2,188 research outputs found
Classification and Redshift Estimation in Multi-Color Surveys
We present a photometric method for identifying stars, galaxies and quasars
in multi-color surveys and estimating multi-color redshifts for the
extragalactic objects. We use a library of >65000 color templates for
comparison with observed objects. The method was originally developed for the
Calar Alto Deep Imaging Survey (CADIS), but is now used in a variety of survey
projects. We checked its performance by spectroscopy of CADIS objects, where it
provides high reliability (6 mistakes among 151 objects with R<24), especially
for the quasar selection, and redshifts accurate within sigma_z = 0.03 for
galaxies and sigma_z = 0.1 for quasars. For an optimization of future surveys,
a few model surveys are compared, which use the same amount of telescope time
but different filter sets. In summary, medium-band surveys perform superior to
broad-band surveys although they collect less photons. A full account of this
work is already in print.Comment: 7 pages, 2 figures, proceedings of MPA/ESO/MPE Joint Astronomy
Conference Mining THE SKY held in Garching, Germany, July 31 - Aug 4, 200
Closed-shell interaction in silver and gold chlorides
Hartree-Fock and coupled-cluster calculations have been performed for cubic
AgCl and for AuCl having a cubic or the observed structure with space group
I4_1/amd. Cohesive energies and lattice constants are in excellent agreement
with experiment for AgCl; for AuCl we find good agreement, and the experimental
structure is correctly predicted to be lower in energy than the cubic one.
Electron-correlation effects on lattice constants are very large, of up to 0.8
\AA for cubic AuCl. We especially discuss the strength of the closed-shell
interactions, and for the first time a quantitative analysis of the so-called
"aurophilic" Au(I)-Au(I) interaction is presented in solids.Comment: accepted by J. Chem. Phy
Compact Polyhedra of Cubic Symmetry: Geometrical Analysis and Classification
Compact polyhedra of cubic point symmetry Oh, exhibit surfaces of planar
sections (facets) characterized by normal vector families {abc} with up to 48
members each, compatible with Oh symmetry. We focus first on polyhedra confined
by facets with normal vectors of one family, {100}, {110}, and {111},
separately. This yields generic polyhedra which serve for the definition of
general compact polyhedra as intersections of the three generic species. Their
structural properties, such as shape, size, volume, and surface facets, are
found to be described by only three polyhedral structure parameters A, B, C. In
addition, we examine compact polyhedra exhibiting facets defined by normal
vectors of only one general {abc} family resulting in up to 48 facets. These
polyhedra can be described by four polyhedral structure parameters Q, a, b, c.
Geometrical properties of all polyhedra are discussed in analytical detail and
substantiated by visualization of characteristic examples. Corresponding
relationships can also be used to classify shapes and estimate sizes of real
compact metal nanoparticles observed e.g. in electron microscopy experiments.Comment: 43 pages, 21 figure
Nanoparticles with Cubic Symmetry: Classification of Polyhedral Shapes
The shape of crystalline nanoparticles (NP) can often be described by
polyhedra with flat facet surfaces. Thus, structural studies of polyhedral
bodies can help to describe geometric details of NPs. Here we consider compact
polyhedra of cubic point symmetry Oh.as simple models. Their surfaces are
described by facets with normal vectors along selected directions (a, b, c)
together with their symmetry equivalents forming a direction family {abc}. For
given {abc} this yields generic polyhedra with up to 48 facets where we focus
on polyhedra with facets of {abc} = {100}, {110}, and {111}, suggested for
metal NPs with cubic lattices. The resulting generic polyhedra, cubic,
rhombohedral, and octahedral, can serve for the description of non-generic
polyhedra as intersections of corresponding generic species. Their structural
properties are shown to be fully determined by only three structure parameters,
facet distances R100, R110, and R111 of three types of facets. This provides a
phase diagram to completely classify the corresponding Oh symmetry polyhedra.
