57,996 research outputs found
Stellar Absorption Lines in the Spectra of Seyfert Galaxies
We have measured the strengths of Ca II Triplet and Mgb stellar absorption
lines in the nuclear and off-nuclear spectra of Seyfert galaxies. These
features are diluted to varying degrees by continuum emission from the active
nucleus and from young stars. Ca II Triplet strengths can be enhanced if
late-type supergiant stars dominate the near-IR light. Thus, objects with
strong Ca II Triplet and weak Mgb lines may be objects with strong bursts of
star formation. We find that for most of our sample the line strengths are at
least consistent with dilution of a normal galaxy spectrum by a power law
continuum, in accord with the standard model for AGN. However, for several
Seyferts in our sample, it appears that dilution by a power law continuum
cannot simultaneously explain strong Ca II Triplet and relatively weak Mgb.
Also, these objects occupy the region of the IRAS color-color diagram
characteristic of starburst galaxies. In these objects it appears that the
optical to near-IR emission is dominated by late-type supergiants produced in a
circumnuclear burst of star formation.Comment: 4 pages, 3 figures, to appear in Advances in Space Research,
presented at "The AGN/Host Galaxy Connection" as part of the Scientific
Assembly of COSPAR, July 12-18 Nagoya, Japa
Current Classification of the Families of Coleoptera
(excerpt)
Several works on the order Coleoptera have appeared in recent years, some of them creating new superfamilies, others modifying the constitution of these or creating new families, finally others are genera1 revisions of the order. The authors believe that the current classification of this order, incorporating these changes would prove useful. The following outline is based mainly on Crowson (1960, 1964, 1966, 1967, 1971, 1972, 1973) and Crowson and Viedma (1964). For characters used on classification see Viedma (1972) and for family synonyms Abdullah (1969). Major features of this conspectus are the rejection of the two sections of Adephaga (Geadephaga and Hydradephaga), based on Bell (1966) and the new sequence of Heteromera, based mainly on Crowson (1966), with adaptations
Notes on Insect Injection, Anesthetization, and Bleeding.
(excerpt)
In recent years there has been a burgeoning interest in insect cytogenetics, sometimes involving in vivo cultures of haematocytes for chromosomal analysis. Mitotic poisons, such as colchicine (Tyrkus, 1971), are commonly injected to produce metaphase plates. Likewise, injection of toxins is now common-place in applied insect research. However, surprisingly little general information on injection is available in the literature. The dictates of morphology determine the gross procedure to be used. The kind of needle and syringe, the amount of fluid to be administered, and the necessity of optical aids are a function of the size of the insect recipient. Once these decisions are made, other considerations must still be weighed, including comparative exoskeletal toughness and the insect\u27s stage of development, which are important in determining possible areas for needle penetration
POLICRYPS-based electrically switchable Bragg reflector
The formation and characterization of a switchable volume reflective element fabricated from a polymer liquid crystal (LC) polymer slice (POLICRYPS) structure by holographic photopolymerization at high temperature (65 °C) using a photosensitive/nematic liquid crystal prepolymer mixture is reported. The submicron Bragg structure formed consists of periodic continuous polymeric walls separated by periodic LC channels. The phase separated NLC self-aligns in a homeotropic alignment between the polymer walls as indicated by polarizing optical microscopy analysis (Maltese cross). The resulting periodic grating structure results in a Bragg reflection notch upon illumination with white light due to the periodic variation in refractive index. Electro-optical experiments realized through in-plane electrodes and temperature experiments confirm that the multilayer structure acts as a Bragg mirror whose reflection efficiency can be controlled by either a small (âŒ3V/ÎŒm) electric field or temperature
CORRECTING FOR SPATIAL EFFECTS IN LIMITED DEPENDENT VARIABLE REGRESSION: ASSESSING THE VALUE OF "AD-HOC" TECHNIQUES
A common test for spatial dependence in regression analysis with continuous dependent variables is the Moran's I. For limited dependent variable models, the standard definition of a residual breaks down because yi is qualitative. Efforts to correct for potential spatial effects in limited dependent variable models have relied on ad-hoc methods such as including a spatial lag variable or using a regular sample that omits neighboring observations. Kelejian and Prucha have recently developed a version of Moran's I for limited dependent variable models. We present the statistic in a more accessible way and use it to test the value of previously-used ad-hoc techniques with a specific data set. Keywords: Morans I, Spatial Autocorrelation, Limited Dependent Variable Models, Land-Use Change, Geographical Information Systems (GIS),Moran's I, Spatial Autocorrelation, Limited Dependent Variable Models, Land-Use Change, Geographical Information Systems (GIS), Research Methods/ Statistical Methods,
On a heuristic point of view concerning the motion of matter. From random metric to Schroedinger equation
The motion of a particle is studied in a random space-time. It is assumed
that the velocity is small enough for the non-relativistic approximation to be
valid. The randomness of the metric induces a diffusion in coordinate space.
Hence it is shown that the evolution of the probability density is given by
Schroedinger equation.Comment: 13 pages, minor changes, publication reference give
Modeling Deforestation and Land Use Change: Sparse Data Environments
Land use change in developing countries is of great interest to policymakers and researchers from many backgrounds. Concerns about consequences of deforestation for global climate change and biodiversity have received the most publicity, but loss of wetlands, declining land productivity, and watershed management are also problems facing developing countries. In developing countries, analysis is especially constrained by lack of data. This paper reviews modeling approaches for data-constrained environments that involve methods such as neural nets and dynamic programming and research results that link individual household survey data with satellite images using geographic positioning systems.Land Economics/Use, Q15, Q23, R14,
Assessing the Robustness of Predictions in Spatially Explicit Models of Land Use
We propose an information-theoretic approach to assess the performance of a discrete choice model used to analyze land use and land use change. We show that our disaggregated measure can be used to compare robustness of predictions across land use categories and across models. Furthermore, a proper reformulation of the problem shows that a disaggregated (observation by observation) log-likelihood lends itself to an information theoretic interpretation, which allows comparisons performance across models.Land Economics/Use,
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