6,782 research outputs found
Non-line-of-sight Node Localization based on Semi-Definite Programming in Wireless Sensor Networks
An unknown-position sensor can be localized if there are three or more
anchors making time-of-arrival (TOA) measurements of a signal from it. However,
the location errors can be very large due to the fact that some of the
measurements are from non-line-of-sight (NLOS) paths. In this paper, we propose
a semi-definite programming (SDP) based node localization algorithm in NLOS
environment for ultra-wideband (UWB) wireless sensor networks. The positions of
sensors can be estimated using the distance estimates from location-aware
anchors as well as other sensors. However, in the absence of LOS paths, e.g.,
in indoor networks, the NLOS range estimates can be significantly biased. As a
result, the NLOS error can remarkably decrease the location accuracy.
And it is not easy to efficiently distinguish LOS from NLOS measurements. In
this paper, an algorithm is proposed that achieves high location accuracy
without the need of identifying NLOS and LOS measurement.Comment: submitted to IEEE ICC'1
Fiber-optic three axis magnetometer prototype development
The goal of this research program was to develop a high sensitivity, fiber optic, interferometric, three-axis magnetometer for interplanetary spacecraft applications. Dynamics Technology, Inc. (DTI) has successfully integrated a low noise, high bandwidth interferometer with high sensitivity metallic glass transducers. Also, DTI has developed sophisticated signal processing electronics and complete data acquisition, filtering, and display software. The sensor was packaged in a compact, low power and weight unit which facilitates deployment. The magnetic field sensor had subgamma sensitivity and a dynamic range of 10(exp 5) gamma in a 10 Hz bandwidth. Furthermore, the vector instrument exhibited the lowest noise level when only one axis was in operation. A system noise level of 1 gamma rms was observed in a 1 Hz bandwidth. However, with the other two channels operating, the noise level increased by about one order of magnitude. Higher system noise was attributed to cross-channel interference among the dither fields
Quantitative insertion-site sequencing (QIseq) for high throughput phenotyping of transposon mutants
Genetic screening using random transposon insertions has been a powerful tool for uncovering biology in prokaryotes, where whole-genome saturating screens have been performed in multiple organisms. In eukaryotes, such screens have proven more problematic, in part because of the lack of a sensitive and robust system for identifying transposon insertion sites. We here describe quantitative insertion-site sequencing, or QIseq, which uses custom library preparation and Illumina sequencing technology and is able to identify insertion sites from both the 5' and 3' ends of the transposon, providing an inbuilt level of validation. The approach was developed using piggyBac mutants in the human malaria parasite Plasmodium falciparum but should be applicable to many other eukaryotic genomes. QIseq proved accurate, confirming known sites in >100 mutants, and sensitive, identifying and monitoring sites over a >10,000-fold dynamic range of sequence counts. Applying QIseq to uncloned parasites shortly after transfections revealed multiple insertions in mixed populations and suggests that >4000 independent mutants could be generated from relatively modest scales of transfection, providing a clear pathway to genome-scale screens in P. falciparum QIseq was also used to monitor the growth of pools of previously cloned mutants and reproducibly differentiated between deleterious and neutral mutations in competitive growth. Among the mutants with fitness defects was a mutant with a piggyBac insertion immediately upstream of the kelch protein K13 gene associated with artemisinin resistance, implying mutants in this gene may have competitive fitness costs. QIseq has the potential to enable the scale-up of piggyBac-mediated genetics across multiple eukaryotic systems
Undecidable properties of self-affine sets and multi-tape automata
We study the decidability of the topological properties of some objects
coming from fractal geometry. We prove that having empty interior is
undecidable for the sets defined by two-dimensional graph-directed iterated
function systems. These results are obtained by studying a particular class of
self-affine sets associated with multi-tape automata. We first establish the
undecidability of some language-theoretical properties of such automata, which
then translate into undecidability results about their associated self-affine
sets.Comment: 10 pages, v2 includes some corrections to match the published versio
Biophysics at the coffee shop: lessons learned working with George Oster
Over the past 50 years, the use of mathematical models, derived from physical
reasoning, to describe molecular and cellular systems has evolved from an art
of the few to a cornerstone of biological inquiry. George Oster stood out as a
pioneer of this paradigm shift from descriptive to quantitative biology not
only through his numerous research accomplishments, but also through the many
students and postdocs he mentored over his long career. Those of us fortunate
enough to have worked with George agree that his sharp intellect, physical
intuition and passion for scientific inquiry not only inspired us as scientists
but also greatly influenced the way we conduct research. We would like to share
a few important lessons we learned from George in honor of his memory and with
the hope that they may inspire future generations of scientists.Comment: 22 pages, 3 figures, accepted in Molecular Biology of the Cel
Epithelial cancer detection by oblique-incidence optical spectroscopy
This paper presents a study on non-invasive detection of two common epithelial cancers (skin and esophagus) based on oblique incidence diffuse reflectance spectroscopy (OIDRS). An OIDRS measurement system, which combines fiber optics and MEMS technologies, was developed. In our pilot studies, a total number of 137 cases have been measured in-vivo for skin cancer detection and a total number of 20 biopsy samples have been measured ex-vivo for esophageal cancer detection. To automatically differentiate the cancerous cases from benign ones, a statistical software classification program was also developed. An overall classification accuracy of 90% and 100% has been achieved for skin and esophageal cancer classification, respectively
Relationship Between BP (\u3ci\u3eBaculovirus penaei\u3c/i\u3e) Energy Reserves in Larval and Postlarval Pacific White Shrimp \u3ci\u3ePenaeus vannamei\u3c/i\u3e
The relationship between energy reserves of the penaeid shrimp Penaeus vannamei and Baculovirus penaei, or BP, were investigated in a series of experiments using mysis stage or early postlarval shrimp. Pre-exposure and post-exposure levels of protein and triacylgycerol (TAG) were determined. The effect of pre-exposure protein and TAG levels on susceptibility to BP infections was also investigated by starving a group of shrimp immediately prior to BP exposure. There was no consistent relationship between either pre-exposure or post-exposure protein levels and the percent of shrimp developing patent BP infections. There was, however, a significant positive correlation between TAG levels immediately prior to viral exposure and prevalence of infection 72 h later. Experimental reduction of TAG reserves prior to BP exposure delayed the development of a patent infection. In some, but not all, experiments there was a significant reduction in TAG levels of infected compared with uninfected shrimp 72 h post-exposure. The effect of patent BP infections on host TAG levels was subordinate to fluctuations in TAG content associated with the ontogeny of the hepatopancreas. Results of this study support histological observations that shrimp lipid levels can be altered by baculovirus infections. Furthermore, high levels of energy reserves in the form of TAG are associated with increased susceptibility to BP infection in larval and postlarval shrimp
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