296 research outputs found
Shapes of Knotted Cyclic Polymers(Knots and soft-matter physics: Topology of polymers and related topics in physics, mathematics and biology)
この論文は国立情報学研究所の電子図書館事業により電子化されました。Momentary configurations of long polymers at thermal equilibrium usually deviate from spherical symmetry and can be better described, on average, by a prolate ellipsoid. The asphericity and nature of asphericity (or prolateness) that describe these momentary ellipsoidal shapes of a polymer are determined by specific expressions involving the three principal moments of inertia calculated for configurations of the polymer. Earlier theoretical studies and numerical simulations have established that as the length of the polymer increases, the average shape for the statistical ensemble of random configurations asymptotically approaches a characteristic universal shape that depends on the solvent quality. It has been established, however, that these universal shapes differ for linear, circular, and branched chains. We investigate here the effect of knotting on the shape of cyclic polymers modeled as random isosegmental polygons. We observe that random polygons forming different knot types reach asymptotic shapes that are distinct from the ensemble average shape. For the same chain length, more complex knots are, on average, more spherical than less complex knots. This paper is a shorter, revised version of the article Ref. [12]. For more details, see Ref. [12]
Line Profiles from Discrete Kinematic Data
We develop a method to extract the shape information of line profiles from
discrete kinematic data. The Gauss-Hermite expansion, which is widely used to
describe the line of sight velocity distributions extracted from absorption
spectra of elliptical galaxies, is not readily applicable to samples of
discrete stellar velocity measurements, accompanied by individual measurement
errors and probabilities of membership. We introduce two parameter families of
probability distributions describing symmetric and asymmetric distortions of
the line profiles from Gaussianity. These are used as the basis of a maximum
likelihood estimator to quantify the shape of the line profiles. Tests show
that the method outperforms a Gauss-Hermite expansion for discrete data, with a
lower limit for the relative gain of approx 2 for sample sizes N approx 800. To
ensure that our methods can give reliable descriptions of the shape, we develop
an efficient test to assess the statistical quality of the obtained fit. As an
application, we turn our attention to the discrete velocity datasets of the
dwarf spheroidals of the Milky Way. In Sculptor, Carina and Sextans the
symmetric deviations are consistent with velocity distributions more peaked
than Gaussian. In Fornax, instead, there is an evolution in the symmetric
deviations of the line profile from a peakier to more flat-topped distribution
on moving outwards. These results suggest a radially biased orbital structure
for the outer parts of Sculptor, Carina and Sextans. On the other hand,
tangential anisotropy is favoured in Fornax. This is all consistent with a
picture in which Fornax may have had a different evolutionary history to
Sculptor, Carina and Sextans.Comment: MNRAS, accepted for publication, minor change
Application of new methods of environment analysis and assessment in landscape audits : case studies of urban areas like Czestochowa, Poland
Following the 2000 European Landscape Convention, a new act strengthening landscape protection
instruments has been in force since 2015. It sets forth legal aspects of landscape shaping (Dziennik Ustaw 2015, poz.
774) and introduces landscape audits at the province level. A landscape audit consists in identification and
characterization of selected landscapes, assessment of their value, selection of so-called priority landscapes and
identification of threats for preservation of their value. An audit complies with GIS standards. Analyses use source
materials, i.e. digital maps of physical-geographical mesoregions, current topographic maps of digital resources of
cartographic databases, latest orthophotomaps and DTMs, maps of potential vegetation, geobotanic regionalization,
historic-cultural regionalization and natural landscape types, documentation of historical and cultural values and
related complementary resources. A special new methodology (Solon et al. 2014), developed for auditing, was tested
in 2015 in an urban area (Myga-Piatek et al. 2015). Landscapes are characterized by determining their analytic
(natural and cultural) and synthetic features, with particular focus on the stage of delimitation and identification of
landscape units in urban areas. Czestochowa was selected as a case study due to its large natural (karst landscapes of
the Czestochowa Upland, numerous forests, nature reserves) and cultural (Saint Mary’s Sanctuary, unique urban
architecture) potential. Czestochowa is also a city of former iron ore and mineral resources exploitation, still active
industry, dynamic urban sprawl within former farming areas, and dynamically growing tourism. Landscape
delimitation and identification distinguished 75 landscape units basing on uniform landscape background (uniform
cover and use of the land). Landscape assessment used a new assessment method for anthropogenic transformation of
landscape – the indicator describing the correlation between the mean shape index (MSI) and the Shannon diversity
index (SHDI) (Pukowiec-Kurda, Sobala 2016). Particular threats and planning suggestions, useful in development of
urban areas, were presented for selected priority landscapes
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Life in the Atacama — Year 2: Geologic reconnaissance through long-range roving and implications on the search for life
The Life in the Atacama-2004 project, which included geological, morphological, and mineralogical mapping through combined satellite, field-based, and microscopic perspectives and long-range roving, led to the localization of potential habitats
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Searching for life with rovers: exploration methods and science results from the 2004 field campaign of the “Life in the Atacama” project and applications to future Mars Missions
LITA develops and field tests a long-range automated rover and a science payload to search for microbial life in the Atacama. The Atacama's evolution provides a unique training ground for designing and testing exploration strategies and life detection methods for the search for life on Mars
A Keck/DEIMOS spectroscopic survey of faint Galactic satellites: searching for the least massive dwarf galaxies
[abridged] We present the results of a spectroscopic survey of the recently
discovered faint Milky Way satellites Boo, UMaI, UMaII and Wil1. Using the
DEIMOS spectrograph on Keck, we have obtained samples that contain from 15 to
85 probable members of these satellites for which we derive radial velocities
precise to a few km/s down to i~21-22. About half of these stars are observed
with a high enough S/N to estimate their metallicity to within \pm0.2 dex. From
this dataset, we show that UMaII is the only object that does not show a clear
radial velocity peak. However, the measured systemic radial velocity
(v_r=115\pm5 km/s) is in good agreement with recent simulations in which this
object is the progenitor of the recently discovered Orphan Stream. The three
other satellites show velocity dispersions that make them highly dark-matter
dominated systems. In particular the Willman 1 object is not a globular cluster
given its metallicity scatter over -2.0<[Fe/H]<-1.0 and is therefore almost
certainly a dwarf galaxy or dwarf galaxy remnant. We measure a radial velocity
dispersion of only 4.3_{-1.3}^{+2.3} km/s around a systemic velocity of
-12.3\pm2.3 km/s which implies a mass-to-light ratio of ~700 and a total mass
of ~5x10^5 Msun for this satellite, making it the least massive satellite
galaxy known to date. Such a low mass could mean that the 10^7 Msun limit that
had until now never been crossed for Milky Way and Andromeda satellite galaxies
may only be an observational limit and that fainter, less massive systems exist
within the Local Group. However, more modeling and an extended search for
potential extra-tidal stars are required to rule out the possibility that these
systems have not been significantly heated by tidal interaction.Comment: 24 pages, 11 figures, MNRAS accepte
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Spectroscopic results from the Life in the Atacama (LITA) project 2004 field season
Analysis of spectroscopy datasets from rover field tests in the Atacama Desert (Chile), focusing on the composition of the surface and identification of potential habitats for life
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