2,874 research outputs found
SEGMENT3D: A Web-based Application for Collaborative Segmentation of 3D images used in the Shoot Apical Meristem
The quantitative analysis of 3D confocal microscopy images of the shoot
apical meristem helps understanding the growth process of some plants. Cell
segmentation in these images is crucial for computational plant analysis and
many automated methods have been proposed. However, variations in signal
intensity across the image mitigate the effectiveness of those approaches with
no easy way for user correction. We propose a web-based collaborative 3D image
segmentation application, SEGMENT3D, to leverage automatic segmentation
results. The image is divided into 3D tiles that can be either segmented
interactively from scratch or corrected from a pre-existing segmentation.
Individual segmentation results per tile are then automatically merged via
consensus analysis and then stitched to complete the segmentation for the
entire image stack. SEGMENT3D is a comprehensive application that can be
applied to other 3D imaging modalities and general objects. It also provides an
easy way to create supervised data to advance segmentation using machine
learning models
Quantum Spectra of Triangular Billiards on the Sphere
We study the quantal energy spectrum of triangular billiards on a spherical
surface. Group theory yields analytical results for tiling billiards while the
generic case is treated numerically. We find that the statistical properties of
the spectra do not follow the standard random matrix results and their peculiar
behaviour can be related to the corresponding classical phase space structure.Comment: 18 pages, 5 eps figure
Stellar 3-D kinematics in the Draco dwarf spheroidal galaxy
Aims. We present the first three-dimensional internal motions for individual
stars in the Draco dwarf spheroidal galaxy. Methods. By combining first-epoch
observations and second-epoch Data Release
2 positions, we measured the proper motions of sources in the direction
of Draco. We determined the line-of-sight velocities for a sub-sample of
red giant branch stars using medium resolution spectra acquired with the DEIMOS
spectrograph at the Keck II telescope. Altogether, this resulted in a final
sample of Draco members with high-precision and accurate 3D motions, which
we present as a table in this paper. Results. Based on this high-quality
dataset, we determined the velocity dispersions at a projected distance of
pc from the centre of Draco to be
km/s, km/s and
km/s in the projected radial, tangential, and line-of-sight directions. This
results in a velocity anisotropy at
pc. Tighter constraints may be obtained using the spherical Jeans equations and
assuming constant anisotropy and Navarro-Frenk-White (NFW) mass profiles, also
based on the assumption that the 3D velocity dispersion should be lower than
of the escape velocity of the system. In this case, we constrain
the maximum circular velocity of Draco to be in the range of
km/s. The corresponding mass range is in good agreement with
previous estimates based on line-of-sight velocities only. Conclusions. Our
Jeans modelling supports the case for a cuspy dark matter profile in this
galaxy. Firmer conclusions may be drawn by applying more sophisticated models
to this dataset and with new datasets from upcoming releases.Comment: 12 pages, 15 figures, 3 tables. Accepted for publication by A&
Cell Segmentation in 3D Confocal Images using Supervoxel Merge-Forests with CNN-based Hypothesis Selection
Automated segmentation approaches are crucial to quantitatively analyze
large-scale 3D microscopy images. Particularly in deep tissue regions,
automatic methods still fail to provide error-free segmentations. To improve
the segmentation quality throughout imaged samples, we present a new
supervoxel-based 3D segmentation approach that outperforms current methods and
reduces the manual correction effort. The algorithm consists of gentle
preprocessing and a conservative super-voxel generation method followed by
supervoxel agglomeration based on local signal properties and a postprocessing
step to fix under-segmentation errors using a Convolutional Neural Network. We
validate the functionality of the algorithm on manually labeled 3D confocal
images of the plant Arabidopis thaliana and compare the results to a
state-of-the-art meristem segmentation algorithm.Comment: 5 pages, 3 figures, 1 tabl
IDF relationships for short duration rainfall
The intensity-duration-frequency (IDF) relationships bound rainfall intensity to duration and return period. These relationships are commonly used as an input in design of many hydraulic structures and drainage systems. Empirical IDF are estimated on the basis of recorded maximum annual precipitation of given durations, often ranging from 1 h to 24 h. For shorter durations, extrapolations are applied. In this paper, maximum annual precipitation for durations shorter than 1 h (namely, 30 min and 10 min) are evaluated using a rainfall disaggregation model and then used for the evaluation of the IDF relationship. A comparison of values obtained with the extrapolated values is then performed, and the results are discussed. Keywords: intensity-duration-frequency curves, rainfall disaggregation, entropy. © 2013 AIP Publishing LLC
Optically switched magnetism in photovoltaic perovskite CHNH(Mn:Pb)I
The demand for ever-increasing density of information storage and speed of
manipulation boosts an intense search for new magnetic materials and novel ways
of controlling the magnetic bit. Here, we report the synthesis of a
ferromagnetic photovoltaic CHNH(Mn:Pb)I material in which the
photo-excited electrons rapidly melt the local magnetic order through the
Ruderman-Kittel-Kasuya-Yosida interactions without heating up the spin system.
