3,212 research outputs found
An Investigation of the Phenomenon of Separation in the Air Flow Around Simple Quadric Cylinders
The tests, conducted at the Guggenheim Aeronautical Laboratory of Stanford University, to investigate the phenomenon of separation in the air flow past geometric shapes are described in this report
The Ethical Debate Of Drone Journalism: Flying Into The Future Of Reporting
Unmanned aerial vehicles ā a.k.a. drones ā have left the realm of science fiction and are making their way into use by businesses, the Department of Homeland Security, law enforcement officials and news organizations in the United States. Their potential as a newsgathering tool is only just now being explored ā but can these machines maneuver around the ethical and legislative obstacles that threaten to block their use? This paper will look at the definition of what constitutes a drone, the legal arguments for and against their use and the status of drone legislation in the United States, the pros and cons of using these machines in news organizations, and the ethical considerations for and against their use in journalism
Inter-species horizontal transfer resulting in core-genome and niche-adaptive variation within Helicobacter pylori
Background
Horizontal gene transfer is central to evolution in most bacterial species. The detection of exchanged regions is often based upon analysis of compositional characteristics and their comparison to the organism as a whole. In this study we describe a new methodology combining aspects of established signature analysis with textual analysis approaches. This approach has been used to analyze the two available genome sequences of H. pylori.
Results
This gene-by-gene analysis reveals a wide range of genes related to both virulence behaviour and the strain differences that have been relatively recently acquired from other sequence backgrounds. These frequently involve single genes or small numbers of genes that are not associated with transposases or bacteriophage genes, nor with inverted repeats typically used as markers for horizontal transfer. In addition, clear examples of horizontal exchange in genes associated with 'core' metabolic functions were identified, supported by differences between the sequenced strains, including: ftsK, xerD and polA. In some cases it was possible to determine which strain represented the 'parent' and 'altered' states for insertion-deletion events. Different signature component lengths showed different sensitivities for the detection of some horizontally transferred genes, which may reflect different amelioration rates of sequence components.
Conclusion
New implementations of signature analysis that can be applied on a gene-by-gene basis for the identification of horizontally acquired sequences are described. These findings highlight the central role of the availability of homologous substrates in evolution mediated by horizontal exchange, and suggest that some components of the supposedly stable 'core genome' may actually be favoured targets for integration of foreign sequences because of their degree of conservation
Bad moon on the rise? Lunar cycles and incidents of crime
Popular cultures in Western societies have long espoused the notion that phases of the moon influence human behavior. In particular, there is a common belief the full moon increases incidents of aberrant, deviant, and criminal behavior. Using police, astronomical, and weather data from a major southwestern American city, this study assessed whether lunar cycles related with rates of reported crime. The findings fail to support popular lore, which has suggested that lunar phase influenced the volume of crime reported to the police. Future research directions examining qualitative rather than quantitative aspects of this problem may yield further inform the understanding of whether lunar cycles appreciably influence demands for policing services
Tensor Rank, Invariants, Inequalities, and Applications
Though algebraic geometry over is often used to describe the
closure of the tensors of a given size and complex rank, this variety includes
tensors of both smaller and larger rank. Here we focus on the tensors of rank over , which has as a dense subset the orbit
of a single tensor under a natural group action. We construct polynomial
invariants under this group action whose non-vanishing distinguishes this orbit
from points only in its closure. Together with an explicit subset of the
defining polynomials of the variety, this gives a semialgebraic description of
the tensors of rank and multilinear rank . The polynomials we
construct coincide with Cayley's hyperdeterminant in the case , and thus
generalize it. Though our construction is direct and explicit, we also recast
our functions in the language of representation theory for additional insights.
We give three applications in different directions: First, we develop basic
topological understanding of how the real tensors of complex rank and
multilinear rank form a collection of path-connected subsets, one of
which contains tensors of real rank . Second, we use the invariants to
develop a semialgebraic description of the set of probability distributions
that can arise from a simple stochastic model with a hidden variable, a model
that is important in phylogenetics and other fields. Third, we construct simple
examples of tensors of rank which lie in the closure of those of rank
.Comment: 31 pages, 1 figur
Outsourced Investment Management: An Overview for Institutional Decision-Makers
Once seen primarily as a solution for small institutions with limited resources, outsourcing of the investment management function is now widespread, with a broad range of long-term investors -- including those with more substantial investable asset pools -- turning to the outsourced chief investment officer model. Properly implemented, outsourcing can help institutions address portfolio complexity and risk management challenges, benefit from more timely decision-making and contend with an increasingly rigorous regulatory environment, while enabling trustees to focus on improving institutional governanc
SATCHMO-JS: a webserver for simultaneous protein multiple sequence alignment and phylogenetic tree construction.
We present the jump-start simultaneous alignment and tree construction using hidden Markov models (SATCHMO-JS) web server for simultaneous estimation of protein multiple sequence alignments (MSAs) and phylogenetic trees. The server takes as input a set of sequences in FASTA format, and outputs a phylogenetic tree and MSA; these can be viewed online or downloaded from the website. SATCHMO-JS is an extension of the SATCHMO algorithm, and employs a divide-and-conquer strategy to jump-start SATCHMO at a higher point in the phylogenetic tree, reducing the computational complexity of the progressive all-versus-all HMM-HMM scoring and alignment. Results on a benchmark dataset of 983 structurally aligned pairs from the PREFAB benchmark dataset show that SATCHMO-JS provides a statistically significant improvement in alignment accuracy over MUSCLE, Multiple Alignment using Fast Fourier Transform (MAFFT), ClustalW and the original SATCHMO algorithm. The SATCHMO-JS webserver is available at http://phylogenomics.berkeley.edu/satchmo-js. The datasets used in these experiments are available for download at http://phylogenomics.berkeley.edu/satchmo-js/supplementary/
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