207 research outputs found
PhytoKeys at 100: progress in sustainability, innovation, and speed to enhance publication in plant systematics
The file attached is the Published/publisher’s pdf version of the article.This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.NHM Repositor
A Toolset for Visualization, Interaction, and Rendering in Virtual Environments
Diese Arbeit beschäftigt sich mit einigen der interessantesten Kernpunkten
der Erstellung eines VR-Systems: die Vorbereitung und Vorverarbeitung der
Daten, deren Visualisierung, die Interaktion mit den Daten und deren
Darstellung. Es werden problem-zugeschnittene Algorithmen, sowie allgemeine
Strategien zur Lösung der entstehenden Probleme vorgestellt.
Insbesondere wird ein neuer Algorithmus zur Segmentierung von Bild- und
Volumendaten eingeführt, der vor allem für medizinische Anwendungen relevant
ist. Weiterhin wird detailliert die Visualisierung von Daten erläutert, die
einen Zeitparameter enthalten. Dabei wird eine Reihe von Visualisierungs-
und Interaktionswerkzeugen zur Analyse historischer Daten demonstriert.
Desweiteren wird der Frage nach der Navigation und der Manipulation entfernter
Objekte nachgegangen und eine neue Interaktionsmetapher vorgestellt: die
Durch-Die-Linse-Metapher (through-the-lens). Basierend auf diesem Konzept
werden verschiedene Navigationswerkzeuge präsentiert, die die Eigenschaften
bekannter Techniken instrumentalisieren, jedoch deren Einschränkungen umgehen
und eine leistungsfähige Interaktion ermöglichen.
Schließlich werden zwei Algorithmen vorgestellt, die eine schnelle Darstellung
der zu visualisierenden Daten in einer virtuellen Umgebung ermöglichen. Jeder
dieser Algorithmen nutzt typische Eigenschaften der Repräsentation. Erstens
wird ein bild-basierter Ansatz vorgestellt, der auf Merkmalen des
Durch-Die-Linse-Konzeptes beruht. Zweitens wird auf die Stereo-Ausgabe von
großen Szenen im Allgemeinen eingegangen.This work addresses some of the most pressing issues considering the assembly of a virtual reality system: the data preprocessing and preparation, the data visualization, the interaction with the data, and their display. The work presents problem-tailored algorithms, as well as general strategies for tackling the introduced problems. In particular, a new algorithm for segmenting image and volume data is discussed, addressing foremost medical applications in general. Moreover, a detailed discussion on visualization issues of data containing a time dimension is provided, demonstrating a set of visualization and interaction props for the analysis of historical events in time.
We describe a set of tools for simultaneously visualization of various parameters of interest and for interactive study of historical events.
In addition, the navigation in general is analyzed, as well as the remote object
manipulation in virtual environments, presenting a new interaction metaphor: the
through-the-lens metaphor. Based on this new concept, a set of navigation tools is introduced, which exploit features of existing techniques, attempting to overcome their limitations and to enable more powerful interaction.
Finally, in order to enable fast rendering of the visualized data, two algorithms for accelerating the rendering performance of a virtual reality system are proposed. Each of them exploits particular characteristics of the representation: (1) an image-based rendering approach based on the features of the introduced through-the-lens tools is presented, (2) the stereo rendering of large scenes is addressed in general
CLINICAL AND NEUROIMAGING STUDIES IN PATIENTS WITH ACUTE SPONTANEOUS INTRACEREBRAL HEMORRHAGE.
Objective: To define the prognostic value of clinical and neuroimaging parameters on the 30-th day mortality and clinical outcome after spontaneous intracerebral hemorrhage (sICH).
Materials and methods: we examined 88 patients with sICH admitted to Neurology Clinic, UMHAT Pleven within 48 hours after clinical symptoms onset. Glasgow Coma Scale (GCS) score was used to assess the primary stroke severity; neurological deficit on admission was assessed by National Institute of Health Stroke Scale (NIHSS); clinical outcome at discharge was evaluated by modified Rankin Scale (mRS) and by Glasgow Outcome Scale (GOS) on the 30-th day after sICH onset. Hematoma volume was measured by the formula of Kothari: AxBxC/2 in ml. The statistical analysis was performed by SPSS 19.0 and Statgraphics plus 4.1 for Windows.
