218,547 research outputs found
General Defocusing Particle Tracking: fundamentals and uncertainty assessment
General Defocusing Particle Tracking (GDPT) is a single-camera,
three-dimensional particle tracking method that determines the particle depth
positions from the defocusing patterns of the corresponding particle images.
GDPT relies on a reference set of experimental particle images which is used to
predict the depth position of measured particle images of similar shape. While
several implementations of the method are possible, its accuracy is ultimately
limited by some intrinsic properties of the acquired data, such as the
signal-to-noise ratio, the particle concentration, as well as the
characteristics of the defocusing patterns. GDPT has been applied in different
fields by different research groups, however, a deeper description and analysis
of the method fundamentals has hitherto not been available. In this work, we
first identity the fundamental elements that characterize a GDPT measurement.
Afterwards, we present a standardized framework based on synthetic images to
assess the performance of GDPT implementations in terms of measurement
uncertainty and relative number of measured particles. Finally, we provide
guidelines to assess the uncertainty of experimental GDPT measurements, where
true values are not accessible and additional image aberrations can lead to
bias errors. The data were processed using DefocusTracker, an open-source GDPT
software. The datasets were created using the synthetic image generator
MicroSIG and have been shared in a freely-accessible repository
CompiLIG at SemEval-2017 Task 1: Cross-Language Plagiarism Detection Methods for Semantic Textual Similarity
We present our submitted systems for Semantic Textual Similarity (STS) Track
4 at SemEval-2017. Given a pair of Spanish-English sentences, each system must
estimate their semantic similarity by a score between 0 and 5. In our
submission, we use syntax-based, dictionary-based, context-based, and MT-based
methods. We also combine these methods in unsupervised and supervised way. Our
best run ranked 1st on track 4a with a correlation of 83.02% with human
annotations
Strong Clustering of Lyman Break Galaxies around Luminous Quasars at z~4
In the standard picture of structure formation, the first massive galaxies
are expected to form at the highest peaks of the density field, which
constitute the cores of massive proto-clusters. Luminous quasars (QSOs) at z~4
are the most strongly clustered population known, and should thus reside in
massive dark matter halos surrounded by large overdensities of galaxies,
implying a strong QSO-galaxy cross-correlation function. We observed six z~4
QSO fields with VLT/FORS exploiting a novel set of narrow band filters custom
designed to select Lyman Break Galaxies (LBGs) in a thin redshift slice of
Delta_z~0.3, mitigating the projection effects that have limited the
sensitivity of previous searches for galaxies around z>~4 QSOs. We find that
LBGs are strongly clustered around QSOs, and present the first measurement of
the QSO-LBG cross-correlation function at z~4, on scales of 0.1<~R<~9 Mpc/h
(comoving). Assuming a power law form for the cross-correlation function
xi=(r/r0_QG)^gamma, we measure r0_QG=8.83^{+1.39}_{-1.51} Mpc/h for a fixed
slope of gamma=2.0. This result is in agreement with the expected
cross-correlation length deduced from measurements of the QSO and LBG
auto-correlation function, and assuming a linear bias model. We also measure a
strong auto-correlation of LBGs in our QSO fields finding
r0_GG=21.59^{+1.72}_{-1.69} Mpc/h for a fixed slope of gamma=1.5, which is ~4
times larger than the LBG auto-correlation length in random fields, providing
further evidence that QSOs reside in overdensities of LBGs. Our results
qualitatively support a picture where luminous QSOs inhabit exceptionally
massive (M_halo>10^12 M_sun) dark matter halos at z~4.Comment: 25 pages, 22 figures, submitted to the Ap
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The role of HG in the analysis of temporal iteration and interaural correlation
Near Infrared Microspectroscopy, Fluorescence Microspectroscopy, Infrared Chemical Imaging and High-Resolution Nuclear Magnetic Resonance Analysis of Soybean Seeds, Embryos and Single Cells
Chemical analysis of soybean seeds, somatic embryos and single cells were carried out by Fourier Transform Infrared (FT-IR), Fourier Transform Near Infrared (FT-NIR) Microspectroscopy, Fluorescence and High-Resolution NMR (HR-NMR). The first FT-NIR chemical images of biological systems approaching 1 micron (1μ) resolution are presented here. Chemical images obtained by FT-NIR and FT-IR Microspectroscopy are presented for oil in soybean seeds and somatic embryos under physiological conditions. FT-NIR spectra of oil and proteins were obtained for volumes as small as 2μ3. Related, HR-NMR analyses of oil contents in somatic embryos are also presented here with nanoliter precision. Such 400 MHz 1H NMR analyses allowed the selection of mutagenized embryos with higher oil content (e.g. ~20%) compared to non-mutagenized control embryos. Moreover, developmental changes in single soybean seeds and/or somatic embryos may be monitored by FT-NIR with a precision approaching the picogram level. Indeed, detailed chemical analyses of oils and phytochemicals are now becoming possible by FT-NIR Chemical Imaging/ Microspectroscopy of single cells. The cost, speed and analytical requirements of plant breeding and genetic selection programs are fully satisfied by FT-NIR spectroscopy and Microspectroscopy for soybeans and soybean embryos. FT-NIR Microspectroscopy and Chemical Imaging are also shown to be potentially important in functional Genomics and Proteomics research through the rapid and accurate detection of high-content microarrays (HCMA). Multi-photon (MP), pulsed femtosecond laser NIR Fluorescence Excitation techniques were shown to be capable of Single Molecule Detection (SMD). Therefore, such powerful techniques allow for the most sensitive and reliable quantitative analyses to be carried out both in vitro and in vivo. Thus, MP NIR excitation for Fluorescence Correlation Spectroscopy (FCS) allows not only single molecule detection, but also molecular dynamics and high resolution, submicron imaging of femtoliter volumes inside living cells and tissues. These novel, ultra-sensitive and rapid NIR/FCS analyses have numerous applications in important research areas, such as: agricultural biotechnology, food safety, pharmacology, medical research and clinical diagnosis of viral diseases and cancers
Scan matching by cross-correlation and differential evolution
Scan matching is an important task, solved in the context of many high-level problems including pose estimation, indoor localization, simultaneous localization and mapping and others. Methods that are accurate and adaptive and at the same time computationally efficient are required to enable location-based services in autonomous mobile devices. Such devices usually have a wide range of high-resolution sensors but only a limited processing power and constrained energy supply. This work introduces a novel high-level scan matching strategy that uses a combination of two advanced algorithms recently used in this field: cross-correlation and differential evolution. The cross-correlation between two laser range scans is used as an efficient measure of scan alignment and the differential evolution algorithm is used to search for the parameters of a transformation that aligns the scans. The proposed method was experimentally validated and showed good ability to match laser range scans taken shortly after each other and an excellent ability to match laser range scans taken with longer time intervals between them.Web of Science88art. no. 85
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