Structural properties of all polyhedra, such as shape, size, and facet
geometries, are discussed in analytical and numerical detail with visualization
of characteristic examples. The results may be used for respective nanoparticle
simulations but also as a repository assisting the interpretation of structures
of real compact nanoparticles observed by experiment.Comment: 40/56 pages, 18/9 figures (paper/supplement). arXiv admin note: text
overlap with arXiv:2209.0891
The influence of glutathione S-transferases M1 and M3 on the development of bladder cancer
Problem: Cigarette smoking is the most important risk factor of transitional cell carcinoma of the urinary bladder. The effect of the glutathione S- transferases M1 (GSTM1) and M3 (GSTM3) on the influence of this risk factor was investigated. Methods: A total of 293 bladder cancer patients from Dortmund and Wittenberg as well as 176 surgical patients without any malignancy from Dortmund were genotyped for GSTM1 und GSTM3 according to standard PCR/RFLP methods. Smoking habits were also qualified by a standardized interview. Results: The percentage of GSTM1 negative cases was 63 % in the entire bladder cancer patient group compared to 50 % in the control group. GSTM3*A/*A genotype was 76 % in the entire group of bladder cancer cases and 74 % in controls. Smokers and ex-smokers were overrepresented in the bladder cancer patient group. A significant association between smoking status and GSTM1 or GSTM3 genotype could not be revealed. Conclusion: The elevated percentage of GSTM1 negative bladder cancer cases shows the important effect of this polymorphic enzyme on the development of bladder cancer. In contrast to some other studies, an influence of GSTM1 on the risk due to cigarette smoking could not be observed. --Bladder cancer,glutathione S-transferase M1,glutathione S-transferase M3,smoking
Distribution and Dispersal Potential of the Endemic Tree Loblolly Bay (Gordonia Lasianthus) in the Southeastern United States Coastal Plain and Implications for Conservation in the Context of Forecast Climate Scenarios.
Plant communities in the Southeastern United States Coastal Plain constitute a rich assemblage of species from neighboring floristic provinces and include over 1,000 species endemic to the region. Conservation of these unique landscapes requires a better understanding of potential impacts from human activity and a changing climate. As a model species, the endemic tree Loblolly Bay (Gordonia lasianthus) is representative of Carolina Bays, pocosins, and isolated wetland habitats that accentuate Longleaf Pine ecosystems which dominate the focus area. Seed-dispersal events in Loblolly Bay are limited to periods of relatively low humidity primarily during the months of October to December, and require horizontal winds to release and carry seeds. Using measured seed- fall velocities, field observations, herbarium specimens, and weather data, dispersal models indicate that prevailing wind speed and direction under these conditions serves to restrict the species dispersal potential to points southeast of parent trees, and that calculated population migration rates reach a maximum of 30 meters per decade when trees are 10 years old. Examination of meteorological conditions during extreme weather events such as hurricanes revealed no noticeable exception to these findings. By comparison, Species Distribution Models using a multimodel ensemble of 22 climate forecasts determined that calculated climate velocities and predicted presence velocities drastically outpace dispersal potential at rates over 50 times greater (2 km/decade) and move perpendicular (northeast) to modeled dispersal patterns. Under forecast climate scenarios, calculated residence times on protected lands within the observed range indicate the potential for multiple local extirpation events by the mid-21st century. While climate refugia are unlikely to support static populations, predicted outcomes may be mitigated through proactive measures to augment protected areas or through the assembly of habitat corridors
Apple scab control with grapefruit seed extract: no alternative to chemical fungicides
The growth inhibiting effect of four commercially available grapefruit seed extracts
on the causal organism of apple scab Venturia inaequalis was tested. Germination of
the conidia of Venturia inaequalis was pronouncedly inhibited by all tested extracts.
The commercial products were analyzed by high pressure liquid chromatography and
thin layer chromatography. All samples contained at least one preserving agent.
These substances were identified as either benzethonium chloride, benzalkonium
chloride, methyl parabene or propyl parabene. Freshly prepared extracts from seeds
of grapefruits (Citrus paradisi) did not inhibit the germination of Venturia inaequalis. It
was therefore concluded that the antifungal effect of grapefruit seed extracts is
caused by the added preservatives
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