5,097 research outputs found
Automated Mobile System for Accurate Outdoor Tree Crop Enumeration Using an Uncalibrated Camera.
This paper demonstrates an automated computer vision system for outdoor tree crop enumeration in a seedling nursery. The complete system incorporates both hardware components (including an embedded microcontroller, an odometry encoder, and an uncalibrated digital color camera) and software algorithms (including microcontroller algorithms and the proposed algorithm for tree crop enumeration) required to obtain robust performance in a natural outdoor environment. The enumeration system uses a three-step image analysis process based upon: (1) an orthographic plant projection method integrating a perspective transform with automatic parameter estimation; (2) a plant counting method based on projection histograms; and (3) a double-counting avoidance method based on a homography transform. Experimental results demonstrate the ability to count large numbers of plants automatically with no human effort. Results show that, for tree seedlings having a height up to 40 cm and a within-row tree spacing of approximately 10 cm, the algorithms successfully estimated the number of plants with an average accuracy of 95.2% for trees within a single image and 98% for counting of the whole plant population in a large sequence of images
Fully automated segmentation and tracking of the intima media thickness in ultrasound video sequences of the common carotid artery
AbstractâThe robust identification and measurement of the intima media thickness (IMT) has a high clinical relevance because it represents one of the most precise predictors used in the assessment of potential future cardiovascular events. To facilitate the analysis of arterial wall thickening in serial clinical investigations, in this paper we have developed a novel fully automatic algorithm for the segmentation, measurement, and tracking of the intima media complex (IMC) in B-mode ultrasound video sequences. The proposed algorithm entails a two-stage image analysis process that initially addresses the segmentation of the IMC in the first frame of the ultrasound video sequence using a model-based approach; in the second step, a novel customized tracking procedure is applied to robustly detect the IMC in the subsequent frames. For the video tracking procedure, we introduce a spatially coherent algorithm called adaptive normalized correlation that prevents the tracking process from converging to wrong arterial interfaces. This represents the main contribution of this paper and was developed to deal with inconsistencies in the appearance of the IMC over the cardiac cycle. The quantitative evaluation has been carried out on 40 ultrasound video sequences of the common carotid artery (CCA) by comparing the results returned by the developed algorithm with respect to ground truth data that has been manually annotated by clinical experts. The measured IMTmean ± standard deviation recorded by the proposed algorithm is 0.60 mm ± 0.10, with a mean coefficient of variation (CV) of 2.05%, whereas the corresponding result obtained for the manually annotated ground truth data is 0.60 mm ± 0.11 with a mean CV equal to 5.60%. The numerical results reported in this paper indicate that the proposed algorithm is able to correctly segment and track the IMC in ultrasound CCA video sequences, and we were encouraged by the stability of our technique when applied to data captured under different imaging conditions. Future clinical studies will focus on the evaluation of patients that are affected by advanced cardiovascular conditions such as focal thickening and arterial plaques
Regular Tunnelling Sequences in Mixed Systems
We show that the pattern of tunnelling rates can display a vivid and regular
pattern when the classical dynamics is of mixed chaotic/regular type. We
consider the situation in which the dominant tunnelling route connects to a
stable periodic orbit and this orbit is surrounded by a regular island which
supports a number of quantum states. We derive an explicit semiclassical
expression for the positions and tunnelling rates of these states by use of a
complexified trace formula.Comment: submitted to Physica E as a contribution to the workshop proceedings
of "Dynamics of Complex Systems" held at the Max Planck Institute for the
Physics of Complex Systems in Dresden from March 30 to June 15, 199
Global Properties of Neutral Hydrogen in Compact Groups
Compact groups of galaxies provide a unique environment to study the
evolution of galaxies amid frequent gravitational encounters. These nearby
groups have conditions similar to those in the earlier universe when galaxies
were assembled and give us the opportunity to witness hierarchical formation in
progress. To understand how the compact group environment affects galaxy
evolution, we examine the gas and dust in these groups. We present new
single-dish GBT neutral hydrogen (HI) observations of 30 compact groups and
define a new way to quantify the group HI content as the HI-to-stellar mass
ratio of the group as a whole. We compare the HI content with mid-IR indicators
of star formation and optical [g-r] color to search for correlations between
group gas content and star formation activity of individual group members.
Quiescent galaxies tend to live in HI-poor groups, and galaxies with active
star formation are more commonly found in HI-rich groups. Intriguingly, we also
find "rogue" galaxies whose star formation does not correlate with group HI
content. In particular, we identify three galaxies (NGC 2968 in RSCG 34, KUG
1131+202A in RSCG 42, and NGC 4613 in RSCG 64) whose mid-IR activity is
discrepant with the HI. We speculate that this mismatch between mid-IR activity
and HI content is a consequence of strong interactions in this environment that
can strip HI from galaxies and abruptly affect star-formation. Ultimately,
characterizing how and on what timescales the gas is processed in compact
groups will help us understand the interstellar medium in complex, dense
environments similar to the earlier Universe.Comment: Accepted to A
Quasistationary binary inspiral. I. Einstein equations for the two Killing vector spacetime
The geometry of two infinitely long lines of mass moving in a fixed circular
orbit is considered as a toy model for the inspiral of a binary system of
compact objects due to gravitational radiation. The two Killing fields in the
toy model are used, according to a formalism introduced by Geroch, to describe
the geometry entirely in terms of a set of tensor fields on the two-manifold of
Killing vector orbits. Geroch's derivation of the Einstein equations in this
formalism is streamlined and generalized. The explicit Einstein equations for
the toy model spacetime are derived in terms of the degrees of freedom which
remain after a particular choice of gauge.Comment: 37 pages, REVTeX, one PostScript Figure included with epsfig; minor
formatting changes and copyright notice added for journal publicatio
Exome sequencing identifies nonsegregating nonsense ATM and PALB2 variants in familial pancreatic cancer.
We sequenced 11 germline exomes from five families with familial pancreatic cancer (FPC). One proband had a germline nonsense variant in ATM with somatic loss of the variant allele. Another proband had a nonsense variant in PALB2 with somatic loss of the variant allele. Both variants were absent in a relative with FPC. These findings question the causal mechanisms of ATM and PALB2 in these families and highlight challenges in identifying the causes of familial cancer syndromes using exome sequencing
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