, contribution to the Proceedings of
the 4th International Conference on Strangeness in Quark Matter (SQM'98),
Padova, Italy, 20-24 July 199
Parametric optimisation of high-velocity oxy-fuel nickel-chromium-silicon-boron and aluminium-oxide coating to improve erosion wear resistance
Nickel (Ni) based alloy coatings are gaining momentum due to its superior mechanical properties contributed by the dispersion of hard carbides and borides, which is substantially influenced by the processing technique. Accordingly, this work investigates High-Velocity Oxy-Fuel (HVOF) thermal spraying of Nickel-Chromium-Silicon-Boron (NiCrSiB) and Aluminium Oxide (Al2O3) at a 60:40 (wt%) ratio on AISI304 stainless steel substrate. The influence of HVOF spray parameters such as oxygen, fuel, and powder feed rate in addition to standoff distance on the erosion resistance was studied. The parametric model identified the rate of powder feed and standoff distance as the two most significant parameters affecting the erosion behaviour. The optimum parametric values for oxygen, fuel and powder feed rate was identified as 260 lpm, 65 lpm and 28 g minâ1 respectively at a standoff distance of 250 mm for the highest wear resistance. The results of this study show that that NiCrSiB-Al2O3 HVOF coating features a ductile erosion behaviour and offers 1.6 times more wear resistance at a 90° impact angle in comparison to 30°.Published onlin
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