Results: Initial assessment of primary stroke severity and neurological deficit by GCS и NIHSS, hematoma localization and volume were found strongly correlated with the clinical outcome on the 30-th day after the sICH onset. Age and vascular risk factors did not correlate with the clinical outcome. Male patients had better survival on the 30-th day compared with the female ones.
Discussion: Neurological deficit on admission, hematoma localization and volume were found reliable predictors of the 30-th day clinical outcome that could serve for early stratification of patients and optimal choice of therapeutic approach
Near-Earth asteroids spectroscopic survey at Isaac Newton Telescope
The population of near-Earth asteroids (NEAs) shows a large variety of
objects in terms of physical and dynamical properties. They are subject to
planetary encounters and to strong solar wind and radiation effects. Their
study is also motivated by practical reasons regarding space exploration and
long-term probability of impact with the Earth. We aim to spectrally
characterize a significant sample of NEAs with sizes in the range of 0.25
- 5.5 km (categorized as large), and search for connections between their
spectral types and the orbital parameters. Optical spectra of NEAs were
obtained using the Isaac Newton Telescope (INT) equipped with the IDS
spectrograph. These observations are analyzed using taxonomic classification
and by comparison with laboratory spectra of meteorites. A total number of 76
NEAs were observed. We classified 44 of them as Q/S-complex, 16 as B/C-complex,
eight as V-types, and another eight belong to the remaining taxonomic classes.
Our sample contains 27 asteroids categorized as potentially hazardous and 31
possible targets for space missions including (459872) 2014 EK24, (436724) 2011
UW158, and (67367) 2000 LY27. The spectral data corresponding to (276049) 2002
CE26 and (385186) 1994 AW1 shows the 0.7 m feature which indicates the
presence of hydrated minerals on their surface. We report that Q-types have the
lowest perihelia (a median value and absolute deviation of AU)
and are systematically larger than the S-type asteroids observed in our sample.
We explain these observational evidences by thermal fatigue fragmentation as
the main process for the rejuvenation of NEA surfaces. In general terms, the
taxonomic distribution of our sample is similar to the previous studies and
matches the broad groups of the inner main belt asteroids. Nevertheless, we
found a wide diversity of spectra compared to the standard taxonomic types.Comment: Accepted in Astronomy & Astrophysics (A&A
Four ultra-short period eclipsing M-dwarf binaries in the WFCAM Transit Survey
We report on the discovery of four ultra-short period (P<0.18 days) eclipsing
M-dwarf binaries in the WFCAM Transit Survey. Their orbital periods are
significantly shorter than of any other known main-sequence binary system, and
are all significantly below the sharp period cut-off at P~0.22 days as seen in
binaries of earlier type stars. The shortest-period binary consists of two M4
type stars in a P=0.112 day orbit. The binaries are discovered as part of an
extensive search for short-period eclipsing systems in over 260,000 stellar
lightcurves, including over 10,000 M-dwarfs down to J=18 mag, yielding 25
binaries with P<0.23 days. In a popular paradigm, the evolution of short period
binaries of cool main-sequence stars is driven by loss of angular momentum
through magnetised winds. In this scheme, the observed P~0.22 day period
cut-off is explained as being due to timescales that are too long for
lower-mass binaries to decay into tighter orbits. Our discovery of low-mass
binaries with significantly shorter orbits implies that either these timescales
have been overestimated for M-dwarfs, e.g. due to a higher effective magnetic
activity, or that the mechanism for forming these tight M-dwarf binaries is
different from that of earlier type main-sequence stars.Comment: 22 pages, 17 figures, 3 tables Accepted for publication in MNRA
280 one-opposition near-Earth asteroids recovered by the EURONEAR with the <i>Isaac Newton</i> Telescope
Context. One-opposition near-Earth asteroids (NEAs) are growing in number, and they must be recovered to prevent loss and mismatch risk, and to improve their orbits, as they are likely to be too faint for detection in shallow surveys at future apparitions.