Our finding offers an alternative, very simple and efficient way of optical
spin control, and opens an avenue for applications in low power, light
controlling magnetic devices
Non \ue8 pi\uf9 quella di una volta. La mafia e le attivit\ue0 estorsive in Sicilia
Il volume presenta i risultati di una ricerca volta alla descrizione dei fenomeni estorsivi e della loro intensit\ue0 in Sicilia, raccontando, sulla base di appositi parametri oggettivi e di valutazioni soggettive degli esponenti del mondo delle associazioni e delle forze dell\u2019ordine, le aree pi\uf9 esposte, quelle meno esposte, quelle dove i fenomeni hanno una rilevanza residuale, in una fase in cui i sodalizi mafiosi sono sempre pi\uf9 pressati dall\u2019azione di contrasto. Per raggiungere questo obiettivo ci si \ue8 avvalsi di strumenti qualitativi e dati quantitativi, approfondendo l\u2019analisi delle trasformazioni delle condotte estorsive durante la crisi, concentrandosi in modo specifico su casi emersi nell\u2019ambito di recenti inchieste giudiziarie. Il libro ricostruisce anche la prospettiva e le difficolt\ue0 di alcuni imprenditori siciliani che, dopo aver pagato il pizzo, hanno scelto di denunciare i propri estorsori e di collaborare con le istituzioni
THE CORINI ACTIVE FAULT IN SOUTHWESTERN VIOTIA REGION, CENTRAL GREECE: SEGMENTATION, STRESS ANALYSIS AND EXTENSIONAL STRAIN PATTERNS
Στην εργασία παρουσιάζονται νέα γεωλογικά δεδομένα για ένα ενεργό ρήγμα της Νοτιοδυτικής Βοιωτίας. Η περιοχή αυτή χαρακτηρίζεται από χαμηλή παραμόρφωση συγκρινόμενη με τις νεοτεκτονικές τάφρους τόσο του Κορινθιακού (προς Δυσμάς) όσο και του Ευβοϊκού (προς ανατολάς). Το κανονικό ρήγμα της Κορύνης αποτελείται από δύο μεγάλα τμήματα και μερικά αρκετά μικρότερα με μέση παράταξη ΑΒΑ-ΔΝΔ (Β58°) και φορά κλίσεως προς ΝΑ. Το ρήγμα έχει συνολικό μήκος 12 km και έχει αναπτυχθεί στο ανθρακικό υπόβαθρο της Υποπελαγονικής. Η αρχιτεκτονική της ρηξιγενούς ζώνης χαρακτηρίζεται από την ύπαρξη ενός τεκτονικού λατυποπαγούς με μέσο πάχος 15 εκατοστών. Στην βάση του καθρέπτη της Κορύνης παρατηρείται λωρίδωση με μικρή έως καθόλου διάβρωση πάχους 20-30 εκατοστών, η οποία αντιπροσωπεύει την τελευταία σεισμική κίνηση του ρήγματος με άνοδο του σταθερού τεμάχους. Αναφορικά με την κινηματική το σημαντικότερο εύρημα έγκειται στο ότι ο ελάχιστος άξονας της κύριας τάσης έχει μέση διεύθυνση Β328°Α, η οποία περίπου ταυτίζεται με αυτή των ενεργών ρηγμάτων της νότιας ακτής της Κορινθιακής τάφρου (χερσόνησος Περαχώρας).The Corini normal fault is an active structure of Quaternary age in Southwestern Viotia. This is a region of low finite strain, located between the Quaternary rifts of the Gulf of Corinth and the Gulf of Evia. The fault is segmented into several segments with an average strike of N58°E and dip direction to the SE. The architecture of the fault zone is characterized by a 15 cm thick gouge rock, observed along the fault plane on the footwall side. At several localities along strike we observed a well-defined basal strip of un-eroded fault plane that represents the width (uplift) of the last co-seismic slip. The width of the strip ranges 20-30 cm. Slip inversion data show a mean orientation ofsigmaS (leastprincipal stress) as Ν328Έ which implies similar kinematics with the active faults of the south coast of the Gulf of Corinth
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