Aims. We aimed to recover more than half of the one-opposition NEAs recommended for observations by the Minor Planet Center (MPC) using the Isaac Newton Telescope (INT) in soft-override mode and some fractions of available D-nights. During about 130 h in total between 2013 and 2016, we targeted 368 NEAs, among which 56 potentially hazardous asteroids (PHAs), observing 437 INT Wide Field Camera (WFC) fields and recovering 280 NEAs (76% of all targets).
Methods. Engaging a core team of about ten students and amateurs, we used the THELI, Astrometrica, and the Find_Orb software to identify all moving objects using the blink and track-and-stack method for the faintest targets and plotting the positional uncertainty ellipse from NEODyS.
Results. Most targets and recovered objects had apparent magnitudes centered around V ~ 22.8 mag, with some becoming as faint as V ~ 24 mag. One hundred and three objects (representing 28% of all targets) were recovered by EURONEAR alone by Aug. 2017. Orbital arcs were prolonged typically from a few weeks to a few years; our oldest recoveries reach 16 years. The O−C residuals for our 1854 NEA astrometric positions show that most measurements cluster closely around the origin. In addition to the recovered NEAs, 22 000 positions of about 3500 known minor planets and another 10 000 observations of about 1500 unknown objects (mostly main-belt objects) were promptly reported to the MPC by our team. Four new NEAs were discovered serendipitously in the analyzed fields and were promptly secured with the INT and other telescopes, while two more NEAs were lost due to extremely fast motion and lack of rapid follow-up time. They increase the counting to nine NEAs discovered by the EURONEAR in 2014 and 2015.
Conclusions. Targeted projects to recover one-opposition NEAs are efficient in override access, especially using at least two-meter class and preferably larger field telescopes located in good sites, which appear even more efficient than the existing surveys
The first planet detected in the WTS: an inflated hot-Jupiter in a 3.35 d orbit around a late F star [Erratum]
We report the discovery of WTS-1b, the first extrasolar planet found by the
WFCAM Transit Survey, which began observations at the 3.8-m United Kingdom
Infrared Telescope (UKIRT) in August 2007. Light curves comprising almost 1200
epochs with a photometric precision of better than 1 per cent to J ~ 16 were
constructed for ~60000 stars and searched for periodic transit signals. For one
of the most promising transiting candidates, high-resolution spectra taken at
the Hobby-Eberly Telescope (HET) allowed us to estimate the spectroscopic
parameters of the host star, a late-F main sequence dwarf (V=16.13) with
possibly slightly subsolar metallicity, and to measure its radial velocity
variations. The combined analysis of the light curves and spectroscopic data
resulted in an orbital period of the substellar companion of 3.35 days, a
planetary mass of 4.01 +- 0.35 Mj and a planetary radius of 1.49+0.16-0.18 Rj.
WTS-1b has one of the largest radius anomalies among the known hot Jupiters in
the mass range 3-5 Mj. The high irradiation from the host star ranks the planet
in the pM class.Comment: 16 pages, 10 figure
<i>Gaia</i> Data Release 1. Summary of the astrometric, photometric, and survey properties
Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7.
Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion of the limitations due to the preliminary nature of this release.
Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue.
Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the HIPPARCOS and Tycho-2 catalogues – a realisation of the Tycho-Gaia Astrometric Solution (TGAS) – and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of ∼3000 Cepheid and RR-Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr−1 for the proper motions. A systematic component of ∼0.3 mas should be added to the parallax uncertainties. For the subset of ∼94 000 HIPPARCOS stars in the primary data set, the proper motions are much more precise at about 0.06 mas yr−1. For the secondary astrometric data set, the typical uncertainty of the positions is ∼10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to ∼0.03 mag over the magnitude range 5 to 20.7.
Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature five-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless, the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data
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